Anti-B7-H4 Antibodies and Immunoconjugates

#The present invention relates to anti-B7-H4 antibodies and immunoconjugates and methods of using the same.

#B7-H4 is a Type I transmembrane protein and is a member of the B7 superfamily of proteins that provides co-signal in conjunction with a T-cell receptor antigenic signal. B7-H4 is a negative regulator of T-cell function and ligation of T-cells inhibits their growth, cytokine secretion and cytotoxicity. Elimination of B7-H4 in mice does not affect immune cell homeostasis and no signs of autoimmunity. Zhu et al., Blood, 113(8): 1759-1767 (2009); Suh et al., Molecular and Cellular Biology, 26(17): 6403-6411 (2006). The receptor for B7-H4 is unknown and unidentified.

#Human B7-H4 is a 282 amino acid protein (including the amino-terminal signal sequence), of which ˜227 amino acids are predicted to be in the extracellular space following cleavage of the amino-terminal signal sequence. B7-H4 comprises an Ig-like V-domain, an Ig-like C domain, a transmembrane domain and a short cytoplasmic tail.

#FIG. 1 shows a graphic representation of the levels of human B7-H4 gene expression in various tissues, as described in Example A.

#FIG. 2 shows expression of B7-H4 in breast carcinoma samples by in situ hybridization, as described in Example B.

#FIG. 3 shows (A) the prevalence of B7-H4 expression in all breast cancer subtypes, (B) the prevalence of 0, 1+, 2+, and 3+ levels of B7-H4 staining in breast cancer subtypes, (C) the overall expression of B7-H4 in breast tumors (by Western analysis), (D) the expression of B7-H4 in primary breast tumors (by Western analysis), (E) the expression of B7-H4 in ovarian tumors, as described in Example B.

#An “acceptor human framework” for the purposes herein is a framework comprising the amino acid sequence of a light chain variable domain (VL) framework or a heavy chain variable domain (VH) framework derived from a human immunoglobulin framework or a human consensus framework, as defined below. An acceptor human framework “derived from” a human immunoglobulin framework or a human consensus framework may comprise the same amino acid sequence thereof, or it may contain amino acid sequence changes. In some embodiments, the number of amino acid changes are 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less. In some embodiments, the VL acceptor human framework is identical in sequence to the VL human immunoglobulin framework sequence or human consensus framework sequence.

#“Affinity” refers to the strength of the sum total of noncovalent interactions between a single binding site of a molecule (e.g., an antibody) and its binding partner (e.g., an antigen). Unless indicated otherwise, as used herein, “binding affinity” refers to intrinsic binding affinity which reflects a 1:1 interaction between members of a binding pair (e.g., antibody and antigen). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (Kd). Affinity can be measured by common methods known in the art, including those described herein. Specific illustrative and exemplary embodiments for measuring binding affinity are described in the following.

#An “affinity matured” antibody refers to an antibody with one or more alterations in one or more hypervariable regions (HVRs), compared to a parent antibody which does not possess such alterations, such alterations resulting in an improvement in the affinity of the antibody for antigen.