KEYNOTE-100: In Women With Advanced Ovarian Cancer, Pembrolizumab Yields Modest Antitumor Efficacy

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the final results of the phase II KEYNOTE-100 study of pembrolizumab in women with advanced and recurrent ovarian cancer showed that pembrolizumab monotherapy produced modest clinical activity. Ursula Matulonis, MD, of Dana-Farber Cancer Institute, Harvard Medical School, reported the data at the ASCO20 Virtual Scientific Program.1

Recurrent ovarian cancer is a leading cause of death from gynecologic cancer, reported Dr. Matulonis. “The majority of our patients relapse after first-line platinum and taxane-based chemotherapy,” she added. For patients with platinum-sensitive disease, response rates are up to 67%, but for patients with platinum-resistant disease, tumor response rates are 10% to 15%. Subsequent recurrences are increasingly platinum- and treatment-resistant.

Ursula Matulonis, MD

Ursula Matulonis, MD

KEYNOTE-100 Study Details

Final analysis of the phase II KEYNOTE-100 study was conducted at a protocol-specified data cutoff of September 18, 2019. The primary endpoint was overall response rate. Secondary endpoints included duration of response, disease control rate (complete response plus partial response plus stable disease of at least 24 weeks), progression-free survival, overall survival, and safety. A total of 376 women with a diagnosis of recurrent and advanced epithelial ovarian fallopian tube or primary peritoneal cancer were assigned to one of two cohorts. Those patients who had received between one and three prior lines of therapy were assigned to cohort A (n = 285), whereas patients who had received four to six previous lines of treatment were assigned to cohort B (n = 91). Both groups required a platinum-free interval of at least 3 months.

For up to 2 years, all patients received pembrolizumab monotherapy at 200 mg intravenously every 3 weeks until disease progression, unacceptable toxicity, or death. PD-L1 expression from archival tumor tissue biopsy was measured by the combined positive score (CPS).

Key Results

Dr. Matulonis reported that in cohort A, 8 of 285 patients completed treatment, with a median follow-up of 37.8 months. A total of 277 patients discontinued treatment due to radiographic (n = 211) or clinical (n = 34) disease progression or toxicity (n = 22). One patient experienced a complete response; nine patients withdrew for other reasons. 

In cohort B, 3 of 91 patients completed treatment, at a median follow-up of 38 months. A total of 88 discontinued treatment due to radiographic (n = 64) or clinical (n = 17) disease progression, toxicity (n = 3), or other reasons (n = 3). One patient achieved a complete response.

The overall response rate was 8.1% in cohort A and 9.9% in cohort B, whereas the disease control rate was 22.1% and 22%, respectively. Among all patients from cohorts A and B, the overall response rate was 8.5%, with a disease control rate of 22.1%. Median progression-free survival for both groups was 2.1 months; there was no difference for cohort A vs B. Median overall survival was 18.7 months vs 17.6 months, respectively.

Dr. Matulonis added that for patients in cohort A who had cancer that was CPS 1 or higher, the overall response rate for pembrolizumab was 6.9%, with a disease control rate of 24.8%. For those with tumors that had a higher CPS score, the response rate increased to 11.6%. Disease control rates stayed the same, at approximately 26%. In cohort B, for patients with a CPS score of 1 or higher, the overall response rate was 10.2%, with a disease control rate of 22.4%. In patients with tumors that had CPS scores of 10 or higher in cohort B, the response rate increased to 18.2%, with a disease control rate of 31.8%.


The most common adverse events of any grade included fatigue, nausea, decreased appetite, hypothyroidism, asthenia, and diarrhea. No new treatment-related adverse events were reported compared with other single-agent pembrolizumab trials.

The study authors concluded that with 37.8 months of median follow-up, results confirmed that pembrolizumab monotherapy elicits modest antitumor efficacy in recurrent ovarian cancer. Dr. Matulonis said: “Responses were durable and typically lasted at least 6 months. Median overall survival was 18.7 months overall, with a trend toward a longer overall survival with increasing PD-L1 expression in both cohorts. No new safety signals were identified.” 

Disclosure: Research funding for the study was provided by Merck & Co., Inc. Dr. Matulonis has served as a consultant or advisor to ImmunoGen, Merck, and Novartis; has received research funding from Fujifilm, ImmunoGen, Leap Therapeutics, Merck, Mersana, Novartis, SQZ Biotechnologies, Syndax, Tesaro; and has received reimbrusement for travel and accommodation expenses from AstraZeneca.


1. Matulonis UA, Shapira R, Santin A, et al: Final results from the KEYNOTE-100 trial of pembrolizumab in patients with advanced recurrent ovarian cancer. ASCO20 Virtual Scientific Program. Abstract 6005.