Academisch Ziekenhuis Leiden
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Leiden, The Netherlands
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Study of gsk5733584 with bevacizumab versus standard drug combination in patients with platinum-sensitive ovarian cancer
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What is this trial about?
A plain-language summary of the goals, design and what participants do
The trial involves people with ovarian cancer, a disease that begins in the ovaries. Two treatment approaches are being compared. One uses the experimental drug mocertatug rezetecan together with the antibody therapy bevacizumab. The other uses a standard chemotherapy regimen called a platinum doublet, which combines the chemotherapy agents carboplatin and paclitaxel, also given with bevacizumab.
The purpose of the study is to determine whether the new combination can keep the cancer from growing longer than the standard chemotherapy. Participants are randomly assigned to one of the two groups and receive medicines by an IV (a needle placed in a vein) every few weeks for several cycles, followed by continued treatment with bevacizumab alone to help maintain the response. During the study, doctors will check health status, draw blood, and perform imaging scans such as CT scans, which are pictures that show the size of the tumor.
After the treatment period, participants continue to be seen for several months with regular check‑ups to monitor for side effects and to look for any signs that the cancer has returned. These visits include simple questions about how they feel, blood tests, and repeat scans to assess the condition of the disease.
The research process
The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.
Who can join the trial?
12 criteria
- Must be at least 18 years old and legally able to give consent.
- Must be able to sign a signed informed consent form.
- Must have an ECOG performance status of 0 or 1 (meaning fully active or able to do light work).
- Must have adequate organ function, including: white blood cell count (ANC) ≥ 1500/µL, platelets ≥ 100,000/µL, hemoglobin ≥ 9.0 g/dL, kidney function (eGFR) ≥ 30 mL/min, albumin ≥ 2.5 g/dL, and normal blood‑clotting tests (INR/PT ≤ 1.5 if not on blood thinners, or within therapeutic range if on them).
- Must have a confirmed diagnosis of epithelial ovarian, primary peritoneal, or fallopian‑tube cancer that is high‑grade serous, high‑grade endometrioid, clear cell carcinoma, or carcinosarcoma, based on tissue examination.
- Must have cancer that has come back or gotten worse after 1 to 2 previous lines of systemic cancer therapy, as shown by scan results (according to RECIST 1.1) or the doctor’s assessment; a rise in the CA‑125 blood test alone is not enough.
- Must have platinum‑sensitive disease, meaning the cancer returned more than 6 months after the last platinum‑based chemotherapy, and be suitable for platinum doublet chemotherapy with bevacizumab.
- Must have test results for BRCA1 or BRCA2 gene mutations (tumor or inherited). If a harmful BRCA mutation is present, the patient must already have received PARPi (PARP inhibitor) maintenance therapy, alone or with bevacizumab, if it was available.
- Must provide a FFPE (formalin‑fixed, paraffin‑embedded) tumor tissue sample that can be tested for B7‑H4 expression before randomization; the sample must come from a recent, non‑irradiated site and cannot be a fine‑needle aspirate, bone marrow, bone, or cell block.
- Must agree to use effective contraception according to local rules.
- Must not be pregnant or breastfeeding. If of child‑bearing potential, must be either post‑menopausal or use a highly effective contraceptive method (<1% failure rate) starting at least 30 days before treatment, continuing during the study, and for at least 8 months after the last dose, and must agree not to donate eggs.
- Must have a negative pregnancy test (urine or blood) within 24 hours before the first dose; if the urine test is unclear, a blood test must be done, and a positive result excludes participation.
Who cannot join the trial?
34 criteria
- Planning to have a second tumor‑removing surgery (called interval secondary cytoreductive surgery) for recurrent ovarian cancer during the initial treatment period.
- Having another cancer (other than the ovarian cancer being studied) that has gotten worse or needed treatment in the past 3 years, except for simple skin cancers that were completely removed.
- Having ever received a bone‑marrow transplant or any solid‑organ transplant.
- Being known to be allergic to any part of the study medicines or related substances, making participation unsafe.
- Having untreated brain or central‑nervous‑system (CNS) metastases, or brain/CNS metastases that have progressed.
- Having current interstitial lung disease (ILD) or pneumonitis, or a past history of these non‑infectious lung problems.
- Having ongoing side‑effects from previous cancer treatment that have not improved to mild (grade ≤ 1) or back to the condition before treatment, except for minor issues such as hair loss or mild nerve tingling.
- Having any serious or unstable medical condition (including infection) or serious psychiatric disorder that could affect safety or the ability to follow study procedures.
- Having significant wound‑healing problems or wounds that have not fully healed.
- Having a history of a hole or tear in the gastrointestinal tract, a tracheoesophageal fistula (an abnormal connection between the windpipe and esophagus), any grade 4 fistula, a gastrointestinal or abdominal abscess within the past 6 months, or osteonecrosis of the jaw (bone death in the jaw).
- Having evidence that the rectum‑sigmoid colon is involved with cancer, seen on pelvic exam, CT scan, or symptoms of bowel blockage.
- Having significant bleeding problems, a strong tendency to bleed, or bleeding tumors within the past 30 days.
- Having a congenital bleeding disorder, an acquired clotting problem, or recent lung bleeding (more than about a half‑teaspoon of blood) within the past 3 months.
- Having had major surgery within 28 days before the study start or focal radiotherapy within 21 days before the study start.
- Having taken any investigational (experimental) drug within 30 days before the study start.
- Having ever been treated with a Topo1 inhibitor (such as topotecan) or an antibody‑drug conjugate containing a Topo1 inhibitor, or with B7‑H4‑targeted therapy.
- Having received any chemotherapy, hormone therapy, targeted therapy, immunotherapy, or other anti‑cancer drug within 30 days (or within 5 half‑lives, whichever is shorter) before the study start, or needing to continue those drugs during the study.
- Having taken drugs that block the transport proteins P‑gp, BCRP, or OATP1B1/1B3 within 7 days before the study start, or drugs that increase P‑gp activity within 14 days before the study start.
- Having received any live vaccine (a vaccine that contains a weakened form of the germ) within 30 days before the study start. (mRNA and adenoviral COVID‑19 vaccines are not considered live.)
- Having received any blood product transfusion (including red cells or platelets) or colony‑stimulating factors (such as G‑CSF, GM‑CSF, or erythropoietin) within 14 days before the study start.
- Having HIV infection that is not well‑controlled (high viral load, low CD4 count, recent changes in therapy, recent HIV‑related cancer, or recent HIV vaccine), as defined by several specific laboratory and clinical criteria.
- Having an ALT level (a liver enzyme) greater than 2.5 times the normal upper limit, or greater than 5 times the normal limit if liver metastases are present.
- Having a total bilirubin level (a measure of liver function) greater than 1.5 times the normal upper limit, unless the increase is due to Gilbert’s syndrome with normal direct bilirubin.
- Having cirrhosis or unstable liver or bile‑duct disease (e.g., fluid in the abdomen, confusion, clotting problems, low albumin, varices, or persistent jaundice), unless the condition is well‑controlled and not caused by the cancer.
- Testing positive for hepatitis B surface antigen (HBsAg) unless you are already on effective antiviral therapy (such as tenofovir or entecavir) for at least 7 days, have undetectable HBV DNA, and have a negative HDV antibody test.
- Testing positive for hepatitis B core antibody (HBcAb) unless you have undetectable HBV DNA and a negative HBsAg test.
- Testing positive for hepatitis C antibody unless an HCV RNA test is negative, showing past resolved infection.
- Having a QTcF interval (a heart‑electrical timing measurement) longer than 470 milliseconds.
- Having a history within the past 12 months of serious or uncontrolled heart disease, a heart attack, severe heart failure (New York Heart Association class III or IV), or a significant irregular heartbeat that is not controlled by medication.
- Having a baseline left ventricular ejection fraction (LVEF – a measure of how well the heart pumps) less than 50 % or below the laboratory’s lower normal limit.
- Having clinically significant abnormal blood pressure or uncontrolled hypertension, including hypertensive crisis, hypertensive encephalopathy, or recent changes in blood‑pressure medication within 14 days before the study start.
- Having any active kidney problem (such as infection, need for dialysis, or other serious kidney condition) that could affect safety.
- Having a history of nephrotic syndrome or grade 3 proteinuria (high protein in the urine).
- Having proteinuria during screening defined as a dipstick result of 2+ or higher and a 24‑hour urine collection showing 1 gram or more of protein; if the 24‑hour collection is less than 1 gram, participation is allowed.
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Investigated drugs
Carboplatin
is a chemotherapy drug given through an IV. In this study it is used as part of the standard “platinum doublet” treatment that is being compared to the new therapy. Its purpose is to help stop the growth of ovarian cancer cells.
Bevacizumab
(brand name Zirabev) is a medication that blocks a protein that helps tumors grow new blood vessels. It is given by IV and is used in both treatment groups in the trial, either together with the new drug or with the standard chemotherapy, to see if it improves outcomes for patients with platinum‑sensitive ovarian cancer.
GSK5733584
is an experimental drug, also called Mocertatug Rezetecan, that is being tested for the first time in people with ovarian cancer. It is given by IV and is combined with bevacizumab in the experimental arm of the study to see if this new combination works better than the standard chemotherapy.
Doxorubicin
(available as Caelyx, a pegylated liposomal formulation) is a chemotherapy medication delivered by IV. In this trial it serves as a comparator drug, helping researchers understand how the new treatment compares to other established chemotherapy options.
Gemcitabine
is an IV chemotherapy drug that interferes with cancer cell DNA, slowing their growth. It is included as one of the comparator agents in the study, providing a reference point for evaluating the effectiveness of the new therapy.
Paclitaxel
is a chemotherapy drug given through an IV that stops cancer cells from dividing. It is part of the standard platinum‑based chemotherapy regimen used as a comparator in the trial, allowing researchers to compare the new drug combination against this widely used treatment.
What is already known about the treatment
Carboplatin
This medication is given as an intravenous injection in a clear solution that is infused into a vein. It is an approved chemotherapy drug widely used for ovarian and other cancers and is listed in medical literature as a standard treatment. It works by attaching to DNA inside cancer cells, which stops the cells from copying their genetic material and leads to their death. Carboplatin belongs to the class of platinum‑based antineoplastic agents.
Bevacizumab
Bevacizumab is administered by slow intravenous infusion of a sterile solution. It is an approved drug for many solid tumors, including ovarian cancer, and is well documented in the medical literature. The drug blocks a protein called VEGF that tumors need to grow new blood vessels, thereby starving the tumor of nutrients. It is classified as a monoclonal antibody and an angiogenesis inhibitor.
Doxorubicin Hydrochloride (Liposomal, Caelyx)
This form of doxorubicin is given as an intravenous infusion of a liposome‑encapsulated solution. It is an established chemotherapy agent used for ovarian and other cancers, with extensive clinical data supporting its use. The drug slips into cancer cells and inserts itself between DNA strands, preventing the DNA from being read and also creates reactive molecules that damage the cell. It is classified as an anthracycline antibiotic antineoplastic.
Gemcitabine Hydrochloride
Gemcitabine is delivered by intravenous infusion of a clear solution. It is an approved chemotherapy drug for several cancers, including ovarian cancer, and is widely referenced in the medical literature. The medication mimics a building block of DNA, gets incorporated into the DNA chain, and stops the cancer cell from copying its DNA, leading to cell death. It belongs to the antimetabolite class of anticancer agents.
Paclitaxel
Paclitaxel is administered as an intravenous infusion of a sterile solution. It is a standard, approved chemotherapy drug for ovarian and many other cancers, with a long history of use in clinical practice. The drug binds to tiny structures called microtubules inside cells, keeping them rigid and preventing the cells from dividing properly. Paclitaxel is classified as a taxane and a mitotic inhibitor.
GSK5733584
This experimental drug is supplied as a powder that is mixed with liquid and given by intravenous infusion. It is currently under investigation and has not yet received regulatory approval, so it appears mainly in early‑stage clinical trial reports. While the exact molecular target is still being studied, the drug is designed to interfere with pathways that help cancer cells grow. It is considered an investigational anticancer agent pending further research.
Investigated diseases
Primary serous ovarian carcinoma - A cancer that begins in the cells lining the surface of the ovary. It initially forms a tumor that can grow outward and involve nearby pelvic structures. As it advances, cancer cells often spread to the lining of the abdomen, causing fluid buildup. Later, tumor cells may travel through blood or lymph vessels to reach distant organs. The disease typically moves from a localized growth to a more widespread involvement of the body.
Trial detailsLast updated 29 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523366-24-00Protocol code224040Estimated enrolment508 patientsSponsorGlaxosmithkline Research & Development Limited
sourced from the EU Clinical Trials Register and site verification
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