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

ClinicalTrials.gov ID: NCT03972657

Public ClinicalTrials.gov record NCT03972657. Field values are reproduced from the official study page; the official ClinicalTrials.gov record remains the source of truth for eligibility, enrollment, and contact information.

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Official title

A Phase 1/2 Study of REGN5678 (Anti-PSMAxCD28) With or Without Cemiplimab (Anti-PD-1) in Patients With Metastatic Castration-Resistant Prostate Cancer and Other Tumors Associated With PSMA Expression

Brief summary

Reproduced verbatim from the official ClinicalTrials.gov record. Not medical advice.

The main purpose of this study is to determine the safety, tolerability (how the body reacts to the drug\[s\]) and effectiveness (ability to treat the cancer) of REGN5678 (Nezastomig) alone, or in combination with cemiplimab. The study has 2 parts. The goal of Part 1 (dose escalation) is to determine a safe dose(s) of REGN5678 when it is given alone or in combination with cemiplimab. The goal of Part 2 (dose expansion) is to use the REGN5678 drug dose(s) found in Part 1 to see how well REGN5678 alone or in combination with cemiplimab works to shrink tumors. This study is looking at several other research questions, including: 1. Side effects that may be experienced by taking REGN5678 alone or in combination with cemiplimab 2. How REGN5678 alone or in combination with cemiplimab works in the body 3. How much REGN5678 and/or cemiplimab are present in the blood 4. To see if REGN5678 alone or in combination with cemiplimab works to reduce the size of the tumor by helping the immune system destroy the tumor

Study identification

NCT ID: NCT03972657
Recruitment status: Recruiting
Study type: Interventional
Phase: Phase 1, Phase 2
Lead sponsor: Regeneron Pharmaceuticals; Industry
Enrollment: 345 participants

Conditions and interventions

Conditions

Interventions

REGN5678 Drug
Cemiplimab Drug

Drug

Eligibility (public fields only)

Age range: 18 Years and older
Sex: All
Healthy volunteers: Healthy volunteers not accepted

This page does not interpret eligibility. Detailed inclusion and exclusion criteria are on the official ClinicalTrials.gov record.

Study timeline

Start date: Aug 11, 2019
Primary completion: Nov 14, 2027
Completion: Nov 14, 2027
Last update posted: Jul 8, 2026

2019 – 2027

United States locations

U.S. sites: 24
U.S. states: 16
U.S. cities: 20

Facility	City	State	ZIP	Site status
Banner MD Anderson Cancer Center	Gilbert	Arizona	85234	Recruiting
Mayo Clinic	Phoenix	Arizona	85054	Recruiting
University of Arizona	Tucson	Arizona	85724	Recruiting
John Wayne Cancer Institute (JWCI)	Santa Monica	California	90404	Recruiting
Sarah Cannon Research Institute (SCRI)	Denver	Colorado	80218	Recruiting
Yale University Hospital	New Haven	Connecticut	06510	Recruiting
Mayo Clinic Jacksonville	Jacksonville	Florida	32224	Recruiting
Moffitt Cancer Center - McKinley Drive	Tampa	Florida	33612	Recruiting
Massachusetts General Hospital	Boston	Massachusetts	02114	Recruiting
Henry Ford Health	Detroit	Michigan	48202	Recruiting
Mayo Clinic	Rochester	Minnesota	55905	Recruiting
NYU Langone Health Perlmutter Cancer Center	New York	New York	10016	Recruiting
Icahn School of Medicine at Mount Sinai	New York	New York	10029	Recruiting
Columbia University - The Trustees of Columbia University in the City of New York	New York	New York	10032	Recruiting
Montefiore Medical Center	New York	New York	10461	Recruiting
University of Rochester Medical Center (URMC) - Wilmot Cancer Institute (WCI) (James P. Wilmot Cancer Center) - Rochester	Rochester	New York	14642	Recruiting
James Cancer Hospital and Solove Research Institute	Columbus	Ohio	43210	Recruiting
Providence Portland Medical Center	Portland	Oregon	97213	Withdrawn
Oregon Health & Science University (3485 S. Bond)	Portland	Oregon	97239	Recruiting
Thomas Jefferson University Hospital	Philadelphia	Pennsylvania	19107	Recruiting
Lifespan Cancer Institute	Providence	Rhode Island	02903	Recruiting
MD Anderson Cancer Center	Houston	Texas	77030	Recruiting
Emily Couric Clinical Cancer Center	Charlottesville	Virginia	22908	Recruiting
West Virginia University	Morgantown	West Virginia	26506	Recruiting

Site contact phone numbers, emails, and investigator names are intentionally not displayed here. Open the official ClinicalTrials.gov record for site contact information.

About this trial record page

What this page shows: Public field values for ClinicalTrials.gov record NCT03972657, including study identification, conditions, interventions, eligibility (age, sex, healthy volunteer), timeline, and U.S. site list.
What this page does not do: No medical advice, eligibility judgments, treatment recommendations, study quality scoring, or AI-generated medical summaries. No site contact phone numbers, emails, or investigator names.
Where the data comes from: Sourced from the official ClinicalTrials.gov public API. The official record is the source of truth.
Last refresh: Last update posted Jul 8, 2026 · Synced Sep 4, 2026

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The complete protocol, eligibility criteria, and contact information for NCT03972657 live on ClinicalTrials.gov.

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