Prior to the discovery of<unk> , a variety of nucleoside analogs had been examined as antihepatitis C treatments, but these exhibited relatively low potency. This low potency arose in part because the enzymatic addition of the first of the three phosphate groups of the triphosphate is slow. The design of<unk> , based on the ProTide approach, avoids this slow step by building the first phosphate group into the structure of the drug during synthesis. Additional groups are attached to the phosphorus to temporarily mask the two negative charges of the phosphate group, thereby facilitating entry of the drug into the infected cell. The NS5B protein is a RNA-dependent RNA polymerase critical for the viral reproduction cycle.<unk>  metabolism. Nucleoside = GS-331077, active triphosphate = GS-461203
Sofosbuvir
Dasabuvir
Telaprevir
Fosamprenavir
Enfuvirtide
Coronavir
Abacavir
Indinavir