Infrequent asymptomatic ALT elevations were transient, typically occurred by week 1-2 and declined without study drug interruption. Concurrent systemic estrogen use was the main risk factor for ALT elevations. Hemoglobin declines to <10g/dL were infrequent, related to RBV use, and manageable by RBV dose reduction. Less than 0.5% of patients received erythropoietin or red blood cell transfusion. Conclusions: The combination of ABT-450/r/ombitasvir and dasabu-vir with or without RBV is well tolerated in a broad and diverse patient drug discovery population. Disclosures: Michael W. Fried – Consulting: Genentech, Merck, Abbvie, Vertex, Janssen, Bristol Myers Squibb, Gilead; Grant/Research

Support: Genentech, Merck, AbbVie, Vertex, Janssen, Bristol Myers Squibb, Gilead; Patent Held/Filed: HCCPlex Adrian M. Di Bisceglie – Grant/Research Support: Genentech, Gilead, AbbVie, BMS John M. Vierling – Advisory Committees or Review Panels: Abbvie, Bristol-Mey-ers-Squibb, Gilead, Hyperion, Intercept, Janssen, Novartis, Merck, Sundise, HepQuant, Salix; Grant/Research Ganetespib cost Support: Abbvie, Bristol-Meyers-Squibb, Eisai, Gilead, Hyperion, Intercept, Janssen, Novartis, Merck, Sundise, Ocera, Mochida; Speaking and Teaching: GALA, Chronic Liver Disease Foundation, ViralEd Edward J. Gane – Advisory Committees or Review Panels: Novira, AbbVie, Novartis, Gilead Sciences, Janssen Cilag, Vertex, Achillion, Tekmira, Merck, Ide-nix; Speaking

and Teaching: AbbVie, Novartis, Gilead Sciences, Janssen Cilag Frederik Nevens – Consulting: CAF, Intercept, Gore, BMS, Abbvie, Novartis, MSD, Eumedica, Janssen; Grant/Research Support: Ipsen, Roche, MSD, Astellas Simone I. Strasser – Advisory Committees or Review Panels: Janssen, AbbVie, Roche Products Australia, MSD, Bristol-Myers Squibb,

Histone demethylase Gilead, Norgine, Bayer Healthcare; Speaking and Teaching: Bayer Healthcare, Bristol-Myers Squibb, MSD, Roche Products Australia, Gilead, Janssen Ola Weiland – Advisory Committees or Review Panels: MSD, BMS, Janssen, Medivir, Gilead, AbbVie; Grant/Research Support, MSD, Roche, BMS; Speaking and Teaching: Novartis, Janssen, Roche, Gilead, AbbVie, Medivir Sandra S. Lovell – Employment: AbbVie Barbara Da Silva-Tillmann – Employment: AbbVie Nancy Shulman – Employment: Abbvie Naoky Tsai – Advisory Committees or Review Panels: BMS, Gilead, AbbVie; Grant/Research Support: BMS, Gilead, AbbVie, Janssen, Beckman; Speaking and Teaching: BMS, Gilead, AbbVie, Janssen, Roche, Merck David R. Nelson – Advisory Committees or Review Panels: Merck; Grant/Research Support: Abbot, BMS, Beohringer Ingelheim, Gilead, Genentech, Merck, Bayer, Idenix, Vertex, Jansen The following people have nothing to disclose: Sorin Rugina Background Ledipasvir (LDV), a potent HCV NS5A inhibitor, is under regulatory review for the treatment of chronic HCV infection as a fixed-dose combination tablet with sofosbuvir.