Merck’s (MRK) supplemental New Drug Application for the expanded indication of Keytruda in microsatellite instability-high cancer is under FDA review – with a decision expected on March 8, 2017.Microsatellite instability-high, or MSI-H, is an established biomarker in certain types of cancer.Keytruda has already received FDA approval for the treatment of metastatic melanoma, metastatic non-small cell lung cancer, and recurrent or metastatic head and neck squamous cell carcinoma.The drug brought home sales of $1.40 billion in 2016, up 148% compared to 2015.