On October 16, 2025 Merck (NYSE: MRK), known as MSD outside of the United States and Canada, reported 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) (Free ESMO Whitepaper) Congress 2025.
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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 (Free ESMO Whitepaper) 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.
(Press release, Merck & Co, OCT 16, 2025, View Source [SID1234656706])