Merck (NYSE:MRK), known as MSD outside the United States and Canada, announced today that the U.S. Food and Drug Administration (FDA) has granted MK-5172/MK-8742 Breakthrough Therapy designation for treatment of chronic hepatitis C virus infection. 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. Interim data from an ongoing Phase IIB clinical trial evaluating MK-5172/MK-8742 in genotype 1 infected patients (C-WORTHY Study) is scheduled to be presented at the 64th American Association for the Study of Liver Disease Annual Meeting, Washington D.C., Nov. 1-5. “The designation of MK-5172/MK-8742 as a Breakthrough Therapy for chronic hepatitis C is an important milestone for Merck,” said Dr. Roger M. Perlmutter, president, Merck Research Laboratories. “There remains significant unmet medical need in hepatitis C, and we are looking forward to working with the FDA to advance this program as quickly as we can to bring this investigational combination to HCV specialists and their patients.” 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 that is planned for use, alone or in combination, to treat a serious or life-threatening disease or condition when preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints. Chronic hepatitis C is a priority focus of research and development at Merck. MK-5172 and MK-8742 are being investigated in a broad clinical program that includes studies in patients with multiple HCV genotypes who are treatment-naïve, treatment failures as well as other important HCV subpopulations such as patients with cirrhosis and those co-infected with HIV. For more information please see www.clinicaltrials.gov. About Merck Today's Merck is a global healthcare leader working to help the world be well. Merck is known as MSD outside the United States and Canada. Through our prescription medicines, vaccines, biologic therapies and consumer care and animal health products, we work with customers and operate in more than 140 countries to deliver innovative health solutions. We also demonstrate our commitment to increasing access to healthcare through far-reaching policies, programs and partnerships. For more information, visit www.merck.com and connect with us on Twitter, Facebook and YouTube. Forward-Looking Statement This news release includes “forward-looking statements” within the meaning of the safe harbor provisions of the United States Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of Merck’s management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline products that the products will receive the necessary regulatory approvals or that they will be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements.