Anti-CTLA4 antibodies and methods for making and using same

Abstract

To provide cross-reactive antibodies (or antigen binding fragments thereof) that bind to human CTLA4, activatable antibodies that bind to human CTLA4, nucleic acid molecules encoding the same, pharmaceutical compositions thereof, and methods of their therapeutic use (e.g., for treatment of cancer).SOLUTION: An activatable antibody comprises a first polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM). The activatable antibody binds to human CTLA4 via a VH and a VL when the CM is cleaved.SELECTED DRAWING: None

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to International Patent Application No. PCT / CN2018 / 075064, filed February 2, 2018, which is incorporated herein by reference in its entirety.

[0002] Submitting a sequence listing as an ASCII text file The following submission in an ASCII text file is incorporated by reference in its entirety: Sequence Listing in Computer Readable Form (CRF) (Filename: 695402000541SEQLIST.TXT, Recorded: February 1, 2019, Size: 102KB).

[0003] The present disclosure relates to cross-reactive antibodies that bind to human cytotoxic T-lymphocyte protein 4 (CTLA4), precision / context-dependent activatable antibodies that bind to human CTLA4, nucleic acids encoding same, pharmaceutical compositions thereof, and therapeutic uses thereof. [Background technology]

[0004] CTLA4 is a member of the immunoglobulin (Ig) superfamily of proteins that act to downregulate T cell activation and maintain immunogenic homeostasis. In vivo antibody-mediated blockade of CTLA4 has been shown to enhance anti-cancer immune responses in a syngeneic mouse prostate cancer model (Kwon et al. (1997) Proc Natl Acad Sci USA, 94(15):8099-103). Furthermore, blocking CTLA4 function has been shown to enhance anti-tumor T cell responses at various stages of tumor growth in tumor-bearing mice (Yang et al. (1997) Cancer Res 57(18):4036-41, Hurwitz et al. (1998) Proc Natl Acad Sci USA 95(17):10067-7). However, the development of antibody-based therapeutics suitable for human use remains challenging, as translation from preclinical animal models to human safety is often poor. Thus, there is a need for anti-CTLA4 antibodies that are cross-reactive across species, such as humans and experimental animals (e.g., mice, monkeys, rats, etc.), to enable animal model studies while providing suitable human therapeutic candidates. Additionally, there is a need for the development of safer anti-CTLA4 antibodies that are active only in certain contexts, such as the protease-rich tumor microenvironment.

[0005] All references cited herein, including patent applications, patent publications, non-patent literature, and UniProtKB / Swiss-Prot / GenBank accession numbers, are hereby incorporated by reference in their entirety as if each individual reference was specifically and individually indicated to be incorporated by reference. Summary of the Invention

[0006] To meet these and other needs, disclosed herein are antibodies (e.g., cross-reactive antibodies) that bind to human CTLA4, and antigen-binding fragments thereof. The disclosed anti-CTLA4 antibodies, or antigen-binding fragments thereof, have the following functional properties: (a) a K of 500 nM or less for human, cynomolgus monkey, mouse, rat, and / or dog CTLA4;D (b) have antagonist activity against human CTLA4; (c) do not bind to human PD-1, PD-L1, PD-L2, LAG3, TIM3, B7-H3, CD95, CD120a, OX40, CD40, BTLA, VISTA, ICOS, and / or B7-H4 at concentrations up to 100 nM; (d) are cross-reactive with monkey, mouse, rat, and / or dog CTLA4; (e) induce ADCC effects (e.g., against Tregs); (f) activate human PBMCs (e.g., stimulate secretion of IL-2 and / or IFNγ); (g) are capable of inhibiting tumor cell proliferation and establishing immune memory against tumor cells; (h) have therapeutic effects against cancer; and (i) block the binding of human CTLA4 to human CD80 and / or human CD86 (see Examples 1-5 below).

[0007] Disclosed herein are precision / context-dependent activatable antibodies that bind to human CTLA4 when active but not inactive, i.e., activatable antibodies that bind to CTLA4 (are active) only after cleavage of the cleavable moiety (CM) to remove the masking moiety (MM). In some embodiments, the discovered masking moieties (MM) described herein can efficiently mask antibody activity and / or reduce or completely inhibit antigen binding, while in some embodiments, they lack the chemically labile residues methionine and / or tryptophan. Moreover, the activatable antibodies identified and described herein are as efficient in treating multiple cancer types as their parent antibodies, and significantly reduce cytotoxicity in susceptible animals (NOD mice).

[0008] Thus, in one aspect, provided herein is an anti-CTLA4 antibody (e.g., a human antibody) that binds to human CTLA4 and is cross-reactive with CTLA4 polypeptides from at least one non-human animal selected from the group consisting of cynomolgus monkey, mouse, rat, and dog. In some embodiments, the antibody binds to cynomolgus monkey CTLA4 and mouse CTLA4. In some embodiments that may be combined with any of the preceding embodiments, the antibody binds to human CTLA4, cynomolgus monkey CTLA4, mouse CTLA4, rat CTLA4, and / or dog CTLA4 with a dissociation constant (K D In some embodiments, K Dis measured by surface plasmon resonance (SPR). In some embodiments, the binding of the antibody to CTLA4 induces antibody-dependent cellular cytotoxicity (ADCC) against CTLA4-expressing cells. In some embodiments, the binding of the antibody to CTLA4 induces ADCC against Treg cells. In some embodiments, the binding of the anti-CTLA4 antibody described herein induces antibody-dependent cellular cytotoxicity (ADCC) against CTLA4-expressing human cells or human Treg cells, and the ADCC activity of the anti-CTLA4 antibody is higher than the ADCC activity of ipilimumab in vitro, and both antibodies comprise wild-type human IgG1 Fc regions. In some embodiments, the binding of the anti-CTLA4 antibody described herein induces antibody-dependent cellular cytotoxicity (ADCC) against CTLA4-expressing human cells or human Treg cells, and the ADCC activity of the anti-CTLA4 antibody is more than two-fold higher than the ADCC activity of ipilimumab in vitro, and both antibodies comprise wild-type human IgG1 Fc regions. In some embodiments, the EC50 of anti-CTL4 antibody ADCC activity is 50% or less than the EC50 of ipilimumab ADCC activity in vitro. Assays for measuring ADCC activity are described in Examples 3 and 15. In some embodiments, anti-CTLA4 antibodies selectively deplete Treg cells in the tumor microenvironment (e.g., reduce the proportion of Treg cells in tumor-infiltrating lymphocytes) compared to PBMCs or spleen in mouse cancer models. See, e.g., Example 18.

[0009] In some embodiments that may be combined with any of the preceding embodiments, the antibody specifically binds to an epitope that includes amino acid residues in a ligand binding site of human CTLA4, such as the CD80 and / or CD86 binding site of human CTLA4. In some embodiments, the antibody specifically binds to an epitope that is similar to a ligand binding site of human CTLA4, such as the CD80 and / or CD86 binding site of human CTLA4. In some embodiments, the antibody specifically binds to an epitope that includes amino acid residues Y105 and L106 of human CTLA4, where the numbering of the amino acid residues is according to SEQ ID NO: 207. In some embodiments, the antibody does not bind to residue I108 of human CTLA4, where the numbering of the amino acid residues is according to SEQ ID NO: 207. In some embodiments, the anti-CTLA4 antibody blocks the binding of CD80 and / or CD86 to human CTLA4. In some embodiments, the anti-CTLA4 antibody has an IC50 that is higher than the IC50 of ipilimumab for blocking the binding of CD80 and / or CD86 to human CTLA4. In some embodiments, in assays where CD86 or CD80 are plate bound and CTLA4 is in solution or CTLA4 is displayed on the cell surface, the anti-CTLA4 antibodies have an IC50 that is 3.5-fold or greater, including 3.9-fold or greater, greater than that of ipilimumab for blocking binding of CD80 and / or CD86 to human CTLA4. See Example 13, Table 23, Figures 57A-57D, and Figure 58. Assays for testing blocking activity (ligand competition) and IC50 of antibodies are described in Examples 3 and 13.

[0010] In some embodiments that may be combined with any of the preceding embodiments, the antibody comprises a heavy chain variable region and a light chain variable region, wherein a) the heavy chain variable region comprises HVR-H1, HVR-H2, and HVR-H3, wherein HVR-H1 is a variable fragment represented by formula (I): X1TFSX2YX3IHWV (SEQ ID NO: 1), where X1 is F or Y, X2 is D or G, and X3 is A, G, or W; or S), and formula (III): FSLSTGGVAVX1WI (SEQ ID NO: 3) (wherein X1 is G or S), and HVR-H2 comprises an amino acid sequence according to a formula selected from the group consisting of formula (IV): IGX1IX2HSGSTYYSX3SLKSRV (SEQ ID NO: 4) (wherein X1 is D or E, X2 is S or Y, and X3 is P or Q), formula (V): IGX1ISPSX2GX3TX4YAQKFQGRV (SEQ ID NO: 5) (wherein X1 is I or W, X2 is G or S, X3 is G or S, and X4 is K or N), and formula (VI): VSX1ISGX2GX3X4TYYADSVKGRF (SEQ ID NO: 6) (wherein X1 is A, G, or S, X2 is S or Y, X3 is G or S, and X4 is S or T); HVR-H3 comprises an amino acid sequence according to a formula selected from the group consisting of formula (VII): ARX1X2X3X4FDX5 (SEQ ID NO: 7) (wherein X1 is G, R, or S, X2 is A, I, or Y, X3 is D, V, or Y, X4 is A, E, or Y, and X5 is I or Y), formula (VI II): ARX1GX2GYFDX3 (SEQ ID NO: 8) (wherein X1 is D or L, X2 is F or Y, and X3 is V or Y), formula (IX): ARX1X2X3X4AX5X6FDY (SEQ ID NO: 9) (wherein X1 is L or R, X2 is I or P, X3 is A or Y, X4 is S or T, X5 is T or Y, and X6 is A or Y), formula (X): ARDX1X2X3GSSGYYX4GFDX5 (SEQ ID NO: 10) (wherein X1 is I or V, X2 is A or H, and X3 is P or S,and b) the light chain variable region comprises an amino acid sequence according to a formula selected from the group consisting of HVR-L1, HVR-L2, and HVR-L3, wherein HVR-L1 is selected from the group consisting of formula (XI): RASQX1X2X3SX4LX5 (SEQ ID NO: 11) (wherein X1 is G or S, X2 is I or V, X3 is G or S, X4 is S or Y, and X5 is A or N), formula (XII): RASQX1VX2X3RX4LA (sequence No. 12) (wherein X1 is S or T, X2 is F, R, or S, X3 is G or S, and X4 is F or Y), and formula (XIII): RASX1SVDFX2GX3SFLX4 (SEQ ID NO: 13) (wherein X1 is E or Q, X2 is D, F, H, or Y, X3 is F, I, or K, and X4 is A, D, or H), and HVR-L2 comprises an amino acid sequence according to a formula selected from the group consisting of: X1ASX2X3X4X5GX6 ( and HVR-L3 comprises an amino acid sequence according to the formula (XV): YCX1X2X3X4X5X6PX7T (SEQ ID NO:15), where X1 is E, Q, or V, X2 is H or Q, X3 is A, G, H, R, or S, X4 is D, L, S, or Y, and X6 is I or V. X1 is H or Q, X2 is T or V, and X3 is E or V. In some embodiments, HVR-H1 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 18 to 29, HVR-H2 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 30 to 39, and HVR-H3 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 40 to 52,HVR-L1 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 53 to 65, HVR-L2 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 66 to 69, and HVR-L3 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 70 to 81. In some embodiments, the antibody is selected from the group consisting of: a) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 18, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 30, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 40, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 53, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 70; b) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 19, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 31, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 41, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 54, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 71; c) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 20, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 32, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 42, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 55, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 72. d) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 21, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 33, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 43, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 56, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 68, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 73; e) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 22, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 34, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 44. -H3, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 57, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 74; f) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 23, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 35, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 45, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 58, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 75;g) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 24, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 32, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 46, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 59, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 76; h) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 25, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 36, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 47, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 60, HVR-L2 comprising the amino acid sequence of sequence number 69, and HVR-L3 comprising the amino acid sequence of sequence number 77; i) HVR-H1 comprising the amino acid sequence of sequence number 26, HVR-H2 comprising the amino acid sequence of sequence number 37, HVR-H3 comprising the amino acid sequence of sequence number 48, HVR-L1 comprising the amino acid sequence of sequence number 61, HVR-L2 comprising the amino acid sequence of sequence number 66, and HVR-L3 comprising the amino acid sequence of sequence number 78; j) HVR-H1 comprising the amino acid sequence of sequence number 27, and HVR-H2 comprising the amino acid sequence of sequence number 32; HVR-H3 comprising the amino acid sequence of SEQ ID NO: 49, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 62, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 79; k) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 28, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 37, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 50, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 63, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 80; l) ) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 18, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 38, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 51, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 64, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 81, or m) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 29, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 39, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 52, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 65, and HVR-L2 comprising the amino acid sequence of SEQ ID NO: 68,and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 77. In some embodiments that may be combined with any of the preceding embodiments, the heavy chain variable region comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 82-94 and / or the light chain variable region comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 95-107. In some embodiments that may be combined with any of the preceding embodiments, the antibody comprises: a) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 82, or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 82, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 95, or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 95; b) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 83, or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 83; c) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 84 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 84, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 97 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 97; d) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 85 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 85, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 98 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 98;e) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 86 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 86, and an amino acid sequence of SEQ ID NO: 99 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 99; f) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 87 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 87, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 100 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 100; g) an amino acid sequence of SEQ ID NO: 88 or an amino acid sequence of SEQ ID NO: 88. a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 101 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 101; and b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 89; i) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 103 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 102, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 103 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 102; 91 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 91; j) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 104 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 104;k) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:92 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO:92, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:105 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO:105; l) an amino acid sequence of SEQ ID NO:93 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO:93. or m) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 94 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 94; and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 107 or a variant thereof having at least about 90% (e.g., at least about 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO: 107.

[0011] In some embodiments, the anti-CTLA4 antibodies described herein comprise a heavy chain variable region and a light chain variable region, and one, two, three, four, five, or six HVRs of the antibody comprise the HVR sequences shown in Table A. In some embodiments, the anti-CTLA4 antibodies comprise a heavy chain variable region comprising HVR-H1, HVR-H2, and HVR-H3, and wherein HVR-H1 comprises the amino acid sequence of SEQ ID NO:23, or wherein HVR-H2 comprises the amino acid sequence of SEQ ID NO:35, or wherein HVR-H3 comprises the amino acid sequence of SEQ ID NO:45. In some embodiments, the anti-CTLA4 antibodies comprise a light chain variable region comprising HVR-L1, HVR-L2, and HVR-L3, and wherein HVR-L1 comprises the amino acid sequence of SEQ ID NO:58, or wherein HVR-L2 comprises the amino acid sequence of SEQ ID NO:66, or wherein HVR-L3 comprises the amino acid sequence of SEQ ID NO:75. In some embodiments, the HVR-H2 of the antibody comprises the amino acid sequence of SEQ ID NO:35. In some embodiments, the anti-CTLA4 antibody comprises (a) a heavy chain variable region comprising HVR-H1 comprising the amino acid sequence of SEQ ID NO: 23, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 35, and HVR-H3 comprising the amino acid sequence of SEQ ID NO: 45, and / or a light chain variable region comprising HVR-L1 comprising the amino acid sequence of SEQ ID NO: 58, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 75. In some embodiments, one, two, three, four, five, or six HVRs of the antibody may comprise one, two, or three conservative amino acid substitutions in the HVRs. In some embodiments, the anti-CTLA4 antibody comprises (b) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:87 or an amino acid sequence having at least 90% (e.g., 91%, 92%, 93%, 95%, 96%, 97%, 98%, or 99%) sequence identity to the amino acid sequence of SEQ ID NO:87, and / or a light chain variable region comprising an amino acid sequence of SEQ ID NO:100 or an amino acid sequence having at least 90% (e.g., 91%, 92%, 93%, 95%, 96%, 97%, 98%, or 99%) sequence identity to the amino acid sequence of SEQ ID NO:100.

[0012] In some embodiments that may be combined with any of the preceding embodiments, the antibody is an antibody fragment. In some embodiments, the fragment is a Fab, Fab', Fab'-SH, F(ab')2, Fv, or scFv fragment. In some embodiments that may be combined with any of the preceding embodiments, the antibody comprises an IgG1, IgG2, IgG3, or IgG4 Fc region (e.g., a human IgG1, IgG2, IgG3, or IgG4 Fc region). In some embodiments, the antibody comprises a human IgG1 or a variant with enhanced ADCC activity. In some embodiments, the antibody comprises a human IgG1 with reduced fucosylation (or non-fucosylated). In some embodiments, the antibody is a human antibody.

[0013] Other aspects of the disclosure relate to antibodies that compete or cross-compete with any of the antibodies described herein for binding to human CTLA4. Also provided herein are antibodies that bind to the same and / or essentially the same epitope as any of the antibodies described herein.

[0014] Another aspect of the present disclosure is a method for producing a polypeptide comprising: a) a first polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein the MM is represented by the formula (XVIII): m CX n CZ o(SEQ ID NO: 134), wherein m is 2-10, n is 3-10, and o is 1-10, each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P, wherein MM inhibits binding of the activatable antibody to human CTLA4 when the CM is uncleaved, the CM comprises at least a first cleavage site, and the TBM comprises an antibody heavy chain variable region (VH), and a) a second polypeptide comprising an antibody light chain variable region (VL), wherein the activatable antibody binds human CTLA4 via the VH and VL when the CM is cleaved. In some embodiments, m is 3-10.

[0015] Another aspect of the disclosure is a polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein the MM is represented by the formula (XVIII): m CX n CZ o (SEQ ID NO: 134), wherein m is 2-10, n is 3-10, and o is 1-10, each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P, wherein MM inhibits binding of the activatable antibody to human CTLA4 when the CM is uncleaved, the CM comprises at least a first cleavage site, and the TBM comprises an antibody light chain variable region (VL), and a) a second polypeptide comprising an antibody heavy chain variable region (VH), wherein the activatable antibody binds human CTLA4 via the VH and VL when the CM is cleaved. In some embodiments, m is 3-10.

[0016] Another aspect of the present disclosure relates to an activatable antibody comprising a polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein the MM has the formula (XVIII): m CX n CZ o (SEQ ID NO:134), wherein m is 2-10, n is 3-10, and o is 1-10; each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y; each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P; MM inhibits binding of the activatable antibody to human CTLA4 if the CM is not cleaved; the CM comprises at least a first cleavage site; the TBM comprises, from the N-terminus to the C-terminus, an antibody light chain variable region (VL) and an antibody heavy chain variable region (VH); and the activatable antibody binds to human CTLA4 via the VH and VL if the CM is cleaved. In some embodiments, m is 3-10.

[0017] Another aspect of the present disclosure relates to an activatable antibody comprising a polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein the MM has the formula (XVIII): m CX n CZ owherein m is 2-10, n is 3-10, and o is 1-10; each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y; and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P; the MM inhibits binding of the activatable antibody to human CTLA4 if the CM is not cleaved; the CM comprises at least a first cleavage site; the TBM comprises, from the N-terminus to the C-terminus, an antibody heavy chain variable region (VH) and an antibody light chain variable region (VL); and the activatable antibody binds to human CTLA4 via the VH and VL if the CM is cleaved.

[0018] In some embodiments according to any one of the above activatable antibodies, m is 2, 3, 4, 5, or 6. In some embodiments, m is 6. In some embodiments, n is 6 to 8. In some embodiments, n is 6. In some embodiments, o is 1 to 2. In some embodiments, o is 2. In some embodiments that may be combined with any of the preceding embodiments, each X is not M, W, or C. In some embodiments that may be combined with any of the preceding embodiments, X in formula (XVIII) is not M, W, or C. m Each X is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P. In some embodiments that may be combined with any of the preceding embodiments, X of formula (XVIII) is n Each X is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P. In some embodiments, MM is m CPDHPYPCXX (SEQ ID NO: 181), X m CDAFYPYCXX (SEQ ID NO: 182), X m CDSHYPYCXX (SEQ ID NO: 183), and X mCVPYYYACXX (SEQ ID NO: 184), wherein m is 2-10, and each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y. In some embodiments, each X is not M, W, or C. In some embodiments, each X is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P. In some embodiments that may be combined with any of the preceding embodiments, the masking moiety (MM) comprises an amino acid sequence selected from SEQ ID NOs: 141-147. In some embodiments that may be combined with any of the preceding embodiments, the MM further comprises an additional amino acid sequence at its N-terminus. In some embodiments, the additional amino acid sequence comprises the amino acid sequence of SEQ ID NO: 148.

[0019] In some embodiments that may be combined with any of the preceding embodiments, the first cleavage site is a protease cleavage site for a protease selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin S, ADAM10, ADAM12, ADAMTS, caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE. In some embodiments that may be combined with any of the preceding embodiments, the CM further comprises a first linker (L1) C-terminal to the first cleavage site. In some embodiments, L1 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 156-163. In some embodiments that may be combined with any of the preceding embodiments, the CM further comprises a second cleavage site. In some embodiments, the second cleavage site is C-terminal to L1. In some embodiments, the second cleavage site is a protease cleavage site for a protease selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin S, ADAM10, ADAM12, ADAMTS, caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE. In some embodiments, the first and second cleavage sites are different.In some embodiments that may be combined with any of the preceding embodiments, the CM further comprises a second linker (L2) C-terminal to the second cleavage site. In some embodiments, L2 comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 156-163. In some embodiments that may be combined with any of the preceding embodiments, the CM further comprises a third linker (L3) N-terminal to the first cleavage site. In some embodiments that may be combined with any of the preceding embodiments, the CM comprises at least a first protease cleavage site and is selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, It is cleaved by one or more proteases selected from the group consisting of cathepsin D, cathepsin K, cathepsin S, ADAM10, ADAM12, ADAMTS, caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE.

[0020] In some embodiments that may be combined with any of the preceding embodiments, the activatable antibody comprises a masking portion (MM) and a cleavable portion (CM) comprising an amino acid sequence according to formula (XXIX): EVGSYX1X2X3X4X5X6CX7X8X9X10X11X12CX13X14SGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 164), where Xi is A, D, I, N, P, or Y; X2 is A, F, N, S, or V; and X3 is A, H, L, X1 is A, D, N, S, T, or Y, X2 is P, S, V, or Y, X3 is A, D, L, S, or Y, X4 is A, H, S, or Y, X5 is A, D, P, S, V, or Y, X6 is A, D, L, S, or Y, X7 is D, P, or V, X8 is A, D, H, P, S, or T, X9 is A, D, F, H, P, or Y, X10 is L, P, or Y, X11 is F, P, or Y, X12 is A, P, S, or Y, X13 is A, D, N, S, T, or Y, and X14 is A, S, or Y. In some embodiments that may be combined with any of the preceding embodiments, the activatable antibody comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 165-179.

[0021] In some embodiments that can be combined with any of the preceding embodiments, the VL comprises HVR-L1 comprising the amino acid sequence of SEQ ID NO:58, HVR-L2 comprising the amino acid sequence of SEQ ID NO:66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO:75. In some embodiments that can be combined with any of the preceding embodiments, the VL comprises the amino acid sequence of SEQ ID NO:100, or a variant thereof having at least about 90% (e.g., at least 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO:100. In some embodiments that can be combined with any of the preceding embodiments, the VH comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO:23, HVR-H2 comprising the amino acid sequence of SEQ ID NO:35, and HVR-H3 comprising the amino acid sequence of SEQ ID NO:45. In some embodiments that can be combined with any of the preceding embodiments, the VH comprises the amino acid sequence of SEQ ID NO:87, or a variant thereof having at least about 90% (e.g., at least 92%, 95%, 98%, 99% or more) sequence identity to the amino acid sequence of SEQ ID NO:87.

[0022] Other aspects of the present disclosure relate to pharmaceutical compositions comprising any of the antibodies and / or activatable antibodies described herein and a pharma- ceutically acceptable carrier.

[0023] Another aspect of the disclosure pertains to a polynucleotide encoding any of the antibodies and / or activatable antibodies described herein. In some embodiments, the polynucleotide comprises a sequence selected from SEQ ID NOs: 108-133.

[0024] Another aspect of the disclosure pertains to a vector comprising any of the polynucleotides described herein. In some embodiments, the vector is an expression vector and / or a display vector.

[0025] Another aspect of the present disclosure relates to a host cell comprising any of the polynucleotides and / or vectors described herein. In some embodiments, the host cell is a eukaryotic organism. In some embodiments, the host cell is a Chinese Hamster Ovary (CHO) cell.

[0026] Another aspect of the disclosure relates to a method of making an antibody or activatable antibody, comprising culturing any of the host cells described herein under conditions suitable for the production of the antibody or activatable antibody, hi some embodiments, the method further comprises recovering the antibody or activatable antibody produced by the cell.

[0027] Other aspects of the disclosure relate to methods of treating or slowing the progression of cancer in a subject in need thereof, the methods comprising administering to the subject an effective amount of any of the antibodies, activatable antibodies, and / or pharmaceutical compositions described herein. In some embodiments, the cancer is liver cancer, cancer of the digestive system (e.g., colon cancer, colorectal cancer), lung cancer, bone cancer, heart cancer, brain cancer, kidney cancer, bladder cancer, blood cancer (e.g., leukemia), skin cancer, breast cancer, thyroid cancer, pancreatic cancer, head and neck cancer, eye-related cancer, cancer of the male reproductive system (e.g., prostate cancer, testicular cancer), or cancer of the female reproductive system (e.g., uterine cancer, cervical cancer). Other aspects of the disclosure relate to methods of reducing the size of a solid tumor in a subject in need thereof, the solid tumor being between about 400 and 1000 mm. 3 In some embodiments, the solid tumor has a size of about 400-800 mm and the method includes administering to the subject an effective amount of any of the antibodies, activatable antibodies, and / or pharmaceutical compositions described herein. 3In some embodiments, the method further comprises administering to the subject an effective amount of at least one additional therapeutic agent. In some embodiments, the at least one additional therapeutic agent is selected from the group consisting of viral gene therapy, immune checkpoint inhibitors, targeted therapy, radiation therapy, vaccine therapy, and chemotherapy. In some embodiments, the at least one additional therapeutic agent is selected from the group consisting of pomalyst, Revlimid, lenalidomide, pomalidomide, thalidomide, DNA alkylating platinum-containing derivatives, cisplatin, 5-fluorouracil, cyclophosphamide, anti-CD137 antibody, anti-PD-1 antibody, anti-PD-L1 antibody, anti-CD20 antibody, anti-CD40 antibody, anti-DR5 antibody, anti-CD1d antibody, anti-TIM3 antibody, SLAMF7 antibody, anti-KIR receptor antibody, anti-OX40 antibody, anti-HER2 antibody, anti-ErbB-2 antibody, anti-EGFR antibody, cetuximab, rituximab, trastuzumab, pembrolizumab, radiation therapy, single radiation, fractionated radiation, focal radiation, whole organ radiation, IL-12, IFNα, GM-CSF, chimeric antigen receptor, adoptively transferred T cells, anti-cancer vaccines, and oncolytic viruses. In some embodiments, the method comprises administering to the subject an effective amount of an anti-CTLA4 antibody, activatable antibody, or pharmaceutical composition described herein before or after surgery to remove a tumor in the subject. In some embodiments, the anti-CD137 antibody comprises an antibody heavy chain variable region comprising HVR-H1 comprising the amino acid sequence FSLSTGGVGVGWI (SEQ ID NO: 223), HVR-H2 comprising the amino acid sequence LALIDWADDKYYSPSLKSRL (SEQ ID NO: 224), and HVR-H3 comprising the amino acid sequence ARGGSDTVIGDWFAY (SEQ ID NO: 225), and an antibody light chain variable region comprising HVR-L1 comprising the amino acid sequence RASQSIGSYLA (SEQ ID NO: 226), HVR-L2 comprising the amino acid sequence DASNLETGV (SEQ ID NO: 227), and HVR-L3 comprising the amino acid sequence YCQQGYYLWT (SEQ ID NO: 228).In some embodiments, the anti-CD137 antibody comprises an antibody heavy chain variable region comprising the amino acid sequence of SEQ ID NO:229 or a sequence having at least 90% (e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identity to the sequence of SEQ ID NO:229, and / or an antibody light chain variable region comprising the amino acid sequence of SEQ ID NO:230 or a sequence having at least 90% (e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identity to the sequence of SEQ ID NO:230. TIFF0007678841000001.tif37170

[0028] It should be understood that one, some, or all of the characteristics of the various embodiments described above and herein may be combined to form other embodiments of the present disclosure. These and other aspects of the present disclosure will be apparent to those skilled in the art. These and other embodiments of the present disclosure are further described by the following detailed description. [Brief description of the drawings]

[0029] [Figure 1] Figure 1 shows antibody binding to CTLA4 as determined by ELISA. A shows binding of the indicated antibodies to human CTLA4. B shows binding of the indicated antibodies to canine CTLA4. [Diagram 2] Shown is the species cross-reactivity of the indicated antibodies, isotype control, or vehicle (PBSA) against HEK293F cells transiently overexpressing empty vector (pIRES), or mouse or human CTLA4, as determined by flow cytometry. [Diagram 3] Binding of antibody TY21580 or isotype control to activated human, monkey, and mouse T cells as determined by flow cytometry. [Figure 4A]Antibody specificity for CTLA4 as determined by flow cytometry. Binding of the indicated antibodies or isotype control to HEK293F cells transiently overexpressing human PD-1, CTLA4, LAG3, TIM3, B7-H3, or empty vector (293F) is shown. [Figure 4B] Antibody specificity for CTLA4 as determined by flow cytometry. Binding of the indicated antibodies, isotype control, or vehicle (PBSA) to HEK293F cells transiently overexpressing human CD95, CD120a, OX40, CD40, CTLA4, or empty vector (pIRES) is shown. [Figure 4C] Antibody specificity for CTLA4 as determined by flow cytometry. Binding of the indicated antibodies, isotype control, or vehicle (PBSA) to HEK293F cells transiently overexpressing human TIM3, CTLA4, PD-L1, LAG3, BTLA, VISTA, PD-L2, ICOS, B7-H4, PD-1, B7-H3, or empty vector (pIRES) is shown. [Figure 5A-B] Figure 5A: Blocking ability of antibodies as determined by ELISA. Ability of antibodies TY21687, TY21689, TY21680, and TY21691 to block human CD80 binding to human CTLA4. Figure 5B: Blocking ability of antibodies as determined by ELISA. Ability of antibodies TAC2114, TY21585, TY21587, TY21588, TY21589, TY21580, and TY21591 to block human CD80 binding to human CTLA4. [Figure 5C-D] Figure 5C: Blocking ability of antibodies as determined by ELISA. Ability of antibodies TY21687, TY21689, TY21680, and TY21691 to block human CD86 binding to human CTLA4. Figure 5D: Blocking ability of antibodies as determined by ELISA. Ability of antibodies TAC2114, TY21585, TY21587, TY21588, TY21589, TY21580, and TY21591 to block human CD86 binding to human CTLA4. [Figure 6] Blocking ability of antibodies as determined by FACS is shown. A shows the ability of the indicated antibodies, isotype control, or vehicle (PBSA) to block human CD80 binding to HEK293F cells transiently overexpressing human CTLA4. B shows the ability of the indicated antibodies, isotype control, or vehicle (PBSA) to block human CD86 binding to HEK293F cells transiently overexpressing human CTLA4. [Figure 7] 1 shows the ability of the indicated antibodies to bind FcRn as determined by surface plasmon resonance (SPR). [Figure 8] Figure 1 shows activation of human peripheral blood mononuclear cells (PBMCs) by antibody TY21580 or an isotype control as measured by ELISA. A shows the effect on IL-2 secretion from CD3-stimulated human PBMCs treated with antibody TY21580 or an isotype control. B shows the effect on IFNγ secretion from CD3-stimulated human PBMCs treated with antibody TY21580 or an isotype control. [Figure 9] FIG. 1 shows the effect on IL-2 secretion from human PBMC treated with antibody TY21580 in the presence or absence of anti-CD3 antibody, as measured by ELISA. [Figure 10] Shown is the effect on IFNγ secretion from human dendritic cells (DCs) co-cultured with allogeneic CD4+ T cells treated with antibody TY21580, isotype control, or anti-PD-1 antibody, as measured by ELISA. [Figure 11]1 shows the antibody-dependent cell-mediated cytotoxicity (ADCC) activity of exemplary antibodies against HEK293F cells transiently overexpressing human CTLA4 as determined by lactate dehydrogenase (LDH) release assay. A shows the ADCC activity of antibody TY21580 or isotype control against HEK293F cells transiently overexpressing human CTLA4 and incubated with human natural killer (NK) cells. B shows the ADCC activity of antibody TY21580, TAC2114, or isotype control against HEK293F cells transiently overexpressing human CTLA4 and incubated with human NK cells. [Figure 12] 1 shows the ADCC activity of exemplary antibodies against human Tregs isolated from two donors as determined by calcein AM release assay. A shows the ADCC activity of antibodies TY21580, TAC2114, or isotype control against human Treg cells (from donor #96) incubated with human NK cells. B shows the ADCC activity of antibodies TY21580, TAC2114, or isotype control against human Treg cells (from donor #12) incubated with human NK cells. [Figure 13] Figure 1 shows the complement dependent cytotoxicity (CDC) activity of antibody TY21580 or isotype control against HEK293F cells transiently overexpressing human CTLA4 as determined by a calcein AM release assay. [Figure 14] CDC activity of antibody TY21580 or isotype control on activated human CD4+ T cells as determined by calcein AM release assay. [Figure 15] Figure 1 shows the in vivo antitumor effect of antibody TY21580 or isotype control in the MC38 syngeneic mouse colorectal tumor model. A shows tumor growth curves of female MC38-type tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means and error bars represent SEM. B shows individual tumor growth curves for each group tested. C shows a rechallenge study showing long-lasting immune memory against MC38 tumor cells. [Figure 16]Figure 1 shows the in vivo antitumor effect of antibody TY21580 or isotype control in the CT26 syngeneic mouse colorectal tumor model. Tumor growth curves of female CT26 tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means and error bars represent SEM. [Figure 17] Figure 1 shows the in vivo antitumor efficacy of antibodies TY21586, TY21580, or isotype control in the H22 syngeneic mouse liver tumor model. Tumor growth curves of female H22 tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means, error bars represent SEM. [Figure 18] Figure 1 shows the in vivo antitumor efficacy of antibodies TY21580, TY21687, TY21687, TY21691 and TY21580, or isotype control in a Lewis syngeneic mouse lung tumor model. Tumor growth curves of female Lewis tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means and error bars represent SEM. [Figure 19] Figure 1 shows the in vivo antitumor effect of antibody TY21580 or isotype control in the PAN02 syngeneic mouse pancreatic tumor model. Tumor growth curves of female PAN02-type tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means and error bars represent SEM. [Figure 20] Figure 1 shows the in vivo antitumor efficacy of monotherapy with antibody TY21580, anti-CD137 antibody, or isotype control, as well as TY21580 + anti-CD137 combination therapy in a 3LL syngeneic mouse lung tumor model. A shows tumor growth curves of female 3LL tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means, error bars represent SEM. B shows individual tumor growth curves for each group tested. [Figure 21] Figure 1 shows a rechallenge study demonstrating long-lasting immune memory against H22 mouse liver tumor cells. Mice that showed complete responses in the TY21580-treated group were rechallenged subcutaneously with H22 tumor cells in the contralateral flank on day 59. Naive mice were also inoculated with H22 tumor cells at the same time. [Figure 22]Shown is the time course of blood concentrations of the indicated antibodies administered intravenously at 10 mg / kg to female BALB / c mice, as determined by ELISA. [Figure 23] 1 shows the time course of blood concentrations of the indicated antibodies administered intravenously at 10 mg / kg to cynomolgus monkeys, as determined by ELISA. [Figure 24] 1 shows the time course of blood concentrations of the indicated antibodies administered intravenously to cynomolgus monkeys at a concentration of 10 mg / kg compared to the appearance of anti-drug antibodies (ADA) in these monkeys as determined by ELISA. [Diagram 25] Average spleen weights of male and female BALB / c mice after repeated intraperitoneal administration of either antibody TY21580 or vehicle control. A shows the average spleen weights of male BALB / c mice after repeated intraperitoneal administration of either antibody TY21580 or vehicle control on days 1, 4, 7, and 11. B shows the average spleen weights of female BALB / c mice after repeated intraperitoneal administration of either antibody TY21580 or vehicle control on days 1, 4, 7, and 11. [Figure 26] Histopathology of BALB / c mice following repeated intraperitoneal administration of either antibody TY21580 or vehicle control on days 1, 4, 7, and 11 is shown. [Figure 27] FIG. 1 shows the stability of exemplary antibodies after storage at high concentrations. A shows the size exclusion chromatography (SEC) profile of antibody TY21586 after storage at over 100 mg / mL. B shows the SEC profile of antibody TY21580 after storage at over 100 mg / mL. [Figure 28] 1 shows the SEC profile of an exemplary antibody under accelerated stress conditions. [Figure 29] FIG. 1 shows a schematic of the selection process for auto-blocking peptides using Fab fragments of anti-CTLA4 antibodies displayed on the yeast surface. [Diagram 30] FIG. 1 shows a schematic of the selection process for self-blocking peptides using scFv fragments of anti-CTLA4 antibodies displayed on the yeast surface. [Diagram 31]Figure 1 shows functional display of Fab and scFv targeting CTLA4 on yeast as determined by flow cytometry. A shows functional display of Fab targeting CTLA4 on the surface of yeast. B shows functional display of scFv targeting CTLA4 on the surface of yeast. [Diagram 32] 1 shows an exemplary selection process for activatable antibodies targeting human CTLA4. A yeast library displaying fusion proteins was subjected to several rounds of FACS-based screening. [Diagram 33] 1 shows the CTLA4 binding affinity of exemplary CTLA4 activatable antibody clones as determined by flow cytometry. A shows the binding affinity of CTLA4 activatable antibody clones in scFv format, including CTLA4 activatable antibody clone B13287 with intact masking peptide or with TEV protease cleaved masking peptide, compared to scFv fragment of target antibody without masking peptide. B shows the CTLA4 binding affinity of CTLA4 activatable antibody clones in Fab format, including CTLA4 activatable antibody clone B13189 with intact masking peptide or with TEV protease cleaved masking peptide, compared to Fab fragment of target antibody without masking peptide. [Diagram 34] Figure 1 shows the masking efficiency of exemplary CTLA4 activatable antibodies TY22401, TY22403, TY22402, and TY22404 compared to parent antibody TY21580. A shows the association and dissociation curves of the indicated activatable antibodies compared to parent antibody TY21580 as determined by the ForteBio system. B shows a graph of the relative ratio of activatable antibody bound compared to parent antibody TY21580. [Diagram 35]1 shows the masking efficiency of exemplary CTLA4 activatable antibodies against recombinant human CTLA4-Fc as determined by ELISA. A shows the first batch of ELISA data showing the binding of CTLA4 activatable antibodies TY22401, TY22402, TY22403, TY22404 to recombinant human CTLA4-Fc compared to parent antibody TY21580. B shows the binding of CTLA4 activatable antibodies TY22563, TY22564, TY22565, TY22566 to recombinant human CTLA4-Fc compared to parent antibody TY21580. [Diagram 36] Figure 1 shows the activity of CTLA4 activatable antibody TY22404 upon removal of the masking peptide. A shows SDS-PAGE results for activatable antibody TY22404 untreated, treated with protease uPA, or treated with 5 or 10 units of protease MMP-9. B shows the binding of activatable antibody TY22404 untreated, treated with protease uPA, or treated with protease MMP-9 compared to parent antibody TY21580 as determined by ELISA. [Figure 37] 1 shows size exclusion chromatography (SEC) profiles of an exemplary activatable antibody under accelerated stress conditions. A shows the SEC profile of activatable antibody TY22402 after 6 cycles of freeze-thawing compared to control conditions. B shows the SEC profile of activatable antibody TY22402 after 7 days at 50° C. compared to control conditions. C shows the percentage of SEC main peak area of ​​an exemplary activatable antibody after 7 days at 50° C., after storage at 40° C. for up to 28 days, or after 6 cycles of freeze-thawing compared to control conditions. [Figure 38] Shown is the percentage of the SEC main peak area for activatable antibodies TY22401 and TY22402 after storage at about 8 mg / mL or above 150 mg / mL. [Figure 39]1 shows the masking efficiency of untreated activatable antibodies TY21580, TY22401, TY22402, and TY22566 incubated at pH 3.7 for 30 minutes or incubated at pH 3.7 for 1 hour as determined by the ForteBio system. [Diagram 40] Figure 1 shows human peripheral blood mononuclear cell (PBMC) activation by isotype control antibody, parent antibody TY21580, or exemplary CTLA4 activatable antibodies TY22401, TY22402, or TY22404 as measured by ELISA. A shows the effect on IL-2 secretion from CD3-primed human PBMC stimulated with isotype control antibody, parent antibody TY21580, and exemplary CTLA4 activatable antibodies TY22401, TY22402, or TY22404. B shows the effect on IFNγ secretion from CD3-primed human PBMC stimulated with isotype control antibody, parent antibody TY21580, and exemplary CTLA4 activatable antibodies TY22401, TY22402, or TY22404. [Diagram 41] 1 shows antibody-dependent cell-mediated cytotoxicity (ADCC) activity of an isotype control antibody, parent antibody TY21580, or exemplary activatable antibodies TY22401, TY21580, or TY22404 against HEK293F cells transiently overexpressing human CTLA4 as determined by an ADCC reporter gene assay. [Diagram 42] Figure 1 shows the in vivo antitumor efficacy of parental antibody TY21580, isotype control antibody, or exemplary CTLA4 activatable antibodies TY22401, TY22402, or TY22566 in the MC38 syngeneic mouse colorectal tumor model. A shows tumor growth curves of female MC38 tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means and error bars represent SEM. B shows individual tumor growth curves of groups treated with TY21580, TY22401, TY22402, and TY22566. [Diagram 43]Figure 1 shows the in vivo antitumor effects of an isotype control antibody, parent antibody TY21580, or one of the three activatable antibodies in a CT26 syngeneic mouse colorectal tumor model. Tumor growth curves of female CT26 tumor-bearing C57BL / 6 mice in different treatment groups are shown. Data points represent group means, and error bars represent SEM. [Diagram 44] Figure 1 shows the in vivo antitumor effects of isotype control antibody, parent antibody TY21580, or one of the three activatable antibodies in the H22 syngeneic mouse liver tumor model. Tumor growth curves of female H22 tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means, error bars represent SEM. [Diagram 45] Figure 1 shows the in vivo antitumor efficacy of parental antibody TY21580, isotype control antibody, and exemplary activatable antibodies TY22401, TY22402, or TY22566 in a 3LL syngeneic mouse lung tumor model. A shows tumor growth curves of female 3LL tumor-bearing C57BL / 6 mice in different treatment groups. Data points represent group means and error bars represent SEM. B shows individual tumor growth curves of groups treated with TY21580, TY22401, TY22402, and TY22566. [Figure 46] 1 shows the time course of blood concentrations as determined by ELISA of test article (TA) administered intravenously at 10 mg / kg to female BALB / c mice. A shows the time course of blood concentrations of activatable antibody TY22401 administered intravenously at 10 mg / kg to female BALB / c mice compared to the parent antibody TY21580. B shows the time course of blood concentrations of activatable antibody TY22402 administered intravenously at 10 mg / kg to female BALB / c mice compared to the parent antibody TY21580. C shows the time course of blood concentrations of activatable antibody TY22404 administered intravenously at 10 mg / kg to female BALB / c mice compared to the parent antibody TY21580. [Figure 47]

[0023] Figure 1 shows repeat dose toxicity of an isotype control antibody, parent antibody TY21580, and exemplary activatable antibodies TY22566, TY22401, and TY22402 using the NOD mouse model. Percent survival over 20 days is shown for each treatment group. [Figure 48A] Average spleen weights of BALB / c mice after repeated intraperitoneal administration of the indicated activatable antibodies. Average spleen weights of BALB / c mice after repeated intraperitoneal administration of activatable antibody TY22402, parental antibody TY21580, or isotype control on days 1, 4, 7, and 11. [Figure 48B] Average spleen weights of BALB / c mice after repeated intraperitoneal administration of the indicated activatable antibodies. Average spleen weights of BALB / c mice after repeated intraperitoneal administration of activatable antibody TY22566, parental antibody TY21580, or isotype control on days 1, 4, 7, and 11. [Figure 48C] Average spleen weights of BALB / c mice after repeated intraperitoneal administration of the indicated activatable antibodies. Average spleen weights of BALB / c mice after repeated intraperitoneal administration of activatable antibody TY22401, parental antibody TY21580, or isotype control on days 1, 4, 7, and 11. [Figure 49] Size exclusion chromatography (SEC) profiles of the indicated activatable antibodies after 7 days at 50° C. compared to control conditions are shown. [Figure 50] Size exclusion chromatography (SEC) profiles of the indicated activatable antibodies after storage at 40° C. for 7, 14, 21, or 28 days compared to control conditions are shown. [Figure 51] Size exclusion chromatography (SEC) profiles of the indicated activatable antibodies after six cycles of freeze-thaw compared to control conditions are shown. [Figure 52] Shown is the percentage of SEC main peak ratio for the indicated activatable antibodies after storage at >115 mg / mL. [Figure 53] A summary of the stability data is shown. [Figure 54]1 shows a multiple sequence alignment of a portion of human CTLA4 and mouse CTLA4 with contact residues mapped between human CTLA4 and one of CD80, CD86, or ipilimumab (based on two crystal structures). Contact amino acids are shaded in grey, major contact amino acids are outlined in bold, dimer interface amino acids are dotted, and amino acids that differ between mouse CTLA4 and human CTLA4 are underlined and bold. The sequences shown are represented from top to bottom by SEQ ID NOs: 203-208. [Figure 55] A shows the interaction between human CTLA4 and its ligand CD80. B shows the interaction between human CTLA4 and its ligand CD86. C shows the structural alignment between human CTLA4 and mouse CTLA4. Human CTLA4 is colored black and mouse CTLA4 is colored white. [Fig. 56A-B] Figure 56A: Results from an epitope mapping experiment showing the binding ability of TY21580 (A), ipilimumab (B), human CD80 (C), human CD86 (D), and mouse CD86 (E) to human CTLA4, mouse CTLA4, and CTLA4 mutants by flow cytometry. Figure 56B: Results from an epitope mapping experiment showing the binding ability of TY21580 (A), ipilimumab (B), human CD80 (C), human CD86 (D), and mouse CD86 (E) to human CTLA4, mouse CTLA4, and CTLA4 mutants by flow cytometry. [Fig. 56C-E]Figure 56C: Results from an epitope mapping experiment showing the binding ability of TY21580 (A), ipilimumab (B), human CD80 (C), human CD86 (D), and mouse CD86 (E) to human CTLA4, mouse CTLA4, and CTLA4 mutants by flow cytometry. Figure 56D: Results from an epitope mapping experiment showing the binding ability of TY21580 (A), ipilimumab (B), human CD80 (C), human CD86 (D), and mouse CD86 (E) to human CTLA4, mouse CTLA4, and CTLA4 mutants by flow cytometry. Figure 56E: Shows results from an epitope mapping experiment demonstrating the binding ability of TY21580 (A), ipilimumab (B), human CD80 (C), human CD86 (D), and mouse CD86 (E) to human CTLA4, mouse CTLA4, and CTLA4 mutants by flow cytometry. [Figure 57] 1 shows the effect of TY21580 and ipilimumab on receptor-ligand binding blockade between human CTLA4 and CD80 or CD86. A and B show the binding curves of human CD80 (A) or CD86 (B) in the presence of serial dilutions of TY21580, ipilimumab, or isotype control antibody to plate-bound human recombinant CTLA4 protein as measured by ELISA. C-D show the binding curves of human recombinant CTLA4 protein to plate-bound human CD80 (C) or CD86 (D) in the presence of serial dilutions of TY21580, ipilimumab, or isotype control antibody as measured by ELISA. [Figure 58]Figure 1 shows CTLA4 blockade-mediated reporter signaling activation of the CD28 pathway by anti-CTLA4 antibodies. Jurkat / CTLA4 and aAPC / Raji cells were co-cultured in the presence of serially diluted anti-CTLA4 antibodies, with human IgG1 anti-HEL antibody as isotype control. After overnight incubation, luminescence signal was measured with Bio-Glo luciferase substrate and relative luciferase units (RLU) were normalized to blank control. Results are expressed as mean RLU-fold ± SEM. Experiments were performed in triplicate. Note: The data point at the highest concentration of TY21580 (500 μg / mL) was excluded from analysis while fitting the curves, since a clear hook effect was observed at this point. [Figure 59] Figure 1 shows signaling activation of ADCC reporter by anti-CTLA4 antibody. Jurkat / NFAT-Luc / CD16 cells and HEK293F / hCTLA4 cells were co-cultured in the presence of serial dilutions of anti-CTLA4 antibody, with human IgG1 anti-HEL antibody as isotype control. After 6 h incubation, luminescence signal was measured with ONE-Glo luciferase substrate. Relative luciferase units (RLU) were normalized to blank control and results are expressed as mean RLU ± SEM. Experiments were performed in triplicate. [Figure 60A] Figure 1 shows tumor growth curves of MC38 tumor-bearing mice treated with anti-CTLA4 antibody. Group mean tumor growth over time in MC38 tumor-bearing mice treated with isotype control antibody (1 mg / kg BIW), TY21580 (1 mg / kg or 0.2 mg / kg BIW), or ipilimumab (1 mg / kg or 0.2 mg / kg BIW). Data points represent the mean and error bars represent the standard error of the mean (SEM). [Figure 60B] 1 shows tumor growth curves for MC38 tumor-bearing mice treated with anti-CTLA4 antibody. Shown are tumor growth over time in individual MC38 tumor-bearing mice treated with isotype control antibody (group 1), TY21580 (groups 2 and 3), or ipilimumab (groups 4 and 5). [Figure 61]Figure 1 shows the effect of TY21580 and ipilimumab on intratumoral regulatory T (Treg) cell levels in subcutaneous MC38 tumors from mice treated with TY21580 or ipilimumab. A shows the percentage of T regulatory (Treg) cells (CD4+CD25+) among CD4+ T cells isolated from tumors. B shows the ratio of cytotoxic T lymphocytes (CD8+ T cells) to Treg cells (i.e., CD8+ / Treg ratio) among CD4+ T cell subpopulations isolated from tumors. Each data point represents data from one mouse. Statistical analysis was performed using Prism 7 (GraphPad Software). P values ​​were calculated using multiple T-test. ns: P>0.05, **: 0.001 <P<0.01、***:P<0.001。 [Figure 62] Figure 1 shows the effect of TY21580 and ipilimumab on intratumoral regulatory T (Treg) cell levels in subcutaneous CT26 tumors from mice treated with TY21580 or ipilimumab. A shows the percentage of T regulatory (Treg) cells (CD4+CD25+) among CD4+ T cells isolated from tumors. B shows the ratio of cytotoxic T lymphocytes (CD8+ T cells) to Treg cells (i.e., CD8+ / Treg ratio) among CD4+ T cell subpopulations isolated from tumors. Each data point represents data from one mouse. Statistical analysis was performed using Prism 7 (GraphPad Software). P values ​​were calculated using multiple T-test. ns: P>0.05, **: 0.001 <P<0.01、***:P<0.001。 [Figure 63] Figure 1 shows CTLA4 expression levels measured by mean fluorescence intensity (MFI) in FOXP3+CD4+Treg cells from CT26 tumor-bearing mice treated with isotype control antibody or TY21580. Each data point represents data from one mouse. Statistical analysis was performed using Prism 7 (GraphPad Software). P values ​​were calculated using multiple T-test. ns: P>0.05, **: 0.001 <P<0.01、***:P<0.001。 [Fig. 64A]Tumor growth curves of mice bearing mouse H22 liver cancer treated with TY21580 or isotype control antibody. A shows the group mean tumor growth when TY21580 treatment was initiated when tumors reached 500 mm3 or 800 mm3, or when isotype control antibody treatment was initiated when tumors reached 500 mm3. Data points represent the mean tumors of 8 mice / group, and error bars represent standard error of the mean (SEM). B-D show individual tumor growth in each mouse. B shows tumor growth in mice treated with isotype control antibody, where treatment was initiated when tumors reached 500 mm3. C shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 500 mm3. D shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 800 mm3. [Fig. 64B-D]Figure 64B: Tumor growth curves of mice bearing mouse H22 liver cancer treated with TY21580 or isotype control antibody. A shows the group mean tumor growth when TY21580 treatment was initiated when tumors reached 500 mm3 or 800 mm3, or when isotype control antibody treatment was initiated when tumors reached 500 mm3. Data points represent the mean tumors of 8 mice / group, and error bars represent standard error of the mean (SEM). B-D show individual tumor growth in each mouse. B shows tumor growth in mice treated with isotype control antibody, where treatment was initiated when tumors reached 500 mm3. C shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 500 mm3. D shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 800 mm3. Figure 64C: Tumor growth curves of mice bearing mouse H22 liver cancer treated with TY21580 or isotype control antibody. A shows the group mean tumor growth when TY21580 treatment was initiated when tumors reached 500 mm3 or 800 mm3, or when isotype control antibody treatment was initiated when tumors reached 500 mm3. Data points represent the mean tumors of 8 mice / group, and error bars represent standard error of the mean (SEM). B-D show individual tumor growth in each mouse. B shows tumor growth in mice treated with isotype control antibody, where treatment was initiated when tumors reached 500 mm3. C shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 500 mm3. D shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 800 mm3. Figure 64D: Tumor growth curves of mice bearing mouse H22 liver cancer treated with TY21580 or isotype control antibody. A shows the group mean tumor growth when TY21580 treatment was initiated when tumors reached 500mm3 or 800mm3, or when isotype control antibody treatment was initiated when tumors reached 500mm3. Data points represent the mean tumor size of 8 mice / group, and error bars represent the standard error of the mean (SEM).B-D show individual tumor growth in each mouse. B shows tumor growth in mice treated with isotype control antibody, where treatment was initiated when tumors reached 500 mm3. C shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 500 mm3. D shows tumor growth in mice treated with TY21580, where treatment was initiated when tumors reached 800 mm3. [Figure 65] Figure 1 shows the masking efficiency of exemplary activatable antibodies containing masking peptides of varying lengths compared to the parent antibody TY21580. Masking efficiency was determined using an ELISA-based method. A and B represent two experiments set up using the same experimental method to test various activatable anti-CTLA4 antibodies. [Figure 66] 1 shows the masking efficiency of exemplary activatable antibodies containing truncated peptides of different lengths compared to the parent antibody TY21580. Masking efficiency was determined using an ELISA-based method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] I. General techniques The techniques and procedures described or referenced herein are generally well understood by those of skill in the art and may be implemented using conventional methodology, e.g., as described in Sambrook et al., Molecular Cloning: A Laboratory Manual 3d edition (2001) Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, Current Protocols in Molecular Biology (FMA Usubel, et al. eds., (2003)), the series Methods in Enzymology (Academic Press, Inc.): PCR 2: A Practical Approach (MJ MacPherson, B.D. Hames and G.R. Taylor eds. (1995)), Harlow and Lane, eds. (1988) Antibodies, A Laboratory Manual, and Animal Cell Culture (R.I. Freshney, ed. (1987)), Oligonucleotide Synthesis (MJ Gait, ed., 1984), Methods in Molecular Biology, Humana Press, Cell Biology: A Laboratory Notebook (JECellis, ed., 1998) Academic Press, Animal Cell Culture (RIFreshney), ed., 1987), Introduction to Cell and Tissue Culture (JP Mather and PE Roberts, 1998) Plenum Press, Cell and Tissue Culture: Laboratory Procedures (A. Doyle, JBGriffiths, and DG Newell, eds., 1993-8) J. Wiley and Sons, Handbook of Experimental Immunology (DM Weir and CC Blackwell, eds.), Gene Transfer Vectors for Mammalian Cells (JMMiller and MPCalos, eds., 1987), PCR: The Polymerase Chain Reaction, (Mullis et al., eds., 1994), Current Protocols in Immunology (JEColigan et al., eds., 1991), Short Protocols in Molecular Biology (Wiley and Sons, 1999), Immunobiology (CA Janeway and P. Travers, 1997), Antibodies (P. Finch, 1997), Antibodies: A Practical Approach (D. Catty., ed., IRL Press, 1988-1989), Monoclonal Antibodies: A Practical Approach (P. Shepherd and C. Dean, eds., Oxford University Press, 2000), Using Antibodies: A Laboratory Manual (E.Harlow and D. Lane (Cold Spring Harbor Laboratory Press, 1999), The Antibodies (M. Zanetti and JD Capra, eds., Harwood Academic Publishers, 1995), and Cancer: Principles and Practice of Oncology (VT DeVita et al., eds., J.B. Lippincott Company, 1993) are generally used.

[0031] II. Definition Before describing the present disclosure in detail, it is to be understood that this disclosure is not limited to particular compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0032] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly indicates otherwise. Thus, for example, reference to "a molecule" includes any combination of two or more such molecules, and so forth.

[0033] As used herein, the term "about" refers to a normal range of error for the respective value, which would be readily understood by one of ordinary skill in the art. Reference herein to "about" a value or parameter includes (and describes) embodiments that are directed to the value or parameter itself.

[0034] It is to be understood that the aspects and embodiments of the present disclosure described herein include "comprising," "consisting," and "consisting essentially of" aspects and embodiments.

[0035] As used herein, the term "and / or" is intended to mean that phrases such as "A and / or B" include both A and B, A or B, A (single), and B (single). Similarly, as used herein, the term "and / or" is intended to mean that phrases such as "A, B, and / or C" include each of the following embodiments: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (single); B (single); and C (single).

[0036] The term "amino acid" refers to natural and synthetic amino acids, as well as amino acid analogs and amino acid mimetics that function similarly to natural amino acids. Natural amino acids are those encoded by the genetic code, as well as those amino acids that are subsequently modified, such as hydroxyproline, gamma-carboxyglutamate, and O-phosphoserine. The term "amino acid analog" refers to a compound that has the same basic chemical structure as a natural amino acid, but the C-terminal carboxy group, the N-terminal amino group, or a functional group on the side chain has been chemically modified to another functional group. The term "amino acid mimetic" refers to a chemical compound that has a structure that is different from the general chemical structure of an amino acid, but functions similarly to a natural amino acid. As used herein, the twenty conventional amino acids and their abbreviations follow conventional usage. See, for example, Immunology-A Synthesis (2nd Edition, E.S.Golub and D.R.Gren, Eds., Sinauer Associates, Sunderland, Mass. (1991)).

[0037] The terms "polypeptide," "protein," and "peptide" are used interchangeably herein and may refer to a polymer of two or more amino acids.

[0038] "Polynucleotide" or "nucleic acid", as used interchangeably herein, refers to a polymer of nucleotides of any length, including DNA and RNA. The nucleotides can be deoxyribonucleotides, ribonucleotides, modified nucleotides or bases, and / or their analogs, or any substrate that can be incorporated into a polymer by DNA or RNA polymerase or by a synthetic reaction. A polynucleotide can contain modified nucleotides, such as methylated nucleotides and their analogs. If present, modifications to the nucleotide structure can be imparted before or after assembly of the polymer. The sequence of nucleotides can be interrupted by non-nucleotide components. A polynucleotide can contain modification(s) made after synthesis, such as conjugation to a label. Other types of modifications include, for example, "caps" which replace one or more of the naturally occurring nucleotides with an analog, internucleotide modifications such as those with non-charged linkages (e.g., methylphosphonates, phosphotriesters, phosphoamidates, carbamates, etc.) and those with charged linkages (e.g., phosphorothioates, phosphorodithioates, etc.), those containing pendant moieties such as proteins (e.g., nucleases, toxins, antibodies, signal peptides, poly-L-lysine, etc.), those with intercalating agents (e.g., acridine, psoralen, etc.), those containing chelating agents (e.g., metals, radioactive metals, boron, metal oxides, etc.), those containing alkylating agents, those with modified linkages (e.g., alpha anomeric nucleic acids, etc.), as well as unmodified forms of the polynucleotide(s). Additionally, any of the hydroxyl groups normally present in the sugar may be replaced, for example, by phosphonate groups, phosphate groups, protected by standard protecting groups, or activated to prepare additional bonds to additional nucleotides, or conjugated to solid or semi-solid supports. The 5' and 3' terminal OH may be phosphorylated or replaced with amines or organic capping group moieties of 1-20 carbon atoms. Other hydroxyls may be derivatized to standard protecting groups.Polynucleotides can also contain analogous forms of ribose or deoxyribose sugars that are commonly known in the art, including, for example, 2'-O-methyl-, 2'-O-allyl, 2'-fluoro-, or 2'-azido-ribose, carbocyclic sugar analogs, α-anomeric sugars, epimeric sugars such as arabinose, xylose or lyxose, pyranose sugars, furanose sugars, sedoheptulose, acrylic acid analogs, and basic nucleoside analogs such as methyl riboside. One or more phosphodiester linkages can be replaced with alternative linking groups. These alternative linking groups include, but are not limited to, embodiments in which phosphate is replaced with P(O)S ("thioate"), P(S)S ("dithioate"), (O)NR2 ("amidate"), P(O)R, P(O)OR', CO, or CH2 ("formacetal"), where each R or R' is independently H or substituted or unsubstituted alkyl (1-20C) (optionally containing an ether (-O-) linkage), aryl, alkenyl, cycloalkyl, cycloalkenyl, or araldyl. Not all linkages in a polynucleotide need be identical. The preceding description applies to all polynucleotides referred to herein, including RNA and DNA.

[0039] The term "isolated nucleic acid" refers to a nucleic acid molecule of genomic, cDNA, or synthetic origin, or a combination thereof, that is separated from other nucleic acid molecules that are present in the natural source of the nucleic acid. For example, with respect to genomic DNA, the term "isolated" includes a nucleic acid molecule that is separated from the chromosome with which the genomic DNA is naturally associated. Preferably, an "isolated" nucleic acid is free of sequences that naturally flank the nucleic acid (i.e., sequences located at the 5' and 3' ends of the nucleic acid of interest).

[0040] The term "antibody" is used herein in the broadest sense and specifically covers monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies, trispecific antibodies), and antibody fragments (e.g., Fab, Fab', Fab'-SH, F(ab')2, Fv and / or single chain variable fragments or scFv), so long as they exhibit the desired biological activity.

[0041] In some embodiments, the term "antibody" refers to an antigen-binding protein (i.e., an immunoglobulin) with a basic four polypeptide chain structure consisting of two identical heavy (H) chains and two identical light (L) chains. Each L chain is linked to a H chain by one covalent disulfide bond, while the two H chains are linked to each other by one or more disulfide bonds depending on the H chain isotype. Each heavy chain contains a variable region (referred to herein as V) at the N-terminus. H The heavy chain constant region is divided into three domains, C H1 , C H2 and C H3 Each light chain consists of a variable region (referred to herein as V I The light chain constant region consists of one domain, C L It consists of. V L is V H Aligned with C L is aligned with the first constant domain (CH1) of the heavy chain. H and V L The pairings of the tetramers together form a single antigen-binding site. IgM antibodies consist of five basic heterotetrameric units plus an additional polypeptide called the J chain and thus contain 10 antigen-binding sites, whereas secreted IgA antibodies can polymerize to form multivalent assemblies containing two to five basic four-chain units plus the J chain.

[0042] V H and V LBased on structural and sequence analysis, the regions can be further subdivided into regions of hypervariability called hypervariable regions (HVRs). HVRs are interspersed with more conserved regions called framework regions (FWs) (see, e.g., Chen et al. (1999) J. Mol. Biol. (1999) 293, 865-881). H and V L is composed of three HVRs and four FWs, arranged from amino to carboxy terminus in the following order: FW-1_HVR-1_FW-2_HVR-2_FW-3_HVR-3_FW4. Throughout this disclosure, the three HVRs of the heavy chain are referred to as HVR-H1, HVR-H2, and HVR-H3. Similarly, the three HVRs of the light chain are referred to as HVR-L1, HVR-L2, and HVR-L3.

[0043] The variable regions of the heavy and light chains contain a binding domain that interacts with an antigen. The constant region of the antibody may mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component (C1q) of the classical complement system. Within the light and heavy chains, the variable and constant regions are joined by a "J" region of about 12 or more amino acids, with the heavy chains also including a "D" region of about 10 or more amino acids (see, e.g., Fundamental Immunology Ch. 7 (Paul, W., ed., 2002). nd ed. Raven Press, NY (1989).

[0044] L chains from any vertebrate species can be assigned to one of two clearly distinct types, called kappa and lambda, based on the amino acid sequence of their constant domains. Antibodies can be assigned to different classes or isotypes depending on the amino acid sequence of the constant domain of their heavy chains (CH). There are five classes of antibodies: IgA, IgD, IgE, IgG, and IgM, with heavy chains designated α (alpha), δ (delta), ε (epsilon), γ (gamma), and μ (mu), respectively. The IgG class of antibodies can be further classified into four subclasses, IgG1, IgG2, IgG3, and IgG4, by the gamma heavy chains Y1-Y4, respectively.

[0045] The term "antibody derivative" or "derivative" of an antibody refers to a molecule that can bind to the same antigen (e.g., CTLA4) that the antibody binds and that contains the amino acid sequence of the antibody linked to an additional molecular entity. The amino acid sequence of the antibody contained in the antibody derivative can be the full-length heavy chain, the full-length light chain, any portion(s) of the full-length heavy chain, any portion(s) of the full-length light chain of the antibody, any other fragment(s) of the antibody, or a complete antibody. The additional molecular entity can be a chemical or biological molecule. Examples of additional molecular entities include chemical groups, amino acids, peptides, proteins (enzymes, antibodies, etc.), and chemical compounds. The additional molecular entity can have any utility, such as use as a detection agent, label, marker, pharmaceutical or therapeutic agent. The amino acid sequence of the antibody can be attached or linked to the additional molecular entity by chemical coupling, genetic fusion, non-covalent bonding, etc. The term "antibody derivative" also encompasses chimeric antibodies, humanized antibodies, and molecules derived from modifications of the amino acid sequence of the CTLA4 antibody, such as conservative amino acid substitutions, additions, and insertions.

[0046] The term "antigen-binding fragment" or "antigen-binding portion" of an antibody refers to one or more portions of an antibody that retain the ability to bind to the antigen to which the antibody binds (e.g., CTLA4). Examples of "antigen-binding fragments" of antibodies include: (i) V L ,,V H , C L , and CH1 (ii) a F(ab')2 fragment, which is a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; and (iii) a V H and C H1 (iv) an Fd fragment consisting of the V domain of a single arm of an antibody; L and V H (v) an Fv fragment consisting of a V H domains (Ward et al., Nature 341:544-546 (1989)), and (vi) isolated complementarity determining regions (CDRs).

[0047] The term "binding molecule" includes (1) antibodies, (2) antigen-binding fragments of antibodies, and (3) derivatives of antibodies, each of which is defined herein.

[0048] The term "CTLA4" is used in this application to include human CTLA4 (e.g., UniProt Accession No. P16410), as well as variants, isoforms, and species homologs thereof (e.g., mouse CTLA4 (UniProt Accession No. P09793), rat CTLA4 (UniProt Accession No. Q9Z1A7), canine CTLA4 (UniProt Accession No. Q9XSI1), cynomolgus monkey CTLA4 (UniProt Accession No. G7PL88), etc.). Thus, as defined and disclosed herein, a binding molecule (e.g., an antibody or activatable antibody) may also bind to CTLA4 from species other than human. In other cases, a binding molecule may be completely specific for human CTLA4 and may not exhibit species or other type cross-reactivity.

[0049] As defined herein, the term "CTLA4 antibody" refers to an antibody capable of binding to human CTLA4.

[0050] The term "chimeric antibody" refers to an antibody that contains amino acid sequences derived from different animal species, such as those having a variable region derived from a human antibody and a murine immunoglobulin constant region.

[0051] The term "compete for binding" refers to the interaction of two antibodies in binding to a binding target. A first antibody competes with a second antibody for binding if the binding of the first antibody to its cognate epitope is detectably reduced in the presence of the second antibody compared to the binding of the first antibody in the absence of the second antibody. The alternative that the binding of the second antibody to its epitope is also detectably reduced in the presence of the first antibody can be, but need not be, the case. That is, a first antibody can inhibit the binding of a second antibody to its epitope without the second antibody inhibiting the binding of the first antibody to its respective epitope. However, if each antibody detectably inhibits the binding of the other antibody to its cognate epitope, whether to the same extent, more or less, the antibodies are said to "cross-compete" with each other for binding of their respective epitope(s).

[0052] The term "epitope" refers to a portion of an antigen to which an antibody (or an antigen-binding fragment thereof) binds. Epitopes can be formed from both contiguous amino acids or non-contiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained upon exposure to denaturing solvents, whereas epitopes formed by tertiary folding are typically lost upon treatment with denaturing solvents. Epitopes can include a variable number of amino acids in unique spatial conformations. Methods for determining the spatial conformation of an epitope include, for example, X-ray crystallography, 2D nuclear magnetic resonance, deuterium and hydrogen exchange combined with mass spectrometry, or site-directed mutagenesis, or any method used in combination with a computational model of the antigen and its complex structure with its bound antibody and its variants (see, for example, Epitope Mapping Protocols in Methods in Molecular Biology, Vol. 66, GE Morris, Ed. (1996)). Once the desired epitope of an antigen is determined, antibodies against that epitope can be generated, for example, using the techniques described herein. Antibody generation and characterization can also elucidate information about the desired epitope. From this information, it is possible to competitively screen antibodies for binding to the same epitope. An approach to achieve this is to perform cross-competition studies to find antibodies that competitively bind to each other, i.e., the antibodies compete for binding to the antigen. A high-throughput process for "binning" antibodies based on their cross-competition is described in PCT Publication No. WO03 / 48731.

[0053] The term "germline" refers to the nucleotide sequences of antibody genes and gene segments that are inherited from parents to offspring via germ cells. Germline sequences are distinguished from the nucleotide sequences that encode antibodies in mature B cells that have been altered by recombination and hypermutation events during the B cell maturation process.

[0054] The term "glycosylation site" refers to an amino acid residue that is recognized by a eukaryotic cell as a location for the attachment of a sugar residue. The amino acids to which carbohydrates, such as oligosaccharides, are attached are typically asparagine (N-linked), serine (O-linked), and threonine (O-linked) residues. The particular attachment site is typically signaled by a sequence of amino acids, referred to herein as a "glycosylation site sequence." The glycosylation site sequence for N-linked glycosylation is -Asn-X-Ser- or -Asn-X-Thr-, where X can be any conventional amino acid except proline. The terms "N-linked" and "O-linked" refer to chemical groups that serve as attachment sites between a sugar molecule and an amino acid residue. N-linked sugars are attached through an amino group. O-linked sugars are attached through a hydroxyl group. The term "glycan occupancy" refers to the presence of a carbohydrate moiety linked to a glycosylation site (i.e., the glycan site is occupied). When there are at least two potential glycosylation sites on a polypeptide, either zero (0-glycan site occupation), one (1-glycan site occupation), or both (2-glycan site occupation) sites can be occupied by carbohydrate moieties.

[0055] The term "host cell" refers to a cell line that can be engineered to produce a protein, protein fragment, or peptide of interest. Host cells include, but are not limited to, cultured cells, e.g., mammalian cultured cells derived from rodents (rat, mouse, guinea pig, or hamster), such as CHO, BHK, NSO, SP2 / 0, YB2 / 0; human cells (e.g., HEK293F cells, HEK293T cells; or human tissue or hybridoma cells, yeast cells, insect cells (e.g., S2 cells), bacterial cells (e.g., E. coli cells), as well as cells contained within transgenic animals or cultured tissues. This term encompasses not only the particular subject cell, but also the progeny of such cells. Since certain modifications may occur in subsequent generations due to either mutations or environmental influences, such progeny may not be identical to the parent cell, but are still included within the scope of the term "host cell".

[0056] A "human antibody" is one that possesses the amino acid sequence of an antibody produced by a human or human cell, or derived from a non-human source that utilizes the human antibody repertoire, or an amino acid sequence that corresponds to other human antibody coding sequences. This definition of a human antibody specifically excludes humanized antibodies which contain non-human antigen-binding residues.

[0057] The term "humanized antibody" refers to a chimeric antibody that contains amino acid residues derived from human antibody sequences. A humanized antibody may contain some or all of the CDRs or HVRs from a non-human animal or synthetic antibody, but the framework and constant regions of the antibody contain amino acid residues derived from human antibody sequences.

[0058] The term "exemplary antibody" refers to any one of the antibodies described in this disclosure and named as listed in Tables A and B, as well as any antibody that contains the six HVRs and / or VHs and VLs of the antibodies listed in Tables A and B. These antibodies can be of any class (e.g., IgA, IgD, IgE, IgG, and IgM). Thus, each of the antibodies identified above includes the V L and V H The present invention encompasses antibodies of all five classes that have the same amino acid sequence for the V domain. Furthermore, antibodies of the IgG class can be of any subclass (e.g., IgG1, IgG2, IgG3, and IgG4). Thus, each of the above-identified antibodies of the IgG subclasses includes the V L and V H It includes antibodies of all four subclasses that have the same amino acid sequence for that region. The amino acid sequences of the heavy chain constant regions of human antibodies in the five classes as well as the four IgG subclasses are known in the art.

[0059] An "isolated" antibody or binding molecule (e.g., an activatable antibody) is one that has been separated from a component of its natural environment. In some embodiments, the antibody is purified to greater than 95% or 99% purity, for example, as determined by electrophoresis (e.g., SDS-PAGE, isoelectric focusing (IEF), capillary electrophoresis), or chromatography (e.g., ion exchange or reverse-phase HPLC). For a review of methods for assessing antibody purity, see, for example, Flatman et al., J. Chromatogr. B 848:79-87 (2007).

[0060] The term “K a " refers to the association rate constant of a particular binding molecule-antigen interaction, d " refers to the dissociation rate constant of a particular binding molecule-antigen interaction.

[0061] "K D The term "dissociation constant" refers to the equilibrium dissociation constant of a particular antibody-antigen interaction. This is k d vs. k a The ratio of (i.e., k d / k a ) and expressed as molar concentration (M). D is used as a measure of the affinity of binding of an antibody to a binding partner. D The smaller the K, the stronger the antibody binds, or the higher the affinity between the antibody and the antigen. For example, an antibody with a nanomolar (nM) dissociation constant will bind to a particular antigen more strongly than an antibody with a micromolar (μM) dissociation constant. D Values ​​can be determined using methods well established in the art. D One method for determining is by using surface plasmon resonance, typically by using a biosensor system such as a Biacore® system. For example, an assay procedure using the BIACORE™ system (BIAcore assay) is described in at least Example 3 of the present disclosure.

[0062] The term "mammal" refers to any animal species of the mammalian class. Examples of mammals include humans; laboratory animals such as rats, mice, hamsters, rabbits, non-human primates, and guinea pigs; farm animals such as cats, dogs, cows, sheep, goats, horses, and pigs; and captive wild animals such as lions, tigers, and elephants.

[0063] The terms "prevent" or "prophylaxis" in reference to a particular disease state in a mammal refer to preventing or delaying the onset of the disease or preventing the manifestation of its clinical or subclinical symptoms.

[0064] As used herein, "sequence identity" between two polypeptide sequences refers to the percentage of amino acids that are identical between sequences.The amino acid sequence identity of polypeptides can be determined conventionally using known computer programs such as Bestfit, FASTA, or BLAST (see, for example, Pearson, Methods Enzymol.183:63-98(1990); Pearson, Methods Mol.Biol.132:185-219(2000); Altschul et al., J.Mol.Biol.215:403-410(1990); Altschul et al., Nucleic Acids Res.25:3389-3402(1997)). When using Bestfit or any other sequence alignment program to determine whether a particular sequence is, for example, 95% identical to a reference amino acid sequence, parameters are set such that the percentage of identity is calculated over the entire length of the reference amino acid sequence, allowing a difference in homology of up to 5% of the total number of amino acid residues in the reference sequence. This aforementioned method of determining the percentage of identity between polypeptides is applicable to all proteins, fragments, or variants thereof disclosed herein.

[0065] As used herein, the terms "bind", "bind to", "specifically bind", "specifically bind to" or "specific for" refer to a measurable and reproducible interaction, such as binding between a target and an antibody, that determines the presence of the target in the presence of a heterogeneous population of molecules, including biological molecules. For example, an antibody that binds or specifically binds to a target (which may be an epitope) is an antibody that binds to this target with higher affinity, avidity, more readily, and / or for longer than it binds to other targets. In one embodiment, the extent of binding of an antibody to an unrelated target is less than about 10% of the binding of the antibody to the target, as measured, for example, by radioimmunoassay (RIA). In certain embodiments, an antibody that specifically binds to a target has a dissociation constant (Kd) of 1 μM or less, 100 nM or less, 10 nM or less, 1 nM or less, or 0.1 nM or less. In certain embodiments, an antibody specifically binds to an epitope on a protein that is conserved among proteins from different species. In another embodiment, specific binding can include, but does not require, exclusive binding.

[0066] The terms "treat", "treating" or "treatment" refer to a particular disease state in a mammal, and to causing a desired or beneficial effect in a mammal having a disease state. A desired or beneficial effect may include a reduction in the frequency or severity of one or more symptoms of the disease (i.e., tumor growth and / or metastasis, or other effects mediated by immune cell numbers and / or activity, etc.), or preventing or inhibiting further progression of the disease, condition, or disorder. In the context of treating cancer in a mammal, a desired or beneficial effect may include inhibiting further growth or metastasis of cancer cells, killing cancer cells, inhibiting recurrence of cancer, reducing pain associated with cancer, or improving the survival of the mammal. The effect may be either subjective or objective. For example, if the mammal is a human, the human may perceive improved vitality or survival, or reduced pain, as subjective symptoms of improvement or response to treatment. Alternatively, the clinician may perceive a reduction in tumor size or burden based on physical examination, clinical laboratory values, tumor markers, or x-ray findings. Some clinical signs that a clinician may observe regarding a therapeutic response include normalization of laboratory values ​​such as white blood cell count, red blood cell count, platelet count, erythrocyte sedimentation rate, and various enzyme levels. In addition, a clinician may observe a decrease in detectable tumor markers. Alternatively, other tests, such as ultrasound imaging, nuclear magnetic resonance imaging, and positron emission tomography, may be used to assess objective improvement.

[0067] The term "vector" refers to a nucleic acid molecule capable of transporting a foreign nucleic acid molecule. The foreign nucleic acid molecule is linked to the vector nucleic acid molecule by recombinant techniques such as ligation or recombination. This allows the foreign nucleic acid molecule to be propagated, selected, further manipulated, or expressed in a host cell or organism. The vector can be a plasmid, phage, transposon, cosmid, chromosome, virus, or virion. Some types of vectors can be integrated into the genome of the host cell upon introduction into the host cell, and are thereby replicated along with the host genome (e.g., non-episomal mammalian vectors). Other types of vectors are capable of autonomous replication in the host cell into which they are introduced (e.g., bacterial vectors and episomal mammalian vectors having a bacterial origin of replication). Another specific type of vector capable of directing the expression of an expressible foreign nucleic acid to which they are operably linked is usually referred to as an "expression vector". Expression vectors generally have control sequences that drive the expression of an expressible foreign nucleic acid. Simpler vectors, known as "transcription vectors", are capable of only transcription but not translation, and they can replicate but not express in target cells. The term "vector" encompasses all types of vectors, regardless of their function. Vectors capable of directing the expression of an expressible nucleic acid to which they are operatively linked are commonly referred to as "expressible vectors." Other examples of "vectors" can include display vectors (e.g., vectors that direct the expression and display of an encoded polypeptide on the surface of a virus or a cell, such as a bacterial cell, yeast cell, insect cell, and / or mammalian cell).

[0068] As used herein, a "subject," "patient," or "individual" may refer to a human or non-human animal. A "non-human animal" may refer to any animal not classified as a human, such as farm animals, livestock, or zoo animals, sport animals, pet animals (e.g., dogs, horses, cats, cows, etc.), and animals used in research. A research animal may refer to, but is not limited to, nematodes, arthropods, vertebrates, mammals, frogs, rodents (e.g., mice or rats), fish (e.g., zebrafish or pufferfish), birds (e.g., chickens), dogs, cats, and non-human primates (e.g., rhesus monkeys, cynomolgus monkeys, chimpanzees, etc.). In some embodiments, the subject, patient, or individual is a human.

[0069] "Effective amount" refers to at least an amount effective at the dosage and for the period of time necessary to achieve one or more desired or indicated effects, including therapeutic or prophylactic results. An effective amount may be provided in one or more administrations. For purposes of this disclosure, an effective amount of an antibody, drug, compound, or pharmaceutical composition is an amount sufficient to directly or indirectly achieve prophylactic or therapeutic treatment. As understood in a clinical context, an effective amount of a drug, compound, or pharmaceutical composition may or may not be achieved in conjunction with another drug, compound, or pharmaceutical composition (e.g., an effective amount when administered as a monotherapy or combination therapy). Thus, an "effective amount" may be considered in the context of administration of one or more therapeutic agents, and a single agent may be considered to be given in an effective amount if a desired result can or is achieved when combined with one or more other agents.

[0070] III. Binding Molecules that Bind Human CTLA4 The present disclosure relates in part to isolated binding molecules that bind human CTLA4, including CTLA4 antibodies, antigen-binding fragments of CTLA4 antibodies, and derivatives of CTLA4 antibodies. In some embodiments, the binding molecule is any of the antibodies described herein, including those described with respect to the HVRs, variable regions (VL, VH), and specific amino acid sequences of the light and heavy chains (e.g., IgG1, IgG2, IgG4). In some embodiments, the antibody is a human antibody. In some embodiments, the antibody is a humanized antibody and / or a chimeric antibody. In some embodiments, the present disclosure provides an antibody that binds human CTLA4 and has the following functional properties: (a) a K of 500 nM or less for human, cynomolgus monkey, mouse, rat, and / or dog CTLA4; D(b) has antagonist activity against human CTLA4; (c) does not bind to human PD-1, PD-L1, PD-L2, LAG3, TIM3, B7-H3, CD95, CD120a, OX40, CD40, BTLA, VISTA, ICOS, and / or B7-H4 at concentrations up to 100 nM; (d) is cross-reactive with monkey, mouse, rat, and / or dog CTLA4; (e) induces an ADCC effect (e.g., against Tregs); and (f) activates human PBMCs. The present invention relates to binding molecules having at least one of the following properties (e.g., at least one, at least two, at least three, at least four, at least five, at least six, at least seven, at least eight, or all nine): (i) activating (e.g., stimulating secretion of IL-2 and / or IFNγ), (g) being capable of inhibiting tumor cell proliferation, (h) having a therapeutic effect against cancer, and (i) blocking binding of human CTLA4 to human CD80 and / or human CD86. In some embodiments, the anti-CTLA4 antibodies described herein have less activity in blocking binding of CD80 and / or CD86 to human CTLA4 compared to ipilimumab in assays where either human CD80 and / or CD86 are immobilized (or plate-bound) or where human CTLA4 protein is present on the cell surface. See Figures 57C and 57D and Figure 58. In some embodiments, the anti-CTLA4 antibodies described herein selectively deplete Treg cells in the tumor microenvironment compared to Treg depletion in PBMCs or spleen. In some embodiments, the anti-CTLA4 antibodies described herein have higher Treg depletion activity in the tumor microenvironment compared to ipilimumab. See Figures 61A-B, 62A-B, and 63. Also provided herein is one or more anti-CTLA4 antibodies or antigen-binding fragments that cross-compete with one or more of the antibodies or antigen-binding fragments described herein for binding to human CTLA4.

[0071] In some embodiments, the antibody or antigen-binding fragment has a K for human, cynomolgus monkey, mouse, rat, and / or dog CTLA4 of about 500 nM or less (e.g., about 500 nM or less, about 450 nM or less, about 400 nM or less, about 350 nM or less, about 300 nM or less, about 250 nM or less, about 200 nM or less, about 150 nM or less, about 100 nM or less, about 90 nM or less, about 80 nM or less, about 70 nM or less, about 60 nM or less, about 50 nM or less, about 40 nM or less, about 30 nM or less, about 25 nM or less, about 20 nM or less, about 10 nM or less, about 1 nM or less, about 0.1 nM or less, etc.). D In some embodiments, the antibody or antigen-binding fragment binds to human, cynomolgus monkey, mouse, rat, and / or dog CTLA4 with a K of about 350 nM or less. D In some embodiments, the antibody or antigen-binding fragment binds with a K of about 100 nM or less. D In some embodiments, the antibody or antigen-binding fragment binds to human CTLA4 with a K of about 50 nM or less. D In some embodiments, the antibody or antigen-binding fragment binds to human CTLA4 with a K of about 10 nM or less. D The K of the antibody or antigen-binding fragment binds to human CTLA4. D Methods for measuring K can be performed using any method known in the art, including, for example, by surface plasmon resonance, ELISA, isothermal titration calorimetry, filter binding assays, EMSA, etc. In some embodiments, K D is measured by surface plasmon resonance or ELISA (see, for example, Example 3 below).

[0072] In some embodiments, the antibodies or antigen-binding fragments described herein have antagonist activity against human CTLA4. In some embodiments, the antibodies or antigen-binding fragments inhibit one or more activities of human CTLA4 (e.g., CTLA4 blockade as measured by an increase in reporter gene signal using a CLA4 blockade reporter gene assay) when a cell expressing human CTLA4 (e.g., a human cell) is contacted by the antibody or antigen-binding fragment.

[0073] In some embodiments, the antibody or antigen-binding fragment is cross-reactive with monkey (e.g., cynomolgus), mouse, rat, and / or dog CTLA4. In some embodiments, the antibody or antigen-binding fragment is cross-reactive with monkey CTLA4. In some embodiments, the antibody or antigen-binding fragment is cross-reactive with mouse CTLA4. In some embodiments, the antibody or antigen-binding fragment is cross-reactive with rat CTLA4. In some embodiments, the antibody or antigen-binding fragment is cross-reactive with dog CTLA4. In some embodiments, the antibody or antigen-binding fragment is cross-reactive with monkey and mouse CTLA4; monkey and rat CTLA4; monkey and dog CTLA4; mouse and rat CTLA4; mouse and dog CTLA4; rat and dog CTLA4; monkey, mouse, and rat CTLA4; monkey, rat, and dog CTLA4; mouse, rat, and dog CTLA4; or monkey, mouse, rat, and dog CTLA4. In some embodiments, the antibody or antigen-binding fragment binds to a non-human CTLA4 molecule with a K of less than about 500 nM (e.g., less than about 1 nM, less than about 10 nM, less than about 25 nM, less than about 50 nM, less than about 75 nM, less than about 100 nM, less than about 150 nM, less than about 200 nM, less than about 250 nM, less than about 300 nM, less than about 350 nM, etc.). D If the antibody binds at the 5'-terminal end of ...

[0074] In some embodiments, the antibody induces an ADCC effect on CTLA4 expressing cells (e.g., on CTLA4 expressing human cells such as Tregs) after the antibody binds to the cells expressing CTLA4. Methods (e.g., in vitro methods) for measuring ADCC effect are known in the art, including, but not limited to, by the methods described in Example 3 below. In some embodiments, the antibody induces an ADCC effect of more than about 10% compared to a control (e.g., an isotype control or ipilimumab) (e.g., induces ADCC of more than about 10%, more than about 15%, more than about 20%, more than about 25%, more than about 30%, more than about 35%, more than about 40%, etc.).

[0075] In some embodiments, the antibody or antigen-binding fragment can inhibit tumor cell growth and / or proliferation. In some embodiments, tumor cell growth and / or proliferation is inhibited by at least about 5% (e.g., at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 99%) when contacted with the antibody or antigen-binding fragment compared to corresponding tumor cells not contacted with the antibody or antigen-binding fragment (or compared to corresponding tumor cells contacted with an isotype control antibody). In some embodiments, the antibody or antigen-binding fragment can reduce tumor volume in a subject when the antibody or antigen-binding fragment is administered to the subject. In some embodiments, the antibody or antigen-binding fragment can reduce tumor volume in a subject by at least about 5% (e.g., at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 99%) compared to the initial tumor volume in the subject (e.g., compared to a corresponding tumor in a subject administered an isotype control antibody prior to administration of the antibody or antigen-binding fragment). Methods for monitoring tumor cell growth / proliferation, tumor volume, and / or tumor inhibition are known in the art, including, for example, by the methods described in Example 4 below.

[0076] In some embodiments, the antibody or antigen-binding fragment has a therapeutic effect against cancer. In some embodiments, the antibody or antigen-binding fragment relieves one or more signs or symptoms of cancer. In some embodiments, a subject suffering from cancer undergoes partial or complete remission when administered the antibody or antigen-binding fragment.

[0077] In another aspect, the present disclosure provides an isolated antibody that competes or cross-competes with any of the exemplary antibodies of the present disclosure, e.g., TY21585, TY21586, TY21587, TY21588, TY21589, TY21580, TY21591, TY21686, TY21687, TY21689, TY21680, TY21691, and / or TY21692, for binding to human CTLA4. In certain embodiments, the present disclosure provides an isolated antibody that competes or cross-competes with any of the exemplary antibodies of the present disclosure for binding to the same epitope on human CTLA4. The ability of an antibody to compete or cross-compete for binding with another antibody can be determined using standard binding assays known in the art, such as BIAcore analysis, ELISA assays, or flow cytometry. For example, the exemplary antibodies of the present disclosure can be allowed to bind to human CTLA4 under saturating conditions, and then the ability of the test antibody to bind to CTLA4 can be measured. If the test antibody can bind to CTLA4 at the same time as the exemplary antibody, then the test antibody binds to a different epitope than the exemplary antibody. However, if the test antibody cannot bind to CTLA4 at the same time, then the test antibody binds to the same epitope, an overlapping epitope, or an epitope that is very close to the epitope bound by the exemplary antibody. This experiment can be performed using a variety of methods, such as ELISA, RIA, FACS, or surface plasmon resonance.

[0078] In some embodiments, the antibody or antigen-binding fragment blocks the binding between CTLA4 and one or more of its binding partners (e.g., human CTLA4 and human CD80, human CTLA4 and human CD86). In some embodiments, the antibody or antigen-binding fragment blocks the binding between CTLA4 and its ligand in vitro. In some embodiments, the antibody or antigen-binding fragment has a half maximal inhibitory concentration (IC) of about 500 nM or less (e.g., about 500 nM or less, about 400 nM or less, about 300 nM or less, about 200 nM or less, about 100 nM or less, about 50 nM or less, about 25 nM or less, about 10 nM or less, about 1 nM or less, etc.) for blocking CTLA4 binding to CD80 and / or CD86. 50 In some embodiments, the antibody or antigen-binding fragment has a half maximal inhibitory concentration (IC) of about 100 nM or less for blocking CTLA4 binding to CD80 and / or CD86. 50 ). In some embodiments, the antibody or antigen-binding fragment completely blocks binding of human CTLA4 to CD80 and / or CD86 when provided at a concentration of about 100 nM or more (e.g., about 100 nM or more, about 500 nM or more, about 1 μM or more, about 10 μM or more, etc.). As used herein, the term "complete blocking" or "completely blocks" refers to the ability of an antibody or antigen-binding fragment to reduce binding between a first protein and a second protein by at least about 80% (e.g., at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99%, etc.). Methods for measuring the ability of an antibody or antigen-binding fragment to block binding of a first protein (e.g., human CTLA4) and a second protein (e.g., human CD80 or human CD86) are known in the art and include, but are not limited to, BIAcore analysis, ELISA assays, and by flow cytometry (see, e.g., Example 3 below). In some embodiments, the anti-CTLA4 antibodies described herein have less activity in blocking ligand binding than ipilimumab.

[0079] CTLA4 antibody In some aspects, the disclosure provides an isolated antibody that binds to human CTLA4. In some embodiments, the antibody has a K of 1000 nM or less (e.g., 50 nM or less, 10 nM or less) as measured by surface plasmon resonance. D In some embodiments, the antibody is cross-reactive with at least one non-human species selected from cynomolgus monkey, mouse, rat, and dog.

[0080] In some aspects, the disclosure provides isolated antibodies that specifically bind to an epitope similar to the ligand binding site of human CTLA4. In some embodiments, the antibody specifically binds to an epitope similar to the CD80 binding site of human CTLA4. In some embodiments, the antibody specifically binds to an epitope similar to the CD86 binding site of human CTLA4. In some embodiments, the antibody specifically binds to an epitope that includes one or more amino acid residues in the ligand binding site (e.g., the CD80 and / or CD86 binding site) of human CTLA4. In some embodiments, the antibody specifically binds to an epitope on human CTLA4 that is distinct from the epitope of ipilimumab. In some embodiments, the epitope does not include an amino acid residue in the CC' loop motif of human CTLA4. In some embodiments, the epitope does not include amino acid residues L106 or I108 of human CTLA4. In some embodiments, the antibody specifically binds to an epitope comprising amino acid residues Y105 and L106 but not I108 of human CTLA4, where the amino acid residue numbering is according to SEQ ID NO:207. KAMHVAQPAVVLASSRGIASFVCEYASPGKATEVRVTVLRQADSQVTEVCAATYMMGNELTFLDDSICTGTSSGNQVNLTIQGLRAMDTGLYICKVELMYPPPYYLGIGNGTQIYVIDPE (SEQ ID NO: 207)

[0081] In one aspect, the disclosure provides an isolated antibody comprising a heavy chain variable region and a light chain variable region, wherein a) the heavy chain variable region comprises HVR-H1, HVR-H2, and HVR-H3, wherein HVR-H1 is selected from the group consisting of a heavy chain variable region having a sequence represented by formula (I): X1TFSX2YX3IHWV (SEQ ID NO: 1), where X1 is F or Y, X2 is D or G, and X3 is A, G, or W; a light chain variable region having a sequence represented by formula (II): YSIX1SGX2X3WX4WI (SEQ ID NO: 2), where X1 is S or T, X2 is H or Y, X3 is H or Y, and X4 is A, D, or S; and a light chain variable region having a sequence represented by formula (I): II): FSLSTGGVAVX1WI (SEQ ID NO: 3) (wherein X1 is G or S), and HVR-H2 comprises an amino acid sequence according to a formula selected from formula (IV): IGX1IX2HSGSTYYSX3SLKSRV (SEQ ID NO: 4) (wherein X1 is D or E, X2 is S or Y, and X3 is P or Q), formula (V): IGX1ISPSX2GX3TX4YAQKFQGRV (SEQ ID NO: 5) (wherein X1 is I or W, X2 is G or S, X3 is G or S, and X4 is K or N), and formula (VI): and HVR-H3 comprises an amino acid sequence according to a formula selected from the group consisting of: VSX1ISGX2GX3X4TYYADSVKGRF (SEQ ID NO: 6) (wherein X1 is A, G, or S, X2 is S or Y, X3 is G or S, and X4 is S or T), and HVR-H4 comprises an amino acid sequence according to a formula selected from the group consisting of: ARX1X2X3X4FDX5 (SEQ ID NO: 7) (wherein X1 is G, R, or S, X2 is A, I, or Y, X3 is D, V, or Y, X4 is A, E, or Y, and X5 is I or Y), or formula (VIII): ARX1GX2GYFDX3 ( SEQ ID NO:8) (wherein X1 is D or L, X2 is F or Y, and X3 is V or Y), formula (IX): ARX1X2X3X4AX5X6FDY (SEQ ID NO:9) (wherein X1 is L or R, X2 is I or P, X3 is A or Y, X4 is S or T, X5 is T or Y, and X6 is A or Y), and formula (X): ARDX1X2X3GSSGYYX4GFDX5 (SEQ ID NO:10) (wherein X1 is I or V, X2 is A or H, X3 is P or S, and X4 is D or Y,and X5 is F or V; and / or b) the light chain variable region comprises an amino acid sequence according to a formula selected from HVR-L1, HVR-L2, and HVR-L3, wherein HVR-L1 is selected from the group consisting of formula (XI): RASQX1X2X3SX4LX5 (SEQ ID NO: 11), where X1 is G or S, X2 is I or V, X3 is G or S, X4 is S or Y, and X5 is A or N; formula (XII): RASQX1VX2X3RX4LA (SEQ ID NO: 12), where X1 is G or S, X2 is I or V, X3 is G or S, X4 is S or Y, and X5 is A or N. X1 is S or T, X2 is F, R, or S, X3 is G or S, and X4 is F or Y; and formula (XIII): RASX1SVDFX2GX3SFLX4 (SEQ ID NO: 13), where X1 is E or Q, X2 is D, F, H, or Y, X3 is F, I, or K, and X4 is A, D, or H; and HVR-L2 comprises an amino acid sequence according to a formula selected from the group consisting of: X1ASX2X3X4X5GX6 (SEQ ID NO: 14), X1 is A or D, X2 is N, S, or T, X3 is L or R, X4 is A, E, or Q, X5 is S or T, and X6 is I or V; and HVR-L3 comprises an amino acid sequence according to the formula (XV): YCX1X2X3X4X5X6PX7T (SEQ ID NO: 15), wherein X1 is E, Q, or V, X2 is H or Q, X3 is A, G, H, R, or S, X4 is D, L, S, or Y, and X5 is E, G, P, Q. or S, X6 is L, T, V, or W, and X7 is F, L, P, W, or Y), formula (XVI): YCQQX1X2X3WPPWT (SEQ ID NO: 16) (wherein X1 is S or Y, X2 is D or Y, and X3 is Q or Y), and formula (XVII): YCQX1YX2SSPPX3YT (SEQ ID NO: 17) (wherein X1 is H or Q, X2 is T or V, and X3 is E or V).

[0082] In some embodiments, the antibody comprises (a) HVR-H1 comprising an amino acid sequence selected from SEQ ID NOs: 18-29, HVR-H2 comprising an amino acid sequence selected from SEQ ID NOs: 30-39, and HVR-H3 comprising an amino acid sequence selected from SEQ ID NOs: 40-52, and / or (b) HVR-L1 comprising an amino acid sequence selected from SEQ ID NOs: 53-65, HVR-L2 comprising an amino acid sequence selected from SEQ ID NOs: 66-69, and HVR-L3 comprising an amino acid sequence selected from SEQ ID NOs: 70-81. In some embodiments, the antibody comprises one, two, three, four, five, or all six of the HVRs set forth for any of the exemplary antibodies described in Table A below. TIFF0007678841000002.tif242170TIFF0007678841000003.tif255170

[0083] In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 18, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 30, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 40, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 53, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 70. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 19, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 31, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 41, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 54, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 71. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 20, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 32, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 42, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 55, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 72. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 21, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 33, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 43, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 56, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 68, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 73. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 22, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 34, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 44, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 57, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 74. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 23, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 35, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 45, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 58, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 75.In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 24, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 32, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 46, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 59, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 76. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 25, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 36, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 47, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 60, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 69, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 77. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO:26, HVR-H2 comprising the amino acid sequence of SEQ ID NO:37, HVR-H3 comprising the amino acid sequence of SEQ ID NO:48, HVR-L1 comprising the amino acid sequence of SEQ ID NO:61, HVR-L2 comprising the amino acid sequence of SEQ ID NO:66, and HVR-L3 comprising the amino acid sequence of SEQ ID NO:78. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO:27, HVR-H2 comprising the amino acid sequence of SEQ ID NO:32, HVR-H3 comprising the amino acid sequence of SEQ ID NO:49, HVR-L1 comprising the amino acid sequence of SEQ ID NO:62, HVR-L2 comprising the amino acid sequence of SEQ ID NO:67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO:79. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO:28, HVR-H2 comprising the amino acid sequence of SEQ ID NO:37, HVR-H3 comprising the amino acid sequence of SEQ ID NO:50, HVR-L1 comprising the amino acid sequence of SEQ ID NO:63, HVR-L2 comprising the amino acid sequence of SEQ ID NO:67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO:80. In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO:18, HVR-H2 comprising the amino acid sequence of SEQ ID NO:38, HVR-H3 comprising the amino acid sequence of SEQ ID NO:51, HVR-L1 comprising the amino acid sequence of SEQ ID NO:64, HVR-L2 comprising the amino acid sequence of SEQ ID NO:67, and HVR-L3 comprising the amino acid sequence of SEQ ID NO:81.In some embodiments, the antibody comprises HVR-H1 comprising the amino acid sequence of SEQ ID NO: 29, HVR-H2 comprising the amino acid sequence of SEQ ID NO: 39, HVR-H3 comprising the amino acid sequence of SEQ ID NO: 52, HVR-L1 comprising the amino acid sequence of SEQ ID NO: 65, HVR-L2 comprising the amino acid sequence of SEQ ID NO: 68, and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 77.

[0084] In some embodiments, the antibody comprises a) a heavy chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 82-94, and / or b) a light chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 95-107. In some embodiments, the antibody comprises a heavy chain variable region comprising an amino acid sequence having at least 90% (e.g., at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) sequence identity to a sequence selected from SEQ ID NOs: 82-94, and / or a light chain variable region comprising an amino acid sequence having at least 90% (e.g., at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) sequence identity to a sequence selected from SEQ ID NOs: 95-107. In some embodiments, the antibody comprises the heavy chain variable region and the light chain variable region of any of the exemplary antibodies set forth in Table B below. In some embodiments, the antibody comprises one, two, or all three HVRs of the heavy chain variable region, and / or one, two, or all three HVRs of the light chain variable region, as set forth for any of the exemplary antibodies set forth in Table B below. TIFF0007678841000004.tif238170TIFF0007678841000005.tif255170TIFF0007678841000006.tif250170

[0085] In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:82, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:95. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:83, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:96. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:84, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:97. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:85, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:98. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:86, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:99. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:87, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:100. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:88, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:101. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:89, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:102. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:90, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:103. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:91, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:104. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:92, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:105. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:93, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:106. In some embodiments, the antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:94, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:107.

[0086] In some embodiments, an antibody of the disclosure cross-competes for binding to human CTLA4 with an antibody comprising (a) an HVR-H1 comprising an amino acid sequence selected from SEQ ID NOs: 18-29, an HVR-H2 comprising an amino acid sequence selected from SEQ ID NOs: 30-39, and an HVR-H3 comprising an amino acid sequence selected from SEQ ID NOs: 40-52, and / or (b) an HVR-L1 comprising an amino acid sequence selected from SEQ ID NOs: 53-65, an HVR-L2 comprising an amino acid sequence selected from SEQ ID NOs: 66-69, and an HVR-L3 comprising an amino acid sequence selected from SEQ ID NOs: 70-81. In some embodiments, an antibody of the disclosure cross-competes for binding to human CTLA4 with an antibody comprising one, two, three, four, five, or all six of the HVRs set forth for any of the exemplary antibodies described in Table A. In some embodiments, an antibody of the disclosure cross-competes for binding to human CTLA4 with an antibody comprising a) a heavy chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 82-94, and / or b) a light chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 95-107. In some embodiments, an antibody of the disclosure cross-competes for binding to human CTLA4 with an antibody comprising a VH and / or VL as shown for any of the exemplary antibodies described in Table B.

[0087] The CTLA4 antibodies described herein can be of any class, such as IgG, IgM, IgE, IgA, or IgD. In some embodiments, the CTLA4 antibody is of the IgG class, such as IgG1, IgG2, IgG3, or IgG4 subclass. CTLA4 antibodies can be converted from one class or subclass to another using methods known in the art. An exemplary method for producing an antibody of a desired class or subclass is to isolate nucleic acid encoding a heavy chain of a CTLA4 antibody and nucleic acid encoding a light chain of a CTLA4 antibody, and convert the nucleic acid to a V-type antibody. H The coding sequence for the region was isolated and HThe method includes the steps of linking the sequence to a sequence encoding a heavy chain constant region of the desired class or subclass, expressing the light chain genes and heavy chain constructs in a cell, and harvesting the CTLA4 antibody. The antibodies of the present disclosure can be monoclonal or polyclonal. The antibodies of the present disclosure can be monospecific or multispecific (e.g., bispecific, trispecific, etc.) antibodies. In some embodiments, the CTLA4 antibodies described herein can include one or more Fc mutations (e.g., that modulate (increase or decrease) ADCC or CDC activity). Any suitable Fc mutation known in the art can be used in the CTLA4 antibodies of the present disclosure.

[0088] In some embodiments, the antibodies of the disclosure are bispecific antibodies that bind to a first and a second target, the first target being human CTLA4. In some embodiments, the bispecific antibodies bind to a first and a second target, the first target being human CTLA4, and the bispecific antibodies comprise (a) an HVR-H1 comprising an amino acid sequence selected from SEQ ID NOs: 18-29, an HVR-H2 comprising an amino acid sequence selected from SEQ ID NOs: 30-39, and an HVR-H3 comprising an amino acid sequence selected from SEQ ID NOs: 40-52, and / or (b) an HVR-L1 comprising an amino acid sequence selected from SEQ ID NOs: 53-65, an HVR-L2 comprising an amino acid sequence selected from SEQ ID NOs: 66-69, and an HVR-L3 comprising an amino acid sequence selected from SEQ ID NOs: 70-81. In some embodiments, the bispecific antibodies bind to a first and a second target, the first target being human CTLA4, and the bispecific antibodies comprise one, two, three, four, five, or all six of the HVRs set forth for any of the exemplary antibodies set forth in Table A. In some embodiments, the bispecific antibody binds to a first and a second target, the first target is human CTLA4, and the bispecific antibody comprises a) a heavy chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 82-94, and / or b) a light chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 95-107. In some embodiments, the bispecific antibody binds to a first and a second target, the first target is human CTLA4, and the bispecific antibody comprises a VH and / or VL as shown for any of the exemplary antibodies described in Table B. In some embodiments, the second target is PD-1, PD-L1, PD-L2, LAG3, TIM3, B7-H3, CD95, CD120a, OX40, CD40, BTLA, VISTA, ICOS, Her1, Her2, Her3, or B7-H4.

[0089] Antibodies of the disclosure may be produced by any technique known in the art, including conventional monoclonal antibody methodology, e.g., standard somatic cell hybridization techniques (see, e.g., Kohler and Milstein, Nature 256:495 (1975)), viral or oncogenic transformation of B lymphocytes, or recombinant antibody techniques described in detail herein (see, e.g., Examples 1 and 2). In some embodiments, antibodies of the disclosure are produced using any of the libraries and / or methods described in PCT Application No. PCT / CN2017 / 098333, which is incorporated herein by reference in its entirety, and / or PCT Application No. PCT / CN2017 / 098299, which is incorporated herein by reference in its entirety.

[0090] The production of hybridomas is a very well-established procedure. A common animal system for preparing hybridomas is the mouse system. Immunization protocols and techniques for isolating immunized splenocytes for fusion are known in the art. Fusion partners (e.g., mouse myeloma cells) and fusion procedures are also known. One well-known method that can be used to generate human CTLA4 antibodies provided by the present disclosure includes the use of the XenoMouse™ animal system. XenoMouse™ mice are an engineered mouse strain that contains large fragments of human immunoglobulin heavy and light chain loci and are deficient in mouse antibody production (see, e.g., Green et al., (1994) Nature Genetics 7:13-21, WO2003 / 040170). The animal is immunized with a CTLA4 antigen. The CTLA4 antigen is isolated and / or purified CTLA4. It can be a fragment of CTLA4, such as the extracellular domain of CTLA4. Immunization of animals can be performed by any method known in the art (see, for example, Harlow and Lane, Antibodies: A Laboratory Manual, New York: Cold Spring Harbor Press, 1990). Methods for immunizing non-human animals, such as mice, rats, sheep, goats, pigs, cattle and horses, are well known in the art (see, for example, Harlow and Lane, supra, and U.S. Pat. No. 5,994,619). CTLA4 antigen can be administered with an adjuvant to stimulate the immune response. Exemplary adjuvants include complete or incomplete Freund's adjuvant, RIBI (muramyl dipeptide), or ISCOM (immunostimulating complex). After immunization of an animal with CTLA4 antigen, an immortalized cell line producing antibodies is prepared from cells isolated from the immunized animal. After immunization, the animal is sacrificed and B cells in the lymph nodes and / or spleen are immortalized.Methods for immortalizing cells include, but are not limited to, introducing oncogenes into the cells, curing the cells with oncogenic viruses, culturing the cells under conditions that select for immortalized cells, subjecting the cells to oncogenic or mutating compounds, fusing the cells with immortalized cells, e.g., myeloma cells, and inactivating tumor suppressor genes (see, e.g., Harlow and Lane, supra). When fusion with myeloma cells is used, the myeloma cells preferably do not secrete immunoglobulin polypeptides (non-secretory cell lines). Immortalized cells are screened using CTLA4, a portion thereof, or cells expressing CTLA4. As discussed further below, CTLA4 antibody-producing cells, e.g., hybridomas, are selected, cloned, and further screened for desirable properties, including robust growth, high antibody production, and desirable antibody properties. Hybridomas can be grown in vivo in syngeneic animals, animals lacking an immune system, e.g., nude mice, or in vitro in cell culture. Methods for selecting, cloning, and growing hybridomas are well known to those skilled in the art.

[0091] The antibodies of the present disclosure can also be prepared using phage display or yeast display methods. Such display methods for isolating human antibodies are established in the art (see, for example, Knappik, et al. (2000) J. Mol. Biol. 296, 57-86; Feldhaus et al. (2003) Nat Biotechnol 21:163-170; also see the methods in Examples 1 and 2 below).

[0092] antigen binding fragment In some other aspects, the disclosure provides antigen-binding fragments of any of the CTLA4 antibodies described herein.

[0093] The antigen-binding fragment may comprise any sequence of any of the antibodies described herein. In some embodiments, the antigen-binding fragment comprises the amino acid sequence of (1) a light chain of a CTLA4 antibody, (2) a heavy chain of a CTLA4 antibody, (3) a variable region from the light chain of a CTLA4 antibody, (4) a variable region from the heavy chain of a CTLA4 antibody, (5) one or more HVRs (e.g., 1, 2, 3, 4, 5, or 6 HVRs) of a CTLA4 antibody, or (6) three HVRs from the light chain and three HVRs from the heavy chain of a CTLA4 antibody.

[0094] In some embodiments, the disclosure provides an antigen-binding fragment of an antibody selected from those listed in Tables A and B.

[0095] In some embodiments, the antigen-binding fragment of a CTLA4 antibody comprises: (i) V L , V H , C L , and C H (ii) a Fab fragment, which is a monovalent fragment consisting of one domain; (iii) a F(ab')2 fragment, which is a bivalent fragment containing two Fab fragments linked by a disulfide bridge at the hinge region; and (iv) a V H and C H (iv) a V of a single arm of an antibody; L and V H (v) an Fv fragment consisting of a V H (vi) isolated CDRs, and (vii) antibody V domains (Ward et al., (1989) Nature 341:544-546). H V of antibody linked to domain L and single chain antibodies (scFv), which are polypeptides comprising a region (see, e.g., Bird et al. (1988) Science 242:423-426; Huston et al. (1988) Proc. Natl. Acad. Sci. USA 85:5879-5883).

[0096] antibody derivative In some further aspects, the disclosure provides derivatives of any of the CTLA4 antibodies described herein.

[0097] In some embodiments, an antibody derivative is derived from the modification of the amino acid sequence of an exemplary antibody of the present disclosure (e.g., a "parent antibody"), preserving the overall molecular structure of the amino acid sequence of the parent antibody. The amino acid sequence of any region of the parent antibody chain can be modified, such as the framework region, HVR region, or constant region. The types of modifications include substitution, insertion, deletion, or combinations thereof of one or more amino acids of the parent antibody.

[0098] In some embodiments, the antibody derivative has a V sequence that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to an amino acid sequence set forth in any of SEQ ID NOs: 82-107. L or V HIn some embodiments, the antibody derivative comprises an HVR-H1 amino acid sequence region that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the amino acid sequence set forth in any of SEQ ID NOs: 18-29. In some embodiments, the antibody derivative comprises an HVR-H2 amino acid sequence region that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the amino acid sequence set forth in any of SEQ ID NOs: 30-39. In some embodiments, the antibody derivative comprises an HVR-H3 amino acid sequence region that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the amino acid sequence set forth in any of SEQ ID NOs: 40-52. In some embodiments, the antibody derivative comprises an HVR-L1 amino acid sequence region that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the amino acid sequence set forth in any of SEQ ID NOs: 53-65. In some embodiments, the antibody derivative comprises an HVR-L2 amino acid sequence region that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the amino acid sequence set forth in any of SEQ ID NOs:66-69.In some embodiments, the antibody derivative comprises an HVR-L3 amino acid sequence region that is at least 65%, at least 75%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the amino acid sequence set forth in any of SEQ ID NOs:70-81.

[0099] In some particular embodiments, the derivative comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 conservative or non-conservative substitutions, and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 additions and / or deletions to the amino acid sequence set forth in any of SEQ ID NOs: 18-107.

[0100] Amino acid substitution includes both conservative and non-conservative substitution. The term "conservative amino acid substitution" refers to the replacement of one amino acid with another amino acid when the two amino acids have similarities in certain physicochemical properties such as polarity, charge, solubility, hydrophobicity, hydrophilicity, and / or amphipathicity of the related residues. For example, typically, substitutions can be made within each of the following groups: (a) non-polar (hydrophobic) amino acids such as alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan, and methionine, (b) polar neutral amino acids such as glycine, serine, threonine, cysteine, tyrosine, asparagine, and glutamine, (c) positively charged (basic) amino acids such as arginine, lysine, and histidine, and (d) negatively charged (acidic) amino acids such as aspartic acid and glutamic acid.

[0101] Modifications may be made anywhere in the amino acid sequence of the antibody, including in the HVRs, framework regions, or constant regions. In one embodiment, the present disclosure provides a VVR of an exemplary antibody of the present disclosure. H and V LThe present invention provides antibody derivatives that contain the HVR sequences of the present disclosure, but contain framework sequences that differ from those of the exemplary antibodies. Such framework sequences can be obtained from public DNA databases or published references that contain germline antibody gene sequences. For example, germline DNA sequences of human heavy and light chain variable region genes can be found in the Genbank database or the "VBase" human germline sequence database (Kaba et al., Sequences of Proteins of Immunological Interest, Fifth Edition, USDepartment of Health and Human Services, NIH Publication No. 91-3242 (1991); Tomlinson et al., J. Mol. Biol. 227:776-798 (1992); and Cox et al., Eur. J. Immunol. 24:827-836 (1994)). Framework sequences that can be used in the construction of antibody derivatives include those that are structurally similar to the framework sequences used by the exemplary antibodies of the present disclosure. For example, the HVR-H1, HVR-H2, and HVR-H3 sequences, and the HVR-L1, HVR-L2, and HVR-L3 sequences of an exemplary antibody can be grafted into framework regions having sequences identical to those found in the germline immunoglobulin gene from which the framework sequences are derived, or the HVR sequences can be grafted into framework regions that contain one or more mutations compared to the germline sequences.

[0102] In some embodiments, the antibody derivative is a chimeric antibody comprising the amino acid sequence of an exemplary antibody of the present disclosure. In one example, one or more HVRs from one or more exemplary antibodies are combined with HVRs from an antibody from a non-human animal, such as a mouse or rat. In another example, all HVRs of the chimeric antibody are derived from one or more exemplary antibodies. In some specific embodiments, the chimeric antibody comprises one, two, or three HVRs from the heavy chain variable region and / or one, two, or three HVRs from the light chain variable region of an exemplary antibody. Chimeric antibodies can be generated using conventional methods known in the art.

[0103] Another type of modification is the V H and / or V L The preferred method is to mutate amino acid residues in the HVR regions of the heavy chain. Site-directed mutagenesis or PCR-mediated mutagenesis can be used to introduce the mutation(s) and the effect on antibody binding or other functional properties of interest can be evaluated in in vitro or in vivo assays known in the art. Typically, conservative substitutions are introduced. The mutations can be amino acid additions and / or deletions. Furthermore, typically no more than 1, 2, 3, 4, or 5 residues in the HVR regions are altered. In some embodiments, the antibody derivative comprises 1, 2, 3, or 4 amino acid substitutions in the heavy chain HVR and / or light chain HVR. In another embodiment, the amino acid substitution is to change one or more cysteines in the antibody to another residue, such as, but not limited to, alanine or serine. The cysteines can be standard or non-standard cysteines. In one embodiment, the antibody derivative has 1, 2, 3, or 4 conservative amino acid substitutions in the heavy chain HVR regions compared to the amino acid sequence of the exemplary antibody.

[0104] Also, V H and / or V LModifications can also be made to framework residues within the region. Typically, such framework variants are made to reduce the immunogenicity of antibodies. One approach is to "back-mutate" one or more framework residues to the corresponding germline sequence. An antibody that has undergone somatic mutations may contain framework residues that differ from the germline sequence from which the antibody is derived. Such residues can be identified by comparing the antibody framework sequence with the germline sequence from which the antibody is derived. To return the framework region sequences to their germline configuration, the somatic mutations can be "back-mutated" to the germline sequence, for example, by site-directed mutagenesis or PCR-mediated mutagenesis.

[0105] In addition, modifications can also be made within the Fc region of an exemplary antibody, typically altering one or more functional properties of the antibody, such as serum half-life, complement binding, Fc receptor binding, and / or antigen-dependent cellular cytotoxicity. In one example, the hinge region of CH1 is modified to change, e.g., increase or decrease, the number of cysteine ​​residues in the hinge region. This approach is further described in U.S. Pat. No. 5,677,425. The number of cysteine ​​residues in the hinge region of CH1 is altered, for example, to facilitate assembly of the light and heavy chains or to increase or decrease the stability of the antibody. In another case, the Fc hinge region of an antibody is mutated to decrease the biological half-life of the antibody.

[0106] Additionally, the antibodies of the present disclosure may be modified to alter their potential glycosylation sites or patterns, according to routine experimentation known in the art. In another aspect, the present disclosure provides derivatives of CTLA4 antibodies containing at least one mutation in the variable region of the light or heavy chain that alters the pattern of glycosylation in the variable region. Such antibody derivatives may have increased affinity and / or altered specificity for binding antigen. The mutations may add new glycosylation sites to the V region, change the location of one or more V region glycosylation site(s), or remove existing V region glycosylation sites. In one embodiment, the present disclosure provides derivatives of CTLA4 antibodies with a potential N-linked glycosylation site at an asparagine in the heavy chain variable region, whereby a potential N-linked glycosylation site in one heavy chain variable region is removed. In another embodiment, the present disclosure provides derivatives of CTLA4 antibodies with a potential N-linked glycosylation site at an asparagine in the heavy chain variable region, whereby a potential N-linked glycosylation site in both heavy chain variable regions is removed. Methods for altering the glycosylation pattern of antibodies are known in the art, such as those described in US Pat. No. 6,933,368, the disclosure of which is incorporated herein by reference.

[0107] In another aspect, the disclosure provides an antibody derivative comprising a CTLA4 antibody or antigen-binding fragment thereof described herein linked to an additional molecular entity, examples of which include pharmaceutical agents, peptides or proteins, detection agents or labels, and antibodies.

[0108] In some embodiments, the antibody derivative comprises an antibody of the present disclosure linked to a pharmaceutical agent. Examples of pharmaceutical agents include cytotoxic agents or other cancer therapeutic agents, and radioisotopes. Specific examples of cytotoxic agents include taxol, cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, tenoposide, vincristine, vinblastine, corticine, doxorubicin, daunorubicin, dihydroxyanthracin dione, mitoxantrone, mithramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine, propranolol, puromycin, and analogs or homologs thereof. Therapeutic agents also include, for example, antimetabolites (e.g., methotrexate, 6-mercaptopurine, 6-thioguanine, cytarabine, 5-fluorouracil decarbazine), alkylating agents (e.g., mechlorethamine, thiotepa chlorambucil, melphalan, carmustine (BSNU) and lomustine (CCNU), cyclosporine, busulfan, dibromomannitol, streptozotocin, mitomycin C, and cis-dichlorodiamine platinum (II) (DDP) cisplatin), anthracyclines (e.g., daunorubicin (formerly daunomycin) and doxorubicin), antibiotics (e.g., dactinomycin (formerly actinomycin), bleomycin, mithramycin, and anthramycin (AMC)), and antimitotic agents (e.g., vincristine and vinblastine). Examples of radioisotopes that can be conjugated to antibodies for diagnostic or therapeutic use include iodine. 131 ,indium 111 ,yttrium 90 , and lutetium 177Methods of linking antibodies to pharmaceutical agents are known in the art, including, but not limited to, using a variety of linker technologies. Exemplary linker types include hydrazones, thioethers, esters, disulfides, and peptide-containing linkers. For further discussion of linkers and methods for linking therapeutic agents to antibodies, see, e.g., Saito et al., Adv. Drug Deliv. Rev. 55:199-215 (2003); Trail, et al., Cancer Immunol. Immunother. 52:328-337 (2003); Payne, Cancer Cell 3:207-212 (2003); Allen, Nat. Rev. Cancer 2:750-763 (2002); Pastan and Kreitman, Curr. Opin. Investig. Drugs 3:1089-1091 (2002); Senter and Springer (2001) Adv. Drug Deliv. Rev. 53:247-264.

[0109] In some embodiments, the antibody derivative is a CTLA4 antibody multimer, which is a multimeric form of CTLA4 antibody, such as an antibody dimer, trimer, or higher order oligomer of monomeric antibodies. The individual monomers in the antibody multimer may be identical or different. Furthermore, the individual antibodies in the multimer may have the same or different binding specificities. Antibody multimerization may be achieved by natural aggregation of antibodies. For example, a certain percentage of purified antibody preparations (e.g., purified IgG4 molecules) spontaneously form protein aggregates containing antibody homodimers and other higher order antibody multimers. Alternatively, antibody homodimers may be formed by chemical conjugation techniques known in the art, such as by using cross-linking agents. Suitable cross-linkers include those that are heterobifunctional, having two distinct reactive groups separated by an appropriate spacer (e.g., m-maleimidobenzoyl-N-hydroxysuccinimide ester, succinimidyl 4-(maleimidomethyl)cyclohexane-1-carboxylate, and N-succinimidyl S-acetylthio-acetate), or those that are homobifunctional (e.g., disuccinimidyl suberate). Such linkers are commercially available, for example, from Pierce Chemical Company, Rockford, IL. Antibodies can also be made to multimerize through recombinant DNA techniques known in the art.

[0110] Other examples of antibody derivatives provided by the present disclosure include single chain antibodies, diabodies, domain antibodies, nanobodies, and unibodies. A "single chain antibody" (scFv) is a V H V linked to domain L It consists of a single polypeptide chain containing the V L Domain and V HThe domains pair to form a monovalent molecule. Single-chain antibodies can be prepared according to methods known in the art (see, for example, Bird et al., (1988) Science 242:423-426, and Huston et al., (1988) Proc. Natl. Acad. Sci. USA 85:5879-5883). "Diabodies" are composed of two chains, each of which comprises a heavy chain variable region connected to a light chain variable region on the same polypeptide chain, connected by a short peptide linker, and the two regions on the same chain do not pair with each other, but have complementary domains on the other chain, forming a bispecific molecule. Methods for preparing diabodies are known in the art (see, for example, Holliger P. et al., (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448, and Poljak RJ et al., (1994) Structure 2:1121-1123). Domain antibodies (dAbs) are small functional binding units of antibodies, corresponding to the variable regions of either the heavy or light antibody chains. Domain antibodies are well expressed in bacteria, yeast, and mammalian cell systems. Further details of domain antibodies and methods for their production are known in the art (see, for example, U.S. Pat. Nos. 6,291,158, 6,582,915, 6,593,081, 6,172,197, 6,696,245, European Patent Nos. 0368684 and 0616640, WO05 / 035572, WO04 / 101790, WO04 / 081026, WO04 / 058821, WO04 / 003019, and WO03 / 002609). Nanobodies are derived from the heavy chain of an antibody. Nanobodies typically contain a single variable domain and two constant domains (CH2 and CH3) and retain the antigen-binding ability of the original antibody. Nanobodies can be prepared by methods known in the art (see, for example, U.S. Patent No. 6,765,087, U.S. Patent No. 6,838,254, WO06 / 079372). Unibodies consist of one light chain and one heavy chain of an IgG4 antibody. Unibodies can be made by removing the hinge region of an IgG4 antibody.Further details of unibodies and methods for preparing them can be found in WO2007 / 059782.

[0111] IV. Activatable Binding Polypeptides Targeting CTLA4 The present disclosure also relates, in part, to precision / context-dependent activatable binding polypeptides (i.e., activatable antibodies) that bind to human CTLA4, including activatable antibodies (e.g., anti-CTLA4 antibodies, anti-CTLA4 antibody binding fragments, and / or anti-CTLA4 antibody derivatives) comprising any of the anti-CTLA4 antibodies described herein, antigen-binding fragments of activatable anti-CTLA4 antibodies, and / or derivatives of activatable anti-CTLA4 antibodies. In some embodiments, the activatable anti-CTLA4 antibodies described herein may have an improved safety profile. For example, the anti-CTLA4 antibodies described herein may have a better safety margin as assessed by spleen weight change. The change in spleen size with increasing doses of the drug administered is used as a benchmark to evaluate the safety margin of the candidate drug used. As shown in Figures 48A-B, the activatable anti-CTLA4 antibodies described herein have a better safety margin compared to the parent antibody (the antibody without the masking moiety).

[0112] In some embodiments, an activatable antibody of the disclosure comprises (a) a masking moiety (MM), (b) a cleavable moiety (CM), and (c) a target binding moiety (TBM). In some embodiments, the MM is any of the masking moieties described herein. In some embodiments, the CM is any of the cleavable moieties described herein. In some embodiments, the TBM is any of the target binding moieties described herein (e.g., a target binding moiety (TBM) comprising an antibody light chain variable region and / or an antibody heavy chain variable region, e.g., the VH and / or VL of any of the anti-CTLA4 antibodies described herein). In some embodiments, the MM prevents and / or inhibits binding of the activatable antibody to its target (e.g., human CTLA4 or human CD137) when the CM is not cleaved. In some embodiments, the activatable antibody can bind to its target (e.g., human CTLA4 or human CD137) when the CM is cleaved.

[0113] In some embodiments, an activatable antibody comprises: (a) a polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein MM is any of the masking moieties described herein, CM is any of the cleavable moieties described herein, and TBM comprises an antibody light chain variable region (VL); and (b) an antibody heavy chain variable region (VH).

[0114] In some embodiments, an activatable antibody comprises: (a) a polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein MM is any of the masking moieties described herein, CM is any of the cleavable moieties described herein, and TBM comprises an antibody heavy chain variable region (VH); and (b) an antibody light chain variable region (VL).

[0115] In some embodiments, an activatable antibody comprises a polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), wherein the MM is any of the masking moieties described herein, the CM is any of the cleavable moieties described herein, and the TBM comprises an antibody heavy chain variable region (VH) and an antibody light chain variable region (VL).

[0116] The term "activatable binding polypeptide," "ABP," or "activatable antibody" includes a polypeptide that includes a target binding portion (TBM), a cleavable portion (CM), and a masking portion (MM). In some embodiments, the TBM includes an amino acid sequence that binds to a target. In some embodiments, the TBM includes an antigen binding domain (ABD) of an antibody or antibody fragment thereof (e.g., any of the antibodies or antigen binding fragments described herein). In some embodiments, the antigen binding domain includes a heavy chain variable region that includes one, two, or three of the heavy chain variable region HVRs described herein, and a light chain variable region that includes one, two, or three of the light chain variable region HVRs described herein (e.g., one, two, or three of the heavy chain variable region HVR sequences and / or one, two, or three of the light chain variable region HVR sequences as shown in Table A, including all six HVRs of any of the exemplary antibodies as shown in Table A). In some embodiments, the antigen binding domain comprises a heavy chain variable region comprising any of the heavy chain variable region sequences described herein, and a light chain variable region comprising any of the light chain variable region sequences described herein (e.g., a heavy chain variable region sequence and / or a light chain variable region sequence as shown in Table B). In some embodiments, the TBM (e.g., comprising an ABD) comprises an antibody light chain variable region (VL) and an antibody heavy chain variable region (VH), where the VH and VL form a binding domain that binds to a target in the absence of MM. In some embodiments, the VH and VL are covalently linked, for example in an scFv. In some embodiments, the VH and VL are not covalently linked. In some embodiments, the VH and VL form a Fab fragment. In some embodiments, the VH is linked to an antibody heavy chain constant region, and the VL is linked to an antibody light chain constant region.

[0117] In some embodiments, the activatable antibody comprises a polypeptide comprising, from the N-terminus to the C-terminus, the structure masking moiety (MM)-cleavable moiety (CM)-VL, and the activatable antibody further comprises a second polypeptide comprising a VH (e.g., a Fab fragment). In some embodiments, the activatable antibody comprises a polypeptide comprising, from the N-terminus to the C-terminus, the structure masking moiety (MM)-cleavable moiety (CM)-VL-VH (e.g., an scFv). In some embodiments, the activatable antibody comprises a polypeptide comprising, from the N-terminus to the C-terminus, the structure masking moiety (MM)-cleavable moiety (CM)-VH, and the activatable antibody further comprises a second polypeptide comprising a VL (e.g., a Fab fragment). In some embodiments, the activatable antibody comprises a polypeptide comprising, from the N-terminus to the C-terminus, the structure masking moiety (MM)-cleavable moiety (CM)-VH-VL (e.g., an scFv).

[0118] A CM generally comprises an amino acid sequence that is cleavable, e.g., that serves as a substrate for an enzyme, and / or a cysteine-cysteine ​​pair that can form a reducible disulfide bond. Thus, when the terms "cleavage," "cleavable," "cleaved," and the like are used in connection with a CM, the terms encompass disruption of the disulfide bond between the cysteine-cysteine ​​pair by, e.g., enzymatic cleavage by a protease, as well as reduction of the disulfide bond, which may result from exposure to a reducing agent.

[0119] MM refers to the amino acid sequence when the CM of an activatable antibody is intact (e.g., not cleaved by the corresponding enzyme and / or contains an unreduced cysteine-cysteine ​​disulfide bond), and the MM interferes with or inhibits the binding of the TBM to its target. In some embodiments, the MM interferes with or inhibits the binding of the TBM to its target so efficiently that binding of the TBM to its target is extremely low and / or below the limit of detection (e.g., binding cannot be detected by ELISA or flow cytometry assays). The amino acid sequence of the CM may overlap with or be contained within the MM. For convenience, it should be noted that "ABP" or "activatable antibody" is used herein to refer to the ABP or activatable antibody in both their uncleaved (or "native") state, as well as their cleaved state. It will be apparent to one of skill in the art that in some embodiments, the cleaved ABP may lack the MM, e.g., due to cleavage of the CM by a protease, resulting in release of at least the MM (e.g., if the MM is not bound to the ABP by a covalent bond (e.g., a disulfide bond between cysteine ​​residues). Exemplary ABPs are described in further detail below.

[0120] In some embodiments, the masking moiety (MM) interferes with, occludes, reduces the ability of, prevents, inhibits, or competes with the target binding moiety for binding to its target (e.g., an inactive activatable antibody). In some embodiments, the masking moiety (MM) interferes with, occludes, reduces, prevents, inhibits, or competes with the target binding moiety for binding to its target only if the polypeptide has not been activated (e.g., activated by a change in pH (increasing or decreasing), activated by a change in temperature (increasing or decreasing), activated after contact with a second molecule (such as a small molecule or protein ligand), etc.). In some embodiments, activation induces cleavage of the polypeptide within the cleavage moiety. In some embodiments, activation induces a conformational change in the polypeptide (e.g., dislocation of the masking moiety (MM)) such that the masking moiety no longer interferes with binding of the activatable antibody to its target. In some embodiments, the masking moiety (MM) interferes with, occludes, reduces the ability of, prevents, inhibits, or competes with the target binding moiety for binding to its target only if the cleavable moiety (CM) is not cleaved by one or more proteases that cleave within the cleavable moiety (CM). In some embodiments, the masking moiety (MM) has a masking efficiency of at least about 2.0 (e.g., at least about 2.0, at least about 3.0, at least about 4.0, at least about 5.0, at least about 6.0, at least about 7.0, at least about 8.0, at least about 9.0, at least about 10, at least about 25, at least about 50, at least about 75, at least about 100, at least about 150, at least about 200, at least about 300, at least about 400, at least about 500, etc.) prior to activation.In some embodiments, masking efficiency is measured by the difference in affinity of an activatable antibody comprising a masking moiety (before activation) for binding to its target compared to the affinity of a polypeptide lacking the masking moiety (MM) for binding to its target (e.g., the difference in affinity of an activatable antibody comprising a masking moiety (MM) (before activation) for a target antigen (such as CTLA4) compared to a parent antibody lacking the masking moiety (MM), or the difference in affinity of an activatable antibody comprising a masking moiety (MM) (before activation) for a target antigen (such as CTLA4) compared to the affinity of the activatable antibody after activation). In some embodiments, masking efficiency is the EC of binding of an activatable antibody comprising a masking moiety (MM) (before activation). 50 , EC of the parent antibody 50 (e.g., EC by ELISA) 50 (see, e.g., methods in Example 8). In some embodiments, masking efficiency is measured by the difference in affinity of an activatable antibody comprising a masking moiety (MM) for binding to its target before activation compared to the affinity of an activatable antibody comprising a masking moiety (MM) for binding to its target after activation (e.g., the difference in affinity of an activatable antibody for a target antigen (such as CTLA4) before activation compared to the affinity of an activatable antibody comprising a masking moiety (MM) for binding to its target after activation). In some embodiments, the masking moiety (MM) binds to the target binding moiety (TBM) and prevents the activatable antibody from binding to its target (e.g., an "inactive" activatable antibody). In some embodiments, the masking moiety (MM) has a dissociation constant for binding to the target binding moiety (TBM) that is greater than the dissociation constant of the target binding moiety (TBM) for its target.

[0121] In some embodiments, the masking moiety (MM) does not interfere with, occlude, reduce the ability of, prevent, inhibit, or compete with the target binding moiety (TBM) for binding to its target after the activatable antibody is activated (e.g., activated by treatment with one or more proteases that cleave within the cleavable moiety (CM), activated by a change in pH (increased or decreased), activated by a change in temperature (increased or decreased), activated after contact with a second molecule (such as an enzyme or protein ligand), etc.). In some embodiments, the masking moiety (MM) does not interfere with, occlude, reduce the ability of, prevent, inhibit, or compete with the target binding moiety (TBM) for binding to its target after the cleavable moiety (CM) is cleaved by one or more proteases that cleave within the cleavable moiety (CM). In some embodiments, the masking moiety (MM) has a masking efficiency after activation (e.g., the relative affinity of the activatable antibody after activation compared to the affinity of the parent antibody) of at most about 1.75 (e.g., at most about 1.75, at most about 1.5, at most about 1.4, at most about 1.3, at most about 1.2, at most about 1.1, at most about 1.0, at most about 0.9, at most about 0.8, at most about 0.7, at most about 0.6, or at most about 0.5, etc.).

[0122] In some embodiments, the activatable antibodies of the present disclosure comprise a pair of cysteine ​​residues at fixed positions to ensure that the activatable antibody has a constrained conformation and / or comprise a masking moiety (MM) that possesses few or no chemically labile residues (such as methionine or tryptophan). Advantageously, the inclusion of a pair of cysteine ​​residues at fixed positions ensures that the activatable antibody has a constrained conformation and tends to exhibit increased binding affinity and / or specificity. Additionally, the activatable antibodies of the present disclosure comprised a masking moiety that possesses few or no residues that are unfavorable to manufacturing processes, such as methionine or tryptophan.

[0123] In some embodiments, the activatable antibodies of the present disclosure are context-dependent (e.g., are activated (only able to bind to their target) in certain contexts (such as a protease-rich tumor microenvironment). In some embodiments, the activatable antibodies of the present disclosure offer improved safety over more traditional non-activatable antibodies (e.g., exhibit reduced toxicity, do not induce significant changes in the weight of many organs, do not alter liver histopathology, hematology, and / or blood biochemistry, etc.). In some embodiments, the activatable antibodies of the present disclosure have improved pharmacokinetic properties (e.g., longer in vivo half-life) compared to more traditional non-activatable antibodies.

[0124] Anti-CTLA4 activatable antibody activity In some embodiments, the disclosure relates to activatable antibodies that bind to human CTLA4 when in an activated form (e.g., the activatable antibody is active after cleavage with a cleavable moiety (e.g., with one or more proteases) but is inactive prior to cleavage with the cleavable moiety (e.g., with one or more proteases)). In some embodiments, the activatable antibody, when in an activated form, exhibits the following functional properties: (a) a K for human, cynomolgus monkey, mouse, rat, and / or dog CTLA4 of 500 nM or less, e.g., about 10 nM or less. D(b) has antagonist activity against human CTLA4; (c) does not bind to human PD-1, PD-L1, PD-L2, LAG3, TIM3, B7-H3, CD95, CD120a, OX40, CD40, BTLA, VISTA, ICOS, and / or B7-H4 at concentrations up to 100 nM; (d) is cross-reactive with monkey, mouse, rat, and / or dog CTLA4; (e) induces an ADCC effect (e.g., against Tregs); (f) inhibits the expression of human PB (g) activate MCs (e.g., stimulate secretion of IL-2 and / or IFNγ), (h) have a therapeutic effect against cancer, and (i) inhibit binding of human CTLA4 to human CD80 and / or human CD86 (e.g., at least one, at least two, at least three, at least four, at least five, at least six, at least seven, at least eight, or all nine of these). Also provided herein is one or more activatable antibodies that compete or cross-compete with one or more of the CTLA4-targeted activatable antibodies and / or anti-CTLA4 antibodies described herein for binding to human CTLA4.

[0125] In some embodiments, the activatable antibody, when in an inactive form, has a K of about 500 nM or greater for human, cynomolgus monkey, mouse, rat, and / or dog CTLA4. D In some embodiments, the activatable antibody, when in its activated form, binds to human, cynomolgus monkey, mouse, rat, and / or dog CTLA4 with a K of about 500 nM or less (e.g., about 500 nM or less, about 450 nM or less, about 400 nM or less, about 350 nM or less, about 300 nM or less, about 250 nM or less, about 200 nM or less, about 150 nM or less, about 100 nM or less, about 90 nM or less, about 80 nM or less, about 70 nM or less, about 60 nM or less, about 50 nM or less, about 40 nM or less, about 30 nM or less, about 25 nM or less, about 20 nM or less, about 10 nM or less, about 1 nM or less, about 0.1 nM or less, etc.). D In some embodiments, the activatable antibody, when in its activated form, binds to human, cynomolgus monkey, mouse, rat, and / or dog CTLA4 with a K of about 350 nM or less.D In some embodiments, the activatable antibody, when in its active form, binds to human CTLA4 with a K of about 100 nM or less. D In some embodiments, the activatable antibody, when in its active form, binds to human CTLA4 with a K of about 50 nM or less. D In some embodiments, the activatable antibody, when in its active form, binds to human CTLA4 with a K of about 10 nM or less. D The K of the activatable antibody D Methods for measuring K can be performed using any method known in the art, including, for example, by surface plasmon resonance, ELISA, isothermal titration calorimetry, filter binding assays, EMSA, etc. In some embodiments, K D is measured by ELISA (see, for example, the Examples below).

[0126] In some embodiments, an activatable antibody, when in an inactive form, has no antagonist activity against human CTLA4. In some embodiments, an activatable antibody, when in an active form, has antagonist activity against human CTLA4 (e.g., induces an ADCC effect (e.g., against Tregs), activates PBMCs (e.g., by activating, inducing, and / or stimulating IL-2 and / or IFNγ secretion), blocks binding of human CTLA4 to human CD80 and / or human CD86, etc.). In some embodiments, an activatable antibody, when in an active form, inhibits one or more activities of human CTLA4 (e.g., inhibits one or more activities of human CTLA4 when a cell (e.g., a human cell) expressing human CTLA4 is contacted by the activatable antibody).

[0127] In some embodiments, the activatable antibody, when in an inactive form, is not cross-reactive with monkey (e.g., cynomolgus), mouse, rat, and / or dog CTLA4. In some embodiments, the activatable antibody, when in an activated form, is cross-reactive with monkey (e.g., cynomolgus), mouse, rat, and / or dog CTLA4. In some embodiments, the activatable antibody, when in an activated form, is cross-reactive with monkey CTLA4. In some embodiments, the activatable antibody, when in an activated form, is cross-reactive with mouse CTLA4. In some embodiments, the activatable antibody, when in an activated form, is cross-reactive with rat CTLA4. In some embodiments, the activatable antibody, when in an activated form, is cross-reactive with dog CTLA4. In some embodiments, the activatable antibody, when in an activated form, is cross-reactive with monkey and mouse CTLA4; monkey and rat CTLA4; monkey and dog CTLA4; mouse and rat CTLA4; mouse and dog CTLA4; rat and dog CTLA4; monkey, mouse, and rat CTLA4; monkey, rat, and dog CTLA4; mouse, rat, and dog CTLA4; or monkey, mouse, rat, and dog CTLA4. In some embodiments, the activatable binding polypeptide, when in an activated form, is cross-reactive at about 350 nM (e.g., about 1 nM, about 10 nM, about 25 nM, about 50 nM, about 75 nM, about 100 nM, about 150 nM, about 200 nM, about 250 nM, about 300 nM, about 350 nM). Methods for measuring cross-reactivity are known in the art and include, but are not limited to, surface plasmon resonance, ELISA, isothermal titration calorimetry, filter binding assays, EMSA, and the like.

[0128] In some embodiments, the activatable antibody, when in an inactive form, does not induce an ADCC effect (e.g., against CTLA4-expressing human cells, such as Tregs). In some embodiments, the activatable antibody, when in an inactive form, reduces the ADCC effect (e.g., against CTLA4-expressing human cells, such as Tregs) compared to a control binding polypeptide (e.g., parent antibody). In some embodiments, the activatable antibody, when in an active form, induces an ADCC effect (e.g., against CTLA4 expression, such as Tregs). Methods (e.g., in vitro methods) for measuring the ADCC effect are known in the art, including, but not limited to, by the methods described in the Examples below. In some embodiments, the activatable antibody, when in an inactive form, induces less than about 10% of the ADCC effect (e.g., less than about 10%, less than about 5%, less than about 1%, etc.) compared to a control (e.g., parent antibody). In some embodiments, the activatable antibody, when in activated form, induces an ADCC effect of greater than about 10% compared to a control (e.g., an isotype control) (e.g., induces an ADCC effect of greater than about 10%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, greater than about 40%, etc.).

[0129] In some embodiments, the activatable antibody is capable of inhibiting tumor cell growth and / or proliferation. In some embodiments, tumor cell growth and / or proliferation is inhibited by at least about 5% (e.g., at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 99%) when contacted with the activatable antibody compared to corresponding tumor cells not contacted with the activatable antibody (or compared to corresponding tumor cells contacted with an isotype control antibody). In some embodiments, the activatable antibody is capable of reducing tumor volume in a subject when the activatable antibody is administered to the subject. In some embodiments, an activatable antibody can reduce tumor volume in a subject by at least about 5% (e.g., at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 99%) compared to the initial tumor volume in the subject (e.g., compared to a corresponding tumor in a subject administered an isotype control antibody prior to administration of the activatable antibody). Methods for monitoring tumor cell growth / proliferation, tumor volume, and / or tumor inhibition are known in the art, including, for example, by the methods described in the Examples below.

[0130] In some embodiments, the activatable antibody has a therapeutic effect against cancer. In some embodiments, the activatable antibody alleviates one or more signs or symptoms of cancer. In some embodiments, a subject suffering from cancer goes into partial or complete remission when administered the activatable antibody.

[0131] In some embodiments, the disclosure provides isolated activatable antibodies that, when in their activated form, compete or cross-compete for binding to human CTLA4 with an antibody comprising a) an HVR-H1 comprising the amino acid sequence of SEQ ID NO:23, an HVR-H2 comprising the amino acid sequence of SEQ ID NO:35, an HVR-H3 comprising the amino acid sequence of SEQ ID NO:45, and / or b) an HVR-L1 comprising the amino acid sequence of SEQ ID NO:58, an HVR-L2 comprising the amino acid sequence of SEQ ID NO:66, and an HVR-L3 comprising the amino acid sequence of SEQ ID NO:75. In some embodiments, the disclosure provides isolated activatable antibodies that, when in their activated form, compete or cross-compete for binding to human CTLA4 with an antibody comprising a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:87, and / or b) a light chain variable region comprising the amino acid sequence of SEQ ID NO:100. The ability of an activatable antibody to compete or cross-compete for binding with an antibody can be determined using standard binding assays known in the art, such as BIAcore analysis, ELISA assays, or flow cytometry. For example, an antibody (e.g., as described above) can be allowed to bind to human CTLA4 under saturating conditions, and then the ability of the test activatable antibody (when in an activated form) to bind to CTLA4 can be measured. If the test activatable antibody can bind to CTLA4 at the same time as the antibody, the test activatable antibody will bind to a different epitope than the antibody. However, if the test activatable antibody cannot bind to CTLA4 at the same time, the test activatable antibody will bind to the same epitope, an overlapping epitope, or an epitope that is very close to the epitope bound by the antibody. This experiment can be performed using a variety of methods, such as ELISA, RIA, FACS, or surface plasmon resonance.

[0132] In some embodiments, the activatable antibody (when inactive) does not inhibit binding between CTLA4 and one or more of its binding partners (e.g., human CTLA4 and human CD80, human CTLA4 and human CD86). In some embodiments, the activatable antibody (when active) inhibits binding between CTLA4 and one or more of its binding partners (e.g., human CTLA4 and human CD80, human CTLA4 and human CD86). In some embodiments, the activatable antibody inhibits binding between CTLA4 and its ligand in vitro. In some embodiments, the activatable antibody has a half maximal inhibitory concentration (IC) of about 500 nM or less (e.g., about 500 nM or less, about 400 nM or less, about 300 nM or less, about 200 nM or less, about 100 nM or less, about 50 nM or less, about 25 nM or less, about 10 nM or less, about 1 nM or less, etc.) for inhibiting binding of CTLA4 to CD80 and / or CD86. 50 In some embodiments, the activatable antibody has a half maximal inhibitory concentration (IC) of about 100 nM or less for inhibiting the binding of CTLA4 to CD80 and / or CD86. 50 ). In some embodiments, the activatable antibody completely inhibits binding of human CTLA4 to CD80 and / or CD86 when provided at a concentration of about 100 nM or more (e.g., about 100 nM or more, about 500 nM or more, about 1 μM or more, about 10 μM or more, etc.). As used herein, the term "complete inhibition" or "completely inhibits" refers to the ability of an activatable antibody to reduce binding between a first protein and a second protein by at least about 80% (e.g., at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99%, etc.). Methods for measuring the ability of a polypeptide to inhibit binding of a first protein (e.g., human CTLA4) and a second protein (e.g., human CD80 or human CD86) are known in the art and include, but are not limited to, by BIAcore analysis, ELISA assays, and flow cytometry.

[0133] Masking part (MM) In some embodiments, the present disclosure relates to an activatable antibody comprising a masking moiety (MM). In some embodiments, the masking moiety (MM) is represented by formula (XVIII): m CX n CZ o (SEQ ID NO: 134), wherein m is 2-10, n is 3-10, and o is 1-10; each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y; and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P. In some embodiments, X is not W, M, and / or C. In some embodiments, X in formula (XVIII) is m Each X in is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P, and / or X in formula (XVIII) n wherein each X is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P. In some embodiments, MM has the formula (XX):(NNK) m TGY(NNK) n TGY(NHC) o (SEQ ID NO:136), wherein each N is independently A, G, T, or C; each K is independently T or G; each Y is independently T or C; and each H is independently A, T, or C.

[0134] In some embodiments, the masking moiety (MM) has the formula (XIX): m CZ n CZ o (SEQ ID NO:135), wherein m is 2 to 10, n is 3 to 10, o is 1 to 10, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0135] In some embodiments, m is 2-10, 2-9, 2-8, 2-7, 2-6, 2-5, 2-4, 2-3, 3-10, 3-9, 3-8, 3-7, 3-6, 3-5, 3-4, 4-10, 4-9, 4-8, 4-7, 4-6, 4-5, 5-10, 5-9, 5-8, 5-7, 5-6, 6-10, 6-9, 6-8, 6-7, 7-10, 7-9, 7-8, 8-10, 8-9, or 9-10. In some embodiments, m is 6-8. In some embodiments, m is 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, m is 6.

[0136] In some embodiments, n is 3-10, 3-9, 3-8, 3-7, 3-6, 3-5, 3-4, 4-10, 4-9, 4-8, 4-7, 4-6, 4-5, 5-10, 5-9, 5-8, 5-7, 5-6, 6-10, 6-9, 6-8, 6-7, 7-10, 7-9, 7-8, 8-10, 8-9, or 9-10. In some embodiments, n is 6-8. In some embodiments, n is 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, n is 6. In some embodiments, n is 8.

[0137] In some embodiments, o is 1-10, 1-9, 1-8, 1-7, 1-6, 1-5, 1-4, 1-3, 1-2, 2-10, 2-9, 2-8, 2-7, 2-6, 2-5, 2-4, 2-3, 3-10, 3-9, 3-8, 3-7, 3-6, 3-5, 3-4, 4-10, 4-9, 4-8, 4-7, 4-6, 4-5, 5-10, 5-9, 5-8, 5-7, 5-6, 6-10, 6-9, 6-8, 6-7, 7-10, 7-9, 7-8, 8-10, 8-9, or 9-10. In some embodiments, o is 1-2. In some embodiments, o is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, o is 2.

[0138] In some embodiments, the masking moiety (MM) comprises an amino acid sequence according to formula (XXI): Z6CX6CZ2 (SEQ ID NO: 137), where each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0139] In some embodiments, the masking moiety (MM) comprises an amino acid sequence according to formula (XXII): Z6CX8CZ2 (SEQ ID NO: 138), where each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0140] In some embodiments, the first peptide (FP) comprises an amino acid sequence according to formula (XXIII):(Z6)C(Z6)C(Z2) (SEQ ID NO: 139), wherein each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0141] In some embodiments, the masking moiety (MM) comprises an amino acid sequence according to formula (XXIV):(Z6)C(Z8)C(Z2) (SEQ ID NO: 140), where each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P. In some embodiments, the activatable antibody comprises X m CPDHPYPCXX (SEQ ID NO: 181), X m CDAFYPYCXX (SEQ ID NO: 182), X m CDSHYPYCXX (SEQ ID NO: 183), and X mCVPYYYACXX (SEQ ID NO: 184), wherein m is 2 to 10 and each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y. In some embodiments, the activatable antibody comprises a masking moiety (MM) comprising the sequence EVGSYNFVADSCPDHPYPCSA (SEQ ID NO: 189), EVGSYIVHHSDCDAFYPYCDS (SEQ ID NO: 190), EVGSYYSAYPACDSHYPYCNS (SEQ ID NO: 191), EVGSYPNPSSDCVPYYYACAY (SEQ ID NO: 192), EVGSYYSAYPACDSHYPYCQS (SEQ ID NO: 193), EVGSYPQPSSDCVPYYYACAY (SEQ ID NO: 195), or EVGSYPNPASDCVPYYYACAY (SEQ ID NO: 196). In some embodiments, the MM comprises the sequence EDCVPYYYACAY (SEQ ID NO: 213), EVGSSDCVPYYYACAY (SEQ ID NO: 214), EDCDAFYPYCDS (SEQ ID NO: 215), or EVGHSDCDAFYPYCDS (SEQ ID NO: 216).

[0142] In some embodiments, the masking moiety (MM) comprises an amino acid sequence selected from NFVADSCPDHPYPCSA (SEQ ID NO: 141), IVHHSDCDAFYPYCDS (SEQ ID NO: 142), YSAYPACDSHYPYCNS (SEQ ID NO: 143), PNPSSDCVPYYYACAY (SEQ ID NO: 144), YSAYPACDSHYPYCQS (SEQ ID NO: 145), PQPSSDCVPYYYACAY (SEQ ID NO: 146), and PNPASDCVPYYYACAY (SEQ ID NO: 147).

[0143] In some embodiments, any of the masking moieties (MM) described herein may further comprise one or more additional amino acid sequences (e.g., one or more polypeptide tags). Examples of suitable additional amino acid sequences may include, but are not limited to, purification tags (e.g., his tags, flag tags, maltose binding protein, and glutathione-S-transferase tags), detection tags (e.g., tags that can be photometrically detected (e.g., red or green fluorescent protein, etc.), tags with detectable enzymatic activity (e.g., alkaline phosphatase, etc.), tags containing secretion sequences, leader sequences, and / or stabilizing sequences, protease cleavage sites (e.g., furin cleavage sites, TEV cleavage sites, thrombin cleavage sites), and the like. In some embodiments, the one or more additional amino acid sequences are at the N-terminus of the masking moiety (MM). In some embodiments, the additional amino acid sequence comprises or consists of the sequence EVGSY (SEQ ID NO: 148).

[0144] In some embodiments, the masking moiety binds to the target binding moiety (TBM) and inhibits the activatable antibody from binding to its target prior to activation (e.g., prior to treatment with one or more proteases that cleave within the cleavable moiety (CM), prior to undergoing a (local) change in pH (increase or decrease), prior to a temperature change (increase or decrease), prior to contact with a second molecule (such as a small molecule or protein ligand), etc.), but does not bind to the TBM and / or inhibit the activatable antibody from binding to its target after activation (e.g., after treatment with one or more proteases that cleave within the cleavable moiety (CM), after undergoing a (local) change in pH (increase or decrease), after a temperature change (increase or decrease), after contact with a second molecule (such as a small molecule or protein ligand), etc.). In some embodiments, the masking moiety (MM) inhibits the binding of the activatable antibody to its target if the CM is not cleaved, but does not inhibit the binding of the activatable antibody to its target if the CM is cleaved. In some embodiments, the masking moiety (MM) has a dissociation constant for binding to the TBM that is greater than the dissociation constant of the activatable antibody (when in activated form) for its target (e.g., at least about 1.5-fold greater, at least about 2-fold greater, at least about 2.5-fold greater, at least about 3-fold greater, at least about 3.5-fold greater, at least about 4-fold greater, at least about 4.5-fold greater, at least about 5-fold greater, at least about 10-fold greater, at least about 100-fold greater, at least about 500-fold greater, etc.).

[0145] Cuttable part (CM) In some embodiments, the present disclosure relates to activatable antibodies that comprise a cleavable moiety (CM), which can be cleaved and / or destroyed by treatment with one or more proteases that cleave within the cleavable moiety (CM), by a change in pH (increasing or decreasing), by a change in temperature (increasing or decreasing), and / or by contact with a second molecule (such as a small molecule or protein ligand), etc.

[0146] In some embodiments, the cleavable moiety (CM) comprises at least a first cleavage site (CS1) (e.g., a first protease cleavage site). In some embodiments, the first cleavage site is a first protease cleavage site. Any suitable protease cleavage site that is recognized and / or cleaved by any protease known in the art (e.g., a protease known to co-exist with the target of an activatable antibody, including a CM) may be used, including, for example, urokinase-type plasminogen activator (uPA), matrix metalloproteinases (e.g., MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-10, MMP-11, MMP-12, MMP-13, MMP-14, MMP-15, MMP-16, MMP-17, MMP-19, MMP-20, MMP-23, MMP-24, MMP-26, and / or MMP-27), tobacco etch virus (TEV) protease, plasmin, thrombin, PSA, PSMA, ADAMS / ADAMTS (e.g., ADAM 8, ADAM 9, ADAM10, ADAM12, ADAM15, ADAM17 / TACE, ADAMDEC1, ADAMTS1, ADAMTS4, and / or ADAMTS5), caspases (e.g., caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, and / or caspase-14), aspartic proteases (e.g., RACE and / or renin), aspartic cathepsins (e.g., cathepsin D and / or cathepsin E), cysteine ​​cathepsins (e.g., cathepsin B, cathepsin C, cathepsin K, cathepsin L, cathepsin S, cathepsin V / L2, and / or cathepsin X / Z / P), cysteine ​​proteinases (e.g., cruzipain, legumain, and / or Otubain-2), KLKs (e.g., KLK4, KLK5, KLK6, KLK7, KLK8, KLK10, KLK11, KLK13, and / or KLK14), metalloproteinases (e.g., meprin, neprilysin, PSMA, and / or BMP-1), serine proteases (e.g.,Included are protease cleavage sites recognized and / or cleaved by activated protein C, cathepsin A, cathepsin G, chymase, and / or coagulation factor proteases (e.g., FVIIa, FIXa, FXa, FXIa, FXIIa), elastase, granzyme B, guanidinobenzoatase, HtrA1, human neutrophil elastase, lactoferrin, marapsin, NS3 / 4A, PACE4, tPA, tryptase, type II transmembrane serine proteases (TTSPs) (e.g., DESC1, DPP-4, FAP, hepsin, matriptase-2, MT-SP1 / matriptase, TMPRSS2, TMPRSS3, and / or TMPRSS4), and the like. In some embodiments, the first protease cleavage site is a cleavage site for a protease selected from uPA, MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, TEV protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin S, ADAM10, ADAM12, ADAMTS, caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE. In some embodiments, the first protease cleavage site is a cleavage site for a protease selected from uPA, MMP-2, MMP-9, and / or TEV protease. In some embodiments, the protease cleavage comprises an amino acid sequence selected from SGRSA (SEQ ID NO: 149), PLGLAG (SEQ ID NO: 150), and ENLYFQG (SEQ ID NO: 151).

[0147] In some embodiments, the activatable antibody comprises a masking portion (MM) and a cleavable portion (CM) comprising an amino acid sequence according to formula (XXV): EVGSY(Z6)C(Z6)C(Z2)SGRSA (sequence number 152), where each Z is independently an amino acid selected from D, A, Y, S, T, N, I, L, F, V, H, and P.

[0148] In some embodiments, the activatable antibody comprises a masking portion (MM) and a cleavable portion (CM) comprising an amino acid sequence according to formula (XXVI): EVGSY(Z6)C(X6)C(Z2)SGRSA (SEQ ID NO: 153), where each X is independently an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0149] In some embodiments, the activatable antibody comprises a masking portion (MM) and a cleavable portion (CM) comprising an amino acid sequence according to formula (XXVII): EVGSY(Z6)C(Z8)C(Z2)SGRSA (sequence number 154), where each Z is independently an amino acid selected from D, A, Y, S, T, N, I, L, F, V, H, and P.

[0150] In some embodiments, the activatable antibody comprises a masking portion (MM) and a cleavable portion (CM) comprising an amino acid sequence according to formula (XXVIII): EVGSY(Z6)C(X8)C(Z2)SGRSA (SEQ ID NO: 155), where each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0151] In some embodiments, the cleavable moiety (CM) further comprises a first linker (L1). In some embodiments, the first linker (L1) is C-terminal to the first cleavage site (CS1) (e.g., the first protease cleavage site). In some embodiments, the cleavable moiety (CM) comprises, from the N-terminus to the C-terminus, the structure (CS1)-L1.

[0152] Any suitable linker (e.g., flexible linker) known in the art may be used, including, for example, glycine polymers (G)n, where n is an integer of at least 1 (e.g., at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, etc.); glycine-serine polymers (GS)n, where n is an integer of at least 1 (e.g., at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, etc.), such as GGGGS (SEQ ID NO:156), SGGS (SEQ ID NO:157), GGSG (SEQ ID NO:158), GGSGG (SEQ ID NO:159), GSGSG (SEQ ID NO:160), GSGGG (SEQ ID NO:161), GGGSG (SEQ ID NO:162), and / or GSSSG (SEQ ID NO:163). glycine alanine polymers; alanine-serine polymers, and the like. The linker sequence can be any length, such as, for example, from about 1 amino acid (e.g., glycine or serine) to about 20 amino acids (e.g., a 20 amino acid glycine polymer or glycine-serine polymer), from about 1 amino acid to about 15 amino acids, from about 3 amino acids to about 12 amino acids, from about 4 amino acids to about 10 amino acids, from about 5 amino acids to about 9 amino acids, from about 6 amino acids to about 8 amino acids, etc. In some embodiments, the linker is any of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acids in length. In some embodiments, the linker comprises an amino acid sequence selected from SEQ ID NOs: 159-163. In some embodiments, the linker comprises the amino acid sequence of SEQ ID NO: 156 or 157.

[0153] In some embodiments, the cleavable moiety (CM) further comprises at least a second cleavage site (e.g., at least a second, at least a third, at least a fourth, at least a fifth, etc.). In some embodiments, the cleavable moiety (CM) further comprises a second cleavage site (CS2). In some embodiments, the second cleavage site is a second protease cleavage site. The second protease cleavage site can be any suitable protease cleavage site recognized and / or cleaved by any of the proteases listed above. In some embodiments, the first (CS1) and second (CS2) cleavage sites are protease cleavage sites recognized and / or cleaved by the same protease. In some embodiments, the first (CS1) and second (CS2) cleavage sites are protease cleavage sites recognized and / or cleaved by different proteases (e.g., the first protease cleavage site is recognized and / or cleaved by uPA and the second protease cleavage site is recognized and / or cleaved by MMP-2; the first protease cleavage site is recognized and / or cleaved by uPA and the second protease cleavage site is recognized and / or cleaved by MMP-9; the first protease cleavage site is recognized and / or cleaved by uPA and the second protease cleavage site is recognized and / or cleaved by TEV protease, etc.). In some embodiments, at least the second cleavage site (CS2) is at the C-terminus of the first linker (L1). In some embodiments, the cleavable moiety (CM) comprises the structure (CS1)-L1-(CS2) from the N-terminus to the C-terminus.

[0154] In some embodiments, the cleavable moiety (CM) further comprises at least a second linker (e.g., at least a second, at least a third, at least a fourth, at least a fifth, etc.). In some embodiments, the cleavable moiety (CM) further comprises a second linker (L2). The second linker (L2) can be any suitable linker described above. In some embodiments, the second linker comprises an amino acid sequence selected from SEQ ID NOs: 156-163. In some embodiments, the first (L1) and second (L2) linkers are the same (e.g., both linkers comprise the sequence of SEQ ID NO: 156 or 157). In some embodiments, the first (L1) and second (L2) linkers are different (e.g., the first linker (L1) comprises the amino acid sequence of SEQ ID NO: 156, the second linker (L2) comprises the amino acid sequence of SEQ ID NO: 157, etc.). In some embodiments, at least the second linker (L2) is C-terminal to the second cleavage site (CS2). In some embodiments, the cleavable moiety (CM) comprises the structure, from N-terminus to C-terminus, (CS1)-L1-(CS2)-L2.

[0155] Exemplary MM-CM sequences In some embodiments, an activatable antibody of the present disclosure comprises the structure, from N-terminus to C-terminus, (FP)-(PCS1)-L1-(PCS2)-L2. In some embodiments, an activatable antibody comprises an amino acid sequence according to formula (XXIX): EVGSYX1X2X3X4X5X6CX7X8X9X 10 X 11 X 12 CX 13 X 14X is A, D, I, N, P, or Y; X is A, F, N, S, or V; X is A, H, L, P, S, V, or Y; X is A, H, S, or Y; X is A, D, L, S, or Y; X is A, D, L, S, or Y; X is D, P, or V; X is A, D, H, P, S, or T; X is A, D, F, H, P, or Y; X is L, P, or Y; X is F, P, or Y; X is A, P, S, or Y;In some embodiments, an activatable antibody of the disclosure is selected from the group consisting of EVGSYDALHYACPPDYYACYYSGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 165), EVGSYNSYHAYCPHPLYPCTASGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 166), EVGSYASSAVLCVTAYFSCNSSGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 167), EVGSYNFVADSCPDHPYPCSASGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 168), EVGSYNFVADSCPDHPYPCSASGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 169), EVGSYIVHHSDCDAFYPYCDSSGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 170), EVGSYIVHHSDCDAFYPYCDSSGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 171), EVGSYYSAYPACDSHYPYC NSSGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 172), EVGSYYSAYPACDSHYPYCNSSGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 173), EVGSYPNPSSDCVPYYYACAYSGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 174), EVGSYPNPSSDCVPYYYACAYSGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 175), EVGSYYSAYPACDSHYPYCQSSGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 176), EVGSYYSAYPACDSHYPYCNSAGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 177), EVGSYPQPSSDCVPYYYACAYSGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 178), and / or EVGSYPNPASDCVPYYYACAYSGRSAGGGGSPLGLAGSGGS (SEQ ID NO: 179). In some embodiments, a polypeptide of the disclosure comprises the structure, from N-terminus to C-terminus, (FP)-(PCS1)-L1-(PCS2)-L2-(TBM).

[0156] In some embodiments, the activatable antibody comprises the amino acid sequence SGRSAGGGGTENLYFQGSGGS (SEQ ID NO: 220), SGRSAGGGGTPLGLAGSGGS (SEQ ID NO: 221), or SGRSAPLGLA (SEQ ID NO: 222). In some embodiments, the activatable antibody comprises the sequence EV(Zn)C(X8)C(Z2)SGRSA (SEQ ID NO: 217), EDC(Z6)C(Z2)SGRSA (SEQ ID NO: 218), or EDC(Z6)C(Z2)PLGLA (SEQ ID NO: 219), where each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, wherein n is 1 to 11, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0157] Target binding moiety (TBM) In some embodiments, the present disclosure relates to an activatable antibody comprising a target binding moiety (TBM). In some embodiments, the target binding moiety (TBM) comprises an antibody light chain variable region and / or an antibody heavy chain variable region. In some embodiments, the target binding moiety (TBM) comprises an antibody light chain variable region. In some embodiments, the target binding moiety (TBM) comprises an antibody heavy chain variable region. In some embodiments, the target binding moiety (TBM) comprises an antibody light chain variable region and an antibody heavy chain variable region.

[0158] In some embodiments, the target binding moiety (TBM) comprises a full-length antibody light chain and / or a full-length antibody heavy chain. The antibody light chain can be a kappa or lambda light chain. The antibody heavy chain can be of any class, such as IgG, IgM, IgE, IgA, or IgD. In some embodiments, the antibody heavy chain is an IgG class, such as an IgG1, IgG2, IgG3, or IgG4 subclass. The antibody heavy chains described herein can be converted from one class or subclass to another class or subclass using methods known in the art.

[0159] Any one or more of the target binding moieties (TBMs) described herein may incorporate any of the HVR sequences described herein (e.g., one, two or three of the heavy chain variable region HVR sequences, and / or one, two or three of the light chain variable region HVR sequences as shown in Table A above), any of the heavy chain variable region sequences and / or light chain variable region sequences described herein (e.g., the heavy chain variable region sequences and / or light chain variable region sequences as shown in Table B above), and / or any of the antibodies described herein.

[0160] In some embodiments, the target binding moiety (TBM) comprises the sequence of one or more of the anti-CTLA4 antibodies described herein, including the antibodies described with respect to the specific amino acid sequences of the HVRs, variable regions (VL, VH), and / or light and heavy chains (e.g., IgG1, IgG2, IgG4). In some embodiments, the target binding moiety (TBM) comprises an antibody light chain variable region comprising an HVR-L1 comprising the amino acid sequence RASQSVRGRFLA (SEQ ID NO:58), an HVR-L2 comprising the amino acid sequence DASNRATGI (SEQ ID NO:66), and / or an HVR-L3 comprising the amino acid sequence YCQQSSSWPPT (SEQ ID NO:75). In some embodiments, the target binding moiety (TBM) comprises an antibody light chain variable region comprising the amino acid sequence of SEQ ID NO:100, or a sequence having at least 90% (e.g., 95%, 96%, 97%, 98%, or 99%) sequence identity to the sequence of SEQ ID NO:100. In some embodiments, the target binding moiety (TBM) comprises an antibody heavy chain variable region comprising an HVR-H1 comprising the amino acid sequence YSISSGYHWSWI (SEQ ID NO: 23), an HVR-H2 comprising the amino acid sequence LARIDWDDDKYYSTSLKSRL (SEQ ID NO: 35), and / or an HVR-H3 comprising the amino acid sequence ARSYVYFDY (SEQ ID NO: 45). In some embodiments, the target binding moiety (TBM) comprises an antibody heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 87, or a sequence having at least 90% (e.g., 95%, 96%, 97%, 98%, or 99%) sequence identity to the sequence of SEQ ID NO: 87. In some embodiments, the target binding moiety (TBM) comprises: a) an antibody light chain variable region comprising HVR-L1 comprising the amino acid sequence RASQSVRGRFLA (SEQ ID NO:58), HVR-L2 comprising the amino acid sequence DASNRATGI (SEQ ID NO:66), and / or HVR-L3 comprising the amino acid sequence YCQQSSSWPPT (SEQ ID NO:75), and b) an antibody heavy chain variable region comprising HVR-H1 comprising the amino acid sequence YSISSGYHWSWI (SEQ ID NO:23), HVR-H2 comprising the amino acid sequence LARIDWDDDKYYSTSLKSRL (SEQ ID NO:35), and / or HVR-H3 comprising the amino acid sequence ARSYVYFDY (SEQ ID NO:45).In some embodiments, the target binding moiety (TBM) comprises an antibody light chain variable region comprising the amino acid sequence of SEQ ID NO:100, and an antibody heavy chain variable region comprising the amino acid sequence of SEQ ID NO:87.

[0161] Properties of activatable binding polypeptides In some embodiments, an activatable binding polypeptide (i.e., an activatable antibody) of the disclosure comprises (a) a masking moiety (MM), (b) a cleavable moiety, and (c) a target binding moiety. In some embodiments, the masking moiety (MM) binds to the target binding moiety (TBM) of the activatable antibody and reduces or inhibits binding of the activatable binding moiety to CTLA4 (e.g., human CTLA4) compared to binding of a corresponding binding polypeptide lacking the masking moiety to CTLA4 (e.g., human CTLA4) and / or compared to binding of a parent antibody to CTLA4 (e.g., human CTLA4).

[0162] In some embodiments, an "activatable" binding polypeptide refers to a binding polypeptide that exhibits a first level of binding to CTLA4 when in an inhibited, masked, and / or uncleaved state, and a second level of binding to CTLA4 when in an uninhibited, unmasked, and / or cleaved state, the second level of CTLA4 binding being greater than the first level of CTLA4 binding. In some embodiments, access to CTLA4 by an activatable binding polypeptide is increased following cleavage within the cleavable moiety (e.g., by one or more proteases).

[0163] In some embodiments, activatable antibodies of the disclosure generally exhibit at least about 2-fold (e.g., at least about 2-fold, at least about 2.5-fold, at least about 3-fold, at least about 3-fold, at least about 4-fold, at least about 5-fold, at least about 6-fold, at least about 7-fold, at least about 8-fold, at least about 9-fold, at least about 10-fold, at least about 15-fold, at least about 16-fold, at least about 17-fold, at least about 18-fold, at least about 20-fold, at least about 25-fold, at least about 20-fold, at least about 30-fold, at least about 40-fold, at least about 50-fold, at least about 60-fold, at least about 70-fold, at least about 80-fold, at least about 90-fold, at least about 100-fold, at least about 15-fold, at least about 16-fold, at least about 20-fold, at least about 20-fold, at least about 20-fold, at least about 30-fold, at least about 30-fold, at least about 40-fold, at least about 50-fold, at least about 15-fold, at least about 2 ... An activatable antibody of the present disclosure is generally considered to be an "activatable" binding polypeptide if the EC of the activatable antibody is increased by at least about 0.5-fold, at least about 4-fold, at least about 4.5-fold, at least about 5-fold, at least about 5.5-fold, at least about 6-fold, at least about 6.5-fold, at least about 7-fold, at least about 7.5-fold, at least about 8-fold, at least about 8.5-fold, at least about 9-fold, at least about 9.5-fold, at least about 10-fold, at least about 25-fold, at least about 50-fold, at least about 75-fold, at least about 100-fold, at least about 250-fold, at least about 500-fold, at least about 750-fold, or at least about 1000-fold or more. 50 is reduced by at least about 2-fold (e.g., at least about 2-fold, at least about 2.5-fold, at least about 3-fold, at least about 3.5-fold, at least about 4-fold, at least about 4.5-fold, at least about 5-fold, at least about 5.5-fold, at least about 6-fold, at least about 6.5-fold, at least about 7-fold, at least about 7.5-fold, at least about 8-fold, at least about 8.5-fold, at least about 9-fold, at least about 9.5-fold, at least about 10-fold, at least about 25-fold, at least about 50-fold, at least about 75-fold, at least about 100-fold, at least about 250-fold, at least about 500-fold, at least about 750-fold, or at least about 1000-fold or more) following "activation" (e.g., as measured by ELISA or FACS assay; see Examples below). In some embodiments, activatable antibodies of the present disclosure generally have an EC of the polypeptide that is greater than or equal to 100 fold. 50is considered "activatable" if it is reduced by at least about two-fold following treatment with a protease that cleaves within the cleavable moiety (CM) (e.g., as measured by ELISA or FACS assay; see Examples below).

[0164] In some embodiments, the K of an activatable antibody to CTLA4 when a masking moiety (MM) is attached to the target binding moiety (TBM) of the activatable antibody. D is greater than when the masking moiety (MM) is not attached to the target binding moiety (TBM) (e.g., after "activation" of the activatable antibody (e.g., after treatment with a protease that cleaves within the cleavable moiety (CM)) and / or the K D about 2-fold or more (e.g., about 2, about 2.5, about 3, about 3.5, about 4, about 4.5, about 5, about 5.5, about 6, about 6.5, about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 25, about 50, about 75, about 100, about 250, about 500, about 750, or about 1000 or more) greater than. Methods of measuring affinity are known in the art and include, for example, the methods described in the Examples below.

[0165] In some embodiments, when the masking moiety is attached to the target binding portion of the activatable antibody, the K D is compared to when the masking moiety is not bound to the target binding moiety (e.g., after "activation" of the activatable antibody (e.g., after treatment with a protease that cleaves within the cleavable moiety (CM))) and / or the K D is decreased by at least about 25% (e.g., at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 99%) compared to. Methods of measuring affinity are known in the art and include, for example, the methods described in the Examples below.

[0166] In some embodiments, the masking moiety sterically masks binding of the activatable antibody to CTLA4 and / or allosterically masks binding of the activatable antibody to CTLA4, hi some embodiments, the masking moiety does not comprise the amino acid sequence of the natural binding partner of the activatable antibody and / or parent antibody.

[0167] In some embodiments, the dissociation constant of the masking moiety for the target binding moiety is greater than the dissociation constant of the activatable antibody (when activated) for CTLA4. In some embodiments, the dissociation constant of the masking moiety for the target binding moiety is greater than about 2-fold or more (e.g., about 2, about 2.5, about 3, about 3.5, about 4, about 4.5, about 5, about 5.5, about 6, about 6.5, about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 25, about 50, about 75, about 100, about 250, about 500, about 750, or about 1000-fold or more) greater than the dissociation constant of the activatable antibody (when activated) for CTLA4. In some embodiments, the dissociation constant of the masking moiety for the target binding moiety is approximately equal to the dissociation constant of the activatable antibody (when activated) for CTLA4.

[0168] The activatable antibodies described herein may be further modified. In some embodiments, the activatable antibodies are linked to additional molecular entities. Examples of additional molecular entities include pharmaceutical agents, peptides or proteins, detection agents or labels, and antibodies.

[0169] In some embodiments, the activatable antibodies of the present disclosure are linked to a pharmaceutical agent. Examples of pharmaceutical agents include cytotoxic agents or other cancer therapeutic agents, and radioisotopes. Specific examples of cytotoxic agents include taxol, cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, tenoposide, vincristine, vinblastine, corticine, doxorubicin, daunorubicin, dihydroxyanthracin dione, mitoxantrone, mithramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine, propranolol, puromycin, and analogs or homologs thereof. Therapeutic agents also include, for example, antimetabolites (e.g., methotrexate, 6-mercaptopurine, 6-thioguanine, cytarabine, 5-fluorouracil decarbazine), alkylating agents (e.g., mechlorethamine, thiotepa chlorambucil, melphalan, carmustine (BSNU) and lomustine (CCNU), cyclosporine, busulfan, dibromomannitol, streptozotocin, mitomycin C, and cis-dichlorodiamine platinum (II) (DDP) cisplatin), anthracyclines (e.g., daunorubicin (formerly daunomycin) and doxorubicin), antibiotics (e.g., dactinomycin (formerly actinomycin), bleomycin, mithramycin, and anthramycin (AMC)), and antimitotic agents (e.g., vincristine and vinblastine). Examples of radioisotopes that can be conjugated to antibodies for diagnostic or therapeutic use include iodine. 131 ,indium 111 ,yttrium 90 , and lutetium 177Methods of linking a polypeptide to a pharmaceutical agent are known in the art, including, but not limited to, using a variety of linker technologies. Exemplary linker types include hydrazones, thioethers, esters, disulfides, and peptide-containing linkers. For further discussion of linkers and methods for linking therapeutic agents to antibodies, see, e.g., Saito et al., Adv. Drug Deliv. Rev. 55:199-215 (2003); Trail, et al., Cancer Immunol. Immunother. 52:328-337 (2003); Payne, Cancer Cell 3:207-212 (2003); Allen, Nat. Rev. Cancer 2:750-763 (2002); Pastan and Kreitman, Curr. Opin. Investig. Drugs 3:1089-1091 (2002); Senter and Springer (2001) Adv. Drug Deliv. Rev. 53:247-264.

[0170] V. Nucleic Acids, Vectors, Host Cells, and Recombinant Methods for Producing CTLA4 Antibodies and / or Precision / Context-Dependent Activatable Antibodies Another aspect of the present disclosure provides an isolated nucleic acid molecule comprising a nucleotide sequence encoding the amino acid sequence of a binding molecule (e.g., an antibody or an activatable antibody) provided herein. The amino acid sequence encoded by the nucleotide sequence can be any part of an antibody, such as an HVR, a sequence comprising one, two, or three HVRs, a variable region of a heavy chain, a variable region of a light chain, or a full-length heavy chain or a full-length light chain. The nucleic acid of the present disclosure can be, for example, DNA or RNA, and may or may not contain intron sequences. Typically, the nucleic acid is a cDNA molecule.

[0171] In some embodiments, the disclosure provides isolated nucleic acid molecules comprising or consisting of a nucleotide sequence encoding an amino acid sequence selected from the group consisting of: (1) the amino acid sequences of HVR-H1, HVR-H2, HVR-H3, HVR-L1, HVR-L2 and / or HVR-L3 of the exemplary antibodies described herein; (2) the variable region of the heavy chain and / or the variable region of the light chain of the exemplary antibodies described herein; or (3) the full-length heavy chain or full-length light chain of the exemplary antibodies.

[0172] In some embodiments, the nucleic acid molecule comprises or consists of a nucleotide sequence encoding the amino acid sequence set forth in any one of SEQ ID NOs: 18-107.

[0173] In some embodiments, the nucleic acid molecule comprises or consists of a nucleotide sequence set forth in Table C below. TIFF0007678841000007.tif255170TIFF0007678841000008.tif255170TIFF0007678841000009.tif244170TIFF0007678841000010.tif255170 TIFF0007678841000011.tif255170TIFF0007678841000012.tif255170TIFF0007678841000013.tif251170TIFF0007678841000014.tif148170

[0174] The nucleic acids of the present disclosure can be obtained using any suitable molecular biology technique. In the case of antibodies expressed by hybridomas, cDNAs encoding the light and heavy chains of the antibodies produced by the hybridomas can be obtained by PCR amplification or cDNA cloning techniques. In the case of antibodies obtained from an immunoglobulin gene library (e.g., using phage display technology), nucleic acids encoding the antibodies can be recovered from the library.

[0175] V H The isolated DNA encoding the region is HA full-length heavy chain gene can be obtained by operably linking the DNA encoding the heavy chain constant region (CH1, CH2, and CH3) to another DNA molecule encoding the heavy chain constant region. The sequences of human heavy chain constant region genes are known in the art (see, for example, Kabat et al. (1991) NIH Publication No. 91-3242), and DNA fragments encompassing these regions can be obtained by standard PCR amplification. The heavy chain constant region can be an IgG1, IgG2, IgG3, IgG4, IgA, IgE, IgM, or IgD constant region. In the case of a Fab fragment heavy chain gene, the V H The DNA encoding the heavy chain CH1 constant region can be operably linked to another DNA molecule encoding only the heavy chain CH1 constant region.

[0176] V L The isolated DNA encoding the region is L The DNA encoding the light chain constant region CL can be operably linked to another DNA molecule encoding the light chain constant region CL to convert it into a full-length light chain gene (as well as a Fab light chain gene). The sequences of human light chain constant region genes are known in the art (see, for example, Kabat et al. (1991) NIH Publication No. 91-3242), and DNA fragments encompassing these regions can be obtained by standard PCR amplification. The light chain constant region can be a kappa or lambda constant region.

[0177] To generate the scFv gene, H and V L The DNA fragment encoding V H and V L The sequences are linked by a flexible linker L and V HThe fragment encodes a flexible linker, e.g., an amino acid sequence (Gly4-Ser)3, which is operably linked to another fragment encoding the amino acid sequence (Gly4-Ser)3, so that the fragment may be expressed as a contiguous single-chain protein having the domain (see, e.g., Bird et al., Science 242:423-426 (1988); Huston et al., Proc. Natl. Acad. Sci. USA 85:5879-5883 (1988); and McCafferty et al., Nature 348:552-554 (1990)).

[0178] The present disclosure further provides vectors comprising the nucleic acid molecules described herein. In some embodiments, the vector is an expression vector or a display vector (e.g., a viral display vector, a bacterial display vector, a yeast display vector, an insect display vector, a mammalian display vector, etc.). The nucleic acid molecule may encode a portion of a light or heavy chain (e.g., a CDR or HVR, a light or heavy chain variable region), a full-length light or heavy chain, a polypeptide comprising a portion or the full-length of a heavy or light chain, or an amino acid sequence of an antibody derivative or antigen-binding fragment. In some embodiments, the vector is an expression vector useful for expressing a binding molecule, such as an antibody or antigen-binding fragment thereof. In some embodiments, vectors are provided herein, where a first vector comprises a polynucleotide sequence encoding a heavy chain variable region described herein, and a second vector comprises a polynucleotide sequence encoding a light chain variable region described herein. In some embodiments, a single vector comprises a polynucleotide encoding a heavy chain variable region described herein and a light chain variable region described herein.

[0179] To express the binding molecules of the present disclosure, DNA encoding partial or full-length light and heavy chains is inserted into an expression vector such that the DNA molecule is operably linked to transcriptional and translational control sequences. In this context, the term "operably linked" means that the antibody gene is ligated into a vector such that the transcriptional and translational control sequences in the vector perform their intended function of regulating the transcription and translation of the DNA molecule. The expression vector and expression control sequences are selected to be compatible with the expression host cell used. The antibody light chain gene and the antibody heavy chain gene can be inserted into separate vectors, or both genes can be inserted into the same expression vector. The antibody gene is inserted into the expression vector by any suitable method (e.g., ligation of complementary restriction sites on the antibody gene fragment and the vector, or homologous recombination-based DNA ligation). The light and heavy chain variable regions of the antibodies described herein are used to ligate the V and VD chains into an expression vector already encoding heavy and light chain constant regions of the desired isotype and subclass. H The segment is C in the vector H operatively coupled to the segment(s), L The segment is C in the vector L By inserting them operably linked to the segment, full-length antibody genes of any antibody isotype and subclass can be generated. Additionally or alternatively, the recombinant expression vector can encode a signal peptide that facilitates secretion of the antibody chain from a host cell. The antibody chain gene can be cloned into the vector such that the signal peptide is linked in-frame to the amino terminus of the antibody chain gene. The signal peptide can be an immunoglobulin signal peptide or a heterologous signal peptide (i.e., a signal peptide from a non-immunoglobulin protein).

[0180] In addition to the antibody sequence, the expression vector of the present disclosure typically has a regulatory sequence that controls the expression of the antibody sequence in a host cell. The term "regulatory sequence" is intended to include promoters, enhancers, and other expression control elements (e.g., polyadenylation signals) that control the transcription or translation of antibody chain genes. Such regulatory sequences are described, for example, in Goeddel (Gene Expression Technology. Methods in Enzymology 185, Academic Press, San Diego, Calif. (1990)). It will be understood by those skilled in the art that the design of the expression vector, including the selection of regulatory sequences, may depend on factors such as the choice of the host cell to be transformed, the expression level of the desired protein, and the like. Examples of regulatory sequences for mammalian host cell expression include viral elements that direct high levels of protein expression in mammalian cells, such as promoters and / or enhancers derived from cytomegalovirus (CMV), simian virus 40 (SV40), adenovirus (e.g., adenovirus major late promoter (AdMLP)), and polyoma. Alternatively, non-viral regulatory sequences such as the ubiquitin promoter or the β-globin promoter can be used. Furthermore, regulatory elements are composed of sequences from various sources, such as the SR promoter system, which contains sequences from the SV40 early promoter and the long terminal repeat of human T-cell leukemia virus type 1 (Takebe, Y. et al. (1988) Mol. Cell. Biol. 8: 466-472).

[0181] In addition to the antibody chain genes and regulatory sequences, expression vectors may carry additional sequences, such as sequences that regulate replication of the vector in host cells (e.g., origins of replication) and selectable marker genes. The selectable marker gene facilitates selection of host cells into which the vector has been introduced (see, e.g., U.S. Pat. Nos. 4,399,216, 4,634,665, and 5,179,017, all by Axel et al.). For example, typically the selectable marker gene confers resistance to drugs, such as G418, hygromycin, or methotrexate, on a host cell into which the vector has been introduced. Selectable marker genes include the dihydrofolate reductase (DHFR) gene (for use in dhfr host cells with methotrexate selection / amplification) and the neo gene (for G418 selection).

[0182] For expression of the light and heavy chains, the expression vector(s) encoding the heavy and light chains are transfected into a host cell by any suitable technique. The various forms of the term "transfection" are intended to encompass a wide variety of techniques commonly used to introduce exogenous DNA into prokaryotic or eukaryotic host cells, such as electroporation, calcium phosphate precipitation, DEAE-dextran transfection, etc. Although the antibodies of the present disclosure can be expressed in either prokaryotic or eukaryotic host cells, expression of the antibodies in eukaryotic cells, and typically mammalian host cells, is most typical.

[0183] The present disclosure further provides a host cell that contains the nucleic acid molecule provided by the present disclosure.The host cell can be virtually any cell for which an expression vector is available.It can be, for example, a higher eukaryotic host cell such as a mammalian cell, a lower eukaryotic host cell such as a yeast cell, or a prokaryotic cell such as a bacterial cell.Methods for introducing recombinant nucleic acid into a host cell are known in the art, and include, for example, calcium phosphate transfection, DEAE, dextran-mediated transfection, electroporation, or phage infection.

[0184] Suitable prokaryotic hosts for transformation include E. coli, Bacillus subtilis, Salmonella typhimurium, and various species within the genera Pseudomonas, Streptomyces, and Staphylococcus.

[0185] Suitable eukaryotic hosts for transformation include yeast, insect (e.g., S2 cells), and mammalian cells. Mammalian host cells for expressing the binding molecules of the present disclosure include, for example, Chinese hamster ovary (CHO) cells (including dhfr-CHO cells as described in Urlaub and Chasin, Proc. Natl. Acad. Sci. USA 77:4216-4220 (1980); Sharp, J. Mol. Biol. 159:601-621 (1982)), NS0 myeloma cells, COS cells, HEK293F cells, HEK293T cells, and Sp2 cells. Another expression system, particularly for use with NS0 myeloma or CHO cells, is the GS (glutamine synthetase) gene expression system disclosed in WO87 / 04462, WO89 / 01036, and EP338,841. In some embodiments, the antibodies of the disclosure are produced in CHO cells. In some embodiments, the antibodies of the disclosure are modified and do not contain a C-terminal lysine residue (e.g., the C-terminal lysine residue of the antibody heavy chain described herein is removed (e.g., before or during antibody production)). When an expression vector encoding an antibody gene is introduced into a mammalian host cell, the antibody is produced by culturing the host cell for a period of time sufficient to allow expression of the antibody in the host cell or secretion of the antibody into the culture medium in which the host cell is growing. The antibody can be recovered from the culture medium using any suitable protein purification method known in the art (e.g., protein A chromatography and / or ion exchange chromatography).

[0186] VI. Composition In other aspects, the present disclosure provides compositions containing a binding molecule (e.g., an antibody or an activatable antibody) provided by the present disclosure. In one aspect, the composition is a pharmaceutical composition comprising the binding molecule (e.g., an antibody or an activatable antibody) and a pharma- ceutically acceptable carrier. The composition can be prepared by conventional methods known in the art.

[0187] In some embodiments, the disclosure provides a composition comprising a binding molecule (e.g., an antibody or activatable antibody) provided by the disclosure and a pharma- ceutically acceptable carrier, the binding molecule comprising a variable domain comprising an HVR amino acid sequence disclosed herein, and the composition comprising less than about 11%, 10%, 8%, 5%, 3%, or 2% of the binding molecules (e.g., antibodies or activatable antibodies) glycosylated at asparagine of the amino acid sequence relative to the total amount of binding molecules (e.g., antibodies or activatable antibodies) present in the composition. In another embodiment, the composition comprises at least about 2% of the binding molecules (e.g., antibodies or activatable antibodies) glycosylated at asparagine of the amino acid sequence relative to the total amount of binding molecules (e.g., antibodies or activatable antibodies) present in the composition.

[0188] The term "pharmaceutical acceptable carrier" refers to any inert material suitable for use in a formulation for delivery of a binding molecule. Carriers can be anti-adherents, binders, coatings, disintegrants, fillers or diluents, preservatives (such as antioxidants, antibacterial agents, or antifungal agents), sweeteners, absorption retardants, wetting agents, emulsifiers, buffers, etc. Examples of suitable pharmaceutical acceptable carriers include water, ethanol, polyols (such as glycerol, propylene glycol, polyethylene glycol), glucose, vegetable oils (such as olive oil), saline, buffers, buffered saline, and isotonic agents such as sugars, polyalcohols, sorbitol, and sodium chloride.

[0189] The composition may be in any suitable form, such as liquid, semi-solid, and solid dosage forms. Examples of liquid dosage forms include solutions (e.g., injectable and infusible solutions), microemulsions, liposomes, dispersions, or suspensions. Examples of solid dosage forms include tablets, pills, capsules, microcapsules, and powders. A particular form of the composition suitable for delivering a binding molecule (e.g., an antibody or an activatable antibody) is a sterile liquid, such as a solution, suspension, or dispersion for injection or infusion. A sterile solution can be prepared by incorporating the required amount of the antibody in a suitable carrier, followed by sterile microfiltration. In general, a dispersion is prepared by incorporating the binding molecule (e.g., an antibody or an activatable antibody) into a sterile vehicle containing a basic dispersion medium and other carriers. In the case of a sterile powder for the preparation of a sterile liquid, the preparation method includes vacuum drying and freeze-drying (lyophilization) to obtain a powder containing the active ingredient plus any additional desired ingredients from its previously sterile-filtered solution. Various dosage forms of the composition can be prepared by conventional techniques known in the art.

[0190] The relative amount of binding molecule (e.g., antibody or activatable antibody) included in the composition will vary depending on many factors, such as the particular binding molecule and carrier used, the dosage form, and the desired release and pharmacodynamic properties. The amount of binding molecule (e.g., antibody or activatable antibody) in a single dosage form will generally be that amount that provides a therapeutic effect, but may be a lesser amount. Generally, this amount will range from about 0.01 percent to about 99 percent, from about 0.1 percent to about 70 percent, or from about 1 percent to about 30 percent, based on the total weight of the dosage form.

[0191] In addition to the binding molecule (e.g., antibody or activatable antibody), one or more additional therapeutic agents can be included in the composition. Examples of additional therapeutic agents are described herein below. The suitable amount of additional therapeutic agent to be included in the composition can be easily selected by those skilled in the art and will vary depending on many factors, such as the specific drug and carrier used, dosage form, and desired release and pharmacodynamic properties. The amount of additional therapeutic agent included in a single dosage form is generally the amount of drug that produces a therapeutic effect, but may be a smaller amount.

[0192] Any of the binding molecules (e.g., antibodies or activatable antibodies) and / or compositions (e.g., pharmaceutical compositions) described herein can be used in the preparation of a medicament (e.g., a medicament for use in treating or delaying the progression of cancer in a subject in need thereof).

[0193] VII. Uses of the Binding Molecules and Pharmaceutical Compositions The binding molecules (e.g., antibodies or activatable antibodies) and pharmaceutical compositions provided by the present disclosure are useful for therapeutic, diagnostic, or other purposes, such as modulating immune responses, treating cancer, enhancing the effectiveness of other cancer therapies, enhancing the effectiveness of vaccines, or treating autoimmune diseases. Thus, in another aspect, the present disclosure provides a method of using the binding molecules (e.g., antibodies or activatable antibodies) or pharmaceutical compositions. In one aspect, the present disclosure provides a method of treating a disorder in a mammal, comprising administering to a mammal in need of treatment an effective amount of a binding molecule (e.g., antibodies or activatable antibodies) or composition provided by the present disclosure. The binding molecule (e.g., antibodies or activatable antibodies) can be a CTLA4 antibody (e.g., a human anti-human CTLA4 antibody) or a CTLA4 activatable antibody. In some embodiments, the mammal is a human.

[0194] In some embodiments, the disorder is cancer. The methods, uses, compositions, or medicaments provided by the present disclosure can be used to treat or prevent a variety of cancers.Examples of such cancers include lung cancers such as bronchogenic carcinoma (e.g., squamous cell carcinoma, small cell carcinoma, large cell carcinoma, and adenocarcinoma), alveolar cell carcinoma, bronchial adenoma, chondroitin hamartoma (non-cancerous), and sarcoma (cancerous); cardiac cancers such as myxoma, fibroma, and rhabdomyoma; bone cancers such as osteochondroma, chondroblastoma, chondromyxoid fibroma, osteoid osteoma, giant cell tumor, chondrosarcoma, multiple myeloma, osteosarcoma, fibrosarcoma, malignant fibrous histiocytoma, Ewing's tumor (Ewing's sarcoma), and reticulum cell sarcoma; gliomas (e.g., glioblastoma multiforme), anaplastic astrocytoma, astrocytoma, gliomas (e.g., glioblastoma multiforme), anaplastic astrocytoma, astrocytoma, gliomas (e.g., glioblastoma multiforme), anaplastic astrocytoma, gliomas (e.g., glioblastoma multiforme), ... brain cancers such as cyst, oligodendroglioma, medulloblastoma, chordoma, schwannoma, ependymoma, meningioma, pituitary adenoma, pinealoma, osteoma, hemangioblastoma, craniopharyngioma, chordoma, germinoma, teratoma, dermoid cyst, and hemangioma; cancers in the digestive system such as leiomyoma, epidermoid carcinoma, adenocarcinoma, leiomyosarcoma, gastric adenocarcinoma, intestinal lipoma, intestinal neurofibroma, intestinal fibroma, colon polyp, and colorectal cancer; liver cancers such as hepatocellular adenoma, hemangioma, hepatocellular carcinoma, fibrolamellar carcinoma, cholangiocarcinoma, hepatoblastoma, and hemangiosarcoma; kidney cancers such as renal adenocarcinoma, renal cell carcinoma, hypernephropathy, and transitional cell carcinoma of the renal pelvis; bladder cancer; acute lymphoblastic blood cancers such as acute myeloid (lymphoblastic) leukemia, acute myeloid (myelocytic, myelogenous, myeloblastic, myelomonocytic) leukemia, chronic lymphocytic leukemia (e.g., Sézary syndrome and hairy cell leukemia), chronic myeloid (myeloid, myeloid, granulocytic) leukemia, Hodgkin's lymphoma, non-Hodgkin's lymphoma, B-cell lymphoma, mycosis fungoides, and myeloproliferative disorders (including myeloproliferative disorders such as polycythemia vera, myelofibrosis, thrombocythemia, and chronic myelogenous leukemia); skin cancers such as basal cell carcinoma, squamous cell carcinoma, melanoma, Kaposi's sarcoma, and Paget's disease; head and neck cancer; retinoblastoma cancers related to the eye, such as melanoma and intraocular melanoma; cancers of the male reproductive system, such as benign prostatic hyperplasia, prostate cancer, and testicular cancer (e.g., seminoma, teratoma, embryonal carcinoma, and choriocarcinoma); breast cancer; cancers of the female reproductive system, such as uterine cancer (endometrial cancer), cervical cancer (cervical carcinoma), ovarian cancer (ovarian carcinoma), vulvar cancer, vaginal cancer, fallopian tube cancer, and hydatidiform mole; thyroid cancer (including papillary, follicular, anaplastic, or medullary carcinoma); pheochromocytoma (adrenal gland); noncancerous growths of the parathyroid glands; pancreatic cancer; and blood cancers, such as leukemia, myeloma, non-Hodgkin's lymphoma, and Hodgkin's lymphoma.

[0195] In another aspect, the disclosure provides a method of enhancing an immune response in a mammal, comprising administering to the mammal an effective amount of a binding molecule (e.g., an antibody or activatable antibody) or composition provided by the disclosure. In some embodiments, the binding molecule is a CTLA4 antibody or antigen-binding fragment thereof, and the mammal is a human. In some embodiments, the binding molecule is a CTLA4 activatable antibody, and the mammal is a human. The term "enhancing an immune response" or grammatical variations thereof means stimulating, eliciting, increasing, improving, or enhancing any response of the immune system of a mammal. The immune response may be a cellular response (i.e., cell-mediated, such as cytotoxic T lymphocyte-mediated), or a humoral response (i.e., antibody-mediated), and may be a primary or secondary immune response. Examples of enhancing an immune response include activation of PBMCs and / or T cells, including increased secretion of one or more cytokines, such as IL-2 and / or IFNγ. The enhanced immune response can be assessed using a number of in vitro or in vivo measurements known to those skilled in the art, including, but not limited to, cytotoxic T lymphocyte assays, cytokine release, tumor regression, survival of tumor-bearing animals, antibody production, immune cell proliferation, expression of cell surface markers, and cytotoxic activity. Typically, the methods of the present disclosure enhance the immune response by a mammal as compared to an immune response by an untreated mammal or a mammal that has not been treated using the cited methods.

[0196] In carrying out the therapy, the binding molecule (e.g., an antibody or an activatable antibody) may be administered alone as a monotherapy or in combination with one or more additional therapeutic agents or therapies. Thus, in another aspect, the present disclosure provides a combination therapy comprising a binding molecule (e.g., an antibody or an activatable antibody) in combination with one or more additional therapies or therapeutic agents for separate, sequential, or simultaneous administration. The term "additional therapeutic agent" may refer to any therapeutic agent other than the binding molecule (e.g., an antibody or an activatable antibody) provided by the present disclosure. In certain aspects, the present disclosure provides a combination therapy for treating cancer in a mammal, comprising administering to the mammal an effective amount of a binding molecule (e.g., an antibody or an activatable antibody) provided herein in combination with one or more additional therapeutic agents. In a further embodiment, the mammal is a human.

[0197] A wide variety of cancer therapeutic agents may be used in combination with the binding molecules (e.g., antibodies or activatable antibodies) provided by the present disclosure. Those skilled in the art will recognize the existence and development of other cancer therapies that can be used in combination with the methods and binding molecules (e.g., antibodies or activatable antibodies) of the present disclosure and will not be limited to the forms of therapy described herein. Examples of categories of additional therapeutic agents that may be used in combination therapy to treat cancer include (1) chemotherapeutic agents, (2) immunotherapeutic agents, and (3) hormonal therapeutic agents. In some embodiments, the additional therapeutic agent is a viral gene therapy, an immune checkpoint inhibitor, a targeted therapy, a radiation therapy, a vaccine therapy, and / or a chemotherapy.

[0198] The term "chemotherapeutic agent" refers to a chemical or biological substance that can cause the death of cancer cells or interfere with the growth, division, repair, and / or function of cancer cells. Examples of chemotherapeutic agents include those disclosed in WO2006 / 129163 and US20060153808, the disclosures of which are incorporated herein by reference. Examples of specific chemotherapeutic agents include: (1) alkylating agents such as chlorambucil (LEUKERAN), cyclophosphamide (CYTOXAN), ifosfamide (IFEX), mechlorethamine hydrochloride (MUSTARGEN), thiotepa (THIOPLEX), streptozotocin (ZANOSAR), carmustine (BICNU, GLIADEL WAFER), lomustine (CEENU), and dacarbazine (DTIC-DOME); (2) doxorubicin (ADRIAMYCIN), epirubicin (ELLENCE, PHARMORUBICIN), daunorubicin (CERUBIDINE, DAUNOXOME), nemorubicin, idarubicin (IDAMYCIN), and the like. (3) alkaloids or plant vinca alkaloids, including cytotoxic antibiotics such as capecitabine (XELODA), cytarabine (CYTOSAR-U), mitoxantrone (DHAD, NOVANTRONE), dactinomycin (ACTINOMYCIN D, COSMEGEN), plicamycin (MITHRACIN), mitomycin (MUTAMYCIN), and bleomycin (BLENOXANE), vinorelbine tartrate (NAVELBINE), vinblastine (VELBAN), vincristine (ONCOVIN), and vindesine (ELDISINE); (4) antimetabolites such as 5-fluorouracil (5-FU), capecitabine (XELODA), raltitrexed (TOMUDEX), tegafur-uracil (UFTORAL), and gemcitabine (GEMZAR); (5) docetaxel (TAXOTERE);(6) platinum agents such as cisplatin (PLATINOL), carboplatin (PARAPLATIN), and oxaliplatin (ELOXATIN); (7) topoisomerase inhibitors such as irinotecan (CAMPTOSAR), topotecan (HYCAMTIN), etoposide (ETOPOPHOS, VEPESSID, TOPOSAR), and teniposide (VUMON); (8) etoposide (ETOPOPHOS, VEPESSID, TOPOSA) and other anti-cancer drugs. (R) and other epipodophyllotoxins (podophyllotoxin derivatives), (9) folic acid derivatives such as leucovorin (WELLCOVORIN), (10) nitrosoureas such as carmustine (BiCNU) and lomustine (CeeNU), (11) gefitinib (IRESSA), erlotinib (TARCEVA), bortezomib (VELCADE), imatinib mesylate (GLEEVEC), genefitinib, lapatinib, sorafenib, thalidomide, sunitinib (SUTENT), axitinib, rituximab, etc. Epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), insulin receptor, insulin-like growth factor receptor (IGFR), hepatocyte growth factor receptor, such as mabs (RITUXAN, MABTHERA), trastuzumab (HERCEPTIN), cetuximab (ERBITUX), bevacizumab (AVASTIN), and ranibizumab (LUCENTIS), lym-1 (ONCOLYM), antibodies against insulin-like growth factor-1 receptor (IGF-1R) described in WO2002 / 053596; (12) inhibitors of receptor tyrosine kinases, including the hemagglutinin receptor (HGFR) and the platelet-derived growth factor receptor (PDGFR); (13) proteasome inhibitors, such as bortezomib (VELCADE); (14) angiogenesis inhibitors, such as bevacizumab (AVASTIN), suramin (GERMANIN), angiostatin, SU5416, thalidomide, and matrix metalloproteinase inhibitors (such as batimastat and marimastat), and those described in WO2002055106.

[0199] The term "immunotherapeutic agent" refers to a chemical or biological substance capable of enhancing the immune response of a mammal. Examples of immunotherapeutic agents include bacillus Calmette-Guerin (BCG); cytokines such as interferons; vaccines such as MyVax personalized immunotherapy, Onyvax-P, Oncophage, GRNVAC1, Favld, Provenge, GVAX, Lovaxin C, BiovaxID, GMXX, and NeuVax; and vaccines such as alemtuzumab (CAMPATH), bevacizumab (AVASTIN), cetuximab (ERBITUX), gemtuzumab ozogamicin (MYLOTARG), ibritumomab tiuxetan (ZEVALIN), panitumumab (VECTIBIX), rituximab (RITUXAN, MABTHERA), trastuzumab (HERCEPTIN), tositumomab (BEXXAR ... These include antibodies such as limumab (YERVOY), tremelimumab, CAT-3888, agonist antibodies against the OX40 receptor (e.g., those disclosed in WO2009 / 079335), agonist antibodies against the CD40 receptor (e.g., those disclosed in WO2003 / 040170), and TLR-9 agonists (e.g., those disclosed in WO2003 / 015711, WO2004 / 016805, and WO2009 / 022215).

[0200] The term "hormonal therapy" refers to a chemical or biological substance that inhibits or eliminates the production of hormones or inhibits or interferes with the effect of hormones on the growth and / or survival of cancerous cells. Examples of such agents suitable for the methods herein include those disclosed in US20070117809. Examples of specific hormonal therapy agents include tamoxifen (NOLVADEX), toremifene (Fareston), fulvestrant (FASLODEX), anastrozole (ARIMIDEX), exemestane (AROMASIN), letrozole (FEMARA), megestrol acetate (MEGACE), goserelin (ZOLADEX), and leuprolide (LUPRON). The binding molecules of the disclosure may also be used in combination with non-drug hormone therapies such as (1) surgical procedures to remove all or part of the organs or glands involved in the production of hormones, such as the ovaries, testes, adrenal glands, and pituitary gland, and (2) radiation therapy, in which a patient's organs or glands are irradiated in an amount sufficient to inhibit or eliminate production of the targeted hormone.

[0201] In some embodiments, the additional therapeutic agent is one or more of pomalyst, Revlimid, lenalidomide, pomalidomide, thalidomide, DNA alkylating platinum-containing derivatives, cisplatin, 5-fluorouracil, cyclophosphamide, anti-CD137 antibody, anti-PD-1 antibody, anti-PD-L1 antibody, anti-CD20 antibody, anti-CD40 antibody, anti-DR5 antibody, anti-CD1d antibody, anti-TIM3 antibody, SLAMF7 antibody, anti-KIR receptor antibody, anti-OX40 antibody, anti-HER2 antibody, anti-ErbB-2 antibody, anti-EGFR antibody, cetuximab, rituximab, trastuzumab, pembrolizumab, radiation therapy, single radiation, fractionated radiation, focal radiation, whole organ radiation, IL-12, IFNα, GM-CSF, chimeric antigen receptor, adoptive transfer T cells, anti-cancer vaccine, and oncolytic virus.

[0202] Combination therapies for treating cancer also include the use of a binding molecule (e.g., an antibody or an activatable antibody) in combination with surgery to remove a tumor. The binding molecule (e.g., an antibody or an activatable antibody) can be administered to the mammal before, during, or after surgery.

[0203] Combination therapies for treating cancer also include the use of binding molecules (e.g., antibodies or activatable antibodies) in combination with radiation therapy, such as ionizing (electromagnetic) radiation therapy (e.g., X-rays or gamma rays) and particle beam radiation therapy (e.g., high linear energy radiation). The source of radiation can be external or internal to the mammal. The binding molecules (e.g., antibodies or activatable antibodies) can be administered to the mammal before, during, or after radiation therapy.

[0204] The binding molecules (e.g., antibodies or activatable antibodies) and compositions provided by the present disclosure can be administered via any suitable enteral or parenteral route of administration. The term "enteral route" of administration refers to administration via any part of the gastrointestinal tract. Examples of enteral routes include oral, mucosal, buccal, and rectal routes, or intragastric routes. A "parenteral route" of administration refers to a route of administration other than the enteral route. Examples of parenteral routes of administration include intravenous, intramuscular, intradermal, intraperitoneal, intratumor, intravesical, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intraarticular, subcapsular, subarachnoid, intraspinal, epidural, and intrasternal, subcutaneous, or topical administration. The binding molecules (e.g., antibodies or activatable antibodies) and compositions of the present disclosure can be administered using any suitable method, such as oral ingestion, nasogastric tube, gastrostomy tube, injection, infusion, implantable infusion pump, and osmotic pump. Suitable routes and methods of administration can vary depending on a number of factors, such as the particular binding molecule (e.g., an antibody or activatable antibody) used, the desired rate of absorption, the particular formulation or dosage form used, the type or severity of the disorder being treated, the particular site of action, and the condition of the patient, and can be readily selected by one of skill in the art.

[0205] The term "effective amount" of a binding molecule (e.g., an antibody or activatable antibody) may refer to an amount effective for the intended therapeutic purpose. For example, in the context of enhancing an immune response, an "effective amount" may be any amount that is effective to stimulate, induce, increase, improve, or enhance any response of the immune system of a mammal. In the context of treating a disease, an "effective amount" may be any amount sufficient to cause any desired or beneficial effect in the treated mammal. Specifically, in the treatment of cancer, examples of desired or beneficial effects include inhibiting further growth or metastasis of cancer cells, killing cancer cells, inhibiting recurrence of cancer, reducing pain associated with cancer, or improving the viability of the mammal. A therapeutically effective amount of a binding molecule (e.g., an antibody or activatable antibody) typically ranges from about 0.001 to about 500 mg / kg, more typically from about 0.01 to about 100 mg / kg of the mammal's body weight. For example, the amount can be about 0.3 mg / kg, 1 mg / kg, 3 mg / kg, 5 mg / kg, 10 mg / kg, 50 mg / kg, or 100 mg / kg of the mammal's body weight. In some embodiments, a therapeutically effective amount of a binding molecule (e.g., an antibody or activatable antibody) is in the range of about 0.01-30 mg / kg of the mammal's body weight. In some other embodiments, a therapeutically effective amount of a binding molecule (e.g., an antibody or activatable antibody) is in the range of about 0.05-15 mg / kg of the mammal's body weight. The exact dosage level to be administered can be readily determined by one of skill in the art and will depend on numerous factors, such as, for example, the type and severity of the disorder being treated, the particular binding molecule (e.g., an antibody or activatable antibody) being employed, the route of administration, the time of administration, the duration of treatment, the particular additional therapy being employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, as well as factors well known in the medical arts.

[0206] A binding molecule (e.g., an antibody or activatable antibody) or composition is usually administered multiple times. The interval between single doses can be, for example, daily, weekly, monthly, every three months, or yearly. Exemplary treatment regimens involve administration once a week, once every two weeks, once every three weeks, once every four weeks, once a month, once every three months, or once every three to six months. A typical dosing regimen for a binding molecule (e.g., an antibody or activatable antibody) includes 1 mg / kg body weight or 3 mg / kg body weight administered intravenously using one of the following dosing schedules: (i) 6 doses every four weeks, then every three months, (ii) every three weeks, (iii) 3 mg / kg body weight once, followed by 1 mg / kg body weight every three weeks.

[0207] VIII. Kit In other aspects, provided herein are kits comprising the binding molecules (e.g., antibodies or activatable antibodies) and / or compositions described herein. In some embodiments, the kits further comprise a package insert comprising instructions for use of the binding molecules (e.g., antibodies or activatable antibodies) and / or compositions. In some embodiments, the kits further comprise one or more buffers, e.g., for storing, transferring, administering, or otherwise using the binding molecules (e.g., antibodies or activatable antibodies) and / or compositions. In some embodiments, the kits further comprise one or more containers for storing the binding molecules (e.g., antibodies or activatable antibodies) and / or compositions.

[0208] The above description is deemed sufficient to enable those skilled in the art to practice the present disclosure. The following examples are presented for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Indeed, in addition to the modifications shown and described herein, various modifications of the present disclosure will become apparent to those skilled in the art from the above description and will fall within the scope of the appended claims. EXAMPLES

[0209] Example 1: Generation of primary Fabs that specifically bind to human CTLA4 A proprietary phagemid library (see PCT Application No. PCT / CN2017 / 098333, incorporated herein by reference in its entirety; see also PCT Application No. PCT / CN2017 / 098299, incorporated herein by reference in its entirety) was used to pan against the human CTLA4 antigen. A total of 3-5 rounds of panning were performed. After the final round of panning, single colony supernatant ELISA was performed to identify primary hits that specifically recognized human CTLA4 (see, e.g., UniProt Accession No. P16410). Primary hits were defined as hits with an ELISA signal at least 2-fold above background. Hits were then sequenced and unique clones were expressed in E. coli and purified. Affinity to human CTLA4 was measured by a ForteBio Octet RED96 system. Briefly, recombinant human CTLA4-Fc (Sino Biological, 11159-H03H) was captured using AHC sensors (Anti-Human IgG Fc Capture Dip and Read Biosensors) and immersed in wells containing purified Fab diluted to 10 μg / mL in kinetic buffer (0.02% Tween 20, 0.1% BSA in PBS buffer). Acquired ForteBio data was processed with Data Acquisition software 7.1 and kinetic data was fitted to a 1:1 Langmuir binding model. The candidate list was narrowed down to 234 Fab hits with both ELISA positive hits and unique sequences. K D Criterion for response signal R>0.1, R 2 >0.9, the list was further narrowed down to 43 hits of interest, whose affinity and kinetic parameters (subtracted background) are shown in Table 1 below. TIFF0007678841000015.tif255170TIFF0007678841000016.tif29170

[0210] The species cross-reactivity of the various Fab hits was then determined by ELISA. Briefly, 100 μL of 1.25 μg / mL anti-human IgG (Fab specific) antibody (Sigma, I5260) was coated on a Maxisorp microplate (Thermo Scientific 446469) overnight at 4 °C. After blocking, 100 μL of Fab hit (2 μg / mL) was added and incubated for 1 h. The wells were washed 3-4 times, after which serial dilutions of human, cynomolgus monkey, or mouse CTLA4 antigen fused to human FC fragment were added and incubated for 1 h. After washing, HRP-labeled goat anti-human FC was diluted 1:2000 in PBS and added to each well for 1 h incubation. The plates were washed 3 times and incubated with TMB substrate for 3-5 min at room temperature. After stopping the reaction, the absorbance at 450 nm was measured. The species cross-reactivity of each Fab tested is outlined below in Table 2.Interestingly, this analysis identified Fabs with different cross-reactivities, and the results showed that hits B13873, B15700, B15704, B15706, B15709, B15711, B15712, B15715, B15720, B15725, B15723, B15731, B15732, B15735, B15736, B15744, B15760, B16083, and B15188 were cross-reactive with human, monkey, and mouse Fabs. CTLA4, hits B15188, B15190, B15701, B15729, B15733, B15742, B15747, B15743, B15751, B15752, B15753, and B18157 bind to human and monkey CTLA4 and weakly bind to mouse CTLA4, hits B13878, B14242, B15189, B15491, B15673, B15694, B15696, B15771, B15772, B15773, B15774, B15775, B15776, B15777, B15778, B15779, B15780, B15781, B15782, B15783, B15784, B15785, B15786, B15787, B15788, B15789, B15791, B15792, B15793, B15794, B15795, B15796, B15797, B15798, B15799, B15799, B15799, B15799, B15791, B15792, B15793, B15794, B15795, B15796, B15797, B15798, B15799, B15799, B1580 ... 5699, B15702, B15705, B15710, B15716, B15717, B15719, B15721, B15722, B15724, B15728, B15734, B15737, B15738, B15739, B15740, B15745, B15746, B15749, B15750, B15754, B15756, B15757, B15759, and B15762 bind to human CTLA4. Hit B15688 bound to human and mouse CTLA4 but not to monkey CTLA4, and hits B13874, B13880, B13898, B15187, B15489, B15672, B15695, B15730, B15741, B18153, and B18174 bound to human CTLA4 but not to monkey or mouse CTLA4. TIFF0007678841000017.tif255170TIFF0007678841000018.tif227170

[0211] Example 2: IgG conversion and expression The 13 purified hits from Example 1 above were then converted to human IgG1 antibodies for detailed biophysical and functional characterization (Table 3). The heavy and light chains of Fab hits B15709, B15716, B15722, B15732, B15740, B15744, B15756, B15700, B15711, B15717, B15735, B15736, and B16083 were cloned separately into the mammalian expression vector pTT5-SPB. The heavy and light chains of the reference antibodies were also cloned into pTT5-SPB. TIFF0007678841000019.tif104170

[0212] Pairs of plasmids encoding the heavy and light chains of the antibodies were transiently transfected into 293F cells according to the manufacturer's protocol. Supernatants from cells transfected with plasmids encoding antibodies TY21585, TY21586, TY21587, TY21588, TY21589, TY21580, or TY21591 were harvested and clarified by centrifugation and filtration, and the resulting IgG was purified using standard protein A affinity chromatography (MabSelect SuRe, GE Healthcare). Proteins were eluted, neutralized, and buffer exchanged into 20 mM PB buffer (20 mM NaH2PO4, 150 mM NaCl, pH 7.0). Protein concentrations were determined by UV spectrophotometry, and IgG purity was analyzed by SDS-PAGE or SEC-HPLC under denaturing, reducing, and non-reducing conditions.

[0213] Supernatants from cells transfected with plasmids encoding antibodies TY21687, TY21689, TY21680, TY21691, or TY21692 were harvested and clarified by centrifugation and filtration, and the resulting IgG was purified using standard protein A affinity chromatography (MabSelect SuRe, GE Healthcare). Proteins were eluted, neutralized, and buffer exchanged into 20 mM histidine buffer (20 mM histidine, 3.5 mL of 6 M HCl, pH 5.5). Protein concentrations were determined by UV spectrophotometry, and IgG purity was analyzed by SDS-PAGE or SEC-HPLC under denaturing, reducing, and non-reducing conditions.

[0214] Example 3: In vitro functional characterization of IgG-converting antibodies The binding affinity and kinetics of antibodies to human, monkey, and mouse CTLA4 were investigated by surface plasmon resonance (SPR) analysis using a Biacore™ T200 instrument (Biacore AB, Uppsala, Sweden) according to the manufacturer's guidelines (Table 4). Anti-human IgG (Fc) antibodies from a human antibody capture kit (GE BR-1008-39) were immobilized on a CM5 chip by coupling their amine groups to the carboxylated surface of the sensor chip according to the instructions of the amine coupling kit (GE Biacore #BR-1000-50). The immobilized anti-human IgG (Fc) antibodies were used to capture antibodies TY21585, TY21586, TY21580, TY21591, TY21687, TY21689, TY21680, TY21691, TY21692, and TAC2114. TAC2114 has the same amino acid sequence as the commercially available antibody ipilimumab. Binding was measured at six different concentrations (3.13, 6.25, 12.5, 25, 50, and 100 nM diluted in running buffer) using a flow rate of 30 μI / min. The running buffer used was HBS-EP (100 mM HEPES, 1.5 M sodium chloride, 0.05% surfactant P20, pH 7.6). Association and dissociation curves were fitted to a 1:1 Langmuir binding model using Biacore T200 Evaluation Software (Biacore AB) according to the manufacturer's guidelines. As shown in Table 4 below, all tested antibodies were able to bind to human and monkey CTLA4, and all antibodies except TY21591, TY21689, and TAC2114 were also able to bind to mouse CTLA4. TIFF0007678841000020.tif157170

[0215] Next, the ability of specific IgG antibodies to bind soluble human (Figure 1A, Table 5A) or canine (Figure 1B, Table 5B) CTLA4 was tested. 1 μg / mL of human CTLA4 fused to a human Fc fragment or canine CTLA4 fused to a His tag was prepared and used to coat ELISA plates overnight at 2-8 °C. After blocking, 100 μL of serially diluted IgG antibodies were added and incubated at 37 °C for 1 h. The plates were washed four times and then incubated with HRP anti-human IgG (Fab specific) (1:6000 dilution) for 1 h at 37 °C. Again, the plates were washed four times and incubated with TMB substrate for 15 min at room temperature. After stopping the reaction, the absorbance at 450 nm was measured. The data were analyzed by Graphpad Prism 6 with nonlinear fitting. As shown in Figures 1A-B and Tables 5A-B, all of the antibodies tested bound to human CTLA4 and, with the exception of antibodies TY21586 and TAC2114, also bound to canine CTLA4. Interestingly, TY21580 bound with the highest affinity to both human and canine CTLA4, with a K D were 0.27 and 0.49, respectively. TIFF0007678841000021.tif97170TIFF0007678841000022.tif102170

[0216] The affinity of the antibodies was also assessed against human and mouse CTLA4 transiently expressed on the surface of HEK293F cells (Figure 2). Briefly, HEK293F cells were transfected with plasmids expressing full-length human, monkey, or mouse CTLA4 from a bicistronic IRES vector that also encodes EGFP, and transfected cells were identified using EGFP expression. After 48 hours, a suspension of mammalian cells (2 × 10 5 / well) into an Eppendorf tube, centrifuge, discard the supernatant, and resuspend the cells in 1 mL of PBSA (at a density of 4 × 10 6The cells were resuspended in 1000 mM NaCl (100 mM NaCl, 0.1 mM NaCl, 0.1 mM NaCl, 0.0 ... TY21580 bound to cell surface expressed human and mouse CTLA4 with low nM affinity, whereas antibodies TY21585 and TY21586 bound to cell surface expressed human CTLA4 with high nM affinity.

[0217] The binding affinity and kinetics of antibodies TY21580, TY21687, TY21680, and TY21691 against rat CTLA4 protein were also tested using a ForteBio red 96 instrument (Pall, USA). Biotinylated rat CTLA4 protein fused with human FC was immobilized using an SA sensor (Pall, 185019), and then the sensor was contacted with IgG-converted hits at a concentration of 15 μg / mL (diluted in KB buffer, which is PBS buffer supplemented with 0.02% Tween 20 and 0.1% BSA) for 300 seconds, and then dissociated in KB buffer for 300 seconds. Association and dissociation curves were fitted to a 1:1 Langmuir binding model using ForteBio Data Analysis 7.1 (Pall, USA) according to the manufacturer's guidelines. As shown in Table 6 below, all tested antibodies were able to bind to rat CTLA4. TIFF0007678841000023.tif40170

[0218] IgG binding to activated T cells Next, the ability of IgG to bind to activated human, monkey, and mouse T cells was tested. Human PBMCs were freshly isolated from the blood of a healthy donor (#106) by density gradient centrifugation using Histopaque-1077 (Sigma). Human T cells were isolated from PBMCs using a human T cell enrichment kit (StemCell Technologies) and subsequently stimulated with anti-CD3 and anti-CD28 antibodies. Briefly, anti-CD3 antibody (clone: ​​OKT3, BioLegend) was plated at 0.2 μg per well in 200 μL on a 96-well plate overnight at 4°C. After washing, T cells were suspended in RPMI-1640 containing 10% FBS and 1% Penn / Strep and added to the plate. 5×10E5 T cells in 200 μL were added to each well of the 96-well plate. Then, 1 μL of anti-human CD28 antibody (clone: ​​28.2, BD) was added to a final concentration of 5 μg / mL. T cells were incubated for 96 hours, and then the binding of TY21580 to T cells was determined by flow cytometric analysis (Figure 3). T cells were stained with APC-labeled TY21580 or human IgG1 (isotype control) for 2 hours at 37°C. After washing, cells were analyzed on a CytoFLEX flow cytometer (Beckman Coulter) and data were analyzed with FlowJo software. As shown in Figure 3, TY21580 bound to activated CD4+ and CD8+ human T cells, whereas the control IgG showed no binding. Furthermore, APC-TY21580 showed no binding to resting T cells (data not shown).

[0219] Monkey PBMCs were freshly isolated from naive cynomolgus blood by density gradient centrifugation using Histopaque-1077 (Sigma). Monkey T cells were isolated from PBMCs using a pan T cell isolation kit non-human primate (Miltenyi Biotec) and subsequently stimulated with anti-CD3 and anti-CD28 antibodies. Briefly, anti-CD3 antibody (clone: ​​SP34, BD) was plated at 0.2 μg per well in 200 μL on a 96-well plate overnight at 4° C. After washing, T cells were suspended in RPMI-1640 containing 10% FBS and 1% Penn / Strep and added to the plate. 2×10E5 T cells in 200 μL were added to each well of the 96-well plate. Then, 1 μL of anti-human CD28 antibody (clone: ​​28.2, BD) was added to a final concentration of 5 μg / mL. T cells were incubated for 72 hours and binding of TY21580 to T cells was determined by flow cytometric analysis (Figure 3). T cells were stained with APC-labeled TY21580 or human IgG1 (isotype control) for 2 hours at 37°C. After washing, cells were analyzed on a CytoFLEX flow cytometer (Beckman Coulter) and data were analyzed with FlowJo software. As shown in Figure 3, TY21580 bound to activated CD4+ and CD8+ monkey T cells, whereas control IgG showed no binding. Furthermore, APC-TY21580 showed no binding to resting T cells (data not shown).

[0220] Mouse T cells isolated from the spleens of adult BALB / c mice were used to induce CTLA-4 expression. Splenocytes from the spleens of fresh mice were used to isolate T cells using the EasySep™ Mouse T Cell Isolation Kit (StemCell Technologies), followed by stimulation with anti-mouse CD3 and anti-CD28 antibodies. Briefly, anti-mouse CD3ε antibody (BioLegend) was coated overnight at 4°C at 0.2 μg per well in 200 μL in a 96-well plate. After washing, mouse T cells were suspended in RPMI-1640 containing 10% FBS and 1% Penn / Strep, and added to each well of the plate at 5×10E5 T cells in 200 μL. Then, 1 μL of anti-mouse CD28 antibody (eBioscience) was added to a final concentration of 5 μg / mL. Mouse T cells were incubated for 72 hours, and then binding of TY21580 to T cells was determined by flow cytometry analysis (Figure 3). T cells were stained with APC-labeled TY21580 or human IgG1 (isotype control) for 2 hours at 37°C. After washing, cells were analyzed on a CytoFLEX flow cytometer (Beckman Coulter) and data were analyzed with FlowJo software. As shown in Figure 3, TY21580 bound to activated mouse CD4+ and CD8+ T cells, whereas control IgG showed no binding.

[0221] Binding selectivity of antibodies against human CTLA4 Next, antibody selectivity was investigated. Human CTLA4, PD1, LAG3, Tim3, B7H3, CD95, TNFR1, OX40, CD40, PD-L1, BLTA, VISTA, PDL2, ICOS, and B7H4 were transiently overexpressed on the surface of HEK293F cells. Transfected cells were washed in pre-chilled 1x PBSA buffer (1.76 mM KH2PO4, 10.14 mM Na2HPO4·12H2O, 2.68 mM KCl, 136.89 mM NaCl, and 1% BSA) and then incubated with 100 nM of test antibody on ice for 1 h. Cells were washed once with staining buffer and Alexa Fluor® 647-conjugated mouse anti-human FC antibody was added and incubated for 30 min on ice protected from light. Samples were washed once with staining buffer before analysis by flow cytometry. TY21585 TY21586, TY21580, TY21687, TY21689, TY21680, and TY21691 were tested with human CTLA4, PD1, LAG3, Tim3, and B7-H3 (Figure 4A), TY21585 TY21586, TY21580 were further tested with human CD95, TNFR1, OX40, and CD40 (Figure 4B), and TY21586, TY21580 were further tested with human PD-L1, BLTA, VISTA, PDL2, ICOS, and B7-H4 (Figure 4C). As shown in Figures 4A-C, all tested antibodies bound specifically to human CTLA4 and did not bind to any of the other tested antigens (or parental cells transfected with empty vector).

[0222] Ligand competitive binding by ELISA The antibodies were then tested by ELISA for their ability to block the binding of CTLA4 to its cognate ligands CD80 and CD86. Recombinant human CTLA4 (fused with human Fc and His tags) was diluted to 1 μg / mL in carbonate buffer at pH 9.4 and coated on Maxisorp plates overnight at 4°C. The plates were blocked with PBS supplemented with 2% (w / v) nonfat milk for 1 h at 37°C. After washing, 50 uL of biotinylated CD80 (4 μg / mL) and 50 uL of various concentrations of test antibodies (2-fold serial dilutions ranging from 200 μg / mL to 1.56 μg / mL) were added sequentially to each well and incubated for 1 h at 37°C. The plates were washed four times and 100 μL of HRP-neutravidin (1:1000) was added to each well and incubated for 1 h at 37°C. Plates were washed as before, 50 μL of TMB substrate solution was added, and after 5 min incubation at room temperature, the reaction was stopped with 50 μL of sulfuric acid (2 M). As shown in Figure 5A-B, all antibodies tested, except TY21589, blocked the binding of CTLA4 to CD80.

[0223] Recombinant human CD86 fused to human Fc was diluted to 1 μg / mL in carbonate buffer, pH 9.4, and coated on Maxisorp plates overnight at 4°C. Plates were blocked with PBS supplemented with 2% (w / v) nonfat milk at 37°C for 1 h. After washing, 50 uL of biotinylated human CTLA4 fused to human Fc and His-tag (2.8 μg / mL) and 50 uL of various concentrations of test antibodies (2-fold serial dilutions ranging from 100 μg / mL to 0.78 μg / mL) were added consecutively to each well and incubated at 37°C for 1 h. Plates were washed 4 times and 100 μL of HRP-neutravidin (1:1000) was added to each well and incubated at 37°C for 1 h. Plates were washed as before, and 50 μL of TMB substrate solution was added and incubated at room temperature for 5 min, after which the reaction was stopped with 50 μL of sulfuric acid (2 M). As shown in Figure 5C-D, all tested antibodies blocked the binding of CTLA4 to CD86.

[0224] Competitive ligand binding by flow cytometry Antibodies were also tested by flow cytometry for their ability to block the binding of CTLA4 to its cognate ligands CD80 and CD86. A plasmid encoding full-length human CTLA4 was transiently expressed in HEK293F cells. Cells were washed with staining buffer (PBSA buffer containing 1.76 mM KH2PO4, 10.14 mM Na2HPO4·12H2O, 2.68 mM KCl, 136.89 mM NaCl, and 1% BSA) and resuspended in staining buffer containing 100 nM of test antibody. After incubation on ice for 60 min, 100 nM of biotinylated human CD80-Fc-Bio or CD86-Fc-Bio was added to each well and incubated for an additional hour on ice. The cells were washed once with staining buffer, and 100 μL of staining buffer containing Alexa Fluor 633-conjugated streptavidin was added and incubated on ice for 30 minutes protected from light. The cells were washed once and analyzed by CytoFlex flow cytometry. As shown in Figure 6A, all tested antibodies blocked the binding of CTLA4 to CD80 in a concentration-dependent manner. TY21588 showed the strongest blocking function, followed by TY21580 and TAC2114 showing significant blocking, and TY21585, TY21587, TY21589, and TY21591 showing lower blocking effects. TY21589 showed little or no blocking. As shown in Figure 6B, all tested antibodies blocked the binding of CTLA4 to CD86 in a concentration-dependent manner. TY21588, TY21589, TY21580, TY21591, and TAC2114 exhibited the most potent blocking function, while TY21585 and TY21587 exhibited a weaker blocking effect.

[0225] Binding to FcγR Next, the binding affinity of TY21586, TY21580, and TAC2114 to CD16a(176Phe) (Sino Biological Inc, 10389-H08H), CD16a(176Val, 10389-H08H1), CD32a (Sino Biological Inc, 10374-H08H), CD32b (Sino Biological Inc, 10259-H08H), and CD64 (Sino Biological Inc, 10256-H08H) was tested. Protein binding was investigated by surface plasmon resonance (SPR) analysis using a Biacore™ T200 instrument (Biacore AB, Uppsala, Sweden) according to the manufacturer's guidelines. Protein L (Sino Biological Inc. 11044-H07E) was immobilized on a CM5 chip by coupling its amine groups to the carboxylated surface of the sensor chip according to the instructions of the amine coupling kit (GE Biacore #BR-1000-50). Immobilized anti-human IgG (Fc) antibody was used to capture TY21586, TY21580, and TAC2114. Stepwise concentrations of FcγR proteins (12.5, 25, 50, 25, 100, and 200 nM) diluted in running buffer were injected at a flow rate of 30 μI / min. The running buffer used was HBS-EP (100 mM HEPES, 1.5 M sodium chloride, 0.05% surfactant P20, pH 7.6). Association and dissociation curves were fitted to a 1:1 Langmuir binding model using Biacore T200 Evaluation Software (Biacore AB, Uppsala, Sweden) according to the manufacturer's guidelines. As shown in Table 7 below, TY21586 and TY21580 showed similar affinities for binding to FcγR compared to the reference antibody (TAC2114). TIFF0007678841000024.tif64170

[0226] Binding to FcRn The binding affinity of the test antibodies to recombinant human FcRn was investigated by surface plasmon resonance (SPR) analysis using a Biacore™ T200 instrument (Biacore AB, Uppsala, Sweden) according to the manufacturer's guidelines. Human FcRn protein (Sino Biological Inc. 11044-H07E) was immobilized on a CM5 chip by coupling its amine groups to the carboxylated surface of the sensor chip according to the instructions of the amine coupling kit (GE Biacore #BR-1000-50). 100 nM of each antibody was diluted in running buffer (50 mM NaPO4, 150 mM NaCl, and 0.05% (v / v) surfactant 20, pH 6.0) and samples were injected for 120 s at a flow rate of 30 μI / min. As shown in Figure 7, antibodies TY21585, TY21580, TY21591, TY21687, and TY21691 showed higher % binding to FcRn than TAC2114, indicating that the IgG-FcRn complex on the Biacore chip may undergo conformational changes that stabilize the complex compared to the reference antibody (TAC2114). Antibodies TY21586, TY21587, TY21589, TY21689, and TY21680 showed lower % binding.

[0227] Human PBMC activation Preliminary studies showed that TY21580 did not stimulate the activation or proliferation of human T cells. Because CTLA4 activity in T cells is related to a first signal (TCR / CD3) and a second signal involving B7-CD28 / CTLA-4, human PBMCs were selected to determine the activity of TY21580 in the presence of low concentrations of anti-CD3. Anti-CD3 antibody (OKT-3) was coated on 96-well plates overnight at 4°C. After washing, 1 × 10 5Freshly isolated human PBMCs were added to each well, followed by the addition of test articles at different concentrations. Induction of IL-2 was measured 48 hours after stimulation using a human IL-2 ELISA Ready-SET-Go (Invitrogen) kit. IFNγ in the supernatants was measured using a human IFNγ ELISA Ready-SET-Go (Invitrogen) kit. As shown in Figures 8A and 9, antibody TY21580 significantly increased human PBMC activation in the presence of anti-CD3, whereas TY21580 alone had no activity.

[0228] Dendritic cell MLR assay DC-MLR assays were performed using monocyte-derived DCs and CD4+ T lymphocytes in three donor pairs: D42 / D109, D32 / D104, and D104 / D42 (Figure 10). To obtain DC cells, PBMCs were isolated by density gradient centrifugation from healthy donors, and CD14+ monocytes were purified from PBMCs using a positive selection commercial kit (StemCell). CD14+ monocytes were skewed to DCs by in vitro culture for 6 days in RPMI-1640 supplemented with 10% heat-inactivated FBS, 1% penicillin / streptomycin, 20 ng / mL rhGM-CSF, and 20 ng / mL rhIL-4. The culture medium was replaced with fresh medium on day 3. DC maturation was induced on day 6 for 24 h in RPMI-1640 medium supplemented with 10% heat-inactivated FBS, 1% penicillin / streptomycin, and 50 ng / mL rhTNF-α. CD4+ T cells were purified by negative isolation from another healthy donor. Test articles were titrated to the corresponding concentrations (as shown in Figure 10). Harvested DCs (1 × 10 4 ) with or without titrated test product, allogeneic CD4+ T cells (1 × 10 5) were co-cultured with human CD4+ T cells and DCs. Anti-PD1 antibody was used as a positive control for the DC-MLR assay. Five days after co-culture, IFNγ was measured in the supernatants by ELISA using the Human IFNγ Ready-SET-Go ELISA kit. As shown in Figure 10, antibody TY21580 showed weak activity in the DC-MLR assay using human CD4+ T cells and DCs.

[0229] ADCC activity of antibody TY21580 HEK293F cells overexpressing human CTLA-4 were used as target cells to evaluate TY21580-mediated ADCC activity. Human NK cells were freshly isolated from human PBMCs using a human NK isolation kit (StemCell). 1 × 10 5 NK cells and 1 x 10 4 HEK293F / hCTLA-4 cells (E:T ratio 10:1) were mixed with different concentrations of antibodies. After 4 hours of incubation, LDH was measured to determine ADCC activity. % lysis was then calculated using the following formula: % lysis = [(experimental release)-mean(target+NK)] / [mean(target max)-mean(target alone)] x 100%. As shown in Figure 11A-B, TY21580 showed stronger ADCC activity than the reference antibody (TAC2114). The isotype control did not show any ADCC activity.

[0230] ADCC activity was also evaluated using human Treg cells (A, donor #96; B, donor #12) and NK cells (A, donor #99; B, donor #05). To obtain human Treg cells, human PBMCs were freshly isolated from a healthy donor and Treg cells were negatively selected using the EASYSEP™ Human Regulatory T Cell Enrichment Kit (StemCell Technologies). The enriched human Treg cells were further expanded by CD3 / CD28 stimulation in the presence of IL-2 and confirmed by CD25 and FOXP3 staining and FACS analysis. To obtain human NK cells, human PBMCs were freshly isolated from another healthy donor and NK cells were isolated using the Human NK Isolation Kit (StemCell Technologies). Human Treg cells were labeled with 10 μM Calcein AM (Invitrogen) for 30 min at 37°C. After washing three times, the labeled Treg cells were mixed with different concentrations of the test products, followed by the addition of NK cells. 1 × 10 5 NK cells and 1 x 10 4 Labeled human Treg cells were added to wells of a 96-well plate and mixed to give an E:T ratio of 10:1. After 4 hours of incubation, Calcein AM concentrations in the supernatants were measured and ADCC activity was determined using the following formula: % lysis = [(experimental release) - mean (target + NK)] / [mean (target max) - mean (target alone)] x 100%. As shown in Figures 12A-B, antibody TY21580 showed stronger ADCC activity than the reference antibody (TAC2114). The isotype control showed no ADCC activity.

[0231] CDC activity of TY21580 HEK293F cells overexpressing human CTLA-4 were labeled with 10 μM calcein AM (Invitrogen) for 30 min at 37°C. Different concentrations of antibodies were added to wells of a 96-well plate at 1 × 10 4 The labeled cells were mixed with 5% normal human serum complement (NHSC, Quidel). After 5 hours of incubation, calcein AM was measured in the supernatant to determine CDC activity (Figure 13).

[0232] Human PBMCs were freshly isolated from a healthy donor (donor #57). CD4+ T cells were isolated using the EasySep Human CD4+ T Cell Enrichment Kit (StemCell) and stimulated with PMA (50 ng / mL) + ionomycin (1 μM) for 20 h to induce CTLA-4 expression on the cell surface. Activated human CD4+ T cells were then labeled with 10 μM calcein AM (Invitrogen) for 30 min at 37 °C. Different concentrations of antibodies were added to wells of a 96-well plate at 1 × 10 4 The cells were mixed with 1000 labeled human CD4+ T cells and 5% normal human serum complement (NHSC, Quidel). After 5 h of incubation, calcein AM was measured in the supernatant to determine CDC activity (Figure 14). TY21580 did not show CDC activity on HEK293F / hCTLA-4 cells or activated human T cells.

[0233] Taken together, these results indicate that the antibodies described herein can bind human CTLA4 with high affinity and specificity, and that such antibodies effectively blocked the interaction of CTLA4 with its cognate ligands CD86 and CD80. The antibodies were also shown to be cross-reactive with CTLA4 from multiple species. Furthermore, binding to CTLA4 can regulate T cell activation and induce ADCC activity against CTLA4-expressing cells, such as Tregs.

[0234] Example 4: In vivo characterization of IgG-converting antibodies As described in the Examples above, the species cross-reactivity (human and mouse) of the antibodies allowed for the determination of the anti-tumor efficacy of the antibodies in multiple syngeneic tumor models, including MC38 and CT26 colorectal tumor models, H22 liver tumor model, PAN02 pancreatic tumor model, and 3LL lung tumor model.

[0235] Antitumor effects in MC38 colorectal tumor model C57BL / 6 mice (n = 8 per group, female, 6-8 weeks old) were subcutaneously inoculated with MC38 (NTCC-MC38) mouse colon cancer cells. When tumors were established (80 mm 3), treatment was initiated with an isotype control antibody and three different doses of antibody TY21580 by intraperitoneal injection twice weekly for three weeks. Tumor growth was monitored twice weekly and reported as the mean tumor volume ± sem over time (Figure 15A-C). As shown in Figure 15A, compared to the isotype control antibody, TY21580 demonstrated potent in vivo antitumor activity, with tumors completely regressing at all three doses. As shown in Figure 15B, by 60 days post-treatment, 8 of 8 mice in the 10 mg / kg TY21580 group, 7 / 8 in the 2.5 mg / kg TY21580 group, and 6 / 8 in the 0.5 mg / kg TY21580 group remained tumor-free. As shown in Figure 15C, long-lasting immune memory against MC38 tumor cells was demonstrated when mice in the 10 mg / kg TY21580 group were rechallenged.

[0236] Antitumor effects in CT26 colorectal tumor model BALB / c mice (n = 8 per group, female, 7-8 weeks old) were subcutaneously inoculated with CT26 (Shanghai Institutes for Biological Sciences) mouse colon cancer cells. When tumors were established (70 mm 3 ), treatment was initiated with an isotype control antibody and two different doses of antibody TY21580 by intraperitoneal injection twice weekly. Tumor growth was monitored twice weekly and reported as mean tumor volume ± sem over time. As shown in Figure 16, compared to the isotype control antibody, TY21580 demonstrated potent in vivo antitumor activity with nearly 100% inhibition at doses as low as 0.1-1 mg / kg.

[0237] Antitumor effect in H22 liver tumor model BALB / c mice (n = 5 per group, female, 7-8 weeks old) were subcutaneously inoculated with H22 (China Center for Type Culture Collection) mouse hepatoma cells. When tumors were established (60 mm 3), treatment was initiated twice weekly by intraperitoneal injection with an isotype control antibody, three different doses of antibody TY21586 (0.1 mg / kg, 1 mg / kg, 5 mg / kg), and two different doses of antibody TY21580 (0.1 mg / kg, 1 mg / kg). Tumor growth was monitored twice weekly and reported as the mean tumor volume ± sem over time. As shown in Figure 17, compared to the isotype control antibody, both TY21580 and TY21586 exhibited potent in vivo antitumor activity in a dose-dependent manner. When compared at the same dose, TY21580 was more potent than TY21586 in this tumor model. Furthermore, administration of TY21580 at 1 mg / kg resulted in tumor regression.

[0238] Antitumor effect in Lewis lung tumor model C57BL / 6 mice (n = 6 per group, female, 8 weeks old) were subcutaneously inoculated with Lewis (JenNio Bio, Guandong, China) mouse lung cancer cells. When tumors were established (70 mm 3 ), treatment was initiated with isotype control antibody or antibodies TY21580, TY21687, TY21680, or TY21691, all at a dose of 5 mg / kg, by intraperitoneal injection twice weekly. Tumor growth was monitored twice weekly and reported as the mean tumor volume ± sem over time. As shown in Figure 18, compared to the isotype control antibody, antibodies TY21580, TY21687, and TY21680 showed significant inhibition of tumor growth, whereas antibody TY21691 did not show potent antitumor activity.

[0239] Antitumor effect in PAN02 pancreatic tumor model C57BL / 6 mice (n=8 per group, female, 6 weeks old) were subcutaneously inoculated with PAN-02 (CAMS Cell Culture Center) mouse pancreatic cancer cells. When tumors were established (85 mm 3), treatment was initiated with an isotype control antibody or antibody TY21580 at three different doses (0.5 mg / kg, 2 mg / kg, 0.5 mg / kg) by intraperitoneal injection twice weekly. Tumor growth was monitored twice weekly and reported as mean tumor volume ± sem over time. As shown in Figure 19, compared to the isotype control antibody, TY21580 demonstrated potent antitumor activity in a dose-dependent manner.

[0240] Antitumor effects of antibody TY21580 alone or in combination with anti-CD137 antibody in 3LL lung tumor model C57BL / 6 mice (n = 10 per group, female, 6-8 weeks old) were subcutaneously inoculated with 3LL (JCRB) mouse lung cancer cells. When tumors were established (75 mm 3 ), treatment was initiated with isotype control antibody, TY21580 (10 mg / kg), anti-CD137 (10 mg / kg), or a combination of TY21580 and anti-CD137, by intraperitoneal injection twice weekly. Anti-CD137 is a proprietary monoclonal antibody developed that possesses the ability to bind to both human and mouse CD137 (see PCT Application No. PCT / CN2017 / 098332, incorporated herein by reference in its entirety). Tumor growth was monitored twice weekly and reported as the mean tumor volume ± sem over time. As shown in Figures 20A-B, compared to the isotype control antibody, both TY21580 and anti-CD137 demonstrated potent anti-tumor activity, with the combination inhibiting tumor growth more than either monotherapy.

[0241] Rechallenge study of mice with complete responses to TY21580 BALB / c mice (n = 8 per group, female, 7-8 weeks old) were subcutaneously inoculated with H22 (China Center for Type Culture Collection) mouse hepatoma cells. When tumors were established (60 mm 3), treatment was initiated with either an isotype control antibody or antibody TY21580 at two different doses (1 mg / kg, 10 mg / kg) by intraperitoneal injection twice a week for three weeks. Tumor growth was monitored twice a week and reported as the mean tumor volume ± sem over time. Compared to the isotype control antibody, TY21580 at both doses resulted in complete tumor regression several days after the last dose, and mice remained tumor-free for 60 days after treatment. Mice in the 10 mg / kg TY21580 treatment group were then rechallenged subcutaneously with H22 tumor cells on the opposite flank on day 60, and tumor growth was monitored. As shown in Figure 21, these mice remained tumor-free after rechallenging with the same tumor cells, suggesting that a specific antitumor memory had developed in these mice. A rechallenge control group was set up simultaneously with untreated mice inoculated with the same number of H22 tumor cells, and their tumors grew rapidly.

[0242] Antibody Pharmacokinetics Pharmacokinetic studies of antibodies TY21585, TY21586, TY21580 and TY21591 were performed in female BALB / c mice (approximately 8 weeks old). Three mice per group were injected intravenously with test antibodies at 10 mg / kg via tail vein injection. Blood samples (approximately 20 μL per sample) were collected at 1, 8, 48, 168, 336 and 500 hours after dosing. Blank control blood was collected from three naive female mice that did not receive antibody. Serum concentrations of each test antibody were determined by ELISA, using CTLA4-His-Fc for capture and HRP-labeled anti-human IgG (Fab specific) antibody (Sigma) for detection. As shown in FIG. 22, TY21586 exhibited comparable pharmacokinetics to TAC2114 in mice, whereas TY21585, TY21580, and TY21591 were cleared much more rapidly.

[0243] Pharmacokinetic studies of TY21586 and TY21580 were also performed in naive cynomolgus monkeys. Each antibody was administered by intravenous bolus injection at 10 mg / kg to one female and one male monkey. Serum samples were collected pre-dose (0 hours) and at 0.25, 1, 8, 24, 72, 120, 168, 240, 336, 504, and 672 hours after dosing. Serum concentrations of TY21586 and TY21580 were determined by ELISA, using CTLA4-His-Fc for capture and HRP-labeled anti-human IgG (Fab specific) antibody (Sigma) for detection. As shown in Figures 23 and 24, compared to TY21586, TY21580 was cleared much more rapidly in monkeys, potentially due to the rapid increase in anti-drug antibodies observed in these animals.

[0244] Repeated dose toxicity study Repeated dose toxicity of TY21580 was performed in normal BALB / c mice. Vehicle control or antibody TY21580 (at 25 mg / kg or 50 mg / kg) was administered intraperitoneally (10 mL / kg) on ​​days 1, 4, 7, and 11. Five female and five male mice (5 weeks old) were included in each group. Mice were monitored daily for abnormal behavior and symptoms, and food intake and body weight were measured daily. On day 14, animals were euthanized for post-mortem examination and other analyses. Blood was collected from each animal, and up to six blood samples (three males, three females) per group were collected for hematology (RBC, platelets, WBC, WBC differential) and / or blood biochemistry (ALT, AST, GLB, ALP, and LDH, etc.) analyses. The following organs were harvested and weighed from each mouse: heart, lungs, thymus, liver, spleen, kidneys, testes, and ovaries. Liver samples from six animals (three males, three females) per group were fixed in FFPE. FFPE blocks for liver tissue were prepared, sectioned, and stained with H&E for histopathological analysis.

[0245] No abnormal behavior was observed during the entire survival period of the study, and there were no unscheduled animal deaths. Compared to vehicle treatment, TY21580 did not affect the food intake and body weight of the animals. Postmortem examination also did not reveal any obvious lesions in the treated mice at both dose levels, except for increased spleen weight in the TY21580-treated group (Figure 25A-B). Blood analysis did not show any significant changes as shown by the blood biochemistry parameters tested in the mice treated with TY21580. No obvious abnormalities were found in the histopathological sections of the liver from the mice (Figure 26). Overall, TY21580 was well tolerated in this study, and no significant toxicity was observed in the mice.

[0246] Taken together, these results demonstrate that the CTLA4 antibodies described herein are highly safe in mice, have potent antitumor activity, and can induce long-lasting immune memory against tumor cells.

[0247] Example 5: Antibody Developability Profile For developability evaluation, purified TY21586 and TY21580 were exchanged into storage buffer (20 mM histidine, pH 5.5). All experiments, including solubility, stability under accelerated stress conditions, and differential scanning fluorescence (DSF) studies, were carried out in storage buffer. A TSKgel column (Tosoh Bioscience G3000SWxl) was used for all SEC-HPLC analyses.

[0248] Antibody solubility Samples containing antibody TY21586 or TY21580 were formulated in storage buffer at concentrations greater than 100 mg / mL and tested for the amount of high molecular weight (HMW) protein aggregates (Table 8). The antibodies were then adjusted to approximately 12 mg / mL in storage buffer. The samples (12 μg each) were then assayed by SEC-HPLC for detection of high molecular weight protein aggregates. As shown in FIG. 27, no significant increase in HMW aggregates was observed for antibodies formulated at high concentrations (greater than 100 mg / mL) for 30 minutes. TIFF0007678841000025.tif28170

[0249] Antibody stability under accelerated stress conditions Antibody stability under accelerated stress conditions was also investigated. The results of these experiments are summarized in Table 9 and Figure 28. TY21586 and TY21580 remained stable after six cycles of freezing (-80°C) and thawing (room temperature). After 7 days at 50°C, there was little change in HMW aggregates or low molecular weight (LMW) fragments. In long-term time course experiments (up to 28 days at 40°C), TY21586 and TY21580 remained stable with no significant increase in HMW aggregates or LMW fragments. TIFF0007678841000026.tif63170

[0250] Furthermore, thermal stability, as measured by differential scanning fluorescence (DSF), indicated that both TY21586 and TY21580 were stable up to at least about 55° C. The transition midpoints (Tm), the characteristic temperatures at which the unfolding transition occurs in almost all protein domains, are shown in Table 10 below. TIFF0007678841000027.tif47170

[0251] Finally, the highest achievable concentrations of antibodies TY21586 and TY21580 were found to be greater than 197.8 mg / mL and 126.0 mg / mL, respectively, after centrifugation.

[0252] Taken together, these results indicate that even without formulation optimization, the CTLA4 antibodies TY21586 and TY21580 had excellent developability profiles.

[0253] Example 6: Methods for identifying autoblocking peptides of CTLA4 activatable antibodies derived from TY21580 Described herein is a new system that has been designed and implemented to efficiently discover masking moieties with good developability. In this system, the target antibody fragment, either Fab (Figure 29) or scFv (Figure 30), was first displayed on the yeast surface and confirmed to be functional in binding to its antigen. The improved peptide library was then directly fused to the N-terminus of the light chain of the CTLA4 antibody (TY21580) to construct a yeast library that displayed the fusion protein on the yeast surface. The yeast library was then subjected to several rounds of FACS-based screening. First, yeast clones that had low binding to the antigen were enriched, and then the enriched yeast clones were treated with protease to remove the N-terminal peptides and clones with high binding to the antigen were selected (Figures 29 and 30). After 4-5 rounds of selection, plasmids were extracted from these clones and the masking peptide sequences were confirmed by DNA sequencing.

[0254] Example 7: Design of Constrained Peptide Libraries (CPL) for CTLA4 Activatable Antibodies Four exemplary constrained peptide libraries (CPLs) were designed (Table 11). TIFF0007678841000028.tif90170 Each X is independently an amino acid selected from the group consisting of A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y, and each Z is independently an amino acid selected from the group consisting of D, A, Y, S, T, N, I, L, F, V, H, and P.

[0255] Their cores have the sequence Z6CX6CZ2 (SEQ ID NO: 137) or Z6CX8CZ2 (SEQ ID NO: 138), with two fixed cysteine ​​residues forming disulfide bonds to constrain the conformation of the peptide. In the synthesized oligonucleotides, the degenerate codon NHC was applied everywhere except inside the loop, and the NNK codon was also incorporated in CPL011 and CPL013. In contrast to the NNK or NNS codon, the NHC codon codes for 12 residues (Table 12), encompassing significant diversity, but lacking the chemically unstable residues methionine, tryptophan, and cysteine. Furthermore, the reduced theoretical diversity compared to the NNK or NNS codons allowed the construction of libraries with a wider coverage. TIFF0007678841000029.tif39170

[0256] Follo...

Claims

1. 1. An activatable antibody comprising a first polypeptide comprising, from N-terminus to C-terminus, a masking moiety (MM), a cleavable moiety (CM), and a target binding moiety (TBM), the MM comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 189-193, 195-196, and 213-216; The CM comprises at least a first cleavage site, and the first cleavage site is selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin B, cathepsin C, cathepsin D, cathepsin D, cathepsin D, cathepsin D, cathepsin B ... a protease cleavage site for a protease selected from the group consisting of caspase S, ADAM10, ADAM12, ADAMTS, caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE; (a) the TBM comprises an antibody light chain variable region (VL), and the activatable antibody further comprises a second polypeptide comprising an antibody heavy chain variable region (VH); (b) the TBM comprises an antibody heavy chain variable region (VH), and the activatable antibody further comprises a second polypeptide comprising an antibody light chain variable region (VL); (c) the TBM comprises, from N-terminus to C-terminus, an antibody light chain variable region (VL) and an antibody heavy chain variable region (VH); or (d) the TBM comprises, from N-terminus to C-terminus, an antibody heavy chain variable region (VH) and an antibody light chain variable region (VL); VH comprises HVR-H1 comprising the amino acid sequence YSISSGYHWSWI (SEQ ID NO:23), HVR-H2 comprising the amino acid sequence LARIDWDDDKYYSTSLKSRL (SEQ ID NO:35), and HVR-H3 comprising the amino acid sequence ARSYVYFDY (SEQ ID NO:45); The VL comprises an HVR-L1 comprising the amino acid sequence RASQSVRGRFLA (SEQ ID NO:58), an HVR-L2 comprising the amino acid sequence DASNRATGI (SEQ ID NO:66), and an HVR-L3 comprising the amino acid sequence YCQQSSSWPPT (SEQ ID NO:75); and When the CM is cleaved, the activatable antibody binds to human CTLA4 via VH and VL. Activatable antibodies.

2. The activatable antibody of claim 1 , wherein the TBM comprises an antibody light chain variable region (VL) and the activatable antibody further comprises a second polypeptide comprising an antibody heavy chain variable region (VH).

3. 2. The activatable antibody of claim 1, wherein the first cleavage site is a protease cleavage site for a protease selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-2 (MMP-2), MMP-9 and tobacco etch virus (TEV) protease.

4. The CM has a first linker (L １ 2. The activatable antibody of claim 1, further comprising:

5. Said L １ The activatable antibody of claim 4, wherein said antibody comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 156-163.

6. The CM further comprises a second cleavage site, the second cleavage site being selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin S, ADAM1, 2. The activatable antibody of claim 1, wherein the cleavage site is a protease cleavage site of a protease selected from the group consisting of caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE.

7. The CM has a first linker (L １ ) wherein the second cleavage site is １ The activatable antibody of claim 6 , wherein the C-terminus of

8. 7. The activatable antibody of claim 6, wherein the second cleavage site is a protease cleavage site for a protease selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-2 (MMP-2), MMP-9 and tobacco etch virus (TEV) protease.

9. The activatable antibody of claim 6 , wherein the first and second cleavage sites are different.

10. The CM has a second linker (L ２ 7. The activatable antibody of claim 6, further comprising:

11. Said L ２ The activatable antibody of claim 10, wherein said activatable antibody comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 156-163.

12. The CM has a linker (L ３ 2. The activatable antibody of claim 1, further comprising:

13. The CM comprises at least a first protease cleavage site and is selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin S, ADAM1, and the like.

2. The activatable antibody of claim 1, which is cleaved by one or more proteases selected from the group consisting of caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE.

14. The activatable antibody of claim 1, comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 165-179 and 198-202.

15. The activatable antibody of claim 1 , wherein the VH comprises the amino acid sequence of SEQ ID NO:87 and the VL comprises the amino acid sequence of SEQ ID NO:

100.

16. The activatable antibody of claim 1 , wherein the MM comprises the amino acid sequence PNPSSDCVPYYYACAY (SEQ ID NO: 144).

17. The activatable antibody of claim 15 , wherein the MM comprises the amino acid sequence PNPSSDCVPYYYACAY (SEQ ID NO: 144).

18. 2. The activatable antibody of claim 1, comprising the amino acid sequence EVGSYPNPSSDCVPYYYACAY (SEQ ID NO: 192).

19. 16. The activatable antibody of claim 15, comprising the amino acid sequence EVGSYPNPSSDCVPYYYACAY (SEQ ID NO: 192).

20. (a) a first polypeptide comprising, from N-terminus to C-terminus, a masking portion (MM), a cleavable portion (CM), and an antibody light chain variable region (VL); and (b) a second polypeptide comprising an antibody heavy chain variable region (VH).

1. An activatable antibody comprising: MM comprises the amino acid sequence PNPSSDCVPYYYACAY (SEQ ID NO: 144); The CM comprises at least a first cleavage site, and the first cleavage site is selected from the group consisting of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, tobacco etch virus (TEV) protease, plasmin, thrombin, factor X, PSA, PSMA, cathepsin D, cathepsin K, cathepsin B, cathepsin C, cathepsin D, cathepsin D, cathepsin D, cathepsin D, cathepsin B ... a protease cleavage site for a protease selected from the group consisting of caspase S, ADAM10, ADAM12, ADAMTS, caspase-1, caspase-2, caspase-3, caspase-4, caspase-5, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, caspase-11, caspase-12, caspase-13, caspase-14, and TACE; VH comprises the amino acid sequence of SEQ ID NO:87, and VL comprises the amino acid sequence of SEQ ID NO:100; and When the CM is cleaved, the activatable antibody binds to human CTLA4 via VH and VL. Activatable antibodies.

21. 21. The activatable antibody of claim 20, wherein the first polypeptide comprises the amino acid sequence EVGSYPNPSSDCVPYYYACAYSGRSAGGGGTPLGLAGSGGS (SEQ ID NO: 200).

22. 22. The activatable antibody of any one of claims 1 to 21, comprising a human IgG1 Fc region comprising one or more mutations that increase antibody-dependent cellular cytotoxicity (ADCC) activity.

23. A pharmaceutical composition comprising an activatable antibody according to any one of claims 1 to 22 and a pharma- ceutically acceptable carrier.

24. A medicament for treating or delaying the progression of cancer in a subject in need thereof, comprising an effective amount of an activatable antibody of any one of claims 1 to 22, or a pharmaceutical composition of claim 23.

25. 1. A medicament for reducing the size of a solid tumor in a subject in need thereof, comprising: The solid tumor is between about 400 and 1000 mm ３ and A medicament comprising an effective amount of an activatable antibody according to any one of claims 1 to 22, or a pharmaceutical composition according to claim 23.

26. further comprising an effective amount of at least one additional therapeutic agent; The pharmaceutical of claim 24 or 25, wherein the at least one additional therapeutic agent is selected from the group consisting of viral gene therapy, immune checkpoint inhibitors, targeted therapy, radiation therapy, vaccine therapy, and chemotherapy.

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