# 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** · PHASE3 · COMPLETED · sponsor: **Merck Sharp & Dohme LLC** · enrollment: 1030 (actual)

## Conditions studied

- Prostatic Neoplasms

## Interventions

- **BIOLOGICAL:** Pembrolizumab
- **DRUG:** Docetaxel
- **DRUG:** Prednisone
- **DRUG:** Placebo
- **DRUG:** Dexamethasone

## Key facts

- **NCT ID:** NCT03834506
- **Lead sponsor:** Merck Sharp & Dohme LLC
- **Sponsor class:** INDUSTRY
- **Phase:** PHASE3
- **Study type:** INTERVENTIONAL
- **Status:** COMPLETED
- **Start date:** 2019-05-02
- **Primary completion:** 2022-06-20
- **Final completion:** 2023-07-18
- **Target enrollment:** 1030 (ACTUAL)
- **Last updated:** 2025-07-18


## Primary source

ClinicalTrials.gov registry: https://clinicaltrials.gov/study/NCT03834506

## Citation

> US National Library of Medicine, ClinicalTrials.gov registration 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)". Retrieved via AI Analytics 2026-06-09 from https://api.ai-analytics.org/clinical/NCT03834506. Licensed CC0.

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