['Less than half of patients infected with hepatitis C virus (HCV) achieve sustained viral clearance after pegylated interferon (peginterferon) and ribavirin therapy. S-adenosyl methionine (SAMe) improves interferon signaling in cell culture. We assessed the effect of SAMe on the kinetics of the early antiviral response and interferon signaling in nonresponders to previous antiviral therapy and investigated the mechanisms involved.', 'Nonresponders with HCV genotype 1 were given peginterferon alfa-2a and ribavirin for 2 weeks (course A, baseline/control). After 1 month, patients received SAMe (1600 mg daily) for 2 weeks and then peginterferon and ribavirin for 48 weeks (course B; completed by 21 of 24 patients). Viral kinetics and interferon-stimulated gene (ISG) expression in peripheral blood mononuclear cells (PBMCs) were compared between courses.', 'The decrease in HCV RNA from 0 to 48 hours (phase 1) was similar with and without SAMe. However, the second phase slope of viral decline was improved with SAMe (course A, 0.11 ± 0.04 log(10) IU/mL/wk; course B, 0.27 ± 0.06; P = .009); 11 patients (53%) achieved an early virological response, and 10 (48%) had undetectable HCV RNA by week 24. Induction of ISGs in PBMCs was significantly greater during course B. In cultured cells, SAMe increased induction of ISGs and the antiviral effects of interferon by increasing STAT1 methylation, possibly affecting STAT1-DNA binding.'] Does s-adenosyl methionine improve early viral responses and interferon-stimulated gene induction in hepatitis C nonresponders?