CHICAGO – Pembrolizumab monotherapy is associated with antitumor activity in patients with advanced recurrent ovarian cancer, interim results from the phase 2 KEYNOTE-100 study suggest.
Notably, objective response rates among study subjects increased in tandem with increased programmed death-ligand 1 (PD-L1) expression, which helps define the population most likely to benefit from single agent pembrolizumab (Keytruda), Ursula A. Matulonis reported during an oral abstract session at the annual meeting of the American Society of Clinical Oncology.
Further, no new safety signals were identified, said Dr. Matulonis, medical director and program leader of the Medical Gynecologic Oncology Program at of Dana-Farber Cancer Institute and professor of medicine at Harvard Medical School, both in Boston.
All patients received intravenous pembrolizumab at 200 mg every 3 weeks for 2 years or until progression, death, unacceptable toxicity, or consent withdrawal, and tumor imaging was performed every 9 weeks for a year, then every 12 weeks thereafter until progressive disease, death, or study completion.
The overall response rate (ORR) among 285 patients in Cohort A, who had one to three prior chemotherapy lines for recurrent advanced ovarian cancer and a platinum-free or treatment-free interval of 3-12 months, was 7.4%, with mean duration of response of 8.2 months. The ORR among 91 patients in Cohort B, who had four to six prior chemotherapy lines and a platinum-free or treatment-free interval of at least 3 months, was 9.9%; the mean duration of response was not reached in Cohort B.
Among all-comers, the ORR was 8.0%, including 7 complete responses and 23 partial responses. Mean duration of response was 8.2 months, and 65.5% of responses lasted at least 6 months. Further, responses were observed across all subgroups, Dr. Matulonis said, noting that responses were seen regardless of age, prior lines of treatment, progression-free/treatment-free interval duration, platinum sensitivity, and histology.
“The one factor that did predict response was a [combined positive score] of 10 or higher, where there were more responses,” she said.