Failure of acyclovir to enhance the antiviral effect of alpha lymphoblastoid interferon on HBe-seroconversion in chronic hepatitis B. A multi-centre randomized controlled trial

Novel Insights to Enhance Therapeutics With Acyclovir in the Management of Herpes Simplex Encephalitis

Acyclovir is an antiviral drug poorly absorbed in the gastrointestinal tract due to its hydrophilicity, with low oral bioavailability (~20%). Although acyclovir is prescribed in the management of herpes simplex encephalitis (HSE), the disease has a poor prognosis, particularly if the treatment is delayed, reaching mortality rates of 70% if left untreated. Thus, high acyclovir doses are administered by intravenous (IV) infusion, usually at a dosage of 10 mg kg^-1 8-hourly in adults with normal renal function. However, the mortality related to HSE treated with acyclovir remains high (~20%) and permanent sequelae are commonly reported after 1 year (~50%). This review analyzed clinical trials following IV acyclovir administration. Novel insights aiming to improve drug bioavailability were reviewed, including acyclovir or its prodrugs, leading to the systemic distribution of the drug or drug targeting. Much research effort has been made to improve antiviral therapy, searching for delivery systems increasing acyclovir bioavailability by non-invasive pathways, such as oral and nasal pathways, or parenterally administered nanotechnology-based systems leading to drug targeting. Nanocarriers administered by non-invasive pathways represent feasible alternatives to treat HSE, even though not be industrially manufactured yet.

Application of kinase bypass strategies to nucleoside antivirals

Nucleoside and nucleotide analogs have served as the cornerstones of antiviral therapy for many viruses. However, the requirement for intracellular activation and side-effects caused by distribution to off-target sites of toxicity still limit the efficacy of the current generation of drugs. Kinase bypass strategies, where phosphorylated nucleosides are delivered directly into cells, thereby, removing the requirement for enzyme catalyzed phosphorylation steps, have already changed the face of antiviral therapy in the form of the acyclic nucleoside phosphonates, cidofovir, adefovir (given orally as its dipivoxil prodrug) and tenofovir (given orally as its disoproxil prodrug), currently used clinically. These strategies hold further promise to advance the field of antiviral therapy with at least 10 kinase bypass and tissue targeted prodrugs, representing seven distinct prodrug classes, currently in clinical trials. This article reviews the history of kinase bypass strategies applied to nucleoside antivirals and the evolution of different tissue targeted prodrug strategies, highlighting clinically relevant examples.

Synthesis and early development of hexadecyloxypropylcidofovir: an oral antipoxvirus nucleoside phosphonate

Hexadecyloxypropyl-cidofovir (HDP-CDV) is a novel ether lipid conjugate of (S)-1-(3-hydroxy-2-phosphonoylmethoxypropyl)-cytosine (CDV) which exhibits a remarkable increase in antiviral activity against orthopoxviruses compared with CDV. In contrast to CDV, HDP-CDV is orally active and lacks the nephrotoxicity of CDV itself. Increased oral bioavailability and increased cellular uptake is facilitated by the lipid portion of the molecule which is responsible for the improved activity profile. The lipid portion of HDP-CDV is cleaved in the cell, releasing CDV which is converted to CDV diphosphate, the active metabolite. HDP-CDV is a highly effective agent against a variety of orthopoxvirus infections in animal models of disease including vaccinia, cowpox, rabbitpox and ectromelia. Its activity was recently demonstrated in a case of human disseminated vaccinia infection after it was added to a multiple drug regimen. In addition to the activity against orthopoxviruses, HDP-CDV (CMX001) is active against all double stranded DNA viruses including CMV, HSV-1, HSV-2, EBV, adenovirus, BK virus, orf, JC, and papilloma viruses, and is under clinical evaluation as a treatment for human infections with these agents.

High rates of HBsAg seroconversion in HBeAg-positive chronic hepatitis B patients responding to interferon: a long-term follow-up study

BACKGROUND/AIMS

To assess the HBsAg seroconversion rate and its impact on the long-term outcome in chronic hepatitis B patients treated with conventional interferon, and to analyze the serum HBsAg concentration prior to seroconversion.

METHODS

Ninety-seven HBeAg-positive patients were retrospectively evaluated. Sustained virological response (SVR) was defined as HBeAg seroconversion and undetectable serum HBV-DNA 48 weeks after treatment discontinuation. HBsAg level was assessed at yearly intervals until seroconversion in SVRs.

RESULTS

Twenty-five patients (26%) achieved SVR. By multivariate analysis, SVR was associated with low serum HBV DNA level and severe liver fibrosis. During a median follow-up of 14 years (range, 5-20 years), 28 patients (29%) developed HBsAg seroconversion including 16 SVRs (64%) and 12 non-SVRs (16%), p < 0.001. HBsAg quantification showed a major decrease (median = 46%, range = 19-100%) in the first year after interferon starting in SVR patients. Six patients developed hepatocellular carcinoma, none of them had undergone HBsAg seroconversion. Liver fibrosis improved in 70% of patients with HBsAg seroconversion compared to 30% of those without HBsAg seroconversion (p < 0.01).

CONCLUSIONS

HBsAg seroconversion is achieved with a high steady rate in patients responding to interferon, and associated with excellent outcome. Prospective studies are needed to clarify the utility of on-treatment quantitative serum HBsAg in interferon-based therapy.

Long-term follow-up of alpha-interferon treatment of patients with chronic hepatitis B

Data on the long-term effects of interferon alfa (IFN) treatment on disease progression and mortality in patients with chronic hepatitis B (CHB) are limited. To evaluate factors that influence clinical outcome and survival, we performed a follow-up study on 165 hepatitis B e antigen (HBeAg) positive CHB patients treated with IFN between 1978 and 2002. The median IFN dose was 30 megaunits (MU)/week (range, 2-70 MU/week), and the median duration of therapy was 16 weeks (range, 1-92 weeks). Response to treatment was defined as HBeAg loss within 12 months after the end of IFN therapy. Median follow-up was 8.8 years (range, 0.3-24 years). Fifty-four patients (33%) responded to IFN treatment. Relapse (HBeAg reactivation) occurred in 7 of the 54 (13%) responders. Fifty-two percent of the responders lost hepatitis B surface antigen (HBsAg) as compared with 9% of the nonresponders (P <.001). Liver histology showed a decreased necroinflammatory activity and less progression of fibrosis in responders. Twenty-six patients died during follow-up. Hepatocellular carcinoma (HCC) was found in 8 patients, 6 of whom were nonresponders. Of the two responders who developed HCC, one patient had relapsed after discontinuation of therapy. Multivariate analysis showed significantly improved survival (relative risk (RR) of death 0.28, 95% CI 0.10-0.78) and reduced risk of developing HCC (RR 0.084, 95% CI 0.09-0.75) in responders. In conclusion, response to IFN therapy results in a prolonged clinical remission with an increased rate of HBsAg seroconversion and improved liver histology. Our results indicate that after correction for baseline factors, response to IFN therapy increases survival and reduces the risk of developing HCC.

A pilot study of beta-interferon for treatment of patients with chronic hepatitis B who failed to respond to alpha-interferon

BACKGROUND/AIMS

Alpha-interferon achieves persistent loss of hepatitis B virus (HBV) in about 30-40% of patients with chronic hepatitis B. In non-responder patients, the disease may progress leading to complications such as cirrhosis and hepatocellular carcinoma. The aim of the current study was to evaluate the efficacy of beta-interferon in patients with chronic hepatitis B who did not respond to one course of alpha-interferon.

METHODS

Twenty nine alpha-interferon-non-responder patients with chronic hepatitis B (11 hepatitis B e antigen, HBeAg-positive; 18 HBeAg-negative) were treated with 6 million units beta-interferon five times a week for 24 weeks. The post-treatment follow-up lasted for 48 weeks.

RESULTS

At the end of treatment, 38% of patients (18% HBeAg-positive; 50% HBeAg-negative) had normal serum aminotransferase levels and negative serum HBV DNA. At the end of follow-up, HBV DNA was no longer detectable in serum in 21% of patients (18% HBeAg-positive; 22% HBeAg-negative). Beta-interferon was well tolerated and safe.

CONCLUSIONS

This pilot study suggests that beta-interferon therapy is effective and safe in the retreatment of patients with chronic hepatitis B who had not responded to a previous alpha-interferon cycle.

Drug discovery and development of antiviral agents for the treatment of chronic hepatitis B virus infection

A safe and effective vaccine for hepatitis B virus (HBV) has been available for nearly twenty years and currently campaigns to provide universal vaccination in developing countries are underway. Nevertheless, chronic HBV infection remains a leading cause of chronic hepatitis worldwide and there is a strong need for safe and effective antiviral therapies. Attempts to identify and develop antiviral agents to treat chronic HBV infection remains focused on nucleoside analogs such as 3TC (lamivudine), adefovir dipivoxil, (bis-POMPMEA), and others. However, advances in our understanding of the molecular biology of HBV and the development of new assays for HBV polymerase activity, such as the reconstitution of active HBV polymerase in vitro, should facilitate large screening efforts for non-nucleoside reverse transcriptase inhibitors. Recent advances have furthered our understanding of clinical resistance to lamivudine, have provided new approaches to treatment, and have offered new perspectives on the major challenges to the identification and development of antiviral agents for chronic HBV infection. Here, in an update to our previous review article that appeared in this series [59a], we focus on recent advances that have occurred in the areas of virus structure and replication, in vitro viral polymerase assays, cell culture systems, and animal models.

Antiviral activities of oral 1-O-hexadecylpropanediol-3-phosphoacyclovir and acyclovir in woodchucks with chronic woodchuck hepatitis virus infection

Acyclovir triphosphate is a potent inhibitor of hepatitis B virus DNA polymerase, but acyclovir treatment provides no benefit in patients with hepatitis B virus infection. This is due in part to the fact that hepatitis B virus, unlike herpes simplex virus, does not code for a viral thymidine kinase which catalyzes the initial phosphorylation of acyclovir. We synthesized 1-O-octadecyl-sn-glycero-3-phospho (3-P)-acyclovir and found that it was highly active in reducing hepatitis B virus replication in 2.2. 15 cells, while acyclovir was inactive. The greater antiviral activity of 1-O-octadecyl-sn-glycero-3-P-acyclovir appeared to be due to liver cell metabolism of the compound to acyclovir monophosphate (K. Y. Hostetler et al., Biochem. Pharmacol. 53:1815-1822, 1997). However, a closely related compound without a hydroxyl group at the sn-2 position of glycerol, 1-O-hexadecylpropanediol-3-P-acyclovir, was more active and selective in 2.2.15 cells in vitro. In this study, we treated woodchucks chronically infected with woodchuck hepatitis virus with increasing oral doses of 1-O-hexadecylpropanediol-3-P-acyclovir and assessed the response to therapy versus acyclovir or a placebo. At a dosage of 10 mg/kg of body weight twice a day, the test compound significantly inhibited viral replication in vivo, as indicated by a 95% reduction in serum woodchuck hepatitis virus DNA levels and by a 54% reduction in levels of woodchuck hepatitis virus replicative intermediates in the liver. Higher doses were somewhat less effective. In contrast, 20 mg of acyclovir/kg twice daily, a 5. 3-fold-higher molar dosage, had no demonstrable activity against woodchuck hepatitis virus. Oral 1-O-hexadecylpropanediol-3-P-acyclovir appeared to be safe and effective in chronic woodchuck hepatitis virus infection.

Interferon alfa for chronic hepatitis B infection: increased efficacy of prolonged treatment. The European Concerted Action on Viral Hepatitis (EUROHEP)

Interferon alfa (IFN-alpha) is the primary treatment for chronic hepatitis B. The standard duration of IFN-alpha therapy is considered 16 weeks; however, the optimal treatment length is still poorly defined. We evaluated the efficacy and acceptability of prolonged IFN-alpha treatment in patients with chronic hepatitis B. To investigate whether treatment prolongation could enhance the rate of hepatitis B e antigen (HBeAg) seroconversion, we conducted a prospective, controlled, multicenter trial in which all patients were treated with a standard regimen of 10 million units IFN-alpha 3 times per week over 16 weeks. Patients who were still HBeAg-positive after 16 weeks of therapy were randomized to prolongation of the identical regimen up to 32 weeks (prolonged therapy) or discontinuation of treatment (standard therapy). Among the 162 patients who entered the study, 27 (17%) were HBeAg-negative after the first 16 weeks of treatment, and 118 were randomized to standard or prolonged therapy. After randomization, a response (HBeAg seroconversion and sustained hepatitis B virus [HBV]-DNA negativity) was observed in 7 of the 57 (12%) patients assigned to standard therapy versus 17 of the 61 (28%) patients assigned to prolonged therapy (P =.04). A low level of viral replication after 16 weeks of treatment, as indicated by serum HBV-DNA values under 10 pg/mL, was found to be the only independent predictor of response (52% vs. 0%; P <.001) during prolonged therapy. The prolonged IFN-alpha schedule was well tolerated in the large majority of patients. In chronic hepatitis B, prolongation of IFN-alpha therapy up to 32 weeks is superior to a standard course of 16 weeks. Those patients who exhibit a low level of viral replication at the end of the standard regimen benefit most from prolonged treatment.

The S-acyl-2-thioethyl pronucleotide approach applied to acyclovir: part I. Synthesis and in vitro anti-hepatitis B virus activity of bis(S-acyl-2-thioethyl)phosphotriester derivatives of acyclovir

The synthesis and in vitro anti-hepatitis B virus (HBV) activity of two mononucleoside phosphotriester derivatives of acyclovir incorporating S-acyl-2-thioethyl (SATE) groups are reported. In contrast to the parent nucleoside, the described phosphotriesters emerged as potent and selective inhibitors of HBV replication in HepG2.2.15 cells. This result can be attributed to the unique cellular metabolism of the SATE pronucleotides giving rise to the delivery to acyclovir 5'-monophosphate inside the infected cells. Moreover, the in vitro anti-HBV activities of one of these bis(SATE)phosphotriesters and of (-)-beta-L-2',3'-dideoxy-3'-thiacytidine (lamivudine, 3TC) were compared alone and in combination. Analysis of the combination data indicates that 3TC and the studied SATE pronucleotide of acyclovir exhibited strong synergistic interactions. The present study provides an example where the use of a pronucleotide approach extends the antiviral spectrum of a nucleoside analogue. Given the potency of SATE pronucleotides of acyclovir against HBV in HepG2.2.15 cells, further studies including animal experiments seem warranted to evaluate the potential of these compounds as anti-HBV agents.

Advances in the treatment of chronic hepatitis B virus infection

Recent advances in our understanding of the replicative mechanism of HBV, and the development of potent nucleoside analogues as clinically effective inhibitors of the HIV reverse transcriptase or herpesvirus polymerases has opened a new era in the treatment of chronic HBV infection. Single agent therapies, such as famciclovir, lamivudine or lobucavir, have had some success. There is now a logical basis for combination therapy, because of the clear need for prolonged treatment and the associated possibility that drug resistant strains will emerge with monotherapy, but the choice of agents to combine and the regimens in which they should be employed remain uncertain.Copyright 1998 John Wiley & Sons, Ltd.

The identification and development of antiviral agents for the treatment of chronic hepatitis B virus infection

Hepatitis B virus (HBV) is the leading cause of chronic hepatitis throughout the world. Notwithstanding the availability of a safe and effective vaccine, the world prevalence of HBV has not declined significantly, thus resulting in the need for a selective antiviral agent. HBV is a small, partially double-stranded DNA virus which replicates through an RNA intermediate. Most efforts to develop anti-HBV agents have been targeted to the viral DNA polymerase which possesses reverse transcriptase activity. Currently, the most promising anti-HBV agents are nucleoside analogs which interfere with viral DNA replication. Although earlier nucleoside analogs such as vidarabine (ara-A) and fialuridine (FIAU) have displayed unacceptable toxicities, newer analogs such as lamivudine (3TC), bis-POM PMEA (GS-840), lobucavir, and BMS-200,475 have demonstrated clinical utility. In particular, the use of lamivudine has generated considerable interest in the development of other L-enantiomeric nucleoside analogs for use against HBV. Here, we provide an overview of HBV structure and replication strategy and discuss the use of cell culture systems, in vitro viral polymerase systems, and animal models to identify and evaluate anti-HBV agents. We also discuss the various classes of nucleoside analogs in terms of structure, mechanism of action, status in clinical development, ability to select for resistant HBV variants, and use in combination therapies. Finally, we present a discussion of novel antiviral approaches, including antisense and gene therapy, and address the various challenges to successful anti-HBV chemotherapeutic intervention.

Combination alpha-interferon and lamivudine therapy for alpha-interferon-resistant chronic hepatitis B infection: results of a pilot study

BACKGROUND/AIMS

Alpha-interferon achieves seroconversion in about one third of naive patients. Attempts to achieve seroconversion in patients who have previously failed alpha-interferon have proved disappointing. Combination chemotherapy (alpha-interferon with a nucleoside analogue) might provide a treatment alternative for these patients. We have undertaken a phase 2 study in 20 patients who had previously failed at least one course of alpha-interferon. The study was designed to assess the safety, tolerability and efficacy of the combination.

METHODS

All patients were treated for 16 weeks with alpha-interferon in combination with 12 or 16 weeks of Lamivudine (3'TC). Patients were followed for 16 weeks post-treatment. Pharmacokinetic studies were performed to identify/exclude significant pharmacokinetic drug interaction.

RESULTS

The combination was well tolerated, and side-effects of the combination were indistinguishable from the recognised side-effects of alpha-interferon. Pharmacokinetic studies performed on days 1 and 29 did not show any significant interaction. All patients achieved HBV DNA clearance during treatment, but 19 relapsed at the end of treatment. HBeAg/anti-HBe seroconversion was observed for four patients, but was sustained for a single patient (who also had sustained DNA clearance).

CONCLUSIONS

Combination therapy with alpha-interferon and lamivudine given for 16 weeks appears safe and is well tolerated. However, for this group of patients who had previously failed interferon monotherapy, the efficacy of combination interferon/lamivudine therapy appears disappointing, and other treatment strategies should be investigated.

Current status of anti-HBV chemotherapy

In the past decade, significant progress has been achieved in the battle against hepatitis B virus. In addition to the immunomodulating agents such as interferon-alpha and thymosin, many novel antiviral agents have been discovered, among which nucleoside analogues are the mainstay. New-generation compounds such as 3TC and famciclovir have shown promise in the treatment of patients chronically infected by this virus, and are on the line for approval. However, viral rebound after cessation of therapy still remains a major problem. Additionally, the reports on the drug resistance to these antiviral agents suggest that combination therapy will be the eventual strategy (Bartholomew et al., 1997; Tipples et al., 1996). Therefore, developments of safe and effective antiviral agents which do not cross-resist with currently available antiviral drugs are still much needed.

Enhanced oral absorption and antiviral activity of 1-O-octadecyl-sn-glycero-3-phospho-acyclovir and related compounds in hepatitis B virus infection, in vitro

Acyclovir (ACV) triphosphate and azidothymidine (AZT) triphosphate inhibit the DNA polymerase of human hepatitis B virus (HBV) by 50% at submicromolar concentrations, but no effects of ACV or AZT treatment have been noted on the clinical manifestations of hepatitis B. We synthesized 1-O-octadecyl-sn-glycero-3-phospho-acyclovir (ODG-P-ACV), 1-O-hexadecylpropanediol-3-phospho-acyclovir (HDP-P-ACV), and 1-O-octadecyl-sn-glycero-3-phospho-azidothymidine (ODG-P-AZT), and evaluated their antiviral activity in human hepatoma cells that constitutively produce HBV (2.2.15 cells). ACV and AZT up to 100 microM caused only slight inhibition of HBV replication in 2.2.15 cells. However, HDP-P-ACV and ODG-P-ACV inhibited viral replication by 50% at 0.5 and 6.8 microM, respectively. ODG-P-AZT also showed increased antiviral activity, with a 50% reduction in HBV replication at 2.1 microM. Based on the EC50, HDP-P-ACV, ODG-P-ACV, and ODG-P-AZT were > 200, > 14.7, and > 48 times more active than their free nucleosides in reducing HBV replication in 2.2.15 cells. To evaluate the biochemical basis for the increased antiviral activity, we studied the uptake and metabolism of 1-O-octadecyl-sn-glycero-3-phospho-[3H]acyclovir (ODG-P-[3H]ACV) in HepG2 cells. Cellular uptake of ODG-P-[3H]ACV was found to be substantially greater than that of [3H]ACV, and cellular levels of ACV-mono-, -di-, and -triphosphate were much higher with ODG-P-ACV. ODG-P-[3H]ACV was well absorbed orally. Based on urinary recovery of tritium after oral or parenteral administration of the radiolabeled compounds, oral absorption of ODG-P-ACV in mice was 100% versus 37% for ACV. ODG-P-ACV plasma area under the curve was more than 7-fold greater than that of ACV. Lipid prodrugs of this type may be useful orally in treating viral diseases.

New therapies for chronic hepatitis B

Currently, the only therapy of proven benefit in chronic hepatitis B is interferon-alpha which leads to a long-term benefit in only one-third of patients. New therapies for hepatitis B fall into three categories; antiviral chemotherapy, immunomodulation with cell-based therapies, vaccines or cytokines, and gene therapy such as with antisense oligonucleotides, ribozymes or viral mutants. The most promising immediate approach to therapy is with the new nucleoside antivirals--lamivudine and famciclovir. These drugs are well absorbed orally, result in profound inhibition of circulating hepatitis B virus, and, in some cases, loss of hepatitis B e antigen and improvement in serum aminotransferases. Controlled trials of long-term famciclovir and lamivudine therapy currently underway aim to show whether these drugs are safe and can provide sustained inhibition of viral replication and attentant improvement in liver disease.

Long-term effects of interferon-alpha in five HIV-positive patients with chronic hepatitis B

Chronic hepatitis B viral infection is common in human immunodeficiency virus (HIV) carriers, but the effectiveness of interferon therapy is still unknown. We report the results of a long-term pilot study of five patients, who were infected with HIV and chronic hepatitis B, treated by interferon. Five males co-infected with HIV and hepatitis B virus (HBV) (mean age 27 years) were given a 6-month course of interferon (IFN)-alpha 2b 5 million units (MU) three times weekly. On initiating the treatment, their CD4 lymphocyte count was 340-553 mm-3, their CDC stage was IIa-III; all had histologically proven chronic hepatitis, with Knodell's score ranging from 6-10, and active HBV replication (HBV DNA and hepatitis B e antigen (HBeAg) were detectable). There was no associated hepatitis delta virus (H delta V) or hepatitis C virus (HCV) infection. Follow-up was for 53 months on average (24-74 months). After the treatment, hepatitis B e antibody (HBeAb) and hepatitis B s antibody (HBsAb) seroconversion was observed in one patient, HBeAb seroconversion alone in two patients, HBV DNA was absent from serum in three patients, and HBV DNA significantly decreased in one patient. The serum alanine aminotransferase (ALT) activity was normal in four patients. Histological improvement was obtained in four patients. The HIV stage remained unchanged in all patients during the whole follow-up. These preliminary results suggest that interferon can be successfully used in immunocompetent HIV carriers with chronic hepatitis B as well as in HIV-negative patients.

Famciclovir treatment of hepatitis B virus recurrence after liver transplantation: a pilot study

Despite hepatitis B immunoprophylaxis hepatitis B virus (HBV) recurrence is a frequent and often fatal complication after orthotopic liver transplantation (OLT). The purine nucleoside analogues penciclovir and its oral form famciclovir (FCV) proved to be well tolerated and effective against herpes simplex and zoster virus infections. In addition, an effective reduction of duck and human HBV replication was observed. Therefore, we conducted an uncontrolled pilot study of famciclovir in patients with HBV recurrence after OLT. Twelve patients have received famciclovir for at least 3 months in an open compassionate-use protocol. FCV was administered orally 500 mg three times a day for all patients (except one patient who was started on 750 mg three times a day for the first 2 weeks). Immediately after starting famciclovir, serum HBV DNA levels declined in 9 of 12 patients (75%) with a mean reduction from baseline levels of 80% after 3 months, 90% after 6 months, and > 95% after 12 months of treatment. With continued treatment, 5 of these 9 patients became negative by conventional hybridization assay, and in one of these HBV DNA became undetectable by polymerase chain reaction (PCR) 28 weeks after the start of treatment. Three patients showed no (sustained) reduction in HBV DNA after at least 3 months of treatment; therefore, FCV was stopped. Latest serum alanine aminotransferase (ALT) levels decreased in 6 of 12 patients (50%) with a median decrease of 80% (range, 40%-95%) in comparison to pretreatment ALT values. ALT levels normalized in 4 patients (33%). One patient died due to sepsis and peritonitis in week 13 of treatment. This event was not related to FCV. No clinically significant side effects were noticed in any patient. The oral nucleoside analog famciclovir reduces HBV replication and transaminase levels in patients with HBV recurrence after liver transplantation. Because long-term FCV treatment is well tolerated, famciclovir appears to be a promising antiviral strategy in the treatment of HBV in immunocompromised patients.

New developments in antiviral therapy for chronic hepatitis B infection

The standard treatment of an HBeAg-positive, HBV-DNA-positive chronic hepatitis B patient is a 16-week course of 10 MU alpha-interferon thrice weekly. However, the overall therapeutic effect, as measured by disappearance of the HBe-antigen, is estimated at 30%. Improvement is possible by better selection of the patient, modifications in the treatment schedule, or combination therapy. In the selection of possible candidates for combination therapy, the second generation nucleoside analogues with activity against hepatitis B are good candidates. In clinical studies, lamivudine and famciclovir are used, both of which can reduce serum HBV-DNA to levels below 1 pg/ml within weeks. The ongoing clinical studies address the efficacy and safety of these drugs after prolonged exposure, in combination with alpha-interferon and around liver transplantation in patients with decompensated liver disease.

The value of quantitative measurement of HBeAg and HBsAg before interferon-alpha treatment of chronic hepatitis B in children

Serum concentrations of HBsAg, HBeAg and hepatitis B virus DNA were measured quantitatively before interferon treatment in 23 children (17 boys, 6 girls) suffering from chronic hepatitis B, and correlated to the outcome of the treatment. Five children remained HBsAg- and HBeAg-positive throughout the treatment and 6 months after the end of the treatment (non-responders), 12 children eliminated HBeAg but not HBsAg (partial responders) and six eliminated HBeAg and HBsAg (complete responders). The five non-responders had significantly higher initial HBsAg and HBeAg concentrations and significantly lower alanine aminotransferase levels than the partial or complete responders. The six complete responders had significantly lower HBsAg concentrations than the partial or non-responders, and seemed to be younger. No significant difference in HBV DNA levels was found in the three response groups. These data suggest that quantitative assays of HBsAg and HBeAg are particularly useful in selecting patients with chronic hepatitis B for interferon therapy.

Treatment of chronic hepatitis B

Chronic infection with the hepatitis B virus (HBV) is a major cause of worldwide morbidity and mortality. A large number of therapeutic approaches has been tried, including interferon (IFN), nucleoside analogues and immunomodulators. To date controlled clinical trials have shown that only IFN is of long-term value but many patients fail to respond to treatment. New approaches to treating patients with IFN-resistant hepatitis B are currently undergoing clinical and experimental evaluation, and it seems likely that new therapeutic agents will be available in the near future.

A randomized controlled trial of thymopentin therapy in patients with chronic hepatitis B

Strategies of treatment of chronic hepatitis type B are currently based on the use of either antiviral or immunomodulatory agents. A randomized, controlled trial was performed to assess the safety and efficacy of 6-month thymopentin therapy in 30 patients with chronic hepatitis B. Inclusion criteria were biopsy-proven chronic hepatitis, elevated alanine aminotransferase and serum HBsAg and HBV-DNA positivity for at least 12 months. At the conclusion of the study (1 year), HBV-DNA was negative and alanine aminotransferase had normalized in 13% and 20% of treated cases and in 20% and 27% of controls. None of the ten treated and one of the nine control patients who were initially HBeAg positive subsequently cleared HBeAg. None became HBsAg negative. A histologic improvement was noted in 27% of the treated patients compared with 18% of controls. These results indicate that this regimen of thymopentin therapy is not effective in treating chronic hepatitis B.

Treatment of chronic viral hepatitis

Recent advances have been made in the treatment of chronic viral hepatitis, mainly with recombinant interferon (IFN) alpha. However, the present treatment of chronic viral hepatitis is not entirely satisfactory because the efficacy is inconstant and/or incomplete. In chronic hepatitis B IFN-alpha induces a sustained interruption of hepatitis B virus (HBV) replication, with a HBeAg to anti-HBe seroconversion in about 30% of patients. Patients most likely to respond are those with no immunosuppression, HBV infection acquired during adulthood or active liver disease with low HBV replication. Responders usually show a significant decrease in serum HBV DNA levels during the first 2 months of therapy, followed by a significant increase in the level of aminotransferases. New nucleoside analogues might be useful in combination with IFN-alpha in the treatment of those who do not respond to IFN therapy. In chronic hepatitis B-D, the rate of sustained response to IFN-alpha therapy is low. To be effective, IFN-alpha must be used at a high dosage (9-10 mega units) with a long duration (1 year). In chronic hepatitis C, IFN-alpha at a dosage of 3 mega units over 6 months, induces a sustained response in about 20% of patients. A higher dosage of IFN (5-10 mega units) and a longer duration of treatment increases the rate of sustained response but is associated with poor tolerance. Non-responders to a first course of IFN do not respond to a second course of treatment. In patients who respond but relapse after treatment, the rate of sustained response after a second course of IFN needs to be assessed. Ribavirin, which has a significant antiviral effect on hepatitis C virus, might be useful in combination with IFN-alpha. At the dosage (3-6 mega units) usually used, IFN-alpha is relatively well tolerated. In about 10% of the patients therapy is interrupted, mainly because of severe fatigue, thyroid dysfunction or depression.

Treatment of chronic hepatitis B with recombinant interferon alpha versus recombinant interferon alpha plus levamisole

To compare the efficacy and tolerance of the simultaneous administration of levamisole plus IFN versus treatment with IFN alone in chronic hepatitis B, 39 patients were randomly assigned into two groups. Nineteen patients received 15 million units of recombinant alpha interferon 2b (rIFN-alpha 2b) 3 times a week for 4 months. The other 20 patients were treated with the same dose and schedule of rIFN-alpha 2b and 150 mg of levamisole simultaneously given during the first 6 weeks of treatment. At the end of the study (thirteenth month), serum HBV-DNA was negative in 59% of patients treated with interferon alone and in 37% of those treated with interferon and levamisole. HBeAg was negative in a similar percentage in the two groups (41% vs. 37%). Serum alanine aminotransferase levels decreased in patients who lost viral DNA. These data demonstrate that the combination of alpha interferon and levamisole, at the doses and under the schedule used in this study, does not achieve better results than the treatment with alpha interferon alone. Although tolerance to the simultaneous administration of alpha interferon and levamisole is good, secondary effects may be hazardous.

Inhibitory effect of 9-(2-phosphonylmethoxyethyl)-adenine (PMEA) on human and duck hepatitis B virus infection

9-(2-Phosphonylmethoxyethyl)adenine (PMEA) was evaluated for its inhibitory effect on hepadnavirus replication in three different cell systems, i.e., human hepatoma cell lines HepG2 2.2.15 and HB611 (transfected with human hepatitis B virus (HBV)) and primary cultures of duck hepatocytes infected with duck hepatitis B virus (DHBV). PMEA inhibited HBV release from HepG2 2.2.15 cells and HB611 cells at a 50% inhibitory concentration (IC50) of 0.7 and 1.2 microM, respectively. Intracellular viral DNA synthesis was inhibited at concentrations equivalent to those required to inhibit virus release from the cells. DHBV secretion from duck hepatocytes was inhibited by PMEA at an IC50 of 0.2 microM. HBsAg secretion was inhibited by PMEA in a concentration-dependent manner in HB611 cells and DHBV-infected duck hepatocytes but not HepG2 2.2.15 cells. The 50% cytotoxic concentration, as measured by inhibition of [3H-methyl]deoxythymidine incorporation was 150 microM for the two human hepatoma cell lines and 40 microM for the duck hepatocyte cultures. In a pilot experiment PMEA was found to reduce the amounts of DHBV DNA in the serum of Pekin ducks.

Repeated courses of alpha-interferon for treatment of chronic hepatitis type B

In chronic hepatitis B transition from active replication to viral latency (HBeAg seroconversion) usually leads to remission of the disease. alpha-Interferon (IFN) therapy induces HBeAg seroconversion in about one-third of the patients, thus leaving the majority of patients with persistent disease. Eighteen chronic hepatitis B patients who did not respond (HBeAg seroconversion and clearance of HBV-DNA) to an initial 16-week course of IFN subsequently received IFN again after at least 6 months of no therapy. The repeated therapy consisted of 1.5-5 MU lymphoblastoid IFN daily for 16 weeks. Treatment effects were monitored by quantitative measurement of HBeAg and HBV-DNA. To analyze whether the results were related to patient characteristics known to affect the response to initial treatment, a predicted response rate, based on pre-treatment factors, was determined. After a follow-up of 52 weeks, 2 of the 18 patients (11%) had responded to therapy. Two additional patients became HBV-DNA-negative with sustained HBeAg positivity. All patients remained HBsAg-positive. According to the pre-treatment parameters, a response was predicted for 9 of the 18 patients (50%). This predicted response rate was significantly higher than the actual response rate (p = 0.03). In conclusion, this pilot study with moderate dosages of IFN suggests that the HBeAg seroconversion rate after repeated IFN treatment is low for previous non-responders and probably is not related to important clinical characteristics that influence the response to initial IFN treatment. A large controlled trial with higher doses of IFN is desirable to further evaluate the benefits of retreatment.

Antiviral effect of prolonged intermittent lymphoblastoid alpha interferon treatment in chronic hepatitis B

In a European multicentre study 40 patients with HBeAg positive chronic hepatitis B virus (HBV) infection were treated with 5 mega units of lymphoblastoid alpha-interferon daily according to the following regimen: a four week primer course, four weeks of rest and a second course lasting 16 to 30 weeks. After 52 weeks of follow up, a response (HBeAg seroconversion and HBV-DNA negativity) was observed in 22 patients (55%). HBsAg seroconversion occurred in five patients (12.5%). One patient exhibited a relapse for serum HBeAg and HBV-DNA after cessation of treatment. According to a response prediction model, the observed response rate was not related to the selection of patients likely to respond. The initial interferon course induced a reduction of the serum HBV-DNA and HBeAg levels of 87% and 18%, respectively, leading to a significantly lower level of viral replication activity at the start of the second longterm course compared with baseline. After 24 weeks of follow up (week 16 of the second course), 19 (48%) patients exhibited a response, 13 (32%) a partial response (HBeAg < 50% of initial level or HBV-DNA negative) and 8 (20%) no response. For eight of the 13 partial responders treatment was stopped at week 24 and viral replication rebounded to pretreatment values. In the last five partial responders prolongation of therapy up to week 38 led to a definite response and HBsAg seroconversion in three of the five patients. The results of this study suggest that a short primer course and prolongation of therapy may help to enhance the response rate of alpha-interferon therapy for chronic hepatitis type B.