REGN5678 and Cemiplimab for Metastatic Prostate and Other Cancers

This study is testing REGN5678 (Nezastomig) alone or with cemiplimab in adults with metastatic castration-resistant prostate cancer (mCRPC) or clear cell renal cell carcinoma (ccRCC). The main goals are to find a safe dose and see how well these drugs shrink tumors. Researchers are also looking at side effects. This study has two parts: first, to find the right dose, and then to see how effective that dose is. Participants must be 18 or older. For men with mCRPC, specific prostate-specific antigen (PSA) levels and progression within 6 months are required. This is an immunotherapy study.

Study design
This interventional study plans to enroll 345 participants. It has two parts: a dose escalation phase and a dose expansion phase.
What's involved
Not specified in the trial record.
Compensation
Not stated in the trial record.
Follow-up
Participants will be followed for treatment-emergent adverse events, adverse events of special interest, and serious adverse events through study completion, up to 5 years.

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NCT03972657

A Trial to Find Out if REGN5678 (Nezastomig) is Safe and How Well it Works Alone or in Combination With Cemiplimab for Adult Participants With Metastatic Castration-Resistant Prostate Cancer and Other Tumors

Recruiting
PHASE1Ages 18+InterventionalTreatment
Regeneron Pharmaceuticals
~345 participants
Updated 2026-07-09 on ClinicalTrials.gov
What's tested:REGN5678Cemiplimab

At a glance

Recruiting sites
23 of 24 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Incidence and severity of Treatment-Emergent Adverse Events (TEAEs)
Measured over Through study completion, up to 5 years
+8 more outcomes measured
Metastatic Castration-Resistant Prostate Cancer (mCRPC)
Clear Cell Renal Cell Carcinoma (ccRCC)
24 sites across 16 states
New York5
Arizona3
Florida2
Oregon2
California1
Colorado1
Connecticut1
Massachusetts1
  • Clinical Trials Management · STUDY_DIRECTOR · Regeneron Pharmaceuticals

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  • Incidence and severity of Treatment-Emergent Adverse Events (TEAEs)Through study completion, up to 5 years

    Dose Escalation Phase

  • Incidence and severity of Adverse Event of Special Interests (AESIs)Through study completion, up to 5 years

    Dose Escalation Phase

  • Incidence and severity of Serious Adverse Events (SAEs)Through study completion, up to 5 years

    Dose Escalation Phase

  • Number of participants with Grade ≥3 laboratory abnormalitiesThrough study completion, up to 5 years

    Dose Escalation Phase

  • Incidence of Dose-Limiting Toxicities (DLTs)First dose through day 42 of last participant in each dose level

    Dose Escalation Phase

  • Concentration of REGN5678 in serum over timeThrough study completion, up to 5 years

    Dose Escalation Phase

  • Concentration of REGN5678 in combination with cemiplimab in serum over timeThrough study completion, up to 5 years

    Dose Escalation Phase

  • Composite Response Rate (CRR) of 50% decline of Prostate Specific Antigen (PSA) and/or confirmed radiographic response of complete (CR) or partial response (PR)Through study completion, up to 5 years

    Dose Expansion Phase - mCRPC cohort

  • Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteriaThrough study completion, up to 5 years

    Dose Expansion Phase - ccRCC cohort