In PDX models of metastatic prostate cancer, MGC018 was active as a single agent toward heterogeneous B7-H3-expressing tumors, and combining MGC018 with inhibitors of PARP or AR led to a greater response in some models…MGC018 demonstrated potent antitumor activity in vivo toward CDX and PDX models of prostate cancer, and enhanced antitumor activity when combined with inhibitors of PARP or AR.