VCH-916

Hepatitis E is a global public health problem. Ribavirin (RBV) and pegylated interferon alpha are currently administered to cure hepatitis E. Recently, in combination with RBV, sofosbuvir (SOF), an anti-hepatitis C virus nucleotide analog, is also given to patients with chronic hepatitis E. However, this combinatorial therapy sometimes fails to achieve a sustained virological response. In this study, we used 27 antiviral compounds, including 15 nucleos(t)ide analogs, for in vitro screening against a genotype 3 HEV strain containing a Gaussia luciferase reporter. RBV, SOF, 2'-C-methyladenosine, 2'-C-methylcytidine (2CMC), 2'-C-methylguanosine (2CMG), and two 4'-azido nucleoside analogs (R-1479 and RO-9187) suppressed replication of the reporter genome, while only RBV, SOF, 2CMC and 2CMG inhibited the growth of genotype 3 HEV in cultured cells. Although 2CMG and RBV (2CMG/RBV) exhibited a synergistic effect while SOF/RBV and 2CMC/RBV showed antagonistic effects on the reporter assay, these three nucleos(t)ide analogs acted additively with RBV in inhibiting HEV growth in cultured cells. Furthermore, SOF and 2CMG, with four interferons (IFN-α2b, IFN-λ1, IFN-λ2 and IFN-λ3), inhibited HEV growth efficiently and cleared HEV in cultured cells. These results suggest that, in combination with RBV or interferons, SOF and 2CMG would be promising bases for developing anti-HEV nucleos(t)ide analogs.

The direct-acting antivirals (DAAs) currently in development for treatment of hepatitis C fall into four categories: (i) NS3/4A protease inhibitors: ABT-450/r, faldaprevir, asunaprevir, GS-9256, vedroprevir (GS-9451), danoprevir, MK-5172, vaniprevir, sovaprevir, ACH-2684, narlaprevir and simeprevir, in addition to those that are already developed [telaprevir (Incivek®) and boceprevir (Victrelis®)], (ii) NS5A protein inhibitors: ABT-267, daclatasvir, ledipasvir, ACH-2928, ACH-3102, PPI-668, AZD-7295, MK-8742, and GSK 2336805; (iii) NS5B (nucleoside-type) polymerase inhibitors: sofosbuvir (now approved by the FDA since 6 December 2013), GS-0938, mericitabine, VX-135, ALS 2158 and TMC 649128; (iv) NS5B (non-nucleoside-type) polymerase inhibitors: VX-222, ABT-072, ABT-333, deleobuvir, tegobuvir, setrobuvir, VCH-916, VCH-759, BMS-791325 and TMC-647055. Future drug combinations will likely exist of two or more DAAs belonging to any of the 4 categories, with the aim to achieve (i) pan-genotypic hepatitis C virus (HCV) activity, (ii) little or no risk for resistance; (iii) short duration (i.e. 12 weeks) of treatment, and (iv) a sustained viral response (SVR) and definite cure of the disease.