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Study of ubamatamab alone or with cemiplimab for adults with ovarian, fallopian tube, peritoneal, or endometrial cancer that has come back

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study involves patients with certain types of cancer, specifically ovarian cancer, fallopian tube cancer, cancer of the lining of the abdomen called primary peritoneal cancer, and endometrial cancer. These cancers have returned or grown after previous treatment. The study uses several medications. The main treatment being tested is ubamatamab, also known by its code name REGN4018, which is a type of medicine designed to help the immune system attack cancer cells. This medication may be given alone or together with another medication called cemiplimab, which also works with the immune system to fight cancer. Some patients may receive sarilumab, marketed as Kevzara, or tocilizumab to help manage side effects. These medications are given either through injection under the skin or through a vein.

The study has two main parts. The first part aims to find the right dose of ubamatamab when given alone or with cemiplimab by checking how safe it is and how the body processes the medication. The second part looks at how well these treatments work in shrinking or controlling the cancer. For patients with ovarian, fallopian tube, or primary peritoneal cancer, they must have received at least one previous treatment with platinum-based chemotherapy and have cancer that has returned or is no longer responding to treatment. For patients with endometrial cancer, they must have previously received treatment with a type of immune therapy and platinum-based chemotherapy, and their cancer must show a certain protein marker called MUC16 in at least one quarter of the tumor cells.

During the study, patients will receive their assigned treatment and be monitored regularly for side effects and to see how their cancer responds. Doctors will use scans and blood tests to check if the cancer is shrinking, staying the same, or growing. The study will also measure how the treatment affects quality of life and daily functioning through questionnaires. Blood samples will be taken to measure the amount of medication in the body and to check if the body develops any reaction to the medications. The study will continue until enough information is gathered about the safety and effectiveness of these treatments.

The research process

The trial runs in 10 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    Upon joining the study, your treatment will be determined based on the specific phase and group to which you are assigned.

    The study involves two main phases: a dose escalation phase and a dose expansion phase.

    You will receive treatment with ubamatamab, which is an investigational medication that targets a protein called MUC16 found on cancer cells. This medication may be given alone or in combination with another medication called cemiplimab, which works with your immune system to fight cancer.

  2. Step 2

    Treatment with ubamatamab alone

    If you are assigned to receive ubamatamab alone, you will receive this medication through an intravenous infusion, which means it will be delivered directly into your vein over a period of time.

    The dose and frequency of administration will be determined during the dose escalation phase to find the safest and most effective amount.

    Your healthcare team will monitor you closely during each infusion session.

  3. Step 3

    Treatment with ubamatamab and cemiplimab combination

    If you are assigned to receive combination treatment, you will receive both ubamatamab and cemiplimab.

    Ubamatamab will be administered through an intravenous infusion into your vein.

    Cemiplimab will also be given through an intravenous infusion. The standard preparation contains 350 mg of the medication.

    Both medications will be given according to a schedule determined by your assigned treatment group.

  4. Step 4

    Regular monitoring visits

    Throughout the study, you will attend regular monitoring visits at the study site.

    During these visits, blood samples will be collected to check your organ function, bone marrow function, and to measure medication levels in your blood.

    Your healthcare team will monitor for any side effects or unwanted reactions to the treatment.

    Laboratory tests will be performed to assess any abnormalities in your blood work.

    If you have ovarian cancer, your CA-125 levels will be measured. CA-125 is a protein that can be elevated in ovarian cancer and is used to monitor disease activity.

  5. Step 5

    Imaging assessments

    You will undergo regular imaging scans to evaluate how your cancer is responding to treatment.

    These assessments will follow standardized criteria called RECIST 1.1, which is a method used to measure tumor size and determine if the cancer is shrinking, staying the same, or growing.

    Additional assessments may be performed using iRECIST criteria, which is specifically designed to evaluate responses to immunotherapy treatments.

  6. Step 6

    Quality of life assessments

    You will be asked to complete questionnaires about your quality of life and how you are feeling.

    These questionnaires include the EORTC QLQ-C30, which assesses your general health status, quality of life, and physical functioning.

    If you have ovarian cancer, you will also complete the MOST questionnaire, which specifically asks about abdominal symptoms.

    You may also complete the EQ-5D questionnaire, which evaluates your overall health and well-being.

    These assessments help your healthcare team understand how the treatment is affecting your daily life.

  7. Step 7

    Safety monitoring

    Your healthcare team will continuously monitor you for any side effects or complications related to the treatment.

    Special attention will be given to immune-related side effects, as the medications work with your immune system.

    Any serious side effects will be documented and managed appropriately.

    Blood tests will be performed regularly to detect any significant laboratory abnormalities.

  8. Step 8

    Antibody testing

    Blood samples will be collected to test whether your body develops anti-drug antibodies against ubamatamab or cemiplimab.

    Anti-drug antibodies are proteins your immune system might create in response to the study medications.

    This testing helps researchers understand how your body responds to the treatment over time.

  9. Step 9

    Ongoing treatment period

    You will continue to receive the study medication according to your assigned treatment schedule.

    Treatment will continue as long as your cancer is not progressing and you are not experiencing unacceptable side effects.

    Your healthcare team will regularly evaluate whether continuing treatment is appropriate for you.

    The study is expected to continue until 2026, though your individual participation duration will depend on your response to treatment and overall condition.

  10. Step 10

    Response evaluation

    Your healthcare team will assess how well the treatment is working by evaluating various factors.

    This includes measuring the objective response rate, which indicates whether your tumors have shrunk.

    Other measurements include disease control rate, which shows whether the cancer is being kept under control, and progression-free survival, which measures how long you live without the cancer getting worse.

    The duration of response will be calculated if your cancer responds to treatment, showing how long the response lasts.

    If you achieve a complete response, meaning no evidence of cancer is detected, this will be documented and monitored.

Who can join the trial?

12 criteria

  • You must have been diagnosed with ovarian cancer (cancer that starts in the ovaries), fallopian tube cancer (cancer that starts in the tubes connecting the ovaries to the uterus), primary peritoneal cancer (cancer that starts in the lining of the abdomen), or endometrial cancer (cancer that starts in the lining of the uterus) that has been confirmed by examining tissue samples under a microscope
  • For ovarian, fallopian tube, or peritoneal cancer patients: You must have a blood test showing a protein called CA-125 that is at least 2 times higher than the normal upper limit
  • For ovarian, fallopian tube, or peritoneal cancer patients: You must have received at least 1 treatment that included platinum-based chemotherapy (a type of cancer treatment using platinum-containing drugs), or you cannot tolerate platinum treatment
  • For ovarian, fallopian tube, or peritoneal cancer patients: Your cancer must have returned or gotten worse after your most recent treatment
  • For ovarian, fallopian tube, or peritoneal cancer patients: There are no other standard treatments available that would likely help you
  • For endometrial cancer patients: Your cancer must have gotten worse or come back after previous treatment with anti-PD-1 therapy (a type of immunotherapy that helps your immune system fight cancer) and platinum-based chemotherapy
  • For endometrial cancer patients: Your tumor must have at least 25 percent of cancer cells that test positive for a protein called MUC16, confirmed by a special laboratory test
  • For endometrial cancer patients: You must have received between 1 and 4 previous treatment plans for your cancer
  • Your body organs and bone marrow (the soft tissue inside bones that makes blood cells) must be working well enough based on specific test results
  • Your doctors must expect that you will live for at least 3 months
  • You must be female
  • You must be an adult

Who cannot join the trial?

3 criteria

  • The study has not provided specific exclusion criteria, which are the reasons why a patient cannot take part in the research.
  • Only female patients can participate in this study. Male patients are excluded, meaning they cannot join.
  • You should discuss with your doctor whether you meet all requirements to participate in this study, as there may be additional medical reasons not listed here that could prevent your participation.
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Investigated drugs

  • Ubamatamab

    (also called REGN4018) is a bispecific antibody that works by connecting two different targets in the body. It attaches to a protein called MUC16, which is found on certain cancer cells, and also to CD3, which is found on immune cells called T-cells. By linking these together, it helps the immune system recognize and attack cancer cells that have MUC16 on their surface.

  • Cemiplimab

    is an immunotherapy medication that helps the body's immune system fight cancer. It works by blocking a protein called PD-1 on immune cells, which allows these cells to better recognize and destroy cancer cells. This medication is being tested in combination with ubamatamab to see if the two treatments work better together than ubamatamab alone.

What is already known about the treatment

  • Ubamatamab

    Ubamatamab is an experimental bispecific antibody currently being studied in clinical trials for the treatment of ovarian cancer, fallopian tube cancer, primary peritoneal cancer, and endometrial cancer that has come back after previous treatment. This medication is given as an infusion into a vein and works by connecting two specific targets: a protein called MUC16 found on cancer cells and a protein called CD3 found on immune cells, bringing them together so the immune system can recognize and attack the cancer cells. It is being tested both alone and in combination with another immunotherapy drug called cemiplimab to determine the safest and most effective dose, and researchers are evaluating how well it helps shrink tumors in patients whose cancer has returned.

  • Cemiplimab

    Cemiplimab is an immunotherapy medication that is already approved for certain types of cancer and is being studied in combination with ubamatamab in this clinical trial. It is administered as an infusion into a vein and belongs to a class of drugs called checkpoint inhibitors, which work by blocking a protein called PD-1 on immune cells, allowing the body's immune system to better recognize and fight cancer cells. In this study, cemiplimab is being combined with ubamatamab to see if the two medications work better together than ubamatamab alone in treating recurrent ovarian cancer and other cancers that express the MUC16 protein.

Investigated diseases

  • Fallopian Tube Cancer

    Fallopian tube cancer is a rare type of cancer that begins in the fallopian tubes, which are the narrow ducts that connect the ovaries to the uterus. This cancer develops when cells in the fallopian tubes start to grow abnormally and uncontrollably. The disease often spreads beyond the fallopian tubes to other parts of the pelvis and abdomen. In its early stages, it may not cause noticeable symptoms, making detection difficult. As the cancer progresses, it can cause abdominal swelling, pelvic pain, and abnormal vaginal bleeding. The disease shares many characteristics with ovarian cancer in terms of how it develops and spreads.

  • Ovarian Cancer

    Ovarian cancer is a disease that occurs when cells in the ovaries, the female reproductive organs that produce eggs, begin to grow abnormally and form tumors. The cancer can develop in different parts of the ovary, including the outer surface, the egg-producing cells, or the hormone-producing cells. As the disease progresses, cancer cells can spread to the lining of the abdomen and other organs in the pelvis. Early stages often produce few or no symptoms, which is why many cases are discovered at more advanced stages. Common symptoms that develop include bloating, abdominal discomfort, feeling full quickly when eating, and changes in bowel or bladder habits. The disease can also cause fluid buildup in the abdomen.

  • Primary Peritoneal Cancer

    Primary peritoneal cancer is a rare cancer that develops in the peritoneum, the thin layer of tissue that lines the inside of the abdomen and covers most abdominal organs. This cancer begins when cells in the peritoneal lining start to grow abnormally and multiply uncontrollably. The disease is closely related to ovarian cancer and behaves in a similar way, even though it originates in a different location. As it progresses, the cancer can spread throughout the abdominal cavity and affect multiple organs. Symptoms typically include abdominal swelling, pain or discomfort in the abdomen, and digestive problems. The disease can also cause fluid accumulation in the abdomen.

  • Endometrial Cancer

    Endometrial cancer is a type of cancer that begins in the endometrium, the inner lining of the uterus. This cancer develops when cells in the endometrial tissue start to grow abnormally and form a tumor. It is the most common type of cancer affecting the female reproductive system. The disease typically begins in the uterus and may spread to nearby tissues and organs if not detected early. The most common early symptom is abnormal vaginal bleeding, especially after menopause. As the cancer progresses, it may cause pelvic pain, pain during intercourse, and unintended weight loss.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2024-510783-23-00Protocol codeR4018-ONC-1721Estimated enrolment689 patientsSponsorRegeneron Pharmaceuticals Inc.

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