For all its success across a wide range of cancer types, Merck’s PD-1 superstar Keytruda has never been able to crack the code for one of the toughest-to-treat indications in oncology—ovarian cancer.
But now, 13 years after the FDA initially blessed it for skin cancer, the U.S. regulator has approved Keytruda as a second- or third-line treatment for patients with a certain type of ovarian cancer.
With the green light, Keytruda becomes the first immune checkpoint inhibitor approved for this indication.
Keytruda is to be used in combination with the chemotherapy paclitaxel and with or without Roche’s targeted cancer therapy Avastin. The endorsement covers those with platinum-resistant recurrent ovarian, fallopian tube or primary peritoneal carcinoma with PD-L1-positive tumors.
The nod also covers infused Keytruda and its subcutaneous version, Keytruda Qlex, which the FDA blessed five months ago.
“For many patients with ovarian cancer, the disease can become platinum-resistant, at which point recurrence is not just a setback—it’s when options can become limited and the reality patients face can change very quickly,” Bradley Monk, M.D., the medical director of the Late-Stage Clinical Research Program at Florida Cancer Specialists and Research Institute, said in a release. “For patients who have been previously treated with standard platinum-based therapies, the FDA approvals of these [Keytruda]-based regimens offer the possibility of more time.”
Paving the way for the green light were results from a phase 3 trial, which demonstrated that the Keytruda regimen, with or without Avastin, reduced the risk of disease progression or death by 28% compared to placebo added to paclitaxel, with or without Avastin, in PD-L1-positive patients. In the same group, the Keytruda regimen also reduced the risk of death by 24% versus the placebo arm.
The median progression-free survival (PFS) period was 8.3 months for those on the Keytruda regimen, versus 7.2 months for those in the placebo arm. The median overall survival for Keytruda patients was 18.2 months compared to 14.0 months for the placebo group.
“These approvals mark an important moment for the ovarian cancer community, reflecting years of focused investment in Keytruda,” Gursel Aktan, Merck’s VP of clinical development, said in a statement. “Introducing the first PD-1 inhibitors for platinum-resistant ovarian cancer means we’re expanding what’s possible for patients facing this disease.”
Of the 643 patients in the trial, 72% were PD-L1-positive. As for Avastin use, 73% of participants received the monoclonal antibody in the study and 46% had received it in a previous line of therapy.
Merck presented those results at the European Society for Medical Oncology (ESMO) Congress in October. At the event, Nicoletta Colombo, M.D., from the European Institute of Oncology in Milan, said that the data support the Keytruda regimen as the “new standard of care” in the indication.
Interestingly, in the trial—and contrary to historical data in other tumor types—Keytruda’s benefit was more pronounced in participants who were PD-L1-negative, as a subgroup analysis showed a PFS improvement of 44%. Still, this patient group wasn't included in the medicine's official FDA-approved label.
Last week, Merck reported 2025 sales of Keytruda at $31.7 billion, an increase of 7% year over year and 49% of the company’s total revenue. Keytruda was the world’s top-selling drug in 2023 and 2024 before being taken over by Eli Lilly’s tirzepatide products last year, which achieved sales of $36.5 billion.