Pembrolizumab (Keytruda) received a green light from the FDA on Tuesday as a third-line treatment for metastatic small cell lung cancer (SCLC), .
The PD-1 immune checkpoint inhibitor is now approved as a monotherapy in these patients following treatment with platinum-based chemotherapy and at least one other line of therapy.
Data supporting the decision came from a pooled analysis of two single-arm pembrolizumab studies -- the phase Ib KEYNOTE-028 and phase II KEYNOTE-158 trials -- where 16 of 83 evaluable patients achieved an objective response (19%), including two complete responders.
At the time of analysis, the median duration of response had not yet been reached. Among the 16 patients who responded, 94% had a response of at least 6 months, 64% had a response of at least 12 months, and 56% responded for at least 18 months.
Additional findings, presented earlier this year at the American Association for Cancer Research annual meeting, showed that most responses (88%) were observed in PD-L1-positive patients and reported a median progression-free survival of 2 months and overall survival of 7.7 months. Rates of overall survival at 1 and 2 years were 34% and 21%, respectively.
Among 131 SCLC patients evaluable for safety in the two trials, grade 3 or higher treatment-related adverse events (AEs) occurred in 10% of patients, which included three deaths -- intestinal ischemia, pneumonia, and encephalopathy. Immune-related AEs occurred in 21% of patients.
Pembrolizumab becomes the third immunotherapy approved for SCLC, following in August 2018 for the third-line treatment of metastatic disease, and earlier this year as first-line treatment in combination with carboplatin and etoposide for extensive-stage disease.