CD46 and Familial prostate cancer: This study reports a novel CD46 targeted 212Pb alpha particle radioimmunotherapy, 212Pb-TCMC-YS5, that is well tolerated and shows potent anti-tumor activity (tumor growth inhibition and increase of animal survival) in vivo in three prostate cancer small animal models, i.e., a subcutaneous and an intraprostate orthotopic mCRPC cell line-derived xenograft models, and a prostate cancer patient-derived xenograft model.