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REGN5678

Phase 1

Metastatic Castration-Resistant Prostate Cancer (mCRPC) | Small molecule | Oncology |Regeneron Pharmaceuticals, Inc.|Last Updated: Jul 9, 2026

Target and mechanism

Molecular targetPSMA
Target classProtein
ModalitySmall molecule

Success Probability

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Market & Valuation

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Trial Design

CONTROLLED
Total Trials1
Total Enrollment345

FDA Designations

No designations recorded

Clinical trial landscape

REGN5678 · 1 trial · 2 indications

Phase 1 1
NCT03972657A 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 TumorsMetastatic Castration-Resistant Prostate Cancer (mCRPC)
RECRUITING345 Analytics
PHASE1RECRUITING
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
Metastatic Castration-Resistant Prostate Cancer (mCRPC)Unlock trial analytics

Study Endpoints

Primary Endpoints

Incidence and severity of Treatment-Emergent Adverse Events (TEAEs)
Through study completion, up to 5 years

Dose Escalation Phase

Incidence and severity of Adverse Event of Special Interests (AESIs)
Through study completion, up to 5 years

Dose Escalation Phase

Incidence and severity of Serious Adverse Events (SAEs)
Through study completion, up to 5 years

Dose Escalation Phase

Number of participants with Grade ≥3 laboratory abnormalities
Through study completion, up to 5 years

Dose Escalation Phase

Incidence of Dose-Limiting Toxicities (DLTs)
First dose through day 42 of last participant in each dose level

Dose Escalation Phase

Concentration of REGN5678 in serum over time
Through study completion, up to 5 years

Dose Escalation Phase

Concentration of REGN5678 in combination with cemiplimab in serum over time
Through study completion, up to 5 years

Dose Escalation Phase

Composite Response Rate (CRR) of 50% decline of Prostate Specific Antigen (PSA) and/or confirmed radiographic response of complete (CR) or partial response (PR)
Through study completion, up to 5 years

Dose Expansion Phase - mCRPC cohort

Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria
Through study completion, up to 5 years

Dose Expansion Phase - ccRCC cohort

Secondary Endpoints

CRR of 50% decline of PSA and/or confirmed radiographic of CR or PR
Through study completion, up to 5 years
ORR per RECIST 1.1 criteria
Through study completion, up to 5 years
Incidence and severity of TEAEs
Through study completion, up to 5 years
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Study Design & Arms

AllocationNON_RANDOMIZED
MaskingNONE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
mCRPC - dose escalation cohortEXPERIMENTALREGN5678 with or without cemiplimab
mCRPC - dose expansion cohortEXPERIMENTALREGN5678 with or without cemiplimab
ccRCC - dose escalation cohortEXPERIMENTALREGN5678 with or without cemiplimab
ccRCC - dose expansion cohortEXPERIMENTALREGN5678 with or without cemiplimab

Interventions

NameTypeDescription
REGN5678DRUGAdministered as per the protocol
CemiplimabDRUGAdministered as per the protocol
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites24

Key Inclusion Criteria: mCRPC cohorts (men): 1. Men with histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma. 2. PSA value at screening ≥4 ng/mL that has progressed within 6 months prior to screening as defined in the protocol. 3. Has received...

Countries:United States
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Recent Changes (Last 90 Days)

LOWJul 9, 2026NCT03972657lastUpdatePostDate: changed
LOWJul 9, 2026NCT03972657lastUpdatePostDate: changed
LOWJun 25, 2026NCT03972657lastUpdatePostDate: changed
LOWJun 25, 2026NCT03972657lastUpdatePostDate: changed
LOWJun 25, 2026NCT03972657lastUpdatePostDate: changed

Frequently asked questions about REGN5678

What is REGN5678 used for?

REGN5678 is an investigational small molecule being studied for the treatment of metastatic castration-resistant prostate cancer (mCRPC). It is also being evaluated in clear cell renal cell carcinoma (ccRCC) as part of a clinical trial. The drug is currently in Phase 1 development and has not been approved by regulatory authorities.

What does REGN5678 target?

REGN5678 targets PSMA, a protein that is highly expressed on prostate cancer cells. By binding to PSMA, the drug is designed to deliver a therapeutic effect specifically to cancer cells. This targeted approach is being investigated in patients with metastatic castration-resistant prostate cancer.

Who makes REGN5678?

REGN5678 is being developed by Regeneron Pharmaceuticals, Inc., a biopharmaceutical company traded on the Nasdaq under the ticker symbol REGN. The company is conducting clinical trials to evaluate the safety and efficacy of this investigational drug in patients with certain advanced cancers.

What phase is REGN5678 in?

REGN5678 is in Phase 1 clinical development. It is an investigational drug, meaning it has not been approved by the FDA or any other regulatory agency. The ongoing Phase 1 trial is recruiting participants to assess the drug's safety, tolerability, and preliminary activity in metastatic castration-resistant prostate cancer and other tumors.

What clinical trials is REGN5678 in?

REGN5678 is being studied in a Phase 1 clinical trial with the identifier NCT03972657. This trial is evaluating the drug alone or in combination with cemiplimab in adult participants with metastatic castration-resistant prostate cancer and other tumors. The study is recruiting up to 345 participants in the United States.

Is REGN5678 the same as Nezastomig?

Yes, REGN5678 is also known as Nezastomig. The clinical trial NCT03972657 refers to the drug as REGN5678 (Nezastomig). Both names refer to the same investigational small molecule being developed by Regeneron Pharmaceuticals for the treatment of certain advanced cancers.