OBJECTIVE: Interleukin-12 is a cytokine with a multitude of immunomodulatory actions. Currently, interferon-α (IFN-α) monotherapy and combination treatment with IFN and ribavirin are the only therapies with proven efficacy against chronic hepatitis C infection. The purpose of this study was to assess the safety and antiviral activity of recombinant interleukin-12 (rhIL-12) in adults with chronic hepatitis C who did not achieve a sustained response to previous IFN-α therapy. METHODS: This was a randomized, placebo-controlled, double-blind trial. We randomized 24 patients to one of three dose groups: 30 ng/kg, 100 ng/kg, and 300 ng/kg. Within each group, six patients received rhIL-12, and two patients received placebo administered s.c. twice a week for 12 wk. RESULTS: Three of six patients treated with rhIL-12 at a dose of 300 ng/kg had loss of detectable hepatitis C RNA by reverse transcription-polymerase chain reaction compared with the placebo group (p = 0.05). All patients relapsed at the end of the 3-month treatment period. No other dose group demonstrated a loss of detectable hepatitis C RNA. CONCLUSIONS: RhIL-12 at 300 ng/kg can suppress hepatitis C RNA to undetectable levels by reverse transcription-polymerase chain reaction, although relapse occurred when treatment was stopped. RhIL-12 was well tolerated with the most common side effects being flu-like symptoms and headaches.
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