Famciclovir: review of clinical efficacy and safety

Small Molecule Drugs Targeting Viral Polymerases

Small molecules that specifically target viral polymerases-crucial enzymes governing viral genome transcription and replication-play a pivotal role in combating viral infections. Presently, approved polymerase inhibitors cover nine human viruses, spanning both DNA and RNA viruses. This review provides a comprehensive analysis of these licensed drugs, encompassing nucleoside/nucleotide inhibitors (NIs), non-nucleoside inhibitors (NNIs), and mutagenic agents. For each compound, we describe the specific targeted virus and related polymerase enzyme, the mechanism of action, and the relevant bioactivity data. This wealth of information serves as a valuable resource for researchers actively engaged in antiviral drug discovery efforts, offering a complete overview of established strategies as well as insights for shaping the development of next-generation antiviral therapeutics.

Exploration of intramolecular charge transfer in para-substituted nitrobenzofurazan: Experimental and theoretical analyses

The present work aims at exploring the high electrophilic character of 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) toward the morpholine group by an S_NAr reaction in acetonitrile or water (thereafter referred to as NBD-Morph). The electron-donating ability of the morpholine causes intra-molecular charge transfer (ICT). In this report, we present a comprehensive study on the optical characteristics using UV-Vis, photoluminescence (cw-PL) and its time-resolved (TR-PL) to determine the properties of the emissive intramolecular charge transfer (ICT) in the NBD-Morph donor-acceptor system. An exhaustive theoretical investigation utilizing the density functional theory (DFT) and its extension TD-DFT methods is an essential complement of experiments to rationalize and understand the molecular structure and related properties. The findings from QTAIM, ELF, and RDG analyses establish that the bonding between morpholine and NBD moieties is of the electrostatic or hydrogen bond type. In addition, the Hirshfeld surfaces have been established to explore the types of interactions. Further, the non-linear optical (NLO) responses of the compound have been examined. The structure-property relationships obtained through the combined experimental and theoretical offer valuable insights for designing efficient NLO material.

Successful treatment with famciclovir for varicella zoster virus infection resistant to acyclovir

Varicella zoster virus (VZV) reactivates more frequently in immunocompromised patients than immunocompetent subjects and is a significant cause of morbidity and mortality. Acyclovir is frequently used for treatment against VZV reactivation. However, long-term use of acyclovir can result in the emergence of VZV strain resistant to acyclovir. Here, we report a 67-year-old man with adult T-cell leukemia who suffered from herpes zoster with acyclovir-resistant VZV after long-term prophylaxis. The isolated viruses from his skin lesions were a mixture of acyclovir-resistant and acyclovir-susceptible strains. Sequence analysis showed the presence of thymidine kinase (TK) mutations in the resistant clones. Interestingly, oral administration of famciclovir, a prodrug form of penciclovir, resulted in resolution of his herpes zoster, although most acyclovir-resistant strains of VZV were reported to be resistant to penciclovir. This implied that a certain amount of susceptible VZV with wild-type viral TK gene was present in vivo, and that famciclovir could be phosphorylated intracellularly by the intact viral kinases. As famciclovir is more potent and longer-acting than acyclovir, the susceptible strains might have suppressed the generation and proliferation of the resistant in vivo. Even when VZV is developing resistance to acyclovir, famciclovir might be effective at least in the early resistant phase.

Radiotherapy-induced reactivation of neurotrophic human herpes viruses: Overview and management

PURPOSE

Infection by Human Herpes Viruses (HHV) types 1-3, are prevalent throughout the world. It is known that radiotherapy can reactivate HHVs, but it is unclear how and to what extent reactivations can interact with or affect radiotherapeutic efficacy, patient outcomes and mortality risk. Herein, we aim to summarize what is known about Herpes Simplex Virus (HSV)-1,2 and Varicella Zoster Virus (VZV) pathophysiology as it relates to tumor biology, radiotherapy, chemo-radiotherapy, diagnosis and management so as to optimize cancer treatment in the setting of active HHV infection. Our secondary aim is to emphasize the need for further research to elucidate the potential adverse effects of active HHV infection in irradiated tumor tissue and to design optimal management strategies to incorporate into cancer management guidelines.

MATERIALS AND METHODS

The literature regarding herpetic infection, herpetic reactivation, and recurrence occurring during radiotherapy and that regarding treatment guidelines for herpetic infections are reviewed. We aim to provide the oncologist with a reference for the infectious dangers of herpetic reactivation in patients under their care and well established methods for prevention, diagnosis, and treatment of such infections. Pain management is also considered.

CONCLUSIONS

In the radiotherapeutic setting, serologic assays for HSV-1 and HSV-2 are feasible and can alert the clinician to patients at risk for viral reactivation. RT-PCR is specific in identifying the exact viral culprit and is the preferred diagnostic method to measure interventional efficacy. It can also differentiate between herpetic infection and radionecrosis. The MicroTrak^® HSV1/HSV2/VZV staining kit has high sensitivity and specificity in acute lesions, is also the most rapid means to confirm diagnosis. Herpetic reactivation and recurrences during radiotherapy can cause interruptions, cessations, or prolongations of the radiotherapeutic course, thus decreasing the biologically effective dose, to sub-therapeutic levels. Active HHV infection within the treatment volume results in increased tumor radio-resistance and potentially sub-therapeutic care if left untreated. Visceral reactivations may result in fatality and therefore, a high index of suspicion is important to identify these active infections. The fact that such infections may be mistaken for acute and/or late radiation effects, leading to less than optimal treatment decisions, makes knowledge of this problem even more relevant. To minimize the risk of these sequelae, prompt anti-viral therapy is recommended, lasting the course of radiotherapy.

Antiviral activity of PHA767491 against human herpes simplex virus in vitro and in vivo

BACKGROUND

Herpes simplex virus (HSV) is a common human pathogen that causes a variety of diseases, including oral-labial, genital lesions and life-threatening encephalitis. The antiviral nucleoside analogues such as acyclovir are currently used in anti-HSV therapies; however, clinical overuse of these drugs has led to the emergence of drug-resistant viral strains. Hence, there is an urgent need to develop new anti-HSV agents.

METHODS

To identify novel anti-HSV-1 compounds, we screened the LOPAC small scale library of 1280 bioactive compounds to identify inhibitors of HSV-1-induced necroptosis. Further experiments including western blot analysis, Q-PCR analysis and immunohistochemistry were performed to explore the antiviral mechanism of the compounds.

RESULTS

Here, we identified PHA767491 as a new inhibitor of HSV. PHA767491 potently blocked the proliferation of HSV in cells, as well as HSV induced cell death. Further, we found that PHA767491 strongly inhibited HSV infection post viral entry. Moreover, PHA767491 reduced the expression of viral genes required for DNA synthesis including UL30/42 DNA polymerase and UL5/8/52 helicase-primase complex. The essential immediate early (IE) genes such as ICP4 and ICP27 are critical for the expression of the early and late genes. Of note, PHA767491 inhibited the expression of all IE genes of both HSV-1 and HSV-2. Importantly, PHA767491 reduced viral titers in the tissues from the mice infected with HSV-1. Consistently, immunohistochemistry analysis showed that PHA767491 dramatically attenuated expression of viral protein gB in the livers.

CONCLUSIONS

Taken together, PHA767491 has potent anti-HSV activity by inhibiting viral replication both in vitro and in mouse model. Thus, PHA767491 could be a promising agent for the development of new anti-HSV therapy.

Rapid host immune response and viral dynamics in herpes simplex virus-2 infection

Herpes simplex virus-2 (HSV-2) is periodically shed throughout the human genital tract. Although a high viral load correlates with the development of genital ulcers, shedding also commonly occurs even when ulcers are absent, allowing for silent transmission during coitus and contributing to high seroprevalence of HSV-2 worldwide. Frequent viral reactivation occurs within ganglia despite diverse and complementary host and viral mechanisms that predispose toward latency, suggesting that viral replication may be constantly occurring in a small minority of neurons at these sites. Within genital mucosa, the in vivo expansion and clearance rates of HSV-2 are extremely rapid. Resident dendritic cells and memory HSV-2 specific T cells persist at prior sites of genital tract reactivation and, in conjunction with prompt innate recognition of infected cells, lead to rapid containment of infected cells. The fact that immune responses usually control viral replication in genital skin before lesions develop provides hope that enhancing such responses could lead to effective vaccines and immunotherapies.

Human herpes simplex virus infections: epidemiology, pathogenesis, symptomatology, diagnosis, and management

Eight of the more than 80 known herpesviruses are human pathogens. Human herpes simplex virus (HSV) is a contagious infection with a large reservoir in the general population. It has a potential for significant complications in the immunocompromised host. In addition, psychological distress caused by the negative stigma associated with genital herpes and visible facial lesions in those experiencing frequent outbreaks renders it a challenging clinical dilemma. This article reviews the epidemiology, pathogenesis, and diagnostic features of HSV infections, providing the clinician with an up-to-date understanding of the available management strategies for mucocutaneous HSV-induced disease.

Infecciones en los pacientes trasplantados de hígado

Infection is the main cause of morbidity and mortality in liver transplant patients. Infections appear in three different periods following transplantation and are related to surgical factors, the degree of immunosuppression, environmental exposure and the type of prophylaxis used. Bacterial infections occur in the first two months after transplantation as bacteremia, surgical wound and intra-abdominal infection, or pneumonia. Tuberculosis in the liver transplant recipient is more aggressive than in immunocompetent persons. Viruses produce direct infection in these patients; moreover, some viruses (e.g., cytomegalovirus and human herpes virus 6) are immunomodulators and can facilitate other infections and graft rejection. Polymerase chain reaction and antigenemia techniques have made possible prompt diagnosis of cytomegalovirus infection and the implementation of prophylactic strategies. Fungal infections still have a high associated mortality rate, despite new diagnostic techniques and new antifungal drugs.

A review of sympathetically maintained pain syndromes in the cancer pain population: the spectrum of ambiguous entities of RSD, CRPS, SMP and other pain states related to the sympathetic nervous system

Accepted wisdom contends that sympathetically maintained pain is rare in cancer pain syndromes. But this may be more of an artifact of how we diagnose this condition than a reflection of its true prevalence. One area in which one might suspect this to be true is in postsurgical states. While there are case reports of sympathetically maintained pain occurring after radical neck dissection, orbital and maxillary exenteration, it has not been reported in the more common areas of postsurgical pain. For instance, although one should suspect that the nerve damage that accompanies post-thoracotomy and postmastectomy pain syndromes would bring into being a certain incidence of sympathetically maintained pain, it is difficult to find collaborative reports. This may have more to do with the difficulty inherent in diagnosing sympathetically maintained pain than its actual contribution to these persistent cancer pain syndromes. The reason that it is more commonly reported in limb amputation is less comprehensible since blocking the sympathetic fibers that travel to an extremity is easier than those going to the thoracic cavity. In addition to surgically induced sympathetically maintained pain, medical patients with lymphoma and leukemia may have an element of sympathetically maintained pain when they develop postherpetic neuralgia. While the contribution of sympathetically maintained pain in these cases is not totally ignored, its involvement, as in the surgical patients mentioned above, is worthy of another analysis. This paper will discuss the topics introduced above and suggest diagnostic and therapeutic options available for this condition.

Prenylation of HDAg and antiviral drug development

Hepatitis delta virus (HDV) is an important cause of acute and chronic liver disease. Current medical therapies are unable to effectively eradicate HDV infections. Research into the molecular virology of the HDV life cycle has revealed a fascinating collection of biology. These insights are now beginning to be translated into new potential treatment strategies. For example, an essential step in the virus assembly process involves the post-translational lipid modification of a specific HDV protein, namely prenylation of large delta antigen. Preventing prenylation abolishes virus particle formation. Drugs capable of specifically inhibiting prenylation have been developed for use in humans. These agents represent a new class of antiviral agents, with HDV as a first target. Here, a brief review of the HDV life cycle emphasizing the role of prenylation is presented along with implications for drug development and therapy.

New antiviral agents

During the last three decades, a better understanding of viral replication and disease states caused by viral infections have led to the development of newer antiviral agents with enhanced activity and better tolerability. This review focuses on newer systemic and topical antiviral agents that are used in treatment of herpes viruses including herpes simplex type-1 (HSV-1) and type-2 (HSV-2), varicella-zoster virus (VZV) and cytomegalovirus CMV) as well as the human papilloma virus (HPV). Included in this article are the agents famciclovir, penciclovir, valganciclovir, imiquimod, docosanole and brivudin.

Viral and fungal infections after liver transplantation--part II

Viral and fungal infections in liver transplant recipients are important to recognize and treat early because of their association with substantial morbidity and mortality. Some viruses, such as cytomegalovirus and human herpesvirus 6, have immunomodulatory properties and can facilitate other infections, including fungal infections. Cytomegalovirus has long been recognized as an important virus in transplantation, but in the past decade other viruses have also received attention in the medical literature because of their association with particular clinical syndromes. Although human herpesvirus 6 has been associated with fever, rash, and encephalitis, a direct cause-and-effect relationship is still lacking. Human herpesvirus 8 has been found to be the cause of Kaposi sarcoma. Molecular techniques (e.g., pp65 antigenemia and polymerase chain reaction) that have been introduced for routine diagnosis of viruses have facilitated the diagnosis of asymptomatic viral infections and the institution of preemptive therapy. Nonetheless, the diagnosis of invasive fungal infections in liver transplant recipients is often delayed and thus associated with high mortality. Despite the use of new antifungal agents in clinical practice and the reduced incidence of fungal infections because of antifungal prophylaxis regimens, mortality has not decreased. Future patient outcomes may improve with early identification of patients who have risk factors for invasive fungal infections and with the development of new molecular diagnostic techniques for early detection.

Synthesis of cationic beta-vinyl substituted meso-tetraphenylporphyrins and their in vitro activity against herpes simplex virus type 1

An easy route to cationic beta-vinyl substituted meso-tetraphenylporphyrin derivatives is described. Two novel compounds were tested in vitro for their antiviral photoactivity against herpes simplex virus type 1. One of these compounds exhibited a significant activity, reaching 99% of virus inactivation after 15 min of photoactivation.

Treatment of herpes simplex virus infections

Herpes simplex virus (HSV) types 1 and 2 are ubiquitous organisms that cause infections in human populations throughout the world. The clinical manifestations of HSV infections are varied, ranging from asymptomatic disease to life-threatening illness in neonates and immunocompromised hosts. This article will review the common presentations for HSV disease and the current recommendations for the treatment of these infections. A detailed summary of the antiviral drugs used to treat HSV infections is also presented.

Changing paradigms in dermatology: antivirals in dermatology

Almost all of the approved antiviral drugs have become available during the past two decades. Approximately one half of these agents are for the treatment of human immunodeficiency virus (HIV) infections and comprise five classes. The first three classes all act to inhibit reverse transcriptase: nucleoside analogs; nonnucleoside analogs; and nucleotide analogs. The fourth class, protease inhibitors, prevent viral packaging; the fifth class, fusion inhibitors, prevent fusion between HIV and the target cell. Four nucleoside analogs, acyclovir, valacyclovir, famciclovir and penciclovir, are approved for the therapy of herpes simplex and varicella zoster infections. Interferon alpha is approved in the injectable form for condyloma acuminatum and Kaposi's sarcoma, but the more efficient method of delivering this agent is via interferon induction following topical use of imiquimod cream. Antiviral agents are also approved for infections with cytomegalovirus, hepatitis B and C, respiratory syncytial virus, and influenza viruses. Most of these antiviral drugs are virastatic and not viracidal. Vaccines and public health measures are much more effective and cost effective than antiviral drugs and must be promoted accordingly in the defense against viral infections.

[Dual infection with hepatitis B and C. Spontaneous course and response to virostatic therapy in children following neoplastic diseases]

Combined chronic hepatitis B and C is a long-term complication in children surviving malignancy. We report on seven children who acquired hepatitis B as well as C virus infection during treatment for different malignancies. Four patients showed a spontaneous HBe Ag/anti-HBe seroconversion, two patients spontaneous clearance of hepatitis C virus, and one patient showed both HBe Ag/anti-HBe seroconversion and clearance of hepatitis C virus. One patient developed HBe Ag/anti-HBe seroconversion after antiviral interferon monotherapy and another patient after combination therapy with interferon/famcyclovir. Three patients developed complete sustained response of hepatitis C to a combined virostatic therapy with interferon and ribavirin. A total of 4 of 7 patients had a clearance of both infections and 3 of 7 patients had a clearance of at least one infection.

CONCLUSION

Our data in long-term survivors of childhood cancer with combined hepatitis B and C showed a remarkably high rate of spontaneous cure and a favourable response to antiviral therapy.

Serological and molecular response on combined antiviral treatment in children with chronic hepatitis B after pediatric malignancy

BACKGROUND

Chronic hepatitis B is a serious long-term problem for children surviving malignancy. The annual rate of spontaneous clearance of hepatitis B e antigen (HBeAg) is only 3% in these patients, and the response to monotherapy with interferon (IFN)-alpha is also low.

OBJECTIVE

To monitor the serological and molecular response on combined antiviral treatment in children with chronic hepatitis B after pediatric malignancy.

STUDY DESIGN

Twelve patients with a history of childhood malignancy and chronic hepatitis B were treated with prednisone for 4 weeks (0.6 mg/kg body weight per day orally for 3 weeks followed by 0.3 mg/kg body weight per day for 1 week) followed by IFN-alpha-2a (5 megaunits/m(2) body surface area, three times a week, subcutaneously) at least for 1 year. After 1 year of IFN-alpha monotherapy, treatment was discontinued in patients with HBeAg seroconversion as well as patients without HBeAg seroconversion and a decrease of serum hepatitis B virus (HBV) DNA level less than 0.5 logs of the basal level. Patients who had a decrease of the serum HBV DNA of more than 0.5 logs of the basal level underwent treatment continuation with IFN-alpha combined with famciclovir (FAM) (20 mg/kg body weight per day orally) for another year.

RESULTS

After 1 year of IFN-alpha monotherapy, a decrease of the serum HBV DNA level to less than 0.5 logs was found in eight of 12 patients. Two of them additionally developed HBeAg seroconversion after 3 and 12 months. The remaining six patients received antiviral treatment with IFN-alpha combined with FAM for another year. Two of them showed HBeAg seroconversion after 21 and 24 months from study entry. HBeAg seroconversion was only observed in patients who had a decrease of serum HBV DNA to levels below 1 x 10(6) copies/ml. Treatment-induced toxicity was moderate and reversible in all patients.

CONCLUSION

Combination treatment of chronic hepatitis B with prednisone, IFN-alpha, and FAM seems to be a safe and effective treatment option for children surviving pediatric malignancy.

Tolerability of treatments for viral hepatitis

Interferon-alpha is the most widely used antiviral drug in chronic hepatitis B and C. Tolerability is usually good and serious adverse effects are rare. Most of the adverse effects are mild or transient and do not necessitate drug withdrawal. More than 90% of patients who are given interferon-alpha achieve 6 months to 1 year of treatment without serious adverse effects. The serious adverse effects usually occur in predisposed patients with pre-existing organ dysfunction. Nevertheless, careful selection of patients for therapy and observation during therapy are recommended. Nucleoside analogues are promising drugs in the treatment of chronic hepatitis B through inhibition of viral DNA polymerase. Lamivudine has been licensed for use in this indication. Its tolerability is excellent even when used for periods of 1 year or more. The main concern is the relatively high incidence of viral resistance resulting in breakthrough during or relapse after therapy. In the treatment of chronic hepatitis C, ribavirin, in combination with interferon-alpha is currently the reference therapy. The main adverse effect is haemolytic anaemia, which necessitates careful monitoring and adjustment of dosage in many cases. Recently, large trials showed the better efficacy of pegylated interferons as compared with standard interferon. The combination of pegylated interferon with ribavirin is under evaluation.

Experimental studies on the antiviral agent famciclovir in Behçet's disease symptoms in ICR mice

BACKGROUND

Chronic oral aphthae, recurrent genital ulcers and uveitis are the three main manifestations of Behçet's disease (BD). The aetiopathogenesis of BD is still obscure, but herpes simplex virus (HSV) is one of the possible causal factors. Various kinds of drugs, including immunosuppressants and aciclovir have been used in treatment, but effectiveness is variable.

OBJECTIVES

To demonstrate the efficacy of famciclovir, an antiviral compound that acts against HSV, varicella-zoster virus and hepatitis B virus, in a murine model of BD.

METHODS

Using the HSV-induced BD mouse model, famciclovir was administered variously before and after inoculation or from the day of lesion occurrence, with appropriate controls. Ulceration of the mouth and genital skin and eye involvement were monitored. In addition, spleen cytokine expression was measured by polymerase chain reaction.

RESULTS

Pretreatment and concurrent treatment did not affect the occurrence of BD, but treatment from the appearance of lesions was effective in improving BD and preventing recurrence. After famciclovir, interleukin 2 expression correlated with the recurrence of BD symptoms.

CONCLUSIONS

This model suggests the possible role of immune response to viral infection in the development and activation of BD. The study provides a rationale for clinical trials of famciclovir in the human form of BD.

Current treatment practice of herpes zoster

The management of herpes zoster infection has been impacted by the development of oral and iv. antiviral therapies. There are clinical and historical features that help optimise the particular therapy course for a given patient. Additionally, there are common features of management in all patients with herpes zoster. In this review an understanding of the pathogenesis of herpes zoster is utilised as a starting point for the development of a rational approach to therapy. Clinical findings that impact decision making are emphasised and the appropriate goals for therapy are discussed.

Ganciclovir and penciclovir, but not acyclovir, induce apoptosis in herpes simplex virus thymidine kinase-transformed baby hamster kidney cells

The efficacies of ganciclovir (GCV), penciclovir (PCV) and acyclovir (ACV) in inducing cell death in the herpes simplex virus thymidine kinase (HSVTK) system were compared. HSVTK-transformed baby hamster kidney cells treated with GCV, PCV or ACV were monitored for growth by viable count, and for death by TUNEL assay, propidium iodide staining, detection of phosphatidyl serine translocation and detection of DNA laddering. All compounds delayed growth or reduced viability of HSVTK-transformed cells. Drug treatment reduced levels of cyclin B1 message (which normally peaks in G2/M-phase of the cell cycle) and induced a four- to fivefold upregulation of GADD45 message. Treatment with GCV or PCV induced rapid accumulation of cells in S-phase and apoptotic death. Treatment with ACV, however, was associated with sustained S-phase arrest. GCV (and to a lesser extent PCV) increased phosphatidyl serine translocation, induced positive TUNEL results with alterations in cell morphology, caused marked propidium iodide staining and induced DNA laddering. By contrast, up to 7 days' exposure to ACV did not induce DNA laddering, with very little TUNEL staining. ACV treatment had little effect on phosphatidyl serine translocation and propidium iodide staining was markedly reduced compared with treatment with the other compounds. Thus, by all criteria, GCV was the most potent inducer of cell death. The current theories regarding apoptosis or necrosis as the preferred form of cell death in prodrug gene therapy are considered and the suitability of PCV or ACV as potential alternatives to GCV in the HSVTK system is discussed.

Famciclovir treatment in transplant recipients with HBV-related liver disease: disappointing results

OBJECTIVE

Long-term administration of hepatitis B immune globulin is effective as prophylaxis for hepatitis B virus (HBV) reinfection but is limited by cost, side effects, availability and a failure rate of 20%. Famciclovir has been shown to be effective in the treatment of hepatitis B in the immunocompetent patient. Fewer data exist in the liver transplant setting, particularly regarding its efficacy in de novo HBV infection. The aims of this pilot study were to determine the effectiveness and safety of long-term administration of famciclovir in recurrent (n = 3) and de novo (n = 3) HBV infection after liver transplantation.

METHODS

Six patients with postransplant HBV infection (positivity of serum HBsAg and HBV DNA), four of whom were HBeAg positive, were treated with famciclovir (500 mg, 3 times a day) with a minimum follow-up period of 12 months. Biochemical, serological, virological (HBV DNA by hybridization assays and polymerase chain reaction), and histological (including HBV immunostaining) endpoints were evaluated.

RESULTS

None of the patients had a complete biochemical response, with a near complete normalization of ALT levels being observed in 3/6 patients. There was a lack of correlation between virological and biochemical responses. None of the patients seroconverted to anti-HBs or anti-HBe. A virological clearance was observed in only two patients, whereas a moderate reduction in HBV DNA levels was present in one. HBV DNA levels were higher than levels during pretreatment in the three remaining patients. Histological improvement was only observed in one patient.

CONCLUSION

Famciclovir alone appears of limited efficacy in the treatment of HBV infection after liver transplantation.

Famciclovir in chronic hepatitis B: results of a dose-finding study

BACKGROUND/AIMS

Famciclovir, an orally available nucleoside analogue with potent in vitro activity against HBV, is being investigated for treatment of chronic hepatitis B.

METHODS

A dose-finding study was conducted in patients with hepatitis B e antigen present in serum. Patients received famciclovir 125 mg, 250 mg, 500 mg three times daily (tid) or placebo for 16 weeks, followed by 8 months post-treatment observation, and 16 weeks open-label treatment. More than 90% of patients had previously received alpha-interferon or had baseline characteristics indicating a high likelihood of poor response to alpha-interferon.

RESULTS

Famciclovir induced rapid, dose-dependent suppression of viral replication and reduction in alanine aminotransferase (ALT), with greatest efficacy in the 500-mg tid treatment group. HBV DNA reduction was maintained throughout the treatment period. ALT also steadily declined during the treatment period. Approximately 40% of patients with pretreatment ALT>upper limit of normal (ULN) receiving famciclovir 500 mg tid, experienced sustained normalization of ALT at the end of the 8-month follow-up. Anti-HBe seroconversion occurred more frequently in patients receiving famciclovir 500 mg tid compared with placebo (p=0.04). Famciclovir was generally well tolerated; the incidence of adverse events was comparable to placebo. Exacerbation of liver disease or serious ALT flares were not observed.

CONCLUSION

Famciclovir 500 mg three times daily may offer an alternative to alpha-interferon for treatment for chronic hepatitis B. Anti-HBe seroconversion in the famciclovir 500-mg tid group suggests that 16 weeks treatment has the potential for HBV clearance. Further studies with a longer treatment duration are warranted.

Decrease of wild-type and precore mutant duck hepatitis B virus replication during lamivudine treatment in white Pekin ducks infected with the viruses

BACKGROUND/AIMS

Lamivudine, an antiviral agent, has been used in the treatment of chronic hepatitis B, but little is known about its effect on intrahepatic replication of hepatitis B virus. We investigated the effect of lamivudine on the replication of wild-type and precore mutant duck hepatitis B virus (DHBV) in the liver and serum of DHBV carrier ducks.

METHODS

Chronic carrier ducks with either wild-type or precore mutant DHBV were treated for 2 weeks with either low-dose (20 mg/kg, p.o., b.i.d.) or high-dose lamivudine (100 mg/kg, p.o., b.i.d.) or were untreated. Serum levels of DHBV DNA were examined serially by slot-blot hybridization. A second group of chronic carrier ducks was treated for 12 weeks with lamivudine (100 mg/kg, p.o., b.i.d.) or was untreated. The amount of DHBV DNA in serum and its various replicative intermediates in the liver were serially examined by slot-, Southern, and Northern blot methods.

RESULTS

In the 2-week treatment study, concentration of DHBV DNA in serum treated with low- and high-dose lamivudine was reduced to 10.8% and 1.1% of the control level in wild-type DHBV carriers, and to 2.3% and 0.48% in precore mutant DHBV carriers, respectively. In the 12-week treatment study, concentration of DHBV DNA in serum at the end of treatment was reduced to <0.65% and <5.36% in wild-type and precore mutant DHBV carriers, respectively. Southern and Northern blot analyses revealed that the various replicative forms of DHBV DNA in the liver were decreased in all treated ducks, but, covalently closed circular DNA and RNA intermediates tended to remain unchanged.

CONCLUSIONS

Our results showed that lamivudine could reduce both wild-type and precore mutant DHBV levels in the liver through inhibition of the reverse transcription step, but complete elimination of the viruses from liver is difficult even by relatively long-term lamivudine monotherapy, suggesting a need for some additional therapy to obtain complete clearance.

Antiviral chemotherapy for the treatment of hepatitis B virus infections

Approximately 5% of the world's human population have an increased risk for developing liver cancer and cirrhosis as a direct consequence of chronic infection with the hepatitis B virus (HBV). Antiviral chemotherapy remains the only option for controlling infection in these individuals, for whom the current licensed hepatitis B vaccines provide no benefit. Interferon (IFN)-alpha has proven benefit in a well-defined group of those with hepatitis B but has made little impact on the global burden of chronic liver disease. The development of more effective chemotherapy for treatment of chronic hepatitis B infection has proven to be extremely challenging, the result of both virus- and host-dependent factors, which will be reviewed in this article. Past attempts to treat chronic hepatitis B infection using nucleoside analogues were disappointing, but more recently, several nucleoside (or nucleotide) analogues have been identified that are potent and selective inhibitors of HBV replication. These agents fall into two broad categories: (1) nucleoside/nucleotides that have modified sugar residues in either cyclic or acyclic configurations and (2) stereoisomers of nucleosides in the "unnatural" L-configuration. Of the analogues that have been used clinically, representatives of the first category are purine derivatives, e.g., adefovir dipivoxil and famciclovir, whereas representatives of the second category are pyrimidine derivatives, such as lamivudine.

Antiviral agents in the critically ill child

The treatment for most viral infections in children primarily is supportive. Severe viral illnesses and significant secondary complications that require treatment in the intensive care unit may occur in immunocompromised patients and also in infants and children who were previously healthy. Antiviral agents with specific activity against certain respiratory viruses, herpesviruses, and enteric viruses are available. New drugs are under development, and their use in pediatric patients is a subject of active research. The clinician's knowledge of the mechanisms of action, spectrum of activity, and side effects of these drugs is an important tool for their judicious use in the treatment of the critically ill child. Copyright © 2000 by W.B. Saunders Company

Antiviral agents for non-human immunodeficiency virus infections

Several new agents for treating viral infections have been developed in recent years. All available agents are virustatic, inhibiting specific steps in the process of viral replication. No agent is active against nonreplicating or latent viruses. Acyclovir is useful in the treatment of genital herpes, herpes simplex encephalitis, mucocutaneous herpetic infection, varicella infection in the immunosuppressed host, and herpes zoster infection in the normal and the immunosuppressed host. It can also be used for prevention of herpesvirus infection in immunocompromised patients. Ganciclovir is indicated for the treatment of cytomegalovirus retinitis in patients with the acquired immunodeficiency syndrome and is effective in the treatment and prevention of cytomegalovirus infection in other immunocompromised patients. Famciclovir and valacyclovir are effective in the management of herpes simplex and varicella-zoster infection. Amantadine and rimantadine are useful therapeutically and prophylactically in the management of influenza A virus infection. Chronic hepatitis B infection can respond to lamivudine therapy, and the optimal treatment of hepatitis C is the combination of interferon alfa and ribavirin. Despite pronounced toxic effects, foscarnet and cidofovir are effective antiviral agents in specific settings.

Famciclovir treatment of chronic hepatitis B in heart transplant recipients: a prospective trial

Hepatitis B may take a rapid and aggressive course in patients under immunosuppression. Nucleoside analogues have been shown to suppress viral replication effectively. To investigate the effect of famciclovir in immunosuppressed patients, 21 heart transplant recipients with chronic hepatitis B infection were included in a prospective study.

PATIENTS AND METHODS

Patients have been treated with Famciclovir for a median of 14 months. Hepatitis B virus replication and biochemical parameters were regularly tested and liver biopsies were taken before treatment and after a median time of 7 months. HBV-polymerase was sequenced in all patients before therapy and in those patients who experienced virological breakthrough.

RESULTS

Nineteen patients were treated for at least 6 months. Hepatitis B virus-DNA levels declined in all patients and became negative in 8 patients. Mean hepatitis B virus-DNA levels decreased from 199+/-269 to 34+/-53 pg/ml after 24 weeks (P=0.003). During treatment HBeAg became negative in five patients. Mean alanine aminotransferase decreased from 42+/-26 to 24+/-10 U/L (P=0.006). Histological analysis revealed improved inflammatory activity according to the Ishak-score in 11/16 (69%) patients. Total inflammatory activity scores decreased from 8 to 6 (median, NS), but interface hepatitis score (P=0.02) and lobular inflammation score (P=0.006) improved significantly. Median fibrosis scores fell from 5 to 3 (P=0.002). Three patients developed virological breakthrough on famciclovir after 7, 8, and 26 months of treatment showing HBV-polymerase amino acid changes L528 M, S567A, and I581K, respectively.

CONCLUSIONS

Famciclovir improves not only biochemical and virological features but also hepatic inflammation and liver fibrosis in patients with chronic hepatitis B under heavy immunosuppression. Virological breakthrough may develop and requires close monitoring.

Clinical management of selected oral fungal and viral infections during HIV-disease

The purpose of this review is to describe current possibilities of management of selected fungal and viral oral opportunistic infections including oral candidiasis, herpes simplex type 1 and 2-related lesions (HSV1,2), oral hairy leukoplakia (OHL) and oral lesions associated with human papilloma viruses (HPV). Less common diseases such as cytomegalovirus infection or human herpes virus type 8 associated with Kaposi's sarcoma and others are not considered. In a number of instances lifelong therapy or prophylaxis has to be instituted. Antiretroviral combination therapy, also called highly active antiretroviral therapy (HAART), has considerably changed the frequency of oral lesions caused by opportunistic agents. A short description of the antiretroviral agents available including respective side-effects is presented.

A placebo-controlled phase I/II study of adefovir dipivoxil in patients with chronic hepatitis B virus infection

Adefovir dipivoxil (bis-POM PMEA) is an adenine nucleotide analogue with activity against retroviruses and herpesviruses, and in vitro activity against hepatitis B virus (HBV). This study was conducted to evaluate its safety and antiviral activity in patients with chronic HBV infection. Twenty patients (13 co-infected with human immunodeficiency virus, HIV) were randomized in a phase I/II, double-blind, placebo-controlled study. Patients who had been hepatitis B surface antigen (HBsAg)/hepatitis B e antigen (HBeAg) positive for > or = 6 months, with elevated hepatic transaminases and serum HBV DNA > or = 50 pg ml-1, were randomized to adefovir dipivoxil 125 mg (n = 15) or placebo (n = 5) as a single, daily, oral dose for 28 days. Antiviral activity was assessed by changes in serum HBV DNA (using the Digene Hybrid Capture assay) and HBeAg/hepatitis B e antibody (HBeAb) status. HBV DNA levels fell rapidly by > 1 log10 in all active drug recipients (median fall 1.8 log10 pg ml-1) but increased by 0.01 log10 pg ml-1 in controls (P = 0.002). Reductions were sustained during treatment. HBV DNA returned to baseline over 1-6 weeks following discontinuation of active drug. HBeAg became transiently undetectable in one patient on treatment and, in another, sustained seroconversion to HBeAb occurred 12 weeks after treatment ended. Liver transaminase elevations > 300 U l-1 were observed in three patients during therapy (leading to protocol-specified treatment discontinuation or dose reduction) and in four patients during follow-up. On-treatment transaminase elevations were associated with HIV status, occurring in three of six HIV-uninfected patients compared with none of nine who were HIV infected. In addition, a slower return to baseline of serum HBV DNA levels was observed in the non-HIV-infected patients. Treatment for chronic hepatitis B as a once-daily oral dose was well tolerated and associated with significant and sustained reductions in serum HBV DNA levels during treatment. Transaminase elevations, which may be related to the therapeutic effect, were observed during and after treatment. Further studies are warranted to investigate the safety, and optimum dose and duration, of adefovir dipivoxil treatment for chronic hepatitis B.

Treatment of chronic hepatitis B: new antiviral therapies

Chronic hepatitis B infection is the most important cause of cirrhosis and hepatocellular carcinoma worldwide. Interferon-alpha has been shown to be effective in approximately one third of patients, and response seems to be sustained in long-term follow-up studies in Western countries. New treatments using lamivudine and other nucleoside analogues such as famciclovir, lobucavir, and adfovir showed promising results although sustained suppression of viral replication is unusual after discontinuation of therapy. The results of recent clinical studies using these nucleoside analogues are discussed in detail in this review. Other important issues such as drug resistance and the role of combination therapy are also addressed.

Resolution of recurrent hepatitis B in two liver transplant recipients treated with famciclovir

Recurrent hepatitis B infection after orthotopic liver transplantation remains problematic despite prophylaxis with hepatitis B immune globulin (anti-HBs IgG). Recently, famciclovir (an oral nucleoside analog) has been shown to have potent antiviral activity against hepatitis B in vitro as well as in patients with chronic hepatitis B. We present two patients who developed recurrent hepatitis B after orthotopic liver transplantation and were treated with famciclovir, 500 mg t.i.d. Both patients subsequently responded with marked improvement in biochemical liver tests and histology, with subsequent loss of hepatitis B surface antigen. Famciclovir is a useful agent in the treatment of hepatitis B in the liver transplant recipient.

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.

Antiviral treatment of diseases in pediatric dermatology

Pediatric dermatologic disease that have specific therapies and/or specific prophylactic measures are reviewed. Herpes simplex virus and varicella-zoster virus infections, human papillomavirus infections, and molluscum contagiosum infections are discussed with special emphasis on recent advances of therapy and prophylaxis.

Famciclovir (FAMVIR)

Famciclovir is an antiviral with efficacy and safety comparable to aciclovir, but famciclovir's more favorable pharmacokinetic profile enables a less frequent dosing regimen. Future trials will likely determine famciclovir's role in the suppression of HBV.