Subjects started the extension study at the same dose received upon completion of the core PSMA ADC 2301 study. Each Prostate Specific Membrane Antigen Antibody Drug Conjugate (PSMA ADC) dose was administered as an IV infusion over approximately 60 minutes once every three weeks (Q3W) for up to eight doses, unless a dose delay or dose reduction was required.

Upon recommendation from the PI and after Sponsor approval, a subject benefiting from treatment could have received up to eight additional doses Q3W. Subjects were weighed prior to each cycle and dosing was calculated on a mg/kg basis prior to each dose, with a maximum weight of 100 kg for dosing calculations.

Total serum PSA (prostate-specific antigen) was measured at baseline and had at least one post-baseline assessment. PSA response was examined at two levels: at least 30% decrease or at least 50% decrease in serum PSA. Response was assessed as the maximum decrease over the extension study. Response was defined as any decrease from baseline of at least 30% or 50%.

Circulating tumor cells (CTC) response was measured at baseline and had at least one post-baseline assessment. Response was assessed as the maximum decrease over the extension study. Response was defined as any decrease from baseline of at least 50%.

Overall radiologic response was measured at baseline and post-baseline. Imaging techniques used at screening were used throughout the study. The preferred imaging techniques include: bone scan, contrast enhanced CT of chest, contrast enhanced CT of pelvis, and contrast enhanced CT of upper & lower abdomen. Best overall radiologic response (confirmed), target and non-target lesions, was defined as responses in bone, visceral or nodal metastases according to the Modified Response Evaluation Criteria (RECIST 1.1). The best overall radiologic response is the best response recorded from the start of the treatment until disease progression/recurrence (taking, as reference for progressive disease, the smallest measurements recorded since the treatment started). The subject's best response assignment depended on the achievement of both measurement and confirmation criteria.

Subjects started the extension study at the same dose received upon completion of the core PSMA ADC 2301 study. Each Prostate Specific Membrane Antigen Antibody Drug Conjugate (PSMA ADC) dose was administered as an IV infusion over approximately 60 minutes once every three weeks (Q3W) for up to eight doses, unless a dose delay or dose reduction was required.

PSMA ADC: Upon recommendation from the PI and after Sponsor approval, a subject benefitting from treatment could have received up to eight additional doses Q3W. Subjects were weighed prior to each cycle and dosing was calculated on a mg/kg basis prior to each dose, with a maximum weight of 100 kg for dosing calculations.

Total serum PSA (prostate-specific antigen) was measured at baseline and had at least one post-baseline assessment. PSA response was examined at two levels: at least 30% decrease or at least 50% decrease in serum PSA. Response was assessed as the maximum decrease over the extension study. Response was defined as any decrease from baseline of at least 30% or 50%.

Both groups must also have received and progressed on abiraterone acetate and/or enzalutamide prior to the study (once these agents were commercially available for use). The population examined was those subjects with a PSA baseline value and at least one post-baseline value.

The chemotherapy-experienced group was comprised of 6 subjects who must have received at least one taxane-containing chemotherapy regimen (e.g., docetaxel, cabazitaxel) prior to the study (more than two cytotoxic chemotherapy regimens required sponsor approval for study participation).

Subjects started the extension study at the same dose received upon completion of the core PSMA ADC 2301 study. Each PSMA ADC dose was administered as an IV infusion over approximately 60 minutes once every three weeks (Q3W) for up to eight doses, unless a dose delay or dose reduction was required.