Patent ID: 8518404

Claim:
An activatable binding polypeptide (ABP) that in an activated state binds Cytotoxic T-Lymphocyte Antigen 4 (CTLA 4), the ABP comprising, in an N- to C-terminal direction or in a C- to N-terminal direction: an antigen binding domain (ABD) that specifically binds to CTLA-4, a cleavable moiety (CM), and a masking moiety (MM), wherein the MM is a peptide that inhibits binding of the ABD to CTLA-4, wherein the MM comprises an amino acid sequence selected from the group consisting of MILLCAAGRTWVEACANGR (SEQ ID NO: 63), AERLCAWAGRFCGS (SEQ ID NO: 65), WADVMPGSGVLPWTS (SEQ ID NO: 67) and SDGRMGSLELCALWGRFCGS (SEQ ID NO: 69, and wherein the CM is positioned in the ABP such that in an uncleaved state the MM interferes with specific binding of the ABD to CTLA-4 and in a cleaved state the MM does not interfere with specific binding of the ABD to CTLA-4.