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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)

NCT03834506 · Status: COMPLETED · Phase: PHASE3 · Type: INTERVENTIONAL · Enrollment: 1030

Last updated 2025-07-18

Study results available
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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.

Conditions

  • Prostatic Neoplasms

Interventions

BIOLOGICAL

Pembrolizumab

IV infusion

DRUG

Docetaxel

IV infusion

DRUG

Prednisone

Oral tablets

DRUG

Placebo

IV infusion

DRUG

Dexamethasone

Oral tablets

Sponsors & Collaborators

Principal Investigators

  • Medical Director · Merck Sharp & Dohme LLC

Study Design

Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Model
PARALLEL

Eligibility

Min Age
18 Years
Sex
MALE
Healthy Volunteers
No

Timeline & Regulatory

Start
2019-05-02
Primary Completion
2022-06-20
Completion
2023-07-18
FDA Drug
Yes

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

Study Locations

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Entities

Drugs
Companies

Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT03834506 on ClinicalTrials.gov