The ORRs among those with PD-L1 expression as measured using the combined positive score (CPS), which is defined as the number of PD-L1–positive cells out of the total number of tumor cells x 100, was 5.0% in those with CPS less than 1, 10.2% in those with CPS of 1 or greater, and 17.1% in those with CPS of 10 or greater (vs. the 8.0% ORR in the study), she explained, noting that all complete responses occurred in those with CPS of 10 or higher.
Grade 3-4 treatment-related adverse events occurred in 19.7% of patients, and included fatigue in 2.7%, and anemia, colitis, increased amylase, increased blood alkaline phosphatase, ascites, and diarrhea in 0.8-1.3%. One treatment-related death occurred in a patient with Stevens-Johnson syndrome, and another occurred in a patient with hypoaldosteronism. Immune-mediated adverse events and infusion reactions were most commonly hyperthyroidism and hypothyroidism, and most cases were grade 1-2, she said.
KEYNOTE-100 is an ongoing study that followed KEYNOTE-028, which demonstrated the clinical activity of pembrolizumab in patients with advanced ovarian cancer. To date, KEYNOTE-100 has enrolled 376 patients with epithelial ovarian, fallopian tube, or primary peritoneal cancer and confirmed recurrence after frontline platinum-based therapy. All had a tumor sample available for biomarker analysis.
The patients had a mean age of 61 years, 64% and 35% had performance status scores of 0 and 1, respectively, and 75% had high-grade serous disease.