The U.S. Food and Drug Administration granted accelerated approval to Keytruda (pembrolizumab) for adult and pediatric patients with unresectable or metastatic, microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) solid tumors that have progressed following prior treatment and who have no satisfactory alternative treatment options or with MSI-H or dMMR colorectal cancer that has progressed following treatment with a fluoropyrimidine, oxaliplatin, and irinotecan.
This is the first time the FDA’s has made a tissue/site-agnostic approval, meaning its it the actual characteristics of the cancer that determine whether Keytruda is indicated, not the physical location of the cancer.
The approval was based on data from 149 patients with MSI-H or dMMR cancers enrolled across five clinical trials. Ninety patients had colorectal cancer and 59 patients were diagnosed with one of 14 other cancer types. Patients were treated with Keytruda until unacceptable side effects, or disease progression that was either symptomatic, rapidly progressive, required urgent intervention, or associated with a decline in performance status. A maximum of 24 months of treatment was administered.
The response rate (ORR) to treatment was 39.6% and responses lasted six months or more for 78% percent of those who responded to Keytruda. There were 11 complete responses and 48 partial responses. ORR was similar irrespective of whether patients were diagnosed with colorectal cancer or a different cancer type (46% across the 14 other cancer types).
The identification of MSI-H or dMMR tumor status for the majority of patients (135/149) was prospectively determined using local laboratory-developed, investigational polymerase chain reaction (PCR) tests for MSI-H status or immunohistochemistry (IHC) tests for dMMR. For 14 of the 149 patients, MSI-H status was determined in a retrospective assessment of 415 patients’ tumor samples using a central laboratory-developed PCR test.
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