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)

What the Registry Record Tells You About NCT03834506

The ClinicalTrials.gov registry entry for NCT03834506 describes a study currently listed as completed. It is categorized as Phase 3, which is the standard way researchers label where a study sits along the investigational pathway from early safety work through later efficacy and post-marketing evaluation. The registered enrollment target is 1,030 participants, a figure that helps gauge the scale of data the investigators plan to collect. The listed sponsor is Merck Sharp & Dohme, which has 741 total studies on file at ClinicalTrials.gov, and sponsors are the parties responsible for study design, oversight, and regulatory filings.

The record links to 1 condition, with Prostatic Neoplasms appearing as the primary indexed condition, and to 5 interventions — of which Pembrolizumab is the first listed. Interventions can include drugs, devices, procedures, behavioral programs, or observational arms, and each is tracked as a separate registry field so that downstream queries can filter accurately. When a trial lists multiple interventions, it usually reflects a multi-arm design or a comparison protocol rather than a single treatment being tested in isolation. The brief summary published in the registry is the clearest source of protocol intent and should be read before drawing conclusions from any sidebar tags.

Geographic footprint matters for practical reasons: NCT03834506 reports 20 study locations spanning 15 distinct geographic areas — top geographies include California, Michigan, Alabama. A larger site network tends to correlate with broader recruitment capacity, but it does not imply anything about study quality, and site-level enrollment status can diverge from the overall registry status shown above. Every data point on this page comes from the public ClinicalTrials.gov dataset and is reproduced here for reference only; it is not a medical recommendation, an endorsement of the sponsor, or an invitation to enroll. Verify current status, eligibility criteria, and contact details directly at ClinicalTrials.gov, and discuss any participation decision with your own healthcare provider.