Relationship between inosine triphosphate genotype and outcome of extended therapy in hepatitis C virus patients with a late viral response to pegylated‐interferon and ribavirin

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It is not yet clear which factors are associated with the outcome of 72-week treatment with pegylated-interferon and ribavirin (RBV) in patients with chronic hepatitis C virus (HCV) infection. In 66 patients with HCV genotype 1 who had a late viral response (LVR) to 72-week treatment of pegylated-interferon and RBV, we examined the factors that determined the outcome, including single nucleotide polymorphisms of interleukin-28B and inosine triphosphatase (ITPA) genes. Thirty seven of 66 (56%) patients with LVR achieved a sustained viral response (SVR). The mean age of these 37 SVR patients was 55, compared with 61 in 29 relapsed patients (P = 0.009). Twenty six of 54 (48%) patients with the CC genotype and 11 of 12 (92%) with the CA/AA genotype of ITPA rs1127354 achieved SVR (P = 0.006). The SVR rates were 79%, 40%, 60%, and 33% in patients with undetectable HCV RNA on weeks 16, 20, 24, and 28 or later, respectively (P = 0.014). Finally, serum RBV concentration at week 44 of treatment was significantly higher in the SVR group (2651 ng/mL) than in the relapse group (1989 ng/mL, P = 0.002). In contrast, the rate of the interleukin-28B genotype was not different between the groups. Multiple regression analysis showed that age < 60 years, ITPA CA/AA genotype, and serum RBV concentration were significant independent predictive factors for SVR. Our findings elucidated the association of four factors, including ITPA genotype, with the outcome of 72-week treatment in LVR patients.