[177Lu]Lu-XT381

Primary Objectives: 1) To evaluate the safety and tolerability of [177Lu]Lu-XT381 injection; 2) To preliminarily assess the efficacy (PSA50 response rate and ORR) of [177Lu]Lu-XT381 injection monotherapy in participants of a trial of prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer; 3) To determine the recommended dose (RP2D) for a phase II clinical trial of [177Lu]Lu-XT381 injection monotherapy in participants of a trial of prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer. Secondary objectives: 1) To further evaluate the safety and tolerability of [177Lu]Lu-XT381 injection; 2) To assess the efficacy of [177Lu]Lu-XT381 injection monotherapy in participants of a trial of prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer (efficacy endpoints: PSA90, maximum PSA response, time to PSA progression, rPFS, DOR, DCR, OS, SSE); 3) To evaluate the radiation dosimetry characteristics of [177Lu]Lu-XT381 injection; 4) To evaluate the pharmacokinetic characteristics of [177Lu]Lu-XT381 injection.