Background & Aims: Peginterferon with ribavirin therapy for chronic hepatitis C leads to sustained loss of serum hepatitis C virus (HCV) RNA in half of treated patients. Although viral kinetic profiles in treatment responders shed light on the mechanism of action of interferon and ribavirin, minimal information is available to explain why some patients experience little or no virologic suppression. Methods: We evaluated factors that might be associated with the lack of a week-20 virologic response in previous nonresponder patients undergoing peginterferon and ribavirin retreatment. Among 1145 patients enrolled in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis Trial's lead-in treatment phase, 588 who received more than 80% of prescribed therapy for 20 weeks were analyzed. Results: By week 20, 245 patients (41.7%) had undetectable HCV RNA (full response), 186 (31.6%) had a 1 log10 or greater decrease in HCV RNA (partial response), and 157 (26.7%) had less than a 1 log10 decrease (null response) in HCV RNA. Null response was associated independently with African American race, genotype-1 infection, and less reduction in body weight, platelets, and white blood cells during treatment. Conclusions: On-treatment variables associated with null response suggest a blunted systemic response to interferon. These observations have important implications for the design and analysis of trial results in which novel agents are evaluated. Further studies are needed to discern whether host interferon resistance, viral drug resistance, or both are playing a role in patients who have no virologic response to interferon treatment.
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