Epidemiology of thrombocytopenia in patients with chronic hepatitis C: more than meets the eye

Pathogenesis of Thrombocytopenia in Chronic HCV Infection: A Review

A large proportion of patients with chronic hepatitis C have associated thrombocytopenia (TCP). Due to bleeding risks, TCP, when severe, can limit diagnostic and therapeutic procedures, treatments, and increases risk of complications, especially excessive bleeding. It is important to understand the mechanisms that cause TCP in order to manage it. In general, TCP can be due to increased destruction or decreased production. Proposed mechanisms of increased destruction include autoantibodies to platelets and hypersplenism with sequestration. Proposed mechanisms of decreased production include virus-induced bone marrow suppression and decreased TPO production. Autoantibodies directed against platelet surface antigens have demonstrated an inverse correlation with platelet counts. Hypersplenism with sequestration involves the interaction of portal hypertension, splenomegaly, and platelet destruction. Decreased production mechanisms involve appropriate and inappropriate levels of TPO secretion. There is limited evidence to support viral-induced bone marrow suppression. In contrast, there is strong evidence to support low levels of TPO in liver failure as a major cause of TCP. TPO-agonists, specifically eltrombopag, have been shown in hepatitis C patients to increase platelet counts without reducing portal hypertension or splenomegaly. We conclude that TCP in hepatitis C virus-induced liver disease is often multifactorial, but an understanding of the mechanisms can lead to judicious use of new drugs for treatment.

Bayesian Population Pharmacokinetic Modeling of Eltrombopag in Chronic Hepatitis C Patients

BACKGROUND AND OBJECTIVES

Eltrombopag is a thrombopoietic growth factor that is approved for the treatment of thrombocytopenia in chronic hepatitis C virus (HCV) patients. We aimed to describe eltrombopag population pharmacokinetics in hepatitis C patients. Bayesian statistical approach will be applied to screen for patients' characteristics associated with eltrombopag pharmacokinetic parameters.

METHODS

A population pharmacokinetic analysis was conducted using WinBUGS version 1.4.3. Data from 483 individuals with chronic HCV infection were analyzed. This analysis is a secondary analysis of two clinical studies (ENABLE1 and ENABLE2) sponsored by GlaxoSmithKline. Several patients' characteristics were examined as possible covariates of the population pharmacokinetic model. Prior information from previous studies was incorporated in the bayesian model as prior distribution to estimate pharmacokinetic parameters.

RESULTS

A two-compartment pharmacokinetic model with first-order absorption with exponential error model best fit the data. We identified East Asian race and total bilirubin level as predictors of eltrombopag clearance. Typical value for distributional clearance was 0.762 L/h (95% Bayesian credible set, 0.703-0.826), for volume of distribution of the central and peripheral compartments were 12 L (10.9-13.4) and 10.9 L (10.4-11.5), and for absorption lag time was 0.947 h (0.918-0.977). Assuming an average total bilirubin of 21.7 µmol/L, the typical elimination clearance value for an East Asian patient was 0.14 L/h and for other races was 0.20 L/h.

CONCLUSIONS

Eltrombopag pharmacokinetic behavior was described using population bayesian approach. This model can be applied to optimize eltrombopag dosing in order to reduce the incidence of thrombocytopenia in HCV-infected patient receiving interferon-based therapy.

Non-cirrhotic thrombocytopenic patients with hepatitis C virus: Characteristics and outcome of antiviral therapy

BACKGROUND AND AIM

Thrombocytopenia is frequently observed in patients with chronic hepatitis C virus (HCV) infection and cirrhosis, although it can also be observed in patients without cirrhosis by a virus-mediated phenomenon. This study assessed the prevalence, characteristics, and outcomes of antiviral therapy in patients with chronic HCV infection and thrombocytopenia not associated with cirrhosis.

METHODS

The study included 1268 patients with HCV infection and thrombocytopenia enrolled in the phase 3 ENABLE studies that assessed the impact of eltrombopag on achieving a sustained virologic response to pegylated interferon and ribavirin. The study population was subdivided according to baseline FibroSURE test results into patients with non-cirrhosis (FibroSURE < 0.4) and cirrhosis-related (FibroSURE ≥ 0.75) thrombocytopenia.

RESULTS

Compared with patients with cirrhosis-related thrombocytopenia (n = 995; 78.5%), non-cirrhotic patients with thrombocytopenia (n = 59; 4.6%) were younger (mean age [95% confidence interval (CI)]: 43.9 [40.7-47.2] vs 52.7 [52.2-53.3] years; P < 0.0001), predominantly female (64% [51-76] vs 30% [27-33]; P < 0.0001), and less frequently had a Model for End-Stage Liver Disease score ≥ 10 (24% [14-37] vs 45% [42-49]; P = 0.0012), low albumin levels (≤ 35 g/L; 2% [0-9] vs 32% [29-35]; P < 0.0001), and prevalence of diabetes mellitus (3% [0-12] vs 21% [19-24]; P = 0.0005). The sustained virologic response rate was higher in non-cirrhotic patients with thrombocytopenia (46% [95% CI, 33-59] vs 16% [14-18]; P < 0.0001).

CONCLUSIONS

Patients with thrombocytopenia associated with HCV who have lower FibroSURE test results may have better preserved liver function and higher sustained virologic response rates than patients with cirrhosis.

Eltrombopag in patients with chronic hepatitis C and thrombocytopenia

ABSTRACT: 

Eltrombopag is a thrombopoietic drug that acts by interacting with the TPO receptor and stimulates megakaryocytopoiesis and platelet production. Thrombocytopenia is a fairly frequent hematological abnormality in patients with chronic liver disease, and may represent an obstacle to interferon-based antiviral therapy in patients with chronic HCV infection who are otherwise good candidates for treatment. In large, multicenter, randomized, placebo-controlled studies, eltrombopag consistently enabled thrombocytopenic chronic hepatitis C patients to be treated with interferon-based therapy and, as an adjunct to antiviral therapy, has shown to be able to increase the sustained virologic response rate to treatment. The safety profile of the drug, with particular attention to the risk of thromboembolic events and the potential for hepatic decompensation, should be taken into account when planning treatment. The aim of this article is to review the information currently available regarding the pharmacokinetics, clinical efficacy and side-effect profile of eltrombopag, and to assess the role of this drug into the current and future hepatitis C treatment paradigm.

Eltrombopag in patients with chronic liver disease

INTRODUCTION

Thrombocytopenia may represent a barrier to optimal management of chronic liver disease patients undergoing invasive procedures, or who need to be treated with interferon-based antiviral therapy. Eltrombopag is a thrombopoietic drug that acts upon binding thrombopoietin receptor and stimulates megakaryocytopoiesis and platelet production.

AREAS COVERED

A summary of the preclinical studies and of studies carried out in patients with chronic liver disease with eltrombopag are presented in this paper. Data are based on abstracts from journal articles and international conferences found in a PubMed search of literature published up to November 2012.

EXPERT OPINION

Eltrombopag has shown to be capable of reducing the need for platelet transfusion in thrombocytopenic patients with advanced liver disease undergoing invasive procedures and help increase the sustained virological response rate to interferon-based antiviral therapy in patients with chronic hepatitis C who were poor candidates to treatment because of thrombocytopenia. In chronic liver disease patients, the possible benefits of eltrombopag administration should be accurately weighed against the adverse events profile of the drug due to possible concerns regarding the occurrence of thromboembolic events and the potential for decompensation of chronic liver disease.

An update on the management of hepatitis C: consensus guidelines from the Canadian Association for the Study of the Liver

Chronic hepatitis C remains a significant medical and economic burden in Canada, affecting nearly 1% of the population. Since the last consensus conference on the management of chronic hepatitis C, major advances have warranted a review of recommended management approaches for these patients. Specifically, direct-acting antiviral agents with dramatically improved rates of virological clearance compared with standard therapy have been developed, and several single nucleotide polymorphisms associated with an increased probability of spontaneous and treatment-induced viral clearance have been identified. In light of this new evidence, a consensus development conference was held in November 2011; the present document highlights the results of the presentations and discussions surrounding these issues. It reviews the epidemiology of hepatitis C in Canada, preferred diagnostic testing approaches and recommendations for the treatment of chronically infected patients with the newly approved protease inhibitors (boceprevir and telaprevir), including those who have previously failed pegylated interferon and ribavirin therapy. In addition, recommendations are made regarding approaches to reducing the burden of hepatitis C in Canada.

Peripheral blood cytopaenia limiting initiation of treatment in chronic hepatitis C patients otherwise eligible for antiviral therapy

BACKGROUND

In patients with chronic hepatitis C virus (HCV) infection, the presence of peripheral blood cytopaenia may represent an obstacle to pegylated interferon and ribavirin treatment.

AIMS

To evaluate the prevalence of anaemia, neutropaenia and thrombocytopaenia potentially limiting initiation of pegylated interferon and ribavirin treatment in patients with chronic HCV infection who were otherwise eligible for antiviral therapy.

METHODS

We studied 3059 consecutive anti-HCV and HCV-RNA positive patients referred to our centre to be evaluated for antiviral therapy from June 2002 to May 2011. The European Association for the Study of Liver HCV guidelines were applied to assess eligibility for antiviral therapy.

RESULTS

In the study cohort, 1,521 patients (49.7%) were not eligible for treatment because of reasons different from haematological abnormalities. In the remaining 1,538 patients the overall prevalence of any peripheral blood cytopaenia potentially preventing patients from being treated with antiviral therapy was 15.1%. In particular, anaemia (haemoglobin level < 12 g/dL for women, <13 g/dL for men) was a relative contraindication to treatment in 8.9% (137/1,538) of the patients, while thrombocytopaenia (platelet count cut-off, 90 × 10(9) /L) and neutropaenia (absolute neutrophil count < 1.5 × 10(9) /L) limited treatment in 6.5% (100/1358) and 3.2% (48/1358) of patients respectively. These haematological abnormalities were more prevalent in patients with older age (P < 0.004) and cirrhosis (P < 0.001).

CONCLUSIONS

The presence of peripheral blood cytopaenia may potentially limit initiation of antiviral therapy in one in every seven patients with chronic HCV infection who are otherwise eligible for treatment.