Telbivudine: a new nucleoside analogue for the treatment of chronic hepatitis B

Hepatitis B surface antigen: carcinogenesis mechanisms and clinical implications in hepatocellular carcinoma

Liver cancer is the third leading cause of death globally, with hepatitis B virus (HBV) infection being identified as the primary risk factor for its development. The occurrence of HBV-related hepatocellular carcinoma (HCC) is attributed to various mechanisms, such as chronic inflammation and liver cell regeneration induced by the cytotoxic immune response triggered by the virus, abnormal activation of oncogenes arising from HBV DNA insertion mutations, and epigenetic alterations mediated by viral oncoproteins. The envelope protein of the HBV virus, known as hepatitis B surface antigen (HBsAg), is a key indicator of increased risk for developing HCC in HBsAg-positive individuals. The HBsAg seroclearance status is found to be associated with recurrence in HCC patients undergoing hepatectomy. Additional evidence indicates that HBsAg is essential to the entire process of tumor development, from initiation to advancement, and acts as an oncoprotein involved in accelerating tumor progression. This review comprehensively analyzes the extensive effects and internal mechanisms of HBsAg during the various stages of the initiation and progression of HCC. Furthermore, it highlights the importance and potential applications of HBsAg in the realms of HCC early diagnosis and personalized therapeutic interventions. An in-depth understanding of the molecular mechanism of HBsAg in the occurrence and development of HCC is provided, which is expected to develop more precise and efficient strategies for the prevention and management of HCC in the future.

Targeting hepatitis B virus-associated nephropathy: efficacy and challenges of current antiviral treatments

Hepatitis B virus (HBV) infection remains a major global health challenge, affecting approximately 296 million people and causing significant mortality annually. Despite vaccination efforts, HBV prevalence persists, particularly in low- and middle-income regions and endemic areas like China. HBV is closely associated with various kidney diseases, including acute kidney injury, chronic kidney disease, and glomerulonephritis, through mechanisms such as immune complex deposition, direct viral invasion, and chronic inflammation. Patients undergoing hemodialysis or kidney transplantation are at increased risk of HBV infection and reactivation, highlighting the need for effective preventive and therapeutic measures. This review examines the classification and clinical features of HBV-associated nephropathy, focusing on membranous nephropathy and membranoproliferative glomerulonephritis. It explores the pathogenesis, emphasizing immune complex deposition and podocyte apoptosis. Antiviral therapy, particularly with nucleos(t)ide analogs like entecavir and tenofovir (including TAF and TMF), demonstrates superior efficacy and safety compared to older agents such as lamivudine and adefovir. While interferon therapy offers benefits, its use is limited by adverse effects. Additionally, individualized treatment strategies for specific populations, including pregnant women and HIV co-infected patients, are crucial. Addressing HBV-associated nephropathy requires enhanced surveillance, timely antiviral intervention, and tailored therapeutic approaches to improve patient outcomes.

Integrated Microbiome and Metabolomics Analysis of the Effects of Dietary Supplementation with Corn-Steep-Liquor-Derived Candida utilis Feed on Black Pigs

In this experiment, glucose master liquor and corn steep liquor were used as carbon and nitrogen sources, and Candida utilis was used as a strain to ferment yeast feed. The OD value and number of yeast cells were used as response values to optimize the medium components of the yeast feed through a response surface methodology. The optimal medium components were a glucose master liquor concentration of 8.3%, a corn steep liquor concentration of 1.2%, and a KH2PO4 concentration of 0.14%. Under this condition of fermentation, the OD value was 0.670 and the number of yeast cells was 2.72 × 108/mL. Then, we fed Candida utilis feed to Dongliao black piglets, and the effects of the yeast feed on the piglets' growth performance, fecal microbiota, and plasma metabolic levels were investigated through 16S rDNA sequencing and metabolomics. In total, 120 black piglets with an average initial weight of 6.90 ± 1.28 kg were randomly divided into two groups. One group was fed the basic diet (the CON group), and the other was supplemented with 2.5% Candida utilis add to the basic diet (the 2.5% CU group). After a pre-feeding period, the formal experiments were performed for 21 days. The results showed that the addition of Candida utilis to the diet did not affect growth performance compared with the control group. Meanwhile, no significant differences were observed in the serum biochemical indices. However, piglets in the 2.5% CU group had a significantly altered fecal microbiota, with an increased abundance of Clostridium_sensu_stricto_1, Lactobacillus, and Muribaculaceae_unclassified. Regarding the plasma metabolome, the 12 differential metabolites detected were mainly enriched in the histidine, tryptophan, primary bile acid, and caffeine metabolic pathways. Regarding the integrated microbiome-metabolome analysis, differential metabolites correlated with fecal flora to variable degrees, but most of them were beneficial bacteria of Firmicutes. Collectively, dietary Candida utilis feed had no adverse effect on growth performance; however, it played an important role in regulating fecal flora and maintaining metabolic levels.

Nucleoside Analogue Reverse Transcriptase Inhibitors Improve Clinical Outcome in Transcriptional Active Human Parvovirus B19-Positive Patients

Human parvovirus B19 (B19V) is the predominant cardiotropic virus associated with dilated inflammatory cardiomyopathy (DCMi). Transcriptionally active cardiotropic B19V infection is clinically relevant and triggers adverse long-term mortality. During the study; we evaluated whether antiviral treatment with the nucleoside analogue telbivudine (LTD) is effective in suppressing transcriptional active B19V in endomyocardial biopsies (EMBs) of B19V positive patients and improving clinical outcomes. Seventeen B19V-positive patients (13 male; mean age 45.7 ± 13.9 years; mean left ventricular ejection fraction (LVEF) 37.7 ± 13.5%) with positive B19V DNA and transcriptional activity (B19V mRNA) in EMBs were treated with 600 mg/d LTD over a period of six months. Patients underwent EMBs before and after termination of the LTD treatment. B19V RNA copy numbers remained unchanged in 3/17 patients (non-responder) and declined or disappeared completely in the remaining 14/17 patients (responder) (p ≤ 0.0001). Notably; LVEF improvement was more significant in patients who reduced or lost B19V RNA (responder; p = 0.02) in contrast to non-responders (p = 0.7). In parallel; responder patients displayed statistically significant improvement in quality of life (QoL) questionnaires (p = 0.03) and dyspnea on exertion (p = 0.0006), reflecting an improvement in New York Heart Association (NYHA) Classification (p = 0.001). Our findings demonstrated for the first time that suppression of B19V transcriptional activity by LTD treatment improved hemodynamic and clinical outcome significantly. Thus; the present study substantiates the clinical relevance of detecting B19V transcriptional activity of the myocardium.

YM155 Inhibits NleB and SseK Arginine Glycosyltransferase Activity

The type III secretion system effector proteins NleB and SseK are glycosyltransferases that glycosylate protein substrates on arginine residues. We conducted high-throughput screening assays on 42,498 compounds to identify NleB/SseK inhibitors. Such small molecules may be useful as mechanistic probes and may have utility in the eventual development of anti-virulence therapies against enteric bacterial pathogens. We observed that YM155 (sepantronium bromide) inhibits the activity of Escherichia coli NleB1, Citrobacter rodentium NleB, and both Salmonella enterica SseK1 and SseK2. YM155 was not toxic to mammalian cells, nor did it show cross-reactivity with the mammalian O-linked N-acetylglucosaminyltransferase (OGT). YM155 reduced Salmonella survival in mouse macrophage-like cells but had no direct impact on bacterial growth rates, suggesting YM155 may have utility as a potential anti-virulence inhibitor.

The evolution of nucleoside analogue antivirals: A review for chemists and non-chemists. Part 1: Early structural modifications to the nucleoside scaffold

This is the first of two invited articles reviewing the development of nucleoside-analogue antiviral drugs, written for a target audience of virologists and other non-chemists, as well as chemists who may not be familiar with the field. Rather than providing a simple chronological account, we have examined and attempted to explain the thought processes, advances in synthetic chemistry and lessons learned from antiviral testing that led to a few molecules being moved forward to eventual approval for human therapies, while others were discarded. The present paper focuses on early, relatively simplistic changes made to the nucleoside scaffold, beginning with modifications of the nucleoside sugars of Ara-C and other arabinose-derived nucleoside analogues in the 1960's. A future paper will review more recent developments, focusing especially on more complex modifications, particularly those involving multiple changes to the nucleoside scaffold. We hope that these articles will help virologists and others outside the field of medicinal chemistry to understand why certain drugs were successfully developed, while the majority of candidate compounds encountered barriers due to low-yielding synthetic routes, toxicity or other problems that led to their abandonment.

The Ca2+/CaMKK2 axis mediates the telbivudine induced upregulation of creatine kinase: Implications for mechanism of antiviral nucleoside analogs' side effect

Telbivudine (LdT), a widely prescribed anti-hepatitis B virus (HBV) drug for the treatment of chronic Hepatitis B (CHB), causes adverse reactions ranging from creatine kinase (CK) elevation to myopathy. The purpose of this study was to explore the mechanism(s) of LdT induced CK elevation. The effects of LdT on mitochondrial morphology and proteins (TK2 and β-actin), oxidative stress, intracellular Ca²⁺ levels, Ca²⁺-related signaling pathway (CaMKK2/AMPK), and Ca²⁺-related biomarkers such as superoxide dismutase (SOD) and malondialdehyde (MDA) were assessed in human skeletal muscle cells (HSKMCs). The results showed that LdT induced a dose-dependent increase in CK activity in HSKMCs, without affecting mitochondrial morphology, and TK2 and β-actin protein levels, following 72 h of treatment. In addition, LdT increased Ca²⁺ production, ROS generation, MDA and lipid peroxide (LPO) levels, and activated the CaMKK2/AMPK signaling pathway. Moreover, these effects were attenuated by the BAPIA-AM (the calcium chelator). We also confirmed the presence of relevant markers (MDA, LPO, and SOD) in serum from CHB patients after LdT treatment, and found that CK was positively correlated with MDA and LPO, and negatively associated with SOD. These findings indicate that LdT induces CK elevation and oxidative stress associated with imbalance of intracellular Ca²⁺ in HSKMCs, suggesting that Ca²⁺/CaMKK2 axis imbalance may underlie human LdT-induced CK elevation. The present findings provide a solid basis for assessing the mechanism of drug-induced CK elevation, which can help develop new tools for the prevention and treatment of diseases associated with drug-induced CK elevation.

Continuous venovenous hemodiafiltration for hyperlactatemia caused by telbivudine in a patient with chronic hepatitis B: a case report and update review

Although there have been reports on telbivudine-induced myopathy and creatine kinase (CK) elevation, few reports focus on its effect on hyperlactatemia in patients with chronic hepatitis B (CHB). Here we reported a case of hyperlactatemia during telbivudine treatment. A 26-year-old Chinese man had been receiving telbivudine for CHB since July 2011, with a CK level of 68 U/L before the antiviral therapy. After 3 months he felt muscular weakness in both upper and lower extremities. A check in the local clinic found his CK level was increased to 222 U/L (upper limit of normal 170 U/L). However, he did not visit his doctor or stop the telbivudine treatment until he felt myalgia throughout his body. By this time his CK level had increased to 4151 U/L. Even after the withdrawal of telbivudine, his myalgia was exacerbated and his CK level was decreased extremely slowly. His constant myolysis developed into hyperlactatemia and he finally recovered after successful venovenous hemodiafiltration. The findings in this patient suggest that telbivudine may lead to high CK levels and hyperlactatemia may occur if telbivudine is not discontinued immediately when CK levels are clearly increased. Moreover, we emphasized that serum CK and lactate levels should be monitored closely during treatment with telbivudine in patients with CHB.

Targeting the Achilles heel of the hepatitis B virus: a review of current treatments against covalently closed circular DNA

Chronic infection with hepatitis B virus (HBV) often leads to the development of liver cancer and cirrhosis, creating immense sociological, clinical and economic burdens worldwide. Although current anti-HBV medications manage to control the disease progression and help restore normal liver functions, they often fail to eliminate the virus completely. A major reason for this failure is the presence of a stable viral genome in the hepatocyte nucleus: the covalently closed circular DNA (cccDNA). Targeting HBV cccDNA is a promising approach that could lead to a complete cure. Here, we review various research approaches that are directed toward eliminating HBV cccDNA. This is a brief, yet comprehensive, summary of current state-of-the-art developments in this emerging area of interest.

The Molecular and Structural Basis of HBV-resistance to Nucleos(t)ide Analogs

Infection with hepatitis B virus (HBV) is a worldwide health problem. Chronic hepatitis B can lead to fibrosis, liver cirrhosis, and hepatocellular carcinoma (HCC). Management of the latter two conditions often requires liver transplantation. Treatment with conventional interferon or pegylated interferon alpha can clear the virus, but the rates are very low. The likelihood, however, of viral resistance to interferon is minimal. The main problems with this therapy are the frequency and severity of side effects. In contrast, nucleos(t)ide analogs (NAs) have significantly lower side effects, but require long term treatment as sustained virological response rates are extremely low. However, long term treatment with NAs increases the risk for the development of anti-viral drug resistance. Only by understanding the molecular basis of resistance and using agents with multiple sites of action can drugs be designed to optimally prevent the occurrence of HBV antiviral resistance.

Structural and kinetic characterization of human deoxycytidine kinase variants able to phosphorylate 5-substituted deoxycytidine and thymidine analogues

The physiological role of human deoxycytidine kinase (dCK) is to phosphorylate deoxynucleosides required for DNA synthesis, with the exception of thymidine. Previous structural analysis of dCK implicated steric factors, specifically the thymine methyl group at the 5-position, that prevent thymidine phosphorylation by dCK. This hypothesis is supported by the observation that mutations that enlarge the active site cavity in proximity to the nucleoside 5-position endow dCK with the ability to phosphorylate thymidine. However, in conflict with this hypothesis was our discovery that the cytidine analogue 5-methyldeoxycytidine (5-Me-dC), an isostere of thymidine, can indeed be phosphorylated by wild-type (WT) dCK. To reconcile this seemingly contradicting observation, and to better understand the determinants preventing thymidine phosphorylation by WT dCK, we solved the crystal structure of dCK in complex with 5-Me-dC. The structure reveals the active site adjustments required to accommodate the methyl group at the 5-position. Combination of kinetic, mutagenesis, and structural data suggested that it is in fact residue Asp133 of dCK that is most responsible for discriminating against the thymine base. dCK variants in which Asp133 is replaced by an alanine and Arg104 by select hydrophobic residues attain significantly improved activity with 5-substituted deoxycytidine and thymidine analogues. Importantly, the ability of the designer enzymes to activate 5-substitued pyrimidines makes it possible to utilize such nucleoside analogues in suicide gene therapy or protein therapy applications that target cancer cells.

Development of a novel mouse model to evaluate drug candidates against hepatitis B virus

Woodchuck hepatitis virus (WHV)-infected woodchucks have been used for preclinical development of drugs against hepatitis B virus (HBV). However, there is no simple in vivo model to evaluate small amounts of compounds against HBV. To develop such a model, HepAD38 cells, in which HBV replication is regulated by tetracycline (tet), were grown as subcutaneous tumours in nude mice. Mice developing viraemia were then left untreated or given tet in the drinking water. In some of the mice given tet, it was removed and the mice were injected intraperitoneally with phosphate buffer saline (PBS), lamivudine (3TC), clevudine (CLV) or tenofovir dipivoxil fumarate (TDF). Virus DNA titres were measured by real-time PCR during and after drug treatment. In water-fed and PBS-injected mice, virus titres reached approximately 10(9) copies/ml serum within 35 days of HepAD38 injection, whereas in tet-treated mice, virus titres remained at 10(4)-10(5) copies/ml. HBV DNA levels were suppressed by 3TC, TDF and CLV, with the latter two drugs showing more sustained virus suppression compared with 3TC. Combination therapy with CLV plus TDF was much more effective than either drug alone in suppressing virus titre for at least 3 weeks after the end of treatment. There was no demonstrable toxicity to HepAD38 cells in drug-treated mice. Hence, a robust tet-controlled system for HBV replication in vivo was demonstrated, validated with monotherapies against HBV and shown to be useful in assessing combination therapy. This system will be useful for preclinical assessment of small amounts of single or multiple compounds against HBV in vivo.

Telbivudine in the treatment of chronic hepatitis B

Treatment of chronic hepatitis B with oral nucleos(t)ide analogs is evolving rapidly with newer compounds gaining approval. Recently, the US FDA and European Medicines Agency (EMEA) have approved telbivudine, a potent anti-hepatitis B virus (HBV)-specific agent with a hitherto excellent safety profile. This review focuses on the efficacy of this agent in chronic hepatitis B compared with lamivudine, evaluated clinically in Phase II and a large Phase III study. Monitoring of the virologic response under treatment with sensitive HBV-DNA assays has been applied, aiming at increasing efficacy and reducing HBV resistance. The results are critically presented and the evolving concept of effective long-term telbivudine and other nucleos(t)ide analog therapy, predicted by the extent of suppression of HBV replication at week 24, are analyzed and discussed.

Genotyping and genomic sequencing in clinical practice

The global prevalence of chronic hepatitis B and its associated serious sequelae demand technologically advanced techniques of management. Nucleic acid testing (NAT) plays a key role in the diagnosis, surveillance, and treatment of chronic hepatitis B. NAT includes quantitative PCR-based HBV DNA assays, HBV genotyping, tests for mutations associated with resistance to antiviral medications, and assays to detect precore and core promoter mutations. This article reviews the uses of NAT in the diagnosis and management of chronic hepatitis B.

Treatment paradigms on hepatitis B e antigen-negative chronic hepatitis B patients

The primary goal of treatment in hepatitis B e antigen (HBeAg)-negative patients with chronic hepatitis B (CHB) is potent and durable suppression of hepatitis B virus (HBV) replication. It results in biochemical and histological remission of CHB and is the prerequisite for the prevention of cirrhosis, its life-threatening complications and hepatocellular carcinoma. Responses that are durable after the cessation of treatment are referred to as sustained virological responses, whereas those persisting under therapy are referred to as treatment-maintained virological responses. Treatment paradigms of sustained virological response in HBeAg-negative CHB are practically restricted to conventional IFN-alpha and pegylated interferons (peg-IFNs), and are limited only to patients with compensated liver disease. Long-lasting maintained virological responses without HBV resistance in HBeAg-negative CHB are achievable by all approved nucleos(t)ide analogues (lamivudine, adefovir and entecavir) in highly variable rates, depending on their potency, rapidity of virological response and genetic barrier to resistance. The maintenance of response under 5 years of adefovir treatment represents the most effective treatment paradigm for HBeAg-negative CHB, whereas such long-term data with entecavir and tenofovir monotherapy may become available in the near future. In patients with lamivudine-resistant HBV mutants, the recommended treatment strategy is to add adefovir at the same time as continuing treatment with lamivudine. There are no treatment paradigms as yet of combination therapy from the very outset with two nucleoside analogues for use in treatment-naive patients.

Multiplex locked nucleic acid probes for analysis of hepatitis B virus mutants using real-time PCR

Current methods of detecting hepatitis B virus (HBV) mutations are time consuming, labor intensive, and not suitable for screening large numbers of samples. A multiplex real-time PCR approach presented in this article is a hepatitis B virus quantification method that employs the SYBR Green I dye in conjunction with wild-type HBV sequence-specific locked nucleic acid (LNA) probes. The three short LNA probes distinguished the wild-type strain or three groups of mutants (rt173, rt180/rt181, and rt202/rt204) depending on perfect-match hybrids or mismatch within one template simultaneously. Primers labeled with quencher minimized the background signals. This sensitive approach could quantify 10(2) copies of HBV virus, and as low as 1% mutants among 10(4) copies of wild-type HBV could be identified. The technique is handy and convenient, requiring only 3.5 h to analyze 30 hepatitis B surface antigen-positive serum samples. The HBV isolates were confirmed by direct sequencing. Our data indicate that real-time PCR with SYBR Green I dye is a reliable, rapid, and convenient technique for HBV quantification. Furthermore, by incorporating fluorescent LNA probes, this technique becomes handy in identifying and classifying mutations in the HBV polymerase gene. Being sensitive, specific, accurate, rapid, and convenient in nature, this technique could be a suitable diagnostic tool with wide application particularly in cases in which large volumes of clinical samples are handled.

Synthesis of beta-L-2'-deoxythymidine (L-dT)

The "unnatural" l-nucleoside beta-l-2'-deoxythymidine (L-dT) is a potent, specific, and selective inhibitor of the replication of hepatitis B virus (HBV), which is currently in Phase III clinical trials. This unit describes, in detail, a semi-large-scale synthesis of l-dT. This convenient methodology produces l-dT in six steps starting with l-ribose and ending with a satisfactory overall yield of l-dT, and may be applied to other 2'-deoxynucleosides, incorporating different heterocyclic bases.

An Update in the Management of Hepatitis B/HIV Coinfection

With growing numbers of hepatitis B virus (HBV)/ HIVcoinfected patients and the complexity of treating both diseases together, new treatment options and guidelines are available. This article reviews treatment and management options for HBV/HIV-coinfected patients.