Area-under-the-curve for peginterferon alpha-2a and peginterferon alpha-2b is not related to body weight in treatment-naive patients with chronic hepatitis C.

One reason for dosing a drug by body weight is to reduce interpatient variability in clinical response. This study evaluated the relationship between body weight and drug exposure for peginterferon alpha-2a and peginterferon alpha-2b used in combination with ribavirin for treating patients with chronic hepatitis C. These two products are dosed differently: peginterferon alpha-2a is flat-dosed at 180 microg regardless of body weight, whereas peginterferon alpha-2b is dosed by body weight at 0.5-1.5 microg/kg. Bodyweight dosing of peginterferon alpha-2b is purported to overcome the adverse effect of increased body weight on sustained virological response. To test this hypothesis, we measured the area-under-the-curve (AUC) for both drugs as part of a previously reported pharmacokinetics study. In total, 22 interferon-naive patients with chronic hepatitis C were treated for 12 weeks. Patients were randomly assigned in a 1:1 ratio to receive once-weekly peginterferon alpha-2a 180 microg (n=10) or peginterferon alpha-2b 1.0 microg/kg (n=12). Ribavirin was dosed by body weight at 1000 mg/day (< or = 75kg) or 1200 mg/day (> 75 kg). We found no correlation between body weight and AUC for either peginterferon alpha-2a or peginterferon alpha-2b. Considerable interpatient variability in AUC occurred for peginterferon alpha-2a [coefficient of variation (CV): 37.5%] and, despite dosing by body weight, for peginterferon alpha-2b (CV: 36.8%). Thus, there appears to be no rationale for a body-weight dosing regimen for peginterferon alpha-2a, and such dosing does not achieve more consistent AUC measurements in patients receiving peginterferon alpha-2b.

Viral dynamics and pharmacokinetics of peginterferon alpha-2a and peginterferon alpha-2b in naive patients with chronic hepatitis c: a randomized, controlled study.

The two available pegylated interferon formulations, peginterferon alpha-2a and peginterferon alpha-2b, have different pharmacokinetic profiles; as a result they may have differing abilities to suppress the hepatitis C virus. A recently reported study by Formann and colleagues assessing early viral kinetics among 20 patients receiving peginterferon alpha-2b either once or twice weekly suggests that once-weekly administration of peginterferon alpha-2b is not sufficient for continuous exposure to interferon over 160 h. Twice-weekly administration is recommended to avoid increases in viral load as interferon levels decline prior to the end of the one-week dosing period. The objective of this study was to compare viral dynamics and pharmacokinetics between peginterferon alpha-2a and peginterferon alpha-2b in interferon-naive chronic hepatitis C patients. Patients were randomized to receive peginterferon alpha-2a 180 microg (n=10) or peginterferon alpha-2b 1.0 microg/kg (n=12) once weekly. Serum peginterferon concentrations were measured at baseline, 24, 48, 120 and 168h. Hepatitis C virus (HCV) RNA was measured at baseline, 24, 48, 120 and 168 h during week 1 and then at 4 and 12 weeks. Peginterferon alpha-2b achieved maximal serum levels at 24 h, and then decreased rapidly. Of the 12 patients who received peginterferon alpha-2b, no drug was detectable in seven (58%) patients at 120 h and in 11 (92%) at 168 h. In contrast, peginterferon alpha-2a concentrations increased continuously over time, reaching maximal serum levels from 48 to 168 h. Drug was detectable in all 10 patients at 168 h. At weeks 1 and 4 no significant difference was observed in mean HCV RNA between the groups. However, at week 12, mean HCV RNA was significantly lower in the peginterferon alpha-2a group versus the peginterferon alpha-2b group (2.8126 vs 3.8726; P<0.01). The differences in mean HCV RNA values at 12 weeks may be related to the different absorption and distribution profiles of the two drugs. In conclusion, once-weekly administration of peginterferon alpha-2b (1.0 microg/kg/wk) may be insufficient for continuous interferon exposure; twice-weekly administration may help avoid increases in viral replication as interferon levels decline. Larger-scale studies assessing both viral kinetics and sustained virological responses are needed to confirm these observations.

Fast relapse and high drop out rate of 48 weeks daily interferon monotherapy in HIV-infected patients with chronic hepatitis C.

BACKGROUND: The standard of care for HCV Hepatitis is the combination of interferon (IFN) plus Ribavirin. In HIV patients the use of this combination therapy may induce drug interactions, and reduces the adherence to HAART. The aim of this study is to evaluate safety and efficacy of a 48 weeks daily dose IFN schedule. METHODS: We evaluated 50 coinfected patients; alpha IFN 2a was administered at a dose of 3 MU daily. The baseline values were the following : CD4+ 515 cells/mmc (mean); HIV-RNA <50 copies/ml in all patients; HCV-RNA 28, 3 x 106 copies/ml. RESULTS: At 48 weeks, 10 patients (20%) achieved a biochemical and virological response according to an intention to treat analysis.Twenty four patients (48%) underwent a drop-out mainly by side effects related to overlapping toxicity of interferon and antiretroviral therapy. All the patients, who responded to the treatment, showed a fast relapse one month after the end of treatment. CONCLUSION: Although our results demonstrated a very poor outcome and a bad tolerance to interferon monotherapy, this approach should not be dropped out, mainly in patients at high risk for side effects and in those with cirrhosis who do not tolerate or are at increased risk for the use of ribavirin.