Hemolytic anemia induced by ribavirin therapy in patients with chronic hepatitis C virus infection: role of membrane oxidative damage

Single and combined IL28B, ITPA and SLC28A3 host genetic markers modulating response to anti-hepatitis C therapy

Advances in hepatitis C pharmacogenomics identified modulations of a sustained virologic response (SVR) by frequent IL28B gene variants and of ribavirin-induced hemolysis by frequent ITPA gene variants. These associations have been widely reproduced in various ethnicities, clinical settings and hepatitis C viral genotypes. The IL28B minor alleles rs8099917G, rs12979860T and rs12980275G have been associated with non-SVR whereas the ITPA minor alleles rs1127354A and rs7270101C were associated with less hemolytic side effects, an effect also attributed to a nucleoside transporter gene SLC28A3 rs10868138G/rs56350726T haplotype. The significance levels of these associations, especially in genome-wide studies, were very high. We nevertheless tested how good clinical outcomes of peginterferon α/ribavirin therapy, such as SVR or hemolytic side effects, were predicted by these variants. An analysis in an example dataset of 115 patients revealed that the prediction of non-SVR or hemolysis by single variants was often only slightly better than guessing. Using combinations of IL28B variants provided a higher accuracy (64.5%) of predicting non-SVR than with single IL28B variants (accuracy 60-63%). Similarly, a decline in blood hemoglobin by ≥3 g/dl could be better predicted at an accuracy of 70% (10% better than guessing) with a combination of an ITPA variant with a nucleoside transporter gene (SLC28A3) haplotype. Thus, genotyping information about single IL28B or ITPA variants is reproducibly and statistically significantly associated with hepatitis C therapy outcomes; however, the clinical predictive utility of single variants can be increased by combinations of genotypes.

Pharmacological exposure to ribavirin: a key player in the complex network of factors implicated in virological response and anaemia in hepatitis C treatment

Ribavirin remains today a pivotal drug in the treatment of hepatitis C; in standard double therapy, as well as in triple combination with direct antiviral agents, ribavirin reduces relapse and can double the sustained virological response obtained with peginterferon alone or in association with direct antiviral agents. In the complex network of interacting factors determining sustained virological response independently of known predictive factors related to host and virus, two modern tools are emerging: polymorphisms in the IL28B gene and very early exposure to ribavirin. The use of a pharmacokinetic-pharmacodynamic model of early ribavirin exposure to adjust the dose individually would help promote a safer ribavirin use and improve sustained virological response. The variability of the influence of ribavirin exposure on anaemia is probably genetically determined; however, the low prevalence of the implicated protective alleles of the inosine triphosphate pyrophosphatase gene could explain their lack of influence on sustained virological response.

Translating pharmacogenetics into clinical practice: interleukin (IL)28B and inosine triphosphatase (ITPA) polymophisms in hepatitis C virus (HCV) infection

Hepatitis C virus (HCV) infection is frequently characterized by evolution to chronicity and by a variable clinical course of the disease. The clinical heterogeneities of HCV infection and the imperfect predictability of the response to interferon (IFN) have suggested the need to search for a genetic basis of clinical features. This led to the discovery of genetic polymorphisms playing a major role in the evolution of infection, as well as on treatment response and adverse effects. This review will cover recent reports on the subject, focusing on the potential use of the new genetic markers in the diagnostic algorithm for the stratification of patients for personalized antiviral regimens.

Common genetic polymorphism of ITPA gene affects ribavirin-induced anemia and effect of peg-interferon plus ribavirin therapy

An association between a single nucleotide polymorphism (SNP) in the inosine triphosphate pyrophosphatase (ITPA) gene and reduction of hemoglobin during peg-interferon plus ribavirin combination therapy for patients with chronic hepatitis C virus (HCV) infection has been reported. However, the effect of the SNP on outcome of therapy has not been fully elucidated. Factors associated with anemia during combination therapy, including rs1127354 genotype, were analyzed in 1,002 treated patients. The effect of the SNP on outcome of therapy was analyzed in a subset of 830 patients with genotype 1. A rapid initial decrease in hemoglobin levels was observed in patients with rs1127354 genotype CC compared with a slow decrease in non-CC patients. Cumulative reduction of ribavirin was significantly more frequent in genotype CC patients than non-CC patients (odds ratio 1.928, P = 8.6 × 10(-8) ). The frequency of patients who received at least the recommended 80% of scheduled ribavirin was significantly lower among genotype CC patients, especially among those who had pretreatment hemoglobin levels between 13.5 and 15 g/dl (P < 0.03), and the sustained viral response rate was significantly lower in this group of patients. Independent predictive factors for sustained virological response included a SNP in the IL28B locus (rs809991), age, fibrosis, ITPA SNP rs1127354 as well as pretreatment hemoglobin levels. Our data suggests that measures to prevent anemia should be considered for patients who have pretreatment hemoglobin levels less than 13.5 g/dl or who have rs1127354 genotype CC and pretreatment hemoglobin levels between 13.5 and 15 g/dl.

Pure red cell aplasia caused by pegylated interferon-α-2a plus ribavirin in the treatment of chronic hepatitis C

Pure red cell aplasia (PRCA) is a rare hematological disorder which is characterized by severe anemia, reticulocytopenia and almost complete absence of erythroid precursors in bone marrow. The pathophysiology of PRCA may be congenital or acquired. To our knowledge, there is only one case report in the English literature of PRCA after pegylated interferon combination therapy for chronic hepatitis C. We report a second case of PRCA after pegylated interferon combination treatment for chronic hepatitis C. The diagnosis of PRCA was confirmed by the typical findings of bone marrow biopsy. The possible etiologies of our case are also discussed in this paper.

Should ribavirin be used to treat hepatitis C in dialysis patients?

Hepatitis C virus infection adversely affects outcomes in patients with chronic kidney disease undergoing maintenance dialysis. Pegylated interferon and ribavirin, the standard-of-care treatment in patients with intact renal function, is associated with severe side effects, toxicity, and high dropout rates in this population. Ribavirin has an important role in maintaining antiviral response following completion of therapy and increases sustained viral response (SVR) rates. However, the use of ribavirin in dialysis patients has been limited by the high frequency of severe hemolytic anemia and is currently reserved for study protocols and highly selected candidates treated at experienced centers. Encouraging data from small trials have shown a significant increase in SVR rates with the use of different dosing regimens of ribavirin in addition to interferon-based therapy and aggressive erythroid-stimulating agent support in dialysis patients. Use of ribavirin in selected dialysis patients, particularly renal transplant candidates, by experienced clinicians is appropriate.

Inosine triphosphate protects against ribavirin-induced adenosine triphosphate loss by adenylosuccinate synthase function

BACKGROUND & AIMS

Genetic variation of inosine triphosphatase (ITPA) causing an accumulation of inosine triphosphate (ITP) has been shown to protect patients against ribavirin (RBV)-induced anemia during treatment for chronic hepatitis C infection by genome-wide association study (GWAS). However, the biologic mechanism by which this occurs is unknown.

METHODS

We examined whether ITP can be used by adenosine triphosphatase (ATPase) in human erythrocytes or recombinant human adenylosuccinate synthase (ADSS). RBV-induced adenosine triphosphate (ATP) reduction in erythrocytes was compared with the genetically determined low or normal activity of ITPA, leading respectively to high or normal ITP levels.

RESULTS

Although ITP is not used directly by human erythrocyte ATPase, it can be used for ATP biosynthesis via ADSS in place of guanosine triphosphate (GTP). With RBV challenge, erythrocyte ATP reduction was more severe in the wild-type ITPA genotype than in the hemolysis protective ITPA genotype. This difference also remains after inhibiting adenosine uptake using nitrobenzylmercaptopurine riboside (NBMPR). Interestingly, the alleviation of ATP reduction by the hemolysis protective ITPA genotype was canceled by the ADSS inhibitor 6-mercaptoethanol (6-MP).

CONCLUSIONS

ITP confers protection against RBV-induced ATP reduction by substituting for erythrocyte GTP, which is depleted by RBV, in the biosynthesis of ATP. Because patients with excess ITP appear largely protected against anemia, these results confirm that RBV-induced anemia is due primarily to the effect of the drug on GTP and consequently ATP levels in erythrocytes.

Pegylated-interferon-α(2a) in clinical practice: how to manage patients suffering from side effects

INTRODUCTION

The goal of antiviral therapy in patients with chronic hepatitis C is to slow or halt the progression of fibrosis and prevent the development of cirrhosis. Accordingly, antiviral treatment is proposed for a large population of patients with chronic hepatitis.

AREAS COVERED

The standard-of-care for chronic hepatitis C is the combination of pegylated IFN (PEG-IFN) and ribavirin. The use of these drugs has been correlated with a range of adverse effects, including influenza-like symptoms, hematological changes and neuropsychiatric disturbances. The effects of these adverse events associated with PEG-IFN therapy are manifold and are a major reason why patients decline or stop therapy. This review addresses the screening for adverse event risk factors and guides the patient to success with adherence strategies.

EXPERT OPINION

Knowledge of the side effects correlated with PEG-IFN is very relevant for clinicians because it can allow them to arrange the best methods for treating these effects and avoid the discontinuation of antiviral treatment. Moreover, the use of new antiviral drugs will considerably shorten treatment periods reducing many of the above-described side effects and, thus, increase adherence to scheduled therapy.

Ribavirin-induced anemia in hepatitis C virus patients undergoing combination therapy

The current standard of care for hepatitis C virus (HCV) infection – combination therapy with pegylated interferon and ribavirin – elicits sustained responses in only ∼50% of the patients treated. No alternatives exist for patients who do not respond to combination therapy. Addition of ribavirin substantially improves response rates to interferon and lowers relapse rates following the cessation of therapy, suggesting that increasing ribavirin exposure may further improve treatment response. A key limitation, however, is the toxic side-effect of ribavirin, hemolytic anemia, which often necessitates a reduction of ribavirin dosage and compromises treatment response. Maximizing treatment response thus requires striking a balance between the antiviral and hemolytic activities of ribavirin. Current models of viral kinetics describe the enhancement of treatment response due to ribavirin. Ribavirin-induced anemia, however, remains poorly understood and precludes rational optimization of combination therapy. Here, we develop a new mathematical model of the population dynamics of erythrocytes that quantitatively describes ribavirin-induced anemia in HCV patients. Based on the assumption that ribavirin accumulation decreases erythrocyte lifespan in a dose-dependent manner, model predictions capture several independent experimental observations of the accumulation of ribavirin in erythrocytes and the resulting decline of hemoglobin in HCV patients undergoing combination therapy, estimate the reduced erythrocyte lifespan during therapy, and describe inter-patient variations in the severity of ribavirin-induced anemia. Further, model predictions estimate the threshold ribavirin exposure beyond which anemia becomes intolerable and suggest guidelines for the usage of growth hormones, such as erythropoietin, that stimulate erythrocyte production and avert the reduction of ribavirin dosage, thereby improving treatment response. Our model thus facilitates, in conjunction with models of viral kinetics, the rational identification of treatment protocols that maximize treatment response while curtailing side effects.

The treatment of HCV infection poses a major global health-care challenge today. The current standard of care, combination therapy with interferon and ribavirin, works in only about half of the patients treated. Because no alternatives are available yet for patients in whom combination therapy fails, identifying ways to improve response to combination therapy is critical. Increasing exposure to ribavirin does improve response but is associated with the severe side-effect, anemia. One way to maximize treatment response therefore is to increase ribavirin exposure to levels just below where anemia becomes intolerable. A second way is to supplement combination therapy with growth hormones, such as erythropoietin, that increase the production of red blood cells (erythrocytes) and compensate for ribavirin-induced anemia. Rational optimization of combination therapy thus relies on a quantitative description of ribavirin-induced anemia, which is currently lacking. Here, we develop a model of the population dynamics of erythrocytes in individuals exposed to ribavirin that quantitatively describes ribavirin-induced anemia. Model predictions capture several independent observations of ribavirin-induced anemia in HCV patients undergoing combination therapy, estimate the threshold ribavirin exposure beyond which anemia becomes intolerable, suggest guidelines for the usage of growth hormones, and facilitate rational optimization of therapy.

HIV infection and the liver: the importance of HCV-HIV coinfection and drug-induced liver injury

Hepatitis C virus-Human immunodeficiency virus (HCV-HIV) coinfections are identified in up to 30% of patients infected with HIV and in 8% of patients infected with HCV. Now that progression of HIV and deaths due to AIDS can be prevented by highly active antiretroviral therapy (HAART), it is clear that HCV coinfection is associated with accelerated progression to cirrhosis and increased liver-related morbidity and mortality. Antiviral therapy with pegylated interferon and ribavirin for HCV in HCV-HIV coinfected patients is less successful than in patients with HCV monoinfection, and HAART can cause drug-induced liver injury. Multiple barriers limit the number of HCV-HIV coinfected patients who receive antiviral therapy for HCV, and the role of orthotopic liver transplantation (OLT) in HIV monoinfected and HCV-HIV coinfected patients remains controversial. Clinical trials of HCV-specific protease or polymerase inhibitors combined with pegylated interferon and ribavirin are needed urgently in coinfected patients, both before and after OLT.

Influence of ITPA polymorphisms on decreases of hemoglobin during treatment with pegylated interferon, ribavirin, and telaprevir

Polymorphisms of the inosine triphosphatase (ITPA) gene influence anemia during pegylated interferon (PEG-IFN) and ribavirin (RBV) therapy, but their effects during triple therapy with PEG-IFN, RBV, and telaprevir are not known. Triple therapy for 12 weeks, followed by PEG-IFN and RBV for 12 weeks, was given to 49 patients with RBV-sensitive (CC at rs1127354) and 12 with RBV-resistant (CA/AA) ITPA genotypes who had been infected with hepatitis C virus (HCV) of genotype 1. Decreases in hemoglobin levels were greater in patients with CC than CA/AA genotypes at week 2 (-1.63 ± 0.92 vs. -0.48 ± 0.75 g/dL, P = 0.001) and week 4 (-3.5 ± 1.1 vs. -2.2 ± 0.96, P = 0.001), as well as at the end of treatment (-2.9 ± 1.1 vs. -2.0 ± 0.86, P = 0.013). Risk factors for hemoglobin <11.0 g/dL at week 4 were female gender, age >50 years, body mass index (BMI) <23, and CC at rs1127354 by multivariate analysis. RBV dose during the first 12 weeks was smaller in patients with CC than CA/AA genotypes (52 ± 14% vs. 65 ± 21% of the target dose, P = 0.039), but the total RBV dose was no different between them (49 ± 17% and 54 ± 18% of the target, P = 0.531). Sustained virological response (SVR) was achieved in 70% and 64% of them, respectively (P = 0.724).

CONCLUSION

ITPA polymorphism influences hemoglobin levels during triple therapy, particularly during the first 12 weeks while telaprevir is given. With careful monitoring of anemia and prompt adjustment of RBV dose, SVR can be achieved comparably frequently between patients with CC and CA/AA genotypes.

Taribavirin: potential future in the treatment of hepatitis C

Taribavirin is a prodrug of ribavirin, studied as a treatment modality in combination with PEGylated interferon for chronic hepatitis C. Taribavirin is catalyzed to ribavirin by adenosine deaminase, which is ubiquitous within the body. Taribavirin has resulted in significantly lower rates of anemia, the main complication of ribavirin and cause of dose reductions or discontinuation. Previous clinical studies failed to demonstrate noninferiority to ribavirin. However, better results were observed when taribavirin was given as a weight-based medicine, as shown in a recently published Phase IIb study.

Impact of pentoxifylline and vitamin e on ribavirin-induced haemolytic anaemia in chronic hepatitis C patients: an egyptian survey

Background/Aim. We evaluate the impact of combined pentoxifylline and high-dose vitamins E to standard antiviral treatment on RBV-induced haemolytic anaemia. Patients and Methods. Selected 200 naïve chronic HCV patients, were randomized to receive either the standard antiviral therapy (peginterferon α-2b and RBV) plus pentoxifylline (800 mg) and high-dose vitamin E (1000 iu) daily (combined group) or received standard antiviral therapy plus placebo only (control group). They were followed up during treatment course and for 6 months posttreatment to assess the occurrence of anaemia and virological response, respectively. Results. RBV dose modification due to anaemia were significantly less in combined group (8.5 versus 21.5%. P < .05).Withdrawal, secondary to sever anemia (Hb < 8.5 gm%), was recorded only in 6 (28.6%) patients of the control group. Both (ETR) and (SVR) were significantly higher in combined group than control group by both intention-to-treat analysis (71 versus 56%, P < .05 and 66 versus 49%, P < .05) and per-protocol analysis (85.5 versus 70.9%, P < .05 and 79.5 versus 62%, P < .05). Conclusion. Pentoxifylline and vitamin E can ameliorate RBV-associated haemolysis; improve compliance and virologic clearance when combined with the standard antiviral therapy in patients with chronic hepatitis C.

Management of Hepatitis C Antiviral Therapy Adverse Effects

Hepatitis C is one of the leading causes of liver disease in the United States, affecting more than 4 million individuals. The current treatment regimen involves pegylated interferon in combination with ribavirin. Although antiviral treatment has been associated with a greater than 50% sustained viral response rate, the adverse effects have proven to be detrimental to quality of life and therapy adherence, and consequently lead to lower sustained viral response rates. This article identifies the most frequently described complications associated with pegylated interferon and ribavirin. The active management of these complications is discussed, including both preventive and empiric treatments.

Optimal erythrocyte ribavirin level to reduce the risk of anemia and obtain an early virological response in patients with chronic hepatitis C caused by genotype 1b infection

Aims. To determine whether the erythrocyte phosphorylated ribavirin (RBV) level might be a useful index of EVR and risk of anemia and to determine the optimal dose of RBV in 24 patients with hepatitis C with pegylated interferon and RBV. Methodology. The RBV level was measured by a high-performance liquid chromatography. Results and Conclusion. In patients aged 50 years or over, a negative correlation (r = -0.548, P < .05) was observed between the RBV level at week 2 and rate of Hb reduction (ΔHb) at week 4. The ΔHb at week 4 was significantly greater in patients with RBV levels of ≥800 μM (-25.5 ± 10.1%) than in patients with RBV levels <800 μM (-15.6 ± 7.7%). None of the patients with RBV levels <600 μM at week 2 achieved EVR and SVR. Thus the optimal levels of erythrocyte phosphorylated RBV at week 2 of therapy in order to achieve EVR without anemia seemed to be 600-800 μM.

Ribavirin monitoring in chronic hepatitis C therapy: anaemia versus efficacy

The standard treatment of HCV infection with pegylated interferon-alpha2a or -alpha2b and ribavirin is effective in <50% of HCV genotype-1-infected patients. To improve this figure, it might be desirable to obtain optimal plasma concentrations of the drug by increasing the dose. Unfortunately, there is great interpatient variability in ribavirin pharmacokinetics. In the present review, we describe the mechanism of ribavirin-induced anaemia in detail, evaluate host predictive factors for this harmful side effect and assess the literature data on attempts to improve the sustained virological response rate by increasing the dose of ribavirin. We suggest an optimal steady-state concentration range for ribavirin in monoinfected and coinfected patients. Lastly, we propose that it would be of particular value to monitor ribavirin concentrations in HCV genotype-1-infected patients and (regardless of the genotype) coinfected patients, haemodialyzed patients and obese patients.

Hepatitis C virus treatment-related anemia is associated with higher sustained virologic response rate

BACKGROUND & AIMS

Hepatitis C virus (HCV) treatment is frequently complicated by anemia from ribavirin (RBV)-related hemolysis and peginterferon-alfa (PEG-IFN)-related bone marrow suppression. We investigated the relationships among treatment outcomes, anemia, and their management with RBV dose reduction and/or erythropoiesis-stimulating agents (ESAs).

METHODS

We analyzed data from a trial conducted at 118 United States academic and community centers in treatment-naïve patients with HCV genotype 1. Patients were treated for as many as 48 weeks with 1 of 3 PEG-IFN/RBV regimens. ESAs were permitted for anemic patients (hemoglobin [Hb] <10 g/dL) after RBV dose reduction. Sustained virologic responses (SVR) were assessed based on decreases in Hb, anemia, and ESA use.

RESULTS

While patients received treatment, 3023 had their Hb levels measured at least once. An SVR was associated with the magnitude of Hb decrease: >3 g/dL, 43.7%; ≤3 g/dL, 29.9% (P < .001). Anemia occurred in 865 patients (28.6%); 449 of these (51.9%) used ESAs. In patients with early-onset anemia (≤ 8 weeks of treatment), ESAs were associated with higher SVR rate (45.0% vs 25.9%; P < .001) and reduced discontinuation of treatment because of adverse events (12.6% vs 30.1%, P < .001). ESAs did not affect SVR or discontinuation rates among patients with late-stage anemia.

CONCLUSIONS

Among HCV genotype 1-infected patients treated with PEG-IFN/RBV, anemia was associated with higher rates of SVR. The effect of ESAs varied by time to anemia; patients with early-onset anemia had higher rates of SVR with ESA use, whereas no effect was observed in those with late-onset anemia. Prospective trials are needed to assess the role of ESAs in HCV treatment.

Plasma/erythrocyte ribavirin x100 ratio as an indicator of sustained virological response in HCV genotype 1 patients with early virological response

BACKGROUND

On-treatment predictors during antiviral therapy of HCV are useful because they allow discontinuation of an unnecessary treatment in non-responders. Our aim was to evaluate the usefulness of plasma and erythrocyte ribavirin levels in predicting sustained virological response (SVR) in HCV genotype 1 patients undergoing antiviral treatment.

METHODS

A total of 40 HCV genotype 1 patients treated with pegylated interferon-alpha2a 180 microg weekly plus ribavirin 1,000 or 1,200 mg daily (according to body weight) were included in the study. Plasma and erythrocyte ribavirin levels were evaluated in all patients at week 12 by HPLC. At week 24, ribavirin levels were reassessed in those achieving early virological response (EVR).

RESULTS

A total of 27 patients achieved EVR, whereas 17 achieved SVR. There was no difference among EVR and non-EVR patients in terms of plasma and erythrocyte ribavirin concentrations at week 12. At week 24, EVR patients obtaining SVR exhibited higher mean +/-sd levels of ribavirin in plasma and lower levels in erythrocytes compared with non-SVR patients (in plasma 12.8 +/-10 versus 5.8 +/-4 microM [P<0.02] and in erythrocytes 1,053 +/-504 versus 1,613 +/-589 microM [P<0.03]). When the plasma ribavirin/erythrocyte ribavirin x100 ratio was compared, the difference was enhanced (1.5 +/-1.3 versus 0.4 +/-0.3 microM; P<0.01). Receiver operating characteristic curve analysis identified a cutoff for plasma ribavirin/erythrocyte ribavirin x100 ratio in predicting SVR of 0.71 with a negative predictive value of 0.8 and a positive predictive value of 0.9, whereas those related to EVR were 1 and 0.6, respectively.

CONCLUSIONS

Plasma ribavirin/erythrocyte ribavirin x100 ratio at week 24 seems to be a good indicator of SVR in HCV genotype 1 patients achieving EVR.

ITPA polymorphism affects ribavirin-induced anemia and outcomes of therapy--a genome-wide study of Japanese HCV virus patients

BACKGROUND & AIMS

Ribavirin-induced anemia is one of the major causes of discontinuation and dose reduction during anti-hepatitis C virus therapy. Factors influencing this anemia, especially host genetic factors, are poorly understood. In this study we investigated predictive factors in hepatitis C virus patients treated with combination therapy.

METHODS

We performed a 2-step genome-wide screening followed by replication analysis and fine-mapping using a total of 923 Japanese hepatitis C virus 1b-infected patients treated with pegylated-interferon plus ribavirin. We also applied logistic regression analysis to search for possible independent associations of clinical parameters and genetic variants with treatment-induced hemoglobin (Hb) decline as well as treatment outcomes.

RESULTS

We identified a variant, located upstream of the inosine triphosphate pyrophosphatase gene on chromosome 20p13 that is significantly associated with treatment-induced anemia (combined P = 6.0 × 10(-14)). Resequencing and fine-mapping revealed several single nucleotide polymorphisms (SNPs) strongly associated with Hb decline, including the nonsynonymous SNP rs1127354 (P = 3.5 × 10(-44)), which was recently reported for other ethnic groups. Another reported SNP, the splicing variant-related SNP rs7270101, was not polymorphic in the Japanese population. Stratified analysis based on rs1127354 genotype revealed that inosine triphosphate pyrophosphatase expression is not correlated with Hb decline, suggesting that rs1127354 is a direct causal variant in the Japanese population. Multivariate analysis demonstrated that age, baseline Hb, baseline platelet count, and rs1127354 were independently associated with severe anemia (Hb <10 g/dL).

CONCLUSIONS

A missense substitution in inosine triphosphate pyrophosphatase gene affects ribavirin-induced anemia in hepatitis C virus-infected Japanese patients.

Variants in the ITPA gene protect against ribavirin-induced hemolytic anemia and decrease the need for ribavirin dose reduction

BACKGROUND & AIMS

In a genome-wide association study of patients being treated for chronic hepatitis C, 2 functional variants in ITPA that cause inosine triphosphatase (ITPase) deficiency were shown to protect against ribavirin (RBV)-induced hemolytic anemia during early stages of treatment. We aimed to replicate this finding in an independent cohort from the Study of Viral Resistance to Antiviral Therapy of Chronic Hepatitis C and to investigate the effects of these variants beyond week 4.

METHODS

Genetic material was available from 318 patients. The ITPA variants, rs1127354 (exon 2, P32T) and rs7270101 (intron 2, splice altering), were genotyped and tested for association with hemoglobin (Hb) reduction at week 4. An ITPase deficiency variable was defined that combined both ITPA variants according to documented effect on ITPase activity. We investigated the impact of ITPA variants on Hb levels over the course of therapy and on the need for RBV dose reduction.

RESULTS

The final analysis included 304 patients with genotype 1 hepatitis C virus (167 white patients and 137 black patients). The polymorphisms rs1127354 and rs7270101 were associated with Hb reduction at week 4 (P = 3.1 × 10(-13) and 1.3 × 10(-3), respectively). The minor alleles of each variant protected against Hb reduction. Combining the variants into the ITPase deficiency variable strengthened the association (P = 2.4 × 10(-18)). The ITPase deficiency variable was associated with lower rates of anemia over the entire treatment period (48 weeks), as well as a lower rate of anemia-related RBV dose reduction (hazard ratio, 0.52; P = .0037). No association with sustained virological response was observed.

CONCLUSIONS

Two polymorphisms that cause ITPase deficiency are strongly associated with protection from RBV-induced hemolytic anemia and decrease the need for RBV dose reduction.

Virologic response rates of weight-based taribavirin versus ribavirin in treatment-naive patients with genotype 1 chronic hepatitis C

Ribavirin-induced hemolytic anemia can prompt dose reductions and lower sustained virologic response (SVR) rates in the treatment of patients with chronic hepatitis C. The study aimed to determine if weight-based dosing of taribavirin (TBV), an oral prodrug of ribavirin (RBV), demonstrated efficacy comparable to RBV while maintaining its previously demonstrated anemia advantage with fixed dose administration. A U.S. phase 2b randomized, open-label, active-controlled, parallel-group study was conducted in 278 treatment-naive patients infected with genotype 1 who were stratified by body weight and baseline viral load. Patients were randomized 1:1:1:1 to receive TBV (20, 25, or 30 mg/kg/day) or RBV (800-1400 mg/day) with pegylated interferon alfa-2b for 48 weeks. The SVR rates in this difficult-to-cure patient demographics (mean age, 49 years; 61% male; 30% African American or Latino; high viral load; advanced fibrosis; and mean weight, 82 kg) were 28.4%, 24.3%, 20.6%, and 21.4% in the 20, 25, and 30 mg/kg TBV groups and the RBV group, respectively. There were no statistical differences in the efficacy analyses. Anemia rates were significantly lower (P < 0.05) in the 20 and 25 mg/kg/day TBV treatment groups (13.4% and 15.7%, respectively) compared to RBV (32.9%). The most common adverse events in all groups were fatigue, diarrhea, and insomnia. Diarrhea, reported in 38% of TBV patients versus 21% of RBV patients, was generally mild and not dose-limiting.

CONCLUSION

All TBV doses demonstrated efficacy and tolerability comparable to that of RBV; however, the 25 mg/kg dose demonstrated the optimal balance of safety and efficacy. Anemia rates were significantly lower for TBV given at 20-25 mg/kg than RBV. These data suggest weight-based dosing with TBV provides a safe and effective treatment alternative to RBV for chronic hepatitis C. American Association for the Study of Liver Diseases.

N-(3-Cyanophenyl)-2-phenylacetamide, an effective inhibitor of morbillivirus-induced membrane fusion with low cytotoxicity

Based on the structural similarity of viral fusion proteins within the family Paramyxoviridae, we tested recently described and newly synthesized acetanilide derivatives for their capacity to inhibit measles virus (MV)-, canine distemper virus (CDV)- and Nipah virus (NiV)-induced membrane fusion. We found that N-(3-cyanophenyl)-2-phenylacetamide (compound 1) has a high capacity to inhibit MV- and CDV-induced (IC(50) μM), but not NiV-induced, membrane fusion. This compound is of outstanding interest because it can be easily synthesized and its cytotoxicity is low [50 % cytotoxic concentration (CC(50)) ≥ 300 μM], leading to a CC(50)/IC(50) ratio of approximately 100. In addition, primary human peripheral blood lymphocytes and primary dog brain cell cultures (DBC) also tolerate high concentrations of compound 1. Infection of human PBMC with recombinant wild-type MV is inhibited by an IC(50) of approximately 20 μM. The cell-to-cell spread of recombinant wild-type CDV in persistently infected DBC can be nearly completely inhibited by compound 1 at 50 μM, indicating that the virus spread between brain cells is dependent on the activity of the viral fusion protein. Our findings demonstrate that this compound is a most applicable inhibitor of morbillivirus-induced membrane fusion in tissue culture experiments including highly sensitive primary cells.

Epoetin alpha improves the response to antiviral treatment in HCV-related chronic hepatitis

BACKGROUND

The conventional antiviral treatment of chronic hepatitis related to hepatitis C virus (HCV) often leads to anemia. In this case, it is necessary to reduce ribavirin dose or stop treatment, thus reducing the rate of sustained virological response.

AIM

We investigated whether epoetin alpha administration improves treatment adherence and leads to higher percentage of response at the end of therapy and sustained virological response.

METHODS

Two hundred and fourteen individuals with genotype 1b HCV-related chronic hepatitis underwent treatment with pegylated (peg)-interferon alpha-2A 180 μg once weekly and ribavirin 1,000-1,200 mg/day; 174 were responders. Forty individuals completed treatment with no hemoglobin reduction; 134 developed anemia during therapy. Anemic responders were distributed randomly into two groups: group 1 continued therapy with epoetin alpha addiction; group 2 continued antiviral therapy with ribavirin reduction only.

RESULTS

Patients in group 1 achieved better control of hemoglobin levels (13.8 ± 1.2 g/dl at the end of therapy) than those in group 2 (11.5 ± 0.8 g/dl). Sustained virological response was 59.7% in group 1 compared with 34.4% in group 2 (p<0.01).

CONCLUSIONS

In patients with 1b HCV-related chronic hepatitis who develop anemia during antiviral treatment, administration of epoetin alpha increases hemoglobin levels and the end-of-treatment rate and sustains virological response by improving treatment adherence.

Adverse effects of drugs in the treatment of viral hepatitis

The hepatitis B virus (HBV) and the hepatitis C virus (HCV) affect approximately 400-500 million individuals worldwide. Both infections are characterised by a significant morbidity and mortality: chronic hepatitis B and C may evolve towards the development of cirrhosis and primary hepatocellular carcinoma. During the last two decades, several new antivirals have been developed that are active against HBV and HCV, allowing sustained cure rates in a significant proportion of patients. All these drugs have side effects, which may represent a major barrier to achieve cure in many patients in need. I will review the most common adverse events reported during the therapy of chronic hepatitis B and C, with some recommendations for proper management.

Preemptive erythropoietin plus high ribavirin doses to increase rapid virological responses in HIV patients treated for chronic hepatitis C

Chronic hepatitis C affects one-third of HIV(+) patients worldwide. High ribavirin (RBV) exposure is crucial to maximize the response to hepatitis C therapy in this population, although it may increase the risk for hemolytic anemia. PERICO is a prospective multicenter trial in which HIV/HCV-coinfected patients are randomized to receive peginterferon (pegIFN) alfa-2a 180 microg/week plus either weight-based RBV (1000-1200 mg/day) or RBV 2000 mg/day, the latest along with erythropoietin alfa (EPO) 30,000 IU/week from the first day until week 4. A total of 149 patients were assessed in a planned interim analysis at week 4. In both arms, 22% of patients achieved negative HCV-RNA (rapid virological response, RVR). Multivariate analysis [OR (IC 95%), p] showed that factors associated with RVR were HCV genotypes 2/3 vs. 1/4 [20 (5-100), <0.01] and baseline HCV-RNA [0.16 (0.07-0.37) per log IU/ml, <0.01]. The occurrence of severe anemia (hemoglobin <10 g/dl) did not differ when comparing RBV vs. high RBV + EPO (7% vs. 3%; p = 0.4). Moreover, RBV plasma trough levels were comparable at week 4 (1.9 vs. 2.4 microg/ml; p = 0.2). Use of high RBV doses with preemptive EPO during the first 4 weeks of hepatitis C therapy is safe, but fails to enhance significantly RBV plasma exposure and RVR rates. Extensive intraerythrocyte accumulation of RBV following boosted production of red blood cells by EPO could explain these findings.

Efficacy and safety of pegylated IFN alfa 2b alone or in combination with ribavirin in thalassemia major with chronic hepatitis C

BACKGROUND

Treatment of HCV infection in patients with thalassemia major (TM) is limited by the lack of large clinical trials and concerns about ribavirin-induced hemolysis.

METHODS

We conducted a prospective, randomized, open-label study to determine efficacy and tolerability of pegylated-interferon alfa 2b (1.5 microg/kg/week) alone (group A) or with ribavirin (12-15 mg/kg/day; group B) in patients with TM and chronic HCV infection. Patients with genotype 1 or 4 HCV were treated for 48 weeks and those with genotype 3 or 2 HCV for 24 weeks. Early viral response (EVR; after 12 weeks of treatment), end-of-treatment virological response (ETR) and sustained virological response (SVR; 6 months after stopping therapy) were assessed.

RESULTS

Of 40 patients, 20 each were allocated to the two treatment groups. EVR rates in group A and B were 15 (75%) and 18 (90%), respectively. ETR occurred in 17/20 (85%) patients in each group. SVR occurred in 8 (40%) patients in group A and 14 (70%) in group B. Blood transfusion requirements increased in one patient in group A and four patients in group B. One patient in group A had severe sepsis and one in group B had nephrotic syndrome. Two patients in each group required reduction in drug dose.

CONCLUSIONS

In patients with TM and chronic HCV infection, pegylated interferon alfa 2b and ribavirin combination therapy achieves a higher SVR rate than pegylated interferon alone, and is well tolerated except for an increase in blood transfusion requirement.

Use of epoetin beta during combination therapy of infection with hepatitis c virus with ribavirin improves a sustained viral response

The aim of the study was to evaluate the effects of epoetin-beta on anemia and sustained viral response in patients with chronic hepatitis C receiving treatment with pegylated interferon and ribavirin. Forty-two Caucasian patients with chronic hepatitis C infection, treated with pegylated interferon alpha-2a or alpha-2b plus ribavirin, who experienced at least a 2 log decline in HCV-RNA in the first month of therapy and a > or =2.5 g/dl hemoglobin drop from baseline, were recruited. They were divided into two groups: 22 patients received epoetin-beta 30,000 U administered s.c. q.w. (group A) and 20 patients received a reduced ribavirin dose of 600 mg daily (group B). The end-of-treatment response was 95.4% (21/22) in group A and 80% (16/20) (P = 0.2) in group B. Sustained viral response in group A was 81.8% (18/22), statistically higher than in group B (45%, 9/20) (P = 0.03). Mean corpuscular volume of erythrocytes was statistically lower in group A than in group B 4 weeks after starting epoetin-beta or reduced ribavirin dose (P < 0.001), end-of-treatment (P < 0.001) and after 6 months follow-up (P < 0.001). A negative correlation between the levels of ferritin serum was found in group A at the baseline and mean corpuscular volume value after 1 month of combination antiviral therapy (r = -0.45; P = 0.35), 4 weeks after starting epoetin-beta (r = -0.43; P = 0.04) and after 6 months follow-up (r = -0.45; P = 0.03). Administration of epoetin-beta increases sustained viral response rates among patients developing anemia, because the standard dose of ribavirin is maintained, thereby reducing the side-effects of antiviral treatment.

Ribavirin plus interferon versus interferon for chronic hepatitis C

BACKGROUND

Hepatitis C is a major cause of liver-related morbidity and mortality. Standard therapy is ribavirin plus pegylated interferon to achieve undetectable level of virus in the blood, but the effect on clinical outcomes is controversial.

OBJECTIVES

To assess the beneficial and harmful effects of ribavirin and interferon combination therapy versus interferon monotherapy for chronic hepatitis C.

SEARCH STRATEGY

We identified trials through electronic databases, manual searches of bibliographies and journals, approaching authors of trials, and pharmaceutical companies until March 2009.

SELECTION CRITERIA

We included randomised trials, irrespective of blinding, language, or publication status, comparing ribavirin plus interferon versus interferon for treatment of chronic hepatitis C.

DATA COLLECTION AND ANALYSIS

The primary outcome measures were serum sustained loss of hepatitis C virus, liver-related morbidity plus all-cause mortality, and adverse events. We performed subgroup analyses of patients who were naive, relapsers, or non-responders to previous antiviral treatment. All outcomes were analysed with the random-effects model. We used Peto odds ratios (OR) with 95% confidence intervals (CI) for analysis of morbidity plus mortality. The remaining outcomes were presented as relative risks (RR). We used trial sequential analyses to examine the robustness of our findings.

MAIN RESULTS

We included 83 randomised trials with 12,707 patients. Most trials had unclear or high risk of bias. We did not find any significant influence of bias on our results but cannot exclude outcome measure reporting bias as many trials did not report on the primary outcomes of this review. Compared with interferon, ribavirin plus interferon had a significant beneficial effect on sustained virological response in subgroups of naive patients (RR 0.72, 95% confidence interval (CI) 0.68 to 0.75), relapsers (RR 0.62, 95% CI 0.54 to 0.70), non-responders (RR 0.89, 95% CI 0.84 to 0.93), and in all patients (RR 0.75, 95% CI 0.71 to 0.79). Combination therapy significantly reduced morbidity plus mortality in all patients (Peto OR, 0.43, 95% CI 0.23 to 0.79), but not in naive, relapsers, or non-responders individually. Combination therapy significantly increased the risk of haematological, dermatological, gastrointestinal, infectious, and miscellaneous (cough, dyspnoea, fatigue) adverse reactions. Accordingly, combination therapy significantly increased the risk of treatment discontinuation and dose reductions. Trial sequential analyses confirmed our findings regarding virological effects, but not regarding liver-related morbidity and all-cause mortality.

AUTHORS' CONCLUSIONS

Compared with interferon alone, ribavirin plus interferon is more effective in clearing hepatitis C virus from the blood. Combination therapy may reduce liver-related morbidity and all-cause mortality, but we need more evidence. The number needed to treat to obtain a beneficial effect is considerable considering the increased risk of several severe adverse reactions and costs.

The utility of therapeutic drug monitoring for ribavirin in patients with chronic hepatitis C--a critical review

OBJECTIVE

To evaluate the utility of therapeutic drug monitoring (TDM) for ribavirin in chronic hepatitis C.

DATA SOURCES

Literature searches were conducted through PubMed (1949-June 2009), EMBASE (1980-June 2009), BIOSIS Previews (1969-June 2009), International Pharmaceutical Abstracts (1970-June 2009), Google, and www.clinicaltrials.gov using the terms ribavirin, therapeutic monitoring, hepatitis C, and drug levels. In addition, pertinent reference citations from identified publications were reviewed. Studies were limited to English language, adult age, and human subjects.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated. Studies that measured ribavirin concentrations or dose and treatment response were included in the review.

DATA SYNTHESIS

While monitoring of ribavirin plasma concentrations to improve treatment response in patients with chronic hepatitis C has been described in the literature, the utility of TDM for ribavirin in this group of patients has not been systematically studied. Thus, a previously published 9-step decision-making algorithm was employed to help determine whether TDM is warranted, based on currently available evidence. Thirty articles involving patients with chronic hepatitis C mono-infection, 12 for hepatitis C-HIV coinfection, 5 for renal dysfunction, and 5 for post-liver transplant patients were reviewed. In all subpopulations, studies exist that either support or refute the usefulness of ribavirin TDM. Additionally, the majority of the included studies had methodologic limitations, such as small sample size, retrospective analyses, and lack of p value adjustment for multiple analyses. Large randomized controlled trials would help to definitively answer this question.

CONCLUSIONS

There is conflicting evidence about the existence of a correlation between ribavirin concentrations and virologic response or development of toxicity. This inconsistent evidence, coupled with the currently employed effective strategies that maximize sustained virologic response and minimize development of anemia, precludes the utility of TDM for ribavirin.

Antiviral activity of gliotoxin, gentian violet and brilliant green against Nipah and Hendra virus in vitro

Background

Using a recently described monolayer assay amenable to high throughput screening format for the identification of potential Nipah virus and Hendra virus antivirals, we have partially screened a low molecular weight compound library (>8,000 compounds) directly against live virus infection and identified twenty eight promising lead molecules. Initial single blind screens were conducted with 10 μM compound in triplicate with a minimum efficacy of 90% required for lead selection. Lead compounds were then further characterised to determine the median efficacy (IC₅₀), cytotoxicity (CC₅₀) and the in vitro therapeutic index in live virus and pseudotype assay formats.

Results

While a number of leads were identified, the current work describes three commercially available compounds: brilliant green, gentian violet and gliotoxin, identified as having potent antiviral activity against Nipah and Hendra virus. Similar efficacy was observed against pseudotyped Nipah and Hendra virus, vesicular stomatitis virus and human parainfluenza virus type 3 while only gliotoxin inhibited an influenza A virus suggesting a non-specific, broad spectrum activity for this compound.

Conclusion

All three of these compounds have been used previously for various aspects of anti-bacterial and anti-fungal therapy and the current results suggest that while unsuitable for internal administration, they may be amenable to topical antiviral applications, or as disinfectants and provide excellent positive controls for future studies.

Ribavirin monotherapy for chronic hepatitis C

BACKGROUND

Hepatitis C is a major cause of liver-related morbidity and mortality. A high proportion of patients never experience symptoms. Peginterferon plus ribavirin is the recommended treatment for chronic hepatitis C. However, ribavirin monotherapy may be considered for some patients.

OBJECTIVES

To assess the beneficial and harmful effects of ribavirin monotherapy for patients with chronic hepatitis C.

SEARCH STRATEGY

We identified trials through electronic databases, manual searches of bibliographies and journals, authors of trials, and pharmaceutical companies until March 2009.

SELECTION CRITERIA

We included all randomised trials irrespective of blinding, language, or publication status comparing ribavirin versus no intervention, placebo, or interferon for chronic hepatitis C.

DATA COLLECTION AND ANALYSIS

The primary outcome measures were serum sustained virological response (loss of hepatitis C virus RNA at least six months after treatment), liver-related morbidity plus all-cause mortality, and adverse events. Secondary outcome measures were end of treatment virological response, biochemical response (transaminase activity), and histological response. Randomisation methods, blinding, data handling, and funding were extracted as measures of bias control. Random-effects and fixed-effect meta-analyses were performed for all outcomes. We only present the results of the fixed-effect model if both models provide the same result regarding statistical significance. We present data as risk difference (RD) with 95% confidence intervals (CI).

MAIN RESULTS

We included 14 randomised trials with 657 patients. The majority of trials had unclear control of bias. Compared with placebo or no intervention, ribavirin had no significant effect on the sustained virological response (RD 0%, 95% CI -2% to 3%, five trials) or end of treatment virological response (RD 0% 95% CI -3% to 3%, ten trials). Ribavirin had no significant effect on liver-related morbidity plus mortality (RD 0%, 95% CI -2% to 3%, 11 trials). Ribavirin significantly increased the risk of adverse reactions, including anaemia. Ribavirin significantly improved end of treatment biochemical and histological response but not the sustained biochemical response. Ribavirin was significantly inferior to interferon regarding virological and biochemical responses (five trials).

AUTHORS' CONCLUSIONS

Ribavirin seems without beneficial effects on serum virological response and liver-related morbidity or mortality, and significantly increased the risk of adverse reactions. Ribavirin monotherapy seems significantly inferior to interferon monotherapy. The total number of included patients is small, and more trials are perhaps needed. The use of ribavirin monotherapy for chronic hepatitis C cannot be recommended outside randomised trials.

Mathematical modeling of HCV infection and treatment

In the last decade, viral kinetic modeling has played an important role in the analysis of HCV RNA decay after the initiation of antiviral therapy. Models have provided a means of evaluating the antiviral effectiveness of therapy and of estimating parameters, such as the rate of virion clearance and the rate of loss of HCV-infected cells, and they have suggested mechanisms of action for both interferon-alpha and ribavirin. The inclusion of homeostatic proliferation of infected and uninfected hepatocytes in existing viral kinetic models has allowed prediction of most observed HCV RNA profiles under treatment, for example, biphasic and triphasic viral decay and viral rebound to baseline values after the cessation of therapy. In addition, new kinetic models have taken into consideration the different pharmacokinetics of standard and pegylated forms of interferon and have incorporated alanine aminotransferase kinetics and aspects of immune responses to provide a more comprehensive picture of the biology underlying changes in HCV RNA during therapy. Here, we describe our current understanding of the kinetics of HCV infection and treatment.

Ribavirin analogs

Ribavirin is ineffective against hepatitis C virus as mono-therapy but is critical in attaining both early virologic response and sustained virologic response when combined with pegylated interferon. Ribavirin has significant dose-limiting toxicities, the most important of which is hemolytic anemia. Taribavirin is a ribavirin pro-drug, which targets the liver and has less incidence of anemia, and it may be a promising alternative to ribavirin in the future.

Treatment of chronic hepatitis C in sickle cell disease and thalassaemic patients with interferon and ribavirin

BACKGROUND/AIM

Hepatic complications are a major cause of death in patients with congenital anaemia and chronic hepatitis C. Ribavirin is usually contraindicated in patients with haemolytic anaemia. This pilot study evaluated the efficacy and safety of antiviral treatment in patients with sickle cell disease (SCD) or beta-thalassaemia major (TM).

METHODS

Eleven consecutive SCD and TM patients were included. Interferon monotherapy was administrated in the two first thalassaemic patients. Other patients received combination therapy with full dose of pegylated interferon 2b and increasing doses of ribavirin, starting with a low dose of ribavirin (400 mg/day).

RESULTS

Hepatitis C virus genotypes were 1 or 4 in nine cases. A sustained virological response achieved in five of 11 patients despite unfavourable factors to response (genotypes, nonresponders to an earlier treatment). Haemoglobin level at the end of treatment was higher than baseline levels in five of six SCD patients. No SCD patient needed a transfusion during and after treatment period, neither presented vasoocclusive crisis. The mean increase in transfusion requirements was 32.5% in the thalassaemic group.

CONCLUSION

A sustained virological response can be obtained in SCD and TM patients. No earlier study of excellent haematological tolerance among SCD patients under ribavirin has been reported to date. The results of this study suggest that full dose ribavirin could be used from the start of treatment in SCD patients.

Proanthocyanidin from blueberry leaves suppresses expression of subgenomic hepatitis C virus RNA

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. While searching for new natural anti-HCV agents in agricultural products, we found a potent inhibitor of HCV RNA expression in extracts of blueberry leaves when examined in an HCV subgenomic replicon cell culture system. This activity was observed in a methanol extract fraction of blueberry leaves and was purified by repeated fractionations in reversed-phase high-performance liquid chromatography. The final purified fraction showed a 63-fold increase in specific activity compared with the initial methanol extracts and was composed only of carbon, hydrogen, and oxygen. Liquid chromatography/mass-ion trap-time of flight analysis and butanol-HCl hydrolysis analysis of the purified fraction revealed that the blueberry leaf-derived inhibitor was proanthocyanidin. Furthermore, structural analysis using acid thiolysis indicated that the mean degree of polymerization of the purified proanthocyanidin was 7.7, consisting predominantly of epicatechin. Proanthocyanidin with a polymerization degree of 8 to 9 showed the greatest potency at inhibiting the expression of subgenomic HCV RNA. Purified proanthocyanidin showed dose-dependent inhibition of expression of the neomycin-resistant gene and the NS-3 protein gene in the HCV subgenome in replicon cells. While characterizing the mechanism by which proanthocyanidin inhibited HCV subgenome expression, we found that heterogeneous nuclear ribonucleoprotein A2/B1 showed affinity to blueberry leaf-derived proanthocyanidin and was indispensable for HCV subgenome expression in replicon cells. These data suggest that proanthocyanidin isolated from blueberry leaves may have potential usefulness as an anti-HCV compound by inhibiting viral replication.

Low dose erythropoietin-beta improves anemia and maintains ribavirin dose in chronic hepatitis C patients receiving combination therapy with ribavirin plus pegylated interferon Alfa-2b

AIM

Anemia during combination therapy with pegylated interferon alfa-2b plus ribavirin (RBV) for chronic hepatitis C virus (HCV) patients usually leads to RBV dose reduction or discontinuation. This study evaluated the effect of erythropoietin-beta (EPO-beta) to maintain RBV dose and hemoglobin (Hb) level in chronic HCV patients treated with antiviral combination therapy.

METHODS

Eighty-eight chronic HCV patients who developed anemia during therapy were enrolled into this retrospective study: 55 in the EPO-beta group and 33 in the untreated group. The study endpoints were to assess the RBV maintenance and the changes in Hb.

RESULTS

A higher percentage of patients with RBV maintenance was observed in the EPO-beta group compared with the untreated group (nadir Hb level <10.5 g/dL; 70% vs. 38%, P = 0.020; nadir Hb < 10 g/dL; 62% vs. 27%, P = 0.046). The mean Hb change from week 12 to week 20 was higher in the EPO-beta group when compared with the untreated group, especially for patients receiving a total EPO-beta dose of more than 16 000 U (+0.70 g/dL vs. -0.32 g/dL, P = 0.023) and of 10 000 U-14 000 U (+0.60 g/dL vs. -0.32 g/dL, P = 0.023).

CONCLUSIONS

Low-dose EPO-beta can maintain RBV dose and increase Hb levels in anemic chronic HCV patients receiving combination therapy.

Ribavirin: current role in the optimal clinical management of chronic hepatitis C

Ribavirin in combination with peginterferon alfa shows strong clinical efficacy against chronic hepatitis C, and is now established as the standard of care. However, the precise role of ribavirin is still being defined, suggesting that optimal ribavirin dose should be maintained over the whole treatment period. Ribavirin dosage varies by bodyweight for genotype 1 disease (1000mg/day in patients <or =75kg and 1200mg/day in patients >75kg), whereas 800mg/day is sufficient to ensure optimal response in all genotype 2/3 patients. Similarly, genotype 1 patients benefit from 48 weeks of therapy, while 24 weeks is sufficient for genotype 2/3 disease. Recent data suggest treatment success is dependent on cumulative ribavirin exposure, as patients who receive <60% of the planned dose have lower response rates, regardless of whether reductions are from temporary interruptions or premature cessation of therapy. All patients should be monitored for hemolytic anemia, as early diagnosis allows management through small dose reductions and stepwise return to the target dose, maximizing cumulative exposure. Despite these recent advances in our knowledge, many questions remain, such as whether the role of ribavirin will change or even be eliminated as new therapies are developed.

Characteristics of Nipah virus and Hendra virus replication in different cell lines and their suitability for antiviral screening

We have recently described the development and validation of a high throughput screening assay suitable for henipavirus antiviral identification. While we are confident this assay is robust and effective, we wished to investigate assay performance in a range of alternative cell lines to determine if assay sensitivity and specificity could be improved. We evaluated ten different cell lines for their susceptibility to Hendra and Nipah virus infection and their sensitivity of detection of the effects of the broad spectrum antiviral, ribavirin and nine novel antivirals identified using our initial screening approach. Cell lines were grouped into three categories with respect to viral replication. Virus replicated best in Vero and BSR cells, followed by Hep-2, HeLa, BHK-21 and M17 cells. The lowest levels of RNA replication and viral protein expression were observed in BAEC, MMEC, A549 and ECV304 cells. Eight cell lines appeared to be similarly effective at discriminating the antiviral effects of ribavirin (<2.7-fold difference). The two cells lines most sensitive to the effect of ribavirin (ECV304 and BAEC) also displayed the lowest levels of viral replication while Vero cells were the least sensitive suggesting excess viral replication may limit drug efficacy and cell lines which limit viral replication may result in enhanced antiviral efficacy. However, there was no consistent trend observed with the other nine antivirals tested. While improvements in antiviral sensitivity in other cell lines may indicate an important role in future HTS assays, the slightly lower sensitivity to antiviral detection in Vero cells has inherent advantages in reducing the number of partially effective lead molecules identified during initial screens. Comparison of a panel of 54 novel antiviral compounds identified during routine screening of an in-house compound library in Vero, BHK-21 and BSR cells suggests no clear advantage of screening in either cell type.

The role of the equilibrative nucleoside transporter 1 (ENT1) in transport and metabolism of ribavirin by human and wild-type or Ent1-/- mouse erythrocytes

The polar nucleoside drug ribavirin is front-line treatment for chronic hepatitis C virus infection. The human equilibrative nucleoside transporter (ENT) 1 transports ribavirin into erythrocytes where it is phosphorylated. These phosphorylated metabolites accumulate in the erythrocytes and produce dose-limiting hemolytic anemia. Here, we examined the in vitro and ex vivo transport and metabolism of ribavirin by erythrocytes isolated from humans and Ent1-null mice. Ribavirin (2.4 microM) uptake was significantly higher (1044 +/- 255 amol/microg/10 s) into erythrocytes from Ent1(+/+) mice compared with that from Ent1(-/-) mice (76.48 +/- 11.20 amol/microg/10 s). Our results showed a saturable (K(m) of 382 +/- 75.1 microM) transport of [(3)H]ribavirin into erythrocytes from Ent1(+/+) mice. We found that ribavirin concentration rapidly (within 60 s) reached equilibrium in erythrocytes using a time course of [(3)H]ribavirin transport (2.5 microM) and metabolism in mouse and human erythrocytes for 8 h. However, total radioactivity of ribavirin was predominantly attributed to the phosphorylated metabolites ribavirin monophosphate and ribavirin triphosphate. Our findings allow us to estimate ribavirin transport, diffusion, and metabolic clearance and to predict in vivo accumulation of ribavirin phosphates in erythrocytes of both mice and humans. Our modeling of ribavirin in erythrocytes on long-term administration of ribavirin suggests that the accumulation of ribavirin inside the cells is dependent on ENT1/Ent1 transport and the rates of intracellular phosphorylation and the degradation of the phosphorylated metabolites. We predict that Ent1(+/+) and Ent1(-/-) mice will serve as excellent models to investigate the contribution of Ent1 to the pharmacokinetics and toxicity of ribavirin in vivo.

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.

Increase in serum bilirubin in HIV/hepatitis-C virus-coinfected patients on atazanavir therapy following initiation of pegylated-interferon and ribavirin

Atazanavir use is associated with increases in serum bilirubin. Ribavirin, used to treat hepatitis-C infection, cause hemolysis and may worsen hyperbilirubinemia. We studied HIV/hepatitis-C virus-coinfected patients who initiated hepatitis-C therapy. Hyperbilirubinemia grade 3-4 increased from 9% to 45% after the start of hepatitis-C treatment in patients who used atazanavir concomitantly. Atazanavir use and hemoglobin (Hb) drops were predictors of increases in bilirubin. A substantial proportion of patients under atazanavir-therapy experienced significant hyperbilirubinemia and jaundice following initiation of hepatitis-C therapy.