FDA grants full approval for Merck’s Keytruda in MSI-H or dMMR tumors

Merck "announced that the FDA has granted full approval to KEYTRUDA, Merck’s anti-PD-1 therapy, for the treatment of adult and pediatric patients with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) solid tumors, as determined by an FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment options. The conversion from an accelerated to a full (regular) approval is based on results from the Phase 2 KEYNOTE-158, KEYNOTE-164 and KEYNOTE-051 trials and includes data in 504 adult and pediatric patients across more than 30 types of cancer. This marks the first full approval for an immunotherapy based on a predictive biomarker, regardless of solid tumor type. The full approval was based on data from three multicenter, non-randomized, open-label multi-cohort trials. KEYNOTE-164 enrolled 124 patients with advanced MSI-H/dMMR colorectal cancer that progressed following treatment with fluoropyrimidine and either oxaliplatin or irinotecan with or without anti-VEGF/EGFR mAb-based therapy. KEYNOTE-158 enrolled 373 patients with advanced MSI-H/dMMR non-colorectal cancers who had disease progression following prior therapy. Patients were either prospectively enrolled with MSI-H/dMMR tumors (Cohort K) or retrospectively identified in one of 10 solid tumor cohorts. KEYNOTE-051 enrolled seven pediatric patients with MSI-H/dMMR cancers. All trials excluded patients with autoimmune disease or a medical condition that required immunosuppression. Regardless of histology, MSI or MMR tumor status was determined using polymerase chain reaction (local or central) or immunohistochemistry (local or central), respectively. "