Aim: Host genetic variants leading to inosine triphosphatase (ITPA) deficiency, a condition not thought to be clinically important, protect against hemolytic anemia in chronic hepatitis C patients receiving ribavirin. In this study, we evaluated the clinical significance of ITPA variants in Japanese hepatitis C patients who were treated with pegylated interferon plus ribavirin.
Methods: In this multicenter retrospective cross-sectional study, 474 hepatitis C patients were enrolled who were treated with pegylated interferon plus ribavirin in four geographically different hospitals in Japan. Patients were grouped according to hemoglobin decline of more than 3 g/dL at week 4. Two single nucleotide polymorphisms (SNP) within or adjacent to the ITPA gene (rs6051702, rs1127354) were genotyped.
Results: A functional SNP, rs1127354, within the ITPA exon was strongly associated with protection against anemia with only one (0.8%) in 129 patients with the ITPA minor variant A developing severe anemia (P = 5.9 × 10−20). For rs6051702, which had significant association in European-Americans, significant but weak association with severe hemoglobin reduction was found in Japanese (P = 0.009). In patients excluding genotype 1b and high viral load, those with the ITPA minor variant A achieved significantly higher sustained viral response rate than those with the major variant (CC) (96% vs 70%, respectively, P = 0.0066).
Conclusion: ITPA SNP, rs1127354, is confirmed to be a useful predictor of ribavirin-induced anemia in Japanese patients. Patients with the ITPA minor variant A (∼27%) have an advantage in pegylated interferon plus ribavirin-based therapies, due to expected adherence of ribavirin doses, resulting in a higher viral clearance rate.