TNFRSF17 and neoplasm: The enhanced efficacy in large solid tumors may be attributed to a combination of features unique to our ADC: (i) the fast-on/fast-off binding kinetics reduce the impact of competitive binding to sBCMA in circulation, (ii) the more transient binding of our antibody to BCMA may allow STI-8811 to diffuse deeper into the tumor rather than irreversibly binding the first available BCMA receptor on the tumor periphery, and (iii) the bystander effect allows improved penetration of the payload into adjacent and inner tumor cells.