On May 15, 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 primary endpoint of progression-free survival (PFS) for the treatment of patients with platinum-resistant recurrent ovarian cancer whose tumors expressed PD-L1 and in all comers (Press release, Merck & Co, MAY 15, 2025, View Source [SID1234653174]). The study also met a secondary endpoint of overall survival (OS) in patients whose tumors express PD-L1. The study is evaluating KEYTRUDA (pembrolizumab), Merck’s anti-PD-1 therapy, in combination with chemotherapy (paclitaxel) with or without bevacizumab for these patients. The trial is continuing and OS for the full study population will be evaluated at a future analysis.

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At pre-specified interim analyses conducted by an independent Data Monitoring Committee, the KEYTRUDA-based regimen demonstrated a statistically significant and clinically meaningful improvement in PFS regardless of PD-L1 status compared to placebo plus chemotherapy with or without bevacizumab. The study also showed a statistically significant and clinically meaningful improvement in OS in patients whose tumors express PD-L1 (Combined Positive Score [CPS] ≥1) 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 will be presented at an upcoming medical meeting and shared with regulatory authorities worldwide.

"This marks the first time a KEYTRUDA-based regimen has shown the ability to help certain patients with platinum-resistant ovarian cancer live longer, and the first time an immune checkpoint inhibitor-based regimen has demonstrated an overall survival benefit in ovarian cancer," said Dr. Gursel Aktan, vice president, global clinical development, Merck Research Laboratories. "The positive results from this trial add to the growing body of evidence supporting the potential benefit of KEYTRUDA across gynecological cancers, including this difficult-to-treat form of ovarian cancer for which patients are in need of new options."

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). In 2024, Merck announced the initiation of the Phase 2/3 REJOICE-Ovarian01 trial evaluating raludotatug deruxtecan (R-DXd), an investigational potential first-in-class CDH6 directed DXd antibody-drug conjugate discovered by Daiichi Sankyo and being jointly developed with Merck, in patients with platinum-resistant ovarian cancer.

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 an estimated 643 patients who were randomized to receive:

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 ovarian cancer

Ovarian cancer often begins in the fallopian tubes or on the outer surface of the ovaries. It is the third most common gynecologic malignancy and seventh most common cancer in women worldwide. Globally, there were approximately 324,603 patients diagnosed with ovarian cancer and about 206,956 deaths from the disease in 2022. 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.