A Phase 1/2 interventional study of REGN5668 and Cemiplimab in Ovarian Cancer, Fallopian Tube Cancer and Primary Peritoneal Cancer, sponsored by Regeneron Pharmaceuticals. Recruiting at 28 sites in 5 countries. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-24.
Sponsored by Regeneron Pharmaceuticals · Phase 1/2, Interventional, and Treatment
This study is researching an investigational drug called REGN5668 :
The main purposes of this study are to:
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:
3,381 studies on the registry are indexed under Ovarian Neoplasms; 790 are open to participants now.
This study's planned enrollment of 612 is above the median of 54 across 2,548 interventional studies indexed under Ovarian Neoplasms.
Browse Ovarian Neoplasms studies →Regeneron Pharmaceuticals is the lead sponsor of 411 studies on the registry; 90 are open to participants now.
Of its 125 completed or terminated interventional studies of FDA-regulated products, 79 (63%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Key Exclusion Criteria:
Note: Other protocol-defined Inclusion/Exclusion criteria apply
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
PD-1, PD-L1 and checkpoint inhibitors
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
REGN5668 in combination with cemiplimab, or cemiplimab + fianlimab
Drug: REGN5668 · Drug: Cemiplimab · Drug: Cemiplimab + Fianlimab [Fixed Dose Combination (FDC)]
REGN5668 and ubamatamab
Drug: REGN5668 · Drug: Ubamatamab · Drug: Sarilumab
Administer per the protocol
Also known as: ubletamig
Administer per the protocol
Also known as: REGN2810, Libtayo®
Administer per the protocol
Also known as: REGN4018
Administer per the protocol
Also known as: Kevzara®
Drug pages: Cemiplimab · Fianlimab
Administer per the protocol
Incidence of Dose Limiting Toxicities (DLT)
Dose escalation phase, Module 1
Time frame: 42 days
Incidence of DLTs
Dose escalation phase, Module 2
Time frame: 21 days post combination administration
Incidence of Treatment-Emergent Adverse Events (TEAEs)
Primary: Dose escalation phase Secondary: Dose expansion phase
Time frame: Through study completion, up to 5 years
Incidence of Serious Adverse Events (SAEs)
Primary: Dose escalation phase Secondary: Dose expansion phase
Time frame: Through study completion, up to 5 years
Incidence of deaths
Primary: Dose escalation phase Secondary: Dose expansion phase
Time frame: Through study completion, up to 5 years
Incidence of laboratory abnormalities (Grade 3 or higher per National Cancer Institute Common Terminology Criteria for Adverse Events [NCI-CTCAE] version 5.0 [v5.0])
Primary: Dose escalation phase Secondary: Dose expansion phase
Time frame: Through study completion, up to 5 years
Concentrations of REGN5668 in serum when dosed alone and in combination with cemiplimab or ubamatamab
Primary: Dose escalation phase
Time frame: Through study completion, up to 5 years
Objective Response Rate (ORR) defined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 (Eisenhauer, 2009) of REGN5668 in combination with cemiplimab, cemiplimab + fianlimab, or ubamatamab (separately by cohort and combination)
Primary: Dose expansion phase
Time frame: Through study completion, up to 5 years
ORR based on RECIST 1.1
Dose escalation phase
Time frame: Through study completion, up to 5 years
Best Overall Response (BOR) based on RECIST 1.1
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Duration Of Response (DOR) based on RECIST 1.1
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Disease Control Rate (DCR) based on RECIST 1.1
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Progression-Free Survival (PFS) based on RECIST 1.1
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Cancer Antigen 125 (CA-125) change from baseline after treatment with REGN5668 in combinations with cemiplimab, cemiplimab + fianlimab, or ubamatamab (separately by cohort and combination)
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Concentration of REGN5668 in serum over time when dosed alone and in combination with cemiplimab, cemiplimab + fianlimab, or ubamatamab
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Presence or absence of anti-drug antibodies against REGN5668
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Presence or absence of anti-drug antibodies against ubamatamab
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Presence or absence of anti-drug antibodies against cemiplimab
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Presence or absence of anti-drug antibodies against fianlimab
Dose escalation and expansion phases
Time frame: Through study completion, up to 5 years
Not enrolling at this site — choose another above.
Plan to share: Yes — All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report, Analytic code
Time frame: When Regeneron has: received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry) the legal authority to share the data, and ensured the ability to protect participant privacy
Access criteria: Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf
Data sharing details ↗ · vivli.org
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