Danila DC, Szmulewitz RZ, Vaishampayan U, et al. - Researchers examined the safety and activity of DSTP3086S, a humanized immunoglobulin G1 anti-six-transmembrane epithelial antigen of the prostate 1 (STEAP1) monoclonal antibody linked to the potent antimitotic agent monomethyl auristatin E, in patients with metastatic castration-resistant prostate cancer. In a 3 + 3 dose escalation study, 77 patients were given DSTP3086S (0.3 to 2.8 mg/kg intravenously) once every 3 weeks, and seven were treated weekly. Outcomes revealed an acceptable safety profile of DSTP3086S at the recommended phase II dose level of 2.4 mg/kg once every 3 weeks. They observed antitumor activity at doses between 2.25 and 2.8 mg/kg once every 3 weeks. This suggests the potential benefit of managing STEAP1-expressing metastatic castration-resistant prostate cancer with an STEAP1-targeting antibody-drug conjugate.