Merck’s MK-5172/MK-8742 for the treatment of chronic hepatitis C virus infection has been granted Breakthrough Therapy designation by the FDA. MK-5172/MK-8742 is an all-oral combination regimen consisting of MK-5172, an investigational HCV NS3/4A protease inhibitor, and MK-8742, an investigational HCV NS5A replication complex inhibitor.   According to the FDA, the designation of an investigational drug as a Breakthrough Therapy is intended to expedite the development and review of a candidate fo...