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Metastatic Castration-resistant Prostate CancerPhase 1/2NCT05125016

A Trial to Find Out if REGN4336 is Safe and How Well it Works Alone and in Combination With REGN5678 for Adult Participants With Advanced Prostate Cancer

A Phase 1/2 study testing REGN4336 and REGN5678 in people with Metastatic Castration-resistant Prostate Cancer, run by Regeneron Pharmaceuticals at 14 sites in United States.

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

This study is researching an investigational drug called REGN4336 both alone or together with another investigational drug called REGN5678. The study is focused on participants with previously treated metastatic prostate cancer. Read more about this study

Who is it for?
Ages 18 years and older, men only
What is being tested?
REGN4336 and REGN5678
Could I receive a placebo?
No, everyone receives an active treatment
How many people
228 participants
Where
14 sitesUnited States
Study dates
30 Nov 2021to 28 Mar 2030
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
  • Men only
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma
  • Metastatic, Castration-Resistant Prostate Cancer (mCRPC) with PSA value at screening ≥4 ng/mL and that has progressed within 6 months prior to screening, according to at least 1 of the following:
  • PSA progression as defined by a rising PSA level confirmed with an interval of ≥1 week between each assessment
  • Radiographic disease progression in soft tissue based on Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria with or without PSA progression
  • Radiographic disease progression in bone defined as the appearance of 2 or more new bone lesions on bone scan with or without PSA progression NOTE: Measurable disease per RECIST version 1.1 per local reading at screening is not an eligibility criterion for enrollment
  • Has progressed upon or intolerant to ≥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 (e.g. abiraterone, enzalutamide, apalutamide, or darolutamide)

Who cannot join

  • Has received treatment with an approved systemic biologic therapy within 3 weeks of dosing or has not yet recovered (ie, grade ≤1 or baseline) from any acute toxicities except for laboratory changes as described in inclusion criteria
  • Has received any previous systemic biologic or anti-cancer immunotherapy within 5 half-lives of first dose of study therapy, as described in the protocol
  • Has received prior Prostate-Specific Membrane Antigen (PSMA)-targeting therapy NOTE: Prior therapy with PSMA-targeting radioligand(s) (eg, 177Lu-PSMA-617) is permitted. However, a period of 12 weeks must elapse between the last dose of the PSMA- targeting radioligand and the first dose of study drug
  • 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
  • Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments
  • 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 Virus (HBV), or Hepatitis C Virus (HCV) infection; or diagnosis of immunodeficiency, as described in the protocol.
  • NOTE: Other protocol defined Inclusion/Exclusion Criteria apply

Trial locations and contacts

14 sites in 1 country. Contact the study team or a site near you to ask about taking part.

Clinical Trials Administrator contact

844-734-6643

clinicaltrials@regeneron.com

14 sites in 1 country

United States14 sites, 13 recruiting

  • University of Maryland Greenebaum Cancer Center

    Baltimore, Maryland, 21201

    Recruiting

  • Roswell Park Cancer Institute

    Buffalo, New York, 14263

    Recruiting

  • Atrium Health Levine Cancer Institute

    Charlotte, North Carolina, 28204

    Recruiting

  • The Ohio State University James Cancer Hospital

    Columbus, Ohio, 43210

    Recruiting

  • MD Anderson Cancer Center

    Houston, Texas, 77030

    Recruiting

  • Norton Cancer Institute

    Louisville, Kentucky, 40207

    Recruiting

  • Medical College of Wisconsin

    Milwaukee, Wisconsin, 53226

    Recruiting

  • Rutgers Cancer Institute of New Jersey

    New Brunswick, New Jersey, 08901

    Recruiting

  • Yale University Hospital

    New Haven, Connecticut, 06510

    Recruiting

  • Stanford University Medical Center - Blake Wilbur Drive

    Palo Alto, California, 94304

    Recruiting

  • Penn Medicine University of Pennsylvania Health System

    Philadelphia, Pennsylvania, 19104

    Recruiting

  • Thomas Jefferson University Hospital

    Philadelphia, Pennsylvania, 19107

    Recruiting

  • Fox Chase Cancer Center

    Philadelphia, Pennsylvania, 19111

    Withdrawn

  • Fox Chase Cancer Center

    Philadelphia, Pennsylvania, 19111

    Recruiting

Other trials in United States

About this study

Official title: Phase 1/2 Study of REGN4336 (a PSMAxCD3 Bispecific Antibody) Administered Alone or in Combination With REGN5678 (a PSMAxCD28 Bispecific Antibody) in Patients With Metastatic Castration-Resistant Prostate Cancer

This study is researching an investigational drug called REGN4336 both alone or together with another investigational drug called REGN5678. The study is focused on participants with previously treated metastatic prostate cancer.

The main purpose of the study is to look at the safety, tolerability (how the body reacts to the drug) and effectiveness (how well the drug works to shrink tumors) of REGN4336 when given in combination with REGN5678.

Read more

The study has 2 parts. The purpose of Part 1 is to determine a safe dose(s) of REGN4336 to be given alone or in combination with REGN5678. Part 1 is known as the "dose escalation" phase.

The purpose of Part 2, (known as the "dose expansion" phase), is to use the doses of REGN4336 and REGN5678 selected in Part 1 to further test how well the combination treatment with REGN4336 and REGN5678 works to shrink tumors.

The study is looking at several other research questions, including:

  • What side effects may happen from taking REGN4336 alone or in combination with REGN5678
  • How well does REGN4336 in combination with REGN5678 reduce tumor size
  • How much REGN4336 is in the blood at different times when it is given alone or in combination with REGN5678
  • Does the body make antibodies against the study drugs (REGN4336 or REGN5678)
Being tested
REGN4336, REGN5678
Keywords
Treatment-experienced metastatic Castration-Resistant Prostate Cancer (mCRPC)

What participants receive

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

  • REGN4336Drug

    Administered per the protocol

  • REGN5678Drug

    Administered per the protocol

Study groups in NCT05125016
Study groupRoleWhat they receive
Module 1- MonotherapyExperimentalNot described
Receives: Drug: REGN4336
Module 3-Combo TherapyExperimentalNot described
Receives: Drug: REGN4336; Drug: REGN5678

What is being measured

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

  1. Incidence of Dose-Limiting Toxicities (DLTs)

    Dose escalation

    Measured: up to 21 days

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

    Dose escalation

    Measured: Up to 5 years

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

    Dose escalation

    Measured: Up to 5 years

  4. Incidence and severity of Adverse Events of Special Interest (AESIs)

    Dose escalation

    Measured: Up to 5 years

  5. REGN4336 monotherapy concentrations in serum

    Dose escalation

    Measured: Up to 5 years

  6. REGN4336 concentrations in serum in combination with REGN5678

    Dose escalation

    Measured: Up to 5 years

  7. Composite Response Rate (CRR) of ≥50% decline of prostate specific antigen (PSA) and/or confirmed radiographic response of complete response (CR) or partial response (PR)

    Dose expansion

    Measured: Up to 5 years

Secondary outcomes (9)

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

    Dose escalation

    Measured: Up to 5 years

  2. Anti-Drug Antibodies (ADA) to REGN4336

    Dose escalation

    Measured: Up to 5 years

  3. ADA to REGN4336 and REGN5678

    Dose escalation and dose expansion

    Measured: Up to 5 years

  4. Incidence and severity of TEAEs

    Dose expansion

    Measured: Up to 5 years

  5. Incidence and severity of SAEs

    Dose expansion

    Measured: Up to 5 years

  6. Incidence and severity of AESIs

    Dose expansion

    Measured: Up to 5 years

  7. REGN4336 concentrations in serum in combination with REGN5678

    Dose expansion

    Measured: Up to 5 years

  8. Percentage of patients with ≥50% reduction in PSA confirmed by a second PSA test ≥3 weeks later

    Dose escalation and dose expansion

    Measured: Up to 5 years

  9. Percentage of patients with ≥90% reduction in PSA confirmed by a second PSA test ≥3 weeks later

    Dose escalation and dose expansion

    Measured: 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 posted18 Nov 2021
  2. Study start30 Nov 2021
  3. Primary completion28 Mar 2030 (estimated)
  4. Study completion28 Mar 2030 (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
Model description
Note: Prior to the current protocol amendment (PA), a Module to evaluate REGN4336 in combination with cemiplimab was included in the study design (Module 2). This Module was de-prioritized in this PA and removed. No patients were dosed in Module 2
Masking
None (open label)
Enrolment
228 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05125016
Sponsor's protocol ID
R4336-ONC-20104
Other IDs
2022-502130-17-00
Status last verified
Apr 2026
First submitted
25 Oct 2021
Last updated
5 May 2026
Results posted
No
Data monitoring committee
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 REGN4336 and REGN5678 in people with Metastatic Castration-resistant Prostate Cancer, run by Regeneron Pharmaceuticals at 14 sites in United States.

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 6 inclusion and 8 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 5 May 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 14 sites in United States. 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 of Dose-Limiting Toxicities (DLTs) (time frame: up to 21 days). The study lists 7 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 NCT05125016.

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 5 May 2026.

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