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

Variant Inosine Triphosphatase Phenotypes Are Associated With Increased Ribavirin Triphosphate Levels

Individuals with lower inosine triphosphatase (ITPA) enzyme activity have a reduced likelihood of experiencing hemolytic anemia during hepatitis C virus (HCV) treatment containing ribavirin (RBV). Because ITPA degrades purines and RBV is a purine analogue, it is conceivable that ITPA activity may affect intracellular RBV concentrations. Here we assessed the association between ITPA activity phenotype and concentrations of RBV triphosphate (RBV-TP) in red blood cells (RBCs) during HCV treatment. RBV-TP was quantified in the RBCs of 177 HCV-infected individuals at a median (range) of 84 (19 to 336) days into HCV treatment that included RBV. Mean (SD) RBV-TP concentrations were 92.8 (51.6), 101.3 (53.5), 184.8 (84.5), and 197.7 (64.6) pmol/106 cells for 100%, 60%, 30%, and ≤10% ITPA activity groups, respectively. Overall, RBV-TP was approximately 2-fold higher in patients with ≤30% ITPA activity compared to 100% activity (P < .0001). Despite higher RBV-TP levels, individuals with variant ITPA phenotypes had less anemia. The 100% activity group had, on average, a -2.20 g/dL drop in hemoglobin vs -1.43 g/dL (P = .04) for 60% activity, -1.14 g/dL (P = .008) for 30% activity, and -0.70 g/dL (P = .06) for ≤10% activity. This finding of higher RBV-TP concentrations in RBCs in ITPA variants was unexpected given that ITPA activity-deficient individuals have a reduced likelihood of RBV-induced anemia. It also refutes the hypothesis that the mechanism by which ITPA variants are protected against anemia is due to lower RBV-TP levels in RBCs.

Ribavirin Contributes to Hepatitis C Virus Suppression by Augmenting pDC Activation and Type 1 IFN Production

Ribavirin is used as a component of combination therapies for the treatment of chronic hepatitis C virus (HCV) infection together with pegylated interferon and/or direct-acting antiviral drugs. Its mechanism of action, however, is not clear. Direct antiviral activity and immunomodulatory functions have been implicated. Plasmacytoid dendritic cells (pDCs) are the principal source of type 1 interferon during viral infection. The interaction of pDCs with HCV-infected hepatocytes is the subject of intense recent investigation, but the effect of ribavirin on pDC activation has not been evaluated. In this study we showed that ribavirin augments toll-like receptors 7 and 9-mediated IFNα/β expression from pDCs and up-regulated numerous interferon-stimulated genes. Using the H77S.3 HCV infection and replication system, we showed that ribavirin enhanced the ability of activated pDCs to inhibit HCV replication, correlated with elevated induction of IFNα. Our findings provide novel evidence that ribavirin contributes to HCV inhibition by augmenting pDCs-derived type 1 IFN production.

Viral hepatitis C therapy: pharmacokinetic and pharmacodynamic considerations

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

Relationship between GH/IGF-1 axis, graft recovery, and early survival in patients undergoing liver transplantation

Background. High levels of IGF-1 have been reported in patients with initial poor function of the graft after liver transplantation (LT). Correlation with other clinical variables or early survival has not been extensively investigated. Aim. To evaluate the GH/IGF-1 profile as a function of liver recovery and patients' early survival after LT. Methods. 30 transplanted patients (23 survivors and 7 nonsurvivors), were retrospectively enrolled in the study. GH and IGF-1 serum levels were assessed at baseline, graft reperfusion, and 1, 7, 15, 30 , 90, and 360 days after LT. Individual biochemical variables were also recorded. Results. After grafting, IGF-1 in blood linearly correlated with cholesterol (r = 0.6, P = 0.001). IGF-1 levels from day 15 after surgery were statistically higher in survivors as compared to nonsurvivors. ROC curves analysis identified an IGF-1 cut-off >90 μg/L, from day 15 after surgery, as a good predictor of survival (sensitivity 86%, specificity 95%, and P < 0.001). Conclusions. After LT, GH levels correlate with the extent of cytolysis, while IGF-1 is an indicator of liver synthetic function recovery. IGF-1 levels >90 μg/L (day 15–30) seem to be an indicator of short-term survival.

Negative predictive value of IL28B, SLC28A2, and CYP27B1 SNPs and low RBV plasma exposure for therapeutic response to PEG/IFN-RBV treatment

OBJECTIVES

The response rate to treatment of chronic hepatitis C virus-genotype 1 and 4 infections was recently found to be strongly influenced by many polymorphisms. The aim of our study was to carry out an integrated analysis of the effects of polymorphisms and ribavirin (RBV) plasma exposure on outcome.

METHODS

The retrospective analysis included 174 patients. IL28B, CYP27B1, SLC29A1, SLC28A3, and SLC28A2 polymorphisms were genotyped and tested for association with sustained virological response. The impact of RBV plasma exposure during the first 3 months of therapy on outcome was also investigated.

RESULTS

Considering patients infected by hepatitis C virus-1/4, 3 polymorphisms (IL28B rs8099917TT, CYP27B1 rs4646536TT, and CNT2 rs11854484TT) were associated with sustained virological response. The number of negative variant allele and low RBV exposure were correlated to percentage increasing to therapy failure, suggesting some degree of cumulative effect of the 4 factors. A cutoff of 2.5 μg/mL of RBV was found to be associated with outcome (area under ROC [AUROC] curve = 0.64, sensitivity = 55.0%, and specificity = 71.2%, P = 0.020). In multivariate logistic regression analyses, each variant allele and RBV plasma exposure cutoff were independently associated with outcome.

CONCLUSIONS

In this study, we found that additional polymorphisms and RBV plasma exposure are also able to influence the achievement of response. Regardless of the magnitude of RBV pharmacokinetic exposure, the negative predictive value of the polymorphisms here investigated is much stronger than the positive one.

The application and mechanism of action of ribavirin in therapy of hepatitis C

Ribavirin has been used as an antiviral agent for several decades. Although it has activity against numerous viruses, its major use clinically has been in the treatment of respiratory syncytial virus in paediatric patients and chronic HCV infection in both children and adults. This review highlights the clinical application and mechanism of action of ribavirin and discusses the future role of ribavirin in treatment of HCV where there are intense research efforts to improve therapy.

Interference with ERK and STAT signaling pathways and inhibition of hepatitis C virus replication by ribavirin

Ribavirin in combination with interferon (IFN)-α is the approved treatment for hepatitis C virus (HCV) infection. Interference of ribavirin with signaling events is involved in its biological activities. However, little is known of signaling pathways induced by ribavirin following HCV infection. In human hepatoma cells, effects of ribavirin on ERK and signal transducers and activators of transcription (STAT) pathways, HCV replication, and antiviral gene expression were evaluated before and after cell culture-derived HCV infection. Ribavirin reduced phosphorylation of Raf, MEK, ERK, Tyk2, and STAT1, but selectively increased STAT3 phosphorylation. IFN-α synergistically regulated ERK and STAT3 phosphorylation with ribavirin, and up-regulated expression and phosphorylation of STAT1. Ribavirin dose-dependently decreased HCV RNA replication and HCV protein expression, with slight induction of IFN regulatory factor 9 and IFN-stimulated gene 15. Ribavirin and IFN-α exerted a synergetic inhibitory effect on HCV. ERK and STAT pathways were down-regulated by ribavirin following HCV infection. These results suggest that ribavirin may mediate anti-HCV activity through interference with ERK and STAT pathways.

Plasma ribavirin trough concentrations during treatment of chronic hepatitis C in genotype-1 patients

GOALS

To investigate the correlation between virological response and plasma ribavirin trough concentrations (RBV Ctrough) during the full period of chronic hepatitis C (CHC) treatment.

STUDY

Multicenter prospective cohort study. Total 119 patients with CHC genotype-1 were treated with peginterferon alfa-2a (pegIFN) and RBV for 48 weeks. RBV quantification was carried out at week 4 (W4), W8, W12, W16, W24, W32, and W40 of treatment.

RESULTS

The mean RBV Ctrough value during treatment was 2.5±0.9 mg/L in total patients. At no time point of treatment were patients with RBV Ctrough average correlated with early and sustained virological response (SVR), but those with RBV Ctrough ≥5 mg/L (95th percentile) at any time point (22/119, 18%) were correlated with SVR (P=0.02). Such high RBV Ctrough values were found from the second to the fourth months of treatment in 73% of these patients (16/22), and this was independently associated with SVR (odds ratio=3.6, 95% confidence interval:1.02-13.2, P=0.04).

CONCLUSION

Our data do not support RBV plasma monitoring as a tool to optimize treatment in patients with CHC genotype-1, but show that a high RBV plasma concentration could improve SVR rates.

Erythrocyte and plasma ribavirin concentrations in the assessment of early and sustained virological responses to pegylated interferon-alpha 2a and ribavirin in patients coinfected with hepatitis C virus and HIV

OBJECTIVES

To determine the relationship between erythrocyte and plasma ribavirin concentrations in hepatitis C virus (HCV)/HIV-coinfected patients, and to correlate ribavirin exposure with early and sustained virological response (EVR and SVR) and haemoglobin level reductions.

METHODS

Clinical and biological data from 68 HCV/HIV-coinfected patients were recorded at baseline, week 4 (W4), week 12 and at 24 weeks after completion of treatment. Plasma and erythrocyte ribavirin concentrations were determined 12 h after the final ribavirin dose (C(min)).

RESULTS

Erythrocyte ribavirin concentrations were 100-fold higher than plasma concentrations, with a significant relationship between them (P < 0.05). In patients with HCV genotype 1 or 4, a plasma ribavirin C(min) threshold of 1.95 mg/L at W4 tended to predict EVR [sensitivity 44%; specificity 87%; AUC 0.67 (95% CI 0.50-0.84)] and was predictive of SVR [sensitivity 58%; specificity 84%; AUC 0.71 (95% CI 0.51-0.90)]. Among patients with these HCV genotypes, an erythrocyte ribavirin C(min) threshold of 146 mg/L at W4 was found to be the best value for discriminating between responders and non-responders for both EVR [sensitivity 67%; specificity 75%; AUC 0.58 (95% CI 0.24-0.93)] and SVR [sensitivity 50%; specificity 80%; AUC 0.70 (95% CI 0.39-1.01)]. We also demonstrated a significant relationship between reduced haemoglobin levels and plasma ribavirin C(min) at W4 (P = 0.05).

CONCLUSIONS

Therapeutic drug monitoring may be useful for the management of anti-HCV treatment in HCV/HIV-coinfected patients.

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.

Ribavirin potentiates interferon action by augmenting interferon-stimulated gene induction in hepatitis C virus cell culture models

The combination of pegylated interferon (PEG-IFN) and ribavirin is the standard treatment for chronic hepatitis C. Our recent clinical study suggests that ribavirin augments the induction of interferon-stimulated genes (ISGs) in patients treated for hepatitis C virus (HCV) infection. In order to further characterize the mechanisms of action of ribavirin, we examined the effect of ribavirin treatment on ISG induction in cell culture. In addition, the effect of ribavirin on infectious HCV cell culture systems was studied. Similar to interferon (IFN)-α, ribavirin potently inhibits JFH-1 infection of Huh7.5.1 cells in a dose-dependent manner, which spans the physiological concentration of ribavirin in vivo. Microarray analysis and subsequent quantitative polymerase chain reaction assays demonstrated that ribavirin treatment resulted in the induction of a distinct set of ISGs. These ISGs, including IFN regulatory factors 7 and 9, are known to play an important role in anti-HCV responses. When ribavirin is used in conjunction with IFN-α, induction of specific ISGs is synergistic when compared with either drug applied separately. Direct up-regulation of these antiviral genes by ribavirin is mediated by a novel mechanism different from those associated with IFN signaling and intracellular double-stranded RNA sensing pathways such as RIG-I and MDA5. RNA interference studies excluded the activation of the Toll-like receptor and nuclear factor κB pathways in the action of ribavirin.

CONCLUSION

Our study suggests that ribavirin, acting by way of a novel innate mechanism, potentiates the anti-HCV effect of IFN. Understanding the mechanism of action of ribavirin would be valuable in identifying novel antivirals.