Pharmacodynamics of PEG-IFN-α-2a in HIV/HCV co-infected patients: Implications for treatment outcomes

Background & Aims: The pharmacokinetics and pharmacodynamics of pegylated-interferon-α-2a (PEG-IFN) have not been described in HCV/HIV co-infected patients. We sought to estimate the pharmacokinetics and pharmacodynamics of PEG-IFN and determine whether these parameters predict treatment outcome. Methods: Twenty-six HCV/human immunodeficiency virus (HIV)-co-infected patients were treated with a 48-week regimen of PEG-IFN (180 μg/week) plus ribavirin (11 mg/kg/day). HCV RNA and PEG-IFN concentrations were obtained from samples collected until week 12. A modeling framework that includes pharmacokinetic and pharmacodynamic parameters was developed. Results: Five patients discontinued treatment. Seven patients achieved a sustained virological response (SVR). PEG-IFN concentrations at day 8 were similar to steady-state levels (p = 0.15) and overall pharmacokinetic parameters were similar in SVRs and non-SVRs. The maximum PEG-IFN effectiveness during the first PEG-IFN dose and the HCV-infected cell loss rate (δ), were significantly higher in SVRs compared to non-SVRs (median 95% vs. 86% [p = 0.013], 0.27 vs. 0.11 day-1 [p = 0.006], respectively). Patients infected with HCV genotype 1 had a significantly lower average first-week PEG-IFN effectiveness (median 70% vs. 88% [p = 0.043]), however, 4- to 12-week PEG-IFN effectiveness was not significantly different compared to those with genotype 3 (p = 0.114). Genotype 1 had a significantly lower δ compared to genotype 3 (median 0.14 vs. 0.23 day-1 [p = 0.021]). The PEG-IFN concentration that decreased HCV production by 50% (EC50) was lower in genotype 3 compared to genotype 1 (median 1.3 vs. 3.4 [p = 0.034]). Conclusions: Both the HCV-infected cell loss rate (δ) and the maximum effectiveness of the first dose of PEG-IFN-α-2a characterised HIV co-infected patients and were highly predictive of SVR. Further studies are needed to validate these viral kinetic parameters as early on-treatment prognosticators of response in patients with HCV and HIV.

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