Effect of IL28B genotype on early viral kinetics during interferon-free treatment of patients with chronic hepatitis C

Background & Aims: Although interleukin 28B (interferon, lambda 3) (IL28B) genotype affects the response of patients with chronic hepatitis C to peginterferon and ribavirin, little is known regarding its effect on response to direct-acting antivirals in interferon-free combinations. We analyzed the effects of IL28B genotype on the viral kinetic (VK) response to an interferon-free combination of the nucleoside polymerase inhibitor mericitabine (RG7128) and the hepatitis C virus (HCV) protease inhibitor danoprevir. Methods: We performed a double-blind, dose-escalation study of patients with chronic HCV genotype 1 infection who were interferon treatment naive or had not responded to previous therapy with peginterferon and ribavirin. Patients were sequentially assigned to 1 of 7 cohorts then randomly assigned to groups that received up to 13 days of treatment with mericitabine (500 or 1000 mg, twice daily) plus danoprevir (100 or 200 mg, every 8 hours, or 600 or 900 mg, twice daily) or placebo. Eighty-three of 87 patients were genotyped for the IL28B single-nucleotide polymorphism rs12979860. VKs were analyzed only in patients who received 13 days of treatment, at optimal doses, using a biphasic model to describe first- and second-phase slopes of viral decay during therapy. Results: At day 14 (the end of interferon-free treatment), the mean reduction in the serum level of HCV RNA was slightly greater in patients with the CC polymorphism (5.01 log₁₀ IU/mL) than those without (4.59 log₁₀ IU/mL). Modeling revealed that patients with the CC polymorphism had slightly better early VKs, most apparent in the β-phase of viral decay. A mixed effect on the α-phase was observed, which was reduced in magnitude but prolonged in patients with CC, who also had better on-treatment response to peginterferon and ribavirin during follow up. Conclusions: IL28B genotype appears to affect early VKs in patients with chronic hepatitis C receiving interferon-free treatment.