Antibodies that bind activatable antibodies and methods of use thereof

A method of detecting the presence or absence of an activatable antibody or conjugated activatable antibody in a subject or a sample, the method comprising:

• contacting a subject or a sample with an antibody or fragment thereof that binds an activatable antibody or conjugated activatable antibody;
• and
• determining the level of activatable antibody or conjugated activatable antibody in the subject or sample,
• wherein the antibody or fragment thereof comprises a combination of a VH CDR1 sequence, a VH CDR2 sequence, a VH CDR3 sequence, a VL CDR1 sequence, a VL CDR2 sequence, and a 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.