The landmark analysis for 6 month rPFS rate will occur when all participants on Part 1 have been on study for at least 6 months.

All participants according to the study treatment assigned (Intent to Treat Population) for participants with mCRPC in Part 1 only. This outcome measure applies to Part 1 only. Per protocol, participants in Part 2 did not have mCRPC and were not part of this analysis.

The ORR is defined as the percentage of participants in the response evaluable population who achieve a best overall response of complete response (CR) or partial response (PR), per RECIST version 1.1 criterial CR is defined as disappearance of all target and non-target lesions. PR is defined as at least a 30% decrease from baseline in the sum of diameters of target lesions.

All participants who received at least one dose of study treatment and had RECIST-evaluable disease per RECIST v1.1 (Tumor Response Evaluable Population) in Part 2 of the study.

To qualify as an objective response, CR and PR require confirmation at least 4 weeks after initial observation of complete response (CR) or partial response (PR). CR + PR = ORR

The analysis is limited to only participants with mCRPC who experienced a complete or partial response to study treatment. None of the participants in the control arm experienced a complete or partial response to study treatment. Participants in Part 2 did not have mCRPC, so were not eligible for response using PCWG3 criteria.

The DoR will be calculated as the time from the date of initial tumor response (CR or PR) to the date of first documented PD or death from any cause, whichever occurs first.

All participants with mCRPC who achieved a confirmed complete or partial response to study treatment. No participants in the control group had a complete or partial response. Participants in Part 2 did not have mCRPC, so were not eligible for response using PCWG3 criteria.

All participants with mCRPC who received at least one dose of study treatment and had RECIST-evaluable disease per PCWG3 (Tumor Response Evaluable Population) in Part 1 of the study. Participants in Part 2 of the study did not have mCRPC and are excluded from this analysis.

PSA response is defined as a ≥ 50% decline in PSA from baseline with PSA confirmation ≥ 3 weeks after the first documented reduction in PSA of ≥ 50%.

All participants in Part 1 who received at least one dose of study treatment, with a baseline PSA ≥ 2 ng/mL and at least one post-baseline PSA measurement (PSA Response Evaluable Population). There were no participants in the Control Arm that were part of the PSA Response Evaluable Population.

Participants in Part 2 did not have mCRPC, so were not assessed using PSA measurement.

In participants with a decrease in PSA from baseline, PSA progression is defined as a ≥ 25% increase and an absolute increase of ≥ 2 ng/mL above the nadir value, which is confirmed by a consecutive second value obtained ≥ 3 weeks later.

In participants with no decrease in PSA from baseline, PSA progression is defined as a ≥ 25% increase and an absolute increase of ≥ 2 ng/mL above the baseline value after 12 weeks.

Time to PSA progression is defined as the time from the date of randomization to the first PSA progression.

The ITT population for Part 1 was used for this analysis. Only 3 of 7 participants were treated in the in the control arm. Of the 3 participants treated in the control arm, only 1 participant had an event.

Participants in Part 2 did not have mCRPC, so were not assessed using PSA measurement.

Duration of PSA response is defined as the time from the date of first documented PSA response to the earliest date of PSA progression.

All participants in Part 1 who met criteria for a PSA response to study treatment. There were no participants in the Control Arm that were part of the PSA Response Evaluable Population. Participants in Part 2 did not have mCRPC, so were not assessed using PSA measurement.

PSA Response Evaluable Population. There were no participants in the Control Arm that were part of the PSA Response Evaluable Population. Participants in Part 2 did not have mCRPC, so were not assessed using PSA measurement.

An SSE is defined as any of the following events: new symptomatic pathological fracture, requirement for radiation therapy to relieve bone pain, spinal cord compression, or tumor-related orthopedic surgical intervention. The time to first SSE is defined as the time from the date of randomization to the first occurrence of SSE.

Participants who experienced a symptomatic skeletal event in Part 1 of the study. SSE were not assessed in Part 2, as these participants did not have mCRPC.

The Safety Population was used for this analysis.

Participant specimens were evaluated for the presence of ADA beginning a baseline and throughout the study. If at any time during the study, the results show evidence of ADA, they were counted as ADA positive. There was no time-to- event analysis nor by visit analysis of the data.

The ADA Evaluable Population was used for this analysis. Participants in the control arm did not receive MGC018.

The DoR will be calculated as the time from the date of initial tumor response (CR or PR) to the date of first documented progressive disease (PD) or death from any cause, whichever occurs first.

No participants in Part 2 of the study had a complete or partial response to study treatment.

PFS is defined as the time from the date of the first dose to the date of first PD per RECIST 1.1 criteria or death from any cause, whichever occurs first.