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A Phase 3 Study of GSK5733584 with drug combination in patients with platinum‑resistant ovarian cancer

Verified siteRegistered drugNo placebo
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What is this trial about?

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

The study focuses on ovarian cancer that no longer responds to platinum‑based chemotherapy, a condition known as platinum‑resistant. Participants will receive either the investigational drug mocertatug rezetecan (also called Mo‑Rez) given by infusion, or a physician‑chosen standard therapy selected from a group of commonly used medicines such as topotecan, paclitaxel, pembrolizumab, doxorubicin, gemcitabine and bevacizumab.

The purpose of the trial is to evaluate the clinical efficacy of Mo‑Rez compared with the physician’s choice of standard of care in participants with platinum‑resistant ovarian cancer.

After giving informed consent, participants are randomly assigned—meaning by chance—to one of the two treatment groups. The assigned medication is administered through an intravenous line on a regular schedule. Throughout the study, participants attend clinic visits for safety checks, blood tests, and imaging scans (pictures of the inside of the body) to monitor tumor changes. They also complete questionnaires that assess symptoms and overall quality of life. The study continues until a predefined end point is reached or the participant and physician decide to stop treatment.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization

    After you join the study, you are assigned a study number and the computer randomly places you into one of two groups.

    One group receives the investigational drug gsk5733584 (dose: 5.8 mg per kilogram of body weight, given by intravenous infusion).

    The other group receives the physician’s choice of a standard treatment, which may be one of the following intravenous drugs:

    topotecan – 4 mg per square meter,

    paclitaxel – 80 mg per square meter,

    pembrolizumab (keytruda) – 400 mg,

    doxorubicin (caelyx) – 40 mg per square meter,

    gemcitabine – 1000 mg per square meter,

    bevacizumab (zirabev) – 10 mg per kilogram.

  2. Step 2

    Baseline assessments

    Before the first infusion, you undergo a series of tests to document your health status.

    These include physical measurements, blood laboratory tests, electrocardiogram (ecg), and imaging scans to evaluate the extent of ovarian cancer.

    Questionnaires about quality of life and symptoms are also completed.

  3. Step 3

    First infusion

    On the day of the first treatment, the assigned medication is prepared and administered through an intravenous line.

    The infusion is performed in a clinical setting under medical supervision.

    The dose described in the randomization step is given during this session.

  4. Step 4

    Subsequent infusions

    You return for additional infusion visits according to the schedule determined by the study protocol.

    At each visit, the same medication and the same dose (based on body surface area or weight) are administered.

    The interval between infusions is consistent with standard practice for the selected drug, but exact timing follows the trial’s predefined schedule.

  5. Step 5

    Safety monitoring

    Before and after each infusion, vital signs (blood pressure, pulse, temperature) are checked.

    Blood samples are taken to monitor laboratory values such as blood counts and chemistry.

    Any side effects are recorded using patient‑reported questionnaires and clinical assessments.

  6. Step 6

    Disease evaluation

    Periodic imaging scans are performed to assess tumor size and determine whether the disease is progressing.

    The same criteria (recist 1.1) are used throughout the study to ensure consistent evaluation.

  7. Step 7

    Dose adjustment

    If side effects reach a level that requires a change, the study physician may delay the next infusion or reduce the dose.

    Any modification follows the predefined rules of the trial protocol.

  8. Step 8

    Treatment discontinuation

    Treatment stops when any of the following occurs: disease progression confirmed by imaging, unacceptable toxicity, withdrawal from the study, or completion of the planned number of cycles.

  9. Step 9

    Follow‑up

    After treatment ends, you continue to be seen at scheduled intervals for safety checks and survival monitoring.

    Blood tests, imaging, and quality‑of‑life questionnaires are repeated to collect long‑term data.

Who can join the trial?

12 criteria

  • Age: You must be at least 18 years old and able to give legal consent for the study.
  • Organ function: Your blood and kidney tests must be normal enough, including white blood cells (ANC ≥ 1500 per microliter), platelets (≥ 100,000 per microliter), hemoglobin (≥ 9.0 g/dL), kidney filtration rate (eGFR ≥ 30 mL/min), blood protein albumin (≥ 2.5 g/dL), and clotting tests (INR/PT/aPTT) that are within safe limits, especially if you are not on blood‑thinning medication.
  • Epithelial ovarian cancer (or related cancers of the lining of the abdomen or fallopian tubes) that is confirmed by a tissue test to be one of the following types—high‑grade serous, high‑grade endometrioid, clear‑cell, or carcinosarcoma—and that no longer responds to platinum‑based chemotherapy (meaning the cancer grew back within 3‑6 months after the last platinum dose).
  • Previous cancer treatments: You must have had at least 1 but no more than 4 earlier rounds of systemic (whole‑body) anti‑cancer therapy. Different types of treatment are counted as one “line” unless a new drug from a different class was added.
  • Required prior drugs: You should have already received the following medicines unless you have a medical reason not to:
    • Mirvetuximab (if your tumor shows strong FRα protein on the cells),
    • Bevacizumab (unless you have conditions like uncontrolled high blood pressure, recent bleeding, or certain wound‑healing problems),
    • PARP inhibitor (PARPi) if you have a harmful BRCA gene mutation and responded to platinum chemotherapy.
    • Measurable tumor lesion: You need to have at least one tumor spot that can be measured on scans according to the RECIST 1.1 criteria (a standard way doctors define tumor size and changes).
    • Tumor tissue sample: You must provide a formalin‑fixed, paraffin‑embedded (FFPE) tumor sample that is large enough for the lab to test for three markers—B7‑H4, FRα, and PD‑L1. The sample should come from a recent, non‑irradiated site and cannot be a fine‑needle aspirate or bone marrow sample.
    • Contraception and pregnancy: You must be a female who is not pregnant or breastfeeding. You need to use a highly effective birth‑control method (failure rate < 1 % per year) starting at least 30 days before the first study dose, continue during the study, and keep using it for at least 8 months after the last dose. You also agree not to donate eggs during this time.
    • Pregnancy test: A very sensitive urine or blood pregnancy test must be negative within 24 hours before the first dose of the study drug.
    • ECOG performance status: Your overall daily activity level must be good, scored as 0 (fully active) or 1 (restricted in physically strenuous activity but ambulatory).

Who cannot join the trial?

28 criteria

  • Has primary platinum‑refractory ovarian cancer, meaning the cancer did not respond to or got worse within 3 months after the first round of platinum‑based chemotherapy.
  • For patients who would receive bevacizumab as part of the physician’s choice regimen: has a history of serious blood‑vessel problems (such as uncontrolled high blood pressure or blood clots), abnormal connections (fistula), bowel problems (rectosigmoid involvement or bowel blockage), poor wound healing, bleeding disorders (coughing up blood, nosebleeds, lung bleeding, or problems with blood clotting), kidney disease with large protein loss (nephrotic syndrome) or significant protein in urine, jaw bone loss (osteonecrosis of the jaw), or known allergy to the medication.
  • Had any major surgery within 28 days before the first study dose or received focused radiation therapy within 21 days before the first dose.
  • Received any experimental drug within 30 days before the first dose.
  • Received any chemotherapy, hormone therapy, targeted therapy, immunotherapy, biologic therapy, or other anti‑cancer drug within 30 days (or within five drug half‑lives, whichever is shorter) before the first dose, or needs to keep taking those drugs during the study.
  • Previously treated with topoisomerase I inhibitors (e.g., topotecan) or antibody‑drug conjugates that contain a TOP1 inhibitor, or with therapy that targets B7‑H4.
  • Received any live vaccine within 30 days before the first dose.
  • Taken drugs that block the transport proteins P‑gp, BCRP, or OATP1B1/1B3 within 7 days before the first dose (P‑gp inducers must be stopped at least 14 days before the first dose).
  • Received a blood transfusion (red cells or platelets) or growth‑factor medicines (such as G‑CSF, GM‑CSF, or erythropoietin) within 14 days before the first dose.
  • Has HIV infection and meets any of the following: detectable HIV‑1 RNA ≥ 50 copies/mL within the last 3 months; no recent CD4 count measurements; CD4 count ≤ 350 cells/mm³ in the past year; recent changes in antiretroviral therapy; history of HIV‑related lymphoma within 5 years; or received an HIV‑1 vaccine within 90 days. (Well‑controlled HIV without AIDS‑defining illness may be allowed.)
  • Has a liver enzyme (ALT) level more than 2.5 times the normal upper limit, or more than 5 times normal if liver metastases are present.
  • Has another cancer (other than the ovarian cancer being studied) that has gotten worse or needed treatment in the past 36 months, except for certain skin cancers or in‑situ cancers that have been completely removed.
  • Has a total bilirubin level more than 1.5 times the normal upper limit (except patients with Gilbert’s syndrome who meet specific bilirubin criteria).
  • Has cirrhosis or unstable liver or bile‑duct disease (such as fluid buildup in the abdomen, confusion, clotting problems, low blood protein, enlarged veins in the esophagus or stomach, or persistent yellowing of the skin). Stable, non‑cirrhotic liver disease may be allowed.
  • Has active hepatitis B surface antigen (HBsAg) or core antibody (HBcAb) at screening unless the person is on effective antiviral therapy for at least 14 days, has suppressed HBV DNA, and has been tested for hepatitis D virus.
  • Has a positive hepatitis C antibody test unless a follow‑up RNA test shows no active virus (indicating past, resolved infection).
  • Has a positive hepatitis C RNA test (indicating active infection).
  • Has a corrected QT interval (QTcF) longer than 470 milliseconds, which can increase the risk of abnormal heart rhythm.
  • Has a history within the past year of significant heart problems, such as uncontrolled cardiac disease, recent heart attack, severe heart failure (NYHA Class III or IV), or serious irregular heartbeat not controlled by medication.
  • For participants receiving pegylated liposomal doxorubicin (PLD) only: has a baseline left‑ventricular ejection fraction (LVEF) below 50% or below the normal range for the site.
  • Has any active kidney problem (infection, need for dialysis, or other serious kidney condition) that could affect safety. Managed kidney blockage may be allowed.
  • Has ever had an allogeneic or autologous bone‑marrow transplant or any solid‑organ transplant.
  • Is known to be allergic to any component of the study drug or its inactive ingredients, or has another allergy that the investigator believes makes participation unsafe.
  • Has untreated brain or central‑nervous‑system (CNS) metastases, or brain/CNS metastases that have grown or are causing new neurological symptoms. Previously treated and stable brain metastases may be allowed if steroids have been stopped for at least 14 days.
  • Has current interstitial lung disease (ILD) or pneumonitis, or a past history of these lung inflammatory conditions.
  • Has ongoing side effects from previous therapy that have not improved to mild (Grade 1) or baseline level, except for hair loss, hearing loss, skin color change, hormone replacement therapy, or mild nerve pain (Grade 2).
  • Has any serious or unstable medical condition (including infection), or serious or unstable psychiatric disorder, or any laboratory abnormality that could interfere with safety, consent, or ability to follow study procedures.
  • For participants planned to receive pembrolizumab as part of the physician’s choice regimen: has had a severe immune‑related adverse event (Grade 3 or higher), severe immune‑mediated neurological problems (such as myasthenia gravis, encephalitis, Guillain‑Barré syndrome, or transverse myelitis), severe skin reaction (such as Stevens‑Johnson syndrome, toxic epidermal necrolysis, or DRESS syndrome), or myocarditis (inflammation of the heart muscle).
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Investigated drugs

  • Topotecan

    is a chemotherapy medicine that works by stopping cancer cells from copying their DNA, which prevents them from growing and dividing. In this trial it is given through an IV line directly into the bloodstream.

  • Paclitaxel

    is another chemotherapy drug that blocks the formation of structures needed for cancer cells to split. By keeping these structures from working, it stops the tumor cells from multiplying. It is also administered by IV infusion.

  • Pembrolizumab

    is an immunotherapy that helps the body’s own immune system see and attack cancer cells. It does this by blocking a protein that normally keeps the immune response in check. This medication is given by IV infusion.

  • Doxorubicin (pegylated liposomal)

    is a form of chemotherapy that is packaged in tiny fat‑like particles (liposomes) to reach the tumor while causing fewer side effects. It works by damaging the DNA inside cancer cells, stopping them from growing. It is delivered through an IV.

  • Gemcitabine

    is a chemotherapy drug that mimics building blocks of DNA, causing the cancer cells to stop making new DNA and die. It is given by IV infusion.

  • Bevacizumab

    is a targeted therapy that blocks a signal that tells tumors to grow new blood vessels. Without these vessels, the tumor gets less oxygen and nutrients, which can slow its growth. It is administered intravenously.

What is already known about the treatment

  • Topotecan

    This medication is given by intravenous infusion as a solution for infusion. It is an approved chemotherapy drug that is used to treat ovarian cancer and other solid tumors. It works by blocking an enzyme called topoisomerase I, which prevents cancer cells from copying their DNA. Topotecan belongs to the class of topoisomerase inhibitors.

  • Paclitaxel

    Paclitaxel is administered by intravenous infusion in a solution form. It is a widely used, approved chemotherapy for ovarian cancer and several other cancers. The drug stabilizes tiny structures called microtubules, stopping cancer cells from dividing. It is classified as a taxane, a type of mitotic inhibitor.

  • Pembrolizumab

    Pembrolizumab is delivered by intravenous infusion as a concentrated solution. It is an approved immunotherapy used for many cancers, including ovarian cancer in certain situations. It blocks the PD‑1 protein on immune cells, helping the body’s immune system recognize and attack cancer. This drug is classified as an immune checkpoint inhibitor.

  • Doxorubicin (pegylated liposomal)

    This formulation is given by intravenous infusion as a solution for infusion. It is an approved chemotherapy for ovarian cancer and other tumors. The drug inserts itself between DNA strands and creates free radicals that damage cancer cells. It belongs to the anthracycline class of antibiotics.

  • Gemcitabine

    Gemcitabine is administered by intravenous infusion as a solution for infusion. It is an approved chemotherapy used to treat ovarian cancer and other solid tumors. The drug mimics a building block of DNA, gets incorporated into the DNA chain, and stops the cancer cell from copying its genetic material. It is classified as a nucleoside analog.

  • GSK5733584

    GSK5733584 is supplied as a powder that is reconstituted for intravenous infusion. It is currently an investigational drug being studied in clinical trials and has no approved medical use yet. The exact way it works is still under investigation, but it is being tested as a potential new cancer therapy. It is considered an experimental investigational agent.

Investigated diseases

  • Ovarian neoplasm

    A malignant growth that originates in the ovary, the organ that produces eggs and hormones. It can arise from the surface cells, germ cells, or supporting tissue of the ovary. The tumor often expands within the ovary and may spread to the surrounding pelvic structures. Cancer cells can travel through the abdominal cavity, leading to involvement of the peritoneum and other organs. Over time, the disease may recur after initial treatment.

  • Platinum‑resistant ovarian cancer

    A form of ovarian cancer that no longer responds to platinum‑based chemotherapy after initial therapy. The cancer continues to grow or recur within six months of completing platinum treatment. It may spread within the pelvis and abdomen, affecting surrounding tissues. The disease can persist despite standard drug regimens, requiring alternative therapeutic approaches. It often presents with increasing tumor burden and symptoms related to abdominal involvement.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523361-25-00Protocol code224031Estimated enrolment450 patientsSponsorGlaxosmithkline Research & Development Limited

sourced from the EU Clinical Trials Register and site verification

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