Nakagawa M et al. – Despite the fact that inosine triphosphatase (ITPA) variants were less likely to develop anemia, patients with low baseline platelet (PLT) counts were difficult to treat, especially those with the ITPA–CA/AA genotype. These results may give a valuable pharmacogenetic diagnostic tool for the tailoring of dosing to minimize drug–induced adverse events.Methods
- A total of 300 hepatitis C patients treated with PEG-IFN plus ribavirin were analyzed.
- Genetic polymorphisms were determined in ITPA and the quantitative reduction in blood cells from the baseline was analyzed every 4 weeks for the duration of treatment and after the end of therapy.
- The decline in hemoglobin (Hb) or platelet (PLT) level at week 4 compared to baseline was also assessed according to ribavirin concentrations.
- Patients with the ITPA-CA/AA genotypes showed a lower degree of Hb reduction throughout therapy than those with the ITPA-CC genotype and a marked difference in mean Hb reduction was found at week 4 (CA/AA -1.0 vs. CC -2.8, p < 0.001).
- The ITPA-CC genotype had significantly less reduction in the mean platelet count than the ITPA-CA/AA genotypes early during treatment (p < 0.001 for weeks 4 and 8).
- Patients with the ITPA-CA/AA genotypes were less likely to develop anemia, regardless of the concentration of ribavirin.
- Patients with baseline PLT counts below 130 × 103/μl had a significantly lower tendency to achieve sustained virological response (SVR), especially those with the ITPA-CA/AA genotypes.
- ITPA gene variation was not extracted by multivariable analysis as an important predictor of SVR.