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KEYNOTE-B96 is the first trial of an immune checkpoint inhibitor-based treatment regimen in platinum-resistant recurrent ovarian cancer to show a statistically significant improvement in OS versus placebo plus chemotherapy with or without bevacizumab for patients whose tumors express PD-L1 and in all comers
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These data add to previous results for the primary endpoint of progression-free survival and key secondary endpoint of OS
October 16, 2025--RAHWAY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced that the Phase 3 KEYNOTE-B96 trial, also known as ENGOT-ov65, met its secondary endpoint of overall survival (OS) for the treatment of patients with platinum-resistant recurrent ovarian cancer in all comers. The trial studied KEYTRUDA® (pembrolizumab), Merck’s anti-PD-1 therapy, in combination with chemotherapy (paclitaxel) with or without bevacizumab for these patients. As previously announced, KEYNOTE-B96 met its primary endpoint of progression-free survival (PFS) in patients with platinum-resistant recurrent ovarian cancer whose tumors express PD-L1 and in all comers, as well as its secondary endpoint of OS for patients whose tumors express PD-L1, at previous interim analyses. Findings from these prior analyses will be presented in a Presidential Symposium at the upcoming European Society for Medical Oncology (ESMO) Congress 2025.
At the final analysis of the trial, the KEYTRUDA-based regimen demonstrated a statistically significant and clinically meaningful improvement in OS in all comers compared to placebo plus chemotherapy with or without bevacizumab. The safety profile of KEYTRUDA in this trial was consistent with that observed in previously reported studies; no new safety signals were identified. Results from this final analysis will be presented at an upcoming medical meeting.
“The results from the KEYNOTE-B96 trial mark the first time ever that an immune checkpoint inhibitor-based regimen has demonstrated the potential to help all patients with platinum-resistant recurrent ovarian cancer,” said Dr. Gursel Aktan, vice president, global clinical development, Merck Research Laboratories. “These women face a very poor prognosis with limited options for treatment, and this impactful news is a testament to our tireless commitment to exploring new options for patients with gynecologic cancers who face a critical unmet need.”
KEYTRUDA is not approved to treat ovarian cancer (see selected KEYTRUDA indications in the U.S. below). LYNPARZA® (olaparib), which is being jointly developed and commercialized by AstraZeneca and Merck, has three approved ovarian cancer indications in the U.S.: in first-line maintenance treatment of BRCA-mutated advanced ovarian cancer, following complete or partial response to first-line platinum-based chemotherapy; in first-line maintenance treatment of HRD-positive advanced ovarian cancer in combination with bevacizumab, following complete or partial response to first-line platinum-based chemotherapy; and in maintenance treatment of BRCA-mutated recurrent ovarian cancer, following complete or partial response to platinum-based chemotherapy. For each of these indications, patients are selected for therapy based on an FDA-approved companion diagnostic for LYNPARZA (see indications for LYNPARZA below).
As announced, data from the REJOICE-Ovarian01 trial in collaboration with Daiichi Sankyo evaluating raludotatug deruxtecan (R-DXd) in patients with platinum-resistant, high-grade ovarian primary peritoneal or fallopian tube cancer will be presented at the ESMO Congress 2025. R-DXd was recently granted Breakthrough Therapy Designation by the U.S. Food and Drug Administration (FDA) for the treatment of adult patients with platinum-resistant epithelial ovarian, primary peritoneal or fallopian tube cancers expressing CDH6 who have received prior treatment with bevacizumab, based in part on data from the REJOICE-Ovarian01 trial. R-DXd was discovered by Daiichi Sankyo and is being jointly developed by Daiichi Sankyo and Merck.
About KEYNOTE-B96/ENGOT-ov65
KEYNOTE-B96, also known as ENGOT-ov65, is a randomized, double-blind Phase 3 trial (ClinicalTrials.gov, NCT05116189) sponsored by Merck and conducted in collaboration with the European Network for Gynecologic Oncology Trial (ENGOT) groups investigating KEYTRUDA in combination with chemotherapy (paclitaxel) with or without bevacizumab compared to placebo plus chemotherapy with or without bevacizumab for the treatment of platinum-resistant recurrent ovarian cancer. The primary endpoint is PFS, and OS is a key secondary endpoint. The trial enrolled approximately 643 patients who were randomized to receive either KEYTRUDA (400 mg intravenously every six weeks for approximately two years) plus paclitaxel with or without bevacizumab, or placebo plus paclitaxel with or without bevacizumab.
About platinum-resistant ovarian cancer
Ovarian cancer often begins in the fallopian tubes or on the outer surface of the ovaries. It is the eighth most commonly diagnosed cancer and the eighth leading cause of cancer death among women worldwide. Globally, there were more than 324,000 patients diagnosed with ovarian cancer and almost 207,000 deaths from the disease in 2022. In many regions, its incidence has been increasing, with estimates projecting a 42% increase in new cases worldwide by 2040. In the U.S., it is estimated there will be approximately 20,890 patients diagnosed with ovarian cancer and about 12,730 deaths from the disease in 2025.
The primary aim of first-line treatment is to delay disease progression for as long as possible with the intent to achieve long-term remission. Between 70% and 80% of patients diagnosed with advanced ovarian cancer will experience disease progression following standard treatment with platinum-based chemotherapy regimens. Approximately 25% of these patients develop resistance within six months of completing first-line platinum-based chemotherapy, and this is defined as primary platinum-resistant ovarian cancer. Prognosis is particularly poor for these patients and treatment options are limited.
About Merck’s research in women’s cancers
Merck is advancing research aimed at expanding treatment options for certain breast and gynecologic (ovarian, cervical and endometrial) cancers, with a goal of improving outcomes for more patients affected by these diseases. Breast cancer and gynecological cancers are the first and second most commonly occurring cancer types among women worldwide, respectively, and Merck aims to give patients facing these devastating diseases options. With more than 20 clinical trials in nearly 20,000 patients around the world, Merck is driving innovative research to purposefully advance standards of care in women’s cancers. Merck’s research efforts include trials focused on evaluating its medicines in earlier stages, as well as identifying novel mechanisms and new combinations with these treatments. Merck is working to develop a portfolio and pipeline to address the impact of women’s cancers on patients, their families and communities globally.
About KEYTRUDA® (pembrolizumab) injection, 100 mg
KEYTRUDA is an anti-programmed death receptor-1 (PD-1) therapy that works by increasing the ability of the body’s immune system to help detect and fight tumor cells. KEYTRUDA is a humanized monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes which may affect both tumor cells and healthy cells.
Merck has the industry’s largest immuno-oncology clinical research program. There are currently more than 1,600 trials studying KEYTRUDA across a wide variety of cancers and treatment settings. The KEYTRUDA clinical program seeks to understand the role of KEYTRUDA across cancers and the factors that may predict a patient's likelihood of benefitting from treatment with KEYTRUDA, including exploring several different biomarkers.
About LYNPARZA® (olaparib)
LYNPARZA is a first-in-class PARP inhibitor and the first targeted treatment to potentially exploit DNA damage response (DDR) pathway deficiencies, such as BRCA mutations, to preferentially kill cancer cells. Inhibition of PARP with LYNPARZA leads to the trapping of PARP bound to DNA single-strand breaks, stalling of replication forks, their collapse and the generation of DNA double-strand breaks and cancer cell death. LYNPARZA is being tested in a range of tumor types with defects and dependencies in the DDR.
LYNPARZA, which is being jointly developed and commercialized by AstraZeneca and Merck, has a broad clinical trial development program, and AstraZeneca and Merck are working together to understand how it may affect multiple PARP-dependent tumors as a monotherapy and in combination across multiple cancer types. Independently, Merck is developing LYNPARZA in combination with its anti-PD-1 therapy, KEYTRUDA.
Merck’s focus on cancer
Every day, we follow the science as we work to discover innovations that can help patients, no matter what stage of cancer they have. As a leading oncology company, we are pursuing research where scientific opportunity and medical need converge, underpinned by our diverse pipeline of more than 25 novel mechanisms. With one of the largest clinical development programs across more than 30 tumor types, we strive to advance breakthrough science that will shape the future of oncology. By addressing barriers to clinical trial participation, screening and treatment, we work with urgency to reduce disparities and help ensure patients have access to high-quality cancer care. Our unwavering commitment is what will bring us closer to our goal of bringing life to more patients with cancer.
About Merck
At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities.