FDA Approves Keytruda for Metastatic Small Cell Lung Cancer

The Food and Drug Administration (FDA) approved Keytruda (pembrolizumab) monotherapy for the treatment of patients with metastatic small cell lung cancer (SCLC) whose disease progressed on or after platinum-based chemotherapy and at least one other prior line of therapy.

“Keytruda is already an established treatment option for non-small cell lung cancer, and today’s approval in small cell lung cancer demonstrates our commitment to bringing forward new treatment options for patients with advanced, difficult-to-treat cancers,” Dr. Jonathan Cheng, vice president of oncology clinical research at Merck Research Laboratories, said in a press release. “We look forward to continuing to advance important clinical research in small cell lung cancer.”

The agency based its decision on pooled data from the SCLC cohorts of two multicenter, multi-cohort, non-randomized, open-label studies: the phase 2 KEYNOTE-158 trial and the phase 1b KEYNOTE-028 trial.

KEYNOTE-158 included patients with 10 different tumor types, and those whose tumors were microsatellite instability-high (MSI-H). Patients on the trial received 200 mg of Keytruda intravenously every three weeks for two years or until disease progression, unacceptable toxicity or study withdrawal.

KEYNOTE-028 is a nonrandomized, multi-arm trial that looked at the safety and efficacy of Keytruda in patients with advanced solid tumors — including 24 patients with SCLC. They received 10 mg/kg of Keytruda every two weeks until progression, intolerable toxicity, physician decision to discontinue or withdrawal of consent.

Patients treated with Keytruda demonstrated an overall response rate of 19%, including complete response rate of 2% and a partial response rate of 17%.

Among the 16 patients who experienced a response to treatment, 94% had a duration of response (the time between the initial response to therapy and subsequent disease progression or relapse) of six months or longer, 63% had a duration of response of 12 months or longer and 56% had a duration of response of 18 months or longer.

Among the patients with SCLC enrolled in KEYNOTE-158 (107 patients) and KEYNOTE-028 (24 patients) who were included in the safety analysis, the side effects observed were similar to those occurring in patients with other solid tumors who received Keytruda as a single agent.

“Small cell lung cancer, which accounts for 10% to 15% of all lung cancers, is often diagnosed at an advanced stage where the prognosis is very poor and there have historically been limited treatment options,” Dr. Patrick Ott, clinical director of the Center for Immuno-Oncology at Dana-Farber Cancer Institute in Boston, said in the release. “The approval of Keytruda in small cell lung cancer provides an additional treatment option for patients based on the clinical response rates from KEYNOTE-158 and KEYNOTE-028.”