Keytruda Becomes First Immunotherapy to Extend Survival in Platinum-Resistant Ovarian Cancer
FDA approves pembrolizumab for a subset of ovarian cancer patients after Phase 3 KEYNOTE-B96 trial shows the first overall survival benefit ever demonstrated by an immunotherapy in this setting.
The U.S. Food and Drug Administration approved pembrolizumab (Keytruda) in combination with paclitaxel, with or without bevacizumab, on February 10, 2026, for adult patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma whose tumors express PD-L1. The decision marks the first time an immune checkpoint inhibitor regimen has shown a statistically significant overall survival benefit in a Phase 3 ovarian cancer trial, according to the FDA’s approval summary.
Ovarian cancer remains among the deadliest gynecologic malignancies in part because most patients are diagnosed at advanced stages and many eventually develop resistance to platinum-based chemotherapy — the backbone of first-line treatment. Approximately 19,000 Americans receive an ovarian cancer diagnosis each year, and platinum-resistant disease carries a particularly poor prognosis, with median survival historically measured in months.
Trial Data
The approval was supported by the Phase 3 KEYNOTE-B96/ENGOT-ov65 trial, which enrolled 643 patients with platinum-resistant recurrent ovarian cancer who had received one or two prior systemic treatment regimens. Patients were randomized in a double-blind, placebo-controlled design to receive either pembrolizumab or placebo alongside weekly paclitaxel, with bevacizumab added at the investigator’s discretion.
In patients whose tumors expressed PD-L1 (Combined Positive Score of 1 or greater) — representing 72 percent of enrolled participants — the pembrolizumab regimen reduced the risk of disease progression or death by 28 percent (hazard ratio 0.72; p=0.0014), extending median progression-free survival from 7.2 months to 8.3 months, according to CancerNetwork’s reporting on the trial data. More significantly, median overall survival in that biomarker-selected group rose from 14.0 months to 18.2 months, a 24 percent reduction in the risk of death (hazard ratio 0.76).
Final overall survival data from the broader all-comers population were presented for the first time on February 27, 2026, at a Best Oral Session of the European Society of Gynaecological Oncology 2026 Congress. The final analysis, conducted over a median follow-up of 32.7 months, found that pembrolizumab reduced the risk of death by 18 percent regardless of PD-L1 status (hazard ratio 0.82; p=0.0115), with median overall survival of 17.7 months versus 14.0 months in the control arm, according to Merck’s announcement of the ESGO data.
Dr. Nicoletta Colombo of the European Institute of Oncology, a lead investigator on the trial, stated that “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.”
Safety and Biomarker Selection
Treatment-related adverse events occurred in 97.8 percent of patients in the pembrolizumab arm versus 95.3 percent in the placebo arm. Grade 3 or higher events affected 67.5 percent of pembrolizumab-treated patients compared with 55.3 percent on placebo. Immune-mediated adverse events, a class effect associated with checkpoint inhibitor therapy, were reported in 39.1 percent of patients receiving pembrolizumab versus 18.9 percent in the control group. The most common toxicities in both arms included anemia, peripheral neuropathy, alopecia, and fatigue.
Patient eligibility for the approved indication requires testing for PD-L1 expression using the FDA-approved PD-L1 IHC 22C3 pharmDx companion diagnostic, which is now required prior to treatment initiation.
A Historically Resistant Disease
Prior to this approval, checkpoint inhibitors had failed to demonstrate meaningful survival benefits in ovarian cancer despite showing durable responses in a range of other solid tumors. Multiple earlier trials evaluating PD-1 and PD-L1 inhibitors in ovarian cancer produced negative or inconclusive results. Researchers and oncologists had come to regard ovarian cancer as a setting where immunotherapy was unlikely to show a broad benefit, in part because ovarian tumors typically exhibit low mutational burden and an immunosuppressive microenvironment.
The KEYNOTE-B96 results challenge that assumption, particularly for the PD-L1-positive subset, and suggest that concurrent weekly paclitaxel may play a role in modulating the tumor immune environment in a way that potentiates checkpoint blockade.
The European Medicines Agency’s Committee for Medicinal Products for Human Use has also issued a positive opinion for pembrolizumab in this indication, restricted to the PD-L1-positive population, signaling likely regulatory approval in Europe as well.