Weight-based versus fixed dosing of peginterferon (40kDa) alfa-2a

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.

Peginterferon–α2a (40 kDa) (Pegasys®) for hepatitis B

Chronic hepatitis B virus is a serious and life threatening disease afflicting 350 million people worldwide, despite the availability of effective vaccines. Thus far, current monotherapy with conventional interferon-alpha, lamivudine and adefovir dipivoxil remains unsatisfactory. In addition, the use of conventional interferon-alpha needs to be administered subcutaneously three-times weekly and is associated with frequent adverse events. Although nucleoside/nucleotide analogs such as lamivudine and adefovir dipivoxil are well tolerated and can normalize serum alanine aminotransaminase rapidly, 1-year therapy with either lamivudine or adefovir dipivoxil results in low hepatitis B e antigen seroconversion rates. In hepatitis B e antigen-negative patients, most would relapse after lamivudine has been discontinued. Peginterferon-alpha2a, an immunomodulatory agent, is a new drug that has just completed Phase III clinical trials for the treatment of both hepatitis B e antigen-positive and -negative chronic hepatitis B virus infection. The advantage of peginterferon-alpha2a in achieving sustained virologic response over nucleoside/nucleotide analogs is particularly obvious in the hepatitis B e antigen-negative group. In both studies, sustained off-treatment response is superior to the use of monotherapy with lamivudine, and concomitant use of lamivudine and pegnterferon-alpha2a does not have advantages over the use of peginterferon-alpha2a alone. These recent data put peginterferon-alpha2a as the antihepatitis B virus therapy of choice, especially in young and motivated patients with chronic hepatitis B virus infection. However, despite the superiority of peginterferon-alpha2a over currently licensed nucleoside/nucleotide analogs, more research needs to be conducted in order to find the most optimal treatment regimen in our fight against chronic hepatitis B virus infection.

Do steatosis and steatohepatitis impact on sustained virological response (SVR) rates in patients receiving pegylated interferon and ribavirin for chronic hepatitis C infection?

The impact of steatosis on treatment response in chronic hepatitis C infection is controversial. The aim of this study was to determine whether steatosis +/- steatohepatitis on pre-treatment liver biopsy influenced sustained virological response (HCV RNA negative 6 months after completing therapy) in patients with chronic hepatitis C infection treated with pegylated interferon-alpha and ribavirin. One hundred and seventy-nine patients, median age 46 years (interquartile range 40-52), treated between 2001 and 2005. Histological evidence of steatosis was present in 93 patients (52%) and steatohepatitis in 33 patients (18%), 31 patients (17.3%) were cirrhotic. There were 106 (59%) responders, who were similar to non-responders in respect to gender, age, and pre-treatment ALT. On univariate analysis, infection with genotype 2 or 3 was associated with sustained virological response (odds ratio 6.5 (95% CI, 3.3-12.5); P < 0.0001), whereas cirrhosis and patient weight were associated with a reduced response (odds ratios 0.23 (95% CI, 0.11-0.48); P < 0.0001, and 0.97 (95% CI, 0.95-0.99); P < 0.01, respectively); steatohepatitis but not steatosis impacted on the likelihood of achieving sustained virological response (odds ratio 0.37 (95% CI, 0.17-0.77); P = 0.009, and P = 0.18, respectively). Multivariate analysis revealed that infection with genotype 1 or 4 (odds ratio 0.09 (95% CI, 0.03-0.32); P < 0.001) and pre-treatment weight (odds ratio 0.94 (95% CI, 0.90-0.98); P = 0.002) were the only variables associated independently with sustained virological response. In chronic hepatitis C infection, although steatosis was associated with steatohepatitis, neither was shown to affect sustained virological response, which was influenced by genotype, patient weight and the presence of cirrhosis.

Hepatitis C and metabolic syndrome

Hepatitis C virus (HCV) and the hepatic manifestation of metabolic syndrome, nonalcoholic fatty liver disease, are the two major causes of chronic liver disease worldwide. Liver histology of both diseases can be associated with steatosis, oxidative stress and fibrogenesis. Although better defined for HCV, approximately 20% of patients with these diseases can also develop cirrhosis or hepatocellular carcinoma. In recent years, it has become clear that the presence of metabolic syndrome and nonalcoholic fatty liver disease negatively impacts HCV-related outcomes, while simultaneously, the progression of HCV may have metabolic consequences in that it encourages or exacerbates insulin resistance. A growing body of evidence suggests that successful treatment of HCV may rely on understanding and addressing the complex and often mutually confounding relationship between HCV and the individual elements that comprise metabolic syndrome.

Assessment of the efficacy of reducing peginterferon alpha-2a and ribavirin dose on virologic response in Koreans with chronic hepatitis C

BACKGROUND/AIMS

The virologic response of Koreans to combination therapy for chronic hepatitis C is similar to westerns; however, dose modification occurs more frequently in Koreans. We evaluated the rates of peginterferon alpha-2a and ribavirin dose modifications and their effect on the virologic response in Koreans.

METHODS

Patients with detectable HCV RNA and enrolled from multicenters were treated with peginterferon alpha-2a (180 microg/week) and ribavirin (800 mg/day) for 24 weeks (genotype non-1, n=37) or peginterferon alpha-2a (180 microg/week) and ribavirin (1,000-1,200 mg/day) for 48 weeks (genotype 1, n=55).

RESULTS

Early virologic response (EVR) and sustained virologic response (SVR) were 77.2% (genotype 1, 75%; non-1, 81%) and 66.3% (genotype 1, 56%; non-1, 81%), respectively. The frequency of dose modification was 32.6% within the first 12 weeks and 52.2% during the entire treatment period. No difference was found in SVR regardless of dose modification. However, the SVR for patients using >or=80% of the peginterferon dose was significantly higher than for those using <80% (81.3 vs. 50.0%, p=0.007), despite varying ribavirin doses. No difference was found in SVR regardless of whether the ribavirin dose was <80% or not. These results did not change based on genotype.

CONCLUSIONS

We suggest that using at least 80% of the peginterferon alpha-2a dose in Koreans not only maintains SVR but also reduces drug side effects during the entire treatment period. A lower dose of ribavirin may be as efficacious as a standard dose.

Pharmacodynamics of peginterferon alpha-2a and peginterferon alpha-2b in interferon-naïve patients with chronic hepatitis C: a randomized, controlled study

BACKGROUND

Peginterferon alpha-2a and alpha-2b, the two commercially available pegylated interferons, have different pharmacokinetic properties that produce differing abilities to suppress replication of the hepatitis C virus.

AIM

To compare the pharmacodynamics of peginterferon alpha-2a and peginterferon alpha-2b in interferon-naive patients with chronic hepatitis C.

METHODS

Patients were randomized to receive peginterferon alpha-2a, 180 microg (n = 10) or peginterferon alpha-2b 1.0 microg/kg (n = 12) once weekly. The enzymatic activity of 2'5'-oligoadenylate synthetase and levels of neopterin and beta(2)-microglobulin were measured at baseline and at 24, 48, 120 and 168 h.

RESULTS

Oligoadenylate synthetase activity and serum neopterin and beta(2)-microglobulin concentrations did not differ significantly between the two patient groups at any time point, nor was there a significant correlation between the serum area under the concentration-time curve of either peginterferon and the area under the concentration-time curve for 2',5'-oligoadenylate synthetase, neopterin and beta(2)-microglobulin. The area under the concentration-time curves calculated for these three markers did not correlate with body mass index stratified at <25 and >or=25 kg/m(2) for either peginterferon.

CONCLUSIONS

Despite pharmacokinetic differences between peginterferon alpha-2a and peginterferon alpha-2b, the pharmacodynamic profiles of the two formulations appear to be comparable.

Impact of obesity on treatment of chronic hepatitis C

Obesity and the metabolic syndrome have hepatic manifestations, including steatosis and progression of fibrosis. In individuals with chronic hepatitis C, obesity is associated with inflammation, insulin resistance, steatosis, progression of fibrosis, and nonresponse to treatment with interferon or peginterferon alpha and ribavirin. Patients with both hepatitis C and obesity-related nonalcoholic fatty liver disease are at greater risk for more advanced liver disease. We review the mechanisms by which obesity may be associated with decreased efficacy of interferon-based therapies in individuals with chronic hepatitis C and the therapeutic strategies that may increase the effectiveness of these therapies in obese individuals.

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 μg regardless of body weight, whereas peginterferon alpha-2b is dosed by body weight at 0.5–1.5 μg/kg. Body-weight 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 μg ( n=10) or peginterferon alpha-2b 1.0 μg/kg ( n=12). Ribavirin was dosed by body weight at 1000 mg/day (≤75 kg) 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.

Review article: pegylated interferons: chemical and clinical differences

Pegylated interferon therapy for the treatment of chronic hepatitis C virus provides significant increases in sustained virological response rates compared with standard interferons. Two pegylated interferons are now available and are used in conjunction with ribavirin to maximize response rates in infected patients. The two pegylated interferons, peginterferonalpha-2a and peginterferonalpha-2b, differ substantially in terms of their chemical and structural characteristics, pharmacokinetic and pharmacodynamic properties, and dosing and administration. A full understanding of the differences between the two drugs is important to maximize the clinical benefits. Controlled studies designed to characterize the effects of the two drugs on viral kinetics and sustained virological response rates are emerging and may help to shed additional light on the use of these compounds in patients with chronic hepatitis C.

Peginterferon alfa-2a: A review of approved and investigational uses

BACKGROUND

In October 2002, the US Food and Drug Administration approved peginterferon alfa-2a for the management of chronic hepatitis C virus (HCV) infection. The addition of polyethylene glycol (PEG) moiety to the interferon (IFN) molecule results in a product with altered pharmacokinetic properties.

OBJECTIVE

The aim of this article is to review the pharmacology, medications interactions, adverse events (AEs), and approved or investigational uses of PEG-IFN alfa-2a for viral hepatitis and oncologic conditions.

METHODS

Relevant articles were identified through searches of MEDLINE (1980-July 2003) and EMBASE (1980-July 2003). Search terms included, but were not limited to, peginterferon alfa-2a, pharmacokinetics, pharmacology, pharmacodynamics, and therapeutic use, as well as terms for specific disease states and AEs. Further publications were identified from citations of resulting papers.

RESULTS

Pegylation of IFN alfa-2a results in major changes in the pharmacokinetics of the product. Absorption is prolonged and serum concentrations are sustained over the dosing regimen. PEG-IFN alfa-2a has been shown to be more effective with or without ribavirin (RBV), in the management of treatment-naive patients with chronic HCV infection, than unmodified IFN alfa-2a with or without RBV. Results in other disease states are still preliminary. AEs are similar, in incidence and severity, to those occurring with unmodified IFN. They include earlier hematologic symptoms and fewer influenza-like symptoms. Drug-drug interactions are the same as those occurring with the unmodified IFN product.

CONCLUSIONS

The pharmacokinetic profile of IFN alfa-2a is improved by pegylation, which enables less frequent administration and results in improved efficacy with a similar side-effect profile. Combination of PEG-IFN alfa-2a with RBV is associated with a greater chance of achieving a sustained virologic response in treatment-naive patients with chronic HCV, compared with unmodified IFN alfa-2a/RBV combinations. Documentation of efficacy in other conditions awaits results of controlled clinical trials.

Improved biological and transcriptional activity of monopegylated interferon-α-2a isomers

The addition of polyethyleneglycol (PEG) side chains to interferon alpha-2a improves the serum stability and clinical efficacy. Current commercial PEG-INF formulations such as PEGASYS are heterogeneous and contain multiple monopegylated isomers. We have analyzed the activity of nine, purified monopegylated variants in antiproliferative, antiviral and binding assays, together with a global transcriptional analysis using DNA oligonucleotide microarrays. We show a direct correlation between biological and transcriptional activity for all isomers and an inversed correlation between IFN-receptor 2a affinity and signal transduction. Two out of nine positional isomers have a higher specific biological and transcriptional activity than the mixture, which can be explained by unique structural features of interferon signaling, which involves two distinct receptors. The possible clinical implications are discussed, which might guide the development of pegylated interferons with improved pharmacological properties.

Peginterferon-alpha2a (40 kDa) for chronic hepatitis C

Pegylated IFN-alpha(2a) (PEG-IFN-alpha(2a) [40 kDa]; Pegasys, Hoffmann-La Roche) is a new subcutaneous formulation of IFN-alpha(2a), produced by its attachment to a 40 kDa branched polyethylene glycol moiety by a stable amide bond. PEG-IFN-alpha(2a) 180 micro g once-weekly has enhanced pharmacokinetic and pharmacodynamic properties which translate into significantly improved efficacy and similar safety and tolerability compared with IFN-alpha in patients with chronic hepatitis C even with underlying cirrhosis. The combination of PEG-IFN-alpha(2a) (40 kDa) plus ribavirin produces significantly better sustained virological responses than the combination of IFN-alpha(2b) and ribavirin, while it is accompanied by a similar or even lower incidence of adverse events and better quality of life. PEG-IFN-alpha(2a) (40 kDa) is the first pegylated IFN-alpha for which evidence-based recommendations can be made on optimum therapy duration and ribavirin dose according to HCV genotype. PEG-IFN-alpha(2a) (40 kDa) is expected to improve the efficacy and tolerability of treatment for chronic hepatitis C.