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REGN21353

Phase 1

Metastatic Castration-Resistant Prostate Cancer | Small molecule | Oncology |Regeneron Pharmaceuticals, Inc.|Last Updated: Sep 30, 2026

Development status

Highest phase Phase 1
Registered trials 1 across 1 sponsor since Sep 2026

Success Probability

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Market & Valuation

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Trial Design

CONTROLLED
Total Trials1
Total Enrollment192

FDA Designations

No designations recorded

Clinical trial landscape

REGN21353 · 1 trial · 2 indications

Phase 1 1
NCT07850921REGN21353 Alone or in Combination With Nezastomig for Metastatic Castration-Resistant Prostate Cancer in Adult ParticipantsMetastatic Castration-Resistant Prostate Cancer
NOT YET_RECRUITING192 Analytics
PHASE1NOT YET_RECRUITING
REGN21353 Alone or in Combination With Nezastomig for Metastatic Castration-Resistant Prostate Cancer in Adult Participants
Metastatic Castration-Resistant Prostate CancerUnlock trial analytics

Study Endpoints

Primary Endpoints

Occurrence of Treatment Emergent Adverse Events (TEAEs)
Up to 5 years

Dose escalation

Occurrence of Dose-Limiting Toxicities (DLTs)
Up to 42 days

Dose escalation

Occurrence of Serious Adverse Events (SAEs)
Up to 5 years

Dose escalation

Occurrence of Adverse Events of Special Interests (AESIs)
Up to 5 years

Dose escalation

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)
Up to 5 years

Dose expansion

Secondary Endpoints

(CRR) of ≥50% decline of prostate specific antigen (PSA) and/or confirmed radiographic response of complete response (CR) or partial response (PR)
Up to 5 years
Occurrence of TEAEs
Up to 5 years
Occurrence of SAEs
Up to 5 years
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Study Design & Arms

AllocationNON_RANDOMIZED
MaskingNONE
ModelSEQUENTIAL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Module 1: monotherapyEXPERIMENTAL -
Module 2: combinationEXPERIMENTAL -

Interventions

NameTypeDescription
REGN21353DRUGAdministered per the protocol
NezastomigDRUGAdministered per the protocol
Sarilumab Prophylaxis (Contingency)DRUGMay be administered as pretreatment, per the protocol
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Eligibility Criteria

Age Range18 Years to N/A
SexMALE
Healthy VolunteersNo

Key Inclusion Criteria: 1. Is male with histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma 2. Has metastatic castration-resistant prostate cancer with prostate-specific antigen value as described in the protocol and that has progressed within ...

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Recent Changes (Last 90 Days)

LOWSep 30, 2026NCT07850921NEW_TRIAL: changed
LOWSep 30, 2026NCT07850921NEW_TRIAL: changed

Frequently asked questions about REGN21353

What is REGN21353?

REGN21353 is an investigational small molecule being developed by Regeneron Pharmaceuticals for metastatic castration-resistant prostate cancer, often abbreviated mCRPC. It is in Phase 1 clinical development and is not yet approved for any indication. It is being studied both as a single agent and in combination with another drug, nezastomig.

What is REGN21353 used for in metastatic castration-resistant prostate cancer?

REGN21353 is being evaluated for the treatment of metastatic castration-resistant prostate cancer, or mCRPC, in adult male patients. It is an investigational therapy and has not been approved for this or any other use. The ongoing study enrolls men aged 18 years and older with this condition.

Who is developing REGN21353?

REGN21353 is being developed by Regeneron Pharmaceuticals, Inc., which trades on the Nasdaq under the ticker REGN. Regeneron is the sponsor of the clinical program evaluating the compound in metastatic castration-resistant prostate cancer.

What phase is REGN21353 in?

REGN21353 is in Phase 1 clinical development. It is an investigational small molecule and is not FDA approved. The single registered trial is a Phase 1 study that has not yet begun recruiting participants.

What clinical trials is REGN21353 in?

REGN21353 is being studied in one registered clinical trial, NCT07850921, titled REGN21353 Alone or in Combination With Nezastomig for Metastatic Castration-Resistant Prostate Cancer in Adult Participants. The Phase 1 trial is not yet recruiting and plans to enroll 192 male participants aged 18 years and older.

Is REGN21353 combined with other drugs in its trial?

Yes. The Phase 1 trial NCT07850921 evaluates REGN21353 both as a single agent and in combination with nezastomig in adults with metastatic castration-resistant prostate cancer. The study is controlled, is not randomized, and is not double blinded, and it plans to enroll 192 participants.