Antibodies that bind activatable antibodies and methods of use thereof

An isolated antibody or fragment thereof that binds an activatable antibody or conjugated activatable antibody,

• wherein the antibody or fragment thereof comprises a combination of complementarity determining region (CDR) comprising a variable heavy chain complementarity determining region 1 (VH CDR1) sequence, a variable heavy chain complementarity determining region 2 (VH CDR2) sequence, a variable heavy chain complementarity determining region 3 (VH CDR2) sequence, a variable light chain complementarity determining region 1 (VL CDR1) sequence, a variable light chain complementarity determining region 2 (VL CDR2) sequence, and a variable light chain complementarity determining region 3 (VL CDR3) sequence,
• wherein the VH CDR1 sequence comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:
• 67, 73, 78, 88, 95, and 101;
• the VH CDR2 sequence comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:
• 68, 74, 79, 89, 96, and 102;
• the VH CDR3 sequence comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:
• 69, 80, 90, and 97;
• the VL CDR1 sequence comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:
• 70, 81, and 98;
• the VL CDR2 sequence comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:
• 71, 82, and 99;
• and the VL CDR3 sequence comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:
• 72, 83, 84, 91, 110, 100, and 103.