Following a review of data from 15 different cancer types, the FDA has granted accelerated approval
to the programmed death 1 (PD-1) inhibitor pembrolizumab for adult and pediatric patients with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) solid tumors that lack suitable alternative treatments or that have progressed on treatment. The indication also includes patients with colorectal cancer (CRC) that is MSI-H or dMMR and who have progressed on fluoropyrimidine, oxaliplatin, and irinotecan.
The data from 5 uncontrolled, multi-center, single-arm studies, included 149 patients with MSI-H or dMMR cancers—a majority (90) had CRC and the remaining 59 were diagnosed with one of 14 other cancers. Patients were treated with 200 mg pembrolizumab every 3 weeks, or 10 mg/kg every 2 weeks, for a maximum of 24 weeks, until unacceptable toxicity or progression was observed.
The objective response rate was 39.6% (95% CI, 31.7 to 47.9) and the minimum duration of response was 6 months in 78% of patients who responded to the PD-1 inhibitor. Further, 11 complete responses and 48 partial responses were documented.
Merck, which has developed the drug, is expected to conduct further studies to confirm the clinical benefit of pembrolizumab for this indication.
In the past month, pembrolizumab has received FDA approvals for several indications, including advanced or metastatic urothelial carcinoma
and metastatic nonsquamous non-small cell lung cancer
(NSCLC). It was one of the first immuno-oncology agents to be approved for melanoma
and for non-small cell lung cancer.