KLK6 and cancer: As mesotrypsin and KLK6 are thought to be involved in different cancer stages and various types of cancer, we believe that APPI‐3M, APPI‐4M, and their HSA fusion proteins can be used in all phases of drug development, ranging from in‐vitro to in‐vivo studies, and in studies devoted to a better understanding of the mechanism of action of mesotrypsin and KLK6 and to dissecting their roles at the molecular level and in animal models for cancer and other malignancies.