A Study of PSMA ADC in Subjects With Metastatic Castration-resistant Prostate Cancer (mCRPC)

Inclusion Criteria: 1. A diagnosis of metastatic castration-resistant prostate cancer. 2. a) Prior history of treatment with at least one taxane-containing chemotherapy regimen (e.g. docetaxel, cabazitaxel). If a subject has received more than two cytotoxic chemotherapy regimens, Sponsor approval is required for study participation. OR b) No prior history of treatment with a cytotoxic chemotherapy regimen. 3. Must have received and progressed on abiraterone acetate and/or enzalutamide. If subject is unable to receive abiraterone acetate and/or enzalutamide, Sponsor approval is required for participation in the study. 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2. 5. Life expectancy ≥ six months. 6. Cytotoxic chemotherapy-naïve subjects ONLY must have received and progressed on-, be ineligible for, refused, have an intolerance to-, or not have access to Radium-223. Exclusion Criteria: 1. Treatment within 30 days prior to first dose of study drug of the following: * External Radiation therapy * Radiopharmaceuticals * Cytotoxic chemotherapy * Treatment with an investigational agent 2. Clinically significant cardiac disease or severe debilitating pulmonary disease 3. An acute infection requiring ongoing antibiotic therapy 4. Any prior treatment with PSMA ADC or other therapies targeting PSMA, or other antibody drug conjugate (ADC) products that contain monomethyl auristatin E (MMAE) (e.g., brentuximab vedotin, glembatumumab vedotin, ASG-5ME, RG7450) unless approved by Sponsor. 5. History of drug and/or alcohol abuse 6. History of pancreatitis