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Updated June 2026 · ClinicalTrials.gov

RECRUITINGPhase 1 / Phase 2INTERVENTIONAL

A Study to Find Out How Safe REGN5668 is and How Well it Works In Adult Women When Given With Either Cemiplimab, or Cemiplimab + Fianlimab, or Ubamatamab

A Phase 1/2 Study of REGN5668 (MUC16xCD28, a Costimulatory Bispecific Antibody) Administered in Combination With Other Agents in MUC16 + Malignancies

A Study to Find Out How Safe REGN5668 is and How Well it Works In Adult Women When Given With Either Cemiplimab, or Cemiplimab + Fianlimab, or Ubamatamab (NCT04590326) is a Phase 1 / Phase 2 interventional studying Ovarian Cancer and Fallopian Tube Cancer, sponsored by Regeneron Pharmaceuticals. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

Important: This information is not medical advice. Talk to your doctor about whether a clinical trial is right for you.

About This Trial

This study is researching an investigational drug called REGN5668 : * alone or, * combined with cemiplimab (also known as REGN2810) or, * combined with both cemiplimab and fianlimab (also known as REGN3767), or * combined with ubamatamab (also known as REGN4018), with or without sarilumab. The main purposes of this study are to: * Learn about the safety and profile of any side effects from the study drugs and to determine the highest, safe dose that can be given to participants with ovarian cancer or cancer of the uterus * Look for signs that the study drugs can treat ovarian cancer or cancer of the uterus This study has 2 parts. The purpose of Part 1 (Escalation) is to find the highest, safe dose of the study drug(s). The purpose of Part 2 (Expansion) is to use the doses chosen in Part 1. Participants with cancer of the uterus will only participate in Part 2. The study is looking at several other research questions, including: * Side effects that may be experienced by participants taking REGN5668 alone and/or in combination with cemiplimab, cemiplimab and fianlimab, or ubamatamab * How REGN5668 works in the body either alone and/or in combination with cemiplimab, cemiplimab and fianlimab, or ubamatamab * How much of the study drugs (REGN5668, cemiplimab, fianlimab, ubamatamab) are in the blood * To see if REGN5668 in combination with cemiplimab, cemiplimab and fianlimab, or ubamatamab works to treat cancer

What Stage of Research Is This?

Phase 1 trials test a new treatment for the first time in humans, focusing on safety, dosing, and how the body processes the drug. For Ovarian Cancer, a Phase 1 study typically enrolls a small number of participants — often healthy volunteers or patients who have exhausted standard treatment options. Phase 1 results determine whether a treatment moves into larger Phase 2 efficacy studies.

This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.

A target enrollment of 612 participants makes this a sizable late-stage trial. Studies in this range typically have enough power to detect clinically meaningful differences from a comparator and to characterize less-common side effects.

Who May Be Eligible (Plain English)

Key Who May Qualify: 1. Ovarian Cancer Cohorts Only: Has diagnosed by tissue sample (biopsy-confirmed) diagnosis of advanced epithelial ovarian cancer (except carcinosarcoma), primary peritoneal, or fallopian tube cancer that has received at least 1 line of platinum-based systemic therapy as defined in the protocol 2. Expansion cohorts only: Has at least 1 lesion that is measurable by RECIST 1.1 as described in the protocol. 3. Has a serum CA-125 level ≥2x ULN (in screening, not applicable to endometrial cohorts) 4. Has adequate organ and bone marrow function as defined in the protocol 5. Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 6. Has a expected to live at least 3 months 7. Endometrial Cancer Cohorts Only: diagnosed by tissue sample (biopsy-confirmed) endometrial cancer that has progressed or recurrent after prior anti-PD-1 therapy and platinum-based chemotherapy as described in the protocol Key Who Should NOT Join This Trial: 1. Current or recent (as defined in the protocol) treatment with an investigational agent, systemic biologic therapy, or anti-cancer immunotherapy 2. Has had another malignancy within the last 5 years that is progressing, requires active treatment, or has a high likelihood of recurrence as defined in the protocol 3. Prior treatment with a Mucin 16 (MUC16)-targeted therapy 4. Ovarian Expansion cohorts only: More than 5 prior lines of systemic therapy 5. Has any condition that requires ongoing/continuous corticosteroid therapy as defined in the protocol within 1 week prior to the first dose of study drug 6. Has ongoing or recent (within 5 years) evidence of significant autoimmune conditions (where your immune system attacks your own body) that required treatment with systemic immunosuppressive treatments as defined in the protocol 7. Has untreated or active primary brain tumor, cancer that has spread to the brain, leptomeningeal disease, or spinal cord compression as defined in the protocol ...See full criteria on ClinicalTrials.gov Always talk to your doctor about whether this trial is right for you.

These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.

Original Eligibility Criteria

View original clinical language
Key Inclusion Criteria: 1. Ovarian Cancer Cohorts Only: Has histologically or cytologically confirmed diagnosis of advanced epithelial ovarian cancer (except carcinosarcoma), primary peritoneal, or fallopian tube cancer that has received at least 1 line of platinum-based systemic therapy as defined in the protocol 2. Expansion cohorts only: Has at least 1 lesion that is measurable by RECIST 1.1 as described in the protocol. 3. Has a serum CA-125 level ≥2x ULN (in screening, not applicable to endometrial cohorts) 4. Has adequate organ and bone marrow function as defined in the protocol 5. Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 6. Has a life expectancy of at least 3 months 7. Endometrial Cancer Cohorts Only: histologically confirmed endometrial cancer that has progressed or recurrent after prior anti-PD-1 therapy and platinum-based chemotherapy as described in the protocol Key Exclusion Criteria: 1. Current or recent (as defined in the protocol) treatment with an investigational agent, systemic biologic therapy, or anti-cancer immunotherapy 2. Has had another malignancy within the last 5 years that is progressing, requires active treatment, or has a high likelihood of recurrence as defined in the protocol 3. Prior treatment with a Mucin 16 (MUC16)-targeted therapy 4. Ovarian Expansion cohorts only: More than 5 prior lines of systemic therapy 5. Has any condition that requires ongoing/continuous corticosteroid therapy as defined in the protocol within 1 week prior to the first dose of study drug 6. Has ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments as defined in the protocol 7. Has untreated or active primary brain tumor, CNS metastases, leptomeningeal disease, or spinal cord compression as defined in the protocol 8. Has history of clinically significant cardiovascular disease as defined in the protocol 9. Has known allergy or hypersensitivity to cemiplimab and/or components of study drug(s). Note: Other protocol-defined Inclusion/Exclusion criteria apply

Treatments Being Tested

DRUG

REGN5668

Administer per the protocol

DRUG

Cemiplimab

Administer per the protocol

DRUG

Ubamatamab

Administer per the protocol

DRUG

Sarilumab

Administer per the protocol

DRUG

Cemiplimab + Fianlimab [Fixed Dose Combination (FDC)]

Administer per the protocol

Locations (20)

Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.

City of Hope Comprehensive Cancer Center
Duarte, California, United States
The City of Hope Orange County Lennar Foundation Cancer Center
Irvine, California, United States
Chao Family Comprehensive Cancer Center
Orange, California, United States
H. Lee Moffitt Cancer Center
Tampa, Florida, United States
Robert H. Lurie Comprehensive Cancer Center of Northwestern University
Chicago, Illinois, United States
University of Chicago Medical Center
Chicago, Illinois, United States
Massachusetts General Hospital
Boston, Massachusetts, United States
Dana Farber Cancer Institute Brookline Avenue
Boston, Massachusetts, United States
Karmanos Cancer Institute
Detroit, Michigan, United States
Memorial Sloan Kettering Cancer Center
New York, New York, United States
The Ohio State University Wexner Medical Center
Columbus, Ohio, United States
Perelman School of Medicine at the University of Pennsylvania
Philadelphia, Pennsylvania, United States
Seattle Cancer Care Alliance at South Lake Union - G3630
Seattle, Washington, United States
Universitair Ziekenhuis Leuven
Leuven, Vlaams-Brabant, Belgium
Hopital Lyon Sud
Pierre-Bénite, Auvergne-Rhône, France
Centre Georges Francois Leclerc
Dijon, Bourgogne-Franche-Comté, France
Institut Bergonie
Bordeaux, New Aquitaine, France
Centre Francois Baclesse (CFB)
Caen, Normandy, France
Institut Gustave Roussy
Villejuif, France
Hospital Clinico Universitario Santiago de Compostela
Santiago de Compostela, A Coruna, Spain

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT04590326), the sponsor (Regeneron Pharmaceuticals), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.

Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.

Authoritative Sources

The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.

Frequently Asked Questions

What is the NCT04590326 clinical trial studying?

This study is researching an investigational drug called REGN5668 : * alone or, * combined with cemiplimab (also known as REGN2810) or, * combined with both cemiplimab and fianlimab (also known as REGN3767), or * combined with ubamatamab (also known as REGN4018), with or without sarilumab. The main purposes of this study are to: * Learn about the safety and profile of any side effects from the study drugs and to determine the highest, safe dose that can be given to participants with ovarian cancer or cancer of the uterus * Look for signs that the study drugs can treat ovarian cancer or canc… The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.

Who can participate in NCT04590326?

Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.

How do I contact the trial site for NCT04590326?

Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.

Is participating in a clinical trial safe?

Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.

Where can I verify the data on this page?

Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.

How This Page Is Built

Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.

Source: ClinicalTrials.gov API v2 record for NCT04590326. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT04590326. Data: ClinicalTrials.gov."

Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.

Last updated 2026-06-07 · Data from ClinicalTrials.gov.