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Metastatic Castration-Resistant Prostate Cancer (mCRPC)Phase 1/2NCT03972657

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

A Phase 1/2 study testing REGN5678 and Cemiplimab in people with Metastatic Castration-Resistant Prostate Cancer (mCRPC) and Clear Cell Renal Cell Carcinoma (ccRCC), run by Regeneron Pharmaceuticals at 27 sites in 2 countries.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
Search all trials

Trial summary

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. Read more about this study

Who is it for?
Ages 18 years and older
What is being tested?
REGN5678 and Cemiplimab
Could I receive a placebo?
No, everyone receives an active treatment
How many people
345 participants
Where
27 sitesin 2 countries
Study dates
12 Aug 2019to 15 Nov 2027
Phase
Phase 1/2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • mCRPC cohorts (men):
  • Men with histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma.
  • PSA value at screening ≥4 ng/mL that has progressed within 6 months prior to screening as defined in the protocol.
  • Has received ≥2 lines prior systemic therapy approved in the metastatic and/or castration-resistant setting (in addition to Androgen Deprivation Therapy [ADT]) including at least:
  • one second-generation anti-androgen therapy (eg, abiraterone, enzalutamide, apalutamide, or darolutamide)
  • 177Lu-PSMA-617 radiotherapy, or another lutetium-based PSMA targeted radioligand, as described in the protocol
Show all 10Show fewer
  • ccRCC cohorts (men and women):
  • Histologically or cytologically confirmed RCC with a clear-cell component.
  • Diagnosis of metastatic ccRCC with at least one measurable lesion via RECIST 1.1 criteria
  • Has progressed on or after ≥1 line prior systemic therapy approved in the metastatic setting. Prior treatment must include an anti-Programmed Death-1 (receptor) [PD-1]/Programmed Death-Ligand 1 (PD-L1) therapy and either ipilimumab and/or a tyrosine kinase inhibitor

Who cannot join

  • Has received treatment with an approved systemic therapy within 3 weeks of dosing or has not yet recovered (ie, grade ≤1 or baseline) from any acute toxicities, as described in the protocol
  • Has received any previous systemic biologic therapy within 5 half-lives of first dose of study therapy, as described in the protocol
  • Has received prior PSMA-targeting therapy with the exception of a PSMA targeting radioligand (eg. 177Lu-PSMA-617) in mCRPC
  • Dose Escalation: Has had prior anti-cancer immunotherapy (other than sipuleucel-T) within 5 half-lives prior to study therapy.
  • Dose Expansion (mCRPC only): Has had prior anti-cancer immunotherapy, as described in the protocol
  • Any condition that requires ongoing/continuous corticosteroid therapy (>10 mg prednisone/day or anti-inflammatory equivalent) within 1 week prior to the first dose of study therapy
Show all 10Show fewer
  • Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments, as described in the protocol
  • Encephalitis, meningitis, neurodegenerative disease (with the exception of mild dementia that does not interfere with Activities of Daily Living [ADLs]) or uncontrolled seizures in the year prior to first dose of study therapy
  • Uncontrolled infection with Human Immunodeficiency Virus (HIV), hepatitis B or hepatitis C infection; or diagnosis of immunodeficiency
  • NOTE: Other protocol defined Inclusion/Exclusion Criteria apply

Trial locations and contacts

27 sites in 2 countries. Contact the study team or a site near you to ask about taking part.

Clinical Trials Administrator contact

844-734-6643

clinicaltrials@regeneron.com

27 sites in 2 countries

United States24 sites, 23 recruiting

  • Massachusetts General Hospital

    Boston, Massachusetts, 02114

    Recruiting

  • Emily Couric Clinical Cancer Center

    Charlottesville, Virginia, 22908

    Recruiting

  • James Cancer Hospital and Solove Research Institute

    Columbus, Ohio, 43210

    Recruiting

  • Sarah Cannon Research Institute (SCRI)

    Denver, Colorado, 80218

    Recruiting

  • Henry Ford Health

    Detroit, Michigan, 48202

    Recruiting

  • Banner MD Anderson Cancer Center

    Gilbert, Arizona, 85234

    Recruiting

  • MD Anderson Cancer Center

    Houston, Texas, 77030

    Recruiting

  • Mayo Clinic Jacksonville

    Jacksonville, Florida, 32224

    Recruiting

  • West Virginia University

    Morgantown, West Virginia, 26506

    Recruiting

  • Yale University Hospital

    New Haven, Connecticut, 06510

    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

  • Thomas Jefferson University Hospital

    Philadelphia, Pennsylvania, 19107

    Recruiting

  • Mayo Clinic

    Phoenix, Arizona, 85054

    Recruiting

  • Providence Portland Medical Center

    Portland, Oregon, 97213

    Withdrawn

  • Oregon Health & Science University (3485 S. Bond)

    Portland, Oregon, 97239

    Recruiting

  • Lifespan Cancer Institute

    Providence, Rhode Island, 02903

    Recruiting

  • Mayo Clinic

    Rochester, Minnesota, 55905

    Recruiting

  • University of Rochester Medical Center (URMC) - Wilmot Cancer Institute (WCI) (James P. Wilmot Cancer Center) - Rochester

    Rochester, New York, 14642

    Recruiting

  • John Wayne Cancer Institute (JWCI)

    Santa Monica, California, 90404

    Recruiting

  • Moffitt Cancer Center - McKinley Drive

    Tampa, Florida, 33612

    Recruiting

  • University of Arizona

    Tucson, Arizona, 85724

    Recruiting

Other trials in United States

South Korea3 sites, 3 recruiting

  • Yonsei University - Severance Hospital - Colorectal Cancer Clinic

    Seoul, 03722

    Recruiting

  • Asan Medical Center

    Seoul, 05505

    Recruiting

  • The Catholic University of Korea - St. Vincent's Hospital - Lung Cancer Center

    Suwon, Gyeonggi-do, 16247

    Recruiting

Other trials in South Korea

About this study

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

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.

Read more

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
Being tested
REGN5678, Cemiplimab
Medical subject headings
Carcinoma, Renal Cell

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • REGN5678Drug

    Also called Nezastomig

    Administered as per the protocol

  • CemiplimabDrug

    Also called REGN2810, LIBTAYO

    Administered as per the protocol

Study groups in NCT03972657
Study groupRoleWhat they receive
mCRPC - dose escalation cohortExperimentalREGN5678 with or without cemiplimab
Receives: Drug: REGN5678; Drug: Cemiplimab
mCRPC - dose expansion cohortExperimentalREGN5678 with or without cemiplimab
Receives: Drug: REGN5678
ccRCC - dose escalation cohortExperimentalREGN5678 with or without cemiplimab
Receives: Drug: REGN5678; Drug: Cemiplimab
ccRCC - dose expansion cohortExperimentalREGN5678 with or without cemiplimab
Receives: Drug: REGN5678

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Incidence and severity of Treatment-Emergent Adverse Events (TEAEs)

    Dose Escalation Phase

    Measured: Through study completion, up to 5 years

  2. Incidence and severity of Adverse Event of Special Interests (AESIs)

    Dose Escalation Phase

    Measured: Through study completion, up to 5 years

  3. Incidence and severity of Serious Adverse Events (SAEs)

    Dose Escalation Phase

    Measured: Through study completion, up to 5 years

  4. Number of participants with Grade ≥3 laboratory abnormalities

    Dose Escalation Phase

    Measured: Through study completion, up to 5 years

  5. Incidence of Dose-Limiting Toxicities (DLTs)

    Dose Escalation Phase

    Measured: First dose through day 42 of last participant in each dose level

  6. Concentration of REGN5678 in serum over time

    Dose Escalation Phase

    Measured: Through study completion, up to 5 years

  7. Concentration of REGN5678 in combination with cemiplimab in serum over time

    Dose Escalation Phase

    Measured: Through study completion, up to 5 years

  8. Composite Response Rate (CRR) of 50% decline of Prostate Specific Antigen (PSA) and/or confirmed radiographic response of complete (CR) or partial response (PR)

    Dose Expansion Phase - mCRPC cohort

    Measured: Through study completion, up to 5 years

  9. Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria

    Dose Expansion Phase - ccRCC cohort

    Measured: Through study completion, up to 5 years

Secondary outcomes (12)

  1. CRR of 50% decline of PSA and/or confirmed radiographic of CR or PR

    Dose Escalation Phase - mCRPC cohort

    Measured: Through study completion, up to 5 years

  2. ORR per RECIST 1.1 criteria

    Dose Escalation Phase - ccRCC cohort

    Measured: Through study completion, up to 5 years

  3. Incidence and severity of TEAEs

    Dose Expansion Phase

    Measured: Through study completion, up to 5 years

  4. Incidence and severity of AESIs

    Dose Expansion Phase

    Measured: Through study completion, up to 5 years

  5. Incidence and severity of SAEs

    Dose Expansion Phase

    Measured: Through study completion, up to 5 years

  6. Number of participants with grade ≥3 laboratory abnormalities

    Dose Expansion Phase

    Measured: Through study completion, up to 5 years

  7. Concentration of REGN5678 in serum over time

    Dose Expansion Phase

    Measured: Through study completion, up to 5 years

  8. Concentration of REGN5678 in combination with cemiplimab in serum over time

    Dose Expansion Phase

    Measured: Through study completion, up to 5 years

  9. Percentage of participants with ≥50% decline of PSA

    Dose Escalation and Dose Expansion Phases - mCRPC cohorts

    Measured: Through study completion, up to 5 years

  10. Percentage of participants with ≥90% decline of PSA

    Dose Escalation and Dose Expansion Phases- mCRPC cohorts

    Measured: Through study completion, up to 5 years

  11. Presence or absence of antibodies against REGN5678

    Dose Escalation and Dose Expansion Phases

    Measured: Through study completion, up to 5 years

  12. Presence or absence of antibodies against cemiplimab

    Dose Escalation and Dose Expansion Phases

    Measured: Through study completion, up to 5 years

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted3 Jun 2019
  2. Study start12 Aug 2019
  3. Primary completion15 Nov 2027 (estimated)
  4. Study completion15 Nov 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 1/2
Primary purpose
Treatment
Allocation
Non-randomised
Intervention model
Parallel groups
Masking
None (open label)
Enrolment
345 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT03972657
Sponsor's protocol ID
R5678-ONC-1879
Status last verified
Nov 2026
First submitted
30 May 2019
Last updated
4 Nov 2026
Results posted
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: All individual patient data (IPD) that underlie publicly available results will be considered for sharing

Questions about this trial

What is this clinical trial studying?

A Phase 1/2 study testing REGN5678 and Cemiplimab in people with Metastatic Castration-Resistant Prostate Cancer (mCRPC) and Clear Cell Renal Cell Carcinoma (ccRCC), run by Regeneron Pharmaceuticals at 27 sites in 2 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 10 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 4 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 27 sites in United States, South Korea. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Clinical Trials Administrator (844-734-6643, clinicaltrials@regeneron.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Incidence and severity of Treatment-Emergent Adverse Events (TEAEs) (time frame: Through study completion, up to 5 years). The study lists 9 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT03972657.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 4 Nov 2026.

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