The invention relates generally to polypeptides that include a cleavable moiety that is a substrate for at least one protease selected from matriptase and u-plasminogen activator (uPA), to activatable antibodies and other larger molecules that include the cleavable moiety that is a substrate for at least one protease selected from matriptase and u-plasminogen activator, and to methods of making and using these polypeptides that include a cleavable moiety that is a substrate for at least one protease selected from matriptase and u-plasminogen activator in a variety of therapeutic, diagnostic and prophylactic indications.
