Background: Pegylated interferon (PEG-IFN) alpha2a and alpha2b differ in their pharmacokinetic properties, which might have an effect on their antiviral effects against hepatitis C virus (HCV). Differences between PEG-IFN-alpha molecules could be more pronounced in HIV-coinfected individuals, in whom response to HCV treatment is impaired.
Methods: All HCV-HIV-coinfected patients included in PRESCO and EXTENT trials recruited at one referral centre were retrospectively analysed. In both trials, ribavirin (RBV) 1,000-1,200 mg/day was prescribed together with standard doses of PEG-IFN-alpha2a or -alpha2b. The attainment of serum HCV RNA <10 IU/ml at weeks 4, 12 and 24 was assessed. On-treatment analyses were made to estimate the intrinsic potency of PEG-IFN-alpha2a versus -alpha2b.
Results: A total of 218 patients were examined, 138 on PEG-IFN-alpha2a and 80 on PEG-IFN-alpha2b. Baseline characteristics were comparable in both groups. Undetectable serum HCV RNA at weeks 4, 12 and 24 was more frequently attained using PEG-IFN-alpha2a than -alpha2b (45% versus 27% [P=0.02]; 65% versus 45%/ [P=0.01]; and 75% versus 55%/ [P=0.01], respectively), regardless of HCV genotype. Plasma RBV levels did not differ between groups. In multivariate analysis, HCV genotypes 2/3 (odds ratio [OR] 12.5; 95% confidence interval [95% CI] 3.45-33.33; P<0.001), use of zidovudine (OR 0.30; 95% CI 0.11-0.85; P=0.02) and treatment with PEG-IFN-alpha2a (OR 2.12; 95% CI 1.02-4.54; P=0.04) were independent predictors of undetectable HCV RNA at week 24. Conversely, the incidence of serious adverse events was more common with PEG-IFN-alpha2a than -alpha2b (13.2% versus 3.6%; P=0.018).
Conclusions: The antiviral effect against HCV seems to be greater for PEG-IFN-alpha2a than -alpha2b in the HIV setting. A shorter half-life of PEG-IFN-alpha2b could explain this finding.