The invention relates generally to polypeptides that include at least a first cleavable moiety (CM1) that is a substrate for at least one matrix metalloprotease (MMP) and at least a second cleavable moiety (CM2) that is a substrate for at least one serine protease (SP), to activatable antibodies and other larger molecules that include these polypeptides that include at least a CM1 that is a substrate for at least one MMP protease and at least a CM2 that is a substrate for at least one SP protease, and to methods of making and using these polypeptides that include at least a CM1 that is a substrate for at least one MMP protease and at least a CM2 that is a substrate for at least one SP protease in a variety of therapeutic, diagnostic and prophylactic indications.
