FDA News reports that FDA has granted breakthrough therapy designation to Merck’s Keytruda, an anti-PD-1 therapy for treating patients with microsatellite instability high metastatic colorectal cancer. The breakthrough designation is based on Phase 2 data of the drug’s activity in cancers with microsatellite instability, a feature present in cells with certain types of DNA repair defects. Merck is conducting a Phase 3 study of the drug in a treatment-naïve patient population. Keytruda (pembrolizumab) previously was granted breakthrough status for advanced melanoma and advanced non-small cell lung cancer.