[30] One of these might play an important role in the response to elongated therapy. In the present study, seven of 10 patients with ITPA non-CC type showed > 2500 ng/mL LY2157299 mw RBV at week 44. In contrast, 19 of 41 patients with the ITPA CC type had > 2500 ng/mL RBV at week 44. Many patients with ITPA non-CC type had > 2500 ng/mL RBV at week 44. We did not detect associations between ITPA variants and RBV concentrations at week 44 (Fig. 4b). RBV concentration is affected by both the dose administered and its clearance; the latter is regulated by renal function.[33] Serum creatinine level was within the normal range in the patients included in the present study, indicating that their renal function is sufficient

buy GW-572016 to receive RBV adjusted by body weight. The RBV dose administered is dependent on body weight and is correlated with RBV-related adverse events, particularly

anemia. Recently, it was reported that both SLC28A2 rs11854484 genotype and ITPA genotype were related to RBV-related anemia. However, the factor associated with RBV concentration at weeks 4 and 8 was the SLC28A2 rs11854484 genotype, but not the ITPA genotype.[34] In patients with LVR, RBV concentration and ITPA genotype were independently associated with the outcome of extended treatment (Table 3). Our data suggest that serum RBV concentration at week 44 was significantly higher in patients with SVR than in those with relapse (P = 0.002). On the other hand, total dosage of RBV was not related to the outcome of extended therapy. In previously published data regarding 48-week therapy, both the RBV dose administered and the RBV concentration in peripheral blood were associated with selleck the outcome of combination therapy with PEG-IFN and RBV.[35, 36] Furusyo et al. reported that in both groups with < 60% and ≥ 60% of RBV assigned total dosage, the mean RBV concentration at 48 weeks in patients with SVR was > 1500 ng/mL and was significantly higher than in those with relapse, suggesting

that RBV concentration was unaffected by the assigned total dosage.[37] In the present study, no association between RBV concentration on week 44 and the total dose of RBV administered was identified (data not shown). Many novel interferon-free antiviral regimens for HCV are now under clinical investigation. Some of these include RBV in combination with one or two direct-acting antiviral agents.[38, 39] RBV will remain a key drug for treatment of chronic HCV infection in the forthcoming era of oral combination antiviral therapy. Further studies are required to evaluate the significance of ITPA SNP as predictors of not only RBV-induced anemia but also of treatment outcome. In conclusion, age, RBV concentration, timing of HCV RNA disappearance, and ITPA SNP rs1127354 were associated with a higher SVR rate in LVR patients given 72-week treatment. These predictive factors may allow more efficient extended treatment with PEG-IFN and RBV for patients with LVR. We thank Ms.