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Investigating the safety and effectiveness of REGN4336 for advanced prostate cancer

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

Phase1; Phase2 Interventional Regeneron Pharmaceuticals · NCT05125016

This study is testing a new drug called REGN4336, alone and with other treatments, to see if it can safely help adults with advanced prostate cancer shrink their tumors.

Quick facts

PhasePhase1; Phase2
Study typeInterventional
Enrollment228 (estimated)
Ages18 Years and up
SexMale
SponsorRegeneron Pharmaceuticals Industry-sponsored
Drugs / interventionsimmunotherapy, prednisone
Locations14 sites (Palo Alto, California and 13 other locations)
Trial IDNCT05125016 on ClinicalTrials.gov

What this trial studies

This clinical trial is evaluating an investigational drug called REGN4336, both alone and in combination with other immunotherapy agents, cemiplimab and REGN5678, for adult patients with advanced metastatic castration-resistant prostate cancer (mCRPC). The study is divided into two parts: the first part aims to determine the safe dosage of REGN4336, while the second part assesses its effectiveness in shrinking tumors. Participants will be monitored for safety, tolerability, and treatment response throughout the trial. The approach focuses on activating T-cells to target and attack cancer cells.

Who should consider this trial

Good fit: Ideal candidates include adults with histologically confirmed metastatic castration-resistant prostate cancer who have progressed on or are intolerant to at least two prior systemic therapies.

Not a fit: Patients with pure small cell carcinoma of the prostate or those who have not received prior systemic therapy may not benefit from this study.

Why it matters

Potential benefit: If successful, this trial could provide a new effective treatment option for patients with advanced prostate cancer.

How similar studies have performed: Other studies have shown promise with similar immunotherapy approaches, indicating potential for success in this trial.

Eligibility criteria

Show full inclusion / exclusion criteria 
Key Inclusion Criteria:

1. Histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma
2. 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:

   1. PSA progression as defined by a rising PSA level confirmed with an interval of ≥1 week between each assessment
   2. Radiographic disease progression in soft tissue based on Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria with or without PSA progression
   3. 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
3. 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)

Key Exclusion Criteria:

1. 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
2. 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
3. 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
4. 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
5. Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments
6. 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
7. 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

Where this trial is running

Palo Alto, California and 13 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Metastatic Castration-resistant Prostate CancerTreatment-experienced metastatic Castration-Resistant Prostate Cancer
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.