Activatable antibodies that bind epidermal growth factor receptor and methods of use thereof

An activatable antibody that in an activated state binds Epidermal Growth Factor Receptor (EGFR) comprising:

• an antibody or an antigen binding fragment thereof (AB) that specifically binds to EGFR, wherein the AB comprises:
• (i) a heavy chain amino acid sequence selected from the group consisting of SEQ ID NO:
• 2, SEQ ID NO:
• 34, and SEQ ID NO:
• 36, and
• (ii) a light chain amino acid sequence comprising the amino acid sequence of SEQ ID NO:
• 32;
• wherein the light chain amino acid sequence is coupled to a spacer sequence and a masking moiety (MM) via a cleavable moiety (CM) to produce a masked light chain, wherein the masked light chain comprises an amino acid sequence selected from the group consisting of SEQ ID NO:
• 4, SEQ ID NO:
• 6, SEQ ID NO:
• 8, SEQ ID NO:
• 10, and SEQ ID NO:
• 12, wherein the MM inhibits the binding of the AB of the activatable antibody in an uncleaved state to EGFR;
• wherein the CM is a polypeptide that functions as a substrate for a protease;
• and
• wherein the activatable antibody in the uncleaved state has the structural arrangement from N-terminus to C-terminus as follows:
• Spacer Sequence-MM-Linking Peptide 1 (LP1)-CM-Linking Peptide 2 (LP2)-AB or AB-LP2-CM-LP1-MM-Spacer Sequence.