The specific design of SPNpro allows for the targeted proteolysis of immunosuppressive enzymes, such as indoleamine 2,3-dioxygenase (IDO), in response to the presence of the cancer biomarker Cathepsin B (CatB), which plays a crucial role in the activation of SPNpro’s PROTAC function in various cancer cells (Figure 10). The gene discussed is TYRP1; the disease is cancer.