a double-blind study which randomly assigned adults with untreated hepatitis C virus, genotype 1, to one of three groups. Each group received a month of peginterferon alfa-2b and ribavirin before being randomized to one of three arms. The first arm received placebo plus peginterferon-ribavirin for 44 weeks, the second arm received boceprevir plus peginterferon-ribavirin for 24 weeks, and those with a detectable HCV RNA level between weeks 8 and 24 received placebo plus peginterferon-ribavirin for an additional 20 weeks, and the third arm received boceprevir plus peginterferon-ribavirin for 44 weeks. Black patients and nonblack patients were enrolled and analyzed separately, since black patients have been shown to respond less well to antiviral therapy with peginterferon plus ribavirin than nonblacks. In all, 938 nonblack and 159 black patients were enrolled in the study. At 44 weeks, among the nonblack cohort, a 40% sustained virologic response (125 of 311 patients) occurred in the placebo group, a 67% response (211 of 316 patients) in the response-guided boceprevir group, and a 68% response (214 of 311 patients) in the fixed-duration therapy group. Important side effects included anemia and dysgeusia (distortion of the sense of taste). RESPOND-2 trial The RESPOND-2 trial studied patients with chronic hepatitis C genotype 1 who did not have a sustained response to therapy with peginterferon-ribavirin therapy. All patients received a month of peginterferon alfa-2b and ribavirin before being randomized to one of three arms. The first arm received placebo plus peginterferon-ribavirin for 44 weeks. The second group received boceprevir plus peginterferon-ribavirin for 32 weeks, and those with a detectable HCV RNA level at week 8 received peginterferon-ribavirin and placebo for another 12 weeks. The third group received boceprevir and peginterferon-ribavirin for 44 weeks. Four hundred and three people were treated in the trial. At 44 weeks, the control group had a lower sustained virologic response rate (21%) than either of the groups treated with boceprevir—59% sustained viral response for the group with response-guided therapy and 66% response for the group with fixed-duration therapy. See also Paxlovid, a structurally related drug developed for the treatment of COVID-19 Telaprevir, a similar agent for the treatment of hepatitis C References Cyclopropanes CYP3A4 inhibitors NS3/4A protease inhibitors Tert-butyl compounds Merck & Co. brands Cyclobutyl compounds Ureas Amides Pyrrolidines