Use of an integrated modelling and simulation approach to develop a simplified peginterferon alfa-2a dosing regimen for children with hepatitis C.

AIM: The aim of the study was to simplify the dosing regimen of peginterferon alfa-2a in paediatric patients with chronic hepatitis C. METHODS: A population pharmacokinetic (PK) model was developed using PK data from 14 children aged 2-8 years and 402 adults. Simulations were produced to identify a simplified dosing regimen that would provide exposures similar to those observed in the paediatric clinical trials and in the range known to be safe/efficacious in adults. Model predictions were evaluated against observed adult and paediatric data to reinforce confidence of the proposed dosing regimen. RESULTS: The final model was a two compartment model with a zero order resorption process. Covariates included a linear influence of body surface area (BSA) on apparent oral clearance (CL/F) and a linear influence of body weight on apparent volume of distribution of the central compartment (V1 /F). A simplified dosing regimen was developed which is expected to provide exposures in children aged ≥5 years similar to the dosing formula used in the paediatric clinical trial and within the range that is safe/efficacious in adults. This simplified regimen is approved in the EU and in other countries for the treatment of chronic hepatitis C in treatment-naive children/adolescents aged ≥5 years in combination with ribavirin. CONCLUSION: Pre-existing adult PK data were combined with relatively limited paediatric PK data to develop a PK model able to predict exposure in both populations adequately. This provided increased confidence in characterizing PK in children and helped in the development of a simplified dosing regimen of peginterferon alfa-2a in paediatric patients.

The dose-response relationship of peginterferon alfa-2a and ribavirin in the treatment of patients coinfected with HIV-HCV.

PURPOSE: The relationship between peginterferon/ribavirin exposure and the probability of achieving a sustained virologic response (SVR) in HIV-HCV coinfected patients is not well described. We conducted a retrospective analysis of HIV-HCV coinfected patients randomized to 48 weeks of treatment with peginterferon alfa-2a (40 kD) 180 µg/week and ribavirin 800 mg/day in the multinational APRICOT study to define optimal exposure thresholds. METHOD: Actual drug exposure was estimated in 287 patients, taking into consideration dose reductions for adverse events or laboratory abnormalities. RESULTS: SVR overall and SVR in those completing treatment was, respectively, 29% and 37% among HCV genotype-1 patients and 59% and 68% among genotype non-1 patients. No patients with ≤40% exposure to ribavirin achieved an SVR. Receiver operating characteristic analysis identified that threshold exposures to both drugs of >75% (genotype-1) and >60% (genotype non-1) are associated with SVR. An existing generalized additive model populated with data from HCV monoinfected patients was updated to predict an overall SVR of 37% if genotype-1 patients received ribavirin 1000 or 1200 mg/day but at the cost of a higher incidence of anemia (23%). CONCLUSION: Completion of scheduled treatment and exceeding certain thresholds for exposure to peginterferon alfa 2a (40 kD) and ribavirin is associated with higher SVR rates.

Predicting efficacy and safety outcomes in patients with hepatitis C virus genotype 1 and persistently 'normal' alanine aminotransferase levels treated with peginterferon alpha-2a (40KD) plus ribavirin.

BACKGROUND: Currently, the approved dosage of ribavirin has not been studied in patients with 'normal' alanine aminotransferase (ALT) levels. METHODS: Modelling and simulations were performed using generalised additive models (GAMs) to predict the incidence of anaemia and rate of sustained virological response (SVR) in patients with hepatitis C virus (HCV) genotype 1 and persistently 'normal' ALT levels treated with peginterferon alpha-2a (40KD) 180 microg/week plus ribavirin 1000/1200 mg/day for 48 weeks. RESULTS: Model-based simulations predicted that SVR rates would increase from 39 to 48% if patients with genotype 1 and persistently 'normal' ALT levels had received the standard weight-adjusted dose of ribavirin. This was similar to the predicted 49% SVR rate for genotype 1 patients with elevated ALT levels. The incidence of anaemia was predicted to increase from 13% to 23% in patients with persistently 'normal' ALT activity and was higher than that predicted for patients with elevated ALT levels; however, the difference appeared to be largely explained by the higher proportion of women in the former group. CONCLUSIONS: Simulations based on GAM suggest that regimens for patients with HCV genotype 1 should include the standard weight-adjusted dose of ribavirin, as similar SVR rates are predicted to be achieved, regardless of patients' ALT status at baseline.

Predicting sustained virological response and anaemia in chronic hepatitis C patients treated with peginterferon alfa-2a (40KD) plus ribavirin.

AIM: To assess the likelihood of a sustained virological response (SVR) vs. the likelihood of anaemia in patients with chronic hepatitis C. METHODS: Data from 1732 patients treated with peginterferon alfa-2a (40KD) plus ribavirin in two randomized, multinational studies were pooled. Probabilities of SVR and anaemia were modelled using the generalized additive logistic model, with numerous clinical variables considered for entry into the model. Baseline haemoglobin was only considered in the analysis for anaemia. RESULTS: The probability of anaemia increased from 6 to 16% as a function of the ribavirin dose kg(-1) (12-16 mg kg(-1)), whereas the relationship between SVR and ribavirin dose kg(-1) was influenced by hepatitis C virus (HCV) genotype. The probability of an SVR was not influenced by the ribavirin dose kg(-1) in patients with HCV genotype 2 or 3 infection, but increased as a function of ribavirin dose kg(-1) in patients with HCV genotype 1 infection (40-50% increase in probability of SVR for 12-16 mg kg(-1) dose ribavirin increase). The probability of an SVR in patients included with HCV genotype 1 decreased with increasing HCV RNA level to about 3 million copies ml(-1), but was relatively independent of increasing HCV RNA level thereafter. In addition, older age, a higher ribavirin apparent oral clearance and cirrhosis had a negative impact on achieving an SVR, but improved with increasing alanine aminotransferase (ALT) quotient. Sex and ribavirin dose kg(-1) were the most important prognostic factors for anaemia, followed by baseline haemoglobin, age, baseline ALT quotient and cirrhosis. CONCLUSION: This study supports individualizing ribavirin dosages by HCV genotype and body weight, and highlights several clinical variables that influence the likelihood of an SVR compared with anaemia in chronic hepatitis C patients treated with peginterferon alfa-2a (40KD) plus ribavirin.

Pharmacokinetics of ribavirin in patients with hepatitis C virus.

AIM: A population pharmacokinetic analysis was performed using plasma concentration data (n = 7025) from 380 patients to examine the relationship between ribavirin dose and its pharmacokinetics. METHODS: Ribavirin pharmacokinetics were described by a three-compartment model with sequential zero-order and a first-order absorption processes. Interoccasion variability and food effects were included. RESULTS: Lean body weight (range 41-91 kg) was the only covariate with a clinically significant influence on ribavirin pharmacokinetics, affecting clearance (15.3-23.9 l h(-1)) and the volume of the larger peripheral compartment. CONCLUSION: The model provided a good description of the available data, confirmed by accurate estimates of parameter values and low residual variability (17%).