Past, Current, and Future Developments of Therapeutic Agents for Treatment of Chronic Hepatitis B Virus Infection

Exploring the potential of drug repurposing for liver diseases: A comprehensive study

Drug repurposing involves the investigation of existing drugs for new indications. It offers a great opportunity to quickly identify a new drug candidate at a lower cost than novel discovery and development. Despite the importance and potential role of drug repurposing, there is no specific definition that healthcare providers and the World Health Organization credit. Unfortunately, many similar and interchangeable concepts are being used in the literature, making it difficult to collect and analyze uniform data on repurposed drugs. This research was conducted based on understanding general criteria for drug repurposing, concentrating on liver diseases. Many drugs have been investigated for their effect on liver diseases even though they were originally approved (or on their way to being approved) for other diseases. Some of the hypotheses for drug repurposing were first captured from the literature and then processed further to test the hypothesis. Recently, with the revolution in bioinformatics techniques, scientists have started to use drug libraries and computer systems that can analyze hundreds of drugs to give a short list of candidates to be analyzed pharmacologically. However, this study revealed that drug repurposing is a potential aid that may help deal with liver diseases. It provides available or under-investigated drugs that could help treat hepatitis, liver cirrhosis, Wilson disease, liver cancer, and fatty liver. However, many further studies are needed to ensure the efficacy of these drugs on a large scale.

Hepatitis B virus-specific human stem cell memory T cells differentiate into cytotoxic T cells and eradicate HBV-infected hepatocytes in mice

Chronic infection with the hepatitis B virus (HBV) induces progressive hepatic impairment. Achieving complete eradication of the virus remains a formidable challenge. Cytotoxic T lymphocytes, specific to viral antigens, either exhibit a numerical deficiency or succumb to an exhausted state in individuals chronically afflicted with HBV. The comprehension of the genesis and dissemination of stem cell memory T cells (TSCMs) targeting HBV remains inadequately elucidated. We identified TSCMs in subjects with chronic HBV infection and scrutinized their efficacy in a murine model with human hepatocyte transplants, specifically the TK-NOG mice. TSCMs were discerned in all subjects under examination. Introduction of TSCMs into the HBV mouse model precipitated a severe necro-inflammatory response, resulting in the elimination of human hepatocytes. TSCMs may constitute a valuable tool in the pursuit of a remedial therapy for HBV infection.

Identification of dihydroquinolizinone derivatives with nitrogen heterocycle moieties as new anti-HBV agents

The sustained loss of HBsAg is considered a pivotal indicator for achieving functional cure of HBV. Dihydroquinolizinone derivatives (DHQs) have demonstrated remarkable inhibitory activity against HBsAg both in vitro and in vivo. However, the reported neurotoxicity associated with RG7834 has raised concerns regarding the development of DHQs. In this study, we designed and synthesized a series of DHQs incorporating nitrogen heterocycle moieties. Almost all of these compounds exhibited potent inhibition activity against HBsAg, with IC50 values at the nanomolar level. Impressively, the compound (S)-2a (10 μM) demonstrated a comparatively reduced impact on the neurite outgrowth of HT22 cells and isolated mouse DRG neurons in comparison to RG7834, thereby indicating a decrease in neurotoxicity. Furthermore, (S)-2a exhibited higher drug exposures than RG7834. The potent anti-HBV activity, reduced neurotoxicity, and favorable pharmacokinetic profiles underscore its promising potential as a lead compound for future anti-HBV drug discovery.

Catenulopyrizomicins, new anti-Hepatitis B virus compounds, from the rare actinomycete Catenuloplanes sp. MM782L-181F7

Hepatitis B virus (HBV) causes chronic hepatitis in humans, and current antiviral therapies rarely treat viral infections. To improve the treatment efficacy, novel therapeutic agents, especially those with different mechanisms of action, need to be developed for use in combination with the current antivirals. Here, we isolated new anti-HBV compounds, named catenulopyrizomicins A-C, from the fermentation broth of rare actinomycete Catenuloplanes sp. MM782L-181F7. Structural analysis revealed that these compounds contained a structure that is composed of thiazolyl pyridine moiety. The catenulopyrizomicins reduced the amount of intracellular viral DNA in HepG2.2.15 cells with EC50 values ranging from 1.94 to 2.63 µM with small but notable selectivity. Mechanistic studies indicated that catenulopyrizomicin promotes the release of immature virion particles that fail to be enveloped through alterations in membrane permeability.

Discovery of 4,5,6,7-Tetrahydropyrazolo[1.5-a]pyrizine Derivatives as Core Protein Allosteric Modulators (CpAMs) for the Inhibition of Hepatitis B Virus

Hepatitis B Virus (HBV) core protein allosteric modulators (CpAMs) are an attractive class of potential anti-HBV therapeutic agents. Here we describe the efforts toward the discovery of a series of 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine (THPP) compounds as HBV CpAMs that effectively inhibit a broad range of nucleos(t)ide-resistant HBV variants. The lead compound 45 demonstrated inhibition of HBV DNA viral load in a HBV AAV mouse model by oral administration.

Structure-based Design of Novel Hepatitis B Virus Capsid Assembly Modulators

Small-molecule capsid assembly modulators (CAMs) have been recently recognized as promising antiviral agents for curing chronic hepatitis B virus (HBV) infection. A target-based in silico screening study is described, aimed towards the discovery of novel HBV CAMs. Initial optimization of four weakly active screening hits was performed via focused library synthesis. Lead compound 42 and close analogues 56 and 57 exhibited in vitro potency in the sub- and micromolar range along with good physico-chemical properties and were further evaluated in molecular docking and mechanism of action studies.

A review of epidemiology and clinical relevance of Hepatitis B virus genotypes and subgenotypes

BACKGROUND

Hepatitis B virus (HBV) infection is a global public health burden, affecting nearly 300 million people around the world. Due to HBV population is considered to be represented as a viral quasispecies with genetic diversity, some reports showed that different genotypes of HBV have different viral effects, though the emergence of antiviral drugs that effectively inhibit viral replication, however, HBV infection has still not been eradicated and further research is needed.

SUMMARY

HBV has been classified into at least ten genotypes (A-J)  and more than 40 subgenotypes based on an intergroup or intragroup nucleotide difference across the whole genome, respectively. Inter genotypic recombinants were also observed during the HBV evolution. HBV genotypes and subgenotypes have distinct ethno-geographical distributions, as well as evident differences in their biological characteristics. HBV genotypes and subgenotypes also have close association with disease severity, long-term clinical outcomes, and response to antiviral therapy.

KEYMESSAGES

In this review, we up-dated the epidemiological characteristics, clinical features and prognosis of HBV infection with dissimilar genotype/subgenotypes, to better understanding and developing individualized prevention and treatment strategies.

Inhibition of Hepatitis B Virus (HBV) replication and antigen expression by Brucea javanica (L.) Merr. oil emulsion

Introduction

The seeds of Brucea javanica (L.) Merr. (BJ) have been traditionally used to treat various types of cancers for many years in China. In this study, we systematically investigated a BJ oil emulsion (BJOE) produced from BJ seeds with the purpose of evaluating its antiviral effect against hepatitis B virus (HBV).

Methods

HepG2.215 (a wild-type HBV cell line), HepG2, and Huh7, transfected with wildtype (WT) or lamivudine-resistance mutant (LMV-MT) HBV replicon plasmids, were treated with different doses of BJOE and then used for pharmacodynamic evaluation. Cell viability was determined using CCK8 assay. The levels of HBsAg/HBeAg in cell cultured supernatant, HBcAg in cell lysis solution, and HBV DNA in both were evaluated.

Results

BJOE at ≤5 mg/ml was nontoxic to carcinoma cell lines, but could significantly inhibit WT/LMV-MT HBV replication and HBs/e/c antigen expression in a dose-dependent manner by upregulating interleukin-6 (IL-6), demonstrating that it possesses moderate anti-HBV activity. As one of the major components of BJOE, bruceine B was found to play a dominant role in IL-6 induction and HBV inhibition.

Discussion

Our results demonstrated that BJOE suppressed HBV replication by stimulating IL-6, indicating that it has promising clinical therapeutic potential for both WT and LMV-MT HBV.

Design and Synthesis of (3-Phenylisoxazol-5-yl)methanimine Derivatives as Hepatitis B Virus Inhibitors

Series of (3-phenylisoxazol-5-yl)methanimine derivatives were synthesized, and evaluated for anti-hepatitis B virus (HBV) activity in vitro. Half of them more effectively inhibited HBsAg than 3TC, and more favor to inhibit secretion of HBeAg than to HBsAg. Part of the compounds with significant inhibition on HBeAg were also effectively inhibit replication of HBV DNA. Compound (E)-3-(4-fluorophenyl)-5-((2-phenylhydrazineylidene)methyl)isoxazole inhibited excellently HBeAg with IC₅₀ in 0.65 μM (3TC(Lamivudine) in 189.90 μM), inhibited HBV DNA in 20.52 μM (3TC in 26.23 μM). Structures of compounds were determined by NMR and HRMS methods, and chlorination on phenyl ring of phenylisoxazol-5-yl was confirmed by X-ray diffraction analysis, and the structure-activity relationships (SARs) of the derivatives was discussed. This work provided a new class of potent non-nucleoside anti-HBV agents.

Pharmacophore-Based Virtual Screening and Structural Modification of Novel Benzamide Derivatives as HBV Capsid Assembly Modulators

Hepatitis B virus (HBV) infection is the most common cause of death from liver disease worldwide. The use of capsid assembly modulators is considered a prominent strategy for the development of novel anti-HBV therapies. We performed a pharmacophore-based virtual screening strategy, and a benzamide scaffold hit, WAI-5, was chosen for further structural optimization. A series of novel HBV capsid assembly modulators (CAMs) were found. Compared with the lead hit, the representative compounds 11g and 11n exhibited a 10-fold increase in anti-HBV activity with 50% effective concentration (EC50) values of 1.74 and 1.90 µM, respectively.

Safety and efficacy of vebicorvir administered with entecavir in treatment-naïve patients with chronic hepatitis B virus infection

BACKGROUND & AIMS

Nucleos(t)ide reverse transcriptase inhibitors do not completely suppress HBV DNA in chronic HBV infection (cHBV). Vebicorvir (VBR) is an investigational core inhibitor that interferes with multiple aspects of HBV replication. This phase II trial evaluated the safety and efficacy of VBR in combination with entecavir (ETV) in treatment-naïve patients with cHBV.

METHODS

HBeAg-positive, treatment-naïve patients without cirrhosis were randomised 1:1 in a double-blind manner to once-daily VBR 300 mg+ETV 0.5 mg or placebo (PBO)+ETV 0.5 mg for 24 weeks. The primary endpoint was change in mean log₁₀ HBV DNA from Baseline to Week 12 and 24.

RESULTS

All patients in both treatment groups (PBO+ETV: 12/12; VBR+ETV: 13/13) completed the study. At Week 12, VBR+ETV led to a greater mean (SD) reduction from Baseline in log₁₀ IU/ml HBV DNA (-4.45 [1.03]) vs. PBO+ETV (-3.30 [1.18]; p = 0.0077). At Week 24, VBR+ETV led to a greater reduction from Baseline in log₁₀ IU/ml HBV DNA (-5.33 [1.59]) vs. PBO+ETV (-4.20 [0.98]; p = 0.0084). Greater mean reductions in pregenomic RNA were observed at Week 12 and 24 in patients receiving VBR+ETV vs. PBO+ETV (p <0.0001 and p <0.0001). Changes in viral antigens were similar in both groups. No drug interaction between VBR and ETV was observed. Two patients experienced HBV DNA rebound during treatment, with no resistance breakthrough detected. The safety of VBR+ETV was similar to PBO+ETV. All treatment-emergent adverse events and laboratory abnormalities were Grade 1/2. There were no deaths, serious adverse events, or evidence of drug-induced liver injury.

CONCLUSIONS

In this 24-week study, VBR+ETV provided additive antiviral activity over PBO+ETV in treatment-naïve patients with cHBV, with a favourable safety and tolerability profile.

CLINICAL TRIAL NUMBER

NCT03577171 LAY SUMMARY: Hepatitis B is a long-lasting viral infection of the liver. Current treatments can suppress hepatitis B virus but do not offer the opportunity of cure, hence, new treatment approaches are required. Herein, we show that the combination of the novel core inhibitor vebicorvir with an existing antiviral (entecavir) in treatment-naïve patients chronically infected with hepatitis B virus demonstrated greater antiviral activity than entecavir alone. Additionally, vebicorvir was safe and well tolerated. Thus, further studies evaluating its potential role in the treatment of chronic hepatitis B are warranted.

Discovery and preclinical evaluations of GST-HG131, a novel HBV antigen inhibitor for the treatment of chronic hepatitis B infection

Chronic hepatitis B (CHB) remains a significant health challenge worldwide. The current treatments for CHB achieve less than 10% cure rates, majority of the patients are on therapy for life. Therefore, cure of CHB is a high unmet medical need. HBV surface antigen (HBsAg) loss and seroconversion are considered as the key for the cure. RG7834 is a novel, orally bioavailable small molecule reported to reduce HBV antigens. Based on RG7834 chemistry, we designed and discovered a series of dihydrobenzopyridooxazepine (DBP) series of HBV antigen inhibitors. Extensive SAR studies led us to GST-HG131 with excellent reduction of HBV antigens (both HBsAg and HBeAg) in vitro and in vivo. GST-HG131 improved safety in rat toxicology studies over RG7834. The promising inhibitory activity, together with animal safety enhancement, merited GST-HG131 progressed into clinical development in 2020 (NCT04499443).

Discovery and Antiviral Profile of New Sulfamoylbenzamide Derivatives as HBV Capsid Assembly Modulators

Chronic hepatitis B (CHB) is a major worldwide public health problem and novel anti-HBV therapies preventing liver disease progression to cirrhosis and hepatocellular carcinoma are urgently needed. Over the last several years, capsid assembly modulators (CAM) have emerged as clinically effective anti-HBV agents which can inhibit HBV replication in CHB patients. As part of a drug discovery program aimed at obtaining novel CAM endowed with high in vitro and in vivo antiviral activity, we identified a novel series of sulfamoylbenzamide (SBA) derivatives. Compound 10, one of the most in vitro potent SBA-derived CAM discovered to date, showed excellent pharmacokinetics in mice suitable for oral dosing. When studied in a transgenic mouse model of hepatic HBV replication, it was considerably more potent than NVR 3-778, the first sulfamoylbenzamide (SBA) CAM that entered clinical trials for CHB, at reducing viral replication in a dose-dependent fashion. We present herein the discovery process, the SAR analysis and the pre-clinical profile of this novel SBA CAM.

Discovery of SHR5133, a Highly Potent and Novel HBV Capsid Assembly Modulator

Capsid assembly modulators (CpAMs) represent a new class of antivirals targeting hepatitis B virus (HBV) core protein to disrupt the assembly process. In this work, a novel chemotype featuring a fused heterocycle amide was discovered through pharmacophore exploration. Lead optimization resulted in compound 8 with an EC₅₀ value of 511 nM, and then methyl substitution on the piperazine was found to improve the in vitro potency remarkably. Further SAR studies established the key compound SHR5133, which showed high in vitro antiviral potency, favorable pharmacokinetic profiles across species, and robust in vivo efficacy.

Anti-viral triterpenes: a review

Triterpenes are naturally occurring derivatives biosynthesized following the isoprene rule of Ruzicka. The triterpenes have been reported to possess a wide range of therapeutic applications including anti-viral properties. In this review, the recent studies (2010-2020) concerning the anti-viral activities of triterpenes have been summarized. The structure activity relationship studies have been described as well as brief biosynthesis of these triterpenes is discussed.

Disassembly of Single Virus Capsids Monitored in Real Time with Multicycle Resistive-Pulse Sensing

Virus assembly and disassembly are critical steps in the virus lifecycle; however, virus disassembly is much less well understood than assembly. For hepatitis B virus (HBV) capsids, disassembly of the virus capsid in the presence of guanidine hydrochloride (GuHCl) exhibits strong hysteresis that requires additional chemical energy to initiate disassembly and disrupt the capsid structure. To study disassembly of HBV capsids, we mixed T = 4 HBV capsids with 1.0-3.0 M GuHCl, monitored the reaction over time by randomly selecting particles, and measured their size with resistive-pulse sensing. Particles were cycled forward and backward multiple times to increase the observation time and likelihood of observing a disassembly event. The four-pore device used for resistive-pulse sensing produces four current pulses for each particle during translocation that improves tracking and identification of single particles and increases the precision of particle-size measurements when pulses are averaged. We studied disassembly at GuHCl concentrations below and above denaturing conditions of the dimer, the fundamental unit of HBV capsid assembly. As expected, capsids showed little disassembly at low GuHCl concentrations (e.g., 1.0 M GuHCl), whereas at higher GuHCl concentrations (≥1.5 M), capsids exhibited disassembly, sometimes as a complex series of events. In all cases, disassembly was an accelerating process, where capsids catastrophically disassembled within a few 100 ms of reaching critical stability; disassembly rates reached tens of dimers per second just before capsids fell apart. Some disassembly events exhibited metastable intermediates that appeared to lose one or more trimers of dimers in a stepwise fashion.

Cellular Id1 inhibits hepatitis B virus transcription by interacting with the novel covalently closed circular DNA-binding protein E2F4

Hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC), which required developing novel therapies targeting the inhibition of HBV transcription and replication due to current limited treatment options. We explored novel target for the development of novel therapies targeting the inhibition of HBV replication and transcription. The expression of Id1 and E2F4 in HCC cells and tissues was detected by qRT-PCR and western blot. We investigated the Id1 and E2F4-mediated transcription of HBV infection by using HepG2.2.15, HepAD38, HepG2-NTCP cell lines and AAV/HBV-infected mice. Interactions between the two host proteins and viral covalently closed circular DNA (cccDNA) were assessed using subcellular localization, protein-protein interaction, chromatin immunoprecipitation, and luciferase assays. Ectopic Id1 significantly reduced HBV transcription and replication in both HBV-expressing cells and AAV/HBV-infected mice. Id1 and E2F4 could form a heterodimer to prevent E2F4 from promoting HBV transcription and replication. E2F4 could directly bind to cccDNA and activate the HBV core promoter in cell lines. Furthermore, in vitro binding experiments confirmed that the sequence 1758'-TTAAAGGTC-1766', which is highly conserved among HBV genotypes, is the target site of the E2F4 homodimer. The findings suggest that E2F4 function as novel cccDNA-binding protein to directly activate HBV transcription by binding to Cp promoter region. Our results highlight the ability that E2F4 represent a pan-potential therapeutic target against HBV transcription and provide more clues to better understand the life cycle of HBV.

A Missense Variant in Granulysin is Associated with the Efficacy of Pegylated-Interferon-Alpha Therapy in Chinese Patients with HBeAg-Positive Chronic Hepatitis B

Purpose

Granulysin (GNLY) is a cytotoxic granule that has been reported to have various antimicrobial activities. We evaluated the association between a missense variant in GNLY (rs11127) and treatment efficacy of pegylated interferon-alpha (PegIFNα) or nucleos(t)ide analogs (NUCs) in patients with chronic hepatitis B (CHB).

Patients and Methods

We included a total of 1823 patients with hepatitis B e antigen (HBeAg)-positive CHB (954 patients treated with PegIFNα and 869 patients treated with NUCs) in four Phase IV multicenter randomized controlled trials. The association of the GNLY rs11127 genotype with the combined response (CR), defined as HBeAg seroconversion and hepatitis B virus (HBV) DNA level <2000 IU/mL was evaluated. A polygenic score (PGS) was constructed to evaluate the cumulative effect of multiple single-nucleotide polymorphisms (SNPs), including rs11127 and several other SNPs, STAT4 rs7574865, CFB rs12614, and CD55 rs28371597, which were reported to be associated with CR.

Results

GNLY rs11127 was significantly associated with CR in patients treated with PegIFNα. The CR rate in patients with the rs11127 CC genotype was higher than that with the CT or TT genotype (40.98% vs 30.34% or 27.09%, P = 0.003). Furthermore, a PGS integrating GNLY rs11127 and three other SNPs was significantly associated with CR in PegIFNα-treated patients (P < 0.001). However, no significant correlation was found between GNLY rs11127 and CR in NUCs-treated patients.

Conclusion

GNLY rs11127 is an independent biomarker for predicting the response to PegIFNα therapy in HBeAg-positive CHB patients. Furthermore, the PGS, including GNLY rs11127, provides new insights for individualized treatment in clinical practice.

Identification of (6S)-cyclopropyl-6,7-dihydropyrazolo[1,5-a]pyrazine-5(4H)-carboxamines as new HBV capsid assembly modulators

GYH2-18 is a type II HBV CAM with 6,7-dihydropyrazolo[1,5-a]pyrazine-5(4H)-carboxamine (DPPC) skeleton discovered by Roche INC. A series of GYH2-18 derivatives were designed, synthesized and evaluated for their anti-HBV activity. Two compounds 2f and 3k exhibited excellent anti-HBV activity, low cytotoxicity and accepted oral PK profiles. Chiral separation of 2f and 3k was conducted successfully, and (6S)-cyclopropyl DPPC isomers 2f-1, 2f-3, 3k-1 and 3k-3 were identified to be much more active than the corresponding (6R)-ones. The preliminary structure-activity relationship, particle gel assay and molecular modeling studies were also discussed, which provide useful indications for guiding the further rational design of new (6S)-cyclopropyl DPPC analogues.

Acetophenone 4-nitrophenylhydrazone inhibits Hepatitis B virus replication by modulating capsid assembly

Hepatitis B virus (HBV) is the causative agent of chronic liver disease and is correlated with the development of subsequent hepatic cirrhosis and hepatocellular carcinoma. Current antiviral therapy using nucleos(t)ide analogs is effective in suppressing viral replication and interrupting disease progression, but HBV is rarely cured completely. Thus, there remains an unmet need for the development of novel anti-HBV drugs. Here, we report the identification of N-(4-Nitrophenyl)-1-phenylethanone hydrazone (ANPH) as a novel structural class of selective inhibitors targeting the replication of the HBV genome using adenovirus vector-mediated HBV genome transduction. ANPH inhibited viral genome replication in HepG2.2.15 cells by inducing the formation of empty capsids devoid of pregenomic RNA without affecting its transcription and translation. Biochemical assays using a truncated core protein consisting of the assembly domain showed that ANPH accelerates the formation of morphologically intact capsids. Taken together, we propose that ANPH might provide a new structural scaffold to design a new anti-HBV drug in medicinal chemistry as well as chemical probes for HBV core protein functions in the future.

Immunotherapy and Gene Therapy for Oncoviruses Infections: A Review

Immunotherapy has been shown to be highly effective in some types of cancer caused by viruses. Gene therapy involves insertion or modification of a therapeutic gene, to correct for inappropriate gene products that cause/may cause diseases. Both these types of therapy have been used as alternative ways to avoid cancers caused by oncoviruses. In this review, we summarize recent studies on immunotherapy and gene therapy including the topics of oncolytic immunotherapy, immune checkpoint inhibitors, gene replacement, antisense oligonucleotides, RNA interference, clustered regularly interspaced short palindromic repeats Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based gene editing, transcription activator-like effector nucleases (TALENs) and custom treatment for Epstein-Barr virus, human T-lymphotropic virus 1, hepatitis B virus, human papillomavirus, hepatitis C virus, herpesvirus associated with Kaposi's sarcoma, Merkel cell polyomavirus, and cytomegalovirus.

Recent Advances in Hepatitis B Treatment

Hepatitis B virus infection affects over 250 million chronic carriers, causing more than 800,000 deaths annually, although a safe and effective vaccine is available. Currently used antiviral agents, pegylated interferon and nucleos(t)ide analogues, have major drawbacks and fail to completely eradicate the virus from infected cells. Thus, achieving a "functional cure" of the infection remains a real challenge. Recent findings concerning the viral replication cycle have led to development of novel therapeutic approaches including viral entry inhibitors, epigenetic control of cccDNA, immune modulators, RNA interference techniques, ribonuclease H inhibitors, and capsid assembly modulators. Promising preclinical results have been obtained, and the leading molecules under development have entered clinical evaluation. This review summarizes the key steps of the HBV life cycle, examines the currently approved anti-HBV drugs, and analyzes novel HBV treatment regimens.

Discovery of novel HBV capsid assembly modulators by structure-based virtual screening and bioassays

HBV capsid assembly has been regarded as an attractive potential target for anti-HBV therapy. In this study, we discovery the Novel HBV capsid assembly modulators (CAMs) through structure-based virtual screening and bioassays. A total of 16 structurally diverse compounds were purchased and assayed, including three compounds with inhibition rate > 50% at 20 μM. Further lead optimization based on the most potent compound II-1-7 (EC₅₀ = 5.6 ± 0.1 µM) were performed by using substructure searching strategy, resulting in compound II-2-9 with an EC₅₀ value of 1.8 ± 0.6 μM. In bimolecular fluorescence complementation (BiFC) assay, compound II-2-9 inhibited the HBV by disrupting the HBV capsid interactions. In summary, this study provides a highly efficient way to discover novel CAMs, and 2-aryl-4-quinolyl amide derivatives could serve as the starting point for development of novel anti-HBV drugs.

New therapeutic options for persistent low-level viremia in patients with chronic hepatitis B virus infection: Increase of entecavir dosage

Chronic hepatitis B virus (HBV) infection (CHB) is a public health concern worldwide. Current therapies utilizing nucleos(t)ide analogs (NA) have not resulted in a complete cure for CHB. Furthermore, patients on long-term NA treatment often develop low-level viremia (LLV). Persistent LLV, in addition to causing the progression of liver disease or hepatocellular carcinoma, may shed light on the current plight of NA therapy. Here, we review the literature on LLV, NA treatment, and various doses of entecavir to find a strategy for improving the efficacy of this antiviral agent. For LLV patients, three therapeutic options are available, switching to another antiviral monotherapy, interferon-α switching therapy, and continuing monotherapy. In real-world clinical practice, entecavir overdose has been used in antiviral therapy for CHB patients with NA refractory and persistent LLV, which encouraged us to conduct further in-depth literature survey on dosage and duration related entecavir studies. The studies of pharmacodynamics and pharmacokinetics show that entecavir has the maximal selected index for safety, and has great potential in inhibiting HBV replication, in all of the NAs. In the particular section of the drug approval package published by the United States Food and Drug Administration, entecavir doses 2.5-20 mg/d do not increase adverse events, and entecavir doses higher than 1.0 mg/d might improve the antiviral efficacy. The literature survey led us to two suggestions: (1) Increasing entecavir dose to 1.0 mg/d for the treatment of NA naïve patients with HBV DNA >2 × 10⁶ IU/mL is feasible and would provide better prognosis; and (2) Further research is needed to assess the long-term toxic effects of higher entecavir doses (2.5 and 5.0 mg/d), which may prove beneficial in treating patients with prior NA treatment, partial virological response, or LLV state.

Medicinal chemistry strategies for discovering antivirals effective against drug-resistant viruses

During the last forty years we have witnessed impressive advances in the field of antiviral drug discovery culminating with the introduction of therapies able to stop human immunodeficiency virus (HIV) replication, or cure hepatitis C virus infections in people suffering from liver disease. However, there are important viral diseases without effective treatments, and the emergence of drug resistance threatens the efficacy of successful therapies used today. In this review, we discuss strategies to discover antiviral compounds specifically designed to combat drug resistance. Currently, efforts in this field are focused on targeted proteins (e.g. multi-target drug design strategies), but also on drug conformation (either improving drug positioning in the binding pocket or introducing conformational constraints), in the introduction or exploitation of new binding sites, or in strengthening interaction forces through the introduction of multiple hydrogen bonds, covalent binding, halogen bonds, additional van der Waals forces or multivalent binding. Among the new developments, proteolysis targeting chimeras (PROTACs) have emerged as a valid approach taking advantage of intracellular mechanisms involving protein degradation by the ubiquitin-proteasome system. Finally, several molecules targeting host factors (e.g. human dihydroorotate dehydrogenase and DEAD-box polypeptide 3) have been identified as broad-spectrum antiviral compounds. Implementation of herein described medicinal chemistry strategies are expected to contribute to the discovery of new drugs effective against current and future threats due to emerging and re-emerging viral pandemics.

2,5-dimethylcelecoxib improves immune microenvironment of hepatocellular carcinoma by promoting ubiquitination of HBx-induced PD-L1

Background

2,5-dimethylcelecoxib (DMC) is a targeted inhibitor of microsomal prostaglandin E synthase-1 (mPGES-1), a key enzyme in the PGE2 synthesis pathway of inflammatory mediators. Previous studies have confirmed that DMC can inhibit the growth of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). However, it is not known whether DMC is involved in the changes of tumor immune microenvironment.

Methods

In this study, we explored the effects of DMC on HBV-related HCC immune microenvironment, and deeply analyzed its unique effect and mechanism on programmed death receptor 1 (PD-1)/and its ligand 1 (PD-L1) pathway.

Results

Clinical hepatoma tissues detection showed that compared with non-virus-related HCC, the level of CD8 of HBV-related HCC was significantly lower, while the levels of PD-L1 and CD163 were higher. In vivo experiments indicated that DMC could increase the level of tumor infiltrating CD8⁺ T cells in hepatitis B virus X (HBx) (+) hepatoma cells implanted mouse models, and inhibit the expression of PD-L1 and CD163 in tumor tissues. DMC combined with atezolizumab had more significant antitumor effect and stronger blocking effect on PD-1/PD-L1 pathway. Mechanism studies have shown that DMC can promote ubiquitin degradation of HBx-induced PD-L1 protein in HCC cells by activating adenosine 5′-monophosphate-activated protein kinase pathway. Further experiments confirmed that this process was mainly mediated by E3 ligase RBX1.

Conclusions

Our results uncover a role for DMC in promoting HBV-related HCC immune microenvironment, which not only enrich the relationship between inflammatory factors (mPGES-1/PGE2 pathway) and immunosuppression (PD-L1), but also provide an important strategic reference for multitarget or combined immunotherapy of HBV-related HCC.

3,7-Dihydroxytropolones Inhibit Initiation of Hepatitis B Virus Minus-Strand DNA Synthesis

Initiation of protein-primed (-) strand DNA synthesis in hepatitis B virus (HBV) requires interaction of the viral reverse transcriptase with epsilon (ε), a cis-acting regulatory signal located at the 5' terminus of pre-genomic RNA (pgRNA), and several host-encoded chaperone proteins. Binding of the viral polymerase (P protein) to ε is necessary for pgRNA encapsidation and synthesis of a short primer covalently attached to its terminal domain. Although we identified small molecules that recognize HBV ε RNA, these failed to inhibit protein-primed DNA synthesis. However, since initiation of HBV (-) strand DNA synthesis occurs within a complex of viral and host components (e.g., Hsp90, DDX3 and APOBEC3G), we considered an alternative therapeutic strategy of allosteric inhibition by disrupting the initiation complex or modifying its topology. To this end, we show here that 3,7-dihydroxytropolones (3,7-dHTs) can inhibit HBV protein-primed DNA synthesis. Since DNA polymerase activity of a ribonuclease (RNase H)-deficient HBV reverse transcriptase that otherwise retains DNA polymerase function is also abrogated, this eliminates direct involvement of RNase (ribonuclease) H activity of HBV reverse transcriptase and supports the notion that the HBV initiation complex might be therapeutically targeted. Modeling studies also provide a rationale for preferential activity of 3,7-dHTs over structurally related α-hydroxytropolones (α-HTs).

Discovery and optimizing polycyclic pyridone compounds as anti-HBV agents

INTRODUCTION

Hepatitis B disease is caused by the hepatitis B virus (HBV), which is a DNA virus that belongs to the Hepadnaviridae family. It is a considerable health burden, with 257 million active cases globally. Long-standing infection may create a fundamental cause of liver disease and chronic infections, including cirrhosis, hepatocellular, and carcinoma liver failure. There is an urgent need to develop novel, safe, and effective drug candidates with a novel mechanism of action, improved activity, efficacy, and cure rate.

AREAS COVERED

Herein, the authors provide a concise report focusing on a general and cutting-edge overview of the current state of polycyclic pyridone-related anti-HBV agent patents from 2016 to 2018 and some future perspectives.

EXPERT OPINION

In medicinal chemistry, high-throughput screening (HTS), hit-to-lead optimization (H2L), bioisosteric replacement, and scaffold hopping approaches are playing a major role in the discovery and development of HBV inhibitors. Developing polycyclic pyridone-related anti-HBV agents that could target host factors has attracted significant interest and attention in recent years.

Orchestration of Intracellular Circuits by G Protein-Coupled Receptor 39 for Hepatitis B Virus Proliferation

Hepatitis B virus (HBV), a highly persistent pathogen causing hepatocellular carcinoma (HCC), takes full advantage of host machinery, presenting therapeutic targets. Here we aimed to identify novel druggable host cellular factors using the reporter HBV we have recently generated. In an RNAi screen of G protein-coupled receptors (GPCRs), GPCR39 (GPR39) appeared as the top hit to facilitate HBV proliferation. Lentiviral overexpression of active GPR39 proteins and an agonist enhanced HBV replication and transcriptional activities of viral promoters, inducing the expression of CCAAT/enhancer binding protein (CEBP)-β (CEBPB). Meanwhile, GPR39 was uncovered to activate the heat shock response, upregulating the expression of proviral heat shock proteins (HSPs). In addition, glioma-associated oncogene homologue signaling, a recently reported target of GPR39, was suggested to inhibit HBV replication and eventually suppress expression of CEBPB and HSPs. Thus, GPR39 provirally governed intracellular circuits simultaneously affecting the carcinopathogenetic gene functions. GPR39 and the regulated signaling networks would serve as antiviral targets, and strategies with selective inhibitors of GPR39 functions can develop host-targeted antiviral therapies preventing HCC.

Impact of HEC72702 chirality on the selective inhibition of hepatitis B virus capsid dimer: A dynamics-structure-energetics perspective

Chirality in drug design has been attracting wide interests and attention over the years based on its innate potentials of enhancing the selectivity and prowess of therapeutic molecules. This approach was fundamental to the recent design of two inhibitors, where (R,R)-HEC72702 exhibited higher potency inhibition against hepatitis B virus capsid (HBVC) than (R,S)-HEC72702. Nevertheless, the detailed molecular mechanism has remained unresolved. Here, we apply multiple computational approaches to explore, validate, and differentiate the binding modes of (R,R) and (R,S)-HEC72702 and to explain the systematic roles mediated by chirality on the distinctive inhibition of HBVC dimer (HBVCd). Our findings revealed that chirality change from R,S to R,R engenders variations in the position of the propanoic acid group of HEC72702 toward the α5' and C-TER' region of HBVCd chain B which could explain the higher inhibitory affinity of (R,R)-HEC72702. Estimated binding free energies revealed a good correlation with bioactivity data. Moreover, analysis of energy decomposition revealed the prominent effects of van der Waals interactions in the binding process of both compounds to HBVCd. Furthermore, hierarchical clustering of residue-based energetic contributions suggested two hot-spot residues W125´ and F156´ play crucial roles in the systematic motions of the propanoic acid group toward chain B.

Discovery of Phthalazinone Derivatives as Novel Hepatitis B Virus Capsid Inhibitors

HBV capsid assembly has been viewed as an attractive target for new antiviral therapies against HBV. On the basis of a lead compound 4r, we further investigated this target to identify novel active compounds with appropriate anti-HBV potencies and improved pharmacokinetic (PK) properties. Structure-activity relationship studies based on metabolic pathways of 4r led to the identification of a phthalazinone derivative 19f with appropriate anti-HBV potencies (IC₅₀ = 0.014 ± 0.004 μM in vitro), which demonstrated high oral bioavailability and liver exposure. In the AAV-HBV/mouse model, administration of 19f resulted in a 2.67 log reduction of the HBV DNA viral load during a 4-week treatment with 150 mg/kg dosing twice daily.

[New Potential Therapies for Chronic Hepatitis B]

A HBV infection is a dynamic disease and long-term liver inflammation contributes to the development of liver cirrhosis and hepatocellular carcinoma. Currently available nucleos(t)ide analogues and pegylated interferon are effective in inhibiting HBV replication but rarely achieve HBsAg clearance. The present article introduces a new definition of HBV cure and several emerging therapies for HBV cure, including direct acting antivirals and immune modulatory antivirals.

Amino acid prodrugs of NVR3-778: Design, synthesis and anti-HBV activity

A series of amino acid prodrugs of NVR3-778, a potent anti-HBV candidate currently under phase II clinical trial, were designed and synthesized as new anti-HBV agents. Except for 1e, all of them displayed roughly comparable anti-HBV activity (IC₅₀, 0.28-0.56 µM) to NVR3-778 (IC₅₀, 0.26 µM). Compound 1a, a l-valine ester prodrug of NVR3-778, was found to show significantly improved water solubility (0.7 mg/mL, pH 2) as we expected, and lower cytotoxicity (CC₅₀ > 10 µM) than NVR3-778 (CC₅₀, 4.81 µM). Moreover, 1a also exhibited acceptable PK properties and comparable in vivo efficacy in HBV DNA hydrodynamic mouse model to that of NVR3-778, suggesting it may serve as a promising lead compound for further anti-HBV drug discovery.

A missense variant in complement factor B (CFB) is a potential predictor of 24-week off-treatment response to PegIFNα therapy in Chinese HBeAg-positive chronic hepatitis B patients

BACKGROUND

To date, 14 single-nucleotide polymorphisms (SNPs) have been identified as susceptibility loci for chronic hepatitis B (CHB).

AIM

To investigate if these SNPs are associated with treatment response of hepatitis B e antigen (HBeAg)-positive CHB patients.

METHODS

We performed a retrospective analysis of 1623 Han Chinese HBeAg-positive CHB patients (782 patients treated with pegylated interferon alpha [PegIFNα] for 48 weeks plus 24 weeks follow-up, and 841 patients treated with nucleos(t)ide analogues [NUCs] for 104 weeks) included in four phase-IV multicentre randomised controlled trials. All 14 SNPs were genotyped for each CHB patient. A polygenic score (PGS) was used to evaluate the cumulative effect of multiple SNPs. The associations of SNPs or PGS with combined response (CR) and hepatitis B s antigen (HBsAg) loss were assessed.

RESULTS

We found that rs12614, a missense variant of complement factor B (CFB), was significantly associated with CR in PegIFNα-treated patients, and the CR rate in patients with the rs12614 TT/CT genotype was less than one-third of that in patients with the CC genotype (7.4% vs 22.6%, P = 0.009). Moreover, a PGS integrating CFB rs12614 and STAT4 rs7574865 (previously reported to be associated with response to PegIFNα) was significantly associated with both CR (P-trend = 4.000 × 10^-4 ) and HBsAg loss (P-trend = 0.010) in PegIFNα-treated patients. However, none of the SNPs were associated with treatment response in NUCs-treated patients.

CONCLUSIONS

CFB rs12614 is an independent predictor of response to PegIFNα therapy in Chinese HBeAg-positive CHB patients. A PGS integrating CFB rs12614 with STAT4 rs7574865 can effectively discriminate responders to PegIFNα from nonresponders.

Variants in STAT4 Associated With Cure of Chronic HBV Infection in HBeAg-positive Patients Treated With Pegylated Interferon-alpha

BACKGROUND & AIMS

Variants in STAT4 (rs7574865) have been associated with seroconversion to hepatitis B e antigen (HBeAg) and reduction in levels of hepatitis B virus (HBV) DNA in patients with chronic infection treated with interferon alpha (IFNA). We evaluated the associations among rs7574865, loss of HB surface antigen (HBsAg, a marker of functional cure of HBV infection), and response to treatment with pegylated IFNA (PegIFN) or nucleos(t)ide analogues (NUCs) in HBeAg-positive patients with chronic HBV infection.

METHODS

We performed a retrospective analysis of 1823 HBeAg-positive patients with chronic HBV infection (954 patients treated with PegIFN and 869 patients treated with NUCs) included in 4 phase-4 multicenter randomized controlled trials. The Cochran-Armitage trend test was used to evaluate the association of rs7574865 genotype with combined response (CR, defined as HBeAg seroconversion and HBV DNA level <2000 IU/mL) and loss of HBsAg at week 72, for patients given PegIFN, or week 104, for patients given NUCs.

RESULTS

We found a significant association between rs7574865 genotype and CR (P = .004) and loss of HBsAg (P = .037) in patients treated with PegIFN. In patients with HBV genotype B infection, 43.6% of those with rs7574865 TT achieved a CR, compared to patients with rs7574865 GG (20.5%), and 7.7% had loss of HBsAg, compared to 1.9% of patients with rs7574865 GG. However, in patients treated with NUCs, we found no association of rs7574865 genotype with CR (P = .811) or loss of HBsAg (P=.439).

CONCLUSIONS

In a retrospective analysis of data from 4 clinical trials, we found rs7574865 in STAT4 to be associated with functional cure of chronic HBV infection by PegIFN treatment, but not NUCs treatment, in HBeAg-positive patients with HBV genotype B infection.

Ribonuclease H, an unexploited target for antiviral intervention against HIV and hepatitis B virus

Ribonucleases H (RNases H) are endonucleolytic enzymes, evolutionarily related to retroviral integrases, DNA transposases, resolvases and numerous nucleases. RNases H cleave RNA in RNA/DNA hybrids and their activity plays an important role in the replication of prokaryotic and eukaryotic genomes, as well as in the replication of reverse-transcribing viruses. During reverse transcription, the RNase H activity of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) degrades the viral genomic RNA to facilitate the synthesis of viral double-stranded DNA. HIV and HBV reverse transcriptases contain DNA polymerase and RNase H domains that act in a coordinated manner to produce double-stranded viral DNA. Although RNase H inhibitors have not been developed into licensed drugs, recent progress has led to the identification of a number of small molecules with inhibitory activity at low micromolar or even nanomolar concentrations. These compounds can be classified into metal-chelating active site inhibitors and allosteric inhibitors. Among them, α-hydroxytropolones, N-hydroxyisoquinolinediones and N-hydroxypyridinediones represent chemotypes active against both HIV and HBV RNases H. In this review we summarize recent developments in the field including the identification of novel RNase H inhibitors, compounds with dual inhibitory activity, broad specificity and efforts to decrease their toxicity.

Discovery of New Hepatitis B Virus Capsid Assembly Modulators by an Optimal High-Throughput Cell-Based Assay

In this article, a simple and effective high-throughput screening (HTS) assay was developed to identify anti-HBV compounds by using a HepAD38 luciferase reporter (HepAD38-luc) cell line that can effectively exclude the false positive hit compounds targeted on the tetracycline off (tet-off) regulation system. Through screening in-house chemical libraries, N-phenylpiperidine-3-carboxamide derivatives, represented by 1 and 2, were identified, while the other false positive hits (i.e., quinoxaline (3) and benzothiazin (4) derivatives) were simultaneously excluded. Compounds 1 and 2 exhibit strong inhibitory activity against HBV replication in both HepAD38 and HepG2.2.15 cells. Further studies revealed that 1 and 2 reduced extracellular HBV DNA, HBeAg, and intracellular HBV intermediates, including total DNA, RNA, and precore RNA of HBV. Size-exclusion chromatography (SEC) and electron microscopy (EM) investigations demonstrated that 1 and 2 remarkably induced the formation of morphologically intact capsids and accelerated the dynamics of capsid assembly, suggesting that both 1 and 2 were type I capsid assembly modulators (CAMs).

Evolution of Intermediates during Capsid Assembly of Hepatitis B Virus with Phenylpropenamide-Based Antivirals

Self-assembly of virus capsids is a potential target for antivirals due to its importance in the virus lifecycle. Here, we investigate the effect of phenylpropenamide derivatives B-21 and AT-130 on the assembly of hepatitis B virus (HBV) core protein. Phenylpropenamides are widely believed to yield assembly of spherical particles resembling native, empty HBV capsids. Because the details of assembly can be overlooked with ensemble measurements, we performed resistive-pulse sensing on nanofluidic devices with four pores in series to characterize the size distributions of the products in real time. With its single particle sensitivity and compatibility with typical assembly buffers, resistive-pulse sensing is well-suited for analyzing virus assembly in vitro. We observed that assembly with B-21 and AT-130 produced a large fraction of partially complete virus particles that may be on-path, off-path, or trapped. For both B-21 and AT-130, capsid assembly was more sensitive to disruption under conditions where the interprotein association energy was low at lower salt concentrations. Dilution of the reaction solutions led to the rearrangement of the incomplete particles and demonstrated that these large intermediates may be on-path, but are labile, and exist in a frustrated dynamic equilibrium. During capsid assembly, phenylpropenamide molecules modestly increase the association energy of dimers, prevent intermediates from dissociating, and lead to kinetic trapping where the formation of too many capsids has been initiated, which results in both empty and incomplete particles.

Novel Hepatitis B Virus Capsid-Targeting Antiviral That Aggregates Core Particles and Inhibits Nuclear Entry of Viral Cores

An estimated 240 million are chronically infected with hepatitis B virus (HBV), which can lead to liver disease, cirrhosis, and hepatocellular carcinoma. Currently, HBV treatment options include only nucleoside reverse transcriptase inhibitors and the immunomodulatory agent interferon alpha, and these treatments are generally not curative. New treatments with novel mechanisms of action, therefore, are highly desired for HBV therapy. The viral core protein (Cp) has gained attention as a possible therapeutic target because of its vital roles in the HBV life cycle. Several classes of capsid assembly effectors (CAEs) have been described in detail, and these compounds all increase capsid assembly rate but inhibit HBV replication by different mechanisms. In this study, we have developed a thermal shift-based screening method for CAE discovery and characterization, filling a much-needed gap in high-throughput screening methods for capsid-targeting molecules. Using this approach followed by cell-based screening, we identified the compound HF9C6 as a CAE with low micromolar potency against HBV replication. HF9C6 caused large multicapsid aggregates when capsids were assembled in vitro and analyzed by transmission electron microscopy. Interestingly, when HBV-expressing cells were treated with HF9C6, Cp was excluded from cell nuclei, suggesting that this compound may inhibit nuclear entry of Cp and capsids. Furthermore, mutational scanning of Cp suggested that HF9C6 binds the known CAE binding pocket, indicating that key Cp-compound interactions within this pocket have a role in determining the CAE mechanism of action.

Treatment of Chronic Hepatitis B Virus Infection Using Small Molecule Modulators of Nucleocapsid Assembly: Recent Advances and Perspectives

On the basis of the recent advance of basic research on molecular biology of hepatitis B virus (HBV) infection, novel antiviral drugs targeting various steps of the HBV life cycle have been developed in recent years. HBV nucleocapsid assembly is now recognized as a hot target for anti-HBV drug development. Structural and functional analysis of HBV nucleocapsid allowed rational design and improvement of small molecules with the ability to interact with the components of HBV nucleocapsid and modulate the viral nucleocapsid assembly process. Prototypes of small molecule modulators targeting HBV nucleocapsid assembly are being preclinically tested or have moved forward in clinical trials, with promising results. This Review summarizes the recent advances in the approach to develop antiviral drugs based on the modulation of HBV nucleocapsid assembly. The antiviral mechanisms of small molecule modulators beyond the capsid formation and the potential implications will be discussed.

Assessment of quinazolinone derivatives as novel non-nucleoside hepatitis B virus inhibitors

Hepatitis B virus (HBV) infection is a worldwide public health issue. Search for novel non-nucleoside anti-HBV agents is of great importance. In the present study, a series of quinazolinones derivatives (4a-t and 5a-f) were synthesized and evaluated as novel anti-HBV agents. Among them, compounds 5e and 5f could significantly inhibit HBV DNA replication with IC₅₀ values of 1.54 μM and 0.71 μM, respectively. Interestingly, the selective index values of 5f was higher than that of lead compound K284-1405, suggesting 5f possessed relatively safety profile than K284-1405. Notably, 5e and 5f exhibited remarkably anti-HBV activities against lamivudine and entecavir resistant HBV strain with IC₅₀ values of 1.90 and 0.84 μM, confirming their effectiveness against resistant HBV strain. In addition, molecular docking studies indicated that compounds 5e and 5f could well fit into the dimer-dimer interface of HBV core protein dominated by hydrophobic interactions. Notably, their binding modes were different from the lead compound K284-1405, which may be attributed to the additional substituent groups in the quinazolinone scaffold. Taken together, 5e and 5f possessed novel chemical structure and potent anti-HBV activity against both drug sensitive and resistant HBV strains, thus warranting further research as potential non-nucleoside anti-HBV candidates.