Optimizing the current therapy for chronic hepatitis C virus: peginterferon and ribavirin dosing and the utility of growth factors

Genetic variants at the ITPA locus protect against ribavirin-induced hemolytic anemia and dose reduction in an HCV G2/G3 cohort

OBJECTIVES

Two functional genetic variants in the inosine triphosphatase (ITPA) gene have been shown to be strongly associated with protection from ribavirin (RBV)-induced hemolysis. We aimed at evaluating this finding in a chronic hepatitis C genotype 2/3 cohort with a predominance of genotype 3 patients where available data are scarce. A second objective was to determine whether a protective association translated into the need for RBV reduction and hence a possible impact on treatment response.

METHODS

Overall, 457 patients were recruited from two trials of genotype 2/3 patients treated with pegylated interferon α-2b and weight-based RBV. rs1127354 and rs7270101 were genotyped and a composite ITPAase deficiency variable was graded according to the two single nucleotide polymorphisms. The primary endpoints were hemoglobin (Hb) decline from baseline and Hb decline of more than 3 g/dl at week 4.

RESULTS

Both single nucleotide polymorphisms and the composite ITPAase deficiency variable were strongly and independently associated with protection from a decline in Hb at week 4 in multivariate linear regression models (Prs1127354=7.0×10, Prs7270101=0.0036, PITPase deficiency variable =6.3×10). Patients with any degree of reduced ITPAase activity were less likely to have their RBV dose reduced (odds ratio 0.39, 95% confidence interval 0.16-0.96, P=0.040), although this did not translate into increased rapid viral response or sustained viral response (Prvr=0.93, Psvr=0.22).

CONCLUSION

We have confirmed a strong association between functional ITPA variants and RBV-induced hemolysis and showed protection from RBV dose reduction, although this did not translate into increased rapid viral response or sustained viral response.

Interferon-free regimens: the near future, the likely and the not so likely

Remarkable progress has been achieved in the treatment of chronic hepatitis C virus (HCV) since interferon was first used to treat this pathogen more than 20 years ago. This article reviews the mechanisms through which interferon is believed to suppress HCV and lead to SVR. These observations are used to speculate as to whether an all-oral antiviral cocktail could "cure" HCV in the near future.

Risk factors for relapse in chronic hepatitis C patients who have achieved end of treatment response

BACKGROUND AND AIM

Some patients with chronic hepatitis C experience virologic relapse even after achieving an end of treatment response. Prolonged therapy can be effective for helping such high-risk patients to avoid relapse. We aimed to identify factors predictive of virologic relapse in chronic hepatitis C patients who have achieved end of treatment response.

METHODS

We analyzed data from 242 chronic hepatitis C patients who achieved end of treatment response with peginterferon plus ribavirin therapy from 2003 to 2007.

RESULTS

Virologic relapse was identified in 32 patients (13.2%). We considered age, sex, body mass index, presence of diabetes, hemoglobin, platelet, alanine aminotransferase, stage of fibrosis, baseline hepatitis C virus RNA level, rapid virologic response, and adherence to drugs. For genotype 1 patients, older age (> or = 50 years) and higher baseline RNA level (> or = 2,000,000 IU/mL) were significantly correlated with occurrence of relapse. For genotypes 2 and 3, lower adherence to peginterferon (< 80%) was an independent risk factor for relapse.

CONCLUSIONS

In chronic hepatitis C patients who had achieved end of treatment response, risk factors for relapse were older age and higher baseline hepatitis C virus RNA level in genotype 1, and lower adherence to peginterferon in genotypes 2 and 3, which may be valuable to individualize duration of therapy.

Treatment of hepatitis C in 2011: what can we expect?

Treatment for chronic hepatitis C virus (HCV) infection is the combination of a peginterferon and ribavirin. Although a fixed duration of treatment (24 weeks for patients with genotypes 2 and 3 and 48 weeks for patients with all other genotypes) has been advocated, the best results are likely to be achieved when the duration of therapy is adjusted based on the time to response. According to the principles of response-guided therapy, patients with rapid virologic response have a high rate of sustained virologic response (SVR) and a low rate of relapse, and can be treated for 24 weeks regardless of genotype. In contrast, patients who become HCV RNA undetectable at a slower rate need a longer duration of therapy. Direct-acting antiviral agents are currently being developed to treat patients with HCV genotype 1. These agents will significantly increase rapid virologic response when used with peginterferon and ribavirin; according to the concepts of response-guided therapy, such treatment will yield high rates of SVR with 24 to 28 weeks of treatment.

Potential benefits of sequential inhibitor-mutagen treatments of RNA virus infections

Lethal mutagenesis is an antiviral strategy consisting of virus extinction associated with enhanced mutagenesis. The use of non-mutagenic antiviral inhibitors has faced the problem of selection of inhibitor-resistant virus mutants. Quasispecies dynamics predicts, and clinical results have confirmed, that combination therapy has an advantage over monotherapy to delay or prevent selection of inhibitor-escape mutants. Using ribavirin-mediated mutagenesis of foot-and-mouth disease virus (FMDV), here we show that, contrary to expectations, sequential administration of the antiviral inhibitor guanidine (GU) first, followed by ribavirin, is more effective than combination therapy with the two drugs, or than either drug used individually. Coelectroporation experiments suggest that limited inhibition of replication of interfering mutants by GU may contribute to the benefits of the sequential treatment. In lethal mutagenesis, a sequential inhibitor-mutagen treatment can be more effective than the corresponding combination treatment to drive a virus towards extinction. Such an advantage is also supported by a theoretical model for the evolution of a viral population under the action of increased mutagenesis in the presence of an inhibitor of viral replication. The model suggests that benefits of the sequential treatment are due to the involvement of a mutagenic agent, and to competition for susceptible cells exerted by the mutant spectrum. The results may impact lethal mutagenesis-based protocols, as well as current antiviral therapies involving ribavirin.

RNA viruses are associated with many important human and animal diseases such as AIDS, influenza, hemorrhagic fevers and several forms of hepatitis. RNA viruses mutate at very high rates and, therefore, can adapt easily to environmental changes. Viral mutants resistant to antiviral inhibitors are readily selected, resulting in treatment failure. The simultaneous administration of three or more inhibitors is a means to prevent or delay selection of resistant mutants. A new antiviral strategy termed lethal mutagenesis is presently under investigation. It consists of the administration of mutagenic agents to elevate the mutation rate of the virus above the maximum level compatible with virus infectivity, without mutagenizing the host cells. Since low amounts of virus are extinguished more easily, the combination of a mutagen and inhibitor was more efficient than a mutagen alone in driving virus to extinction. Here we show that foot-and-mouth disease virus replicating in cell culture can be extinguished more easily when the inhibitor guanidine is administered first, followed by the mutagenic agent ribavirin, than when both drugs are administered simultaneously. Interfering mutants that contribute to extinction were active in the presence of ribavirin but not in the presence of guanidine. This observation provides a mechanism for the advantage of the sequential versus the combination treatment. This unexpected effectiveness of a sequential treatment is supported by a theoretical model of virus evolution in the presence of the inhibitor and the mutagen. The results can have an application for future lethal mutagenesis protocols and for current antiviral treatments that involve the antiviral agent ribavirin when it acts as a mutagen.

The evolution of the major hepatitis C genotypes correlates with clinical response to interferon therapy

BACKGROUND

Patients chronically infected with hepatitis C virus (HCV) require significantly different durations of therapy and achieve substantially different sustained virologic response rates to interferon-based therapies, depending on the HCV genotype with which they are infected. There currently exists no systematic framework that explains these genotype-specific response rates. Since humans are the only known natural hosts for HCV-a virus that is at least hundreds of years old-one possibility is that over the time frame of this relationship, HCV accumulated adaptive mutations that confer increasing resistance to the human immune system. Given that interferon therapy functions by triggering an immune response, we hypothesized that clinical response rates are a reflection of viral evolutionary adaptations to the immune system.

METHODS AND FINDINGS

We have performed the first phylogenetic analysis to include all available full-length HCV genomic sequences (n = 345). This resulted in a new cladogram of HCV. This tree establishes for the first time the relative evolutionary ages of the major HCV genotypes. The outcome data from prospective clinical trials that studied interferon and ribavirin therapy was then mapped onto this new tree. This mapping revealed a correlation between genotype-specific responses to therapy and respective genotype age. This correlation allows us to predict that genotypes 5 and 6, for which there currently are no published prospective trials, will likely have intermediate response rates, similar to genotype 3. Ancestral protein sequence reconstruction was also performed, which identified the HCV proteins E2 and NS5A as potential determinants of genotype-specific clinical outcome. Biochemical studies have independently identified these same two proteins as having genotype-specific abilities to inhibit the innate immune factor double-stranded RNA-dependent protein kinase (PKR).

CONCLUSION

An evolutionary analysis of all available HCV genomes supports the hypothesis that immune selection was a significant driving force in the divergence of the major HCV genotypes and that viral factors that acquired the ability to inhibit the immune response may play a role in determining genotype-specific response rates to interferon therapy.

Chronic hepatitis C in patients co-infected with human immunodeficiency virus in Japan: a retrospective multicenter analysis

AIM

A nationwide survey in Japan revealed that nearly one-fifth of human immunodeficiency virus (HIV)-positive patients are co-infected with hepatitis C virus (HCV). We conducted a study to further analyze the features of liver disease in HIV-HCV co-infected patients.

METHODS

We analyzed 297 patients from eight hospitals belonging to the HIV/AIDS Network of Japan.

RESULTS

HCV genotypes 1, 2, 3, 4 and mixed genotypes were detected in 55.2, 13.7, 18.9, 0.9 and 11.3% of patients, respectively, in contrast to the fact that only genotypes 1 and 2 are detected in HCV mono-infected patients in Japan. This is compatible with the transmission of HCV through imported blood products contaminated by HCV. Sixteen of 297 HIV-HCV co-infected patients had advanced liver disease accompanied by ascites, hepatic encephalopathy or hepatocellular carcinoma. The average age of such patients was 41.1 +/- 14.0 years, which was much younger than that of HCV mono-infected patients with the same complications. The progression speed of liver disease estimated from the changes in the levels of serum albumin, bilirubin, or platelet was slower in patients who achieved sustained virological response with interferon treatment than in those who did not receive it. The overall sustained virological response rate to interferon treatment was 43.3%.

CONCLUSIONS

Our findings suggest that liver disease is more advanced in HIV-HCV co-infected patients than in HCV mono-infected patients, and interferon treatment may retard the progression of liver disease in such patients.

Trends in the Treatment of Chronic Hepatitis C Virus Infection

Despite reductions in the incidence of new hepatitis C virus infections, infections from previous decades continue to place a substantial burden on our health care system. Although the course of the disease is highly variable, approximately 20% to 30% of patients develop cirrhosis, end-stage liver disease, or hepatocellular carcinoma. Fortunately, treatment with our current standard of care, peginterferon a and ribavirin, can reduce the complications of chronic liver disease. However, these drugs are associated with significant adverse effects, many patients are ineligible for treatment, and only 50% are cured. Thus, there is a tremendous need to improve our current therapies and develop new compounds for this disease. This review highlights the transmission, pathophysiology, and course of illness; the pharmacokinetics, proposed mechanisms of action, adverse events, and potential drug interactions with peginterferon a and ribavirin; current treatment trends; the role of the pharmacist in the treatment of this disease; and investigational drugs in later stages of clinical development. Despite the initial hope that these new drugs would replace our current standard of care, it has become clear that ribavirin and peginterferon a will continue to play an important role in the treatment of chronic hepatitis C virus in the years to come.

What future for ribavirin?

The optimal therapy for patients with the chronic hepatitis C virus (HCV) is a combination of peginterferon and ribavirin. Treating HCV without ribavirin or prematurely discontinuing, frequently missing doses of ribavirin is associated with a significant decline in virological response, and an increase in both breakthrough viraemia and relapse. The major limitation of ribavirin is adverse events, the most common of which is haemolytic anaemia. Haemolysis is modest when ribavirin is utilized as monotherapy, but is significantly increased when combined with interferon or peginterferon. For these reasons, attempts to replace ribavirin with a less toxic alternative have been advanced. Unfortunately, even when ribavirin is replaced by a potent protease inhibitor, relapse is significantly increased and SVR is reduced. The future of HCV treatment is to combine peginterferon and ribavirin with several protease and/or polymerase inhibitors. Whether this strategy will allow ribavirin to be removed from the treatment paradigm remains to be proven. However, based on the results of clinical trials conducted to date, it is much more likely that peginterferon, not ribavirin, could be expendable.

Elevation of interleukin-18 in chronic hepatitis C: implications for hepatitis C virus pathogenesis

The outcome of hepatitis C virus (HCV) infection is determined by the interplay between the virus and the host immune response. Interleukin (IL)-18, an interferon-gamma-inducing factor, plays a critical role in the T helper type 1 (Th1) response required for host defence against viruses, and antibodies to IL-18 have been found to prevent liver damage in a murine model. The present study was conducted to investigate the possible role of IL-18 in the pathogenesis and persistence of HCV. IL-18 levels were measured in sera of 50 patients at various stages of HCV infection (resolved, chronic and cirrhosis) and compared with those of normal controls. IL-18 gene expression was studied in peripheral blood mononuclear cells (PBMC) from each group, and in liver biopsy tissue from patients with chronic hepatitis C. The mean levels of IL-18 in sera were markedly elevated in patients with chronic hepatitis and cirrhosis, and were reduced in patients with resolved HCV infection. The serum IL-18 concentrations were related to the Child-Pugh severity of liver disease in cirrhotic patients. There also existed a strong positive correlation of IL-18 levels with histological activity score and necrosis. IL-18 mRNA expression was significantly up-regulated in the PBMC of cirrhotic patients when compared with other groups, while in the liver, higher levels of IL-18 transcripts were expressed in patients with chronic hepatitis C. The results of our study indicate that IL-18 levels reflect the severity and activity of HCV infection, and may contribute to the pathogenesis and progression of liver disease associated with HCV.