Population pharmacokinetics of peginterferon alfa-2b in pediatric patients with chronic hepatitis C

Individualized dosing guidelines for PEGasparaginase and factors influencing the clearance: a population pharmacokinetic model

Considerable inter- and intra-patient variability exist in serum activity levels of PEGasparaginase, essential for pediatric acute lymphoblastic leukemia treatment. A population pharmacokinetic (popPK) model was developed, identifying patient characteristics explaining these variabilities. Patients (n=92) were treated according to the DCOG ALL-11 protocol, using therapeutic drug monitoring to individualize the PEGasparaginase doses. Non-linear mixed effects modeling (NONMEM) was used to analyze the popPK evaluating several covariates. The final model was validated using an independent database (n=28). Guidelines for starting doses and dose adjustments were developed. A one-compartment model with time-dependent clearance adequately described the popPK. Normalization of clearance and volume of distribution by body surface are (BSA) reduced inter-individual variability. Clearance was 0.084 L/day/m2 for 12.7 days, increasing with 0.082 L/day/m2/day thereafter. Clearance was 38% higher during an infection, and 11-19% higher during induction treatment than intensification and maintenance (p<0.001). Targeting an asparaginase activity level of 100 IU/L, a loading dose of 800 IU/m2 (induction) and 600 IU/m2 (intensification) is advised. In conclusion, variability of PEGasparaginase activity levels can be explained by BSA, treatment phase and the occurrence of an infection. With this popPK model, PEGasparaginase treatment can be individualized further, taking into account these covariates and the dosing guidelines provided.

Population pharmacokinetics of peginterferon α2a in patients with chronic hepatitis B

There were significant differences in response and pharmacokinetic characteristics to the peginterferon α2a treatment among Chronic Hepatitis B (CHB) patients. The aim of this study is to identify factors which could significantly impact the peginterferon α2a pharmacokinetic characteristics in CHB patients. There were 208 blood samples collected from 178 patients who were considered as CHB and had been treated with peginterferon α2a followed by blood concentration measurement and other laboratory tests. The covariates such as demographic and clinical characteristics of the patients were retrieved from medical records. Nonlinear mixed-effects modeling method was used to develop the population pharmacokinetic model with NONMEM software. A population pharmacokinetic model for peginterferon α2a has been successfully developed which shows that distribution volume (V) was associated with body mass index (BMI), and drug clearance (CL) had a positive correlation with creatinine clearance (CCR). The final population pharmacokinetic model supports the use of BMI and CCR-adjusted dosing in hepatitis B virus patients.

PEGylated interferon displays differences in plasma clearance and bioavailability between male and female mice and between female immunocompetent C57Bl/6J and athymic nude mice

Gender and immune status can considerably impact on the pharmacokinetics (PK) of macromolecular and small molecule drugs. However, these effects are often not considered in drug development. We aimed to quantitatively evaluate effects of gender and immune status on the PK of PEGylated interferon in frequently used murine models. Chronically cannulated female athymic nude and female and male immunocompetent C57Bl/6J mice (n = 24 in total) received a single intravenous or subcutaneous (s.c.) dose of PEGylated interferon. Serial blood samples were taken for 48 h. Noncompartmental analysis and population PK modeling with covariate analysis were performed to evaluate the data. The PK of PEGylated interferon followed a three compartment disposition model with two sequential compartments for s.c. absorption. Female nude mice had significantly higher plasma clearance than C57Bl/6J mice (0.503 vs. 0.397 mL/h). Male mice had a slower absorption rate constant (0.138 h(-1)) and extent (46.2%) of s.c. absorption than female mice (0.274 in C57Bl/6J and 0.374 h(-1) in nude, 60.8% in both). Thus, gender and immune status significantly impacted on important PK parameters of PEGylated interferon in murine models commonly utilized in drug development. It is critical to take into account these differences when choosing animal models and conducting translational pharmacology research.

Viral hepatitis C therapy: pharmacokinetic and pharmacodynamic considerations

Chronic hepatitis C is a global health problem. To prevent or reduce complications, the hepatitis C virus (HCV) infection needs to be eradicated. There have been several developments in treating these patients since the discovery of the virus. As of 1 January 2014, the drugs that are approved for treatment of chronic HCV infection are peginterferon-α, ribavirin, boceprevir, telaprevir, simeprevir and sofosbuvir. In this review we provide an overview of the clinical pharmacokinetic characteristics of these agents by describing their absorption, distribution, metabolism and excretion. In the pharmacodynamic part we summarize what is known about the relationships between the pharmacokinetics of each drug and efficacy or toxicity. We briefly discuss the pharmacokinetics and pharmacodynamics of chronic hepatitis C treatment in special patient populations, such as patients with liver cirrhosis, renal insufficiency or HCV/HIV coinfection, and children. With this knowledge, physicians, pharmacists, nurse practitioners, etc. should be educated to safely and effectively treat HCV-infected patients.