NZ727600B2 - Bispecific t cell activating antigen binding molecules - Google Patents

Abstract

The present invention generally relates to bispecific antigen binding molecules for T cell activation and re-direction to specific target cells. These bispecific antigen binding molecules comprise: (a) a first Fab molecule which specifically binds to a first antigen; (b) a second Fab molecule which specifically binds to a second antigen, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; (c) a third Fab molecule which binds specifically to the first antigen; and (d) an Fc domain composed of a first and second subunit capable of stable association; wherein the first antigen is a target cell antigen and the second antigen is a activating T cell antigen; and wherein the third Fab molecule under c) is identical to the first Fab molecule under a); wherein the CL and CH1 domains of the first and third Fab molecules are modified as defined; and wherein the CH3 domain of the first subunit of the Fc domain comprises a protuberance and the CH3 domain of the second subunit of the Fc domain comprises a cavity ("knob in hole" structure). In addition, the present invention relates to polynucleotides encoding such bispecific antigen binding molecules, and vectors and host cells comprising such polynucleotides. The invention further relates to methods for producing the bispecific antigen binding molecules of the invention, and to methods of using these bispecific antigen binding molecules in the treatment of disease, such as cancer. ich specifically binds to a second antigen, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; (c) a third Fab molecule which binds specifically to the first antigen; and (d) an Fc domain composed of a first and second subunit capable of stable association; wherein the first antigen is a target cell antigen and the second antigen is a activating T cell antigen; and wherein the third Fab molecule under c) is identical to the first Fab molecule under a); wherein the CL and CH1 domains of the first and third Fab molecules are modified as defined; and wherein the CH3 domain of the first subunit of the Fc domain comprises a protuberance and the CH3 domain of the second subunit of the Fc domain comprises a cavity ("knob in hole" structure). In addition, the present invention relates to polynucleotides encoding such bispecific antigen binding molecules, and vectors and host cells comprising such polynucleotides. The invention further relates to methods for producing the bispecific antigen binding molecules of the invention, and to methods of using these bispecific antigen binding molecules in the treatment of disease, such as cancer.

Description

Bispecific T cell activating n binding molecules Field of the Invention The present invention generally relates to bispecific antigen binding molecules for activating T cells. In on, the t invention relates to polynucleotides encoding such bispecific antigen g molecules, and s and host cells comprising such polynucleotides. The invention further relates to methods for producing the bispecific antigen binding molecules of the invention. Methods of using these bispecific antigen binding molecules in the treatment of disease are also described.

Background The selective destruction of an individual cell or a specific cell type is often desirable in a variety of clinical settings. For example, it is a primary goal of cancer therapy to specifically destroy tumor cells, while leaving y cells and tissues intact and undamaged.

An attractive way of achieving this is by inducing an immune response against the tumor, to make immune effector cells such as natural killer (NK) cells or cytotoxic T lymphocytes (CTLs) attack and destroy tumor cells. CTLs constitute the most potent or cells of the immune system, however they cannot be activated by the or mechanism mediated by the Fc domain of conventional therapeutic dies.

In this regard, bispecific antibodies designed to bind with one “arm” to a surface antigen on target cells, and with the second “arm” to an activating, invariant component of the T cell receptor (TCR) complex, have become of st in recent years. The simultaneous binding of such an antibody to both of its targets will force a temporary interaction between target cell and T cell, causing activation of any cytotoxic T cell and subsequent lysis of the target cell. Hence, the immune se is re-directed to the target cells and is independent of peptide antigen presentation by the target cell or the specificity of the T cell as would be relevant for normal MHC-restricted activation of CTLs. In this context it is l that CTLs are only activated when a target cell is presenting the bispecific antibody to them, i.e. the immunological synapse is ed. Particularly desirable are bispecific antibodies that do not require lymphocyte preconditioning or co-stimulation in order to elicit efficient lysis of target cells.

Several bispecific antibody formats have been developed and their suitability for T cell mediated immunotherapy investigated. Out of these, the so-called BiTE (bispecific T cell engager) les have been very well characterized and already shown some promise in the clinic (reviewed in Nagorsen and Bäuerle, Exp Cell Res 317, 1255-1260 (2011)). BiTEs are tandem scFv molecules wherein two scFv molecules are fused by a le linker. Further bispecific formats being ted for T cell engagement e diabodies (Holliger et al., Prot Eng 9, 299-305 (1996)) and derivatives thereof, such as tandem ies (Kipriyanov et al., J Mol Biol 293, 41-66 (1999)). A more recent development are the so-called DART (dual affinity retargeting) molecules, which are based on the diabody format but feature a C-terminal disulfide bridge for additional stabilization (Moore et al., Blood 117, 4542-51 ). The so-called triomabs, which are whole hybrid mouse/rat IgG molecules and also currently being evaluated in clinical trials, represent a larger sized format (reviewed in Seimetz et al., Cancer Treat Rev 36, 458-467 (2010)).

The variety of formats that are being developed shows the great potential attributed to T cell re- direction and activation in immunotherapy. The task of ting bispecific antibodies le therefor is, however, by no means trivial, but involves a number of challenges that have to be met d to efficacy, toxicity, applicability and produceability of the antibodies.

Small constructs such as, for example, BiTE molecules – while being able to efficiently crosslink effector and target cells – have a very short serum half life requiring them to be administered to patients by continuous infusion. IgG-like formats on the other hand – while having the great benefit of a long half life – suffer from toxicity associated with the native effector ons inherent to IgG molecules. Their immunogenic potential constitutes another unfavorable e of IgG-like bispecific antibodies, especially non-human formats, for successful therapeutic development. y, a major challenge in the general development of bispecific antibodies has been the tion of bispecific antibody constructs at a clinically sufficient quantity and purity, due to the mispairing of antibody heavy and light chains of ent icities upon co-expression, which decreases the yield of the correctly assembled construct and results in a number of non-functional side products from which the desired bispecific antibody may be difficult to separate.

Different approaches have been taken to overcome the chain association issue in bispecific antibodies (see e.g. Klein et al., mAbs 6, 653-663 ). For example, the -into-holes’ strategy aims at forcing the pairing of two different antibody heavy chains by introducing mutations into the CH3 domains to modify the contact interface. On one chain bulky amino acids are replaced by amino acids with short side chains to create a ‘hole’. sely, amino acids with large side chains are introduced into the other CH3 domain, to create a ‘knob’. By coexpressing these two heavy chains (and two identical light chains, which have to be appropriate for both heavy chains), high yields of heterodimer (‘knob-hole’) versus homodimer (‘hole-hole’ or ‘knob-knob’) are observed (Ridgway, J.B., et al., Protein Eng. 9 (1996) 617-621; and WO 96/027011). The percentage of heterodimer could be further increased by remodeling the interaction surfaces of the two CH3 domains using a phage y approach and the introduction of a disulfide bridge to stabilize the heterodimers (Merchant, A.M., et al., Nature Biotech. 16 (1998) 677-681; Atwell, S., et al., J. Mol. Biol. 270 (1997) 26–35). New ches for the knobs-into-holes technology are described in e.g. in EP 1870459 A1.

The ‘knobs-into-holes’ strategy does, however, not solve the problem of heavy chain-light chain mispairing, which occurs in bispecific antibodies comprising different light chains for g to the different target antigens.

A strategy to prevent heavy chain-light chain mispairing is to exchange domains between the heavy and light chains of one of the binding arms of a bispecific antibody (see , , , and Schaefer, W. et al, PNAS, 108 (2011) 11187-11191, which relate to bispecific IgG antibodies with a domain crossover).

Exchanging the heavy and light chain variable domains VH and VL in one of the binding arms of the bispecific antibody (WO2009/080252, see also Schaefer, W. et al, PNAS, 108 (2011) 11187-11191) y reduces the side products caused by the mispairing of a light chain against a first antigen with the wrong heavy chain against the second antigen (compared to approaches without such domain exchange). Nevertheless, these antibody preparations are not tely free of side products. The main side product is based on a Bence Jones-type interaction (Schaefer, W. et al, PNAS, 108 (2011) 11187-11191; in Fig. S1I of the Supplement). A further ion of such side products is thus desirable to improve e.g. the yield of such bispecific antibodies.

Given the ulties and disadvantages associated with currently available bispecific dies for T cell ed immunotherapy, there remains a need for novel, improved formats of such molecules. An object of the t invention is to provide bispecific n binding molecules ed for T cell activation and re-direction that combine good efficacy and produceability with low toxicity and ble pharmacokinetic properties; and/ or to at least provide the public with a useful choice. y of the Invention In a first aspect, the invention relates to a T cell activating bispecific antigen binding molecule comprising (a) a first Fab molecule which specifically binds to a first antigen; (b) a second Fab molecule which specifically binds to a second antigen, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; (c) a third Fab molecule which ically binds to the first antigen; and (d) an Fc domain composed of a first and second subunit capable of stable association; wherein the first antigen is a target cell antigen, and the second antigen is an activating T cell antigen, wherein the third Fab molecule under c) is identical to the first Fab molecule under a); wherein in the nt domain CL of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at on 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by arginine (R) or lysine (K) (numbering according to Kabat), and wherein in the nt domain CH1 of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 147 is substituted by glutamic acid (E) ring according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index); and n the Fc domain is an IgG Fc domain, and wherein in the CH3 domain of the first subunit of the Fc domain an amino acid residue is replaced with an amino acid residue having a larger side chain volume, thereby generating a protuberance within the CH3 domain of the first t which is positionable in a cavity within the CH3 domain of the second subunit, and in the CH3 domain of the second subunit of the Fc domain an amino acid residue is replaced with an amino acid residue having a smaller side chain , thereby generating a cavity within the CH3 domain of the second subunit within which the protuberance within the CH3 domain of the first subunit is positionable; and wherein i) the first Fab molecule under a) is fused at the C-terminus of the Fab heavy chain to the N- terminus of the Fab heavy chain of the second Fab molecule under b), and the second Fab molecule under b) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d); or ii) the second Fab molecule under b) is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule under a), and the first Fab molecule under a) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the ts of the Fc domain under d).

In a second aspect, the invention relates to one or more isolated polynucleotide(s) encoding the T cell ting bispecific antigen binding molecule according to the first aspect.

In a third aspect, the ion relates to one or more vector(s), comprising the polynucleotide(s) according to the second aspect.

In a fourth aspect, the invention relates to a host cell in culture comprising the polynucleotide(s) according to the second aspect or the vector(s) ing to the third aspect.

In a fifth aspect, the invention relates to a method of producing a T cell activating bispecific antigen binding molecule according to the first aspect and capable of specific binding to CD3 and a target cell antigen, comprising the steps of a) culturing the host cell according to the fourth aspect under conditions suitable for the expression of the T cell activating bispecific antigen binding molecule and b) recovering the T cell activating bispecific antigen binding molecule.

In a sixth aspect, the invention s to the T cell activating bispecific antigen binding molecule according to the first aspect for use as a medicament.

In a seventh aspect, the invention relates to pharmaceutical composition comprising the T cell ting bispecific antigen binding molecule ing to the first aspect and a pharmaceutically acceptable r.

In an eighth , the invention relates to the T cell ting bispecific antigen binding molecule according to the first aspect for the treatment of a disease in an individual in need thereof.

In a ninth aspect, the invention relates to use of the T cell activating bispecific antigen binding molecule according to the first aspect for the manufacture of a medicament for the treatment of a disease in an individual in need thereof.

Brief ption of the Invention According to the ption, the ratio of a desired bispecific antibody compared to undesired side products, in particular Bence Jones-type side products occurring in ific antibodies with a VH/VL domain exchange in one of their binding arms, can be improved by the introduction of charged amino acids with opposite charges at specific amino acid positions in the CH1 and CL domains.

Thus, in a first embodiment the present description includes a T cell activating bispecific antigen binding molecule comprising (a) a first Fab molecule which specifically binds to a first antigen; (b) a second Fab molecule which specifically binds to a second antigen, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; n the first n is an activating T cell antigen and the second antigen is a target cell antigen, or the first antigen is a target cell antigen and the second antigen is an activating T cell antigen; and wherein i) in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) ring according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) ring according to Kabat EU index); or ii) in the constant domain CL of the second Fab molecule under b) the amino acid at position 124 is tuted ndently by lysine (K), arginine (R) or histidine (H) (numbering ing to Kabat), and wherein in the constant domain CH1 of the second Fab molecule under b) the amino acid at position 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) ring ing to Kabat EU index).

According to the description, the second Fab molecule is a crossover Fab molecule wherein the variable regions of the Fab light chain and the Fab heavy chain are exchanged. In particular embodiments, the first (and the third, if any) Fab le is a conventional Fab molecule. In a further particular embodiment, not more than one Fab molecule capable of specific g to an ting T cell antigen is present in the T cell activating ific antigen g molecule (i.e. the T cell activating bispecific n binding molecule provides lent binding to the activating T cell antigen).

In a particular embodiment, the first antigen is a target cell antigen and the second antigen is an activating T cell antigen. In a more specific embodiment, the activating T cell antigen is CD3, particularly CD3 epsilon. In one embodiment, the target cell antigen is CD20.

In one embodiment of the T cell activating bispecific antigen g molecule according to the description, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), ne (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In a further embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat), and in the nt domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by ic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In yet another embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at on 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment ndently by lysine (K) or arginine (R)) and the amino acid at position 123 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted ndently by glutamic acid (E), or aspartic acid (D) ring according to Kabat EU index).

In a particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by lysine (K) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted by ic acid (E) ring according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index).

In r particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is tuted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by arginine (R) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index).

In one embodiment, the T cell activating ific antigen binding molecule of the description comprises (a) a first Fab molecule which specifically binds to a first antigen; (b) a second Fab molecule which specifically binds to a second antigen, and wherein the variable s VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; wherein the first antigen is a target cell antigen and the second antigen is an activating T cell antigen; and wherein in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted ndently by lysine (K), ne (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or ne (R)) and the amino acid at position 123 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index) and the amino acid at position 213 is tuted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).In an alternative embodiment of the T cell activating bispecific antigen binding molecule according to the ption, in the constant domain CL of the second Fab molecule under b) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one red embodiment independently by lysine (K) or arginine (R)), and in the nt domain CH1 of the second Fab molecule under b) the amino acid at position 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or ic acid (D) (numbering according to Kabat EU index).

In a further ment, in the constant domain CL of the second Fab molecule under b) the amino acid at position 124 is tuted independently by lysine (K), arginine (R) or histidine (H) ring according to Kabat), and in the constant domain CH1 of the second Fab molecule under b) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In still another embodiment, in the nt domain CL of the second Fab molecule under b) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)) and the amino acid at position 123 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the second Fab molecule under b) the amino acid at on 147 is tuted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In one embodiment, in the constant domain CL of the second Fab molecule under b) the amino acid at position 124 is tuted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is tuted by lysine (K) (numbering according to Kabat), and in the constant domain CH1 of the second Fab molecule under b) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU .

In another embodiment, in the constant domain CL of the second Fab molecule under b) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at on 123 is substituted by arginine (R) (numbering according to , and in the constant domain CH1 of the second Fab molecule under b) the amino acid at position 147 is substituted by ic acid (E) (numbering according to Kabat EU index) and the amino acid at on 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index).

In some embodiments, the T cell activating bispecific n binding molecule according to the description further comprises a third Fab molecule which specifically binds to the first antigen.

In particular embodiments, the third Fab molecule is identical to the first Fab molecule. In these embodiments, the third Fab molecule thus comprises the same amino acid substitutions as the first Fab molecule. Like the first Fab molecule, the third Fab molecule particularly is a conventional Fab molecule.

If a third Fab molecule is present, in a particular embodiment the first and the third Fab molecule specifically bind to a target cell n, and the second Fab molecule specifically binds to an activating T cell antigen, particularly CD3, more particularly CD3 epsilon.

In some embodiments of the T cell activating bispecific n binding molecule ing to the description the first Fab molecule under a) and the second Fab molecule under b) are fused to each other, optionally via a peptide linker. In a specific embodiment, the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. In an alternative embodiment, the first Fab molecule is fused at the C- terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. In embodiments wherein either (i) the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule or (ii) the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, additionally the Fab light chain of the Fab molecule and the Fab light chain of the second Fab molecule may be fused to each other, optionally via a peptide linker.

In particular embodiments, the T cell activating bispecific antigen binding molecule according to the description additionally comprises an Fc domain composed of a first and a second subunit capable of stable association.

The T cell activating ific antigen binding le according to the description can have different urations, i.e. the first, second (and optionally third) Fab le may be fused to each other and to the Fc domain in different ways. The components may be fused to each other directly or, preferably, via one or more suitable e linkers. Where fusion is to the N- terminus of a subunit of the Fc domain, it is typically via an immunoglobulin hinge region.

In one embodiment, the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first or the second subunit of the Fc . In such embodiment, the first Fab molecule may be fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule or to the N-terminus of the other one of the subunits of the Fc domain.

In one embodiment, the first and the second Fab molecule are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain. In this embodiment, the T cell activating bispecific antigen binding molecule essentially ses an immunoglobulin molecule, wherein in one of the Fab arms the heavy and light chain le regions VH and VL are exchanged/replaced by each other (see Figure 1A, D).

In alternative embodiments, the third Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first or second subunit of the Fc domain. In a particular such embodiment, the second and the third Fab le are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain, and the first Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. In this embodiment, the T cell activating bispecific antigen binding molecule essentially comprises an immunoglobulin le, wherein in one of the Fab arms the heavy and light chain variable regions VH and VL are ged/replaced by each other, and wherein an additional (conventional) Fab molecule is inally fused to said Fab arm (see Figure 1B, E). In another such embodiment, the first and the third Fab molecule are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain, and the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. In this embodiment, the T cell activating bispecific antigen binding molecule essentially comprises an immunoglobulin molecule with an additional Fab molecule N-terminally fused to one of the immunoglobulin Fab arms, wherein in said onal Fab molecule the heavy and light chain variable regions VH and VL are exchanged/replaced by each other (see Figure 1C, F).

In all of the different configurations of the T cell activating bispecific n binding molecule according to the description, the amino acid substitutions described herein may either be in the CH1 and CL domains of the first and (if present) the third Fab molecule, or in the CH1 and CL domains of the second Fab molecule. Preferably, they are in the CH1 and CL domains of the first and (if present) the third Fab molecule. In accordance with the concept of the description, if amino acid substitutions as bed herein are made in the first (and, if present, the third) Fab molecule, no such amino acid substitutions are made in the second Fab molecule. Conversely, if amino acid substitutions as described herein are made in the second Fab le, no such amino acid substitutions are made in the first (and, if present, the third) Fab molecule.

In particular embodiments of the T cell activating bispecific antigen binding molecule according to the ption, particularly wherein amino acid substitutions as described herein are made in the first (and, if present, the third) Fab le, the constant domain CL of the first (and, if present, the third) Fab molecule is of kappa isotype. In other embodiments of the T cell activating bispecific antigen binding molecule according to the description, particularly wherein amino acid substitutions as described herein are made in the second Fab molecule, the constant domain CL of the second Fab le is of kappa isotype. In some embodiments, the constant domain CL of the first (and, if present, the third) Fab molecule and the constant domain CL of the second Fab molecule are of kappa isotype.

In a particular embodiment, the immunoglobulin molecule comprised in the T cell activating bispecific antigen binding molecule according to the description is an IgG class immunoglobulin.

In an even more particular embodiment the globulin is an IgG1 subclass immunoglobulin.

In another embodiment, the immunoglobulin is an IgG4 subclass immunoglobulin.

In a particular embodiment, the description includes a T cell activating ific antigen binding le comprising a) a first Fab molecule which specifically binds to a first n; b) a second Fab molecule which specifically binds to a second antigen, and n the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; c) a third Fab molecule which specifically binds to the first antigen; and d) an Fc domain composed of a first and a second subunit capable of stable association; wherein the first antigen is a target cell n and the second antigen is an activating T cell antigen, particularly CD3, more particularly CD3 epsilon; wherein the third Fab molecule under c) is identical to the first Fab molecule under a); wherein in the constant domain CL of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at on 123 is substituted by lysine (K) or arginine (R) (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab le under a) and the third Fab molecule under c) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at on 213 is substituted by ic acid (E) (numbering according to Kabat EU index); and wherein (i) the first Fab molecule under a) is fused at the C-terminus of the Fab heavy chain to the N- terminus of the Fab heavy chain of the second Fab molecule under b), and the second Fab molecule under b) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d), or (ii) the second Fab molecule under b) is fused at the C-terminus of the Fab heavy chain to the N- terminus of the Fab heavy chain of the first Fab molecule under a), and the first Fab molecule under a) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d).

In an even more particular embodiment, the ption includes a T cell activating bispecific antigen binding molecule comprising a) a first Fab le which specifically binds to a first antigen; b) a second Fab molecule which specifically binds to a second antigen, and wherein the le domains VL and VH of the Fab light chain and the Fab heavy chain are ed by each other; c) a third Fab molecule which specifically binds to the first antigen; and d) an Fc domain composed of a first and a second subunit capable of stable association; wherein the first n is a target cell n and the second antigen is an activating T cell antigen, particularly CD3, more particularly CD3 epsilon; wherein the third Fab molecule under c) is identical to the first Fab molecule under a); wherein in the constant domain CL of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 124 is substituted by lysine (K) ring according to Kabat) and the amino acid at position 123 is substituted by arginine (R) (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index); and wherein the first Fab molecule under a) is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule under b), and the second Fab molecule under b) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d).

In a further embodiment, the description includes a T cell activating bispecific antigen binding le comprising a) a first Fab molecule which specifically binds to a first antigen; b) a second Fab molecule which specifically binds to a second n, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are ed by each other; c) an Fc domain composed of a first and a second t capable of stable association; wherein (i) the first antigen is a target cell antigen and the second antigen is an activating T cell antigen, ularly CD3, more particularly CD3 epsilon; or (ii) the second antigen is a target cell antigen and the first antigen is an activating T cell antigen, particularly CD3, more particularly CD3 epsilon; wherein in the nt domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by lysine (K) or arginine (R) (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index); and wherein the first Fab molecule under a) and the second Fab molecule under b) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under c).

In ular embodiments of the T cell activating ific antigen binding molecule, the Fc domain is an IgG Fc . In a specific embodiment, the Fc domain is an IgG1 Fc domain. In another specific embodiment, the Fc domain is an IgG4 Fc domain. In an even more specific embodiment, the Fc domain is an IgG4 Fc domain comprising the amino acid substitution S228P (Kabat numbering). In particular embodiments the Fc domain is a human Fc domain.

In particular embodiments, the Fc domain comprises a modification promoting the association of the first and the second Fc domain subunit. In a specific such embodiment, an amino acid e in the CH3 domain of the first subunit of the Fc domain is ed with an amino acid residue having a larger side chain volume, thereby generating a protuberance within the CH3 domain of the first subunit which is positionable in a cavity within the CH3 domain of the second subunit, and an amino acid residue in the CH3 domain of the second subunit of the Fc domain is replaced with an amino acid residue having a smaller side chain volume, y generating a cavity within the CH3 domain of the second subunit within which the protuberance within the CH3 domain of the first subunit is positionable.

In a particular embodiment the Fc domain exhibits reduced binding affinity to an Fc receptor and/or reduced or function, as compared to a native IgG1 Fc domain. In certain embodiments the Fc domain is engineered to have reduced binding affinity to an Fc or and/or reduced effector function, as compared to a gineered Fc domain. In one embodiment, the Fc domain comprises one or more amino acid substitution that reduces binding to an Fc receptor and/or effector function. In one embodiment, the one or more amino acid substitution in the Fc domain that reduces binding to an Fc receptor and/or effector on is at one or more position ed from the group of L234, L235, and P329 (Kabat EU index numbering). In particular embodiments, each subunit of the Fc domain comprises three amino acid tutions that reduce binding to an Fc receptor and/or effector on wherein said amino acid substitutions are L234A, L235A and P329G (Kabat EU index ing). In one such embodiment, the Fc domain is an IgG1 Fc domain, particularly a human IgG1 Fc domain. In other embodiments, each subunit of the Fc domain comprises two amino acid tutions that reduce binding to an Fc receptor and/or effector function n said amino acid substitutions are L235E and P329G (Kabat EU index numbering). In one such embodiment, the Fc domain is an IgG4 Fc domain, particularly a human IgG4 Fc domain. In one embodiment, the Fc domain of the T cell activating bispecific antigen binding molecule is an IgG4 Fc domain and comprises the amino acid substitutions L235E and S228P (SPLE) (Kabat EU index numbering).

In one embodiment the Fc receptor is an Fcγ receptor. In one embodiment the Fc receptor is a human Fc receptor. In one embodiment, the Fc receptor is an activating Fc or. In a ic embodiment, the Fc receptor is human FcγRIIa, FcγRI, and/or FcγRIIIa. In one embodiment, the effector function is antibody-dependent cell-mediated cytotoxicity (ADCC).

In a specific embodiment of the T cell activating bispecific antigen binding molecule according to the description, the Fab molecule which specifically binds to an activating T cell antigen, particularly CD3, more particularly CD3 n, comprises the heavy chain mentarity determining region (CDR) 1 of SEQ ID NO: 4, the heavy chain CDR 2 of SEQ ID NO: 5, the heavy chain CDR 3 of SEQ ID NO: 6, the light chain CDR 1 of SEQ ID NO: 8, the light chain CDR 2 of SEQ ID NO: 9 and the light chain CDR 3 of SEQ ID NO: 10. In an even more specific embodiment, the Fab molecule which specifically binds to an activating T cell antigen, particularly CD3, more particularly CD3 epsilon, ses a heavy chain variable region comprising an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 7. In one specific embodiment, the second Fab molecule comprised in the T cell activating bispecific n binding molecule according to the description specifically binds to CD3, more particularly CD3 epsilon, and comprises the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 4, the heavy chain CDR 2 of SEQ ID NO: 5, the heavy chain CDR 3 of SEQ ID NO: 6, the light chain CDR 1 of SEQ ID NO: 8, the light chain CDR 2 of SEQ ID NO: 9 and the light chain CDR 3 of SEQ ID NO: 10. In an even more specific embodiment, said second Fab molecule comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 7.

In a further specific embodiment of the T cell activating bispecific antigen binding molecule according to the description, the Fab molecule which specifically binds to a target cell antigen, particularly CD20, comprises the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 46, the heavy chain CDR 2 of SEQ ID NO: 47, the heavy chain CDR 3 of SEQ ID NO: 48, the light chain CDR 1 of SEQ ID NO: 49, the light chain CDR 2 of SEQ ID NO: 50 and the light chain CDR 3 of SEQ ID NO: 51. In an even more specific embodiment, the Fab molecule which specifically binds to a target cell antigen, particularly CD20, comprises a heavy chain variable region comprising an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 30 and a light chain variable region comprising an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 31. In one specific embodiment, the first (and, if present, the third) Fab molecule comprised in the T cell ting bispecific antigen binding molecule ing to the description specifically binds to CD20, and comprises the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 46, the heavy chain CDR 2 of SEQ ID NO: 47, the heavy chain CDR 3 of SEQ ID NO: 48, the light chain CDR 1 of SEQ ID NO: 49, the light chain CDR 2 of SEQ ID NO: 50 and the light chain CDR 3 of SEQ ID NO: 51. In an even more specific embodiment, said first (and, if t, said third) Fab molecule comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 30 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 31.

In a particular embodiment, the description includes a T cell activating bispecific antigen binding molecule sing a) a first Fab molecule which specifically binds to a first antigen; b) a second Fab molecule which specifically binds to a second antigen, and n the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; c) a third Fab le which specifically binds to the first antigen; and d) an Fc domain composed of a first and a second subunit capable of stable association; (i) the first antigen is CD20 and the second antigen is CD3, ularly CD3 epsilon; (ii) the first Fab molecule under a) and the third Fab molecule under c) each comprise the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 46, the heavy chain CDR 2 of SEQ ID NO: 47, the heavy chain CDR 3 of SEQ ID NO: 48, the light chain CDR 1 of SEQ ID NO: 49, the light chain CDR 2 of SEQ ID NO: 50 and the light chain CDR 3 of SEQ ID NO: 51, and the second Fab molecule under b) comprises the heavy chain CDR 1 of SEQ ID NO: 4, the heavy chain CDR 2 of SEQ ID NO: 5, the heavy chain CDR 3 of SEQ ID NO: 6, the light chain CDR 1 of SEQ ID NO: 8, the light chain CDR 2 of SEQ ID NO: 9 and the light chain CDR 3 of SEQ ID NO: 10; (iii) in the nt domain CL of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by lysine (K) or arginine (R), particularly by arginine (R) (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index); and (iv) the first Fab molecule under a) is fused at the C-terminus of the Fab heavy chain to the N- terminus of the Fab heavy chain of the second Fab le under b), and the second Fab molecule under b) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d).

In a r embodiment, the description includes a T cell activating bispecific antigen g le comprising a) a first Fab molecule which specifically binds to a first antigen; b) a second Fab molecule which specifically binds to a second antigen, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; c) a third Fab molecule which specifically binds to the first n; and d) an Fc domain composed of a first and a second t capable of stable association; wherein (i) the first antigen is CD20 and the second antigen is CD3, particularly CD3 epsilon; (ii) the first Fab molecule under a) and the third Fab molecule under c) each se the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 46, the heavy chain CDR 2 of SEQ ID NO: 47, the heavy chain CDR 3 of SEQ ID NO: 48, the light chain CDR 1 of SEQ ID NO: 49, the light chain CDR 2 of SEQ ID NO: 50 and the light chain CDR 3 of SEQ ID NO: 51, and the second Fab molecule under b) comprises the heavy chain CDR 1 of SEQ ID NO: 4, the heavy chain CDR 2 of SEQ ID NO: 67, the heavy chain CDR 3 of SEQ ID NO: 6, the light chain CDR 1 of SEQ ID NO: 68, the light chain CDR 2 of SEQ ID NO: 9 and the light chain CDR 3 of SEQ ID NO: 10; (iii) in the nt domain CL of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by lysine (K) or arginine (R), particularly by arginine (R) (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 147 is tuted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index); and (iv) the first Fab molecule under a) is fused at the C-terminus of the Fab heavy chain to the N- us of the Fab heavy chain of the second Fab molecule under b), and the second Fab molecule under b) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d). ing to another aspect of the invention there is provided one or more isolated polynucleotide(s) encoding a T cell activating bispecific antigen g molecule of the invention. The invention further provides one or more expression vector(s) comprising the isolated polynucleotide(s) of the invention, and a host cell comprising the ed polynucleotide(s) or the sion vector(s) of the invention. In some embodiments the host cell is a eukaryotic cell, particularly a mammalian cell.

In r aspect is provided a method of ing the T cell activating bispecific antigen binding molecule of the invention, comprising the steps of a) culturing the host cell of the invention under conditions suitable for the expression of the T cell activating bispecific antigen binding molecule and b) recovering the T cell activating bispecific antigen binding molecule.

The ption also encompasses a T cell activating ific antigen binding molecule produced by the method of the invention.

The invention further provides a pharmaceutical composition comprising the T cell activating bispecific antigen binding molecule of the invention and a ceutically acceptable carrier.

Also encompassed by the invention are s of using the T cell activating bispecific antigen binding le and pharmaceutical composition of the invention. In one aspect the invention provides a T cell activating bispecific antigen binding molecule or a pharmaceutical composition of the ion for use as a medicament. In one aspect is provided a T cell activating bispecific antigen binding molecule or a pharmaceutical composition according to the invention for use in the treatment of a e in an individual in need thereof. In a specific embodiment the disease is cancer.

Also provided is the use of a T cell ting bispecific n binding molecule of the invention for the manufacture of a ment for the treatment of a disease in an individual in need thereof. The description includes a method of treating a disease in an individual, comprising administering to said individual a therapeutically effective amount of a composition sing the T cell activating bispecific antigen binding molecule according to the invention in a pharmaceutically acceptable form. In a specific embodiment the disease is cancer. In any of the above embodiments the individual preferably is a mammal, particularly a human.

The description also includes a method for inducing lysis of a target cell, particularly a tumor cell, comprising contacting a target cell with a T cell activating bispecific antigen g molecule of the description in the ce of a T cell, particularly a cytotoxic T cell.

Brief Description of the Drawings FIGURE 1. Exemplary configurations of the T cell activating bispecific antigen binding molecules (TCBs) of the description. (A, D) Illustration of the “1+1 CrossMab” molecule. (B, E) ration of the “2+1 IgG Crossfab” molecule with alternative order of Crossfab and Fab components (“inverted”). (C, F) Illustration of the “2+1 IgG Crossfab” molecule. (G, K) Illustration of the “1+1 IgG Crossfab” molecule with alternative order of Crossfab and Fab ents (“inverted”). (H, L) Illustration of the “1+1 IgG ab” molecule. (I, M) Illustration of the “2+1 IgG Crossfab” le with two CrossFabs. (J, N) Illustration of the “2+1 IgG Crossfab” molecule with two CrossFabs and ative order of Crossfab and Fab components (“inverted”). (O, S) Illustration of the rossfab” molecule. (P, T) ration of the “Crossfab-Fab” molecule. (Q, U) Illustration of the “(Fab)2-Crossfab” molecule. (R, V) ration of the “Crossfab-(Fab)2” molecule. (W, Y) Illustration of the “Fab-(Crossfab)2” molecule. (X, Z) Illustration of the “(Crossfab)2-Fab” molecule. Black dot: optional modification in the Fc domain promoting heterodimerization. ++, --: amino acids of opposite charges introduced in the CH and CL domains.

FIGURE 2. Illustration of the TCBs prepared in Example 1. (A) “2+1 IgG CrossFab, inverted” without charge modifications (CH1/CL exchange in CD3 binder), (B) “2+1 IgG CrossFab, inverted” with charge modifications (VH/VL ge in CD3 binder, charge modification in CD20 binders, EE = 147E, 213E; RK = 123R, 124K), (C) “2+1 IgG CrossFab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in CD20 binders, EE = 147E, 213E; RK = 123R, 124K), (D) “2+1 IgG ab, ed” without charge modifications (VH/VL exchange in CD3 binder), (E) “2+1 IgG ab, inverted” without charge modifications (VH-CH1/VL-CL exchange in CD3 binder), (F) “2+1 IgG CrossFab, inverted” with charge cations (VH/VL exchange in CD20 binders, charge modification in CD3 binder, EE = 147E, 213E; KK = 123K, 124K), (G) “2+1 IgG CrossFab, inverted” with charge modifications and DDKK on in Fc region (VH/VL exchange in CD3 binder, charge modification in CD20 binders, EE = 147E, 213E; RK = 123R, 124K), (H) “1+1 CrossMab” with charge modifications (VH/VL exchange in CD3 binder, charge cation in CD20 binder, EE = 147E, 213E; RK = 123R, 124K), (I) “1+1 CrossMab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in CD20 binder, EE = 147E, 213E; RK = 123R, 124K, different CD20 binder), (J) “2+1 IgG CrossFab, inverted” with charge modifications 213E, 123R (VH/VL exchange in CD3 binder, charge modification in CD20 binder, E = 213E; R = 123R), (K) “2+1 IgG CrossFab, inverted” with charge modifications (VH/VL exchange and charge modification in CD3 ).

FIGURE 3. (A-I, N, O) CE-SDS analysis of the TCBs prepared in Example 1 (final purified preparations). (A) Electropherogram of molecule ”A”, shown in Figure 2A, (B) electropherogram of molecule ”B”, shown in Figure 2B, (C) electropherogram of molecule ”C”, shown in Figure 2C, (D) electropherogram of molecule ”D”, shown in Figure 2D, (E) electropherogram of molecule ”E”, shown in Figure 2E, (F) electropherogram of molecule ”F”, shown in Figure 2F, (G) electropherogram of molecule ”G”, shown in Figure 2G, (H) electropherogram of molecule ”H”, shown in Figure 2H, (I) opherogram of molecule ”I”, shown in Figure 2I, (N) Electropherogram of molecule ”J”, shown in Figure 2J, (O) electropherogram of molecule ”K”, shown in Figure 2K. Lane A = non-reduced, lane B = reduced. (J-L, P, Q) SDS-PAGE analysis of TCBs prepared in Example 1 after the first purification step (Protein A affinity chromatography). (J) 4-12% Bis-Tris SDS-PAGE, non reduced; lane 1 = marker (Mark 12, ned standard, Invitrogen); lane 2-11 = fractions from Protein A affinity chromatography of molecule B, (K) 3-8% cetate SDS-PAGE, non reduced; lane 1 = marker k, Invitrogen); lane 2-12 = fractions from Protein A affinity chromatography of molecule C, (L) 4-12% Bis-Tris SDS-PAGE, non reduced; lane 1 = marker (Mark 12, unstained standard, Invitrogen); lane 2-14 = ons from Protein A affinity chromatography of molecule D, (P) 4-12 % Bis/Tris SDS PAGE, non reduced; lane 1 = marker (Mark 12, Invitrogen); lane 2 -10 = fractions from Protein A affinity chromatography of molecule J, (Q) 4-12 % Bis/Tris SDS PAGE, non reduced; lane 1 = marker (Mark 12, Invitrogen); lane 2 -12= fractions from Protein A affinity chromatography of molecule K. (M) Preparative size exclusion chromatography (SEC; first purification step) of TCBs prepared in Example 1 (molecule A (first SEC step), B and D, as indicated).

FIGURE 4. CD3 and CD20 g of anti-CD3 / anti-CD20 T cell bispecific (TCB) antibodies (“CD20 TCB”) with or without charge modifications (“charge residues”) (see Example 1).

FIGURE 5. Tumor cell lysis induced by anti-CD3 / anti-CD20 T cell bispecific (TCB) antibodies (“CD20 TCB”) with or without charge modifications (“charge residues”) upon 22 h incubation with human PBMCs (see Example 1).

FIGURE 6. Activation of CD8+ T cells (A) or CD4+ T cells (B) upon T cell-mediated killing of CD20-expressing tumor target cells (Nalm-6) induced by D3 / anti-CD20 T cell bispecific (TCB) dies (“CD20 TCB”) with or without charge modifications (“charge residues”) (see Example 1).

FIGURE 7. Activation of CD8+ T cells (A) or CD4+ T cells (B) upon T ediated killing of CD20-expressing tumor target cells (Z-138) induced by anti-CD3 / anti-CD20 T cell bispecific (TCB) dies (“CD20 TCB”) with or without charge modifications (“charge residues”) (see Example 1).

FIGURE 8. B cell depletion in y human whole blood upon incubation with anti-CD3 / anti- CD20 T cell bispecific (TCB) antibodies (“CD20 TCB”) with or without charge cations (“charge residues”); 22 h assay (see Example 1).

FIGURE 9. Activation of CD8+ T cells (A) or CD4+ T cells (B) upon T cell-mediated killing of CD20-expressing B cells in human healthy whole blood induced by anti-CD3 / anti-CD20 T cell bispecific (TCB) antibodies (“CD20 TCB”) with or without charge cations (“charge residues”) (see Example 1).

FIGURE 10. Binding of anti-CD20 / anti-CD3 TCB ule “B” shown in Figure 2B) to human CD20- (A) and CD3-expressing (B) target cells.

FIGURE 11. Binding of anti-CD20 / anti-CD3 TCB ule “B” shown in Figure 2B) to human and lgus monkey CD20- and CD3-expressing target cells. (A) s, (B) CD4 T cells, (C) CD8 T cells.

FIGURE 12. Tumor cell lysis mediated by different anti-CD20 / anti-CD3 TCB antibody formats.

FIGURE 13. Tumor cell lysis and subsequent T cell activation mediated by different anti-CD20 / D3 TCB antibody formats. (A-C) Lysis of Z138 tumor target cells by PBMC effector cells from three different human donors. (D) Lysis of a panel of DLBCL tumor cell lines as indicated.

FIGURE 14. B cell depletion in human whole blood mediated by different anti-CD20 / anti-CD3 TCB antibody formats.

FIGURE 15. Activation of T cells by different anti-CD20 / anti-CD3 TCB antibody formats, assessed by quantification of the intensity of CD3 downstream signaling using Jurkat-NFAT reporter assay.

FIGURE 16. Pharmacokinetic parameters of a 0.5 mg/kg i.v. bolus administration of anti-CD20 / anti-CD3 TCB antibody (molecule “B” shown in Figure 2B) from sparse sampling data in NOG mice.

FIGURE 17. tic representation of the study design to assess B cell depletion activity of anti-CD20 / anti-CD3 TCB antibody (molecule “B” shown in Figure 2B) in fully humanized NOG mice.

FIGURE 18. Kinetics of B-cell and T-cell frequency in blood of fully humanized NOG mice treated with (B) anti-CD20 / D3 TCB antibody (molecule “B” shown in Figure 2B) or (A) vehicle control. D0, D7: days of therapy injection.

FIGURE 19. Analysis of different surface markers expression on peripheral T-cells three days (D3) and ten days (D10) after vehicle (black bars) or anti-CD20 / anti-CD3 TCB antibody ule “B” shown in Figure 2B) (white bars) injection in fully humanized mice.

FIGURE 20. Analysis of B-cell frequency (A), T-cell frequency (B) and surface markers expression on T-cells (C) in spleen of e (black bars) or anti-CD20 / anti-CD3 TCB dy (molecule “B” shown in Figure 2B) (white bars)-treated fully humanized mice at study ation (D10 after first therapeutic injection).

FIGURE 21. Anti-tumor ty of D20 / D3 TCB antibody (molecule “B” shown in Figure 2B) (0.5 mg/kg, once a week) in the WSU-DLCL2 model in NOG mice with huPBMC transfer.

FIGURE 22. Illustration of the “2+1 IgG CrossFab, inverted” molecules prepared in Example 2. (1) Molecule without charge cations, (2) molecule with charge modifications in the CH1 and CL domains of the Fab molecules which specifically bind to BCMA (EE = 147E, 213E; KK = 123K, 124K).

FIGURE 23. CE-SDS analysis (lane A = non-reduced, lang B = reduced, peak table for lane A) of “2+1 IgG CrossFab, inverted” molecules used in Example 2. Different methods of purification (Protein A ty chromatography (PA), size exclusion chromatography (SEC), cation exchange chromatography (cIEX), and a final size exclusion tographic step (re-SEC)) were applied for the molecule without charge modifications (83A10-TCB) and the molecule with charge modifications (83A10-TCBcv).

FIGURE 24. CE-SDS analysis (lane A = non-reduced, lane B = reduced, peak table for lane A) of “2+1 IgG CrossFab, inverted” molecules used in Example 2, in head-to-head (H2H) comparison after Protein A affinity chromatography (PA) and size exclusion tographic (SEC) purification steps.

FIGURE 25. Flow cytometry analysis of binding of anti-BCMA/anti-CD3 T-cell ific antibodies to BCMA-positive le myeloma cell lines. (A) 83A10-TCB on H929 cells and MKN45 cells, (B) 83A10-TCBcv on H929 cells and MKN45 cells, (C) comparison of 83A10- TCB and 83A10-TCBcv on H929 cells.

FIGURE 26. Killing of BCMA-positive H929 myeloma cells by anti-BCMA/anti-CD3 TCB antibodies ((A) TCB, (B) 83A10-TCBcv) as measured by LDH release.

FIGURE 27. Illustration of the TCBs prepared in Example 3. (A) “2+1 IgG CrossFab, inverted” with charge modifications (VH/VL exchange in CD3 binder, charge modification in Her2 binders, EE = 147E, 213E; RK = 123R, 124K), (B) “2+1 IgG CrossFab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in Her3 binders, EE = 147E, 213E; RK = 123R, 124K).

FIGURE 28. CE-SDS analysis of the TCBs prepared in Example 3 (final purified preparation).

(A) Electropherogram of Her2 TCB, shown in Figure 27A, (B) electropherogram of Her3 TCB, shown in Figure 27B. Lane A = non-reduced, lane B = d.

FIGURE 29. g of Her2 TCB (A) and Her3 TCB (B) to cells, as determined by FACS.

Median fluorescence intensities for g of the Her2 TCB molecule to human CD3 on Jurkat cells (left) or to human Her2 (A) or Her3 (B) on KPL-4 cells (right), as measured by flow cytometry. Depicted are median fluorescence values, based on triplicates, including SD.

FIGURE 30. T cell activation by Her3 TCB. Upon co-incubation of human PBMC or cells, KPL-4 target cells and increasing concentrations of the Her3 TCB, the percentage of CD69 positive CD8 T cells was measured by FACS after 48h. Shown are triplicates with SD.

FIGURE 31. Activation of Jurkat cells via CD3 after 5h, as determined by luminescence. Upon incubation of KPL4 tumor cells with Jurkat-NFAT er cells (E:T 5:1 (A) or 2.5:1 (B)) and increasing concentrations of the Her2 TCB (A) or the Her3 TCB (B), activation of Jurkats was determined by relative luminescent signals (RLUS) after 5h. EC50 values were calculated by Graph Pad Prism (34.4 pM (A) and 22 pM (B)). Depicted are average values from triplicates, error bars indicate SD.

FIGURE 32. (A, B) Tumor cell lysis, as measured by LDH release, upon incubation of Her2- ve KPL4, N87, T47D or MDA-MB-231 target cells with human PBMC effector cells (E:T 10:1) and increasing concentrations of the Her 2 TCB molecule for 25 h (A) or 46 h (B).

Depicted are average values from triplicates, error bars indicate SD. EC50 values were calculated by GraphPadPrism: 7.5 pM (KPL4 cells), 25.6 pM (N87 cells), 30.6 pM (T47D cells), and 59.9 pM B-231 cells). (C) Tumor cell lysis, as meassured by LDH release, upon incubation of Her3-positive KPL4 target cells with human PBMC or cells (E:T 10:1) and increasing concentrations of the Her 3 TCB molecule for 24 h or 48 h, as indicated. Depicted are average values from triplicates, error bars indicate SD. EC50 values were calculated by GraphPadPrism: 2.54 pM (24 h) and 0.53 pM (48 h).

FIGURE 33. Tumor cell lysis, induced by Her3 TCB, as determined by Caspase 3/7 ty (luminescence). Shown is the relative luminescent signal, that was measured as a consequence of Caspase 3/7 activity in KPLCaspase-3/7 GloSensor target cells after 6.5 h co-incubation with PBMCs (E:T = 10:1) and ent concentrations of Her3 TCB, as indicated. Shown are triplicates with SD. EC50 value was ated by GraphPadPrism: 0.7 pM.

FIGURE 34. Illustration of the TCBs prepared in Example 4. (A) “(Fab)2-CrossFab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in MCSP binders, EE = 147E, 213E; RK = 123R, 124K), (B) “(Fab)2-CrossFab” without charge modifications (VH/VL exchange in CD3 binder).

FIGURE 35. CE-SDS analysis of the TCB with charge modifications prepared in Example 4 (final purified preparation): Electropherogram of (Fab)2-XFab-LC007cv, shown in Figure 34A.

Lane A = duced, lane B = reduced.

FIGURE 36. Median fluorescence intensities for binding of the TCB molecules to human MCSP on MV-3 cells (left) or to human CD3 on Jurkat cells (right), as measured by flow cytometry.

Depicted are median fluorescence values, based on cates, ing SD.

FIGURE 37. Tumor cell lysis, as measured by LDH release, upon incubation of human MCSP- positive MV-3 cells with human PBMC effector cells (E:T 10:1) and increasing concentrations of the TCB molecules for 24h (left) or 48h (right). Depicted are average values from triplicates, error bars indicate SD.

Detailed Description of the Invention Definitions Terms are used herein as generally used in the art, unless otherwise defined in the following.

As used herein, the term "antigen binding le" refers in its broadest sense to a molecule that specifically binds an antigenic determinant. es of antigen binding molecules are immunoglobulins and tives, e.g. fragments, thereof.

The term cific” means that the antigen binding molecule is able to specifically bind to at least two distinct antigenic determinants. Typically, a ific antigen binding molecule comprises two antigen binding sites, each of which is specific for a different antigenic determinant. In certain embodiments the bispecific antigen binding molecule is capable of simultaneously binding two antigenic determinants, particularly two antigenic inants expressed on two distinct cells.

The term “valent” as used herein denotes the presence of a specified number of antigen binding sites in an antigen binding molecule. As such, the term “monovalent binding to an antigen” denotes the ce of one (and not more than one) antigen binding site specific for the antigen in the n binding molecule.

An “antigen binding site” refers to the site, i.e. one or more amino acid residues, of an antigen binding molecule which provides interaction with the antigen. For example, the antigen binding site of an antibody comprises amino acid residues from the complementarity determining regions (CDRs). A native immunoglobulin molecule typically has two antigen binding sites, a Fab molecule typically has a single antigen g site.

As used herein, the term "antigen binding moiety" refers to a polypeptide molecule that specifically binds to an nic inant. In one ment, an antigen binding moiety is able to direct the entity to which it is attached (e.g. a second antigen binding moiety) to a target site, for example to a specific type of tumor cell or tumor stroma bearing the antigenic determinant. In another ment an antigen binding moiety is able to activate signaling through its target antigen, for example a T cell or complex antigen. Antigen binding moieties include antibodies and fragments thereof as further defined herein. Particular antigen g moieties include an n binding domain of an antibody, comprising an antibody heavy chain variable region and an antibody light chain variable region. In certain embodiments, the antigen binding moieties may comprise antibody constant regions as r defined herein and known in the art. Useful heavy chain constant regions include any of the five isotypes: α, δ, ε, γ, or μ. Useful light chain constant s include any of the two isotypes: κ and λ.

As used herein, the term "antigenic determinant" is synonymous with "antigen" and "epitope," and refers to a site (e.g. a contiguous stretch of amino acids or a mational configuration made up of different s of ntiguous amino acids) on a polypeptide macromolecule to which an antigen binding moiety binds, forming an antigen binding moiety-antigen complex.

Useful antigenic determinants can be found, for example, on the surfaces of tumor cells, on the surfaces of virus-infected cells, on the surfaces of other diseased cells, on the surface of immune cells, free in blood serum, and/or in the extracellular matrix (ECM). The proteins ed to as antigens herein (e.g. CD3) can be any native form the proteins from any vertebrate source, ing mammals such as primates (e.g. humans) and rodents (e.g. mice and rats), unless otherwise indicated. In a particular embodiment the antigen is a human protein. Where nce is made to a specific protein herein, the term encompasses the “full-length”, unprocessed protein as well as any form of the n that results from processing in the cell. The term also asses naturally occurring variants of the protein, e.g. splice variants or allelic variants.

An exemplary human protein useful as antigen is CD3, particularly the epsilon subunit of CD3 (see UniProt no. P07766 (version 130), NCBI RefSeq no. NP_000724.1, SEQ ID NO: 1 for the human sequence; or UniProt no. Q95LI5 (version 49), NCBI GenBank no. BAB71849.1, SEQ ID NO: 2 for the cynomolgus [Macaca fascicularis] sequence). In certain embodiments the T cell activating ific antigen binding molecule of the description binds to an epitope of CD3 or a target cell antigen that is conserved among the CD3 or target cell antigen from different species.

By "specific binding" is meant that the binding is ive for the antigen and can be discriminated from unwanted or ecific interactions. The ability of an antigen binding moiety to bind to a specific antigenic determinant can be measured either through an enzymelinked immunosorbent assay ) or other techniques familiar to one of skill in the art, e.g. surface plasmon resonance (SPR) technique (analyzed on a BIAcore instrument) blad et al., Glyco J 17, 323-329 (2000)), and traditional binding assays (Heeley, Endocr Res 28, 217-229 (2002)). In one embodiment, the extent of g of an antigen binding moiety to an unrelated protein is less than about 10% of the binding of the antigen binding moiety to the n as measured, e.g., by SPR. In certain ments, an antigen binding moiety that binds to the antigen, or an antigen binding molecule comprising that antigen binding moiety, has a dissociation constant (KD) of ≤ 1 μM, ≤ 100 nM, ≤ 10 nM, ≤ 1 nM, ≤ 0.1 nM, ≤ 0.01 nM, or ≤ 0.001 nM (e.g. 10-8 M or less, e.g. from 10-8 M to 10-13 M, e.g., from 10-9 M to 10-13 M).

“Affinity” refers to the strength of the sum total of non-covalent ctions between a single binding site of a molecule (e.g., a receptor) and its binding partner (e.g., a ligand). Unless indicated otherwise, as used herein, “binding affinity” refers to intrinsic binding affinity which reflects a 1:1 ction between members of a binding pair (e.g., an antigen binding moiety and an antigen, or a receptor and its ligand). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (KD), which is the ratio of dissociation and association rate constants (koff and kon, respectively). Thus, equivalent affinities may comprise different rate constants, as long as the ratio of the rate constants s the same. Affinity can be measured by well established methods known in the art, including those described herein. A ular method for measuring affinity is Surface Plasmon Resonance (SPR).

“Reduced binding”, for example reduced binding to an Fc receptor, refers to a decrease in ty for the respective interaction, as ed for example by SPR. For clarity the term includes also reduction of the affinity to zero (or below the detection limit of the analytic method), i.e. complete abolishment of the interaction. Conversely, “increased binding” refers to an increase in binding ty for the tive interaction.

An “activating T cell antigen” as used herein refers to an antigenic determinant expressed on the surface of a T cyte, particularly a cytotoxic T lymphocyte, which is capable of inducing T cell activation upon interaction with an antigen g molecule. Specifically, interaction of an antigen binding molecule with an activating T cell antigen may induce T cell activation by triggering the signaling cascade of the T cell receptor complex. In a particular ment the ting T cell antigen is CD3, particularly the n subunit of CD3 (see UniProt no. P07766 (version 130), NCBI RefSeq no. NP_000724.1, SEQ ID NO: 1 for the human sequence; or UniProt no. Q95LI5 on 49), NCBI GenBank no. BAB71849.1, SEQ ID NO: 2 for the cynomolgus [Macaca fascicularis] sequence).

“T cell activation” as used herein refers to one or more cellular response of a T lymphocyte, particularly a cytotoxic T lymphocyte, selected from: proliferation, differentiation, cytokine secretion, cytotoxic effector molecule release, cytotoxic activity, and sion of activation markers. The T cell activating bispecific antigen g les of the description are capable of inducing T cell activation. Suitable assays to measure T cell activation are known in the art described herein.

A “target cell antigen” as used herein refers to an nic determinant presented on the surface of a target cell, for example a cell in a tumor such as a cancer cell or a cell of the tumor stroma.

In a particular embodiment, the target cell antigen is CD20, particularly human CD20 (see UniProt no. P11836).

As used , the terms “first”, “second” or “third” with respect to Fab les etc., are used for convenience of distinguishing when there is more than one of each type of moiety. Use of these terms is not intended to confer a specific order or orientation of the T cell activating bispecific antigen g molecule unless explicitly so stated.

A “Fab molecule” refers to a protein consisting of the VH and CH1 domain of the heavy chain (the “Fab heavy chain”) and the VL and CL domain of the light chain (the “Fab light chain”) of an immunoglobulin.

By “fused” is meant that the components (e.g. a Fab le and an Fc domain subunit) are linked by peptide bonds, either directly or via one or more peptide linkers.

As used herein, the term "single-chain" refers to a le comprising amino acid monomers linearly linked by peptide bonds. In certain embodiments, one of the n binding moieties is a single-chain Fab molecule, i.e. a Fab molecule wherein the Fab light chain and the Fab heavy chain are connected by a peptide linker to form a single peptide chain. In a particular such ment, the C-terminus of the Fab light chain is connected to the N-terminus of the Fab heavy chain in the single-chain Fab molecule.

By a “crossover” Fab molecule (also termed “Crossfab”) is meant a Fab molecule wherein the variable domains of the Fab heavy and light chain are exchanged (i.e. replaced by each other), i.e. the ver Fab molecule comprises a peptide chain composed of the light chain variable domain VL and the heavy chain nt domain 1 CH1 (VL-CH1, in N- to C-terminal direction), and a peptide chain composed of the heavy chain variable domain VH and the light chain nt domain CL (VH-CL, in N- to C-terminal direction). For clarity, in a crossover Fab molecule wherein the variable domains of the Fab light chain and the Fab heavy chain are exchanged, the peptide chain comprising the heavy chain constant domain 1 CH1 is referred to herein as the “heavy chain” of the crossover Fab molecule.

In contrast thereto, by a “conventional” Fab molecule is meant a Fab molecule in its natural format, i.e. comprising a heavy chain composed of the heavy chain variable and constant domains (VH-CH1, in N- to C-terminal ion), and a light chain composed of the light chain variable and constant domains , in N- to C-terminal direction).

The term “immunoglobulin molecule” refers to a protein having the structure of a naturally occurring antibody. For example, immunoglobulins of the IgG class are heterotetrameric glycoproteins of about 0 daltons, composed of two light chains and two heavy chains that are disulfide-bonded. From N- to C-terminus, each heavy chain has a variable domain (VH), also called a variable heavy domain or a heavy chain variable region, followed by three constant s (CH1, CH2, and CH3), also called a heavy chain constant region. Similarly, from N- to C-terminus, each light chain has a variable domain (VL), also called a variable light domain or a light chain variable region, followed by a constant light (CL) domain, also called a light chain constant region. The heavy chain of an immunoglobulin may be assigned to one of five types, called α (IgA), δ (IgD), ε (IgE), γ (IgG), or μ (IgM), some of which may be further divided into subtypes, e.g. γ1 (IgG1), γ2 (IgG2), γ3 (IgG3), γ4 (IgG4), α1 (IgA1) and α2 (IgA2). The light chain of an immunoglobulin may be assigned to one of two types, called kappa (κ) and lambda (λ), based on the amino acid sequence of its constant domain. An immunoglobulin essentially consists of two Fab molecules and an Fc domain, linked via the immunoglobulin hinge region.

The term "antibody" herein is used in the broadest sense and asses various antibody structures, including but not limited to onal dies, polyclonal dies, and antibody fragments so long as they t the desired antigen-binding activity.

An "antibody fragment" refers to a molecule other than an intact antibody that comprises a n of an intact antibody that binds the antigen to which the intact antibody binds. Examples of antibody nts include but are not limited to Fv, Fab, Fab', Fab’-SH, F(ab')2, diabodies, linear dies, single-chain antibody molecules (e.g. scFv), and single-domain antibodies. For a review of certain antibody fragments, see Hudson et al., Nat Med 9, 129-134 (2003). For a review of scFv fragments, see e.g. Plückthun, in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994); see also WO 93/16185; and U.S. Patent Nos. 5,571,894 and 5,587,458. For discussion of Fab and F(ab')2 fragments comprising e receptor binding epitope es and having increased in vivo half-life, see U.S. Patent No. 5,869,046. Diabodies are antibody fragments with two antigenbinding sites that may be bivalent or bispecific. See, for example, EP 404,097; WO 1161; Hudson et al., Nat Med 9, 129-134 (2003); and Hollinger et al., Proc Natl Acad Sci USA 90, 6444-6448 (1993). Triabodies and tetrabodies are also described in Hudson et al., Nat Med 9, 129-134 (2003). -domain antibodies are antibody fragments comprising all or a portion of the heavy chain variable domain or all or a portion of the light chain variable domain of an antibody. In certain embodiments, a single-domain antibody is a human -domain antibody (Domantis, Inc., Waltham, MA; see e.g. U.S. Patent No. 6,248,516 B1). Antibody fragments can be made by various techniques, including but not limited to lytic digestion of an intact antibody as well as production by recombinant host cells (e.g. E. coli or phage), as described herein.

The term "antigen binding domain" refers to the part of an antibody that comprises the area which specifically binds to and is complementary to part or all of an antigen. An antigen binding domain may be provided by, for example, one or more antibody variable domains (also called antibody variable regions). Particularly, an antigen binding domain ses an antibody light chain variable domain (VL) and an antibody heavy chain variable domain (VH).

The term “variable region” or “variable domain” refers to the domain of an dy heavy or light chain that is involved in binding the antibody to antigen. The variable domains of the heavy chain and light chain (VH and VL, respectively) of a native antibody generally have similar structures, with each domain comprising four conserved framework regions (FRs) and three hypervariable s (HVRs). See, e.g., Kindt et al., Kuby Immunology, 6th ed., W.H. Freeman and Co., page 91 (2007). A single VH or VL domain may be sufficient to confer antigen-binding specificity.

The term “hypervariable region” or “HVR”, as used herein, refers to each of the regions of an antibody variable domain which are hypervariable in sequence and/or form structurally d loops (“hypervariable loops”). Generally, native four-chain antibodies comprise six HVRs; three in the VH (H1, H2, H3), and three in the VL (L1, L2, L3). HVRs generally comprise amino acid residues from the hypervariable loops and/or from the complementarity ining s (CDRs), the latter being of highest sequence ility and/or involved in antigen recognition.

With the exception of CDR1 in VH, CDRs generally comprise the amino acid residues that form the hypervariable loops. Hypervariable regions (HVRs) are also referred to as “complementarity determining regions” (CDRs), and these terms are used herein interchangeably in reference to portions of the variable region that form the antigen binding regions. This particular region has been bed by Kabat et al., Sequences of ns of logical Interest, 5th Ed. Public Health Service, al Institutes of Health, Bethesda, MD (1991) and by Chothia et al., J Mol Biol 196:901-917 (1987), where the definitions include overlapping or subsets of amino acid residues when compared against each other. Nevertheless, application of either definition to refer to a CDR of an antibody or variants thereof is ed to be within the scope of the term as defined and used herein. The appropriate amino acid residues which encompass the CDRs as d by each of the above cited references are set forth below in Table 1 as a comparison. The exact residue numbers which encompass a particular CDR will vary depending on the sequence and size of the CDR. Those skilled in the art can routinely determine which residues comprise a particular CDR given the variable region amino acid ce of the antibody. The CDR sequences given herein are generally according to the Kabat definition.

TABLE 1. CDR Definitions1 CDR Kabat Chothia AbM2 VH CDR1 31-35 26-32 26-35 VH CDR2 50-65 52-58 50-58 VH CDR3 95-102 95-102 95-102 VL CDR1 24-34 26-32 24-34 VL CDR2 50-56 50-52 50-56 VL CDR3 89-97 91-96 89-97 1 Numbering of all CDR tions in Table 1 is according to the numbering conventions set forth by Kabat et al. (see below). 2 "AbM" with a lowercase “b” as used in Table 1 refers to the CDRs as defined by Oxford Molecular's "AbM" antibody modeling software.

Kabat et al. also defined a numbering system for variable region sequences that is able to any antibody. One of ry skill in the art can unambiguously assign this system of "Kabat numbering" to any variable region sequence, without reliance on any experimental data beyond the sequence itself. As used herein in connection with variable region ces, "Kabat numbering" refers to the numbering system set forth by Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD (1991). Unless otherwise specified, references to the numbering of specific amino acid residue ons in an antibody variable region are according to the Kabat numbering system.

As used herein, the amino acid positions of all constant regions and domains of the heavy and light chain are numbered according to the Kabat numbering system described in Kabat, et al., Sequences of Proteins of Immunological Interest, 5th ed., Public Health Service, National Institutes of Health, Bethesda, MD (1991) and is referred to as “numbering according to Kabat” or “Kabat ing” . Specifically the Kabat numbering system (see pages 647-660 of Kabat, et al., Sequences of Proteins of Immunological Interest, 5th ed., Public Health Service, National Institutes of Health, Bethesda, MD (1991)) is used for the light chain constant domain CL of kappa and lambda isotype and the Kabat EU index numbering system (see pages 661-723) is used for the heavy chain constant domains (CH1, Hinge, CH2 and CH3), which is herein further clarified by referring to “numbering according to Kabat EU index” in this case.

The ptide sequences of the sequence listing are not numbered according to the Kabat numbering system. However, it is well within the ordinary skill of one in the art to convert the numbering of the sequences of the Sequence Listing to Kabat numbering. work" or "FR" refers to variable domain residues other than hypervariable region (HVR) residues. The FR of a variable domain generally ts of four FR domains: FR1, FR2, FR3, and FR4. Accordingly, the HVR and FR ces generally appear in the following sequence in VH (or VL): FR1-H1(L1)-FR2-H2(L2)-FR3-H3(L3)-FR4.

The “class” of an antibody or immunoglobulin refers to the type of nt domain or constant region possessed by its heavy chain. There are five major s of antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2. The heavy chain constant domains that correspond to the different classes of immunoglobulins are called α, δ, ε, γ, and μ, respectively.

The term “Fc domain” or “Fc region” herein is used to define a C-terminal region of an immunoglobulin heavy chain that contains at least a n of the constant region. The term includes native sequence Fc regions and variant Fc regions. Although the boundaries of the Fc region of an IgG heavy chain might vary slightly, the human IgG heavy chain Fc region is usually defined to extend from Cys226, or from Pro230, to the carboxyl-terminus of the heavy chain. However, antibodies produced by host cells may undergo post-translational cleavage of one or more, particularly one or two, amino acids from the C-terminus of the heavy chain.

Therefore an antibody produced by a host cell by expression of a specific nucleic acid molecule encoding a full-length heavy chain may include the full-length heavy chain, or it may include a cleaved variant of the full-length heavy chain (also referred to herein as a “cleaved variant heavy chain”). This may be the case where the final two C-terminal amino acids of the heavy chain are glycine (G446) and lysine (K447, numbering according to Kabat EU . Therefore, the C- terminal lysine 7), or the C-terminal glycine (Gly446) and lysine (K447), of the Fc region may or may not be present. Amino acid sequences of heavy chains including Fc domains (or a subunit of an Fc domain as defined herein) are denoted herein without C-terminal glycine-lysine ide if not indicated otherwise. In one embodiment of the description, a heavy chain including a subunit of an Fc domain as specified herein, comprised in a T cell activating bispecific n binding le according to the ption, comprises an additional C- terminal glycine-lysine dipeptide (G446 and K447, numbering ing to EU index of Kabat).

In one embodiment of the description, a heavy chain including a subunit of an Fc domain as specified herein, comprised in a T cell activating bispecific antigen g molecule according to the description, comprises an additional C-terminal glycine residue (G446, numbering according to EU index of Kabat). Compositions of the description, such as the pharmaceutical compositions described herein, comprise a population of T cell activating bispecific antigen binding les of the description. The population of T cell ting ific antigen binding molecule may comprise les having a full-length heavy chain and molecules having a cleaved variant heavy chain. The population of T cell activating bispecific antigen binding molecules may consist of a e of molecules having a ength heavy chain and les having a cleaved variant heavy chain, wherein at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the T cell activating bispecific antigen binding molecules have a cleaved variant heavy chain. In one embodiment of the description a composition comprising a population of T cell activating bispecific antigen binding molecules of the description comprises an T cell activating bispecific antigen binding le sing a heavy chain including a subunit of an Fc domain as specified herein with an additional C-terminal glycine-lysine dipeptide (G446 and K447, numbering according to EU index of Kabat). In one embodiment of the description a composition comprising a population of T cell activating bispecific antigen binding molecules of the description ses an T cell activating bispecific antigen binding molecule comprising a heavy chain including a t of an Fc domain as specified herein with an additional C-terminal glycine residue (G446, ing according to EU index of Kabat). In one embodiment of the description such a ition comprises a population of T cell activating bispecific antigen binding molecules sed of molecules comprising a heavy chain including a subunit of an Fc domain as specified herein; molecules comprising a heavy chain including a subunit of a Fc domain as specified herein with an additional inal glycine residue (G446, numbering according to EU index of Kabat); and molecules comprising a heavy chain including a subunit of an Fc domain as ied herein with an additional C- terminal glycine-lysine dipeptide (G446 and K447, numbering according to EU index of Kabat).

Unless otherwise specified herein, numbering of amino acid residues in the Fc region or constant region is according to the EU numbering system, also called the EU index, as described in Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD, 1991 (see also above). A “subunit” of an Fc domain as used herein refers to one of the two polypeptides forming the dimeric Fc domain, i.e. a polypeptide comprising inal constant regions of an immunoglobulin heavy chain, capable of stable ssociation. For example, a subunit of an IgG Fc domain ses an IgG CH2 and an IgG CH3 constant .

A “modification promoting the association of the first and the second subunit of the Fc domain” is a lation of the peptide backbone or the post-translational modifications of an Fc domain subunit that reduces or prevents the association of a polypeptide comprising the Fc domain subunit with an identical polypeptide to form a homodimer. A modification promoting association as used herein particularly includes separate modifications made to each of the two Fc domain subunits desired to associate (i.e. the first and the second subunit of the Fc domain), wherein the modifications are complementary to each other so as to promote association of the two Fc domain subunits. For example, a modification promoting association may alter the structure or charge of one or both of the Fc domain subunits so as to make their association ally or electrostatically favorable, tively. Thus, (hetero)dimerization occurs between a polypeptide comprising the first Fc domain subunit and a polypeptide comprising the second Fc domain subunit, which might be entical in the sense that r components fused to each of the ts (e.g. antigen binding moieties) are not the same. In some embodiments the modification ing association comprises an amino acid mutation in the Fc domain, specifically an amino acid substitution. In a particular ment, the cation promoting association comprises a separate amino acid mutation, specifically an amino acid substitution, in each of the two subunits of the Fc domain.

The term “effector functions” refers to those biological activities attributable to the Fc region of an antibody, which vary with the antibody isotype. Examples of antibody effector ons include: C1q binding and complement dependent cytotoxicity (CDC), Fc receptor binding, antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), cytokine secretion, immune x-mediated antigen uptake by antigen presenting cells, down regulation of cell surface receptors (e.g. B cell receptor), and B cell activation.

As used herein, the terms “engineer, engineered, engineering”, are considered to include any manipulation of the peptide backbone or the post-translational modifications of a naturally occurring or inant polypeptide or fragment thereof. Engineering includes cations of the amino acid sequence, of the glycosylation pattern, or of the side chain group of individual amino acids, as well as ations of these approaches.

The term “amino acid mutation” as used herein is meant to encompass amino acid substitutions, deletions, insertions, and modifications. Any combination of substitution, deletion, insertion, and modification can be made to arrive at the final construct, provided that the final uct possesses the desired characteristics, e.g., d binding to an Fc receptor, or increased association with another peptide. Amino acid sequence deletions and insertions include amino- and/or carboxy-terminal deletions and insertions of amino acids. ular amino acid ons are amino acid substitutions. For the purpose of altering e.g. the binding characteristics of an Fc region, non-conservative amino acid substitutions, i.e. replacing one amino acid with another amino acid having different structural and/or chemical properties, are particularly preferred.

Amino acid substitutions include replacement by non-naturally occurring amino acids or by naturally occurring amino acid tives of the twenty standard amino acids (e.g. 4- hydroxyproline, 3-methylhistidine, ornithine, homoserine, 5-hydroxylysine). Amino acid mutations can be generated using genetic or chemical methods well known in the art. Genetic methods may include site-directed mutagenesis, PCR, gene synthesis and the like. It is contemplated that methods of altering the side chain group of an amino acid by methods other than genetic engineering, such as chemical modification, may also be useful. Various designations may be used herein to indicate the same amino acid mutation. For example, a substitution from proline at position 329 of the Fc domain to glycine can be ted as 329G, G329, G329, P329G, or Pro329Gly.

As used herein, term "polypeptide" refers to a le ed of monomers (amino acids) linearly linked by amide bonds (also known as peptide bonds). The term "polypeptide" refers to any chain of two or more amino acids, and does not refer to a specific length of the product.

Thus, peptides, dipeptides, tripeptides, oligopeptides, "protein," "amino acid chain," or any other term used to refer to a chain of two or more amino acids, are included within the definition of "polypeptide," and the term "polypeptide" may be used instead of, or interchangeably with any of these terms. The term "polypeptide" is also intended to refer to the products of post-expression modifications of the polypeptide, including without limitation glycosylation, acetylation, phosphorylation, amidation, derivatization by known protecting/blocking groups, proteolytic cleavage, or modification by non-naturally occurring amino acids. A polypeptide may be derived from a natural biological source or produced by recombinant technology, but is not necessarily translated from a designated nucleic acid sequence. It may be generated in any manner, including by chemical sis. A ptide of the description may be of a size of about 3 or more, 5 or more, 10 or more, 20 or more, 25 or more, 50 or more, 75 or more, 100 or more, 200 or more, 500 or more, 1,000 or more, or 2,000 or more amino acids. Polypeptides may have a defined three-dimensional structure, although they do not arily have such structure. Polypeptides with a defined three-dimensional structure are ed to as folded, and polypeptides which do not possess a d three-dimensional structure, but rather can adopt a large number of different conformations, and are referred to as unfolded.

By an "isolated" polypeptide or a variant, or tive f is ed a polypeptide that is not in its natural milieu. No ular level of purification is required. For example, an isolated polypeptide can be removed from its native or natural environment. Recombinantly produced polypeptides and proteins expressed in host cells are considered isolated for the purpose of the description, as are native or recombinant polypeptides which have been ted, fractionated, or partially or substantially purified by any suitable technique.

“Percent (%) amino acid ce identity" with respect to a reference polypeptide sequence is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the reference polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence ty. Alignment for es of determining percent amino acid ce identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or Megalign (DNASTAR) software. Those skilled in the art can determine appropriate parameters for aligning sequences, ing any thms needed to achieve l alignment over the full length of the sequences being compared. For purposes herein, however, % amino acid ce identity values are generated using the sequence comparison er program ALIGN-2. The ALIGN-2 sequence comparison computer program was authored by Genentech, Inc., and the source code has been filed with user documentation in the U.S. Copyright Office, Washington D.C., 20559, where it is registered under U.S. Copyright Registration No. TXU510087. The ALIGN-2 program is publicly available from Genentech, Inc., South San Francisco, California, or may be compiled from the source code.

The ALIGN-2 program should be compiled for use on a UNIX operating , including digital UNIX V4.0D. All ce ison parameters are set by the ALIGN-2 program and do not vary. In situations where ALIGN-2 is employed for amino acid sequence comparisons, the % amino acid sequence identity of a given amino acid sequence A to, with, or against a given amino acid sequence B (which can alternatively be phrased as a given amino acid sequence A that has or comprises a certain % amino acid sequence ty to, with, or against a given amino acid sequence B) is calculated as follows: 100 times the fraction X/Y where X is the number of amino acid residues scored as identical matches by the sequence alignment program ALIGN-2 in that program’s alignment of A and B, and where Y is the total number of amino acid es in B. It will be appreciated that where the length of amino acid sequence A is not equal to the length of amino acid sequence B, the % amino acid sequence identity of A to B will not equal the % amino acid sequence identity of B to A. Unless specifically stated otherwise, all % amino acid sequence identity values used herein are obtained as described in the immediately ing paragraph using the ALIGN-2 computer program.

The term "polynucleotide" refers to an isolated nucleic acid le or construct, e.g. messenger RNA (mRNA), virally-derived RNA, or plasmid DNA (pDNA). A polynucleotide may comprise a conventional phosphodiester bond or a non-conventional bond (e.g. an amide bond, such as found in peptide nucleic acids (PNA). The term "nucleic acid molecule" refers to any one or more nucleic acid segments, e.g. DNA or RNA fragments, present in a polynucleotide.

By "isolated" nucleic acid molecule or polynucleotide is intended a nucleic acid molecule, DNA or RNA, which has been removed from its native environment. For e, a recombinant polynucleotide encoding a polypeptide ned in a vector is considered isolated for the purposes of the present description. Further examples of an isolated cleotide include recombinant polynucleotides maintained in heterologous host cells or ed ally or substantially) polynucleotides in solution. An isolated polynucleotide includes a polynucleotide molecule contained in cells that ordinarily contain the polynucleotide molecule, but the polynucleotide molecule is present extrachromosomally or at a chromosomal location that is different from its natural chromosomal location. Isolated RNA les include in vivo or in vitro RNA ripts of the present description, as well as positive and negative strand forms, and double-stranded forms. Isolated cleotides or nucleic acids according to the present description further include such molecules produced synthetically. In addition, a polynucleotide or a nucleic acid may be or may include a regulatory element such as a promoter, ribosome binding site, or a transcription terminator.

By a nucleic acid or polynucleotide having a nucleotide sequence at least, for example, 95% "identical" to a reference tide sequence of the t description, it is intended that the tide sequence of the polynucleotide is cal to the reference sequence except that the polynucleotide sequence may include up to five point ons per each 100 nucleotides of the reference nucleotide sequence. In other words, to obtain a polynucleotide having a nucleotide sequence at least 95% identical to a reference nucleotide sequence, up to 5% of the nucleotides in the reference sequence may be deleted or substituted with another nucleotide, or a number of nucleotides up to 5% of the total nucleotides in the reference sequence may be inserted into the reference ce. These alterations of the reference sequence may occur at the 5’ or 3’ terminal positions of the reference nucleotide sequence or anywhere between those terminal positions, persed either individually among residues in the reference sequence or in one or more uous groups within the reference sequence. As a practical matter, whether any particular polynucleotide sequence is at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identical to a nucleotide sequence of the present description can be determined tionally using known computer programs, such as the ones discussed above for polypeptides (e.g.

ALIGN-2).

The term "expression cassette" refers to a polynucleotide generated inantly or synthetically, with a series of specified nucleic acid elements that permit transcription of a particular c acid in a target cell. The recombinant expression cassette can be incorporated into a plasmid, chromosome, mitochondrial DNA, plastid DNA, virus, or c acid fragment.

Typically, the recombinant sion cassette portion of an expression vector includes, among other sequences, a nucleic acid sequence to be transcribed and a promoter. In certain embodiments, the expression cassette of the description ses polynucleotide sequences that encode bispecific antigen binding molecules of the description or fragments thereof.

The term “vector” or "expression vector" is synonymous with ssion construct" and refers to a DNA molecule that is used to introduce and direct the expression of a specific gene to which it is operably associated in a target cell. The term includes the vector as a self-replicating nucleic acid ure as well as the vector incorporated into the genome of a host cell into which it has been uced. The expression vector of the present description comprises an expression cassette. Expression vectors allow transcription of large amounts of stable mRNA. Once the expression vector is inside the target cell, the ribonucleic acid molecule or protein that is d by the gene is produced by the cellular transcription and/or translation machinery. In one embodiment, the expression vector of the description comprises an expression cassette that comprises cleotide sequences that encode bispecific antigen binding molecules of the description or fragments thereof.

The terms "host cell", "host cell line," and "host cell culture" are used interchangeably and refer to cells into which exogenous nucleic acid has been introduced, including the progeny of such cells. Host cells include "transformants" and "transformed cells," which include the primary transformed cell and progeny derived therefrom without regard to the number of passages.

Progeny may not be completely identical in nucleic acid content to a parent cell, but may contain mutations. Mutant progeny that have the same function or biological activity as ed or selected for in the originally transformed cell are included . A host cell is any type of cellular system that can be used to te the bispecific antigen binding les of the present description. Host cells include cultured cells, e.g. mammalian cultured cells, such as CHO cells, BHK cells, NS0 cells, SP2/0 cells, YO myeloma cells, P3X63 mouse myeloma cells, PER cells, PER.C6 cells or hybridoma cells, yeast cells, insect cells, and plant cells, to name only a few, but also cells comprised within a transgenic animal, transgenic plant or cultured plant or animal tissue.

An “activating Fc receptor” is an Fc receptor that following engagement by an Fc domain of an antibody elicits signaling events that stimulate the receptor-bearing cell to perform effector functions. Human activating Fc receptors include FcγRIIIa (CD16a), FcγRI (CD64), FcγRIIa (CD32), and FcαRI (CD89).

Antibody-dependent ediated cytotoxicity (ADCC) is an immune mechanism leading to the lysis of antibody-coated target cells by immune effector cells. The target cells are cells to which antibodies or derivatives thereof comprising an Fc region specifically bind, generally via the protein part that is N-terminal to the Fc . As used herein, the term “reduced ADCC” is defined as either a reduction in the number of target cells that are lysed in a given time, at a given concentration of dy in the medium surrounding the target cells, by the mechanism of ADCC defined above, and/or an increase in the concentration of antibody in the medium surrounding the target cells, required to e the lysis of a given number of target cells in a given time, by the mechanism of ADCC. The reduction in ADCC is relative to the ADCC mediated by the same antibody produced by the same type of host cells, using the same standard production, cation, formulation and storage methods (which are known to those skilled in the art), but that has not been engineered. For example the reduction in ADCC mediated by an antibody sing in its Fc domain an amino acid substitution that reduces ADCC, is relative to the ADCC mediated by the same dy without this amino acid substitution in the Fc . Suitable assays to e ADCC are well known in the art (see e.g. PCT publication no. or PCT publication no. ).

An "effective amount" of an agent refers to the amount that is necessary to result in a physiological change in the cell or tissue to which it is stered.

A "therapeutically effective amount" of an agent, e.g. a pharmaceutical composition, refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic or prophylactic result. A therapeutically ive amount of an agent for example eliminates, decreases, delays, minimizes or prevents adverse effects of a disease.

An idual” or “subject” is a mammal. Mammals include, but are not d to, domesticated animals (e.g. cows, sheep, cats, dogs, and horses), primates (e.g. humans and non- human primates such as monkeys), rabbits, and rodents (e.g. mice and rats). Particularly, the individual or subject is a human.

The term "pharmaceutical composition" refers to a preparation which is in such form as to permit the biological activity of an active ient contained therein to be effective, and which contains no onal components which are unacceptably toxic to a subject to which the formulation would be administered.

A “pharmaceutically acceptable carrier” refers to an ingredient in a pharmaceutical composition, other than an active ingredient, which is ic to a subject. A ceutically acceptable carrier includes, but is not limited to, a buffer, excipient, stabilizer, or preservative.

As used herein, “treatment” (and tical variations f such as “treat” or “treating”) refers to clinical intervention in an attempt to alter the natural course of a disease in the dual being treated, and can be performed either for prophylaxis or during the course of al pathology. Desirable effects of treatment include, but are not limited to, preventing occurrence or recurrence of disease, alleviation of symptoms, diminishment of any direct or indirect pathological consequences of the disease, preventing metastasis, decreasing the rate of disease progression, amelioration or palliation of the disease state, and remission or improved prognosis. In some embodiments, T cell activating bispecific antigen binding molecules of the description are used to delay development of a disease or to slow the ssion of a disease.

The term “package ” is used to refer to ctions arily included in commercial packages of eutic products, that contain information about the indications, usage, dosage, stration, combination therapy, contraindications and/or warnings concerning the use of such therapeutic products.

The term “comprising” as used in this specification and claims means “consisting at least in part of”. When interpreting statements in this specification, and claims which include the term “comprising”, it is to be tood that other features that are additional to the features prefaced by this term in each statement or claim may also be present. Related terms such as “comprise” and “comprised” are to be interpreted in similar manner.

Detailed Description of the Embodiments The description includes a T cell activating bispecific antigen binding molecule with favorable properties for therapeutic application, in particular with improved produceability (e.g. with respect to purity, . The amino acid substitutions in Fab molecules comprised in the T cell activating bispecific n binding molecules of the description are particularly efficient in reducing mispairing of light chains with tching heavy chains (Bence-Jones-type side products), which can occur in the production of Fab-based bi-/multispecific antigen binding molecules with a VH/VL exchange in one (or more, in case of molecules comprising more than two antigen-binding Fab molecules) of their binding arms (see also PCT application no. , particularly the examples therein, incorporated herein by reference in its entirety).

In a first embodiment the ption includes a T cell activating bispecific antigen binding molecule comprising (a) a first Fab molecule which specifically binds to a first antigen (b) a second Fab le which specifically binds to a second antigen, and wherein the variable domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other, wherein the first antigen is an activating T cell antigen and the second antigen is a target cell antigen, or the first antigen is a target cell antigen and the second antigen is an activating T cell n; and wherein i) in the nt domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by a positively charged amino acid (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 or the amino acid at position 213 is tuted by a negatively charged amino acid (numbering according to Kabat EU index); or ii) in the constant domain CL of the second Fab molecule under b) the amino acid at position 124 is substituted by a positively charged amino acid (numbering ing to Kabat), and wherein in the constant domain CH1 of the second Fab molecule under b) the amino acid at position 147 or the amino acid at position 213 is substituted by a negatively d amino acid (numbering according to Kabat EU index).

According to the ption, the T cell activating bispecific antigen binding molecule does not comprise both cations mentioned under i) and ii). The constant domains CL and CH1 of the second Fab molecule are not replaced by each other (i.e. remain unexchanged).

In one ment of the T cell activating bispecific antigen binding molecule according to the description, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is tuted ndently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 or the amino acid at position 213 is tuted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In a further embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In a particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at on 124 is substituted independently by lysine (K), arginine (R) or ine (H) (numbering according to Kabat) (in one preferred embodiment ndently by lysine (K) or arginine (R)) and the amino acid at position 123 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index) and the amino acid at position 213 is tuted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).

In a more particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by lysine (K) ring according to Kabat) and the amino acid at position 123 is substituted by lysine (K) or arginine (R) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted by glutamic acid (E) ring according to Kabat EU index) and the amino acid at position 213 is tuted by glutamic acid (E) (numbering ing to Kabat EU index).

In an even more particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by arginine (R) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at on 147 is tuted by glutamic acid (E) ring according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index).

In particular embodiments, the constant domain CL of the first Fab molecule under a) is of kappa isotype.

Alternatively, the amino acid substitutions according to the above embodiments may be made in the constant domain CL and the constant domain CH1 of the second Fab molecule under b) instead of in the constant domain CL and the constant domain CH1 of the first Fab molecule under a). In particular such embodiments, the constant domain CL of the second Fab molecule under b) is of kappa isotype.

The T cell activating bispecific antigen binding molecule according to the description may further comprise a third Fab molecule which specifically binds to the first antigen. In particular embodiments, said third Fab le is identical to the first Fab molecule under a). In these ments, the amino acid substitutions according to the above embodiments will be made in the constant domain CL and the constant domain CH1 of each of the first Fab molecule and the third Fab molecule. Alternatively, the amino acid substitutions according to the above embodiments may be made in the constant domain CL and the constant domain CH1 of the second Fab molecule under b), but not in the constant domain CL and the constant domain CH1 of the first Fab molecule and the third Fab molecule.

In particular embodiments, the T cell activating bispecific antigen binding molecule according to the description further comprises an Fc domain composed of a first and a second subunit e of stable association.

T cell activating bispecific antigen binding molecule formats The components of the T cell activating bispecific antigen binding molecule can be fused to each other in a y of configurations. Exemplary configurations are depicted in Figure 1.

In ular embodiments, the T cell activating ific antigen binding molecule ses an Fc domain composed of a first and a second subunit capable of stable association.

In some embodiments, the second Fab le is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first or the second subunit of the Fc domain.

In one such embodiment, the first Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. In a specific such embodiment, the T cell ting bispecific antigen binding molecule essentially consists of the first and the second Fab molecule, the Fc domain composed of a first and a second subunit, and optionally one or more peptide linkers, wherein the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, and the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first or the second t of the Fc domain. Such a uration is schematically depicted in Figures 1G and 1K. Optionally, the Fab light chain of the first Fab molecule and the Fab light chain of the second Fab molecule may additionally be fused to each other.

In another such ment, the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first or second subunit of the Fc domain. In a specific such embodiment, the T cell activating bispecific antigen binding molecule ially consists of the first and the second Fab molecule, the Fc domain composed of a first and a second subunit, and optionally one or more peptide linkers, wherein the first and the second Fab molecule are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain. Such a configuration is schematically depicted in Figures 1A and 1D. The first and the second Fab molecule may be fused to the Fc domain directly or through a peptide linker. In a particular embodiment the first and the second Fab molecule are each fused to the Fc domain through an immunoglobulin hinge region. In a specific embodiment, the immunoglobulin hinge region is a human IgG1 hinge region, particularly where the Fc domain is an IgG1 Fc .

In other embodiments, the first Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the first or second subunit of the Fc domain.

In one such embodiment, the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. In a specific such ment, the T cell activating bispecific antigen binding molecule essentially consists of the first and the second Fab molecule, the Fc domain composed of a first and a second subunit, and optionally one or more peptide s, wherein the second Fab molecule is fused at the C- terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab le, and the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N- terminus of the first or the second subunit of the Fc domain. Such a configuration is tically depicted in Figures 1H and 1L. Optionally, the Fab light chain of the first Fab molecule and the Fab light chain of the second Fab molecule may additionally be fused to each other.

The Fab molecules may be fused to the Fc domain or to each other directly or through a peptide linker, comprising one or more amino acids, typically about 2-20 amino acids. Peptide linkers are known in the art and are described herein. Suitable, non-immunogenic peptide linkers include, for example, , (SG4)n, (G4S)n or G4(SG4)n peptide linkers. “n” is generally an r from 1 to 10, typically from 2 to 4. In one embodiment said peptide linker has a length of at least 5 amino acids, in one embodiment a length of 5 to 100, in a further embodiment of 10 to 50 amino acids. In one embodiment said peptide linker is (GxS)n or (GxS)nGm with ine, S=serine, and (x=3, n= 3, 4, 5 or 6, and m=0, 1, 2 or 3) or (x=4, n=2, 3, 4 or 5 and m= 0, 1, 2 or 3), in one embodiment x=4 and n=2 or 3, in a further embodiment x=4 and n=2. In one embodiment said peptide linker is (G4S)2. A ularly suitable peptide linker for fusing the Fab light chains of the first and the second Fab molecule to each other is (G4S)2. An exemplary peptide linker le for connecting the Fab heavy chains of the first and the second Fab fragments comprises the sequence (D)-(G4S)2 (SEQ ID NOs 11 and 12). Additionally, linkers may se (a portion of) an immunoglobulin hinge . Particularly where a Fab molecule is fused to the N-terminus of an Fc domain subunit, it may be fused via an globulin hinge region or a portion thereof, with or without an additional peptide .

A T cell activating bispecific antigen g molecule with a single antigen binding moiety (such as a Fab molecule) e of specific binding to a target cell antigen (for example as shown in Figure 1A, D, G, H, K, L) is useful, particularly in cases where internalization of the target cell antigen is to be expected following binding of a high affinity antigen binding moiety.

In such cases, the presence of more than one antigen g moiety specific for the target cell antigen may e internalization of the target cell antigen, thereby reducing its availablity.

In many other cases, however, it will be advantageous to have a T cell activating bispecific antigen binding molecule comprising two or more antigen binding moieties (such as Fab moelcules) specific for a target cell antigen (see examples shown in Figure 1B, 1C, 1E, 1F, 1I, 1J. 1M or 1N), for example to optimize targeting to the target site or to allow crosslinking of target cell antigens.

Accordingly, in particular embodiments, the T cell activating bispecific antigen binding molecule of the description further comprises a third Fab le which specifically binds to the first antigen. The first antigen preferably is the target cell antigen. In one embodiment, the third Fab molecule is a conventional Fab le. In one embodiment, the third Fab molecule is identical to the first Fab molecule (i.e. the first and the third Fab molecule comprise the same heavy and light chain amino acid sequences and have the same arrangement of domains (i.e. conventional or crossover)). In a ular embodiment, the second Fab le specifically binds to an activating T cell antigen, particularly CD3, and the first and third Fab molecule specifically bind to a target cell n.

In alternative embodiments, the T cell activating bispecific antigen binding molecule of the ption further comprises a third Fab molecule which ically binds to the second antigen.

In these embodiments, the second antigen preferably is the target cell antigen. In one such embodiment, the third Fab molecule is a crossover Fab molecule (a Fab molecule wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / replaced by each other). In one such embodiment, the third Fab le is identical to the second Fab molecule (i.e. the second and the third Fab molecule comprise the same heavy and light chain amino acid sequences and have the same arrangement of domains (i.e. conventional or crossover)). In one such embodiment, the first Fab molecule specifically binds to an activating T cell antigen, particularly CD3, and the second and third Fab molecule specifically bind to a target cell antigen.

In one embodiment, the third Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first or second subunit of the Fc domain.

In a particular embodiment, the second and the third Fab molecule are each fused at the C- terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain, and the first Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. In a specific such embodiment, the T cell activating bispecific antigen binding le essentially consists of the first, the second and the third Fab molecule, the Fc domain composed of a first and a second subunit, and optionally one or more peptide linkers, wherein the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, and the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the first t of the Fc domain, and wherein the third Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the second subunit of the Fc domain. Such a configuration is schematically depicted in Figure 1B and 1E (particular embodiments, wherein the third Fab molecule is a conventional Fab molecule and preferably identical to the first Fab molecule), and Figure 1I and 1M (alternative embodiments, wherein the third Fab le is a crossover Fab molecule and preferably identical to the second Fab le). The second and the third Fab molecule may be fused to the Fc domain ly or through a peptide linker. In a particular embodiment the second and the third Fab le are each fused to the Fc domain through an immunoglobulin hinge region. In a specific embodiment, the immunoglobulin hinge region is a human IgG1 hinge region, particularly where the Fc domain is an IgG1 Fc domain.

Optionally, the Fab light chain of the first Fab le and the Fab light chain of the second Fab le may additionally be fused to each other.

In another ment, the first and the third Fab molecule are each fused at the C-terminus of the Fab heavy chain to the inus of one of the subunits of the Fc domain, and the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. In a specific such embodiment, the T cell activating bispecific antigen binding molecule essentially consists of the first, the second and the third Fab molecule, the Fc domain composed of a first and a second subunit, and optionally one or more peptide linkers, wherein the second Fab le is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule, and the first Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the first subunit of the Fc domain, and wherein the third Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the second subunit of the Fc domain. Such a configuration is schematically depicted in Figure 1C and 1F (particular embodiments, wherein the third Fab molecule is a conventional Fab le and preferably identical to the first Fab molecule) and in Figure 1J and 1N (alternative embodiments, wherein the third Fab molecule is a crossover Fab molecule and preferably identical to the second Fab molecule). The first and the third Fab le may be fused to the Fc domain directly or h a peptide linker. In a particular embodiment the first and the third Fab molecule are each fused to the Fc domain through an immunoglobulin hinge region. In a specific embodiment, the immunoglobulin hinge region is a human IgG1 hinge region, particularly where the Fc domain is an IgG1 Fc domain. Optionally, the Fab light chain of the first Fab molecule and the Fab light chain of the second Fab molecule may additionally be fused to each other.

In configurations of the T cell activating bispecific antigen binding le wherein a Fab molecule is fused at the C-terminus of the Fab heavy chain to the inus of each of the subunits of the Fc domain h an immunoglobulin hinge regions, the two Fab molecules, the hinge regions and the Fc domain essentially form an immunoglobulin molecule. In a particular embodiment the immunoglobulin molecule is an IgG class immunoglobulin. In an even more particular embodiment the immunoglobulin is an IgG1 subclass immunoglobulin. In another embodiment the immunoglobulin is an IgG4 subclass immunoglobulin. In a further particular embodiment the immunoglobulin is a human immunoglobulin. In other embodiments the immunoglobulin is a ic immunoglobulin or a humanized immunoglobulin.

In some of the T cell activating bispecific antigen g molecule of the description, the Fab light chain of the first Fab molecule and the Fab light chain of the second Fab molecule are fused to each other, optionally via a peptide lnker. Depending on the configuration of the first and the second Fab molecule, the Fab light chain of the first Fab molecule may be fused at its C- terminus to the N-terminus of the Fab light chain of the second Fab molecule, or the Fab light chain of the second Fab molecule may be fused at its C-terminus to the N-terminus of the Fab light chain of the first Fab le. Fusion of the Fab light chains of the first and the second Fab molecule further s mispairing of unmatched Fab heavy and light chains, and also s the number of plasmids needed for expression of some of the T cell activating bispecific antigen binding molecules of the description.

In certain embodiments the T cell activating bispecific antigen binding molecule according to the description comprises a polypeptide wherein the Fab light chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab le comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable region), which in turn shares a carboxy-terminal peptide bond with an Fc domain subunit -CH1(2)- CH2-CH3(-CH4)), and a ptide wherein the Fab heavy chain of the first Fab molecule shares a carboxy-terminal peptide bond with an Fc domain subunit (VH(1)-CH1(1)-CH2-CH3(- CH4)). In some embodiments the T cell activating bispecific antigen binding molecule further comprises a polypeptide wherein the Fab heavy chain variable region of the second Fab molecule shares a carboxy-terminal e bond with the Fab light chain constant region of the second Fab molecule (VH(2)-CL(2)) and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)). In certain embodiments the polypeptides are covalently linked, e.g., by a disulfide bond.

In some embodiments, the T cell activating bispecific antigen binding molecule comprises a polypeptide n the Fab light chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab le (i.e. the second Fab le comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain le region), which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain of the first Fab molecule, which in turn shares a carboxy-terminal peptide bond with an Fc domain subunit -CH1(2)-VH(1)-CH1(1)- CH2-CH3(-CH4)). In other embodiments, the T cell activating bispecific antigen binding molecule ses a polypeptide wherein the Fab heavy chain of the first Fab molecule shares a carboxy-terminal e bond with the Fab light chain le region of the second Fab molecule which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable region), which in turn shares a carboxy-terminal peptide bond with an Fc domain subunit (VH(1)- CH1(1)-VL(2)-CH1(2)-CH2-CH3(-CH4)).

In some of these embodiments the T cell ting bispecific antigen binding molecule further comprises a crossover Fab light chain polypeptide of the second Fab le, wherein the Fab heavy chain le region of the second Fab le shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab le (VH(2)-CL(2)), and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)). In others of these embodiments the T cell activating bispecific antigen binding molecule further comprises a polypeptide n the Fab light chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule which in turn shares a carboxy-terminal peptide bond with the Fab light chain polypeptide of the first Fab molecule (VL(2)-CH1(2)-VL(1)-CL(1)), or a ptide wherein the Fab light chain polypeptide of the first Fab molecule shares a carboxy-terminal peptide bond with the Fab heavy chain variable region of the second Fab molecule which in turn shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab molecule (VL(1)-CL(1)-VH(2)-CL(2)), as appropriate.

The T cell activating bispecific antigen binding molecule according to these embodiments may further comprise (i) an Fc domain subunit polypeptide (CH2-CH3(-CH4)), or (ii) a polypeptide wherein the Fab heavy chain of a third Fab molecule shares a carboxy-terminal peptide bond with an Fc domain subunit (VH(3)-CH1(3)-CH2-CH3(-CH4)) and the Fab light chain polypeptide of a third Fab molecule (VL(3)-CL(3)). In certain embodiments the ptides are covalently , e.g., by a disulfide bond.

In some embodiments, the first Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. In certain such embodiments, the T cell activating bispecific antigen binding molecule does not comprise an Fc domain. In certain embodiments, the T cell activating bispecific n binding molecule essentially consists of the first and the second Fab molecule, and optionally one or more peptide linkers, wherein the first Fab le is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. Such a configuration is schematically depicted in Figures 1O and 1S.

In other embodiments, the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. In certain such ments, the T cell activating bispecific n binding molecule does not comprise an Fc domain. In certain embodiments, the T cell activating bispecific antigen binding molecule essentially consists of the first and the second Fab molecule, and optionally one or more peptide linkers, wherein the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. Such a configuration is schematically depicted in Figures 1P and 1T.

In some embodiments, the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, and the T cell activating ific antigen binding le further comprises a third Fab molecule, wherein said third Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. In particular such embodiments, said third Fab molecule is a conventional Fab molecule. In other such embodiments, said third Fab molecule is a crossover Fab molecule as described herein, i.e. a Fab molecule wherein the variable s VH and VL of the Fab heavy and light chains are exchanged / replaced by each other. In certain such embodiments, the T cell activating bispecific antigen binding molecule essentially consists of the first, the second and the third Fab molecule, and ally one or more peptide linkers, n the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, and the third Fab molecule is fused at the C- terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule. Such a configuration is tically depicted in Figure 1Q and 1U (particular embodiments, wherein the third Fab le is a conventional Fab molecule and preferably identical to the first Fab molecule).

In some embodiments, the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, and the T cell activating bispecific n binding molecule further comprises a third Fab molecule, wherein said third Fab molecule is fused at the N-terminus of the Fab heavy chain to the C-terminus of the Fab heavy chain of the second Fab molecule. In particular such embodiments, said third Fab le is a crossover Fab molecule as described herein, i.e. a Fab molecule wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / ed by each other. In other such embodiments, said third Fab molecule is a tional Fab molecule. In certain such embodiments, the T cell activating bispecific antigen binding molecule essentially consists of the first, the second and the third Fab molecule, and optionally one or more peptide linkers, wherein the first Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule, and the third Fab le is fused at the N-terminus of the Fab heavy chain to the C-terminus of the Fab heavy chain of the second Fab molecule. Such a configuration is schematically depicted in Figure 1W and 1Y (particular ments, wherein the third Fab molecule is a crossover Fab molecule and preferably identical to the second Fab molecule).

In some embodiments, the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule, and the T cell activating bispecific antigen binding molecule further ses a third Fab molecule, wherein said third Fab molecule is fused at the N-terminus of the Fab heavy chain to the C-terminus of the Fab heavy chain of the first Fab molecule. In particular such embodiments, said third Fab molecule is a conventional Fab molecule. In other such embodiments, said third Fab molecule is a crossover Fab le as described , i.e. a Fab molecule wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / ed by each other. In certain such embodiments, the T cell activating bispecific antigen binding le essentially consists of the first, the second and the third Fab molecule, and optionally one or more peptide linkers, wherein the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N- us of the Fab heavy chain of the first Fab molecule, and the third Fab molecule is fused at the N-terminus of the Fab heavy chain to the C-terminus of the Fab heavy chain of the first Fab molecule. Such a configuration is schematically depicted in Figure 1R and 1V (particular ments, wherein the third Fab molecule is a conventional Fab molecule and preferably identical to the first Fab molecule).

In some embodiments, the second Fab le is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule, and the T cell activating bispecific antigen binding molecule further comprises a third Fab molecule, wherein said third Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. In particular such embodiments, said third Fab molecule is a crossover Fab molecule as described herein, i.e. a Fab le wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / replaced by each other. In other such embodiments, said third Fab molecule is a conventional Fab molecule. In certain such ments, the T cell activating bispecific antigen binding molecule essentially consists of the first, the second and the third Fab molecule, and ally one or more peptide linkers, wherein the second Fab molecule is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule, and the third Fab molecule is fused at the inus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the second Fab molecule. Such a configuration is schematically depicted in Figure 1X and 1Z cular embodiments, n the third Fab molecule is a crossover Fab molecule and preferably identical to the first Fab molecule).

In certain embodiments the T cell activating bispecific antigen binding molecule ing to the description comprises a polypeptide wherein the Fab heavy chain of the first Fab molecule shares a carboxy-terminal e bond with the Fab light chain variable region of the second Fab molecule, which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable region) (VH(1)-CH1(1)-VL(2)-CH1(2)). In some embodiments the T cell activating bispecific n binding molecule further comprises a polypeptide wherein the Fab heavy chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab molecule -CL(2)) and the Fab light chain ptide of the first Fab molecule (VL(1)-CL(1)).

In certain embodiments the T cell activating bispecific antigen binding molecule according to the description comprises a polypeptide wherein the Fab light chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain le ), which in turn shares a carboxy-terminal e bond with the Fab heavy chain of the first Fab molecule (VL(2)-CH1(2)-VH(1)-CH1(1)). In some embodiments the T cell activating bispecific antigen binding le further comprises a polypeptide wherein the Fab heavy chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab molecule (VH(2)-CL(2)) and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)).

In certain embodiments the T cell activating bispecific antigen g molecule according to the description comprises a polypeptide wherein the Fab heavy chain of a third Fab molecule shares a carboxy-terminal e bond with the Fab heavy chain of the first Fab molecule, which in turn shares a carboxy-terminal peptide bond with the Fab light chain variable region of the second Fab molecule, which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab le comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable ) (VH(3)-CH1(3)-VH(1)-CH1(1)-VL(2)-CH1(2)). In some embodiments the T cell activating bispecific antigen binding molecule further comprises a polypeptide wherein the Fab heavy chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab molecule (VH(2)-CL(2)) and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)). In some embodiments the T cell activating ific antigen binding molecule further comprises the Fab light chain polypeptide of a third Fab molecule (VL(3)-CL(3)).

In certain embodiments the T cell activating bispecific antigen binding molecule according to the description comprises a polypeptide wherein the Fab light chain variable region of the second Fab molecule shares a y-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is ed by a light chain variable region), which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain of the first Fab molecule, which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain of a third Fab molecule (VL(2)-CH1(2)-VH(1)-CH1(1)-VH(3)-CH1(3)). In some embodiments the T cell activating bispecific antigen binding molecule r comprises a polypeptide wherein the Fab heavy chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab molecule (VH(2)-CL(2)) and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)). In some embodiments the T cell activating bispecific antigen binding molecule further comprises the Fab light chain ptide of a third Fab le (VL(3)-CL(3)).

In certain ments the T cell ting ific antigen binding molecule according to the description comprises a polypeptide wherein the Fab heavy chain of the first Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain variable region of the second Fab molecule, which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain le region), which in turn shares a carboxy-terminal peptide bond with the Fab light chain variable region of a third Fab molecule, which in turn shares a carboxy-terminal e bond with the Fab heavy chain constant region of a third Fab molecule (i.e. the third Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable ) (VH(1)-CH1(1)-VL(2)-CH1(2)-VL(3)-CH1(3)). In some embodiments the T cell activating bispecific antigen binding molecule further comprises a polypeptide wherein the Fab heavy chain variable region of the second Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of the second Fab molecule (VH(2)-CL(2)) and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)). In some embodiments the T cell activating bispecific antigen binding molecule further comprises a polypeptide wherein the Fab heavy chain variable region of a third Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of a third Fab molecule (VH(3)-CL(3)).

In certain embodiments the T cell activating bispecific antigen binding molecule according to the description comprises a polypeptide wherein the Fab light chain variable region of a third Fab le shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of a third Fab molecule (i.e. the third Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable region), which in turn shares a y-terminal peptide bond with the Fab light chain variable region of the second Fab molecule, which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain constant region of the second Fab molecule (i.e. the second Fab molecule comprises a crossover Fab heavy chain, wherein the heavy chain variable region is replaced by a light chain variable region), which in turn shares a carboxy-terminal peptide bond with the Fab heavy chain of the first Fab molecule (VL(3)-CH1(3)-VL(2)-CH1(2)-VH(1)-CH1(1)). In some embodiments the T cell activating bispecific n binding molecule further comprises a polypeptide wherein the Fab heavy chain le region of the second Fab le shares a carboxy-terminal peptide bond with the Fab light chain nt region of the second Fab le (VH(2)-CL(2)) and the Fab light chain polypeptide of the first Fab molecule (VL(1)-CL(1)). In some embodiments the T cell activating bispecific antigen binding molecule further comprises a polypeptide wherein the Fab heavy chain variable region of a third Fab molecule shares a carboxy-terminal peptide bond with the Fab light chain constant region of a third Fab molecule (VH(3)-CL(3)).

According to any of the above embodiments, components of the T cell activating ific antigen binding molecule (e.g. Fab les, Fc domain) may be fused directly or h various linkers, particularly peptide linkers comprising one or more amino acids, lly about 2-20 amino acids, that are described herein or are known in the art. Suitable, non-immunogenic peptide linkers include, for example, (G4S)n, , (G4S)n or G4(SG4)n peptide linkers, wherein n is generally an integer from 1 to 10, typically from 2 to 4.

Fc domain The Fc domain of the T cell activating bispecific antigen binding molecule consists of a pair of polypeptide chains comprising heavy chain domains of an immunoglobulin molecule. For example, the Fc domain of an immunoglobulin G (IgG) molecule is a dimer, each subunit of which comprises the CH2 and CH3 IgG heavy chain constant domains. The two subunits of the Fc domain are capable of stable association with each other. In one embodiment the T cell activating ific antigen binding molecule of the description comprises not more than one Fc domain.

In one embodiment according the description the Fc domain of the T cell activating ific antigen binding molecule is an IgG Fc domain. In a particular ment the Fc domain is an IgG1 Fc domain. In another embodiment the Fc domain is an IgG4 Fc . In a more specific embodiment, the Fc domain is an IgG4 Fc domain comprising an amino acid substitution at position S228 (Kabat numbering), particularly the amino acid substitution S228P. This amino acid substitution reduces in vivo Fab arm exchange of IgG4 antibodies (see rauch et al., Drug Metabolism and Disposition 38, 84-91 (2010)). In a further particular embodiment the Fc domain is human. An exemplary sequence of a human IgG1 Fc region is given in SEQ ID NO: Fc domain modifications promoting heterodimerization T cell activating bispecific antigen binding molecules according to the description comprise different Fab molecules, fused to one or the other of the two subunits of the Fc domain, thus the two subunits of the Fc domain are typically comprised in two non-identical polypeptide .

Recombinant co-expression of these polypeptides and subsequent dimerization leads to several possible combinations of the two polypeptides. To e the yield and purity of T cell activating bispecific antigen binding les in inant production, it will thus be advantageous to introduce in the Fc domain of the T cell activating bispecific antigen binding molecule a modification promoting the association of the desired polypeptides.

Accordingly, in particular ments the Fc domain of the T cell activating bispecific antigen binding molecule according to the ption comprises a modification promoting the association of the first and the second t of the Fc domain. The site of most extensive protein-protein ction between the two subunits of a human IgG Fc domain is in the CH3 domain of the Fc domain. Thus, in one embodiment said modification is in the CH3 domain of the Fc domain.

There exist several approaches for modifications in the CH3 domain of the Fc domain in order to enforce heterodimerization, which are well bed e.g. in WO 96/27011, WO 98/050431, EP 1870459, , , , , , , WO 2012058768, WO 7954, WO 2013096291.

Typically, in all such ches the CH3 domain of the first subunit of the Fc domain and the CH3 domain of the second subunit of the Fc domain are both engineered in a complementary manner so that each CH3 domain (or the heavy chain sing it) can no longer homodimerize with itself but is forced to heterodimerize with the complementarily engineered other CH3 domain (so that the first and second CH3 domain heterodimerize and no homdimers between the two first or the two second CH3 domains are formed). These different approaches for improved heavy chain heterodimerization are contemplated as different alternatives in combination with the heavy-light chain modifications (VH and VL exchange/replacement in one binding arm and the introduction of substitutions of charged amino acids with opposite charges in the CH1/CL interface) in the T cell activating bispecific antigen binding molecule according to the ption which reduce light chain mispairing and Bence Jones-type side products.

In a specific embodiment said modification promoting the association of the first and the second subunit of the Fc domain is a so-called “knob-into-hole” modification, sing a “knob” modification in one of the two subunits of the Fc domain and a “hole” modification in the other one of the two subunits of the Fc .

The knob-into-hole technology is described e.g. in US 5,731,168; US 936; Ridgway et al., Prot Eng 9, 617-621 (1996) and Carter, J Immunol Meth 248, 7-15 (2001). Generally, the method es introducing a protuberance (“knob”) at the interface of a first polypeptide and a corresponding cavity (“hole”) in the interface of a second polypeptide, such that the protuberance can be positioned in the cavity so as to promote heterodimer ion and hinder homodimer formation. erances are constructed by replacing small amino acid side chains from the interface of the first polypeptide with larger side chains (e.g. ne or tryptophan).

Compensatory es of identical or similar size to the protuberances are created in the interface of the second polypeptide by replacing large amino acid side chains with smaller ones (e.g. alanine or threonine).

Accordingly, in a particular embodiment, in the CH3 domain of the first subunit of the Fc domain of the T cell activating bispecific antigen binding molecule an amino acid residue is replaced with an amino acid residue having a larger side chain volume, thereby generating a erance within the CH3 domain of the first subunit which is positionable in a cavity within the CH3 domain of the second subunit, and in the CH3 domain of the second subunit of the Fc domain an amino acid residue is replaced with an amino acid residue having a r side chain volume, thereby generating a cavity within the CH3 domain of the second subunit within which the protuberance within the CH3 domain of the first subunit is positionable.

Preferably said amino acid residue having a larger side chain volume is selected from the group consisting of arginine (R), phenylalanine (F), tyrosine (Y), and tryptophan (W).

Preferably said amino acid residue having a smaller side chain volume is selected from the group consisting of alanine (A), serine (S), threonine (T), and valine (V).

The protuberance and cavity can be made by altering the nucleic acid encoding the polypeptides, e.g. by site-specific mutagenesis, or by peptide synthesis.

In a specific embodiment, in the CH3 domain of the first subunit of the Fc domain (the “knobs” subunit) the threonine residue at position 366 is replaced with a tryptophan residue (T366W), and in the CH3 domain of the second subunit of the Fc domain (the “hole” t) the tyrosine e at position 407 is replaced with a valine residue (Y407V). In one embodiment, in the second subunit of the Fc domain additionally the threonine residue at on 366 is replaced with a serine residue ) and the leucine residue at position 368 is replaced with an alanine residue (L368A) rings ing to Kabat EU index).

In yet a further embodiment, in the first subunit of the Fc domain additionally the serine residue at position 354 is ed with a cysteine residue (S354C) or the glutamic acid residue at position 356 is replaced with a cysteine residue (E356C), and in the second subunit of the Fc domain additionally the tyrosine residue at on 349 is replaced by a cysteine residue (Y349C) (numberings according to Kabat EU index). Introduction of these two cysteine residues results in formation of a disulfide bridge between the two subunits of the Fc domain, r stabilizing the dimer (Carter, J l Methods 248, 7-15 ).

In a particular ment, the first subunit of the Fc domain comprises amino acid substitutions S354C and T366W, and the second subunit of the Fc domain comprises amino acid tutions Y349C, T366S, L368A and Y407V (numbering according to Kabat EU index).

In a particular embodiment the Fab molecule which specifically binds an activating T cell antigen is fused (optionally via a Fab molecule which specifically binds to a target cell antigen) to the first subunit of the Fc domain (comprising the “knob” modification). Without wishing to be bound by theory, fusion of the Fab le which specifically binds an activating T cell antigen to the knob-containing subunit of the Fc domain will (further) minimize the generation of antigen g molecules comprising two Fab molecules which bind to an activating T cell antigen (steric clash of two knob-containing polypeptides).

Other techniques of dification for enforcing the heterodimerization are contemplated as alternatives according to the description and are described e.g. in WO 96/27011, WO 98/050431, EP 1870459, , , WO 89004, , , , , WO 57954, .

In one embodiment the heterodimerization approach described in EP 1870459 A1, is used alternatively. This approach is based on the introduction of charged amino acids with opposite s at specific amino acid positions in the CH3/CH3 domain interface between the two subunits of the Fc . One preferred embodiment for the T cell activating bispecific antigen binding molecule of the description are amino acid mutations R409D; K370E in one of the two CH3 domains (of the Fc domain) and amino acid ons D399K; E357K in the other one of the CH3 domains of the Fc domain ring according to Kabat EU index).

In another embodiment the T cell activating bispecific antigen binding molecule of the description comprises amino acid mutation T366W in the CH3 domain of the first subunit of the Fc domain and amino acid ons T366S, L368A, Y407V in the CH3 domain of the second subunit of the Fc domain, and additionally amino acid mutations R409D; K370E in the CH3 domain of the first subunit of the Fc domain and amino acid mutations D399K; E357K in the CH3 domain of the second subunit of the Fc domain (numberings according to Kabat EU index).

In another embodiment T cell activating bispecific antigen binding molecule of the description comprises amino acid mutations S354C, T366W in the CH3 domain of the first subunit of the Fc domain and amino acid mutations Y349C, T366S, L368A, Y407V in the CH3 domain of the second subunit of the Fc , or said T cell activating bispecific antigen binding molecule comprises amino acid mutations Y349C, T366W in the CH3 domain of the first subunit of the Fc domain and amino acid mutations S354C, T366S, L368A, Y407V in the CH3 domains of the second t of the Fc domain and additionally amino acid mutations R409D; K370E in the CH3 domain of the first subunit of the Fc domain and amino acid mutations D399K; E357K in the CH3 domain of the second subunit of the Fc domain (all numberings ing to Kabat EU index).

In one embodiment the heterodimerization approach described in is used alternatively. In one embodiment a first CH3 domain comprises amino acid mutation T366K and a second CH3 domain ses amino acid mutation L351D (numberings according to Kabat EU index). In a further embodiment the first CH3 domain comprises further amino acid mutation L351K. In a further embodiment the second CH3 domain comprises further an amino acid mutation selected from Y349E, Y349D and L368E rably L368E) (numberings according to Kabat EU index).

In one embodiment the heterodimerization approach described in is used atively. In one embodiment a first CH3 domain comprises amino acid mutations L351Y, Y407A and a second CH3 domain comprises amino acid mutations T366A, K409F. In a further embodiment the second CH3 domain comprises a further amino acid mutation at position T411, D399, S400, F405, N390, or K392, e.g. selected from a) T411N, T411R, T411Q, T411K, T411D, T411E or T411W, b) D399R, D399W, D399Y or D399K, c) S400E, S400D, S400R, or S400K, d) F405I, F405M, F405T, F405S, F405V or F405W, e) N390R, N390K or N390D, f) K392V, K392M, K392R, K392L, K392F or K392E rings according to Kabat EU index).

In a further embodiment a first CH3 domain ses amino acid ons L351Y, Y407A and a second CH3 domain comprises amino acid ons T366V, K409F. In a further embodiment a first CH3 domain comprises amino acid mutation Y407A and a second CH3 domain comprises amino acid mutations T366A, K409F. In a further embodiment the second CH3 domain further comprises amino acid mutations K392E, T411E, D399R and S400R (numberings according to Kabat EU index).

In one embodiment the heterodimerization approach described in is used alternatively, e.g. with the amino acid modification at a position selected from the group consisting of 368 and 409 (numbering according to Kabat EU index).

In one embodiment the dimerization approach described in , which also uses the knobs-into-holes technology described above, is used alternatively. In one embodiment a first CH3 domain comprises amino acid mutation T366W and a second CH3 domain comprises amino acid mutation Y407A. In one embodiment a first CH3 domain comprises amino acid mutation T366Y and a second CH3 domain comprises amino acid mutation Y407T (numberings according to Kabat EU index).

In one embodiment the T cell activating bispecific antigen binding molecule or its Fc domain is of IgG2 subclass and the heterodimerization approach described in is used alternatively.

In an alternative embodiment a cation promoting association of the first and the second subunit of the Fc domain comprises a modification mediating ostatic steering effects, e.g. as bed in PCT publication . lly, this method involves replacement of one or more amino acid residues at the interface of the two Fc domain subunits by charged amino acid es so that homodimer formation becomes ostatically rable but heterodimerization electrostatically favorable. In one such embodiment a first CH3 domain comprises amino acid substitution of K392 or N392 with a negatively charged amino acid (e.g. glutamic acid (E), or aspartic acid (D), ably K392D or N392D) and a second CH3 domain comprises amino acid substitution of D399, E356, D356, or E357 with a positively charged amino acid (e.g. lysine (K) or arginine (R), preferably D399K, E356K, D356K, or E357K, and more preferably D399K and E356K). In a further embodiment the first CH3 domain further ses amino acid substitution of K409 or R409 with a negatively charged amino acid (e.g. glutamic acid (E), or aspartic acid (D), preferably K409D or R409D). In a further embodiment the first CH3 domain further or alternatively comprises amino acid substitution of K439 and/or K370 with a negatively charged amino acid (e.g. glutamic acid (E), or aspartic acid (D)) (all numberings according to Kabat EU index).

In yet a further embodiment the heterodimerization approach bed in is used alternatively. In one embodiment a first CH3 domain comprises amino acid mutations K253E, D282K, and K322D and a second CH3 domain comprises amino acid mutations D239K, E240K, and K292D (numberings according to Kabat EU index).

In still another embodiment the heterodimerization approach described in can be used alternatively.

In one embodiment, the first subunit of the Fc domain comprises amino acid substitutions K392D and K409D, and the second subunit of the Fc domain comprises amino acid substitutions D356K and D399K (numbering according to Kabat EU index).

Fc domain modifications reducing Fc receptor binding and/or effector function The Fc domain confers to the T cell activating bispecific antigen binding molecule favorable pharmacokinetic properties, including a long serum half-life which contributes to good accumulation in the target tissue and a favorable tissue-blood bution ratio. At the same time it may, however, lead to undesirable targeting of the T cell activating bispecific antigen binding le to cells expressing Fc ors rather than to the preferred n-bearing cells.

Moreover, the co-activation of Fc receptor signaling pathways may lead to ne release which, in combination with the T cell activating ties and the long half-life of the antigen g molecule, results in excessive tion of cytokine receptors and severe side effects upon systemic administration. Activation of (Fc receptor-bearing) immune cells other than T cells may even reduce efficacy of the T cell activating bispecific antigen binding molecule due to the potential destruction of T cells e.g. by NK cells.

Accordingly, in particular embodiments, the Fc domain of the T cell activating bispecific antigen binding molecules according to the description exhibits reduced binding affinity to an Fc receptor and/or reduced effector function, as compared to a native IgG1 Fc domain. In one such embodiment the Fc domain (or the T cell activating bispecific antigen binding molecule comprising said Fc domain) exhibits less than 50%, preferably less than 20%, more preferably less than 10% and most preferably less than 5% of the g ty to an Fc receptor, as compared to a native IgG1 Fc domain (or a T cell activating bispecific n binding molecule comprising a native IgG1 Fc domain), and/or less than 50%, preferably less than 20%, more preferably less than 10% and most preferably less than 5% of the effector function, as compared to a native IgG1 Fc domain domain (or a T cell activating bispecific antigen binding molecule comprising a native IgG1 Fc domain). In one embodiment, the Fc domain domain (or the T cell activating bispecific n binding molecule sing said Fc domain) does not substantially bind to an Fc receptor and/or induce effector function. In a ular embodiment the Fc receptor is an Fcγ receptor. In one embodiment the Fc or is a human Fc receptor. In one embodiment the Fc receptor is an activating Fc receptor. In a specific embodiment the Fc receptor is an activating human Fcγ receptor, more specifically human FcγRIIIa, FcγRI or FcγRIIa, most specifically human FcγRIIIa. In one embodiment the effector function is one or more ed from the group of CDC, ADCC, ADCP, and cytokine secretion. In a particular embodiment the effector function is ADCC. In one embodiment the Fc domain domain exhibits substantially similar binding ty to neonatal Fc receptor , as compared to a native IgG1 Fc domain . Substantially similar binding to FcRn is achieved when the Fc domain (or the T cell activating bispecific antigen binding molecule comprising said Fc domain) exhibits greater than about 70%, particularly greater than about 80%, more particularly greater than about 90% of the binding affinity of a native IgG1 Fc domain (or the T cell activating bispecific n binding molecule comprising a native IgG1 Fc domain) to FcRn.

In certain embodiments the Fc domain is engineered to have reduced binding affinity to an Fc receptor and/or reduced effector function, as compared to a non-engineered Fc domain. In particular ments, the Fc domain of the T cell activating ific antigen binding molecule comprises one or more amino acid mutation that reduces the binding affinity of the Fc domain to an Fc receptor and/or or function. Typically, the same one or more amino acid mutation is present in each of the two subunits of the Fc domain. In one embodiment the amino acid mutation reduces the binding affinity of the Fc domain to an Fc receptor. In one embodiment the amino acid on s the binding affinity of the Fc domain to an Fc receptor by at least , at least 5-fold, or at least 10-fold. In embodiments where there is more than one amino acid mutation that reduces the binding affinity of the Fc domain to the Fc receptor, the combination of these amino acid mutations may reduce the binding affinity of the Fc domain to an Fc or by at least 10-fold, at least 20-fold, or even at least 50-fold. In one embodiment the T cell activating ific antigen binding molecule comprising an engineered Fc domain exhibits less than 20%, ularly less than 10%, more particularly less than 5% of the binding affinity to an Fc receptor as compared to a T cell activating bispecific antigen binding molecule sing a non-engineered Fc domain. In a particular ment the Fc receptor is an Fcγ receptor. In some embodiments the Fc receptor is a human Fc receptor. In some embodiments the Fc receptor is an activating Fc receptor. In a ic embodiment the Fc receptor is an activating human Fcγ receptor, more specifically human FcγRIIIa, FcγRI or FcγRIIa, most specifically human FcγRIIIa. Preferably, binding to each of these receptors is reduced. In some embodiments binding affinity to a complement component, specifically binding affinity to C1q, is also reduced. In one embodiment binding affinity to neonatal Fc receptor (FcRn) is not reduced. Substantially r binding to FcRn, i.e. preservation of the binding affinity of the Fc domain to said receptor, is achieved when the Fc domain (or the T cell activating bispecific antigen binding molecule comprising said Fc domain) exhibits greater than about 70% of the g affinity of a non-engineered form of the Fc domain (or the T cell activating bispecific antigen binding molecule comprising said non-engineered form of the Fc domain) to FcRn. The Fc domain, or T cell activating bispecific n binding molecules of the description comprising said Fc domain, may exhibit greater than about 80% and even greater than about 90% of such affinity. In certain embodiments the Fc domain of the T cell activating bispecific antigen binding molecule is engineered to have reduced effector function, as ed to a non-engineered Fc domain. The reduced effector function can include, but is not limited to, one or more of the following: reduced complement dependent cytotoxicity (CDC), reduced antibody-dependent cell-mediated cytotoxicity , reduced antibody-dependent ar phagocytosis , reduced ne secretion, reduced immune complex-mediated n uptake by antigen-presenting cells, reduced binding to NK cells, reduced binding to macrophages, reduced binding to monocytes, reduced binding to polymorphonuclear cells, reduced direct signaling inducing apoptosis, reduced crosslinking of target-bound antibodies, reduced dendritic cell maturation, or reduced T cell priming. In one embodiment the reduced effector function is one or more selected from the group of reduced CDC, reduced ADCC, d ADCP, and reduced cytokine ion. In a particular embodiment the reduced effector function is reduced ADCC. In one embodiment the reduced ADCC is less than 20% of the ADCC d by a non-engineered Fc domain (or a T cell activating bispecific antigen binding molecule comprising a non-engineered Fc domain).

In one embodiment the amino acid mutation that reduces the binding affinity of the Fc domain to an Fc receptor and/or effector function is an amino acid substitution. In one embodiment the Fc domain comprises an amino acid substitution at a position selected from the group of E233, L234, L235, N297, P331 and P329 (numberings according to Kabat EU index). In a more specific embodiment the Fc domain comprises an amino acid tution at a position selected from the group of L234, L235 and P329 (numberings according to Kabat EU . In some embodiments the Fc domain comprises the amino acid substitutions L234A and L235A (numberings according to Kabat EU index). In one such embodiment, the Fc domain is an IgG1 Fc domain, particularly a human IgG1 Fc domain. In one embodiment the Fc domain ses an amino acid substitution at position P329. In a more specific embodiment the amino acid substitution is P329A or P329G, particularly P329G (numberings according to Kabat EU index).

In one embodiment the Fc domain comprises an amino acid substitution at position P329 and a r amino acid substitution at a position selected from E233, L234, L235, N297 and P331 (numberings according to Kabat EU index). In a more specific embodiment the further amino acid substitution is E233P, L234A, L235A, L235E, N297A, N297D or P331S. In particular embodiments the Fc domain comprises amino acid substitutions at positions P329, L234 and L235(numberings according to Kabat EU index). In more particular embodiments the Fc domain ses the amino acid mutations L234A, L235A and P329G (“P329G LALA”). In one such embodiment, the Fc domain is an IgG1 Fc domain, particularly a human IgG1 Fc domain. The “P329G LALA” combination of amino acid substitutions almost tely abolishes Fcγ or (as well as complement) binding of a human IgG1 Fc domain, as described in PCT publication no. , orated herein by reference in its entirety. WO 2012/130831 also describes methods of preparing such mutant Fc domains and methods for determining its properties such as Fc receptor binding or or functions.

IgG4 antibodies exhibit d binding affinity to Fc receptors and reduced effector functions as compared to IgG1 antibodies. Hence, in some embodiments the Fc domain of the T cell activating bispecific antigen binding molecules of the description is an IgG4 Fc , particularly a human IgG4 Fc domain. In one ment the IgG4 Fc domain comprises amino acid substitutions at position S228, specifically the amino acid substitution S228P (numberings according to Kabat EU index). To further reduce its binding ty to an Fc receptor and/or its effector function, in one embodiment the IgG4 Fc domain comprises an amino acid substitution at position L235, specifically the amino acid substitution L235E (numberings ing to Kabat EU index). In another embodiment, the IgG4 Fc domain comprises an amino acid substitution at position P329, ically the amino acid tution P329G (numberings according to Kabat EU index). In a particular embodiment, the IgG4 Fc domain comprises amino acid substitutions at positions S228, L235 and P329, specifically amino acid substitutions S228P, L235E and P329G (numberings according to Kabat EU index). Such IgG4 Fc domain mutants and their Fcγ receptor binding properties are described in PCT publication no. , incorporated herein by reference in its entirety.

In a particular embodiment the Fc domain exhibiting reduced binding affinity to an Fc receptor and/or reduced effector on, as compared to a native IgG1 Fc domain, is a human IgG1 Fc domain comprising the amino acid tutions L234A, L235A and optionally P329G, or a human IgG4 Fc domain comprising the amino acid substitutions S228P, L235E and optionally P329G (numberings ing to Kabat EU index).

In certain embodiments N-glycosylation of the Fc domain has been ated. In one such ment the Fc domain comprises an amino acid mutation at position N297, particularly an amino acid substitution replacing asparagine by e (N297A) or aspartic acid (N297D) (numberings according to Kabat EU index).

In addition to the Fc domains described hereinabove and in PCT publication no. WO 2012/130831, Fc domains with reduced Fc receptor binding and/or effector on also include those with substitution of one or more of Fc domain residues 238, 265, 269, 270, 297, 327 and 329 (U.S. Patent No. 6,737,056) (numberings according to Kabat EU index). Such Fc mutants include Fc mutants with tutions at two or more of amino acid positions 265, 269, 270, 297 and 327, including the so-called “DANA” Fc mutant with substitution of residues 265 and 297 to alanine (US Patent No. 7,332,581).

Mutant Fc domains can be prepared by amino acid deletion, substitution, insertion or modification using genetic or chemical methods well known in the art. Genetic methods may include site-specific mutagenesis of the encoding DNA sequence, PCR, gene synthesis, and the like. The correct nucleotide changes can be verified for example by sequencing.

Binding to Fc receptors can be easily determined e.g. by ELISA, or by Surface n Resonance (SPR) using standard instrumentation such as a BIAcore ment (GE Healthcare), and Fc receptors such as may be obtained by recombinant expression. A suitable such binding assay is described herein. Alternatively, binding affinity of Fc domains or cell activating bispecific antigen binding molecules sing an Fc domain for Fc receptors may be ted using cell lines known to express particular Fc receptors, such as human NK cells expressing FcγIIIa or.

Effector function of an Fc domain, or a T cell activating bispecific antigen binding molecule comprising an Fc domain, can be measured by methods known in the art. A suitable assay for measuring ADCC is described herein. Other examples of in vitro assays to assess ADCC activity of a molecule of interest are described in U.S. Patent No. 5,500,362; Hellstrom et al. Proc Natl Acad Sci USA 83, 7059-7063 (1986) and Hellstrom et al., Proc Natl Acad Sci USA 82, 1499- 1502 (1985); U.S. Patent No. 337; Bruggemann et al., J Exp Med 166, 1351-1361 (1987).

Alternatively, non-radioactive assays methods may be ed (see, for example, ACTI™ nonradioactive cytotoxicity assay for flow cytometry (CellTechnology, Inc. Mountain View, CA); and CytoTox 96® non-radioactive cytotoxicity assay (Promega, Madison, WI)). Useful effector cells for such assays include peripheral blood mononuclear cells (PBMC) and Natural Killer (NK) cells. atively, or onally, ADCC activity of the molecule of interest may be assessed in vivo, e.g. in a animal model such as that disclosed in Clynes et al., Proc Natl Acad Sci USA 95, 652-656 (1998).

In some embodiments, binding of the Fc domain to a complement component, specifically to C1q, is d. Accordingly, in some embodiments wherein the Fc domain is engineered to have reduced effector function, said reduced effector function includes reduced CDC. C1q binding assays may be carried out to determine whether the T cell activating bispecific antigen binding molecule is able to bind C1q and hence has CDC activity. See e.g., C1q and C3c binding ELISA in and . To assess complement activation, a CDC assay may be performed (see, for example, Gazzano-Santoro et al., J Immunol Methods 202, 163 (1996); Cragg et al., Blood 101, 1045-1052 (2003); and Cragg and Glennie, Blood 103, 2738- 2743 ).

Antigen Binding Moieties The antigen binding molecule of the ion is bispecific, i.e. it comprises at least two antigen binding moieties capable of specific g to two distinct antigenic inants. According to the invention, the n binding moieties are Fab molecules (i.e. antigen binding domains composed of a heavy and a light chain, each comprising a variable and a constant domain). In one embodiment said Fab molecules are human. In another embodiment said Fab molecules are zed. In yet another embodiment said Fab molecules comprise human heavy and light chain constant domains.

At least one of the antigen binding moieties is a crossover Fab le. Such modification reduces mispairing of heavy and light chains from different Fab molecules, thereby improving the yield and purity of the T cell activating ific antigen binding molecule of the description in recombinant production. In a particular crossover Fab molecule useful for the T cell activating bispecific antigen binding le of the ption, the variable domains of the Fab light chain and the Fab heavy chain (VL and VH, respectively) are exchanged. Even with this domain exchange, however, the preparation of the T cell activating bispecific antigen binding molecule may comprise certain side products due to a so-called Bence Jones-type interaction between mispaired heavy and light chains (see Schaefer et al, PNAS, 108 (2011) 11187-11191). To further reduce mispairing of heavy and light chains from different Fab molecules and thus increase the purity and yield of the desired T cell activating bispecific antigen binding molecule, according to the present description charged amino acids with opposite charges are introduced at specific amino acid positions in the CH1 and CL domains of either the Fab molecule(s) specifically binding to a target cell antigen, or the Fab molecule ically binding to an activating T cell antigen. Charge modifications are made either in the conventional Fab molecule(s) comprised in the T cell activating bispecific antigen binding molecule (such as shown e.g. in Figures 1 A-C, G-J), or in the crossover Fab molecule(s) comprised in the T cell ting bispecific antigen binding molecule (such as shown e.g. in Figure 1 D-F, K-N) (but not in both). In particular embodiments, the charge cations are made in the conventional Fab molecule(s) comprised in the T cell activating bispecific antigen binding molecule (which in ular ments specifically bind(s) to the target cell antigen).

In a particular embodiment according to the ption, the T cell activating bispecific antigen g molecule is e of simultaneous binding to a target cell antigen, ularly a tumor cell antigen, and an activating T cell antigen, particularly CD3. In one embodiment, the T cell activating bispecific antigen binding molecule is capable of crosslinking a T cell and a target cell by simultaneous binding to a target cell antigen and an activating T cell antigen. In an even more particular embodiment, such simultaneous binding results in lysis of the target cell, particularly a tumor cell. In one embodiment, such aneous binding results in activation of the T cell. In other embodiments, such simultaneous binding results in a cellular response of a T lymphocyte, particularly a cytotoxic T cyte, ed from the group of: proliferation, differentiation, cytokine ion, cytotoxic effector molecule release, cytotoxic activity, and expression of activation s. In one embodiment, binding of the T cell activating bispecific n binding molecule to the activating T cell antigen, particularly CD3, without simultaneous g to the target cell antigen does not result in T cell activation.

In one embodiment, the T cell activating bispecific antigen binding molecule is capable of re- directing cytotoxic activity of a T cell to a target cell. In a particular embodiment, said redirection is independent of diated peptide antigen presentation by the target cell and and/or specificity of the T cell.

Particularly, a T cell according to any of the embodiments of the description is a cytotoxic T cell.

In some embodiments the T cell is a CD4+ or a CD8+ T cell, particularly a CD8+ T cell.

Activating T cell antigen binding Fab molecule The T cell activating bispecific antigen binding molecule of the description comprises at least one Fab molecule which specifically binds to an activating T cell antigen (also referred to herein as an “activating T cell antigen binding Fab molecule”). In a particular embodiment, the T cell activating bispecific antigen binding molecule comprises not more than one Fab molecule (or other Fab molecule) capable of specific binding to an activating T cell antigen. In one embodiment the T cell activating bispecific antigen binding molecule es monovalent binding to the activating T cell antigen.

In particular embodiments, the Fab molecule which specifically binds an activating T cell antigen is a ver Fab molecule as described , i.e. a Fab le wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / ed by each other.

In such embodiments, the Fab molecule(s) which specifically binds a target cell antigen is a conventional Fab molecule. In embodiments where there is more than one Fab molecule which specifically binds to a target cell antigen comprised in the T cell ting bispecific antigen g le, the Fab molecule which specifically binds to an activating T cell antigen preferably is a crossover Fab le and the Fab molecules which specifically bind to a target cell antigen are conventional Fab molecules.

In alternative embodiments, the Fab molecule which specifically binds an activating T cell antigen is a conventional Fab molecule. In such embodiments, the Fab molecule(s) which specifically binds a target cell antigen is a crossover Fab molecule as described herein, i.e. a Fab molecule wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / replaced by each other.

In a particular embodiment the activating T cell n is CD3, particularly human CD3 (SEQ ID NO: 1) or lgus CD3 (SEQ ID NO: 2), most particularly human CD3. In a ular ment the activating T cell antigen binding Fab molecule is reactive for (i.e. specifically binds to) human and cynomolgus CD3. In some embodiments, the activating T cell antigen is the epsilon subunit of CD3 (CD3 epsilon).

In some embodiments, the activating T cell antigen binding Fab molecule specifically binds to CD3, particularly CD3 epsilon, and comprises at least one heavy chain complementarity determining region (CDR) selected from the group consisting of SEQ ID NO: 4, SEQ ID NO: 5 and SEQ ID NO: 6 and at least one light chain CDR selected from the group of SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10.

In one embodiment the CD3 binding Fab molecule comprises a heavy chain variable region comprising the heavy chain CDR1 of SEQ ID NO: 4, the heavy chain CDR2 of SEQ ID NO: 5, the heavy chain CDR3 of SEQ ID NO: 6, and a light chain variable region comprising the light chain CDR1 of SEQ ID NO: 8, the light chain CDR2 of SEQ ID NO: 9, and the light chain CDR3 of SEQ ID NO: 10.

In another embodiment the CD3 binding Fab le comprises a heavy chain variable region comprising the heavy chain CDR1 of SEQ ID NO: 4, the heavy chain CDR2 of SEQ ID NO: 67, the heavy chain CDR3 of SEQ ID NO: 6, and a light chain le region comprising the light chain CDR1 of SEQ ID NO: 68, the light chain CDR2 of SEQ ID NO: 9, and the light chain CDR3 of SEQ ID NO: 10.

In one embodiment the CD3 binding Fab molecule comprises a heavy chain variable region sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to SEQ ID NO: 3 and a light chain le region sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to SEQ ID NO: 7.

In one embodiment the CD3 binding Fab molecule comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 7.

In one embodiment the CD3 binding Fab molecule comprises the heavy chain variable region sequence of SEQ ID NO: 3 and the light chain variable region sequence of SEQ ID NO: 7.

Target cell antigen binding Fab molecule The T cell activating bispecific antigen binding molecule of the description comprises at least one Fab molecule which specifically binds to a target cell antigen (also referred to herein as “target cell antigen binding Fab molecule”). In certain embodiments, the T cell activating bispecific antigen binding molecule comprises two Fab les which specifically bind to a target cell antigen. In a particular such embodiment, each of these Fab molecules specifically binds to the same antigenic inant. In an even more particular embodiment, all of these Fab molecules are identical, i.e. they comprise the same amino acid sequences including the same amino acid substitutions in the CH1 and CL domain as described herein (if any). In one ment, the T cell activating bispecific antigen binding molecule comprises an immunoglobulin molecule which specifically binds to a target cell antigen. In one embodiment the T cell activating bispecific antigen binding molecule comprises not more than two Fab molecules which specifically bind to a target cell antigen.

In particular embodiments, the Fab molecule(s) which cially bind to a target cell antigen is/are a tional Fab molecule. In such embodiments, the Fab molecule(s) which specifically binds an ting T cell antigen is a crossover Fab molecule as described herein, i.e. a Fab molecule wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / replaced by each other.

In alternative embodiments, the Fab molecule(s) which specficially bind to a target cell antigen is/are a crossover Fab molecule as described herein, i.e. a Fab molecule wherein the variable domains VH and VL of the Fab heavy and light chains are exchanged / replaced by each other.

In such embodiments, the Fab molecule(s) which specifically binds an activating T cell antigen is a conventional Fab molecule.

The target cell antigen binding Fab le binds to a specific antigenic determinant and is able to direct the T cell activating bispecific antigen binding molecule to a target site, for example to a specific type of tumor cell that bears the antigenic determinant.

In certain embodiments the target cell antigen binding Fab molecule specifically binds to a cell e n.

In certain embodiments the target cell antigen binding Fab molecule is directed to an antigen associated with a pathological condition, such as an antigen ted on a tumor cell or on a virus-infected cell. Suitable target cell antigens are cell surface antigens, for e, but not limited to, cell e receptors. In particular embodiments the target cell antigen is a human n. Exemplary target cell antigens include CD20, Her2, Her3, MCSP (melanoma-associated chondroitin sulfate proteoglycan, also known as chondroitin sulfate proteoglycan 4), or BCMA (human B cell maturation target, also known as Tumor Necrosis Factor or Superfamily Member 17 (UniProt Q02223)).

In particular embodiments, the target cell antigen is CD20, particularly human CD20. In one embodiment, the target cell n is CD20 and the Fab molecule which specifically binds to said target cell antigen comprises a heavy chain le region comprising the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 46, the heavy chain CDR 2 of SEQ ID NO: 47, and the heavy chain CDR 3 of SEQ ID NO: 48, and a light chain variable region comprising the light chain CDR 1 of SEQ ID NO: 49, the light chain CDR 2 of SEQ ID NO: 50 and the light chain CDR 3 of SEQ ID NO: 51. In a further embodiment, the target cell antigen is CD20 and the Fab le which specifically binds to said target cell antigen ses a heavy chain variable region that is at least 95%, 96%, 97%, 98%, or 99% cal to the sequence of SEQ ID NO: 30, and a light chain variable region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 31, In still a further embodiment, the target cell antigen is CD20 and the Fab molecule which specifically binds to said target cell antigen comprises the heavy chain le region ce of SEQ ID NO: 30, and the light chain variable region sequence of SEQ ID NO: 31. In a particular embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 18, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 19, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 20, and a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 21. In a further particular embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide sequence of SEQ ID NO: 18, a polypeptide sequence of SEQ ID NO: 19, a polypeptide sequence of SEQ ID NO: 20 and a polypeptide sequence of SEQ ID NO: 21. In another embodiment, the T cell activating bispecific antigen binding le comprises a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 32, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 19, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 20, and a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 21. In a further embodiment, the the T cell activating ific n binding molecule comprises a polypeptide sequence of SEQ ID NO: 32, a polypeptide sequence of SEQ ID NO: 19, a polypeptide sequence of SEQ ID NO: 20 and a polypeptide sequence of SEQ ID NO: 21. In still another ment, the T cell activating bispecific antigen binding molecule comprises a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 36, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 37, a ptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 38, and a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 39. In a further embodiment, the the T cell activating bispecific antigen binding molecule comprises a polypeptide sequence of SEQ ID NO: 36, a polypeptide sequence of SEQ ID NO: 37, a polypeptide sequence of SEQ ID NO: 38 and a polypeptide sequence of SEQ ID NO: 39. In a further embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 40, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% cal to the ce of SEQ ID NO: 41, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 20, and a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% cal to the sequence of SEQ ID NO: 21. In a further embodiment, the the T cell activating bispecific antigen binding molecule comprises a polypeptide sequence of SEQ ID NO: 40, a polypeptide sequence of SEQ ID NO: 41, a polypeptide sequence of SEQ ID NO: 20 and a polypeptide sequence of SEQ ID NO: 21.

In other embodiments, the target antigen is Her2, ularly human Her2. In one embodiment, the target cell antigen is Her2 and the Fab molecule which specifically binds to said target cell antigen comprises a heavy chain variable region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 61, and a light chain variable region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 62, In a further embodiment, the target cell n is Her2 and the Fab molecule which specifically binds to said target cell antigen comprises the heavy chain variable region ce of SEQ ID NO: 61, and the light chain variable region sequence of SEQ ID NO: 62. In one embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% cal to the sequence of SEQ ID NO: 21, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the ce of SEQ ID NO: 52, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 53, and a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 54. In a further embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide ce of SEQ ID NO: 21, a polypeptide sequence of SEQ ID NO: 52, a polypeptide ce of SEQ ID NO: 53 and a polypeptide sequence of SEQ ID NO: 54.

In other embodiments, the target antigen is Her3, particularly human Her3. In one embodiment, the target cell n is Her3 and the Fab molecule which specifically binds to said target cell n comprises a heavy chain variable region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 63, and a light chain le region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 64, In a further embodiment, the target cell antigen is Her3 and the Fab molecule which specifically binds to said target cell antigen ses the heavy chain variable region sequence of SEQ ID NO: 63, and the light chain variable region sequence of SEQ ID NO: 64. In one embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 21, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 55, a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 56, and a polypeptide that is at least 95%, 96%, 97%, 98%, or 99% cal to the ce of SEQ ID NO: 57. In a further embodiment, the T cell activating bispecific antigen binding molecule comprises a polypeptide sequence of SEQ ID NO: 21, a polypeptide ce of SEQ ID NO: 55, a polypeptide sequence of SEQ ID NO: 56 and a polypeptide sequence of SEQ ID NO: 57.

In other embodiments, the target antigen is melanoma-associated chondroitin sulfate proteoglycan (MCSP), ularly human MCSP. In one ment, the target cell antigen is MCSP and the Fab molecule which specifically binds to said target cell antigen comprises a heavy chain variable region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 65, and a light chain variable region that is at least 95%, 96%, 97%, 98%, or 99% identical to the sequence of SEQ ID NO: 66, In a further embodiment, the target cell antigen is Her2 and the Fab molecule which specifically binds to said target cell antigen comprises the heavy chain variable region sequence of SEQ ID NO: 65, and the light chain variable region sequence of SEQ ID NO: 66.

In some embodiments, the target n is BCMA. In other embodiments, the target cell antigen is not BCMA.

Polynucleotides The description further includes isolated polynucleotides encoding a T cell activating bispecific antigen binding molecule as described herein or a fragment f. In some ments, said fragment is an antigen binding fragment.

The polynucleotides encoding T cell activating bispecific antigen binding molecules of the description may be expressed as a single polynucleotide that encodes the entire T cell activating bispecific antigen binding le or as multiple (e.g., two or more) polynucleotides that are co-expressed. Polypeptides encoded by polynucleotides that are co-expressed may ate through, e.g., disulfide bonds or other means to form a functional T cell activating bispecific n binding molecule. For example, the light chain portion of a Fab molecule may be encoded by a separate polynucleotide from the portion of the T cell ting bispecific antigen binding molecule comprising the heavy chain portion of the Fab molecule, an Fc domain subunit and optionally (part of) another Fab molecule. When ressed, the heavy chain polypeptides will associate with the light chain polypeptides to form the Fab molecule. In another example, the portion of the T cell activating bispecific n binding molecule comprising one of the two Fc domain subunits and optionally (part of) one or more Fab molecules could be encoded by a separate polynucleotide from the portion of the T cell activating bispecific antigen binding le comprising the the other of the two Fc domain subunits and optionally (part of) a Fab molecule. When co-expressed, the Fc domain subunits will associate to form the Fc domain.

In some embodiments, the ed polynucleotide encodes the entire T cell activating bispecific antigen binding molecule according to the ption as described herein. In other embodiments, the isolated polynucleotide encodes a polypeptides comprised in the T cell activating bispecific antigen binding molecule according to the description as bed herein.

In certain embodiments the polynucleotide or nucleic acid is DNA. In other embodiments, a polynucleotide of the present description is RNA, for example, in the form of messenger RNA (mRNA). RNA of the present description may be single stranded or double ed.

Recombinant Methods T cell activating bispecific antigen binding molecules of the ption may be obtained, for example, by solid-state peptide synthesis (e.g. Merrifield solid phase synthesis) or recombinant production. For recombinant tion one or more polynucleotide encoding the T cell activating bispecific antigen binding molecule (fragment), e.g., as described above, is isolated and inserted into one or more s for further cloning and/or expression in a host cell. Such polynucleotide may be readily isolated and sequenced using conventional procedures. In one embodiment described is a vector, preferably an expression vector, comprising one or more of the cleotides of the description. Methods which are well known to those d in the art can be used to construct expression vectors containing the coding ce of a T cell activating bispecific antigen binding molecule ent) along with appropriate transcriptional/translational control signals. These methods include in vitro recombinant DNA techniques, synthetic techniques and in vivo recombination/genetic recombination. See, for example, the techniques described in Maniatis et al., MOLECULAR CLONING: A LABORATORY , Cold Spring Harbor Laboratory, N.Y. (1989); and Ausubel et al., CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, Greene Publishing Associates and Wiley Interscience, N.Y (1989). The expression vector can be part of a plasmid, virus, or may be a nucleic acid fragment. The expression vector includes an expression cassette into which the polynucleotide ng the T cell activating bispecific antigen binding molecule (fragment) (i.e. the coding region) is cloned in operable association with a promoter and/or other transcription or translation control elements. As used herein, a "coding region" is a portion of nucleic acid which consists of codons translated into amino acids. Although a "stop codon" (TAG, TGA, or TAA) is not translated into an amino acid, it may be considered to be part of a coding region, if present, but any flanking sequences, for example promoters, ribosome binding sites, transcriptional terminators, introns, 5' and 3' untranslated regions, and the like, are not part of a coding region.

Two or more coding regions can be present in a single polynucleotide construct, e.g. on a single , or in separate polynucleotide constructs, e.g. on separate (different) vectors. Furthermore, any vector may n a single coding region, or may se two or more coding regions, e.g. a vector of the present description may encode one or more polypeptides, which are post- or cotranslationally separated into the final ns via proteolytic cleavage. In addition, a vector, polynucleotide, or c acid of the description may encode heterologous coding regions, either fused or d to a polynucleotide encoding the T cell activating bispecific antigen binding molecule (fragment) of the description, or variant or derivative thereof. Heterologous coding regions include without limitation specialized elements or , such as a secretory signal peptide or a heterologous functional domain. An operable association is when a coding region for a gene t, e.g. a polypeptide, is associated with one or more regulatory sequences in such a way as to place expression of the gene product under the influence or control of the regulatory sequence(s). Two DNA fragments (such as a polypeptide coding region and a promoter associated therewith) are "operably ated" if induction of promoter function results in the ription of mRNA encoding the d gene product and if the nature of the linkage between the two DNA fragments does not interfere with the ability of the expression regulatory sequences to direct the expression of the gene product or interfere with the ability of the DNA template to be transcribed. Thus, a promoter region would be operably ated with a nucleic acid encoding a ptide if the promoter was capable of effecting transcription of that nucleic acid. The promoter may be a pecific promoter that directs substantial transcription of the DNA only in predetermined cells. Other transcription l elements, besides a er, for example enhancers, operators, repressors, and ription termination signals, can be operably associated with the cleotide to direct cell-specific ription. le promoters and other transcription control regions are disclosed herein. A variety of transcription control regions are known to those skilled in the art. These e, without limitation, transcription control regions, which function in vertebrate cells, such as, but not limited to, promoter and enhancer segments from cytomegaloviruses (e.g. the immediate early promoter, in ction with intron-A), simian virus 40 (e.g. the early er), and retroviruses (such as, e.g. Rous sarcoma virus). Other transcription control regions include those derived from vertebrate genes such as actin, heat shock protein, bovine growth hormone and rabbit in, as well as other sequences capable of controlling gene expression in eukaryotic cells. Additional suitable transcription control regions include tissue-specific promoters and enhancers as well as inducible promoters (e.g. promoters ble tetracyclins). Similarly, a variety of translation control elements are known to those of ordinary skill in the art. These include, but are not limited to ribosome binding sites, translation initiation and termination codons, and elements derived from viral systems (particularly an internal ribosome entry site, or IRES, also referred to as a CITE sequence). The expression cassette may also include other features such as an origin of replication, and/or some integration elements such as retroviral long terminal s (LTRs), or adeno-associated viral (AAV) inverted terminal s (ITRs).

Polynucleotide and nucleic acid coding s of the present description may be associated with additional coding regions which encode secretory or signal peptides, which direct the secretion of a polypeptide d by a polynucleotide of the present description. For example, if secretion of the T cell activating bispecific antigen binding molecule is desired, DNA encoding a signal ce may be placed upstream of the nucleic acid encoding a T cell activating bispecific antigen binding molecule of the description or a fragment thereof. ing to the signal hypothesis, proteins secreted by mammalian cells have a signal peptide or secretory leader ce which is cleaved from the mature protein once export of the growing protein chain across the rough endoplasmic reticulum has been initiated. Those of ordinary skill in the art are aware that polypeptides secreted by vertebrate cells generally have a signal peptide fused to the N-terminus of the polypeptide, which is cleaved from the translated polypeptide to produce a secreted or "mature" form of the polypeptide. In certain embodiments, the native signal peptide, e.g. an immunoglobulin heavy chain or light chain signal peptide is used, or a functional derivative of that sequence that retains the y to direct the secretion of the polypeptide that is operably associated with it. Alternatively, a heterologous mammalian signal peptide, or a functional derivative thereof, may be used. For example, the ype leader sequence may be substituted with the leader sequence of human tissue plasminogen activator (TPA) or mouse βglucuronidase.

DNA encoding a short n sequence that could be used to facilitate later purification (e.g. a histidine tag) or assist in labeling the T cell activating bispecific antigen binding molecule may be included within or at the ends of the T cell activating bispecific antigen binding molecule (fragment) encoding cleotide.

In a further embodiment, a host cell is described sing one or more polynucleotides of thedescription. In certain embodiments a host cell is described comprising one or more vectors of thedescription. The polynucleotides and vectors may incorporate any of the es, singly or in combination, bed herein in relation to polynucleotides and vectors, respectively. In one such embodiment a host cell comprises (e.g. has been transformed or transfected with) a vector comprising a polynucleotide that encodes (part of) a T cell activating ific antigen binding molecule of the description. As used herein, the term "host cell" refers to any kind of cellular system which can be engineered to generate the T cell ting bispecific antigen binding molecules of the description or nts thereof. Host cells suitable for replicating and for supporting expression of T cell activating bispecific antigen binding molecules are well known in the art. Such cells may be ected or transduced as riate with the particular expression vector and large quantities of vector containing cells can be grown for seeding large scale fermenters to obtain ient ties of the T cell activating bispecific antigen binding molecule for clinical applications. Suitable host cells include prokaryotic microorganisms, such as E. coli, or various eukaryotic cells, such as Chinese hamster ovary cells (CHO), insect cells, or the like. For example, polypeptides may be produced in bacteria in particular when glycosylation is not needed. After expression, the polypeptide may be isolated from the bacterial cell paste in a soluble fraction and can be further purified. In addition to prokaryotes, otic microbes such as filamentous fungi or yeast are suitable cloning or expression hosts for polypeptide-encoding vectors, including fungi and yeast strains whose glycosylation pathways have been “humanized”, resulting in the production of a polypeptide with a partially or fully human glycosylation pattern.

See Gerngross, Nat h 22, 1409-1414 (2004), and Li et al., Nat Biotech 24, 210-215 (2006).

Suitable host cells for the expression of (glycosylated) polypeptides are also derived from ellular organisms (invertebrates and vertebrates). Examples of invertebrate cells include plant and insect cells. Numerous baculoviral strains have been identified which may be used in conjunction with insect cells, particularly for transfection of Spodoptera frugiperda cells. Plant cell cultures can also be utilized as hosts. See e.g. US Patent Nos. 177, 6,040,498, 6,420,548, 7,125,978, and 6,417,429 (describing PLANTIBODIESTM technology for producing antibodies in transgenic plants). Vertebrate cells may also be used as hosts. For e, mammalian cell lines that are adapted to grow in suspension may be useful. Other examples of useful ian host cell lines are monkey kidney CV1 line transformed by SV40 (COS-7); human embryonic kidney line (293 or 293T cells as described, e.g., in Graham et al., J Gen Virol 36, 59 (1977)), baby hamster kidney cells (BHK), mouse sertoli cells (TM4 cells as described, e.g., in Mather, Biol Reprod 23, 243-251 (1980)), monkey kidney cells (CV1), African green monkey kidney cells (VERO-76), human cervical carcinoma cells (HELA), canine kidney cells (MDCK), buffalo rat liver cells (BRL 3A), human lung cells (W138), human liver cells (Hep G2), mouse mammary tumor cells (MMT 060562), TRI cells (as described, e.g., in Mather et al., Annals N.Y. Acad Sci 383, 44-68 (1982)), MRC 5 cells, and FS4 cells. Other useful mammalian host cell lines include Chinese hamster ovary (CHO) cells, including dhfr- CHO cells (Urlaub et al., Proc Natl Acad Sci USA 77, 4216 ); and myeloma cell lines such as YO, NS0, P3X63 and Sp2/0. For a review of certain mammalian host cell lines suitable for protein production, see, e.g., Yazaki and Wu, Methods in Molecular Biology, Vol. 248 (B.K.C. Lo, ed., Humana Press, Totowa, NJ), pp. 255-268 (2003). Host cells include cultured cells, e.g., mammalian cultured cells, yeast cells, insect cells, bacterial cells and plant cells, to name only a few, but also cells comprised within a transgenic animal, transgenic plant or cultured plant or animal tissue. In one embodiment, the host cell is a eukaryotic cell, preferably a mammalian cell, such as a Chinese Hamster Ovary (CHO) cell, a human embryonic kidney (HEK) cell or a lymphoid cell (e.g., Y0, NS0, Sp20 cell).

Standard technologies are known in the art to express foreign genes in these systems. Cells expressing a polypeptide comprising either the heavy or the light chain of an n binding domain such as an antibody, may be engineered so as to also express the other of the antibody chains such that the sed product is an antibody that has both a heavy and a light chain.

In one ment, a method of producing a T cell activating bispecific antigen g molecule according to the description is included, wherein the method comprises culturing a host cell comprising a cleotide encoding the T cell activating bispecific antigen binding molecule, as described herein, under ions suitable for expression of the T cell activating bispecific antigen g molecule, and recovering the T cell activating bispecific n binding molecule from the host cell (or host cell culture medium).

The components of the T cell activating bispecific antigen binding le are genetically fused to each other. T cell activating ific antigen binding molecule can be designed such that its components are fused directly to each other or indirectly through a linker sequence. The composition and length of the linker may be ined in accordance with methods well known in the art and may be tested for efficacy. Examples of linker sequences between different components of T cell ting bispecific antigen g molecules are found in the sequences described herein. Additional sequences may also be included to incorporate a cleavage site to separate the individual components of the fusion if d, for example an endopeptidase recognition sequence.

In certain embodiments the one or more antigen binding moieties of the T cell activating bispecific n binding molecules comprise at least an antibody variable region capable of binding an antigenic determinant. Variable regions can form part of and be derived from naturally or non-naturally occurring antibodies and fragments thereof. Methods to produce polyclonal antibodies and monoclonal antibodies are well known in the art (see e.g. Harlow and Lane, "Antibodies, a laboratory manual", Cold Spring Harbor Laboratory, 1988). Non-naturally occurring antibodies can be constructed using solid peptide sis, can be produced recombinantly (e.g. as described in U.S. patent No. 4,186,567) or can be obtained, for example, by screening combinatorial libraries comprising variable heavy chains and variable light chains (see e.g. U.S. Patent. No. 5,969,108 to McCafferty).

Any animal species of antibody, dy fragment, antigen binding domain or variable region can be used in the T cell activating bispecific antigen binding molecules of the description. Nonlimiting antibodies, antibody fragments, n binding domains or variable regions useful in the t description can be of , primate, or human origin. If the T cell activating bispecific antigen binding molecule is ed for human use, a chimeric form of antibody may be used wherein the constant regions of the antibody are from a human. A zed or fully human form of the antibody can also be prepared in accordance with methods well known in the art (see e. g. U.S. Patent No. 5,565,332 to Winter). Humanization may be achieved by various methods including, but not limited to (a) grafting the non-human (e.g., donor antibody) CDRs onto human (e.g. ent antibody) framework and constant regions with or without retention of critical framework residues (e.g. those that are important for retaining good antigen binding affinity or antibody functions), (b) grafting only the non-human specificity-determining regions (SDRs or a-CDRs; the residues critical for the antibody-antigen interaction) onto human framework and constant regions, or (c) transplanting the entire non-human variable domains, but "cloaking" them with a human-like section by replacement of surface residues. Humanized antibodies and methods of making them are reviewed, e.g., in Almagro and Fransson, Front Biosci 13, 1619-1633 (2008), and are further described, e.g., in ann et al., Nature 332, 323-329 (1988); Queen et al., Proc Natl Acad Sci USA 86, 10029-10033 (1989); US Patent Nos. 5,821,337, 7,527,791, 6,982,321, and 7,087,409; Jones et al., Nature 321, 522-525 (1986); Morrison et al., Proc Natl Acad Sci 81, 6851-6855 (1984); Morrison and Oi, Adv Immunol 44, 65-92 (1988); Verhoeyen et al., Science 239, 1534-1536 (1988); Padlan, Molec Immun 31(3), 169-217 (1994); Kashmiri et al., Methods 36, 25-34 (2005) (describing SDR (a-CDR) grafting); Padlan, Mol l 28, 489-498 (1991) (describing “resurfacing”); Dall’Acqua et al., Methods 36, 43-60 (2005) (describing “FR shuffling”); and n et al., s 36, 61-68 (2005) and Klimka et al., Br J Cancer 83, 252-260 (2000) (describing the “guided selection” approach to FR shuffling). Human antibodies and human variable regions can be ed using various techniques known in the art. Human antibodies are bed generally in van Dijk and van de Winkel, Curr Opin Pharmacol 5, 368-74 (2001) and Lonberg, Curr Opin Immunol 20, 450-459 (2008). Human variable regions can form part of and be derived from human monoclonal antibodies made by the oma method (see e.g. onal Antibody Production Techniques and Applications, pp. 51-63 (Marcel Dekker, Inc., New York, 1987)). Human antibodies and human variable regions may also be prepared by administering an immunogen to a enic animal that has been modified to produce intact human antibodies or intact antibodies with human le s in response to antigenic challenge (see e.g. Lonberg, Nat Biotech 23, 1117-1125 . Human antibodies and human variable regions may also be generated by isolating Fv clone variable region sequences selected from human-derived phage display libraries (see e.g., Hoogenboom et al. in Methods in Molecular Biology 178, 1-37 (O’Brien et al., ed., Human Press, , NJ, 2001); and McCafferty et al., Nature 348, 552- 554; Clackson et al., Nature 352, 624-628 (1991)). Phage typically display antibody fragments, either as single-chain Fv (scFv) fragments or as Fab fragments.

In certain embodiments, the antigen g moieties useful in the present description are engineered to have enhanced binding affinity according to, for example, the methods disclosed in U.S. Pat. Appl. Publ. No. 132066, the entire contents of which are hereby orated by reference. The ability of the T cell activating bispecific antigen g molecule of the description, including the T cell activating bispecific antigen g molecule of the invention, to bind to a specific antigenic determinant can be measured either through an enzyme-linked immunosorbent assay (ELISA) or other techniques familiar to one of skill in the art, e.g. surface plasmon resonance technique (analyzed on a BIACORE T100 system) (Liljeblad, et al., Glyco J 17, 323-329 (2000)), and ional g assays (Heeley, Endocr Res 28, 217-229 (2002)).

Competition assays may be used to identify an antibody, antibody fragment, antigen binding domain or variable domain that competes with a reference antibody for binding to a particular antigen, e.g. an antibody that competes with the V9 antibody for binding to CD3. In certain embodiments, such a competing antibody binds to the same epitope (e.g. a linear or a conformational epitope) that is bound by the reference antibody. Detailed exemplary methods for mapping an epitope to which an antibody binds are provided in Morris (1996) “Epitope Mapping Protocols,” in Methods in Molecular Biology vol. 66 (Humana Press, Totowa, NJ). In an exemplary competition assay, immobilized antigen (e.g. CD3) is incubated in a solution comprising a first labeled antibody that binds to the antigen (e.g. V9 antibody, described in US 6,054,297) and a second unlabeled antibody that is being tested for its ability to compete with the first dy for binding to the antigen. The second dy may be present in a hybridoma supernatant. As a control, immobilized antigen is incubated in a solution comprising the first labeled dy but not the second unlabeled antibody. After incubation under conditions permissive for binding of the first antibody to the antigen, excess unbound antibody is removed, and the amount of label associated with immobilized antigen is measured. If the amount of label ated with immobilized antigen is substantially reduced in the test sample relative to the control sample, then that indicates that the second dy is competing with the first antibody for g to the n. See Harlow and Lane (1988) dies: A Laboratory Manual ch.14 (Cold Spring Harbor Laboratory, Cold Spring Harbor, NY).

T cell activating bispecific antigen binding molecules prepared as described herein may be purified by art-known techniques such as high performance liquid chromatography, ion exchange chromatography, gel electrophoresis, affinity chromatography, size exclusion chromatography, and the like. The actual conditions used to purify a particular protein will depend, in part, on factors such as net charge, hydrophobicity, hilicity etc., and will be apparent to those having skill in the art. For affinity chromatography purification an antibody, , receptor or n can be used to which the T cell activating bispecific n binding le binds. For example, for affinity chromatography purification of T cell activating bispecific n binding molecules of the ption, a matrix with protein A or protein G may be used. Sequential Protein A or G affinity chromatography and size ion chromatography can be used to isolate a T cell activating ific antigen binding molecule essentially as described in the Examples. The purity of the T cell activating bispecific antigen binding molecule can be determined by any of a variety of well known analytical methods including gel electrophoresis, high pressure liquid chromatography, and the like. For example, the heavy chain fusion proteins expressed as bed in the Examples were shown to be intact and properly assembled as demonstrated by reducing SDS-PAGE (see e.g. Figure 3). Three bands were ed at approximately Mr 25,000, Mr 50,000 and Mr , corresponding to the predicted molecular weights of the T cell activating bispecific antigen binding molecule light chain, heavy chain and heavy chain/light chain fusion n.

Assays T cell activating bispecific antigen binding molecules bed herein may be identified, screened for, or characterized for their physical/chemical properties and/or biological activities by various assays known in the art.

Affinity assays The ty of the T cell activating bispecific antigen binding molecule for an Fc receptor or a target antigen can be determined in accordance with the methods set forth in the Examples by surface plasmon resonance (SPR), using standard mentation such as a e instrument (GE Healthcare), and receptors or target proteins such as may be obtained by recombinant expression. Alternatively, binding of T cell activating bispecific antigen binding les for different receptors or target antigens may be evaluated using cell lines expressing the particular receptor or target antigen, for example by flow cytometry . A specific illustrative and exemplary embodiment for measuring binding affinity is described in the following and in the Examples below. ing to one embodiment, KD is measured by surface plasmon nce using a BIACORE® T100 machine (GE Healthcare) at 25 °C.

To analyze the interaction between the Fc-portion and Fc receptors, His-tagged inant Fcreceptor is captured by an anti-Penta His antibody (Qiagen) immobilized on CM5 chips and the bispecific constructs are used as analytes. Briefly, ymethylated dextran biosensor chips (CM5, GE Healthcare) are activated with N-ethyl-N’-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) according to the supplier’s instructions.

Anti Penta-His antibody is diluted with 10 mM sodium acetate, pH 5.0, to 40 μg/ml before injection at a flow rate of 5 μl/min to achieve approximately 6500 response units (RU) of coupled protein. Following the injection of the ligand, 1 M ethanolamine is injected to block unreacted groups. Subsequently the Fc-receptor is captured for 60 s at 4 or 10 nM. For kinetic measurements, old serial ons of the bispecific construct (range between 500 nM and 4000 nM) are injected in HBS-EP (GE Healthcare, 10 mM HEPES, 150 mM NaCl, 3 mM EDTA, 0.05 % Surfactant P20, pH 7.4) at 25 °C at a flow rate of 30 μl/min for 120 s.

To determine the affinity to the target antigen, bispecific constructs are captured by an anti human Fab specific antibody (GE Healthcare) that is immobilized on an activated CM5-sensor chip surface as described for the anti Penta-His antibody. The final amount of coupled protein is is approximately 12000 RU. The bispecific ucts are captured for 90 s at 300 nM. The target ns are passed through the flow cells for 180 s at a concentration range from 250 to 1000 nM with a flowrate of 30 μl/min. The dissociation is monitored for 180 s.

Bulk refractive index differences are corrected for by subtracting the response obtained on reference flow cell. The steady state response was used to derive the dissociation constant KD by non-linear curve fitting of the Langmuir binding isotherm. Association rates (kon) and dissociation rates (koff) are ated using a simple one-to-one Langmuir binding model (BIACORE® T100 Evaluation Software version 1.1.1) by simultaneously fitting the ation and dissociation sensorgrams. The equilibrium dissociation constant (KD) is calculated as the ratio koff/kon. See, e.g., Chen et al., J Mol Biol 293, 865-881 (1999).

Activity assays Biological activity of the T cell activating bispecific antigen binding molecules of the description, including the T cell activating ific antigen g molecule of the invention, can be measured by various assays as described in the Examples. Biological activities may for example include the induction of proliferation of T cells, the induction of signaling in T cells, the induction of expression of activation markers in T cells, the induction of ne secretion by T cells, the induction of lysis of target cells such as tumor cells, and the induction of tumor sion and/or the improvement of survival.

Compositions, Formulations, and Routes of stration In a r embodiment, the description includes pharmaceutical compositions comprising any of the T cell activating bispecific antigen binding molecules described herein, e.g., for use in any of the below therapeutic methods. In one embodiment, a pharmaceutical composition comprises any of the T cell activating bispecific antigen binding molecules described herein and a pharmaceutically acceptable carrier. In r embodiment, a pharmaceutical composition comprises any of the T cell activating bispecific n binding molecules described herein and at least one onal therapeutic agent, e.g., as described below.

Further described is a method of producing a T cell activating bispecific antigen binding molecule of the description in a form suitable for administration in vivo, the method comprising (a) obtaining a T cell activating bispecific antigen binding molecule according to the description, and (b) formulating the T cell ting bispecific antigen binding molecule with at least one pharmaceutically acceptable carrier, whereby a preparation of T cell activating bispecific antigen binding molecule is formulated for administration in vivo.

Pharmaceutical compositions of the present description comprise a therapeutically effective amount of one or more T cell activating bispecific antigen binding molecule dissolved or dispersed in a pharmaceutically able carrier. The phrases aceutical or pharmacologically acceptable" refers to molecular entities and compositions that are generally non-toxic to recipients at the dosages and concentrations employed, i.e. do not produce an adverse, allergic or other untoward reaction when administered to an animal, such as, for example, a human, as appropriate. The preparation of a pharmaceutical composition that contains at least one T cell activating bispecific antigen binding molecule and ally an additional active ingredient will be known to those of skill in the art in light of the present disclosure, as exemplified by Remington's Pharmaceutical Sciences, 18th Ed. Mack Printing Company, 1990, incorporated herein by reference. Moreover, for animal (e.g., human) administration, it will be understood that ations should meet sterility, nicity, general safety and purity standards as required by FDA Office of Biological Standards or corresponding authorities in other countries. Preferred compositions are lized formulations or aqueous solutions. As used herein, "pharmaceutically acceptable carrier" includes any and all solvents, buffers, sion media, gs, surfactants, antioxidants, preservatives (e.g. cterial agents, antifungal agents), isotonic agents, absorption delaying agents, salts, preservatives, antioxidants, proteins, drugs, drug stabilizers, polymers, gels, binders, excipients, disintegration agents, lubricants, sweetening agents, ing agents, dyes, such like materials and ations thereof, as would be known to one of ordinary skill in the art (see, for example, ton's Pharmaceutical Sciences, 18th Ed. Mack Printing Company, 1990, pp. 1289-1329, incorporated herein by reference). Except insofar as any conventional carrier is incompatible with the active ingredient, its use in the therapeutic or pharmaceutical compositions is contemplated.

The composition may se different types of rs depending on whether it is to be stered in solid, liquid or aerosol form, and whether it need to be sterile for such routes of administration as injection. T cell ting ific antigen g molecules of the present description (and any additional therapeutic agent) can be administered intravenously, intradermally, intraarterially, intraperitoneally, intralesionally, intracranially, intraarticularly, intraprostatically, intrasplenically, intrarenally, intrapleurally, intratracheally, intranasally, intravitreally, intravaginally, intrarectally, intratumorally, intramuscularly, intraperitoneally, subcutaneously, subconjunctivally, esicularlly, mucosally, intrapericardially, intraumbilically, intraocularally, orally, topically, locally, by inhalation (e.g. aerosol inhalation), ion, on, continuous infusion, localized ion bathing target cells directly, via a er, via a lavage, in cremes, in lipid compositions (e.g. liposomes), or by other method or any combination of the forgoing as would be known to one of ordinary skill in the art (see, for example, Remington's Pharmaceutical Sciences, 18th Ed. Mack ng Company, 1990, incorporated herein by reference). eral administration, in particular intravenous injection, is most commonly used for administering polypeptide molecules such as the T cell activating bispecific antigen binding molecules of the description.

Parenteral compositions include those designed for administration by injection, e.g. subcutaneous, intradermal, intralesional, intravenous, intraarterial intramuscular, intrathecal or intraperitoneal ion. For injection, the T cell activating bispecific antigen binding molecules of the ption may be formulated in aqueous ons, preferably in physiologically compatible buffers such as Hanks' solution, Ringer's solution, or physiological saline buffer. The solution may contain atory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the T cell activating bispecific antigen binding molecules may be in powder form for constitution with a le vehicle, e.g., sterile n-free water, before use.

Sterile injectable solutions are ed by incorporating the T cell activating bispecific antigen binding molecules of the description in the required amount in the appropriate solvent with various of the other ingredients enumerated below, as required. Sterility may be readily accomplished, e.g., by filtration through sterile filtration membranes. Generally, dispersions are prepared by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and/or the other ingredients. In the case of sterile powders for the preparation of sterile injectable solutions, suspensions or emulsion, the preferred methods of preparation are vacuum-drying or freeze-drying ques which yield a powder of the active ient plus any additional desired ingredient from a previously sterile-filtered liquid medium thereof. The liquid medium should be suitably buffered if necessary and the liquid diluent first rendered isotonic prior to injection with sufficient saline or glucose. The composition must be stable under the conditions of manufacture and storage, and preserved against the inating action of microorganisms, such as bacteria and fungi. It will be appreciated that endotoxin contamination should be kept minimally at a safe level, for example, less that 0.5 ng/mg n.

Suitable pharmaceutically acceptable carriers include, but are not limited to: buffers such as ate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride; benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) ptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic rs such as polyvinylpyrrolidone; amino acids such as e, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes (e.g. Zn-protein complexes); and/or non-ionic surfactants such as polyethylene glycol (PEG). Aqueous injection sions may contain compounds which increase the viscosity of the suspension, such as sodium carboxymethyl cellulose, sorbitol, dextran, or the like. ally, the suspension may also contain suitable izers or agents which increase the solubility of the nds to allow for the preparation of highly concentrated solutions. Additionally, suspensions of the active compounds may be prepared as riate oily injection suspensions. Suitable lipophilic solvents or es include fatty oils such as sesame oil, or synthetic fatty acid esters, such as ethyl cleats or cerides, or liposomes.

Active ingredients may be entrapped in microcapsules prepared, for example, by coacervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or n- microcapsules and poly-(methylmethacylate) microcapsules, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, mulsions, nanoparticles and nanocapsules) or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences (18th Ed. Mack Printing Company, 1990). Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semipermeable matrices of solid hydrophobic polymers containing the polypeptide, which matrices are in the form of shaped articles, e.g. films, or microcapsules. In particular embodiments, prolonged absorption of an injectable ition can be brought about by the use in the compositions of agents delaying absorption, such as, for e, aluminum monostearate, gelatin or combinations thereof.

In addition to the compositions bed previously, the T cell activating bispecific antigen g molecules may also be formulated as a depot preparation. Such long acting formulations may be administered by tation (for example subcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the T cell activating bispecific antigen binding molecules may be formulated with suitable polymeric or hydrophobic materials (for example as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a gly soluble salt.

Pharmaceutical compositions comprising the T cell ting bispecific antigen binding molecules of the description may be manufactured by means of tional mixing, dissolving, emulsifying, ulating, entrapping or lyophilizing processes. Pharmaceutical compositions may be formulated in conventional manner using one or more physiologically acceptable carriers, diluents, excipients or auxiliaries which facilitate processing of the proteins into preparations that can be used pharmaceutically. Proper formulation is dependent upon the route of administration chosen.

The T cell activating bispecific antigen binding molecules may be formulated into a composition in a free acid or base, neutral or salt form. Pharmaceutically acceptable salts are salts that ntially retain the biological activity of the free acid or base. These include the acid addition salts, e.g., those formed with the free amino groups of a proteinaceous composition, or which are formed with nic acids such as for example, hydrochloric or phosphoric acids, or such organic acids as acetic, oxalic, tartaric or mandelic acid. Salts formed with the free carboxyl groups can also be derived from nic bases such as for example, sodium, potassium, um, calcium or ferric hydroxides; or such organic bases as isopropylamine, trimethylamine, histidine or procaine. Pharmaceutical salts tend to be more soluble in aqueous and other protic solvents than are the corresponding free base forms.

Therapeutic Methods and Compositions Any of the T cell activating bispecific antigen binding molecules described herein may be used in therapeutic methods. T cell activating bispecific antigen binding molecules of the ption can be used as immunotherapeutic agents, for example in the ent of s.

For use in therapeutic methods, T cell activating bispecific antigen binding molecules of the description would be ated, dosed, and administered in a fashion consistent with good medical practice. Factors for consideration in this context e the particular disorder being treated, the particular mammal being treated, the al condition of the individual patient, the cause of the disorder, the site of delivery of the agent, the method of administration, the scheduling of administration, and other factors known to medical practitioners.

In one aspect, T cell activating ific antigen binding molecules of the invention for use as a medicament are ed. In further aspects, T cell activating bispecific antigen binding les of the invention for use in treating a e are provided. In certain embodiments, T cell activating bispecific antigen binding molecules of the invention for use in a method of treatment are provided. In one embodiment, the invention provides a T cell ting bispecific antigen binding molecule as described herein for use in the treatment of a disease in an individual in need thereof. In certain embodiments, the description includes a T cell activating bispecific antigen binding molecule for use in a method of treating an individual having a disease comprising administering to the individual a eutically effective amount of the T cell activating bispecific antigen binding molecule. In certain embodiments the disease to be d is a proliferative disorder. In a particular embodiment the disease is cancer. In certain embodiments the method further comprises administering to the individual a therapeutically effective amount of at least one additional therapeutic agent, e.g., an anti-cancer agent if the disease to be treated is . In further embodiments, the description includes a T cell activating bispecific antigen binding molecule as described herein for use in inducing lysis of a target cell, particularly a tumor cell. In n embodiments, the description includes a T cell activating bispecific antigen binding molecule for use in a method of inducing lysis of a target cell, particularly a tumor cell, in an individual comprising stering to the individual an effective amount of the T cell activating bispecific n binding molecule to induce lysis of a target cell. An “individual” ing to any of the above embodiments is a mammal, preferably a human.

In a further aspect, the invention provides for the use of a T cell activating bispecific antigen binding molecule of the invention in the manufacture or preparation of a medicament. In one embodiment the medicament is for the treatment of a disease in an individual in need thereof. In a further embodiment, the medicament is for use in a method of treating a e comprising administering to an individual having the disease a therapeutically effective amount of the medicament. In certain embodiments the e to be treated is a proliferative er. In a particular embodiment the disease is cancer. In one embodiment, the method further comprises stering to the individual a therapeutically effective amount of at least one additional therapeutic agent, e.g., an anti-cancer agent if the disease to be treated is cancer. In a further embodiment, the medicament is for inducing lysis of a target cell, particularly a tumor cell. In still a further embodiment, the medicament is for use in a method of inducing lysis of a target cell, particularly a tumor cell, in an individual sing administering to the individual an effective amount of the medicament to induce lysis of a target cell. An “individual” ing to any of the above ments may be a mammal, preferably a human.

In a further embodiment, the description includes a method for treating a disease. In one embodiment, the method comprises administering to an individual having such disease a therapeutically effective amount of a T cell activating bispecific antigen g molecule of the ption. In one embodiment a ition is administered to said dual, comprising the T cell activating bispecific antigen binding molecule of the description in a pharmaceutically acceptable form. In certain embodiments the disease to be treated is a proliferative disorder. In a particular embodiment the disease is cancer. In certain embodiments the method r comprises administering to the individual a therapeutically effective amount of at least one additional therapeutic agent, e.g., an anti-cancer agent if the disease to be treated is cancer. An “individual” according to any of the above embodiments may be a mammal, preferably a human.

In a further ment, the description includes a method for inducing lysis of a target cell, particularly a tumor cell. In one embodiment the method comprises contacting a target cell with a T cell activating bispecific n binding molecule of the description in the presence of a T cell, particularly a cytotoxic T cell. In a further embodiment, a method for inducing lysis of a target cell, particularly a tumor cell, in an individual is described. In one such embodiment, the method comprises administering to the individual an effective amount of a T cell activating bispecific antigen g molecule to induce lysis of a target cell. In one embodiment, an “individual” is a human.

In n embodiments the disease to be treated is a proliferative disorder, particularly cancer.

Non-limiting examples of cancers include bladder cancer, brain cancer, head and neck cancer, pancreatic cancer, lung cancer, breast cancer, n cancer, uterine cancer, cervical cancer, endometrial cancer, esophageal cancer, colon cancer, colorectal cancer, rectal cancer, gastric cancer, prostate cancer, blood cancer, skin cancer, squamous cell carcinoma, bone cancer, and kidney cancer. Other cell proliferation disorders that can be treated using a T cell activating bispecific antigen binding le of the t ption include, but are not limited to neoplasms located in the: abdomen, bone, , digestive system, liver, pancreas, peritoneum, endocrine glands (adrenal, yroid, pituitary, testicles, ovary, thymus, thyroid), eye, head and neck, nervous system al and peripheral), lymphatic system, pelvic, skin, soft tissue, spleen, thoracic region, and urogenital system. Also included are pre-cancerous conditions or s and cancer metastases. In certain embodiments the cancer is chosen from the group consisting of renal cell cancer, skin cancer, lung cancer, colorectal cancer, breast cancer, brain cancer, head and neck cancer. A skilled artisan readily recognizes that in many cases the T cell activating bispecific n binding molecule may not provide a cure but may only provide l benefit.

In some embodiments, a physiological change having some benefit is also considered therapeutically beneficial. Thus, in some embodiments, an amount of T cell ting bispecific antigen binding molecule that provides a physiological change is considered an "effective amount" or a "therapeutically ive amount". The t, t, or individual in need of treatment is lly a mammal, more specifically a human.

In some embodiments, an effective amount of a T cell activating bispecific antigen binding molecule of the description is administered to a cell. In other embodiments, a therapeutically effective amount of a T cell activating bispecific antigen binding molecule of the description is administered to an individual for the treatment of disease.

For the prevention or treatment of disease, the appropriate dosage of a T cell activating bispecific antigen binding molecule of the description (when used alone or in combination with one or more other additional therapeutic agents) will depend on the type of disease to be treated, the route of administration, the body weight of the patient, the type of T cell ting bispecific antigen g molecule, the severity and course of the disease, whether the T cell activating bispecific antigen binding molecule is administered for preventive or eutic purposes, previous or concurrent therapeutic interventions, the patient's clinical history and response to the T cell activating bispecific antigen binding molecule, and the discretion of the attending physician. The practitioner responsible for stration will, in any event, determine the concentration of active ingredient(s) in a composition and appropriate dose(s) for the dual subject. Various dosing schedules including but not limited to single or multiple administrations over s time-points, bolus administration, and pulse infusion are contemplated herein.

The T cell activating ific antigen binding molecule is suitably administered to the patient at one time or over a series of treatments. Depending on the type and severity of the e, about 1 µg/kg to 15 mg/kg (e.g. 0.1 mg/kg – 10 mg/kg) of T cell activating bispecific antigen binding molecule can be an initial candidate dosage for administration to the patient, whether, for example, by one or more te administrations, or by continuous infusion. One typical daily dosage might range from about 1 µg/kg to 100 mg/kg or more, ing on the factors mentioned above. For repeated strations over l days or longer, depending on the ion, the treatment would generally be sustained until a desired suppression of disease symptoms occurs. One exemplary dosage of the T cell activating bispecific antigen binding molecule would be in the range from about 0.005 mg/kg to about 10 mg/kg. In other non- limiting examples, a dose may also comprise from about 1 microgram/kg body weight, about 5 microgram/kg body , about 10 microgram/kg body weight, about 50 microgram/kg body weight, about 100 microgram/kg body weight, about 200 microgram/kg body weight, about 350 microgram/kg body weight, about 500 ram/kg body weight, about 1 milligram/kg body weight, about 5 milligram/kg body weight, about 10 milligram/kg body weight, about 50 milligram/kg body weight, about 100 milligram/kg body weight, about 200 milligram/kg body weight, about 350 milligram/kg body weight, about 500 milligram/kg body weight, to about 1000 mg/kg body weight or more per administration, and any range derivable therein. In nonlimiting examples of a derivable range from the numbers listed herein, a range of about 5 mg/kg body weight to about 100 mg/kg body , about 5 microgram/kg body weight to about 500 milligram/kg body weight, etc., can be administered, based on the numbers described above.

Thus, one or more doses of about 0.5 mg/kg, 2.0 mg/kg, 5.0 mg/kg or 10 mg/kg (or any combination thereof) may be stered to the patient. Such doses may be administered intermittently, e.g. every week or every three weeks (e.g. such that the patient es from about two to about twenty, or e.g. about six doses of the T cell activating bispecific antigen binding molecule). An initial higher loading dose, ed by one or more lower doses may be administered. However, other dosage regimens may be useful. The progress of this therapy is easily red by tional techniques and assays.

The T cell activating bispecific antigen binding molecules of the description will generally be used in an amount effective to achieve the intended purpose. For use to treat or prevent a disease condition, the T cell activating bispecific antigen binding molecules of the description, or ceutical compositions thereof, are administered or applied in a therapeutically effective amount. Determination of a therapeutically effective amount is well within the capabilities of those skilled in the art, especially in light of the detailed sure described .

For systemic administration, a therapeutically effective dose can be ted initially from in vitro assays, such as cell culture assays. A dose can then be formulated in animal models to achieve a circulating concentration range that includes the IC50 as determined in cell culture.

Such information can be used to more accurately determine useful doses in humans.

Initial dosages can also be estimated from in vivo data, e.g., animal models, using techniques that are well known in the art. One having ordinary skill in the art could readily optimize administration to humans based on animal data.

Dosage amount and al may be adjusted individually to provide plasma levels of the T cell activating bispecific antigen g molecules which are sufficient to maintain eutic effect. Usual t dosages for administration by injection range from about 0.1 to 50 mg/kg/day, typically from about 0.5 to 1 mg/kg/day. eutically effective plasma levels may be achieved by administering multiple doses each day. Levels in plasma may be measured, for e, by HPLC.

In cases of local administration or selective uptake, the effective local concentration of the T cell activating bispecific antigen binding molecules may not be related to plasma concentration. One having skill in the art will be able to optimize therapeutically effective local dosages without undue experimentation.

A therapeutically effective dose of the T cell activating bispecific antigen binding molecules described herein will generally provide therapeutic benefit without causing ntial toxicity.

Toxicity and therapeutic efficacy of a T cell activating bispecific antigen binding le can be determined by standard ceutical procedures in cell culture or experimental animals.

Cell culture assays and animal studies can be used to determine the LD50 (the dose lethal to 50% of a population) and the ED50 (the dose therapeutically effective in 50% of a population). The dose ratio between toxic and therapeutic effects is the therapeutic index, which can be expressed as the ratio LD50/ED50. T cell activating bispecific antigen binding molecules that exhibit large therapeutic indices are red. In one embodiment, the T cell activating bispecific antigen binding molecule ing to the t description exhibits a high therapeutic index. The data obtained from cell culture assays and animal studies can be used in formulating a range of dosages suitable for use in humans. The dosage lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage may vary within this range depending upon a variety of factors, e.g., the dosage form employed, the route of administration utilized, the condition of the subject, and the like. The exact formulation, route of administration and dosage can be chosen by the individual physician in view of the patient's condition (see, e.g., Fingl et al., 1975, in: The Pharmacological Basis of Therapeutics, Ch. 1, p. 1, orated herein by nce in its entirety).

The attending ian for patients treated with T cell activating ific antigen binding molecules of the description would know how and when to terminate, interrupt, or adjust administration due to toxicity, organ dysfunction, and the like. Conversely, the attending physician would also know to adjust treatment to higher levels if the clinical response were not adequate uding ty). The magnitude of an administered dose in the management of the disorder of interest will vary with the severity of the condition to be d, with the route of administration, and the like. The severity of the condition may, for example, be evaluated, in part, by standard prognostic evaluation methods. Further, the dose and perhaps dose frequency will also vary according to the age, body weight, and response of the individual patient.

Other Agents and Treatments The T cell activating bispecific n binding les of the description may be administered in combination with one or more other agents in therapy. For instance, a T cell activating bispecific antigen binding molecule of the description may be co-administered with at least one onal therapeutic agent. The term "therapeutic agent” encompasses any agent stered to treat a symptom or disease in an individual in need of such treatment. Such additional therapeutic agent may comprise any active ingredients suitable for the particular indication being treated, preferably those with complementary activities that do not adversely affect each other. In certain embodiments, an additional eutic agent is an immunomodulatory agent, a atic agent, an inhibitor of cell adhesion, a cytotoxic agent, an activator of cell apoptosis, or an agent that increases the sensitivity of cells to apoptotic inducers.

In a particular ment, the additional therapeutic agent is an anti-cancer agent, for example a microtubule tor, an antimetabolite, a topoisomerase inhibitor, a DNA intercalator, an alkylating agent, a hormonal therapy, a kinase inhibitor, a receptor antagonist, an activator of tumor cell apoptosis, or an giogenic agent.

Such other agents are suitably present in combination in amounts that are effective for the purpose intended. The effective amount of such other agents depends on the amount of T cell activating bispecific n binding molecule used, the type of disorder or treatment, and other factors discussed above. The T cell ting bispecific antigen binding molecules are generally used in the same dosages and with administration routes as described herein, or about from 1 to 99% of the dosages described herein, or in any dosage and by any route that is empirically/clinically determined to be appropriate.

Such combination ies noted above encompass combined administration (where two or more therapeutic agents are included in the same or separate compositions), and separate administration, in which case, administration of the T cell activating bispecific antigen binding molecule of the descritpion can occur prior to, simultaneously, and/or following, administration of the onal therapeutic agent and/or adjuvant. T cell activating bispecific antigen binding molecules of the description can also be used in combination with radiation therapy.

Articles of Manufacture In r embodiment of the description, an article of manufacture containing materials useful for the treatment, prevention and/or diagnosis of the disorders bed above is described. The article of manufacture comprises a container and a label or package insert on or associated with the container. Suitable containers e, for example, bottles, vials, syringes, IV solution bags, etc. The containers may be formed from a variety of materials such as glass or plastic. The ner holds a composition which is by itself or combined with another composition effective for treating, preventing and/or diagnosing the ion and may have a sterile access port (for example the container may be an intravenous solution bag or a vial having a stopper pierceable by a rmic injection needle). At least one active agent in the composition is a T cell activating bispecific antigen binding molecule of the description. The label or package insert tes that the composition is used for treating the condition of choice. Moreover, the article of manufacture may comprise (a) a first container with a composition contained therein, wherein the ition comprises a T cell activating bispecific antigen binding molecule of the description; and (b) a second container with a composition contained therein, wherein the composition ses a further cytotoxic or otherwise therapeutic agent. The article of manufacture in this embodiment of the description may further comprise a package insert indicating that the itions can be used to treat a particular condition. Alternatively, or additionally, the article of cture may further comprise a second (or third) ner comprising a pharmaceutically-acceptable buffer, such as bacteriostatic water for injection (BWFI), phosphate-buffered saline, Ringer's solution and dextrose on. It may further include other materials desirable from a commercial and user standpoint, ing other buffers, diluents, filters, needles, and syringes.

The following are examples of methods and compositions of the description. It is understood that various other embodiments may be practiced, given the general description included above.

General methods Recombinant DNA Techniques Standard methods were used to manipulate DNA as described in Sambrook et al., Molecular cloning: A laboratory manual; Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, 1989. The molecular biological reagents were used according to the manufacturers’ instructions. General information regarding the nucleotide ces of human immunoglobulins light and heavy chains is given in: Kabat, E.A. et al., (1991) Sequences of Proteins of Immunological Interest, 5th ed., NIH Publication No. 91-3242.

DNA Sequencing DNA sequences were determined by double strand sequencing.

Gene Synthesis d gene segments where required were either generated by PCR using riate templates or were synthesized by t AG (Regensburg, Germany) from synthetic oligonucleotides and PCR ts by automated gene synthesis. In cases where no exact gene sequence was available, oligonucleotide primers were designed based on sequences from closest homologues and the genes were isolated by RT-PCR from RNA originating from the appropriate tissue. The gene segments flanked by singular restriction endonuclease cleavage sites were cloned into standard cloning / sequencing vectors. The plasmid DNA was purified from transformed bacteria and concentration determined by UV spectroscopy. The DNA ce of the subcloned gene fragments was confirmed by DNA sequencing. Gene segments were designed with suitable restriction sites to allow oning into the respective sion vectors. All constructs were designed with a 5’-end DNA sequence coding for a leader peptide which targets proteins for secretion in eukaryotic cells.

Example 1 Preparation of T-cell bispecific (TCB) antibodies with and t charge modifications (anti-CD20 / anti-CD3) The following molecules were prepared in this example, tic illustrations thereof are shown in Figure 2: A. “2+1 IgG CrossFab, inverted” without charge modifications (CH1/CL exchange in CD3 binder) (Figure 2A, SEQ ID NOs 14-17) B. “2+1 IgG CrossFab, inverted” with charge modifications (VH/VL exchange in CD3 binder, charge modification in CD20 s) (Figure 2B, SEQ ID NOs 18-21) C. “2+1 IgG CrossFab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in CD20 binders) (Figure 2C, SEQ ID NOs 32, 19-21) D. “2+1 IgG CrossFab, inverted” without charge cations (VH/VL exchange in CD3 binder) e 2D, SEQ ID NOs 33, 15, 17, 21) E. “2+1 IgG CrossFab, inverted” without charge modifications (VH-CH1/VL-CL exchange in CD3 binder) (Figure 2E, SEQ ID NOs 34, 15, 17, 35) F. “2+1 IgG CrossFab, inverted” with charge modifications (VH/VL exchange in CD20 binders, charge modification in CD3 binder) (Figure 2F, SEQ ID NOs 36-39) G. “2+1 IgG CrossFab, inverted” with charge modifications and DDKK mutation in Fc region (VH/VL exchange in CD3 binder, charge modification in CD20 binders) (Figure 2G, SEQ ID NOs 40, 41, 20, 21) H. “1+1 CrossMab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in CD20 binder) (Figure 2H, SEQ ID NOs 42, 43, 20, 21) I. “1+1 CrossMab” with charge modifications (VH/VL exchange in CD3 binder, charge modification in CD20 binder, different CD20 ) (Figure 2I, SEQ ID NOs 43-45, 21) J. “2+1 IgG ab, inverted” with charge modifications 213E, 123R (VH/VL exchange in CD3 binder, charge modification in CD20 binder) (Figure 2J, SEQ ID NOs 69-71, 21) K. “2+1 IgG CrossFab, inverted” with charge modifications (VH/VL exchange and charge modification in CD3 binder) (Figure 2K, SEQ ID NOs 15, 17, 72, 73).

The variable region of heavy and light chain DNA sequences were subcloned in frame with either the constant heavy chain or the constant light chain pre-inserted into the respective recipient mammalian expression . Protein expression is driven by an MPSV promoter and a synthetic polyA signal ce is present at the 3’ end of the CDS. In addition each vector ns an EBV OriP sequence.

The molecules were produced by co-transfecting -EBNA cells growing in suspension with the mammalian expression s using polyethylenimine (PEI). The cells were ected with the corresponding expression vectors in a 1:2:1:1 ratio (A: “vector heavy chain (VH-CH1- VH-CL-CH2-CH3)” : “vector light chain (VL-CL)” : “vector heavy chain (VH-CH1-CH2- CH3)” : r light chain (VL-CH1)”; B, D, G, J, K: r heavy chain (VH-CH1-VL-CH1- CH2-CH3)” : “vector light chain (VL-CL)” : “vector heavy chain (VH-CH1-CH2-CH3)” : “vector light chain (VH-CL)”; C: r heavy chain (VL-CH1-VH-CH1-CH2-CH3)” : “vector light chain (VL-CL)” : “vector heavy chain (VH-CH1-CH2-CH3)” : “vector light chain (VHCL )”; E: “vector heavy chain (VH-CH1-VL-CL-CH2-CH3)” : “vector light chain (VL-CL)” : “vector heavy chain (VH-CH1-CH2-CH3)” : “vector light chain (VH-CH1)”; F: “vector heavy chain (VL-CH1-VH-CH1-CH2-CH3)” : “vector light chain (VH-CL)” : “vector heavy chain 1-CH2-CH3)” : “vector light chain (VH-CH1)”) or a 1:1:1:1 ratio (H, I: “vector heavy chain (VL-CH1-CH2-CH3)” : “vector light chain (VL-CL)” : “vector heavy chain (VH-CH1- 3)” : “vector light chain (VH-CL)”).

For transfection, HEK293 EBNA cells were cultivated in suspension serum free in Excell culture medium containing 6 mM amine and 250 mg/l G418. For the production in 600 ml tubespin flasks (max. g volume 400 ml) 600 million HEK293 EBNA cells were seeded 24 hours before transfection. For transfection, cells were centrifuged for 5 min at 210 x g, and supernatant was ed by 20 ml pre-warmed CD CHO medium. Expression vectors are mixed in 20 ml CD CHO medium to a final amount of 400 μg DNA. After addition of 1080 μl PEI solution (2.7 μg/ml) the mixture was vortexed for 15 s and subsequently ted for 10 min at room temperature. Afterwards cells were mixed with the DNA/PEI solution, transferred to a 600 ml tubespin flask and incubated for 3 hours at 37°C in an incubator with a 5% CO2 atmosphere.

After incubation, 360 ml Excell + 6 mM amine + 5 g/L Pepsoy + 1.0 mM VPA medium was added and cells were cultivated for 24 hours. One day after transfection 7% Feed 1 (Lonza) was added. After 7 days cultivation atant was collected for purification by centrifugation for 20 - 30 min at 3600 x g (Sigma 8K centrifuge), the solution was sterile filtered (0.22 mm filter) and sodium azide in a final concentration of 0.01% w/v was added. The solution was kept at 4°C.

The concentration of the ucts in the e medium was determined by ProteinA-HPLC.

The basis of separation was binding of Fc-containing molecules on ProteinA at pH 8.0 and step elution from pH 2.5. There were two mobile phases. These were Tris (10 mM) - glycine (50 mM) - NaCl (100 mM) buffers, identical except that they were adjusted to different pHs (8 and 2.5).

The column body was an Upchurch 2x20 mm pre-column with an internal volume of ~63 μl packed with POROS 20A. 100 μl of each sample was injected on equilibrated material with a flow rate of 0.5 ml/min. After 0.67 minutes the sample was eluted with a pH step to pH 2.5.

Quantitation was done by determination of 280 nm ance and calculation using a standard curve with a concentration range of human IgG1 from 16 to 166 mg/l.

The secreted protein was ed from cell e atants by affinity tography using Protein A affinity chromatography, followed by a size exclusion chromatographic step.

For affinity tography supernatant was loaded on a HiTrap ProteinA HP column (CV=5 mL, GE Healthcare) equilibrated with 25 ml 20 mM sodium phosphate, 20 mM sodium citrate, pH 7.5. Unbound protein was removed by washing with at least 10 column volumes 20 mM sodium phosphate, 20 mM sodium citrate, 0.5 M sodium chloride, pH 7.5, followed by an additional wash step using 6 column s 10 mM sodium phosphate, 20 mM sodium citrate, 0.5 M sodium chloride, pH 5.45. The column was washed subsequently with 20 ml 10 mM MES, 100 mM sodium chloride, pH 5.0, and target protein was eluted in 6 column volumes 20 mM sodium e, 100 mM sodium chloride, 100 mM glycine, pH 3.0. Protein solution was neutralized by adding 1/10 of 0.5 M sodium phosphate, pH 8.0. Target protein was trated and filtrated prior to loading on a HiLoad Superdex 200 column (GE Healthcare) equilibrated with 20 mM histidine, 140 mM sodium de, 0.01% Tween-20, pH 6.0. Molecule A had to be purified by an additional preparative size exclusion chromatography (SEC) step to achieve a final monomer content of 100%. Therefore, fractions with high monomer content from the first size exclusion step were pooled, concentrated and again loaded on a HiLoad Superdex 200 column (GE Healthcare). This additional purification step was not necessary for the other molecules (depending on the side product profile, however, g of fractions and therefore ry after the first size exclusion chromatography was different for these les).

Purity and molecular weight of the molecules was analyzed after the first purification step (Protein A affinity chromatography) by SDS-PAGE in the absence of a reducing agent and staining with Coomassie (SimpleBlue™ SafeStain, Invitrogen). The NuPAGE® Pre-Cast gel system (Invitrogen, USA) was used according to the manufacturer’s instruction (4-12% Tris- Acetate gels or 4-12% Bis-Tris).

The protein concentration of purified protein samples was determined by measuring the optical density (OD) at 280 nm, using the molar extinction coefficient calculated on the basis of the amino acid sequence.

Purity and molecular weight of molecules after the final purification step were analyzed by CESDS analyses in the presence and absence of a ng agent. The Caliper LabChip GXII system (Caliper lifescience) was used according to the manufacturer’s instruction. 2 μg sample was used for analyses.

The aggregate content of dy samples was analyzed using a TSKgel G3000 SW XL analytical size-exclusion column (Tosoh) in 25 mM K2HPO4, 125 mM NaCl, 200 mM L- arginine monohydrocloride, 0.02 % (w/v) NaN3, pH 6.7 g buffer at 25°C.

All molecules were produced and purified following the same method (except for molecule A having been subjected to an additional SEC step, as indicated . le A showed a high ate content after the first preparative size exclusion chromatography. The content of aggregates after this purification step could not be determined since there was no baseline separation of high molecular weight impurities and the ric fraction. To obtain 100% monomeric material an additional preparative size exclusion tography step was necessary. Molecule B was 100% monomeric after one preparative size exclusion tography.

The concentration in the supernatant was higher for molecule A, but the final yield was (due to the high aggregate content) 2.3 fold lower than for molecule B (Table 2).

The final purity shown by CE-SDS analyses was higher for molecule B than for molecule A (Table 3, Figure 3A and B). Figure 3M and 3N show chromatograms of the SEC cation step (preparative SEC) wherein molecule A has a broad peak as compared to molecule B, indicating that the preparation of molecule A loaded on the SEC is not homogenous while the preparation of molecule B is largely monomeric.

Molecule C could be produced with high titer but compared to molecule B the final recovery was lower due to a high t of side products that could not be completely removed by the applied chromatography methods (Table 2; Table 3; Figure 3B and J, and Figure 3C and K). As shown in Figure 3B and 3K, the SDS-PAGE analysis after the Protein A purification step showed no side product for molecule B, while the preparation of molecule C contains some side products appearing at an apparent molecular weight of 100 kDa.

Molecule D differs from molecule B only in the absence of the charged residues in the anti- CD20 Fabs. This molecule could also be produced transiently with high titer but as already described for molecule C the final y shown on analytical SEC (98% monomer for molecule D, vs. 100% monomer for molecule B) and the recovery was lower than for molecule B due to a high content of side products (Table 2; Table 3; Figure 3B and J and Figure 3D and L). As shown in Figure 3J and 3L, the GE analysis after the Protein A purification step showed no side product for molecule B, while the preparation of molecule D contains some side products appearing at an apparent molecular weight of 66 kDa and 40 kDa. Figure 3N and 3O show chromatograms of the SEC purification step (preparative SEC) wherein molecule D has a broad peak as compared to molecule B, indicating that the preparation of molecule D loaded on the SEC is not homogenous while the ation of molecule B is largely monomeric.

Also the titer of the production of molecule E was high but the final product ned still low molecular weight impurities as shown by analytical SEC and capillary electrophoresis (Table 2; Table 3; Figure 3E).

In contrast to molecule B, molecule F has the VH-VL exchange on the Fab of the tumor target binding moiety whereas the charge modifications have been introduced in the anti-CD3 Fab.

This molecule could be produced with high titers too, but the final recovery was low due to side products. For the anti-CD20 / anti-CD3 TCB the format with charge modifications in the anti- CD20 Fab is able with regard to production and purification.

Molecule G is a molecule with charge modifications in the Fc region (“DD” = K392D; K409D in one of the subunits of the Fc domain, “KK” = D356K; D399K in the other of the subunits of the Fc domain (EU numbering), replacing the “knob into hole” mutation. The generation of bispecific molecules is fostered by the introduction of two aspartic acid residues on one heavy chain and two lysine residues in the second heavy chain e 2G). This molecule could be produced with high titer but the final product has still some high molecular and low molecular weight impurities shown by analytical SEC and capillary electrophoresis (Table 2; Table 3) whereas the side products could be completely removed for the same molecule ng the “knob into hole” mutation (molecule B).

Molecule I, which differs from molecule H in its CD20 binder, showed a higher aggregate content after the final preparative size exclusion chromatography compared to molecule H. The final purity shown by CE-SDS analyses was higher for molecule H than for the molecule I (Table 3; Figure 3H and I). Also the recovery for molecule H was 40% higher than for molecule I (Table 2). This result shows that the quality of the le is also dependent on the antibody used in the T cell bispecific format.

The productions of molecule J and le K had a good starting titer which led to a good yield. r, the final recovery of around 20% for both molecules was well below the 48% achieved with molecule B (Table 2). Both molecules are similar in final quality with >99% monomer content (Table 2). The purity in non-reduced CE-SDS is better for molecule J (which lacks the charge modifications at position 124 of the CL domain and on 147 of the CH1 domain) with nearly 99% compared to molecule K g charge modifications and a VL-VH exchange in the CD3 binder) with 90% (Table 3, Figure 3N and 3O). Molecule J showed some precipitation during the concentration step after ty chromatography. Molecule K has charge modifications in the CD3 binding CrossFab rather than the CD20 binding Fabs. This has an impact on the final quality as shown by CE-SDS (Table 3, Figure 3O). The difference in quality is mostly visible after the first purification step on SDS-Page (Figure 3P, 3Q). le K contains more side products at 150 kDa and 70 kDa (half molecules and constructs probably missing light chains) than molecule J. Both les have the same thermal stability which is similar to molecule B (Table 4).

For the D20 / anti-CD3 TCB the “inverted” version with charge modifications on the anti CD20 Fab (molecule B) is the format that could be produced with the highest recovery and final quality.

TABLE 2. Summary of production and purification of anti-CD20 / anti-CD3 TCB molecules with and without charge cations.

Analytical SEC App. purity ined Titer Recovery Yield Molecule (HMW/Monomer/ by LC-MS [%] (mg/l) [%] (mg/l) LMW) [%] A 16.7 7.2 1.2 0/100/0 * 85-90 * B 5.5 48.2 2.8 0/100/0 93 C 25 12.9 3.24 4/93/3 nd D 55 9.8 5.42 2/98/0 nd E 30.5 3.3 0.99 0/96.3/3.7 nd F 57 11.8 6.43 3.4/96.6/0 nd G 56 21 11.8 3.75/92.3/3.43 nd H 29 9.2 2.66 2/98/0 nd I 52.5 5.8 3.05 2.7/95.3/2 nd J 77 18 17.4 0.7/99.3/0 nd K 71.5 21.8 15.5 0/99.7/0.3 nd * final product, after two SEC steps TABLE 3. CE-SDS analyses (non-reduced) of anti-CD20 / anti-CD3 TCB les with and without charge modifications.

Molecule Peak # Size [kDa] Purity [%] A 1 34.13 0.49 2 55.10 0.58 3 58.89 0.97 4 152.30 1.76 165.95 2.25 6 177.64 7.75 7 186.15 14.06 8 194.17 18.37 9 201.68 53.77 B 1 160.09 0.57 2 180.70 1.62 3 194.42 97.81 C 1 131.12 0.82 2 141.45 3.45 3 182.86 2.39 4 192.1 13.5 198.13 79.84 D 1 207.04 100 E 1 176.36 0.67 2 196.54 14.36 3 209.22 84.97 F 1 30.41 0.55 2 65.04 1.33 3 198.80 2.05 4 203.10 7.94 213.93 88.12 G 1 96.50 1.67 2 208.46 96.77 3 216.11 1.55 H 1 131.98 1.13 2 140.64 1.96 3 153.02 92.24 4 161.24 4.67 I 1 55.75 1.88 2 158.62 50.78 3 178.6 46.14 4 218.64 1.2 J 1 186.5 1.4 2 198.2 98.6 K 1 164.7 4 2 182.4 6 3 200.1 90 Molecular weight confirmation by LC-MS analyses Deglycosylation To confirm homogeneous preparation of the molecules, the final protein solution was analyzed by LC-MS analyses. To remove heterogeneity introduced by carbohydrates, the constructs were treated with PNGaseF. For this purpose, the pH of the protein on was adjusted to pH 7.0 by adding 2 μl 2 M Tris to 20 µg protein with a concentration of 0.5 mg/ml. 0.8 µg PNGaseF was added and incubated for 12 h at 37°C.

LC-MS analysis - On line detection The LC-MS method was performed on an Agilent HPLC 1200 coupled to a TOF 6441 mass spectrometer nt). The chromatographic separation was performed on a Macherey Nagel Polysterene column; RP1000-8 (8 µm particle size, 4.6 x 250 mm; cat. No. ). Eluent A was 5% acetonitrile and 0.05% (v/v) formic acid in water, eluent B was 95% acetonitrile, 5% water and 0.05% formic acid. The flow rate was 1 ml/min, the separation was med at 40°C and with 6 µg (15 µl) protein sample obtained with the treatment bed before.

Time (min.) %B 0.5 15 60 12.5 100 14.5 100 14.6 15 16 15 16.1 100 During the first four s the eluate was directed into the waste to prevent salt contamination of the mass spectrometer. The ESI-source was running with a drying gas flow of 12 l/min, a temperature of 350°C and a nebulizer re of 60 psi. The MS spectra were ed using a fragmentor voltage of 380 V and a mass range 700 to 3200 m/z in positive ion mode. MS data are acquired by the instrument software from 4 to 17 minutes.

The preparation of molecule A had about 10-15% les with mispaired light chains and traces of free or linked light chains. The preparation of molecule B had traces of les comprising two CD3 light chains. Impurities such as free light chain or linked light chain could not be detected (Table 2).

Thermal stability by Static Light Scattering Thermal stability was red by Static Light Scattering (SLS) and by measuring the intrinsic protein scence in response to applied temperature stress. 30 µg of filtered protein sample with a protein concentration of 1 mg/ml was applied in duplicate to Optim 2 (Avacta Analytical Ltd; GB). The temperature was ramped from 25 to 85°C at 0.1 °C/min, with the radius and total scattering intensity being collected. For determination of intrinsic protein scence the sample was d at 295 nm and emission was collected between 266 and 473 nm.

Thermal stability was determined for all molecules, results are shown in Table 4. The aggregation temperature (TAgg) determined by dynamic light scattering and the g temperature (TM) measured by protein fluorescence after applying a temperature gradient was comparable for all molecules with TAgg ranging from 54-58°C and TM ranging from 56-60°C (Table 4).

TABLE 4. Thermal stability of anti-CD20 / anti-CD3 TCB molecules with and without charge modifications.

Molecule TAggregation [°C] TM [°C] A 54.4 55.9 B 54.3 56.4 C 56 59 D 56 59 E 56 60 F 58 60 G 57 59 H 55 56 I 53 57 J 54 55 K 54 55 g to CD3 and CD20 of anti-CD3 / anti-CD20 TCB antibodies The binding to CD3 of anti-CD3 / D20 T cell bispecific (TCB) antibodies with or without charge modifications (molecules “A” and “B” above) was measured using human CD3- expressing Jurkat cells. The binding to CD20 was determined using human CD20-expressing Z- 138 cells. sion cells were harvested, washed once with PBS, and viability and cell density determined using Vicell. The suspension cells were resuspended at 2 x 106 cells/ml in FACS buffer. 100 µl of the cell suspension were seeded into a 96 well round bottom plate. Each step was performed at 4°C. The plates were centrifuged at 360 x g for 5 min and the atant was removed. dy dilutions were prepared in 1 % BSA. 30 µl of the diluted anti-CD3 / anti-CD20 TCB antibodies or FACS buffer were added to the wells and the cells were incubated for 30 min at 4°C. After the incubation, 120 µl FACS buffer were added per well, the plate was centrifuged for 5 min at 350 x g, and the supernatant was removed. The washing step was repeated once. 30 µl pre-diluted secondary antibody was added per well, as indicated in the plate layout. The plates were incubated for further 30 min at 4°C. After the incubation, 120 µl FACS buffer were added per well, the plates were centrifuged for 5 min at 350 x g, and the atant was removed. The washing step was repeated once for all plates but the plate with Jurkat cells, which were fixed directly after this one washing step. The cells were fixed using 100 µl BD Fixation buffer per well (#BD Biosciences, 554655) at 4°C for 20-30 min. Cells were re- suspended in 80 µl/well FACS buffer for the FACS measurement using a BD FACS CantoII.

The result of this experiment is shown in Figure 4.

Tumor cell lysis and CD4+ and CD8+ T cell activation upon T cell-mediated killing of CD20-expressing tumor target cells induced by anti-CD3 / anti-CD20 TCB antibodies T ediated killing of target cells and activation of T cells induced by anti-CD3 / anti-CD20 TCB antibodies with or without charge modifications (molecules “A” and “B” above) was ed on Z-138 and Nalm-6 tumor cells. Human PBMCs were used as effectors and killing as well as T cell activation detected 22 h after incubation with the bispecific antibody. Briefly, target cells were harvested, washed, and plated at density of 30 000 cells/well using roundbottom 96-well . Peripheral blood mononuclear cells ) were ed by aque y centrifugation of fresh blood from healthy human donors. Fresh blood was diluted with sterile PBS and layered over Histopaque gradient (Sigma, ). After centrifugation (450 x g, 30 minutes, room temperature), the plasma above the PBMC-containing interphase was discarded and PBMCs transferred in a new falcon tube subsequently filled with 50 ml PBS. The mixture was fuged (400 x g, 10 minutes, room temperature), the supernatant discarded and the PBMC pellet washed twice with sterile PBS (centrifugation steps 350 x g, 10 minutes). The resulting PBMC tion was counted automatically (ViCell) and kept in RPMI1640 medium containing 10% FCS and 1% L-alanyl-L-glutamine rom, K0302) in cell incubator (37°C, 5% CO2) until further use (no longer than 24 h). For the killing assay, the antibodies were added at indicated concentrations (range of 1000 pM – 0.1 pM in triplicates). PBMCs were added to target cells at the final E:T ratio of 6:1. After the incubation, plates were centrifuged at 420 x g for 4 min and 50 µl/well was transferred into fresh 96-flat bottom plates for LDH detection. LDH detection was performed using a Cytotoxicity Detection Kit (Roche #11644793001) according to the instructions of the manufacturer. The remaining cells were washed with PBS containing 0.1% BSA. Surface staining for CD8 (APCCy7 antihuman CD8, Biolegend #301016), CD4 (FITC anti-human CD4, Biolegend # 300506), CD69 (BV421 anti-human CD69 Biolegend #310930) and CD25 (PECy7 anti-human CD25 Biolegend #302612) was performed according to the suppliers’ indications. After 30 min at 4°C cells were washed twice with 150 l PBS containing 0.1% BSA and fixed using 100 µl/well 2 % PFA.

The measurement was performed using a BD FACS CantoII.

The result of this experiment is shown in Figure 5, 6 and 7. Both molecules y comparable activity in terms of tumor cell lysis and T cell activation.

B cell depletion and CD4+ and CD8+ T cell activation upon T cell-mediated killing of healthy human B cells induced by anti-CD3 / anti- CD20 TCB antibodies in human whole blood Human whole blood from a healthy donor was incubated with anti-CD3 / anti-CD20 TCB antibodies with or without charge modifications (molecules “A” and “B” above) at ted concentrations (range of 50000 pM – 1 pM in triplicates). After 22 h, the blood was mixed and µl were collected for staining with 20 µl FACS antibody mix containing CD8 (APCCy7 antihuman CD8, Biolegend #301016), CD4 (FITC anti-human CD4, Biolegend # 300506), CD69 (BV421 anti-human CD69 Biolegend #310930) and CD25 (PECy7 anti-human CD25, Biolegend #302612), CD22 (APC anti-human CD22, Biolegend #302510) and CD45 Cy5.5 antihuman CD45, Biolegend #304028). After 15 minutes incubation at room ature, the blood was fixed with FACS Lysing solution (BD, #349202) and analyzed by flow cytometry. B cell depletion was calculated based on the ratio of B cell s and CD4+ T cell numbers setting the untreated samples to 0% B cell depletion.

The result of this experiment is shown in Figure 8 and 9. Both molecules display comparable activity in terms of B cell depletion in the whole blood and T cell activation.

Binding of anti-CD3 / anti-CD20 TCB antibody to human CD20- and CD3-expressing target cells The binding of the anti-CD3 / anti-CD20 TCB antibody shown as le “B” above was tested on human CD20-expressing Diffuse Large-Cell B Cell Lymphoma (DLBCL) cell line (WSU DLCL2, 0.5-1 x 106 CD20 binding sites) and CD3-expressing immortalized T lymphocyte line (Jurkat). y, cells were ted, counted, checked for ity and resuspended at 1.5 x 106 cells/ml in FACS buffer (PBS 0.1% BSA). 100 µl of cell suspension (containing 0.15 x 106 cells) were incubated in round-bottom 96-well plate for 30 min at 4°C with sing concentrations of the CD20 TCB (50 pM - 200 nM), washed twice with cold PBS 0.1% BSA, re-incubated for further 30 min at 4°C with diluted PE-conjugated AffiniPure F(ab’)2 Fragment goat anti-human IgG Fcg Fragment ic secondary antibody (Jackson Immuno Research Lab PE #109170), washed twice with cold PBS 0.1% BSA, fixed by addition of 2 % PFA and analyzed by FACS using a FACS CantoII are FACS Diva) excluding dead cells from analysis by FSC/SSC gating.

Results are shown in Figure 10A ng to WSU DLCL2 cells) and Figure 10B ng to Jurkat cells). Binding curves and the EC50 values related to binding were calculated using GraphPadPrism5. EC50 values were 0.98 nM (bivalent g to CD20-expressing WSU DLCL2 cells) and approximately 12.5 nM (monovalent binding to CD3-expressing Jurkat cells).

Binding of anti-CD3 / anti-CD20 TCB antibody to human and cynomolgus monkey CD20- and CD3-expressing target cells The crossreactivity of the D3 / anti-CD20 TCB dy shown as molecule “B” above was evaluated by assessing binding to human and cynomolgus monkey CD20-expressing B cells and CD3-expressing CD4 and CD8 T cells. Briefly, heparinized human and cynomolgus monkey blood from healthy donors was used to isolate PBMCs by density centrifugation. Isolated PBMCs were d, checked for viability and resuspended at 4 x 106 cells/ml in FACS buffer (100 μl PBS 0.1% BSA). 100 µl of cell suspension (containing 0.4 x 106 cells) were plated into 96-well_U-bottom plate and centrifuged (420 x g, 4 min). After removal of the supernatants, PBMCs were ted for 30 min at 4°C with increasing concentrations of the CD20 TCBAlexaFlour488 (200 pM - 200 nM), washed twice with cold PBS 0.1% BSA, re-incubated for further 30 min at 4°C with human/cynomolgus cross-reactive antibodies: anti-CD19 (in house, clone 8B8)-AlexaFluor647, anti-CD4 (BD, #552838, clone L200)-PerCPCy5.5 and anti-CD8 (BD, #555367, clone RPA-T8)-PE. After 30 min, PBMCs were washed twice with cold PBS 0.1% BSA and treated with FACS Lysing solution (BD, # 349202) followed by FACS is using a FACS CantoII (Software FACS Diva). Binding curves were obtained using adPrism5.

Results are shown in Figure 11A (binding to human and cynomolgus monkey B cells), Figure 11B (binding to human and cynomolgus monkey CD4 T cells) and Figure 11C (binding to human and cynomolgus monkey CD8 T cells). The EC50 values related to binding to CD20- expressing B cells, calculated using GraphPadPrism5, were 4.8 nM (human B cells) and 3.3 nM (cynomolgus B cells).

Tumor cell lysis mediated by different anti-CD20 / anti-CD3 TCB antibody s Tumor cell lysis ed by different anti-CD20 / anti-CD3 TCB antibody formats (molecules “B”, “A” “C” and “H” shown above) was assessed on Z138 cells (mantle cell ma, 0.06- 0.23 x 106 CD20 binding sites). Human PBMCs were used as effectors and tumor lysis was detected at 21-24 h of incubation with the different bispecific antibody formats. Briefly, target cells were harvested, washed, and plated at density of 50 000 cells/well using om 96-well plates. Peripheral blood mononuclear cells (PBMCs) were prepared by Histopaque density centrifugation of healthy human blood. Fresh blood was diluted with sterile PBS and layered over Histopaque gradient (Sigma, #H8889). After centrifugation (450 x g, 30 minutes, room temperature, w/o brake), the plasma above the PBMC-containing interphase was discarded and PBMCs transferred in a new falcon tube subsequently filled with 50 ml of PBS. The mixture was fuged (350 x g, 10 minutes, room temperature), the supernatant discarded and the PBMC pellet washed with sterile PBS (300 x g, 10 minutes). The ing PBMC population was counted automatically (ViCell) and stored in RPMI1640 medium containing 10% FCS and 1% L-alanyl-L-glutamine (Biochrom, K0302) at 37°C, 5% CO2 in cell incubator until r use (no longer than 24 h). For the tumor lysis assay, the antibodies were added at the indicated concentrations (range of 0.1 pM – 1 nM in triplicates). PBMCs were added to target cells at final E:T ratio of 6:1. Tumor cell lysis was assessed after 21-24 h of incubation at 37°C, 5% CO2 by quantification of LDH released into cell atants by apoptotic/necrotic cells (LDH detection kit, Roche Applied Science, #11 644 793 001). Maximal lysis of the target cells (= 100%) was achieved by incubation of target cells with 1% Triton X-100. Minimal lysis (= 0%) refers to target cells ubated with effector cells without bispecific uct.

Figure 12 shows that different CD20 TCB antibody formats d a strong and target-specific lysis of CD20+ target cells. Panel A shows that the “CD20 TCB_2+1_with charges, ed” (molecule “B” shown above) displays comparable activity to the “CD20 TCB_2+1_no charges, inverted” (molecule “A” shown above) and that both are more potent than the “CD20 TCB_1+1_with charges” format (molecule “H” shown above). Panel B shows that “CD20 TCB_2+1_with charges, inverted” (molecule “B” shown above) is more potent than “CD20 TCB_2+1_with charges, classical” format (molecule “C” shown above). The EC50 values related to killing assays, calculated using adPrism5 are given in Table 5.

TABLE 5. EC50 values (pM) of tumor cell lysis ed by different anti-CD20 / anti-CD3 TCB antibody formats evaluated using CD20-expressing Z138 tumor target cells.

Panel CD20 dy format EC50 [pM] A CD20 TCB_2+1_with charges, inverted 2.18 (molecule B) A CD20 TCB_2+1_no charges, inverted 0.76 (molecule A) A CD20 TCB_1+1_with charges 17.54 (molecule H) B CD20 TCB_2+1_with charges, inverted 0.96 ule B) B CD20 TCB_2+1_with charges, classical 43.34 (molecule C) Tumor cell lysis and subsequent T cell activation mediated by different anti-CD20 / anti- CD3 TCB antibody formats Tumor cell lysis mediated by different anti-CD20 / anti-CD3 TCB antibody formats (molecules “B” and “H” shown above) was further assessed on Z138 cells e cell lymphoma) using human PBMCs derived from three different healthy donors as well as on a broader panel of DLBCL lines including OCI Ly-18 (0.06-0.2 x 106 CD20 binding sites), Ramos (0.1-0.4 x 106 CD20 binding sites), SU-DHL-5 0.21 x 106 CD20 binding sites), SU-DHL-8 (CD20 binding sites below detection limit of the assay), Toledo (0.02 x 106 CD20 binding sites) and U2932 0.4 x 106 CD20 binding sites) cell lines. Tumor cell harvest, PBMC isolation, and assay conditions were identical to the ones described in the previous example. E:T ratio for the assays shown in Figures 13 A-C was 6:1, for the assay shown in Figure 13D it was 3:1. Tumor cell lysis was assessed after 21 h of tion at 37°C, 5% CO2 by quantification of LDH released into cell supernatants by apoptotic/necrotic cells (LDH detection kit, Roche Applied Science, #11 644 793 001). For the assessment of T cell activation ing upon tumor cell lysis, PBMCs were transferred to a round-bottom 96-well plate, centrifuged at 400 x g for 5 min and washed twice with PBS containing 0.1% BSA. Surface staining for CD8 (APCCy7 antihuman CD8 Biolegend, #301016), CD4 (FITC anti-human CD4, Biolegend #300506) and CD25 (PECy7 anti-human CD25 Biolegend 2) was performed according to the suppliers’ indications. Cells were washed twice with 150 µl/well PBS containing 0.1% BSA and fixed using 2 % PFA or FACS Lysing solution (BD, # 349202). Samples were analyzed at BD FACS CantoII.

Figure 13 shows that the “CD20 TCB_2+1_with charges, inverted” antibody format ule “B” shown above) is more potent than “CD20 TCB_1+1” antibody format ule “H” shown above) as assessed by detection of both tumor cell lysis (Panels A, D) and T cell activation (Panel B, C) using PBMCs from different . The EC50 values related to tumor lysis and T cell activation of Z138 cells are given in Table 6a. The EC50 values related to tumor lysis assays of a panel of DLBCL cell lines are given in Table 6b. The EC50 values were calculated using GraphPadPrism5.

TABLE 6a. EC50 values (pM) of tumor cell lysis and T cell tion mediated by anti-CD20 / anti-CD3 TCB dies using CD20-expressing Z138 tumor cells.

CD20 antibody format EC50 [pM] 24 h ge of 3 donors) CD20 TCB_2+1_with charges, inverted (tumor lysis) 1.6 ule B) CD20 TCB_1+1 (tumor lysis) 751 (molecule H) CD20 TCB_2+1_with charges, inverted (CD8 T cell activation) 2.2 (molecule B) CD20 TCB_1+1 (CD8 T cell activation) 174.8 (molecule H) CD20 TCB_2+1_with charges, inverted (CD4 T cell activation) 1.2 (molecule B) CD20 TCB_1+1 (CD4 T cell activation) 122 (molecule H) TABLE 6b. EC50 values (pM) of tumor lysis of a panel of DLBCL tumor cell lines mediated by anti-CD20 / anti-CD3 TCB antibodies.

EC50 [pM] 24 h of CD20 TCB_2+1_with CD20 TCB_1+1 tumor lysis charges, inverted (molecule H) (molecule B) Ocly-18 0.3 250.4 Ramos n.d. n.d.

SU-DHL-5 1.2 69.7 SU-DHL-8 0.5 218.9 Toledo n.d. 120.2 U2932 0.9 72.7 B cell ion in human whole blood mediated by different anti-CD20 / anti-CD3 TCB antibody formats Normal B cell depletion mediated by different anti-CD20 / anti-CD3 TCB antibody formats (molecules “B” and “H” shown above) and by obinutuzumab was further assessed using fresh human blood from healthy eers. Briefly, fresh blood was collected in n-containing syringes. Blood aliquots (180 μL/well) were placed in 96-deep well plates, supplemented with TCB or dy dilutions (10 μL/well + 10 μL/well PBS) and incubated for 24 h at 37°C in 5 % CO2 in a humidified cell incubator. After incubation, blood was mixed by pipetting up and down before 35 μL blood aliquots were transferred in 96-well U-bottom plates and incubated with scent D45 (APC, Biolegend, #304037), anti-CD4 (PerCPCy5.5, BD, #552838), anti- CD8 (APCCy7, Biolegend, #301016), anti-CD19 (PE, Biolegend, #302208), anti-CD25 (PECy7, Biolegend, #302612) and anti-CD69 (BV421, Biolegend, #310930) in total 55 μL volume for flow cytometry. After 15 min incubation at room temperature (in the dark) 180 μL/well of FACS lysis solution (BD Biosciences) was added to e erythrocytes and to fix cells prior to flow cytometry.

Figure 14 shows that the “CD20 TCB_2+1_with charges, inverted” (molecule “B” above) is more potent in depleting normal B cells than both obinutuzumab a) and “CD20 TCB_1+1” with charges (molecule “H” above).

TABLE 7. EC50 values (pM) of B cell depletion in normal human whole blood mediated by different CD20-targeting antibodies.

CD20-targeting dies EC50 [pM] 24 h CD20 TCB_2+1_with charges, inverted (molecule B) 13.2 Obinutuzumab (Gazyva®) 79.2 CD20 TCB_1+1 (molecule H) 3753 Activation of T cells assessed by quantification of the intensity of CD3 downstream signaling using Jurkat-NFAT er assay The capacity of different anti-CD20 / anti-CD3 TCB antibody formats to induce T cell crosslinking and subsequently T cell activation was assessed using co-cultures of CD20-expressing tumor target cells and Jurkat-NFAT er cells (a CD3-expressing human acute lymphatic leukemia reporter cell line with a NFAT promoter, GloResponse Jurkat NFAT-RE-luc2P, a #CS176501). Upon simultaneous binding of anti-CD20 / anti-CD3 TCB to CD20 antigen (expressed on tumor cells) and CD3 antigen (expressed on Jurkat-NFAT reporter cells), the NFAT promoter is activated and leads to expression of active firefly luciferase. The intensity of luminescence signal (obtained upon addition of luciferase substrate) is proportional to the ity of CD3 activation and signaling. Jurkat-NFAT reporter cells grow in suspension and were cultured in 40, 2g/l glucose, 2 g/l NaHCO3, 10 % FCS, 25 mM HEPES, 2 mM L- glutamin, 1 x NEAA, 1 x sodium-pyruvate at 0.1 – 0.5 mio cells per ml, 200 µg per ml hygromycin. For the assay, tumor target cells (Z138) were harvested and viability determined using . 50 µl/well of diluted antibodies or medium (for controls) was added to target cells. 20 000 cells/well were plated in a flat-bottom, white-walled 96-well-plate 98, Greiner bio-one). Subsequently, Jurkat-NFAT reporter cells were harvested and viability assessed using ViCell. Cells were resuspended at 2 mio cells/ml in cell culture medium without hygromycin B and added to tumor cells at 0.1 x 106 cells/well (50 µl/well) to obtain a final E:T of 5:1 and a final volume of 100 µl per well. Cells were incubated for 6 h at 37°C in a humidified incubator.

At the end of incubation time, 100 µl/well of ONE-Glo solution (1:1 ONE-Glo and assay medium volume per well) were added to wells and incubated for 10 min at room temperature in the dark. Luminescence was detected using WALLAC Victor3 ELISA reader (PerkinElmer2030), sec/well as detection time.

Figure 15 shows that “CD20 TCB_2+1_with charges, inverted” (molecule “B” above) leads to stronger T cell activation and signaling downstream of CD3 than “CD20 1” ule “H” above).

TABLE 8. EC50 values (pM) of CD3 activation detected using Jurkat-NFAT reporter cells.

CD20 antibody format EC50 [pM] CD20 TCB_2+1_with charges, inverted (molecule B) 28.98 CD20 TCB_1+1 (molecule H) 1001 Single dose PK of anti-CD20 / anti-CD3 TCB in healthy NOG mice A single dose pharmacokinetic study (SDPK) was performed to evaluate re of D20 / anti-CD3 TCB molecule “B” (hereinafter called “CD20 TCB”) during efficacy studies (Figure 16). An i.v. bolus administration of 0.5 mg/kg was administered to NOG mice and blood samples were taken at selected time points for pharmacokinetic tion. A generic assay was used for measuring total concentrations of the CD20 TCB. The ation range of the standard curve for the CD20 TCB was 0.78 to 50 ng/ml, where 15 ng/ml is the lower limit of quantification (LLOQ).

A biphasic decline was observed with a beta half-life of 10 days (non-compartmental analysis) and clearance of 8 mL/d/kg partmental model). The half-life and clearance was as expected as compared to a normal untargeted IgG (Table 9).

Phoenix v6.2 from Pharsight Ltd was used for PK analysis, modelling and simulation.

TABLE 9. Pharmacokinetic parameters of a 0.5 mg/kg i.v. bolus administration of CD20 TCB in NOG mice.

Half-life 10 days Clearance 7.9 mL/d/kg Cmax 9.4 ug/mL AUC 1554 h*ug/mL In vivo B-cell depletion ty of D20 / anti-CD3 TCB Peripheral B-cell depletion activity of CD20 TCB was tested in fully humanized NOD/Shiscid /IL-2Rγnull (NOG) mice.

Fully humanized NOG mice at 14 weeks of age, bearing physiological levels of circulating human B- and T- cells (Hayakawa J. et al. (2009), Stem Cells 27(1), 175–182), were treated either with vehicle (n = 7) or with CD20 TCB (n = 6) at the dose of 0.5 mg/kg administered intravenously (i.v.) once per week. As shown on the study design in Figure 17, mice were bled for B cell and T- cell analysis one and three days after the first therapeutic injection (D1, D3), and three days after the second (D10), at which time point the study was terminated. At the latter time point, spleens were also harvested for B- cell and T- cell analysis Mice were screened 4 days before therapeutic ion (D-4) as baseline reference for circulating B- and T- cell counts. Figure 18 shows B- and T-cell counts analysed by ex vivo flow cytometry in blood of vehicle (left panel) and CD20 TCB (right panel)-treated mice at the different time . Results demonstrate that circulating B-cells were very ently depleted already one day after CD20 TCB injection, and their number remained undetectable for the whole study duration. On the contrary, circulating T-cell count only transiently dropped at D1 after therapeutic injection, ed to baseline levels at D3, and ed stable for the whole study duration. T-cell activation status was also analysed in blood of treated mice at D3 and D10 after first therapeutic injection, by means of ex vivo flow cytometry using different T-cell surface markers and the proliferation marker Ki67 (Figure 19). T-cells from CD20 TCB–treated mice showed an activated phenotype at D3 after therapeutic injection (upper panel), with up-regulation of the activation markers CD25, 4-1BB, PD-1 and me-B (GZB) in both CD4 and CD8 T-cell compartments, compared to T-cells from vehicle control. T-cells from treated mice also expressed higher levels of the proliferation marker Ki67. At D10 after first therapeutic injection, most of the T-cell activation markers had ed to baseline levels with the ion of GZB and PD-1, which were still expressed at higher levels compared to vehicle control.

Figure 20 shows the results of B-cell and T-cell analyses done on spleens of vehicle and CD20 TCB-treated mice at study termination (D10). CD20 TCB treatment mediated a very efficient B cell depletion also in this secondary lymphoid organ (Figure 20A), while T-cell counts showed levels comparable to vehicle control (Figure 20B). The T cell activation status (Figure 20C) was similar to that ed in blood, with higher expression of GZB and PD-1 in splenic T cells of treated mice compared to vehicle control.

Altogether these results demonstrate that CD20 TCB treatment can e a very efficient depletion of peripheral B-cells already one day after therapy injection, with B-cells remaining undetectable until study termination (three days after second therapeutic ion). B-cells are also efficiently depleted in spleen of treated mice. B-cell depletion activity is paralleled by a transient T-cell activation in blood of treated animals, which returns to baseline levels three days after eutic injection, with the exception of GZB and PD-1 activation markers, which remain sed at a higher level compared to untreated controls.

Anti-tumor ty of anti-CD20 / anti-CD3 TCB in WSU-DLCL2 model Anti-tumor activity of CD20 TCB was tested in NOG mice bearing the human diffuse large B cell lymphoma cell line WSU-DLCL2 and transferred with human peripheral mononuclear cells (PBMC). Briefly, female NOG mice were injected sub-cutaneously (s.c.) with 1.5 x 106 L2 cells (originally obtained from the European Collection of Cell Culture). When e tumor volume reached 200 mm3, mice received intra-peritoneal injection of human PBMC (10 x 106 cells per mouse) as source human T-cells. Two days later, mice received CD20 TCB therapy i.v. at a dose of 0.5 mg/kg administered once a week. As depicted in Figure 21, CD20 TCB shows a potent anti-tumor activity, with almost complete tumor regression observed at study termination (day 34).

Example 2 Preparation of “2+1 IgG CrossFab, inverted” T-cell bispecific antibody with and without charge modifications (anti-BCMA / anti-CD3) tic illustrations of the molecules prepared in this example are shown in Figure 22. The anti-BCMA/anti-CD3 “2+1 IgG CrossFab, inverted” molecule without charge modifications (referred to in this example as “83A10-TCB”) comprises the amino acid sequences of SEQ ID NOs 22-25, the anti-BCMA/anti-CD3 “2+1 IgG CrossFab, inverted” molecule with charge modifications (referred to in this example as “83A10-TCBcv”) comprises the amino acid ces of SEQ ID NOs 26-29.

For the generation of BCMAxCD3 bispecific antibody vectors, the IgG1 derived bispecific molecules consist at least of two antigen binding moieties capable of binding ically to two distinct antigenic determinants CD3 and BCMA. The antigen binding moieties are Fab nts composed of a heavy and a light chain, each comprising a variable and a nt region. At least one of the Fab fragments was a fab” fragment, n VH and VL were ged. The exchange of VH and VL within the Fab fragment s that Fab fragments of ent icity do not have identical domain ements. The bispecific molecule design was monovalent for CD3 and bivalent for BCMA where one Fab fragment was fused to the N- terminus of the inner CrossFab (2+1). The bispecific molecule contained an Fc part in order for the molecule to have a longer ife. The molecules were produced by co-transfecting HEK293 EBNA cells growing in suspension with the mammalian expression vectors using polyethylenimine (PEI). For preparation of 2+1 CrossFab-IgG constructs, cells were transfected with the corresponding expression vectors in a 1:2:1:1 ratio (“vector Fc(knob)” : “vector light chain” : “vector light chain ab” : “vector heavy chain-CrossFab ”).

For bispecific antibodies, introduction of a replacement/exchange in one binding arm “Crossfab” y reduces the side-products but the preparation is not completely free of side-products (described in detail in WO2009/080252 and Schaefer, W. et al, PNAS, 108 (2011) 11187-1191).

Thus, to further reduce side-products caused by the mismatch of a light chain against a first antigen with the wrong heavy chain against the second antigen and to improve the yield of the bispecific antibody, an additional approach is applied to the molecule by introducing substitutions of charged amino acids with the opposite charge at specific amino acid positions in the CH1 and CL domains in the constant domain CL of the first light chain under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K), arginine (R)), and wherein in the constant domain CH1 of the first heavy chain under a) the amino acid at position 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat); or ii) in the constant domain CL of the second light chain under b) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or Histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K), arginine (R)), and wherein in the constant domain CH1 of the second heavy chain under b) the amino acid at positions 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or ic acid (D) (numbering according to Kabat).

For the production of the bispecific antibodies, ific antibodies were expressed by transient co-transfection of the respective mammalian expression vectors in HEK293-EBNA cells, which were cultivated in suspension, using polyethylenimine (PEI). One day prior to transfection, the HEK293-EBNA cells were seeded at 1.5 Mio viable cells/mL in Ex-Cell medium supplemented with 6 mM of L-Glutamine. For every mL of final production volume, 2.0 Mio viable cells were centrifuged (5 minutes at 210 x g). The supernatant was aspirated and the cells resuspended in 100 µL of CD CHO medium. The DNA for every mL of final production volume was prepared by mixing 1 µg of DNA (Ratio heavy chain: modified heavy chain: light chain: ed light chain = 1:1:2:1) in 100 µL of CD CHO . After addition of 0.27 µL of PEI solution (1 mg/mL) the mixture was ed for 15 seconds and left at room temperature for 10 minutes. After 10 minutes, the resuspended cells and DNA/PEI e were put together and then transferred into an appropriate container which was placed in a shaking device (37°C, % CO2). After a 3 hours incubation time 800 µL of Ex-Cell Medium, supplemented with 6 mM L-Glutamine, 1.25 mM valproic acid and 12.5% Pepsoy (50 g/L), was added for every mL of final Production volume. After 24 hours, 70 µL of Feed (SF40, Lonza) was added for every mL of final production volume. After 7 days or when the cell ity was equal or lower than 70%, the cells were separated from the supernatant by centrifugation and sterile filtration. The antibodies were purified by an affinity step and one or two ing steps, being cation exchange chromatography and size exclusion chromatography. When required, an additional polishing step was used.

For the affinity step the supernatant was loaded on a protein A column (HiTrap Protein A FF , 5 mL, GE Healthcare) equilibrated with 6 CV 20 mM sodium phosphate, 20 mM sodium citrate, pH 7.5. After a g step with the same buffer the antibody was eluted from the column by step elution with 20 mM sodium phosphate, 100 mM sodium chloride, 100 mM Glycine, pH 3.0.

The fractions with the desired antibody were immediately neutralized by 0.5 M Sodium Phosphate, pH 8.0 (1:10), pooled and concentrated by centrifugation. The concentrate was e filtered and processed further by cation ge chromatography and/or size exclusion chromatography.

For the cation exchange chromatography step the concentrated n was diluted 1:10 with the n buffer used for the affinity step and loaded onto a cation exchange colume (Poros 50 HS, Applied Biosystems). After two washing steps with the equilibration buffer and a washing buffer resp. 20 mM sodium phosphate, 20 mM sodium citrate, 20 mM TRIS, pH 5.0 and 20 mM sodium phosphate, 20 mM sodium citrate, 20 mM TRIS, 100 mM sodium de pH 5.0 the protein was eluted with a gradient using 20 mM sodium phosphate, 20 mM sodium citrate, 20 mM TRIS, 100 mM sodium chloride pH 8.5. The fractions containing the d antibody were pooled, concentrated by centrifugation, sterile filtered and processed further a size exclusion step.

For the size exclusion step the concentrated protein was injected in a XK16/60 HiLoad Superdex 200 column (GE Healthcare), and 20 mM Histidine, 140 mM Sodium Chloride, pH 6.0 with or without Tween20 as formulation buffer. The fractions containing the monomers were pooled, concentrated by centrifugation and sterile filtered into a sterile vial. ination of the antibody concentration was done by measurement of the absorbance at 280 nm, using the theoretical value of the absorbance of a 0.1% solution of the dy. This value was based on the amino acid sequence and calculated by GPMAW software (Lighthouse data).

Purity and monomer content of the final protein preparation was determined by CE-SDS (Caliper LabChip GXII system (Caliper Life Sciences)) resp. HPLC (TSKgel G3000 SW XL analytical size exclusion column (Tosoh)) in a 25 mM potassium phosphate, 125 mM Sodium chloride, 200 mM L-arginine monohydrochloride, 0.02 % (w/v) Sodium azide, pH 6.7 buffer.

To verify the molecular weight of the final protein preparations and confirm the homogeneous preparation of the molecules final protein solution, liquid chromatography-mass spectometry (LC-MS) was used. A deglycosylation step was first performed. To remove heterogeneity introduced by carbohydrates, the constructs were treated with PNGaseF (ProZyme). Therefore, the pH of the protein solution was adjusted to pH7.0 by adding 2 µl 2 M Tris to 20 µg protein with a concentration of 0.5 mg/ml. 0.8 µg PNGaseF was added and incubated for 12 h at 37 °C.

The LC-MS online detection was then med. LC-MS method was performed on an Agilent HPLC 1200 coupled to a TOF 6441 mass spectrometer (Agilent). The chromatographic separation was performed on a Macherey Nagel Polysterene column; RP1000-8 (8 µm le size, 4.6 x 250 mm; cat. No. 719510). Eluent A was 5 % itrile and 0.05 % (v/v) formic acid in water, eluent B was 95 % itrile, 5 % water and 0.05 % formic acid. The flow rate was 1 ml/min, the tion was performed at 40°C and 6 µg (15 µl) of a protein sample ed with a treatment as described before.

Time (min.) %B 0.5 15 60 12.5 100 14.5 100 14.6 15 16 15 16.1 100 During the first 4 minutes, the eluate was directed into the waste to protect the mass spectrometer from salt contamination. The ESI-source was running with a drying gas flow of 12 l/min, a temperature of 350°C and a nebulizer pressure of 60psi. The MS spectra were acquired using a fragmentor voltage of 380 V and a mass range 700 to 3200 m/z in positive ion mode using. MS data were acquired by the instrument software from 4 to 17 minutes.

Figure 23 depicts the CE-SDS (non-reduced) graphs of the final protein preparations after different methods of purification for 83A10-TCB and 83A10-TCBcv dies. Protein A (PA) affinity chromatography and size ion chromatographic (SEC) purification steps applied to 83A10-TCB antibody resulted in a purity of <30% and 82.8% of r content (A). When additional purifications steps including cation exchange chromatography (cIEX) and a final size exclusion chromatographic (re-SEC) steps were applied to the final protein preparations in (A), the purity was increased to 93.4% but the monomer t remained the same and the yield was significantly reduced to 0.42 mg/L. However, when specific charge modifications were applied to 83A10 anti-BCMA Fab CL-CH1, namely 83A10-TCBcv antibody, a or production/purification profile of the TCB molecule, as demonstrated by a purity of 95.3%, monomer t of 100% and yield of up to 3.3 mg/L, could y be observed even when PA + cIEX + SEC purification steps were applied (C) in comparison to (B) with a production/purification profile showing a 7.9-fold lower yield and 17.2% lower monomer content despite including an additional re-SEC purification step.

A head-to-head production run to compare the production/purification profile of 83A10-TCB vs. 83A10-TCBcv antibodies was then ted to further evaluate the advantages of the CL-CH1 charge cations applied to the antibodies. As depicted in Figure 24, ties of 83A10- TCB and 83A10-TCBcv antibodies were measured side-by-side and compared after each purification steps 1) PA affinity tography only (A, B), 2) PA affinity chromatography then SEC (C, D) and 3) PA ty chromatography then SEC then cIEX and re-SEC (E, F).

The CE-SDS (non-reduced) graphs of the final protein solutions after the respective methods of purification for 83A10-TCB and 83A10-TCBcv antibodies are demonstrated in Figure 24. As shown in Figures 24A and 24B, ements with applying the charge variants to the TCB antibody were already observed after purification by PA affinity chromatography only. In this head-to-head study, PA affinity chromatography purification step applied to 83A10-TCB antibody ed in a purity of 61.3%, a yield of 26.2 mg/L and 63.7% of r content (24A). In comparison, when 83A10-TCBcv antibody was purified by PA affinity chromatography all the properties were improved with a better purity of 81.0%, a better yield of 51.5 mg/L and 68.2% of monomer content (24B). When an additional SEC purifications step was applied to the final protein preparations as seen in s 24A and 24B, TCB gained a purity of 69.5%, a yield of 14.1 mg/L and 74.7% of monomer content as compared to 83A10-TCBcv with improved purity and monomer content of up to 91.0% and 83.9% respectively, and a yield of 10.3 mg/L. Even though the yield was slightly less (i.e. 27% less) for 83A10-TCBcv than for 83A10-TCB in this particular experiment, the percentage of correct molecule was much better for 83A10-TCBcv than for 83A10-TCB, respectively 90% vs. 40-60%, as measured by LC-MS. In the third head-to-head comparison, 83A10-TCB and 83A10-TCBcv final protein preparations from Figures 24C and 24D were pooled with approximately 1 L (equivolume) of respective final protein preparations from another cation batch (same production) following PA affinity chromatography purification step only. The pooled protein preparations were then being r ed by cIEX and SEC purification s. As ed in Figures 24E and 24F, ement of the production/purification profile of the TCB antibody with the charge variants was consistently ed when compared to TCB antibody without charge variant. After several steps of cation methods (i.e. PA +/- SEC + cIEX + SEC) were used to purify 83A10-TCB antibody, only 43.1% purity was reached and 98.3% of monomer content could be achieved but to the detriment of the yield which was reduced to 0.43 mg/L. The percentage of t molecule as measured by LC-MS was still poor with 60-70%.

At the end, the quality of the final protein preparation was not acceptable for in vitro use. In stark contrast, when the same multiple purification steps with the same logy were applied to 83A10-TCBcv antibody, 96.2% purity and 98.9% of monomer content were reached as well as 95% of correct molecule as measured by LC-MS. The yield however was also greatly reduced to 0.64 mg/L after cIEX purification step. The results show that better purity, higher monomer content, higher percentage of correct molecule and better yield can be achieved with 83A10-TCBcv antibody only after two standard purification steps i.e. PA affinity chromatography and SEC (Figure 24D) while such properties could not be achieved with 83A10- TCB even when onal purification steps were applied (Figure 24E).

Table 10 summarizes the properties of 83A10-TCB as ed to 83A10-TCVcv following PA purification step. Table 11 summarizes the properties of 83A10-TCB as compared to 83A10- TCVcv following PA and SEC purification steps. Table 12 summarizes the properties of 83A10- TCB as compared to 83A10-TCVcv ing PA and SEC plus PA alone then cIEX and re- SEC purification steps. For Tables 10 to 12, the values in bold highlight the superior property as ed between TCB vs. 83A10-TCVcv. With one exception which may not be representative, all the production/purification parameters and values resulting from the 3 head- to-head ison experiments were superior for 83A10-TCBcv as compared to 83A10-TCB.

The overall results clearly demonstrate that advantages in production/purification features could be achieved with applying CL-CH1 charge modifications to TCB antibodies and that only two purification steps (i.e PA affinity chromatography and SEC) were required to achieve already high y protein preparations with very good pability properties.

TABLE 10. Production/purification profile of anti-BCMA/anti-CD3 T cell bispecific antibodies following protein A affinity chromatography purification step. 83A10-TCB 83A10-TCBcv Purity (%) 61.3 81.0 Yield (mg/L) 26.2 51.5 Amount (mg) 24.3 50.2 Monomer (%) 63.7 68.2 t molecule by n.d. n.d LC-MS (%) TABLE 11. Production/purification profile of anti-BCMA/anti-CD3 T cell bispecific antibodies following protein A affinity chromatography and size exclusion chromatography purification steps. 83A10-TCB 83A10-TCBcv Purity (%) 69.5 91.0 Yield (mg/L) 14.1 10.3 Amount (mg) 13.1 10.0 Monomer (%) 74.7 83.9 Correct molecule by 40-60 90 LC-MS (%) TABLE 12. Production/purification profile of anti-BCMA/anti-CD3 T cell bispecific antibodies following 1.a) protein A affinity chromatography and size exclusion chromatography and 1.b) protein A affinity chromatography only pooled together then 2) cation exchange chromatography and 3) final size exclusion chromatography cation steps.

TCB 83A10-TCBcv Purity (%) 43.1 96.2 Yield (mg/L) 0.43 0.64 Amount (mg) 0.73 1.27 Monomer (%) 98.3 98.9 Correct molecule by 60-70% >95% LC-MS (%) Binding of anti-BCMA/anti-CD3 T-cell bispecific antibodies to BCMA-positive multiple myeloma cell lines (flow cytometry) Anti-BCMA/anti-CD3 TCB antibodies (83A10-TCB, 13A4-TCBcv) were analyzed by flow cytometry for binding to human BCMA on BCMA-expressing NCI-H929 cells (ATCC® CRL- . MKN45 (human gastric adenocarcinoma cell line that does not express BCMA) was used as negative control. Briefly, cultured cells were harvested, counted and cell viability was ted using ViCell. Viable cells were then adjusted to 2 x 106 cells per ml in BSA-containing FACS Stain Buffer (BD Biosciences). 100 µl of this cell suspension were further aliquoted per well into a round-bottom 96-well plate and ted with 30 µl of the anti-BCMA antibodies or corresponding IgG control for 30 min at 4°c. All Anti-BCMA/anti-CD3 TCB antibodies (and TCB controls) were titrated and analyzed in final concentration range between 1 – 300 nM. Cells were then fuged (5 min, 350 x g), washed with well FACS Stain Buffer (BD Biosciences), resuspended and ted for an additional 30 min at 4°C with fluorochrome- conjugated PE-conjugated AffiniPure F(ab’)2 Fragment goat anti-human IgG Fc Fragment ic (Jackson Immuno ch Lab; 109170). Cells were then washed twice with Stain Buffer (BD Biosciences), fixed using 100 ul BD Fixation buffer per well (#BD Biosciences, 554655) at 4°C for 20 min, resuspended in 120 µl FACS buffer and analyzed using BD FACS CantoII. As depicted in Figure 25, the mean fluorescence intensity of anti-BCMA/anti-CD3 TCB antibodies were plotted in function of dy concentrations; (A) 83A10-TCB on H929 cells and MKN45 cells, (B) 83A10-TCBcv on H929 cells and MKN45 cells. When applicable, EC50 were calculated using Prism GraphPad la, CA, USA) and EC50 values denoting the antibody concentration required to reach 50% of the maximal binding for the binding of 83A10- TCB and 83A10-TCBcv to H929 cells are summarized in Table 13. Figure 25C shows that 83A10-TCB and 83A10-TCBcv bind to H929 cells in a concentration-dependent manner and with similar potency. Such results are expected since 83A10-TCB and TCBcv molecules share identical CDR sequences on the respective VL and VH variable domains. DP47-TCB control antibody did not bind to BCMA-positive H929 myeloma cells as measured by a lack of increase in median fluorescence intensity. In a second head-to-head comparison experiment, 83A10-TCB and 83A10-TCBcv were evaluated for binding to BCMA-positive H929 cells and lack of binding to BCMA/CD3-negative MKN45 cells. As ed in Figure 25D, 83A10-TCB and 83A10-TCBcv bind to BCMA-positive H929 cells in a concentration-dependent manner and with similar potency. EC50 values for the binding of 83A10-TCB and 83A10-TCBcv to H929 cells for this second ment are summarized in Table 14.

TABLE 13. EC50 values for binding of CMA/anti-CD3 TCB antibodies to H929 cells iment 1).

Anti-BCMA/anti-CD3 TCB molecules EC50 (nM) EC50 (µg/ml) 83A10-TCB 9.8 1.9 83A10-TCBcv 14.5 2.8 TABLE 14. EC50 values for binding of anti-BCMA/anti-CD3 TCB antibodies to H929 cells (Experiment 2).

Anti-BCMA/anti-CD3 TCB molecules EC50 (nM) EC50 ) 83A10-TCB 16.9 3.25 83A10-TCBcv 14.5 2.8 Redirected T-cell cytotoxicity of BCMA-high expressing H929 myeloma cells induced by anti-BCMA/anti-CD3 T cell bispecific antibodies (LDH release assay) Anti-BCMA/anti-CD3 TCB antibodies were also analyzed for their potential to induce T cell- mediated apoptosis in BCMA-high expressing myeloma cells upon crosslinking of the construct via binding of the antigen binding moieties to BCMA on cells. Briefly, human BCMA- expressing H929 multiple myeloma target cells were harvested with Cell Dissociation Buffer, washed and resuspended in RPMI supplemented with 10% fetal bovine serum (Invitrogen).

Approximately 30,000 cells per well were plated in a round-bottom l plate and the respective dilution of the antibody uct was added for a desired final concentration (in triplicates); final concentrations ranging from 0.1 pM to 10 nM. For an appropriate comparison, all TCB constructs and controls were adjusted to the same molarity. Human total T cells (effector) were added into the wells to obtain a final effector : target (E:T) ratio of 5:1. When human PBMC were used as effector cells, a final E:T ratio of 10:1 was used. ve control groups were represented by effector or target cells only. As a positive control for the activation of human pan T cells, 1 μg/ml PHA-M (Sigma #L8902) was used. For ization, maximal lysis of the H929 MM target cells (= 100%) was determined by tion of the target cells with a final concentration of 1% Triton X-100, inducing cell death. Minimal lysis (= 0%) was represented by target cells co-incubated with effector cells only, i.e. without any T cell bispecific antibody. After 20-24 h incubation at 37°C, 5% CO2, LDH release from the apoptotic/necrotic myeloma target cells into the supernatant was then measured with the LDH detection kit (Roche Applied Science), following the manufacturer’s instructions. The percentage of LDH release was plotted against the concentrations of anti-BCMA/anti-CD3 T cell bispecific antibodies in concentration-response curves. When applicable, the EC50 values were measured using Prism software (GraphPad) and determined as the TCB antibody concentration that results in 50% of m LDH release. As shown in Figure 26, CMA/anti-CD3 TCB antibodies ((A,B) 83A10-TCB, (C,D) TCBcv) induced a concentration-dependent killing of BCMA- positive H929 myeloma cells as measured by LDH e. The killing of H929 cells was specific since CB control dy which does not bind to BCMA-positive target cells did not induce LDH release, even at the highest tration of 1 nM (A). Even though EC50 values were not measurable with the use of Prism (GraphPad) statistical software for 83A10- TCB (A, B) and 83A10-TCBcv (C, Experiment 1), the magnitude of EC50 values could be approximately estimated to low lar range potency for both non-charged and charged TCB molecules. In a second experiment, the effect of 83A10-TCBcv was evaluated in the redirected T-cell killing assay and an EC50 value could be measured to 1.5 pM. The authors could not exclude that the slightly lower EC50 value (slightly better potency) could be due to blood donor variability. However, the magnitude of potency to kill H929 cells was definitely in the low picomolar range. The overall results suggest that 83A10-TCB (without charge variant) vs. 83A10-TCBcv (with charge variant) shows similar biological properties in ased assays.

TABLE 15. EC50 values and tions for redirected T-cell killing of H929 cells induced by anti-BCMA/anti-CD3 TCB antibodies.

Anti-BCMA/anti-CD3 TCB molecules EC50 (pM) EC50 (µg/ml) Low pM range 83A10-TCB (Experiment 1) Single digit (approx. <20) Low pM range 83A10-TCB (Experiment 2) Single digit (approx. <20) Low pM range 83A10-TCBcv (Experiment 1) Single digit (approx. <20) 83A10-TCBcv (Experiment 2) 1.5 0.3 Example 3 Preparation of “2+1 IgG CrossFab, inverted” T-cell bispecific dy with charge modifications Her2 / anti-CD3) and “2+1 IgG CrossFab” T-cell bispecific antibody with charge cations (anti-Her3 / anti-CD3) A tic illustration of the molecules prepared in this example is shown in Figure 27. The anti-Her2/anti-CD3 “2+1 IgG CrossFab, inverted” molecule with charge modifications (referred to in this example as “Her2 TCB”) ses the amino acid sequences of SEQ ID NOs 21, 52, 53 and 54. The anti-Her3/anti-CD3 “2+1 IgG CrossFab” molecule with charge modifications (referred to in this example as “Her3 TCB”) comprises the amino acid sequences of SEQ ID NOs 21, 55, 56 and 57.

The les were ed, purified and analyzed as described in Example 1 above (with a single preparative SEC step).

Both molecules could be purified with high final y shown by ical size exclusion chromatography and CE-SDS (Table 16, 17). Although recovery of the Her2 TCB in this preparation was lower ed to the Her3 TCB, the protein was almost pure after the two purification steps (Protein A and SEC). CE-SDS analysis shows only 1.18% low molecular weight impurity at approximately 164 kDa (Table 17). The species detected at 187.28 kDa corresponds to the target molecule without N-linked glycosylation on the Fc domain (this species is commonly detected by CE-SDS for human IgG1 after production in eukaryotic cells).

Her3 TCB could be purified with good recovery. The final quality was superior to the Her2 TCB comparing the final monomer content. Also the CE-SDS shows 100% target protein, assuming the peak detected at 192.05 kDa corresponds to the non-glycosylated Fc-species.

For both preparations no product-related low molecular weight impurities such as free light chains (expected molecular weight at 25 kDa), zed light chains as it can occur by introducing only a CH1-CL exchange on one light chain (expected molecular weight at 50 kDa) or molecules with missing or non-covalently linked light chains (expected molecular weight at 125 kDa, 150 kDa or 175 kDa) have been ed by CE-SDS or analytical size exclusion tography.

TABLE 16. Summary of production and purification of anti-Her2 / anti-CD3 and anti-Her3 / anti-CD3 TCB molecules with charge cations.

Analytical SEC Molecule Titer [mg/l] Recovery [%] Yield [mg/l] (HMW/Monomer/LMW) [%] Her2 TCB 45 1.8 1 3.3/96.7/0 Her3 TCB 72 12.7 11.42 0/100/0 TABLE 17. CE-SDS analyses educed) of anti-Her2 / anti-CD3 and anti-Her3 / anti-CD3 TCB molecules with charge modifications.

Molecule Peak # Size [kDa] Purity [%] Her2 TCB 1 163.99 1.18 2 187.28 1.30 3 200.81 97.52 Her3 TCB 1 192.05 19.36 2 198.57 80.64 Binding of Her2 TCB and Her3 TCB to cells Jurkat suspension cells were harvested, washed with FACS buffer (PBS + 0.1% BSA) once and viability was determined by ViCell.

Adherent KPL-4 tumor cells (kindly provided by J. Kurebayashi, Kawasaki Medical School, Japan) were harvested with Cell Dissociation Buffer (Gibco Invitrogen) and washed with FACS buffer once, before viability was determined by . 0.2 million cells were plated per well of a round-bottom 96-well plate and the plates were centrifuged for 4 min at 400 g. Then 25 µl per well of the TCB dilutions in FACS buffer was added to the cells. The cells were incubated for 30 min in the fridge. Afterwards the cells were washed twice with 150 μl FACS buffer per well. µl of appropriately diluted secondary antibody (FITC conjugated AffiniPure F(ab')₂ Fragment, Goat Anti-Human IgG, ₂ fragment specific, Jackson ImmunoResearch) were added per well and the plates were stained for further 30 min at 4°C in the dark.

The plates were washed twice with 150 µl FACS buffer per well and resuspended in 150 µl FACS buffer. The analysis was performed using a BD FACS CantoII, equipped with FACS Diva re. Median scence values (MFI) were plotted against the concentration of the TCB molecules.

As shown in Figure 29, both TCBs show concentration-dependent good binding to their tive target antigens on cells. tion of human CD8+ T effector cells, after T cell-mediated lysis of human tumor cells, induced by the Her3 TCB CD8+ T effector cells of a classical tumor cell lysis experiment (as described below) with Her3 TCB using an effector-to-target ratio (E:T) of 10:1 and an incubation time of 48h were evaluated for the percentage of CD69-positive cells.

Briefly, after incubation, PBMCs were transferred to a round-bottom 96-well plate, centrifuged at 350 x g for 5 min and washed twice with PBS containing 0.1% BSA. Surface staining for CD8 (Biolegend #300908) and CD69 (BioLegend #310904) was med according to the ers’ indications. Cells were washed twice with 150 l PBS containing 0.1% BSA and fixed for min at 4°C using 100 µl/well 1% PFA. After centrifugation, the samples were resuspended in 200 µl/well PBS 0.1% BSA and analyzed at FACS CantoII (Software FACS Diva).

As shown in Figure 30, the Her3 TCB induces cross-linkage of T cells and tumor cells (KPL-4) via its respective targeting moieties and induces activation of T cells in a concentrationdependent manner.

-NFAT activation assay The capacity of the Her2 TCB and the Her3 TCB to induce T cell cross-linking and subsequently T cell activation, was assessed using tures of tumor antigen positive target cells (KPL-4) and Jurkat-NFAT reporter cells (a pressing human acute lymphatic leukemia er cell line with a NFAT promoter, ponse Jurkat NFAT-RE-luc2P, Promega #CS176501). Upon simultaneous binding of the TCB molecule to human Her2, tively human Her3, antigen (expressed on tumor cells) and CD3 n (expressed on Jurkat-NFAT reporter , the NFAT promoter is activated and leads to expression of active firefly luciferase. The intensity of luminescence signal ned upon addition of luciferase substrate) is proportional to the intensity of CD3 activation and signaling.

For the assay, KPL-4 human tumor cells were harvested with Cell Dissociation Buffer (Gibco Invitrogen) and viability was determined using ViCell. 20 000 cells/well were plated in a ttom , white-walled 96-well-plate (Greiner bio-one) and diluted TCBs or medium (for controls) was added. Subsequently, Jurkat-NFAT reporter cells were harvested and viability assessed using ViCell. Cells were resuspended in cell culture medium and added to tumor cells to obtain a final E:T of 2.5:1 (for Her2 TCB) or 5:1 (for Her3 TCB) as indicated, and a final volume of 100 µl per well. Cells were incubated for 5 h at 37°C in a humidified incubator. At the end of the incubation time, 100 µl/well of ONE-Glo solution (Promega, #E6120) (1:1 ONE-Glo and assay medium volume per well) were added to wells and incubated for 10 min at room temperature in the dark. Luminescence was detected using WALLAC Victor3 ELISA reader (PerkinElmer2030), 5 sec/well as detection time.

As depicted in Figure 31, both TCB molecules induce T cell cross-linking via CD3 and subsequently T cell tion. The Her3 TCB is slightly more potent on KPL-4 cells, which might be explained by a higher level of Her3 over Her2 on these target cells.

Tumor cell lysis induced by Her2 TCB and Her3 TCB Tumor cell lysis of Her2- or Her3-expressing tumor target cells induced by the respective TCB molecules was assessed, using human peripheral blood mononuclear cells (PBMCs) as effectors, at an E:T of 10:1. Tumor cell lysis was determined by measurement of released LDH into the supernatants after 24 h and 48 h upon incubation with the TCBs, as indicated.

Human PBMCs were ed from fresh blood or from a buffy coat. Briefly, blood was diluted 2:1 (fresh blood) or 3:1 (buffy coat) with PBS. About 30 ml of the blood/PBS mixture was layered on 15 ml of aque ) and centrifuged for 30 min at 450 x g without brake at RT. The lymphocytes were collected with a 10 ml pipette into 50 ml tubes ning PBS. The tubes were filled up to 50 ml with PBS and centrifuged 10 min at 350 g. The supernatant was discarded, the pellet re-suspended in 50 ml PBS and centrifuged for 10 min at 300 x g. The washing step was repeated once. The cells were pended in RPMI containing 10% FCS and 1% GlutaMax (Life Technologies) and stored at 37°C, 5% CO2 in the incubator until assay start (not longer than 24h).

Target cells were harvested with Trypsin/EDTA, washed, and plated at density of 30 000 cells/well using flat-bottom 96-well plates. Cells were left to adhere ght in a humidified incubator. On the day of the assay, the assay plates were centrifuged at 350 x g for 5 min and the medium was aspirated. 100 µl per well of assay medium were added.

The TCBs were added at indicated concentrations (range of 0.001 pM – 1 nM for the Her3 TCB, and 0.01 pM – 100 nM for the Her2 TCB, in triplicates). PBMCs were added to target cells at the final E:T ratio of 10:1. Target cell killing was assessed after 24 h and 48 h of incubation by quantification of LDH (lactate dehydrogenase) released into cell supernatants by tic/necrotic cells (LDH detection kit, Roche Applied Science, #11 644 793 001). Maximal lysis of the target cells (= 100%) was achieved by incubation of target cells with 1% Triton X- 100. Minimal lysis (= 0%) refers to target cells co-incubated with effector cells without bispecific antibody. The EC50 values were calculated using GraphPadPrism5.

In r experiment, tumor cell lysis was determined by Caspase 3/7 activity after 6.5h by measuring luminescence in a microplate reader (5 s reading time per wells).

For the determination of Caspase 3/7 activity, KPLCaspase-3/7 GloSensor target cells (KPL-4 cells stably transfected with GloSensor plasmid) were harvested as described above. After one wash with PBS the concentration was adjusted to 0.3 x 106 cells/ml in the assay medium (RPMI1640, 2% FCS, 1% Glutamax) and mixed with 2% v/v GloSensor cAMP Reagent (Promega). 100 µl (= 30 000 cells) of this target cell suspension was transferred into each well of a 96-flat bottom plate with white walls.

Peripheral blood clear cells ) were prepared by Histopaque density centrifugation of enriched lymphocyte preparations (buffy coats) ed from healthy human , as described above. The tumor cell lysis assay was performed essentially as described above.

The results depicted in Figure 32C and Figure 33 rate that the Her3 TCB molecule induces potent and tration-dependent apoptosis and lysis of KPL-4 tumor cells.

The same is true for the Her2 TCB that is depicted Figure 32A and B and shows significant, concentration-dependent lysis of tumor cells over time. Thereby, the EC50 of killing seems to depend on the expression level of Her2 on the respective target cell. The higher the expression level, the better the tumor cell killing by the Her2 TCB.

Example 4 Preparation of “(Fab)2-CrossFab” T-cell bispecific antibodies with and without charge modifications (anti-MCSP / anti-CD3) A schematic illustration of the molecules prepared in this example is shown in Figure 34. The anti-MCSP/anti-CD3 “(Fab)2-CrossFab” le with charge modifications in the MCSP s (referred to as “(Fab)2-XFab-LC007cv” in this example) comprises the amino acid sequences of SEQ ID NOs 58, 59 and 60. The anti-MCSP/anti-CD3 “(Fab)2-CrossFab” molecule without charge modifications (referred to as “(Fab)2-XFab” in this example) comprises the corresponding amino acid sequences without the charge modifications.

The molecules were prepared, purified and analyzed essentially as described in Example 1 above, with the ing adaptations.

For the production of these molecules, the HEK293-EBNA cells were transfected with the corresponding expression vectors in a 1:2:1 ratio or heavy chain” : r light chain anti- MSCP Fab” : “vector light chain anti-CD3 Fab”). tration of the constructs in the culture medium was determined by ProteinA-HPLC, based on binding of parts of the CH1 domain to ProteinA at pH8.0 and step n from pH2.5 as described in Example 1.

The secreted proteins were purified from cell culture supernatants by affinity chromatography using affinity chromatography binding to CH1, followed by a size exclusion chromatographic step.

For affinity chromatography, supernatant was loaded on a HiTrap KappaSelect column (CV=5 mL, GE Healthcare) equilibrated with 5 ml 50 mM Tris, 100 mM glycine, 150 mM NaCl pH 8.0.

Unbound protein was removed by washing with at least 10 column volumes 50 mM Tris, 100 mM glycine, 150 mM NaCl pH 8.0. The target protein was eluted in 10 column volumes gradient to 50 mM Tris, 100 mM glycine, 150 mM NaCl pH 2.0. Protein solution was neutralized by adding 1/40 of 2 M Tris pH 8.0. Target protein is concentrated and filtered prior loading on a HiLoad Superdex 200 column (GE Healthcare) equilibrated with 20 mM histidine, 140 mM sodium de, 0.01% Tween-20, pH 6.0.

Both molecules were ed and purified following the same method ed to the molecule without charge cations (“(Fab)2-XFab”) the titer of the molecule with charges was 10 fold lower. Nevertheless the final recovery was imately two times higher for the molecule with the charge modifications in the two anti-MCSP Fabs (“(Fab)2-XFab-LC007cv”) (Table 18). The (Fab)2-XFab-LC007cv le could be purified to a final monomer content of 95.8% shown by size exclusion chromatography and a final purity proven by CE-SDS analyses of 94.33%.

TABLE 18. Summary of production and purification of anti-MCSP / anti-CD3 TCB molecules with and without charge modifications.

Analytical SEC Titer Recovery Molecule Yield [mg/l] (HMW/Monomer/LMW) [mg/l] [%] (Fab)2-XFab 25 6.24 7.8 0/100/0 (Fab)2-XFab-LC007cv 2.32 10.5 0.24 3.2/95.8/1 TABLE 19. CE-SDS analyses (non-reduced) of the anti-MCSP / anti-CD3 TCB molecule with charge modifications.

Molecule Peak # Size [kDa] Purity [%] 1 162.67 94.33 (Fab)2-XFab-LC007cv 2 170.59 5.67 Cell binding of “(Fab)2-CrossFab” T-cell bispecific antibodies with and without charge cations (anti-MCSP / anti-CD3) Jurkat-NFAT suspension cells were ted, washed with FACS buffer (PBS + 0.1% BSA) once and viability was determined by ViCell.

Adherent MV-3 tumor cells were harvested with Cell Dissociation Buffer (Gibco Invitrogen) and washed with FACS buffer once, before viability was determined by ViCell. 0.2 million cells were plated per well of a round-bottom 96-well plate and the plates were centrifuged for 4 min at 400 x g. Then 25 µl per well of the primary antibody dilutions in FACS buffer was added to the cells. The cells were incubated for 30 min in the fridge. Afterwards the cells were washed twice with 150 µl FACS buffer per well. 25 µl of the d secondary antibody (FITC conjugated AffiniPure F(ab')₂ Fragment, Goat Anti-Human IgG, F(ab')₂ fragment specific, Jackson ImmunoResearch) were added per well and the plates were stained for further 30 min at 4°C in the dark.

The plates were washed twice with 150 µl FACS buffer per well and resuspended in 150 µl FACS buffer. The analysis was performed using a BD FACS CantoII, equipped with FACS Diva Software. Median fluorescence values (MFI) were d against the concentration of the MCSP TCB molecules.

As shown in Figure 36, the (Fab)2-XFAb-LC007cv molecule shows concentration-dependent binding to human MCSP on MV-3 and to human CD3 on Jurkat cells. The (Fab)2-XFab molecule without charge modifications shows comparable binding to human MCSP as - XFAb-LC007cv (EC50 binding of 2.3 nM for the (Fab)2-XFAb-LC007cv versus EC 50 1.5 nM for the (Fab)2-XFab).

Tumor cell lysis ed by “(Fab)2-CrossFab” T-cell bispecific antibodies with and without charge modifications (anti-MCSP / anti-CD3) Tumor cell lysis of xpressing MV-3 tumor target cells induced by the MCSP TCB molecules was using human PBMCs as effectors, at an E:T of 10:1. Tumor cell lysis was determined by measurement of released LDH into the supernatants after 24 h and 48 h upon incubation with the TCBs. y, target cells were harvested with Trypsin/EDTA, washed, and plated at density of 25 000 cells/well using flat-bottom 96-well plates. Cells were left to adhere overnight in a humidified incubator. On the day of the assay, the assay plates were centrifuged at 350 x g for 5 min and the medium was aspirated. 100 µl per well of assay medium were added.

Peripheral blood clear cells (PBMCs) were isolated from fresh blood. y, blood was diluted 2:1 with PBS. About 30 ml of the blood/PBS mixture was layered on 15 ml of Histopaque (Sigma) and centrifuged for 30 min at 450 x g without brake. The lymphocytes were collected with a 10 ml pipette into 50 ml tubes containing PBS. The tubes were filled up to 50 ml with PBS and centrifuged 10 min at 350 x g. The atant was discarded, the pellet resuspended in 50 ml PBS and fuged for 10 min at 300 x g. The washing step was repeated once. The cells were re-suspended in RPMI containing 10 % FCS and 1% GlutaMax (Life Technologies) and stored at 37°C, 5% CO2 in the incubator until assay start (not longer than 24h).

For the killing assay, the TCB molecules were added at ted trations (range of 0.04 pM – 10 nM in triplicates). PBMCs were added to target cells at the final E:T ratio of 10:1.

Target cell killing was assessed after 24 h and 48 h of incubation by quantification of LDH (lactate dehydrogenase) released into cell supernatants by apoptotic/necrotic cells (LDH detection kit, Roche Applied Science, #11 644 793 001). Maximal lysis of the target cells (= 100%) was achieved by incubation of target cells with 1% Triton X-100. Minimal lysis (= 0%) refers to target cells co-incubated with effector cells t bispecific antibody. The EC50 values were calculated using GraphPadPrism5.

As depicted in Figure 37, both molecules show concentration-dependent lysis of hMCSP- expressing target cells. The potency of the -XFAb-LC007cv molecule (EC50 2.8 pM after 24h, and 8.6 pM after 48h) is comparable to the potency of the (Fab)2-XFab molecule without charge modifications (EC50 5.9 pM after 24 h, and 4.8 pM after 48 h).

* * * Although the foregoing invention has been described in some detail by way of illustration and example for purposes of y of understanding, the descriptions and examples should not be construed as limiting the scope of the invention. The disclosures of all patent and scientific ture cited herein are expressly orated in their entirety by reference.

In this specification where reference has been made to patent specifications, other al documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such al documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common l knowledge in the art.

Certain statements that appear herein are broader than what appears in the statements of the invention. These statements are provided in the sts of providing the reader with a better understanding of the invention and its practice. The reader is directed to the accompanying claim set which defines the scope of the invention.

Claims (49)

Claims 1.

1. A T cell activating bispecific antigen binding molecule comprising (a) a first Fab molecule which specifically binds to a first antigen; (b) a second Fab molecule which specifically binds to a second antigen, and wherein the variable 5 domains VL and VH of the Fab light chain and the Fab heavy chain are replaced by each other; (c) a third Fab molecule which ically binds to the first antigen; and (d) an Fc domain composed of a first and second subunit capable of stable association; wherein the first antigen is a target cell antigen, and the second antigen is an activating T cell antigen, 10 wherein the third Fab molecule under c) is identical to the first Fab molecule under a); wherein in the constant domain CL of the first Fab molecule under a) and the third Fab molecule under c) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by arginine (R) or lysine (K) (numbering according to Kabat), and wherein in the constant domain CH1 of the first Fab molecule under a) 15 and the third Fab molecule under c) the amino acid at position 147 is substituted by glutamic acid (E) ring according to Kabat EU index) and the amino acid at position 213 is substituted by ic acid (E) (numbering according to Kabat EU index); and wherein the Fc domain is an IgG Fc domain, and wherein in the CH3 domain of the first subunit of the Fc domain an amino acid residue is 20 replaced with an amino acid residue having a larger side chain , thereby generating a protuberance within the CH3 domain of the first subunit which is positionable in a cavity within the CH3 domain of the second subunit, and in the CH3 domain of the second t of the Fc domain an amino acid residue is replaced with an amino acid e having a smaller side chain , thereby generating a cavity within the CH3 domain of the second subunit within which 25 the erance within the CH3 domain of the first subunit is positionable; and wherein i) the first Fab le under a) is fused at the C-terminus of the Fab heavy chain to the N- terminus of the Fab heavy chain of the second Fab molecule under b), and the second Fab molecule under b) and the third Fab molecule under c) are each fused at the inus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d); or 5 ii) the second Fab molecule under b) is fused at the C-terminus of the Fab heavy chain to the N-terminus of the Fab heavy chain of the first Fab molecule under a), and the first Fab molecule under a) and the third Fab molecule under c) are each fused at the C-terminus of the Fab heavy chain to the N-terminus of one of the subunits of the Fc domain under d).

2. The T cell activating bispecific antigen binding molecule according to claim 1, wherein the 10 activating T cell antigen is CD3.

3. The T cell activating bispecific antigen binding le according to claim 1 or 2, wherein the activating T cell antigen is CD3 epsilon.

4. The T cell activating bispecific antigen binding molecule according to according to any one of claims 2 to 3, wherein the Fab molecule which ically binds to CD3 comprises the heavy 15 chain complementarity determining region (CDR) 1 of SEQ ID NO:4, the heavy chain CDR 2 of SEQ ID NO: 5, the heavy chain CDR 3 of SEQ ID NO: 6, the light chain CDR 1 of SEQ ID NO: 8, the light chain CDR 2 of SEQ ID NO: 9, and the light chain CDR 3 of SEQ ID NO:10.

5. The T cell activating bispecific antigen g molecule according to any one of claims 2 to 4, wherein the Fab molecule which specifically binds to CD3 comprises a heavy chain variable 20 region comprising an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising an amino acid ce that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 7.

6. The T cell activating bispecific antigen binding molecule according to any one of claims 1 to 5, 25 wherein the target cell antigen is CD20 and the Fab molecule which ically binds to the target cell antigen comprises the heavy chain complementarity determining region (CDR) 1 of SEQ ID NO: 46, the heavy chain CDR 2 of SEQ ID NO: 47, the heavy chain CDR 3 of SEQ ID NO: 48, the light chain CDR 1 of SEQ ID NO: 49, the light chain CDR 2 of SEQ ID NO: 50 and the light chain CDR 3 of SEQ ID NO: 51.

7. The T cell ting bispecific antigen binding molecule according to any one of claims 1 to 4, wherein the target cell antigen is CD20 and the Fab molecule which specifically binds to the target cell antigen comprises a heavy chain variable region sing an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of 5 SEQ ID NO: 30 and a light chain variable region comprising an amino acid sequence that is at least about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequence of SEQ ID NO: 31.

8. The T cell activating bispecific antigen binding molecule of any one of claims 1 to 7, wherein the first Fab molecule under a) and the third Fab molecule under c) each comprise a heavy chain 10 variable region comprising the amino acid sequence of SEQ ID NO: 30 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 31.

9. The T cell ting bispecific antigen binding molecule of any one of claims 1 to 8, wherein the second Fab molecule under b) comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising the amino acid 15 sequence of SEQ ID NO: 7.

10. The T cell activating bispecific antigen binding le according to any one of claims 1 to 9, wherein the Fc domain is an IgG1 or IgG4 Fc domain.

11. The T cell ting bispecific antigen binding molecule according to any one of claims 1 to 10, wherein the Fc domain is a human Fc domain. 20

12. The T cell activating bispecific antigen binding molecule of any one of claims 1 to 11, wherein said amino acid residue having a larger side chain volume is selected from the group consisting of arginine (R), alanine (F), tyrosine (Y), and tryptophan (W), and said amino acid residue having a smaller side chain volume is selected from the group consisting of alanine (A), serine (S), ine (T), and valine (V). 25

13. The T cell activating ific antigen binding molecule of any one of claims 1 to 12, wherein in the CH3 domain of the first subunit of the Fc domain the threonine residue at position 366 is replaced with a tryptophan residue (T366W), and in the CH3 domain of the second subunit of the Fc domain the tyrosine residue at position 407 is replaced with a valine residue (Y407V), and ally in the second subunit of the Fc domain additionally the threonine 30 residue at on 366 is replaced with a serine residue (T366S) and the e residue at on 368 is replaced with an alanine residue (L368A) (numberings according to Kabat EU

14. The T cell activating bispecific antigen binding molecule of any one of claims 1 to 13, wherein in the first subunit of the Fc domain additionally the serine residue at on 354 is 5 ed with a cysteine residue (S354C) or the glutamic acid residue at position 356 is replaced with a cysteine residue (E356C), and in the second subunit of the Fc domain additionally the tyrosine residue at position 349 is replaced by a cysteine residue (Y349C) (numberings according to Kabat EU index).

15. The T cell activating ific antigen binding molecule of any one of claims 1 to 14, 10 wherein the first subunit of the Fc domain comprises amino acid substitutions S354C and T366W, and the second subunit of the Fc domain comprises amino acid substitutions Y349C, T366S, L368A and Y407V (numbering according to Kabat EU index).

16. The T cell ting bispecific antigen binding molecule according to any one of claims 1 to 15, wherein the Fc domain exhibits reduced binding affinity to an Fc receptor and/or reduced 15 effector function, as compared to a native lgG1 Fc domain.

17. The T cell ting bispecific antigen binding molecule according to any one of claims 1 to 16, wherein said one or more amino acid substitution(s) is at one or more position(s) selected from the group of L234, L235, and P329 (Kabat EU index numbering).

18. The T cell activating bispecific antigen binding molecule ing to any one of claims 1 to 20 17, wherein each subunit of the Fc domain comprises three amino acid substitutions that reduce binding to an activating Fc receptor and/or effector on wherein said amino acid substitutions are L234A, nd P329G (Kabat EU index numbering).

19. The T cell activating bispecific antigen binding molecule according to any one of claims 1 to 18, wherein the molecule comprises at least one heavy chain that is about 95%, 96%, 97%, 98%, 25 99% or 100% cal to the amino acid ces of SEQ ID NO: 18, at least one heavy chain that is about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequences of SEQ ID NO: 19, at least one light chain that is about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequences of SEQ ID NO: 20, and at least one light chain that is about 95%, 96%, 97%, 98%, 99% or 100% identical to the amino acid sequences of SEQ ID NO: 21.

20. The T cell activating bispecific antigen binding molecule of any one of claims 1 to 19, wherein the Fc receptor is an Fcγ receptor.

21. The T cell activating bispecific antigen binding molecule of any one of claims 1 to 20, n the effector function is dy-dependent ediated cytotoxicity (ADCC). 5

22. One or more isolated polynucleotide(s) ng the T cell activating bispecific antigen binding molecule according to any one of claims 1 to 21.

23. One or more vector(s), comprising the polynucleotide(s) according to claim 22.

24. The one or more vector(s) according to claim 23, wherein the one or more vector(s) is an expression vector. 10

25. A host cell in culture comprising the polynucleotide(s) according to claim 22 or the vector(s) according to claim 23 or 24.

26. A method of producing a T cell activating bispecific antigen binding molecule ing to claim 1 and e of specific binding to CD3 and a target cell antigen, comprising the steps of a) culturing the host cell according to claim 25 under ions suitable for the expression of the 15 T cell activating bispecific antigen binding molecule and b) recovering the T cell activating bispecific antigen binding molecule.

27. The T cell activating bispecific antigen g molecule according to any one of claims 1 to 21 for use as a medicament.

28. The T cell activating bispecific antigen binding molecule ing to claim 27, wherein the 20 medicament is for use in the treatment of cancer.

29. The T cell activating ific antigen binding molecule according to any one of claims 1 to 21, for use in the treatment of a disease in an individual in need thereof wherein the molecule is to be administered with a further therapeutically ive amount of at least one additional therapeutic agent. 25

30. The T cell activating bispecific antigen binding molecule according to claim 29, wherein the disease is cancer.

31. A pharmaceutical composition comprising the T cell activating bispecific antigen binding molecule according to any one of claims 1 to 21 and a pharmaceutically acceptable carrier.

32. The pharmaceutical composition according to claim 31 for use as a medicament.

33. The pharmaceutical composition according to claim 31 for use in the treatment of a e 5 in an individual in need thereof wherein the pharmaceutical composition is to be stered with a further therapeutically effective amount of at least one additional therapeutic agent.

34. The pharmaceutical composition according to claim 32, wherein the composition is for use in the treatment of cancer.

35. The pharmaceutical composition according to claim 33, wherein the disease is cancer. 10

36. The T cell activating bispecific antigen binding molecule of any one of claims 1 to 21 for the treatment of a disease in an individual in need thereof.

37. Use of the T cell activating bispecific antigen binding molecule ing to any one of claims 1 to 21 for the manufacture of a medicament for the treatment of a disease in an dual in need thereof. 15

38. The use according to claim 37, wherein said disease is cancer.

39. The use according to claim 37 or 38, wherein the medicament further comprises at least one additional eutic agent.

40. The use ing to claim 37 or 38, wherein the medicament is in a form for, or is to be administered, prior to, aneously with, or following at least one additional therapeutic agent. 20

41. The T cell activating bispecific antigen binding molecule according to any one of claims 1 to 21, ntially as herein described with nce to any example thereof and with reference to the accompanying figures.

42. The one or more isolated polynucleotide(s) according to claim 22, substantially as herein described with reference to any example f and with reference to the anying figures. 25

43. The one or more vector(s) according to claim 23 or 24, substantially as herein described with reference to any example thereof and with reference to the anying figures.

44. The host cell according to claim 25, substantially as herein described with reference to any e thereof and with reference to the accompanying figures.

45. The method according to claim 26, substantially as herein bed with reference to any example thereof and with nce to the accompanying figures. 5

46. The T cell activating bispecific antigen binding molecule according to any one of claims 27- 30, substantially as herein described with reference to any example thereof and with nce to the accompanying figures.

47. The pharmaceutical composition according to any one of claims 31-35 , substantially as herein described with reference to any example thereof and with reference to the accompanying 10 figures.

48. The T cell activating bispecific antigen binding molecule for use according to claim 36, substantially as herein described with reference to any example thereof and with reference to the anying figures.

49. The use ing to any one of claims claim 37-40, substantially as herein described with 15 reference to any example thereof and with reference to the accompanying figures. WO 20309