KEYTRUDA Plus Chemotherapy Improves Survival in Platinum-Resistant Ovarian Cancer

Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced results from the final analysis of the pivotal Phase 3 KEYNOTE-B96 trial, also known as ENGOT-ov65, showing that KEYTRUDA (pembrolizumab), Merck's anti-PD-1 therapy, in combination with chemotherapy (paclitaxel) with or without bevacizumab significantly improved overall survival (OS), a key secondary endpoint, for patients with platinum-resistant recurrent ovarian cancer regardless of PD-L1 status versus paclitaxel with or without bevacizumab alone, the most active standard of care control arm for patients who are bevacizumab-eligible.

At the final analysis, after a median follow-up of 32.7 months (range, 26.1-44.1), KEYTRUDA plus paclitaxel with or without bevacizumab demonstrated a statistically significant and clinically meaningful improvement in OS in all comers, reducing the risk of death by 18% (HR=0.82 [95% CI, 0.69-0.97]; p=0.0115) compared to paclitaxel with or without bevacizumab alone. For patients who received the KEYTRUDA regimen, median OS was 17.7 months versus 14.0 months for patients receiving the placebo regimen. The observed OS is among the longest reported in any clinical trial for platinum-resistant recurrent ovarian cancer, showing a clinically meaningful benefit of this regimen relative to the most active standard of care control arm, weekly paclitaxel with bevacizumab in bevacizumab-eligible patients.

The data were presented during a Best Oral Session at the European Society of Gynaecological Oncology (ESGO) 2026 Congress (abstract #526).

As previously reported at the European Society for Medical Oncology (ESMO) Congress 2025, KEYTRUDA plus paclitaxel with or without bevacizumab met its primary endpoint of progression-free survival (PFS) in the all comers population of patients with platinum-resistant recurrent ovarian cancer, as well as in patients whose tumors express PD-L1 (Combined Positive Score [CPS] =1). The KEYTRUDA regimen also met its key secondary endpoint of OS in patients with platinum-resistant recurrent ovarian cancer whose tumors express PD-L1 (CPS =1).

The director of the Gynecologic Oncology Program at the European Institute of Oncology in Milan, Italy, stated that patients with platinum-resistant ovarian cancer show reduced responses to traditional treatment regimens and may experience poor overall survival. These results build on prior data from the KEYNOTE-B96 trial and further define the clinical impact of this pembrolizumab-based regimen in appropriate patients with platinum-resistant recurrent ovarian cancer.

Additionally, the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion recommending approval of KEYTRUDA in combination with paclitaxel with or without bevacizumab for the treatment of platinum-resistant epithelial ovarian, fallopian tube or primary peritoneal carcinoma in adults whose tumors express PD-L1 (CPS =1), and who have received one or two prior systemic treatment regimens.

In February, KEYTRUDA plus paclitaxel with or without bevacizumab was approved by the U.S. Food and Drug Administration (FDA) to treat adult patients with platinum-resistant epithelial ovarian, fallopian tube or primary peritoneal carcinoma whose tumors express PD-L1 (CPS =1) as determined by an FDA-authorized test, and who have received one or two prior systemic treatment regimens based on previous data from the KEYNOTE-B96 trial.

A vice president of global clinical development at Merck Research Laboratories stated that results from the final analysis of KEYNOTE-B96, including overall survival data in the all comers population, demonstrate the continued clinical benefit of KEYTRUDA plus paclitaxel with or without bevacizumab for certain patients with platinum-resistant recurrent ovarian cancer. Taken together, the recent FDA approval and CHMP positive opinion underscore the company's commitment to the ovarian cancer community and ongoing focus on delivering therapies that can help patients with unmet needs across women's cancers.

KEYNOTE-B96, also known as ENGOT-ov65, is a multicenter, randomized, double-blind placebo-controlled 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, Merck's anti-PD-1 therapy, in combination with chemotherapy (paclitaxel) with or without bevacizumab compared to placebo plus paclitaxel with or without bevacizumab for the treatment of platinum-resistant recurrent ovarian cancer. The primary endpoint is PFS, as assessed by investigator according to Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1), and OS is a key secondary endpoint. The trial enrolled 643 patients with epithelial ovarian, fallopian tube or primary peritoneal carcinoma.