Study of Pembrolizumab (MK-3475) in Participants With Metastatic Castration-Resistant Prostate Cancer (mCRPC)(MK-3475-199/KEYNOTE-199)

Official Title

Phase II Trial of Pembrolizumab (MK-3475) in Subjects With Metastatic Castration-Resistant Prostate Cancer (mCRPC) (KEYNOTE-199)

Summary:

This is a study of pembrolizumab (MK-3475) in participants with metastatic castration-resistant prostate cancer (mCRPC). Participants will be enrolled into one of five cohorts: Cohort 1 (participants with programmed cell death ligand 1 [PD-L1]-positive, measurable disease), Cohort 2 (participants with PD-L1 negative, measurable disease), Cohort 3 (participants with bone-metastases and non-measurable disease) post-chemotherapy, Cohort 4 (participants with Response Evaluation Criteria in Solid Tumours version 1.1- [RECIST 1.1]-measureable disease) and Cohort 5 (participants with bone metastases only or bone-predominant disease) pre-chemotherapy.

Trial Description

Primary Outcome:

• Objective Response Rate (ORR) by Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 assessed by central imaging vendor (Cohorts 1 and 2 combined, Cohort 1, Cohort 2 and Cohort 4)

Secondary Outcome:

• Disease Control Rate (DCR) (Cohorts 1 and 2 combined, Cohorts 1, 2, and 3 combined, Cohorts 4 and 5 combined, and by each cohort)
• Prostate-specific Antigen (PSA) response rate (Cohorts 1 and 2 combined, Cohorts 1, 2, and 3 combined, Cohorts 4 and 5 combined, and by each cohort)
• Percentage of participants who experience an adverse event (AE) (All cohorts combined and by each cohort)
• Percentage of participants who discontinue study drug due to an AE (All cohorts combined and by each cohort)

Participants with mCRPC previously treated with docetaxel-based chemotherapy in Cohorts 1 to 3 will receive monotherapy with pembrolizumab. Chemotherapy-naïve subjects with mCRPC either having failed or showing signs of failure with enzalutamide in Cohorts 4 and 5 will receive pembrolizumab monotherapy in addition to their current regimen of enzalutamide. In all cohorts, pembrolizumab administration will occur on Day 1 of each 3-week dosing cycle and will continue for a maximum of 35 cycles (approximately 2 years) unless specific withdrawal/discontinuation criteria are met. Participants who discontinue after 35 infusions of pembrolizumab for reasons other than disease progression or intolerability, or who discontinue after attaining a complete response may be eligible for up to 17 additional infusions (approximately 1 year) after they have experienced disease progression.

View this trial on ClinicalTrials.gov