NCT03834506

Study of Pembrolizumab (MK-3475) Plus Docetaxel Versus Placebo Plus Docetaxel in Chemotherapy-naïve Metastatic Castration-resistant Prostate Cancer (mCRPC) (MK-3475-921/KEYNOTE-921)

A Phase 3, Randomized, Double-blind Study of Pembrolizumab (MK-3475) Plus Docetaxel Plus Prednisone Versus Placebo Plus Docetaxel Plus Prednisone in Participants With Chemotherapy-naïve Metastatic Castration-Resistant Prostate Cancer (mCRPC) Who Have Progressed on a Next Generation Hormonal Agent (NHA) (KEYNOTE-921)

• Status: Completed
• Phase: Phase 3
• Study type: Interventional
• Enrollment: 1,030 (actual)
• Sponsor: Merck Sharp & Dohme LLC · Industry
• Sex: Male
• Age: 18 Years
• Healthy volunteers: Not accepted

Summary

The purpose of this study is to assess the efficacy and safety of the combination of pembrolizumab (MK-3475) and docetaxel in the treatment of men with metastatic castration-resistant prostate cancer (mCRPC) who have not received chemotherapy for mCRPC but have progressed on or are intolerant to Next Generation Hormonal Agent (NHA). There are two primary study hypotheses. Hypothesis 1: The combination of pembrolizumab plus docetaxel plus prednisone is superior to placebo plus docetaxel plus prednisone with respect to Overall Survival (OS). Hypothesis 2: The combination of pembrolizumab plus docetaxel plus prednisone is superior to placebo plus docetaxel plus prednisone with respect to Radiographic Progression-free Survival (rPFS) per Prostate Cancer Working Group (PCWG)-modified Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as assessed by blinded independent central review.

Detailed description

With Amendment 6 (effective date: 29-Sep-2022), all participants will be unblinded and placebo treatment will be stopping. Participants who are deemed to be deriving clinical benefit from treatment may continue at the discretion of the investigator. The global study for MK-3475-921 enrolled 1030 participants. Of the 1030 total participants enrolled in the global study, 21 were also enrolled in the China extension study for MK-3475-921 (NCT04907227).

Conditions

• Prostatic Neoplasms

Interventions

Type	Name	Description
BIOLOGICAL	Pembrolizumab	IV infusion
DRUG	Docetaxel	IV infusion
DRUG	Prednisone	Oral tablets
DRUG	Placebo	IV infusion
DRUG	Dexamethasone	Oral tablets

Timeline

• Start date: 2019-05-02
• Primary completion: 2022-06-20
• Completion: 2023-07-18
• First posted: 2019-02-08
• Last updated: 2025-07-18
• Results posted: 2023-06-18

Locations

215 sites across 21 countries: United States, Argentina, Australia, Austria, Brazil, Canada, Chile, China, Colombia, France, Germany, Ireland, Israel, Italy, Japan, Netherlands, Russia, South Korea, Spain, Taiwan, United Kingdom

Regulatory

• FDA-regulated drug study