Ribavirin monotherapy for chronic hepatitis C infection: a Cochrane Hepato-Biliary Group systematic review and meta-analysis of randomized trials

Efficacy and Safety of Sofosbuvir/Velpatasvir Plus Ribavirin in Patients with Hepatitis C Virus-Related Decompensated Cirrhosis

A fixed-dose combination of sofosbuvir/velpatasvir (SOF/VEL) plus weight-based ribavirin (RBV) for 12 weeks is recommended for the treatment of patients with hepatitis C virus (HCV)-associated decompensated cirrhosis. However, large global studies, while confirming the effectiveness of SOF/VEL in a broad range of patients, often exclude these patients. This Phase 2, single-arm, open-label study in adult patients with HCV-associated decompensated cirrhosis in France and the USA aimed to provide further data on the safety and efficacy of SOF/VEL plus RBV for 12 weeks in this population. Patients were treated with a fixed-dose combination of SOF 400 mg/VEL 100 mg plus weight-based RBV once daily for 12 weeks. The inclusion criteria were chronic HCV infection (≥6 months), quantifiable HCV RNA at screening, Child-Turcotte-Pugh class B or C cirrhosis, and liver imaging within 6 months of Day 1 to exclude hepatocellular carcinoma. Among 32 patients who initiated treatment, 78.1% achieved sustained virologic response 12 weeks after the end of treatment (SVR12). Failure to achieve SVR12 was due to non-virologic reasons (investigator discretion, n = 1; death, n = 6). All 25 patients in the per-protocol population achieved SVR12 and all but one achieved sustained virologic response 24 weeks after the end of treatment. Adverse events (AEs) were as expected for a patient population with advanced liver disease. All Grade 3-4 and serious AEs and deaths were deemed unrelated to treatment. In patients with HCV-associated decompensated cirrhosis, SOF/VEL plus RBV achieved high SVR12 rates and was generally well tolerated.

Potential Virus Involvement in Alzheimer's Disease: Results from a Phase IIa Trial Evaluating Apovir, an Antiviral Drug Combination

Background:

Accumulating data suggest infectious agents are involved in Alzheimer’s disease (AD). The two primary aims of this trial were to assess safety and efficacy of an antiviral drug combination on AD progression.

Objective:

The trial evaluated whether Apovir, a combination of two antiviral agents, pleconaril (active on enteroviruses) and ribavirin (active on several viruses), could slow AD progression.

Methods:

Sixty-nine patients 60–85 years were treated with Apovir or placebo for 9 months and followed until 12 months after end of treatment. Cognitive tests, safety, biomarkers, drug plasma, and cerebrospinal fluid concentrations were assessed.

Results:

The tolerability of Apovir was compromised as demonstrated by the large drop-out rate and increased frequency and severity of adverse events. The primary endpoint, demonstrating a difference in change from baseline to 9 months between groups in ADAS-cog total score, was not met (p = 0.1809). However, there were observations indicating potential effects on both ADAS-cog and CDR-SB but these effects need to be verified. Also, there was a decrease in cerebrospinal fluid amyloid-β in Apovir at 9 months (p = 0.0330) but no change in placebo.

Conclusion:

This was the first randomized, placebo controlled clinical trial exploring antiviral treatment on AD progression. The trial is considered inconclusive due to the large drop-out rate. New trials are needed to verify if the indications of effect observed can be confirmed and which component(s) in Apovir contributed to such effects. Pleconaril alone may be studied to improve the tolerability and to verify if enterovirus is involved in the disease process.

Low dose ribavirin has been effective in the treatment of incapacitating muco-cutaneous extrahepatic manifestations in patients with hepatitis C with contraindication or no access for approved antiviral treatment

BACKGROUND AND STUDY AIMS

Chronic hepatitis C virus (HCV) is a major public health problem and represents a common cause of chronic liver disease worldwide. The Egyptian Demographic Health Survey (EDHS) has estimated HCV prevalence in Egypt to be 14.7%. HCV can affect multiple organ systems and cause a variety of extrahepatic manifestations. Most of extrahepatic manifestations affect the skin and mucous membranes; such as lichen planus (LP), psoriasis, and leucocytoclastic vasculitis. The treatment of extrahepatic manifestations has been disappointing in patients not indicated for interferon with no access for the new costly all oral treatments.

PATIENTS AND METHODS

In 2014, thirty Egyptian patients with incapacitating mucocutaneous extrahepatic manifestations due to chronic HCV infection, not indicated for interferon, have been randomised into two groups; group I treated with ribavirin (5-10mg/kg daily divided into 2 doses), and group II treated with local steroids for 3months. Patients were followed up for 3months. Dermatology life quality index score has been measured before and after treatment for all patients.

RESULTS

A significant improvement of mucocutaneous lesions has been accomplished in group I in comparison to group II (p<0.01). All lesions in group I showed a significant improvement except psoriasis (p>0.05). A significant improvement of dermatology life quality index score has been found in patients in group I when compared to group II (p<0.05).

CONCLUSION

We conclude that low dose ribavirin was effective in the treatment of incapacitating mucocutaneous extrahepatic manifestations of chronic HCV infection in patients with contraindication or no access to the approved antiviral treatments.

Deviation from intention to treat analysis in randomised trials and treatment effect estimates: meta-epidemiological study

OBJECTIVE

To examine whether deviation from the standard intention to treat analysis has an influence on treatment effect estimates of randomised trials.

DESIGN

Meta-epidemiological study.

DATA SOURCES

Medline, via PubMed, searched between 2006 and 2010; 43 systematic reviews of interventions and 310 randomised trials were included.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

From each year searched, random selection of 5% of intervention reviews with a meta-analysis that included at least one trial that deviated from the standard intention to treat approach. Basic characteristics of the systematic reviews and randomised trials were extracted. Information on the reporting of intention to treat analysis, outcome data, risk of bias items, post-randomisation exclusions, and funding were extracted from each trial. Trials were classified as: ITT (reporting the standard intention to treat approach), mITT (reporting a deviation from the standard approach), and no ITT (reporting no approach). Within each meta-analysis, treatment effects were compared between mITT and ITT trials, and between mITT and no ITT trials. The ratio of odds ratios was calculated (value <1 indicated larger treatment effects in mITT trials than in other trial categories).

RESULTS

50 meta-analyses and 322 comparisons of randomised trials (from 84 ITT trials, 118 mITT trials, and 108 no ITT trials; 12 trials contributed twice to the analysis) were examined. Compared with ITT trials, mITT trials showed a larger intervention effect (pooled ratio of odds ratios 0.83 (95% confidence interval 0.71 to 0.96), P=0.01; between meta-analyses variance τ(2)=0.13). Adjustments for sample size, type of centre, funding, items of risk of bias, post-randomisation exclusions, and variance of log odds ratio yielded consistent results (0.80 (0.69 to 0.94), P=0.005; τ(2)=0.08). After exclusion of five influential studies, results remained consistent (0.85 (0.75 to 0.98); τ(2)=0.08). The comparison between mITT trials and no ITT trials showed no statistical difference between the two groups (adjusted ratio of odds ratios 0.92 (0.70 to 1.23); τ(2)=0.57).

CONCLUSIONS

Trials that deviated from the intention to treat analysis showed larger intervention effects than trials that reported the standard approach. Where an intention to treat analysis is impossible to perform, authors should clearly report who is included in the analysis and attempt to perform multiple imputations.

Effects of ribavirin monotherapy on the viral population in patients with chronic hepatitis C genotype 1: direct sequencing and pyrosequencing of the HCV regions

Ribavirin remains essential to chronic hepatitis C treatment. This paper investigates the influence of ribavirin priming to steady state before combined pegylated-interferon/ribavirin treatment on viral kinetics, ribavirin trough concentrations, genetic variability within HCV-core, -NS5B and -NS5A, and response to antiviral therapy. A prospective cohort study was made of 27 chronic hepatitis C genotype 1 naïve patients who received four weeks of ribavirin followed by pegIFN-α-2a/ribavirin for 48 weeks (Group A). The results obtained were compared with those for a control/historical group (Group B). In addition, direct sequencing and pyrosequencing were applied to determine ribavirin monotherapy-induced sequence changes. The rapid, early, and sustained virological response values obtained were 48%, 89%, and 52%, respectively, in Group A, and 52%, 90%, and 52% in Group B (P > 0.05). In the four-week combined treatment, the Group A patients showed a greater decrease in HCV-RNA (2.3 log10  IU/ml vs. 1.2 log10  IU/ml; P = 0.04), lower alanine aminotransferase levels (23.5 ± 1.33 U/L vs. 60.11 ± 18 U/L; P < 0.001) and higher mean ribavirin trough concentrations (3.28 ± 1.26 mg/L vs. 1.74 ± 0.7 mg/L; P = 0.001). No general increase in rates of nucleotide substitutions in the ribavirin monotherapy-treated patients was observed in NS5B, ISDR, or PKRbd, but there was a decrease in silent mutations in the HCV core (P = 0.04). This result was confirmed by pyrosequencing in the NS5A region. It is concluded that the ribavirin priming combined treatment with pegIFN-α-2a does not improve sustained virological response rates in HCV genotype 1 naïve infected patients. However, the greater reductions in viral load and alanine aminotransferase levels, together with the higher ribavirin trough concentration values obtained, could reflect the greater effectiveness of the treatment. Ribavirin does not have a mutagenic effect on the virus in patients with chronic hepatitis C.

The impact of inosine triphosphatase variants on hemoglobin level and sustained virologic response of chronic hepatitis C in Korean

TWO VARIANTS OF THE INOSINE TRIPHOSPHATASE (ITPA

rs1127354, rs7270101) gene cause ITPA deficiency and protect against the hemolytic toxicity of ribavirin. We investigated the clinical significance of ITPA variants in Korean patients treated with pegylated interferon (PEG-IFN) plus ribavirin. Of the 133 patients, 108 were CC and 25 were non-CC at rs1127354 (groups A and B, respectively). On the other hand, at rs7270101 all 133 were AA. The mean values of Hemoglobin (Hgb) after 4, 8, and 12 weeks of treatment in groups A and B were 12.2 and 14.0, 11.8 and 13.2, and 11.5 and 12.9, respectively (P=0.001, 0.036, 0.036). Sustained virologic response (SVR) was achieved in 67.8% (40/59) of genotype 1 patients and in 75% (27/36) of non-genotype 1 patients. Regarding ITPA variants, SVR was achieved by 66% and 80% of genotype 1 (P=0.282), and by 78% and 71% (P=0.726) of non-genotype 1. SVR was not significantly different in groups A and B. In conclusion, non-CC at rs1127354 without involvement of rs7270101 is strongly associated with protection from ribavirin-induced anemia, however, ITPA genotype is not associated with SVR.

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.

Antiviral treatment for HCV recurrence after liver transplantation: when, how much and for how long?

Chronic HCV infection is one of the leading causes of end-stage liver disease and hepatocellular carcinoma worldwide, and it constitutes one of the principal indications for liver transplant. However, recurrent HCV infection after liver transplant is nearly universal, and leads to decreased patient and graft survival in the long-term. Strategies to approach this problem that is commonly encountered in clinical practice include treating patients in order to obtain viral clearance before the transplant, pre-emptive treatment, which refers to therapy initiation before there is histological evidence of disease, and treatment for established recurrence. Therapy at these diverse time points poses varied challenges regarding the feasibility of the treatment, possibility of treatment completion, risk of adverse effects and different response rates. Furthermore, advances are being made in identifying prognostic markers of viral response, which could aid in decreasing the disease burden.

Hepato-biliary clinical trials and their inclusion in the Cochrane Hepato-Biliary Group register and reviews

BACKGROUND AND AIMS

The Cochrane Hepato-Biliary Group (CHBG) is one of the 52 collaborative review groups within The Cochrane Collaboration. The activities of the CHBG focus on collecting hepato-biliary randomized clinical trials (RCT) and controlled clinical trials (CCT), and including them in systematic reviews with meta-analyses of the trials. In this overview, we present the growth of The CHBG Controlled Trials Register, as well as the systematic reviews that have been produced since March 1996.

RESULTS

The CHBG register includes almost 11,000 RCT and 700 CCT publications. The earliest RCT in the register were published in 1955, and the earliest CCT in 1945. From 1945 to 1980, there were less than 100 publications each year. From 1981 to 1997, their number increased from over 100 to 600 a year. After 1997, the number of publications seems to have been decreasing. The CHBG has published 199 protocols for systematic reviews and 107 systematic reviews through to August 2009 in which 21% of the RCT and CCT were included. The CHBG reviews have been cited approximately 1200 times.

CONCLUSIONS

A large amount of work has been carried out since 1996. However, there is still much to do, as the CHBG register contains a great number of RCT and CCT on topics that have not yet been systematically reviewed.

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.

Maintenance ribavirin monotherapy delays fibrosis progression in liver transplant recipients with recurrent hepatitis C at high risk of progression

BACKGROUND

Fibrosis in liver transplant recipients with recurrent HCV is fast, yet, different patterns of progression are recognized.

AIMS

To investigate histological findings associated with maintenance ribavirin monotherapy in patients with recurrent HCV transplanted > or =4 years earlier.

METHODS

14 recipients at high risk of progression (fibrosis progression rate >0.33 units/year and/or persistently elevated ALT) were assigned to receive ribavirin for 3 years. 11 patients at lower risk of progression (FPR < or =0.33 units/year and normal ALT) as controls. Biopsies were obtained yearly since transplant and 7 consecutive biopsies were evaluated.

RESULTS

Improved necroinflammation (reduction > or =2 grading) was observed in 7 treated with ribavirin and 3 untreated patients, while 1 and 3 patients worsened respectively. Fibrosis improved (reduction >1 staging) in 2 ribavirin-treated patients, unchanged in 10 and worsened (increase > or =1 staging) in 2. Fibrosis progression decreased from 0.48+/-0.27 observed during the 3-year pre-treatment period to 0.04+/-0.31 units/year (p=0.003) during the 3 years of ribavirin. Among untreated fibrosis remained unchanged in 1 and worsened in 10 (p<0.001), yearly fibrosis progression rate increasing from 0.15+/-0.17 units/year to 0.42+/-0.39 units/year (p=0.10).

CONCLUSIONS

Maintenance ribavirin monotherapy delays fibrosis progression in high risk patients, offering an alternative strategy for those failing to respond to conventional treatment.

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.

Thiazolides: a new class of antiviral drugs

BACKGROUND

Thiazolides have emerged as a new class of broad-spectrum antiviral drugs, and the first thiazolide, nitazoxanide, is in late-stage clinical trials for treating chronic hepatitis C.

OBJECTIVE

To review the chemistry, pharmacology, toxicology and efficacy of thiazolides as antiviral agents with emphasis on clinical development of nitazoxanide in treating chronic hepatitis C.

METHODS

Literature search, information from Romark Laboratories and my personal experience with the discovery and development of thiazolides serve as the sources for this review.

CONCLUSIONS

Thiazolides are metabolically stable, highly bound to plasma proteins and are associated with a favorable toxicology profile. Phase II clinical trials have demonstrated efficacy and safety of nitazoxanide added to peginterferon with or without ribavirin in treating patients with chronic hepatitis C. More limited clinical data indicated potential in treating chronic hepatitis B, and three randomized controlled trials have demonstrated efficacy in reducing the duration of viral gastroenteritis. New generation thiazolides with the nitro group of nitazoxanide replaced by a non-reducible group are not active against anaerobes but retain broad-spectrum activity against viruses. Further studies are needed. Research indicates that these drugs may play an important and complementary role in combination with other classes of antiviral drugs.

Meta-analyses on viral hepatitis

This article summarizes the meta-analyses of interventions for viral hepatitis A, B, and C. Some of the interventions assessed are described in small trials with unclear bias control. Other interventions are supported by large, high-quality trials. Although attempts have been made to adjust for unclear bias control, analysis of publication bias and other biases is difficult when only few trials are available. It is possible that some of the meta-analyses presented in this article are biased. Furthermore, performing updated cumulative meta-analyses also may introduce random error.3,4 The extent and direction of bias may vary. On average, however, bias leads to overestimated intervention benefits.1 Accordingly, the benefit of some of the interventions suggested in this article may be exaggerated by systematic and random errors. Additional research including large, randomized trials is necessary to clarify the true intervention effects.

A support vector machine approach to assess drug efficacy of interferon-alpha and ribavirin combination therapy

BACKGROUND

Interferon-alpha (IFNalpha) in combination with ribavirin can be used for the treatment of patients with chronic hepatitis C. This therapeutic approach achieves an overall sustained response rate of approximately 40%, but treatment takes 6-12 months and patients often experience significant adverse reactions.

OBJECTIVE

We aim to develop a tool to distinguish potential responders from nonresponders prior to initiation of IFNalpha-ribavirin treatment.

METHODS

Using single nucleotide polymorphisms (SNPs) and viral genotype, we applied the support vector machine (SVM) algorithm to build a tool to predict responsiveness to IFNalpha-ribavirin combination therapy. Furthermore, we utilized the SVM algorithm with the recursive feature elimination method to identify a subset of factors that are significantly more influential than the others.

RESULTS AND CONCLUSION

The SVM model is a promising method for inferring responsiveness to IFNalpha dealing with the complex nonlinear relationship between factors (such as SNPs and viral genotype) and successful therapy. In this study, we demonstrate that our tool may allow patients and doctors to make more informed decisions by analyzing host SNP and viral genotype information.

De novo nephrotic syndrome following pegylated interferon alfa 2b/ribavirin therapy for chronic hepatitis C infection

This paper describes the case of a patient with HCV, without previous evidence of nephropathy, who following two well-tolerated cycles of treatment with interferon alone developed nephrotic syndrome after a third attempt with ribavirin associated with peginterferon alfa 2b. The patient exhibited a total remission when the antiviral treatment was discontinued.

Nonresponse to treatment for hepatitis C: current management strategies

Chronic hepatitis C affects >170 million people worldwide, causing cirrhosis and liver cancer in a sizeable proportion of patients. Substantial progress has been made in the treatment of chronic hepatitis C. More than 50% of patients can achieve sustained virological response after 24-48 weeks of interferon and ribavirin combination therapy, making chronic hepatitis C a potentially curable disease. However, a large proportion of patients with chronic hepatitis C do not clear the virus after current standard therapy. Hepatitis C virus develops two pathways to counteract the antiviral effect of interferon. Some chronic hepatitis C patients may have a virus that is more resistant to interferon therapy, while other patients appear to have defective immune responses or poor tolerance or compliance to interferon-based antiviral therapy. The possible strategies to improve antiviral efficiency in these nonresponders are to increase the dosage, prolong the duration of treatment and improve the compliance of patients. A total of 6-15% of prior nonresponders to standard interferon plus ribavirin therapy will respond to re-treatment with peginterferon plus ribavirin, while 32-50% of patients who have relapsed will respond to re-treatment. New small molecules are under development to treat chronic hepatitis C and may be important particularly in the treatment of prior nonresponders to current standard therapy.

Hepatitis C: epidemiology, diagnosis, and management

Chronic hepatitis C virus (HCV) infection is a common worldwide problem. The infection may progress to cirrhosis with the subsequent development of complications including hepatocellular carcinoma. There has been substantial progress in understanding various aspects of HCV infection, including the epidemiology, virology, natural history of chronic infection, and medical therapy.

Adverse events associated with high-dose ribavirin: evidence from the Toronto outbreak of severe acute respiratory syndrome

Study Objectives. To distinguish adverse events related to ribavirin therapy from those attributable to severe acute respiratory syndrome (SARS), and to determine the rate of potential ribavirin‐related adverse events.

Design. Retrospective cohort study.

Setting. Hospitals in Toronto, Ontario, Canada.

Patients. A cohort of 306 patients with confirmed or probable SARS, 183 of whom received ribavirin and 123 of whom did not, between February 23, 2003, and July 1, 2003. Of the 183 treated patients, 155 (85%) received very high‐dose ribavirin; the other 28 treated patients received lower‐dose regimens.

Measurements and Main Results. Data on all patients with SARS admitted to hospitals in Toronto were abstracted from charts and electronic databases onto a standardized form by trained research nurses. Logistic regression was used to evaluate the association between ribavirin use and each adverse event (progressive anemia, hypomagnesemia, hypocalcemia, bradycardia, transaminitis, and hyperamylasemia) after adjusting for SARS‐related prognostic factors and corticosteroid use. In the primary logistic regression analysis, ribavirin use was strongly associated with anemia (odds ratio [OR] 3.0, 99% confidence interval [CI] 1.5–6.1, p<0.0001), hypomagnesemia (OR 21, 99% CI 5.8–73, p<0.0001), and bradycardia (OR 2.3, 99% CI 1.0–5.1, p=0.007). Hypocalcemia, transaminitis, and hyperamylasemia were not associated with ribavirin use. The risk of anemia, hypomagnesemia, and bradycardia attributable to ribavirin use was 27%, 45%, and 17%, respectively.

Conclusions. High‐dose ribavirin is associated with a high rate of adverse events. The use of high‐dose ribavirin is appropriate only for the treatment of infectious diseases for which ribavirin has proven clinical efficacy, or in the context of a clinical trial. Ribavirin should not be used empirically for the treatment of viral syndromes of unknown origin.

Current non-AIDS antiviral chemotherapy

The evolution of antiviral therapy began with developments in the management of influenza and herpes simplex keratitis in the 1960s and early 1970s. However, the field exploded with the successful treatment of herpes simplex encephalitis, herpes zoster and genital herpes simplex virus infections, all occurring in the late 1970s and early 1980s. These advances have contributed to the development of therapies for HIV that have transformed the lives of infected patients in recent years. The clinical fruit of all of these research advances has been an armamentarium of drugs that can be used to successfully treat a variety of viral illnesses. In addition to HIV/AIDS, current antiviral therapy focuses primarily on herpesviruses, hepatitis viruses and influenza. Notably, considerable progress remains to be made in these areas. Moreover, a variety of additional viral diseases currently require the development of specific therapies.

Hepatology may have problems with putative surrogate outcome measures

A surrogate outcome measure is a laboratory measurement, a physical sign, or another intermediate substitute that is able to predict an intervention's effect on a clinically meaningful outcome. A clinical outcome detects how a patient feels, functions, or survives. Surrogate outcome measures occur faster or more often, are cheaper, and/or are less invasively achieved than the clinical outcome. In practice, validation is surprisingly often overlooked, especially if a biologic plausible rationale is proposed. Surrogate outcomes must be validated before use. The first step in validation is to demonstrate a correlation between the putative surrogate and the clinical outcome, e.g., the higher the surrogate the shorter time to death. However, a correlation is not sufficient to validate the surrogate. The second step is to establish if the intervention's effect on the surrogate outcome accurately predicts the intervention's effect on the clinical outcome. In hepatology a number of putative surrogate outcomes are used both in clinical research and in clinical practice without having been properly validated. Sustained virological response to interferons and ribavirin in patients with chronic hepatitis C, serum bilirubin concentration following ursodeoxycholic acid or immunosuppressants for patients with primary biliary cirrhosis, and nutritional outcomes following artificial nutrition for liver patients may not be valid surrogates for morbidity or mortality. The challenge is to develop reliable surrogates, both to facilitate the development of new interventions and to ensure our patients and us that these interventions are effective clinically.

Replicative homeostasis III: implications for antiviral therapy and mechanisms of response and non-response

While improved drug regimens have greatly enhanced outcomes for patients with chronic viral infection, antiviral therapy is still not ideal due to drug toxicities, treatment costs, primary drug failure and emergent resistance. New antiviral agents, alternative treatment strategies and a better understanding of viral pathobiology, host responses and drug action are desperately needed. Interferon (IFN) and ribavirin, are effective drugs used to treat hepatitis C (HCV), but the mechanism(s) of their action are uncertain. Error catastrophe (EC), or precipitous loss of replicative fitness caused by genomic mutation, is postulated to mediate ribavirin action, but is a deeply flawed hypothesis lacking empirical confirmation. Paradoxically ribavirin, a proven RNA mutagen, has no impact on HCV viraemia long term, suggesting real viruses, replicating in-vitro, as opposed to mathematical models, replicating in-silico, are likely to resist EC by highly selective replication of fit (~consensus sequence) genomes mediated, in part, by replicative homeostasis (RH), an epicyclic mechanism that dynamically links RNApol fidelity and processivity and other viral protein functions. Replicative homeostasis provides a rational explanation for the various responses seen during treatment of HCV, including genotype-specific and viral load-dependent differential response rates, as well as otherwise unexplained phenomena like the transient inhibition and rebound of HCV viraemia seen during ribavirin monotherapy. Replicative homeostasis also suggests a primarily non-immunological mechanism that mediates increased immune responsiveness during treatment with ribavirin (and other nucleos(t)ide analogues), explicating the enhanced second-phase clearance of HCV ribavirin promotes and, thus, the apparent immunomodulatory action of ribavirin. More importantly, RH suggests specific new antiviral therapeutic strategies.

Ribavirin inhibits angiogenesis by tetrahydrobiopterin depletion

Ribavirin is a broad-spectrum antiviral drug that is used to treat hepatitis C virus (HCV)-infected patients. The virological response after ribavirin treatment appears to be insufficient to fully explain ribavirin-induced beneficial effects. Angiogenesis plays a pathogenic role in HCV-induced liver damage. Here, we investigated the influence of therapeutic ribavirin concentrations on angiogenesis. Ribavirin inhibited endothelial cell tube formation in vitro and vessel formation in the chick chorioallantoic membrane assay in vivo. Ribavirin inhibits inosine monophosphate dehydrogenase, which causes depletion of cellular GTP and in turn reduction of cellular tetrahydrobiopterin levels. The availability of tetrahydrobiopterin limits NO production by endothelial NO synthase. Ribavirin reduced levels of tetrahydrobiopterin (as revealed by HPLC), NO (as revealed by electron spin resonance spectroscopy), and cGMP (as revealed by RIA) in endothelial cells. Addition of tetrahydrobiopterin or NO prevented ribavirin-induced tube formation inhibition. In conclusion, angiogenesis inhibition by ribavirin has not been described before. This inhibition may contribute to ribavirin-induced pharmacological effects including adverse events.