A phase-I study of the safety, pharmacokinetics, and antiviral activity of combination didanosine and ribavirin in patients with HIV-1 disease. AIDS Clinical Trials Group 231 Protocol Team

Current and emerging strategies for the diagnosis, prevention and treatment of Lassa fever

ABSTRACT 

Lassa fever (LF) is a potentially fatal disease that affects an estimated 300,000–500,000 people in endemic areas of west Africa each year. Though past studies have identified fatality rates of 5–20% in patients suspected to have contracted Lassa virus (LASV), new studies using more precise clinical diagnoses and modern diagnostic assays show fatalities rates above 60% in acutely ill patients from endemic regions. Currently, there are no approved vaccines or therapeutics, and only one Comformité Européenne (CE) marked rapid immunodiagnostic for acute LASV infection. Therefore, preventing LASV transmission is the primary goal in endemic regions. Development of rapid immunodiagnostics and research into the efficacy of current treatment options continues toward saving lives in west Africa as well as creating a line of defense against the nefarious use of LASV in bioterrorism settings.

Drug-Drug Interactions Among Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV) Medications

One-fourth of individuals diagnosed with the human immunodeficiency virus concomitantly have the hepatitis C virus infection. Since the discovery of highly active antiretroviral therapy, liver complications have become the leading cause of morbidity and mortality in HIV-HCV coinfected individuals. Optimal treatment in this patient population is critical, as coinfection has been linked to deterioration of both disease states. The objective of this review article is to highlight the current literature on drug-drug interactions between HIV and HCV treatments. The management of the treatment of coinfection patients has been covered extensively in numerous other publications.

Hepatitis C virus infection in HIV-infected patients

The hepatitis C virus (HCV) is a spherical enveloped RNA virus of the Flaviviridae family, classified within the Hepacivirus genus. Since its discovery in 1989, HCV has been recognized as a major cause of chronic hepatitis and hepatic fibrosis that progresses in some patients to cirrhosis and hepatocellular carcinoma. In the United States, approximately 4 million people have been infected with HCV, and 10,000 HCVrelated deaths occur each year. Due to shared routes of transmission, HCV and HIV co-infection are common, affecting approximately one third of all HIV-infected persons in the United States. In addition, HIV co-infection is associated with higher HCV RNA viral load and a more rapid progression of HCV-related liver disease, leading to an increased risk of cirrhosis. HCV infection may also impact the course and management of HIV disease, particularly by increasing the risk of antiretroviral drug-induced hepatotoxicity. Thus, chronic HCV infection acts as an opportunistic disease in HIV-infected persons because the incidence of infection is increased and the natural history of HCV infection is accelerated in co-infected persons. Strategies to prevent primary HCV infection and to modify the progression of HCV-related liver disease are urgently needed among HIV/HCV co-infected individuals.

[Treatment of hepatitis C virus in HIV-positive patients]

Hepatitis C virus (HCV)-HIV coinfection currently occurs in more than 30% of HIV-positive patients in Spain. Nowadays, the treatment of choice for chronic hepatitis due to HCV infection in HIV-positive patients is pegylated interferon plus ribavirin. This combination achieves an overall cure rate of 50%, which is somewhat lower than those obtained in patients with HCV monoinfection. Adverse effects are frequent, leading to treatment withdrawal in 10-20% of patients. Importantly, there are three new features of hepatitis C in patients with HIV: (1) the recent development of epidemic outbreaks of acute hepatitis due to HCV infection in HIV-positive men caused by homosexual activity, (2) pharmacogenetic markers in the form of genetic polymorphisms near the IL28B gene related to response to HCV treatment as well as spontaneous eradication of HCV after acute infection, and (3) new antiviral molecules have allowed triple combination treatments to be designed and the preliminary results of clinical trials reporting high response rates are highly promising.

Review of the literature and proposed guidelines for the use of oral ribavirin as postexposure prophylaxis for Lassa fever

Lassa fever is an acute viral hemorrhagic illness; the virus is endemic in West Africa and also of concern with regard to bioterrorism. Transmission of Lassa virus between humans may occur through direct contact with infected blood or bodily secretions. Oral administration of the antiviral drug ribavirin is often considered for postexposure prophylaxis, but no systematically collected data or uniform guidelines exist for this indication. Furthermore, the relatively low secondary attack rates for Lassa fever, the restriction of the area of endemicity to West Africa, and the infrequency of high-risk exposures make it unlikely that controlled prospective efficacy trials will ever be possible. Recommendations for postexposure use of ribavirin can therefore be made only on the basis of a thorough understanding and logical extrapolation of existing data. Here, we review the pertinent issues and propose guidelines based on extensive review of the literature, as well as our experience in this field. We recommend oral ribavirin postexposure prophylaxis for Lassa fever exclusively for definitive high-risk exposures. These guidelines may also serve for exposure to other hemorrhagic fever viruses susceptible to ribavirin.

[AIDS Study Group/Spanish AIDS Plan consensus document on antiretroviral therapy in adults with human immunodeficiency virus infection (updated January 2010)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy recommendations for adult patients with human immunodeficiency virus infection.

METHODS

To formulate these recommendations a panel made up of members of the Grupo de Estudio de Sida (Gesida, AIDS Study Group) and the Plan Nacional sobre el Sida (PNS, Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of human immunodeficiency virus (HIV) infection, the efficacy and safety of clinical trials, and cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings. Three levels of evidence were defined according to the data source: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not to recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r), but other combinations are possible. Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts below 350 cells/microl; 2) When CD4 counts are between 350 and 500 cells/microl, therapy should be started in case of cirrhosis, chronic hepatitis C, high cardiovascular risk, HIV nephropathy, HIV viral load above 100,000 copies/ml, proportion of CD4 cells under 14%, and in people aged over 55; 3) Therapy should be deferred when CD4 are above 500 cells/microl, but could be considered if any of previous considerations concurs. Treatment should be initiated in case of hepatitis B requiring treatment and should be considered for reduce sexual transmission. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures but undetectable viral loads maybe possible with the new drugs even in highly drug experienced patients. Genotype studies are useful in these situations. Drug toxicity of ART therapy is losing importance as benefits exceed adverse effects. Criteria for antiretroviral treatment in acute infection, pregnancy and post-exposure prophylaxis are mentioned as well as the management of HIV co-infection with hepatitis B or C.

CONCLUSIONS

CD4 cells counts, viral load and patient co-morbidities are the most important reference factors to consider when initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized therapy approach in order to achieve undetectable viral load under any circumstances.

Antiviral hepatitis and antiretroviral drug interactions

More and more HIV-infected patients are treated for viral hepatitis, increasing interactions. HEPATITIS C: The concomitant use of didanosine and ribavirin increases the risk of mitochondrial toxicity, responsible for pancreatitis and/or lactic acidosis. Lactic acidosis is characterized by a high mortality rate. Thus, didanosine, but also stavudine, should not be co-administered with ribavirin. Cases of hepatic decompensation have been reported in cirrhotics concomitantly receiving ribavirin and didanosine. Thus, this co-admininistration should be contraindicated in patients with advanced liver fibrosis. Anemia is a frequent side effect of ribavirin. In patients with zidovudine-related anemia, this drug should be discontinued before prescribing ribavirin. Erythropoietin may help to improve the haemoglobin level. HEPATITIS B: Adefovir significantly decreases the plasma levels of saquinavir. Pancreatitis may occur with the co-administration of didanosine and tenofovir. Thus this co-administration should be avoided. Atazanavir concentrations are decreased when tenofovir is co-administered. Thus, atazanavir should be boosted with ritonavir, when combined with tenofovir. Atazanavir increases the concentrations of tenofovir, with the potential risk of increasing the adverse events of tenofovir, including renal disorders. Tenofovir area under the curve is increased if lopinavir-ritonavir are co-administered. The main interactions, with a fatal risk, are observed with didanosine, when co-administered with ribavirin (hepatitis C) or with tenofovir (hepatitis B). Anemia is frequent, but usually moderate, when zidovudine is co-administered with ribavirin. Other interactions are usually easy to manage.

Treatment of viral hepatitis in HIV-coinfected patients-adverse events and their management

For the treatment of HBV/HIV-co-infection, study data on interferon-based therapy are very limited and insufficient to draw any specific conclusions. In contrast, data on HBV-polymerase inhibitors (lamivudine, adefovir, tenofovir) are available from controlled trials. Lamivudine is well tolerated and safe, however, development of HBV-resistance is frequent. Adefovir has a nephrotoxic potential and may at least theoretically induce antiretroviral resistance in HBV/HIV-patients treated with adefovir. Tenofovir has gastrointestinal side effects, is associated with hypophospatemia, which has not induced serious osteopenia so far and may have a nephrotoxic potential. For HCV/HIV-co-infection pegylated interferon alpha plus ribavirin is standard of care. Flu-like symptoms, fatigue and depressive mood changes are frequent. In patients with a history of neurotic or minor depression initiation of treatment with antidepressants before the start of interferon-based therapy should be considered. Weight loss may be pronounced in individual cases. A marked decrease in absolute, but not relative CD4 +/- cells is the rule, but no relevant increase in opportunistic infection was observed, and anaemia (<10 g/dl) is reported in up to 30% of patients. Neutropenia (< 1,000 cells/microl) is observed in up to 50% of the patients. Adverse events specific to the HCV/HIV-patient population as compared to HCV-mono-infected patients are the occurrence of hyperlactataemia/lactic acidosis and hepatic decompensation.

Treatment algorithm for the management of hepatitis C in HIV-coinfected persons

In the era of highly effective antiretroviral therapy (ART), HCV-related liver disease has emerged as a significant cause of morbidity and mortality. Accordingly, expert panels have recommend that coinfected patients undergo medical evaluation for HCV-related liver disease, consideration for HCV treatment and, if indicated, orthotopic liver transplantation. While the treatment of such patients is complicated by medical, and psychiatric comorbidities, HIV disease, and concurrent antiretroviral therapy, randomized controlled trials support the safety, tolerability and efficacy of HCV treatment with peginterferon alfa (PEG-IFN) plus ribavirin (RBV) in HIV-infected persons. Although, the available data has led to consensus among experts regarding the need to medically manage HCV disease in HIV-infected persons, uncertainty remains regarding the best treatment algorithm for coinfected patients.

Effect of ribavirin on intracellular and plasma pharmacokinetics of nucleoside reverse transcriptase inhibitors in patients with human immunodeficiency virus-hepatitis C virus coinfection: results of a randomized clinical study

The intracellular triphosphorylation and plasma pharmacokinetics of lamivudine (3TC), stavudine (d4T), and zidovudine (ZDV) were assessed in a pharmacokinetic substudy, in 56 human immunodeficiency virus-hepatitis C virus (HIV-HCV) coinfected patients receiving peginterferon alfa-2a (40KD) 180 microg/week plus either placebo or ribavirin (RBV) 800 mg/day in the AIDS PEGASYS Ribavirin International Coinfection Trial. There were no significant differences between patients treated with RBV and placebo in plasma pharmacokinetics parameters for the nucleoside reverse transcriptase inhibitors (NRTIs) at steady state (weeks 8 to 12): ratios of least squares mean of area under the plasma concentration-time curve (AUC(0-12 h)) were 1.17 (95% confidence interval, 0.91 to 1.51) for 3TC, 1.44 (95% confidence interval, 0.58 to 3.60) for d4T and 0.85 (95% confidence interval, 0.50 to 1.45) for ZDV, and ratios of least squares mean plasma C(max) were 1.33 (95% confidence interval, 0.99 to 1.78), 1.06 (95% confidence interval, 0.68 to 1.65), and 0.84 (95% confidence interval, 0.46 to 1.53), respectively. Concentrations of NRTI triphosphate (TP) metabolites in relation to those of the triphosphates of endogenous deoxythymidine-triphosphate (dTTP) and deoxcytidine-triphosphate (dCTP) were similar in the RBV and placebo groups. Differences (RBV to placebo) in least squares mean ratios of AUC(0-12 h) at steady state were 0.274 (95% confidence interval, -0.37 to 0.91) for 3TC-TP:dCTP, 0.009 (95% confidence interval, -0.06 to 0.08) for d4T-TP:dTTP, and -0.081 (95% confidence interval, -0.40 to 0.24) for ZDV-TP:dTTP. RBV did not adversely affect HIV-1 replication. In summary, RBV 800 mg/day administered in combination with peginterferon alfa-2a (40KD) does not significantly affect the intracellular phosphorylation or plasma pharmacokinetics of 3TC, d4T, and ZDV in HIV-HCV-coinfected patients.

Hepatitis C virus infection in HIV-infected patients

Because of shared routes of transmission, hepatitis C and HIV coinfection is common in the United States, affecting 15% to 30% of HIV-infected individuals. In the era of highly effective antiretroviral therapy, hepatitis C virus (HCV)-related liver disease has emerged as a significant cause of morbidity and mortality. Accordingly, the Infectious Diseases Society of America and the American Association for the Study of Liver Disease guidelines for the management of HCV recommend that patients with HIV/HCV undergo medical evaluation for HCV-related liver disease and consideration for HCV treatment and, if indicated, orthotopic liver transplantation. However, the treatment of patients with HIV/HCV is complicated by the relatively high prevalence of medical and psychiatric comorbidities and the challenges of anti-HCV therapy in the setting of HIV disease and antiretroviral therapy. Nonetheless, recently completed randomized controlled trials provide evidence of the safety, tolerability, and efficacy of HCV treatment with pegylated interferon-alpha plus ribavirin in HIV-infected individuals. This review focuses on the epidemiology, natural history, and management of HCV in the HIV-infected patient.

Tolérance et interactions médicamenteuses des traitements anti-VIH et anti-VHC

Treating Hepatitis C among HIV patients under antiretroviral drug therapy requires a high degree of vigilance and continuous monitoring because of frequent problems with intolerance and/or drug interactions. Recent studies, including three therapeutic trials, on Ribavic, APRICOT, and ACTG A5671, have given some insights on following these patients up. The adverse effects are relatively similar in HCV-HIV-co-infected patients and patients infected by HCV only. Their frequency is, on the other hand, higher among HCV-HIV-Co-infected patients. The adverse-effects are consistent, in a non-exhaustive way, with pseudo influenza-like symptoms, fever, myalgia, cephalgia, with psychiatric disorders (irritability, depression, etc.); endocrine disorders (thyroid dysfunction, diabetes...); and with hematological anomalies especially anemia and leucopenia. But the percentage of lymphocyte T CD4 is not modified, therefore there is no risk of opportunistic infection. Pharmacokinetic interactions between antiretroviral drugs and treatment for HCV infection including ribavirin plus interferon alpha (IFN-alpha) or pegylated IFN are described. They are almost exclusively due to the combination of ribavirin and of nucleoside analogue reverse transcriptase inhibitors. One of the principal consequences is the emergence of mitochondrial toxicity defined by the occurrence of hyperlactatemia, or acute pancreatitis). Thus, some combinations should be avoided such as ddI+ribavirin and ddI+d4T+ribavirin. The d4T+ribavirin combination must also be used with caution.

Serum hepatic enzyme manifestations in patients with severe acute respiratory syndrome: retrospective analysis

AIM

To evaluate the hepatic function in patients with severe acute respiratory syndrome (SARS) and possible causes of hepatic disorder in these patients.

METHODS

One hundred and eighty-two patients with SARS were employed in a retrospective study that investigated hepatic dysfunction. Liver alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactic dehydrogenase (LDH) were analyzed in these patients. Patients with different hospital treatments were further investigated.

RESULTS

Of the 182 patients, 128(70.3%) had abnormal ALT activity, 57(31.3%) had abnormal AST activity and 87(47.8%) had abnormal LDH activity. The peak of elevated hepatic enzyme activities occurred between the sixth day and the tenth day after the first day of reported fever. Of the 182 patients, 160(87.9%) had been treated with antibiotics, 137(75.2%) with Ribavirin, and 115(63.2%) with methylpredisolone. There was no statistically significant correlation between the duration of Ribavirin treatment and hepatic dysfunction.

CONCLUSION

Abnormal liver functions were common in patients with SARS and could be associated with virus replication in the liver.

High Rate of Didanosine-Related Mitochondrial Toxicity in HIV/HCV-Coinfected Patients Receiving Ribavirin

Background

Nucleoside analogues may induce mitochondrial toxicity, particularly didanosine. Ribavirin increases didanosine exposure, which might be clinically relevant when coadministered in HIV/HCV-coinfected patients.

Objective

To evaluate, among 89 patients receiving highly active antiretroviral therapy (HAART) and therapy for chronic hepatitis C, clinically relevant mitochondrial toxicity in those treated with concomitant ribavirin and didanosine ( n=35, 39%).

Methods

From January 2000 to July 2002 longitudinal analysis of the incidence and clinical course of didanosine-related hyperamylasaemia, pancreatitis, hyperlactataemia/lactic acidosis or neuropathy. Risk factors were evaluated using univariate and multivariate Cox's proportional hazards model.

Results

Among 35 patients who received concomitant didanosine (400 mg/day in 86%) and ribavirin (≥10 mg/kg/day in 91%), 20 (57%) developed one or more adverse events after a mean of 87 days. Most frequent laboratory abnormalities were hyperamylasaemia (18 patients, 51%) and hyperlactataemia (eight patients, 23%). Acute pancreatitis and symptomatic hyperlactataemia developed in 10 (28%) and six (17%) patients, respectively. Two patients (6%) with pancreatitis and severe lactic acidosis died; the other patients recovered uneventfully despite continuation of anti-HCV therapy in 83% after didanosine withdrawal in 40%. In the Cox's model higher baseline amylase levels (HR: 1.04, 95% CI: 1.02–1.06, P=0.001) and three nucleoside reverse transcriptase inhibitor-based HAART (HR: 5.3, 95% CI: 1.73–16.24, P=0.003) were significantly associated to toxicity.

Conclusions

The coadministration of didanosine and ribavirin should be avoided in HIV/HCV-coinfected patients, due to a high rate of clinically significant toxicity, particularly in triple nucleoside-based HAART. Amylase levels should be strictly monitored, especially if elevated at baseline.

Treatment of hepatitis C virus in the coinfected patient

Since hepatitis C virus (HCV) was first identified in 1989, the impact of HCV infection on the HIV-infected population has been steadily increasing. It is now known that HCV affects the course and treatment of HIV disease in coinfected individuals (those infected with both HCV and HIV). Although there are significant data regarding the treatment of HCV in non-coinfected individuals, there are numerous questions that still remain regarding how to monitor and treat HCV infection in the coinfected population. This article reviews the available data regarding treatment of HCV in the coinfected population as well as how these individuals should be monitored, before and during HCV therapy, as well as how to address the numerous side effects associated with HCV treatment. To meet the demands of the coinfected population. HIV nurses must be willing to expand their knowledge to support, educate, assess, and advocate for coinfected individuals.

Clinical experiences with interferon as monotherapy or in combination with ribavirin in patients co-infected with HIV and HCV

Human immunodeficiency virus (HIV) co-infection accelerates progression of hepatitis C virus (HCV) toward cirrhosis. Thus, with the increase of life expectancy observed after introduction of combination antiretroviral treatment, liver disease is becoming an increasing cause of morbidity and mortality in HIV-infected patients. In addition, HCV co-infection blunts CD4 restoration induced by HAART and increases HAART hepatotoxicity. For all these reasons, anti-HCV treatment is mandatory in HIV seropositives. The perfect treatment of hepatitis C should not only be safe and effective, but it should not have any adverse impact on HIV diseases and concurrent anti-HIV therapy. Two drugs are currently licensed for treatment of HCV: interferon alfa (IFNalpha) and ribavirin. Three hundred and thirty-eight patients have been included in pilot studies on the efficacy and tolerability of IFNalpha monotherapy: 16% showed sustained response and 10% dropped out. No significant adverse impact of IFNalpha monotherapy on HIV diseases or antiretroviral treatment has been observed. IFNalpha and ribavirin in combination have been introduced more recently: only 88 patients were included in pilot studies published as full papers with a 25% sustained response and an 11% rate of drop outs. Anemia and cumulative toxicity with didanosine were the most important side effects of combination treatment, but it did not affect HIV disease progression. Higher rates of sustained response (33%) without increase of side effects have been observed in preliminary experiences with the new long-acting pegylated interferons in combination with ribavirin. The search for the perfect treatment continues.

[Recommendations of the Spanish AIDS Study Group (GESIDA) and the National Aids Plan (PNS) for antiretroviral treatment in adult patients with human immunodeficiency virus infection in 2002]

OBJECTIVE

To provide an update of recommendation on antiretroviral treatment (ART) in HIV-infected adults.Methods. These recommendations have been agreed by consensus by a committee of the spanish AIDS Study Group (GESIDA) and the National AIDS Plan. To do so, advances in the physiopathology of AIDS and the results on efficacy and safety in clinical trials, cohort and pharmacokinetics studies published in biomedical journals or presented at congresses in the last few years have been reviewed. Three levels of evidence have been defined according to the data source: randomized studies (level A), case-control or cohort studies (level B) and expert opinion (level C). Whether to recommend, consider, or not to recommend ART has been established for each situation.

RESULTS

Currently, ART with combinations of at least three drugs constitutes the treatment of choice in chronic HIV infection. In patients with symptomatic HIV infection, initiation of ART is recommended. In asymptomatic patients initiation of ART should be based on the CD41/mL lymphocyte count and on the plasma viral load (PVL): a) in patients with CD41 lymphocytes < 200 cells/mL, initiation of ART is recommended; b) in patients with CD41 lymphocytes between 200 and 300 cells/mL, initiation of ART should, in most cases, be recommended; however, it could be delayed when the CD41 lymphocyte count remains close to 350 cells/mL and the PVL is low, and c) in patients with CD41 lymphocytes > 350 cells/mL, initiation of ART can be delayed. The aim of ART is to achieve an undetectable PVL. Adherence to ART plays a role in the durability of the antiviral response. Because of the development of cross-resistance, the therapeutic options in treatment failure are limited. In these cases, genotypic analysis is useful. Toxicity limits ART. The criteria for ART in acute infection, pregnancy and postexposure prophylaxis and in the management of coinfection with HIV and hepatitis C and B virus are controversial.

CONCLUSIONS

The current approach to initiating ART is more conservative than in previous recommendations. In asymptomatic patients, the CD41 lymphocyte count is the most important reference factor for initiating ART. Because of the considerable number of drugs available, more sensitive monitoring methods (PVL) and the possibility of determining resistance, therapeutic strategies have become much more individualized.

Management of hepatitis C in human immunodeficiency virus-infected patients

Hepatitis C virus-related liver disease and its associated complications are steadily emerging health concerns in persons co-infected with human immunodeficiency virus. The increasing number of liver-related deaths in human immunodeficiency virus-hepatitis C virus co-infected individuals supports the compelling argument for more aggressive treatment in these patients. The safety and efficacy of interferon/ribavirin in human immunodeficiency virus/hepatitis C virus co-infected patients is currently under evaluation. Despite well-documented concern over highly active antiretroviral therapy-associated hepatotoxicity human immunodeficiency virus/hepatitis C virus co-infected patients should be offered antiretroviral therapy. Since management of co-infected patients is complex a multidisciplinary approach is needed in order to facilitate care and help patients to achieve a positive outcome.

Interferon-alpha-2b plus ribavirin: a review of its use in the management of chronic hepatitis C

Relatively few patients (< or =20%) with chronic hepatitis C achieve a sustained virological response after interferon-alpha monotherapy. Hence, alternative treatment strategies such as the addition of the broad spectrum antiviral agent ribavirin to interferon-alpha-2b have been investigated. Combination therapy with subcutaneous interferon-alpha-2b [3 million units (MU) three times per week] plus oral ribavirin (1000 to 1200 mg/day) has proven effective in several well designed trials of 24 to 48 weeks' duration in adult patients with compensated chronic hepatitis C. Compared with interferon-alpha-2b (3 or 6 MU three times per week) with or without placebo, combination treatment with interferon-alpha-2b plus ribavirin significantly enhanced end-of-treatment and sustained virological and biochemical response rates in treatment-naive and treatment-experienced patients [sustained virological response rates in treatment-naive recipients (6 to 19% vs 31 to 43% of patients); sustained overall (virological plus biochemical) response rates in nonresponders to (1 vs 14%) or relapsers (4 to 5% vs 30 to 44%) after previous interferon-alpha monotherapy]. Forty-eight weeks of combination therapy was superior to 24 weeks in treatment-naive patients infected with hepatitis virus C (HCV) genotype 1, whereas response rates were similar at 24 and 48 weeks in those infected with other HCV genotypes. Furthermore, there were marked improvements in histological inflammatory scores in patients who responded to treatment with either interferon-alpha-2b plus ribavirin or interferon-alpha-2b alone. Although adverse events associated with either drug during combination therapy occurred frequently, these were generally mild to moderate in intensity and were consistent with those reported for each individual agent. Twenty-six percent of patients required dosage modifications of one or both drugs during combination therapy.

CONCLUSIONS

Interferon-alpha-2b plus ribavirin is an efficacious first- and second-line therapy in adult patients with compensated chronic hepatitis C, significantly improving sustained virological and biochemical responses versus interferon-alpha-2b monotherapy. The tolerability profile of interferon-alpha-2b plus ribavirin therapy is consistent with the individual profiles of these agents with no evidence of additive effects. The place of interferon-alpha-2b plus ribavirin combination therapy in relation to newer agents, including pegylated interferons-alpha and other multidrug regimens, remains to be determined in this rapidly evolving area of therapeutic management. Currently, combination therapy with interferon-alpha-2b plus ribavirin is recommended as first-line therapy for patients with chronic hepatitis C and compensated liver disease, and is an option for use as second-line therapy in those who have relapsed after, or failed to respond to, previous treatment with interferon-alpha.

Treatment of hepatitis C and anemia in human immunodeficiency virus-infected patients

Because of shared modes of transmission, co-infection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) is common. Co-infection with HIV increases HCV virus load, liver-related mortality, and the risk of sexual and perinatal transmission of HCV, and it may accelerate HCV disease progression. With combination interferon (IFN)-alpha 2b/ribavirin or pegylated IFN-alpha 2b/ribavirin therapy, long-term remission is possible for HCV-infected patients. Preliminary evidence suggests that the combination of IFN-alpha 2b/ribavirin can achieve similar response rates in HCV/HIV-co-infected individuals with no adverse effect on HIV RNA concentrations. Although adverse effects are more frequent with combination therapy than with IFN-alpha monotherapy, most are manageable. In addition, few instances of drug-drug antagonism have been reported among drugs used to treat each disease, although further study is necessary. Ribavirin-associated hemolytic anemia is a potential problem in a patient population that is already susceptible to anemia but is manageable with recombinant human erythropoietin (epoetin alfa).

The biological effects of structural variation at the meta position of the aromatic rings and at the end of the alkenyl chain in the alkenyldiarylmethane series of non-nucleoside reverse transcriptase inhibitors

In an effort to elucidate a set of structure-activity relationships in the alkenyldiarylmethane (ADAM) series of non-nucleoside reverse transcriptase inhibitors, a number of modifications were made at two locations: (1) the meta positions of the two aromatic rings and (2) the end of the alkenyl chain. Forty-two new ADAMs were synthesized and evaluated for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cell culture and for inhibition of HIV-1 reverse transcriptase. The size of the aromatic substituents was found to affect anti-HIV activity, with optimal activity appearing with Cl, CH(3), and Br substituents and with diminished activity occurring with smaller (H and F) or larger (I and CF(3)) substituents. The substituents at the end of the alkenyl chain were also found to influence the antiviral activity, with maximal activity associated with methyl or ethyl ester groups and with diminished activity resulting from substitution with higher esters, amides, sulfides, sulfoxides, sulfones, thioesters, acetals, ketones, carbamates, ureas, and thioureas. Twelve of the new ADAMs displayed submicromolar EC(50) values for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cells. Selected ADAMs, 19 and 21, were compared to previously published ADAMs 15 and 17 for antiviral efficacy and activity against the HIV-1 reverse transcriptase enzyme. All four ADAMs were found to inhibit HIV-1 reverse transcriptase enzyme activity, to inhibit the replication of a variety of HIV-1 clinical isolates representing syncytium-inducing, nonsyncytium-inducing, and subtype representative isolates, and to inhibit HIV-1 replication in monocytes. Subsequent assessment against a panel of site-directed reverse transcriptase mutants in NL4-3 demonstrated no effect of the K103N mutation on antiviral efficacy and a slight enhancement (6- to 11-fold) in sensitivity to AZT-resistant viruses. Additionally, ADAMs 19 (44-fold) and 21 (29-fold) were more effective against the A98G mutation (found in association with nevirapine resistance in vitro), and ADAM 21 was 5-fold and 2-fold more potent against the Y181C inactivation mutation than the previously reported ADAMs 15 and 17, respectively. All four ADAMs were tested for efficacy against a multidrug-resistant virus derived from a highly experienced patient expressing resistance to the reverse transcriptase enzyme inhibitors AZT, ddI, 3TC, d4T, foscarnet, and nevirapine, as well as the protease inhibitors indinavir, saquinavir, and nelfinavir. ADAM 21 was 2-fold more potent than ADAM 15 and 6-fold more potent than ADAMs 17 and 19 at preventing virus replication. Thus, we have identified a novel series of reverse transcriptase inhibitors with a favorable profile of antiviral activity against the primary mutation involved in clinical failure of non-nucleoside reverse transcriptase inhibitors, K103N, and that retain activity against a multidrug-resistant virus.

Treatment of hepatitis C virus and HIV co-infections

Hepatitis C coinfection is common in patients with HIV, particularly in injection-drug users. Hepatitis C virus levels tend to be higher in coinfected patients, and histologic progression is more rapid than in patients with HCV alone. The efficacy of interferon monotherapy in HIV patients with an adequate CD4 cell count is comparable to that observed in patients without HIV. The combination of interferon plus ribavirin and pegylated interferon will further improve response rates. Interferon therapy is associated with leukopenia and a decrease in absolute CD4 cell count. Some concern remains that ribavirin might reduce the activity of pyrimidine analogues such as zidovudine and stavudine, and HIV-RNA levels should be followed when these medications are given concurrently. It is hoped that in time, new drug development will make the multiple-drug therapeutic strategy that has been highly successful in the management of HIV feasible for the treatment of HCV.

Phosphorylation of nucleoside analog antiretrovirals: a review for clinicians

Nucleoside analogs (zidovudine, didanosine, zalcitabine, stavudine, abacavir, lamivudine) have been administered as antiretroviral agents for more than a decade. They undergo anabolic phosphorylation by intracellular kinases to form triphosphates, which inhibit human immunodeficiency virus replication by competitively inhibiting viral reverse transcriptase. Numerous methods are used to elucidate the intracellular metabolic pathways of these agents. Intracellular and extracellular factors affect intracellular phosphorylation. Lack of standardization and complexity of methods used to study phosphorylation in patients limit interpretation of study results and comparability of findings across studies. However, in vitro and in vivo studies give important insights into mechanisms of action, metabolic feedback mechanisms, antiviral effects, and mechanisms of toxicity, and have influenced dosing regimens of nucleoside analogs.

Infections of the liver in HIV-infected patients

The liver is a common site of pathology in HIV-infected patients. In patients with controlled HIV and minimal immunosuppression, infection with hepatitis viruses is common owing to the risk factors of sexual transmission or parenteral drug use. In patients with AIDS, the liver is a common site of lymphohematogenous dissemination of several infectious pathogens. A thorough diagnostic approach leads to a diagnosis of most hepatobiliary processes. The therapeutic nihilism that has surrounded hepatic disease, including viral hepatitis, is unwarranted, because treatment of the underlying HIV and the hepatic process may improve the quality of life and longevity of these patients.

Hepatitis C virus and human immunodeficiency virus: clinical issues in coinfection

The prevalence of hepatitis C virus (HCV) and human immunodeficiency virus (HIV) coinfection ranges from nearly 30% to over 50%, depending on the population. Shared modes of transmission and the success of current antiretroviral regimens have contributed to the emergence of HCV as a significant pathogen in the HIV-positive population. HIV coinfection appears to worsen HCV infection, with studies showing more severe fibrosis, a higher frequency of cirrhosis, and increased deaths from liver disease. HIV coinfection may also increase the rate of maternal-fetal transmission of HCV. Similarly, studies suggest a more rapid progression to AIDS or death for HCV genotypes 1a and 1b than for other genotypes in HIV-infected patients with hemophilia. Highly active antiretroviral therapy (HAART), such as HIV protease inhibitors, has no effect on HCV infection and may transiently increase ALT, AST, and hepatitis C viral load. Hepatotoxicity associated with HAART may or may not be related to the presence of HCV and may depend on the specific agents used. Data suggest that treating chronic hepatitis C in HIV-co-infected patients can decrease fibrosis, increase T-cell responsiveness to HCV antigens, and decrease the rate of fatal hepatomas. Interferon alpha may provide sustained biochemical or virologic responses in HIV/HCV-coinfected patients. The combination of interferon-alpha and ribavirin may also be a treatment option but is more complex, and additional research is needed. Treating HCV infection in HIV/HCV-coinfected individuals may help lower the hepatitis C viral load and permit treatment with protease inhibitors.

A combinatorial ledge: reverse transcriptase fidelity, total body viral burden, and the implications of multiple-drug HIV therapy for the evolution of antiviral resistance

The chronicity, high mutation rates, and high circulating titers of HIV during the 'stable' phase of infection make rapid evolution of resistance mutations a key predictor of antiretroviral efficacy. Recent advances in measurement of viral RNA titers, turnover dynamics and the in vivo spectrum of resistance mutations allow realistic in vivo estimates of important kinetic parameters of within-patient evolution of viral resistance. First-order estimates of the frequency of viral genotypes necessary for resistance to many antiretroviral combination regimens indicate that many such genotypes pre-exist in patients prior to initiation of therapy. The combinatorial nature of observed multiply-resistant genotypes, however, along with current estimates of total-body viral load and viral turnover dynamics, imply a strikingly sharp transition associated with the change from two-drug to three-drug antiretroviral regimens: pre-existing resistance being near-certain in the first instance but highly unlikely in the second. This abrupt change, a 'combinatorial ledge', carries with it a number of important implications for the understanding and control of HIV infection and other potential targets of antiviral therapy.