In vivo reduction of hepatitis B virus antigenemia and viremia by antisense oligonucleotides

Localization of unlabeled bepirovirsen antisense oligonucleotide in murine tissues using in situ hybridization and CARS imaging

Current methods for detecting unlabeled antisense oligonucleotide (ASO) drugs rely on immunohistochemistry (IHC) and/or conjugated molecules, which lack sufficient sensitivity, specificity, and resolution to fully investigate their biodistribution. Our aim was to demonstrate the qualitative and quantitative distribution of unlabeled bepirovirsen, a clinical stage ASO, in livers and kidneys of dosed mice using novel staining and imaging technologies at subcellular resolution. ASOs were detected in formalin-fixed paraffin-embedded (FFPE) and frozen tissues using an automated chromogenic in situ hybridization (ISH) assay: miRNAscope. This was then combined with immunohistochemical detection of cell lineage markers. ASO distribution in hepatocytes versus nonparenchymal cell lineages was quantified using HALO AI image analysis. To complement this, hyperspectral coherent anti-Stokes Raman scattering (HS-CARS) imaging microscopy was used to specifically detect the unique cellular Raman spectral signatures following ASO treatment. Bepirovirsen was localized primarily in nonparenchymal liver cells and proximal renal tubules. Codetection of ASO with distinct cell lineage markers of liver and kidney populations aided target cell identity facilitating quantification. Positive liver signal was quantified using HALO AI, with 12.9% of the ASO localized to the hepatocytes and 87.1% in nonparenchymal cells. HS-CARS imaging specifically detected ASO fingerprints based on the unique vibrational signatures following unlabeled ASO treatment in a totally nonperturbative manner at subcellular resolution. Together, these novel detection and imaging modalities represent a significant increase in our ability to detect unlabeled ASOs in tissues, demonstrating improved levels of specificity and resolution. These methods help us understand their underlying mechanisms of action and ultimately improve the therapeutic potential of these important drugs for treating globally significant human diseases.

A dual-targeting near-infrared biomimetic drug delivery system for HBV treatment

Hepatitis B virus (HBV) infection is a serious global public health threat. It remains elusive to achieve a functional HBV cure with currently available antivirals. Herein, a photo-responsive delivery vehicle composed of Nd³⁺ -sensitized core-shell upconversion nanoparticle (UCNP), mesoporous silica nanoparticle (MSN), antisense oligonucleotides (ASOs), and capsid-binding inhibitor C39 was established, which was named UMAC according to the initials of its components. Subsequently, the as-synthesized delivery vehicle was encapsulated by β- D-galactopyranoside (Gal) modified red blood cell (RBC) membrane vesicles, which enabled precise targeting of the liver cells (UMAC-M-Gal). Both in vitro and in vivo experiments demonstrated that this biomimetic system could successfully achieve controlled drug release under light conditions at 808 nm, leading to effective suppression of HBV replication in this dual-targeted therapeutic approach. Together, these results substantiate the system has huge prospects for application to achieve functional HBV cure, and provides a promising novel strategy for drug delivery.

Preclinical and Phase 1 Assessment of Antisense Oligonucleotide Bepirovirsen in Hepatitis B Virus-Transgenic Mice and Healthy Human Volunteers: Support for Clinical Dose Selection and Evaluation of Safety, Tolerability, and Pharmacokinetics of Single and Multiple Doses

Dose-dependent reductions in hepatitis B virus (HBV) RNA, DNA, and viral proteins following bepirovirsen administration were observed in HepG2.2.15 cells. In HBV-transgenic mice treated at 50 mg/kg/wk, hepatic HBV RNA and DNA were reduced by 90% and 99%, respectively. Subsequently, a phase 1 first-in-human study assessed pharmacokinetics and tolerability of single (75-450 mg) and multiple (150-450 mg on days 1, 4, 8, 11, 15, and 22) subcutaneous bepirovirsen doses in 96 healthy volunteers. Bepirovirsen at all dose levels was rapidly absorbed (maximum plasma concentration 3-8 hours after dosing), rapidly distributed to peripheral tissues, and slowly eliminated (median plasma terminal half-life: 22.5-24.6 days across cohorts). Plasma exposure (dose-proportional at 150-450 mg) and concentration-time profiles were similar following the first and sixth doses, suggesting little to no plasma accumulation (steady state achieved by day 22). Renal elimination of full-length bepirovirsen accounted for <2% of the total dose. Across the single and multiple dose cohorts, 197 treatment-emergent adverse events were reported, with 99% and 65% classified as mild in severity and local injection site reactions, respectively. In conclusion, bepirovirsen showed an acceptable safety profile in humans with observed pharmacokinetics consistent with the chemical class, warranting further evaluation of bepirovirsen in chronic HBV infection.

Transcriptomics and RNA-Based Therapeutics as Potential Approaches to Manage SARS-CoV-2 Infection

SARS-CoV-2 is a coronavirus family member that appeared in China in December 2019 and caused the disease called COVID-19, which was declared a pandemic in 2020 by the World Health Organization. In recent months, great efforts have been made in the field of basic and clinical research to understand the biology and infection processes of SARS-CoV-2. In particular, transcriptome analysis has contributed to generating new knowledge of the viral sequences and intracellular signaling pathways that regulate the infection and pathogenesis of SARS-CoV-2, generating new information about its biology. Furthermore, transcriptomics approaches including spatial transcriptomics, single-cell transcriptomics and direct RNA sequencing have been used for clinical applications in monitoring, detection, diagnosis, and treatment to generate new clinical predictive models for SARS-CoV-2. Consequently, RNA-based therapeutics and their relationship with SARS-CoV-2 have emerged as promising strategies to battle the SARS-CoV-2 pandemic with the assistance of novel approaches such as CRISPR-CAS, ASOs, and siRNA systems. Lastly, we discuss the importance of precision public health in the management of patients infected with SARS-CoV-2 and establish that the fusion of transcriptomics, RNA-based therapeutics, and precision public health will allow a linkage for developing health systems that facilitate the acquisition of relevant clinical strategies for rapid decision making to assist in the management and treatment of the SARS-CoV-2-infected population to combat this global public health problem.

Surrogate Markers for Hepatitis B Virus Covalently Closed Circular DNA

Chronic infection with the hepatitis B virus (HBV) is one of the most common causes of liver disease worldwide. Chronic HBV infection is currently incurable because of the persistence of the viral template for the viral transcripts, covalently closed circular deoxyribonucleic acid (cccDNA). Detecting changes in cccDNA transcriptional activity is key to understanding fundamental virology, determining the efficacy of new therapies, and deciding the optimal clinical management of HBV patients. In this review, we summarize surrogate circulating biomarkers that have been used to infer cccDNA levels and activity in people with chronic hepatitis B. Moreover, we outline the current shortcomings of the current biomarkers and highlight the clinical importance in improving them and expanding their use.

Viral hepatitis: Past, present, and future

Each hepatitis virus-Hepatitis A, B, C, D, E, and G-poses a distinct scenario to the patient and clinician alike. Since the discovery of each virus, extensive knowledge regarding epidemiology, virologic properties, and the natural clinical and immunologic history of acute and chronic infections has been generated. Basic discoveries about host immunologic responses to acute and chronic viral infections, combined with virologic data, has led to vaccines to prevent Hepatitis A, B, and E and highly efficacious antivirals for Hepatitis B and C. These therapeutic breakthroughs are transforming the fields of hepatology, transplant medicine in general, and public and global health. Most notably, there is even an ambitious global effort to eliminate chronic viral hepatitis within the next decade. While attainable, there are many barriers to this goal that are being actively investigated in basic and clinical labs on the local, national, and international scales. Herein, we discuss pertinent clinical information and recent organizational guidelines for each of the individual hepatitis viruses while also synthesizing this information with the latest research to focus on exciting future directions for each virus.

Chronic hepatitis B: New potential therapeutic drugs target

Chronic hepatitis B (CHB) infection remains the most causative agent of liver-related morbidity and mortality worldwide. It impacts nearly 300 million people. The current treatment for chronic infection with the hepatitis B virus (HBV) is complex and lacks a durable treatment response, especially hepatitis B surface antigen (HBsAg) loss, necessitating indefinite treatment in most CHB patients due to the persistence of HBV covalently closed circular DNA (cccDNA). New drugs that target distinct steps of the HBV life cycle have been investigated, which comprise inhibiting the entry of HBV into hepatocytes, disrupting or silencing HBV cccDNA, modulating nucleocapsid assembly, interfering HBV transcription, and inhibiting HBsAg release. The achievement of a functional cure or sustained HBsAg loss in CHB patients represents the following approach towards HBV eradication. This review will explore the up-to-date advances in the development of new direct-acting anti-HBV drugs. Hopefully, with the combination of the current antiviral drugs and the newly developed direct-acting antiviral drugs targeting the different steps of the HBV life cycle, the ultimate eradication of CHB infection will soon be achieved.

Making safe sense of an anti-sense!

Bepiroversen has been developed and trialed for the cure of HBV. Yuen et al.¹ report on the safety and antiviral efficacy of this agent. We “spotlight” key findings of this study and its impact for future clinical trial design.

Safety, tolerability and antiviral activity of the antisense oligonucleotide bepirovirsen in patients with chronic hepatitis B: a phase 2 randomized controlled trial

Chronic infection with hepatitis B virus (HBV) leads to an increased risk of death from cirrhosis and hepatocellular carcinoma. Functional cure rates are low with current treatment options (nucleos(t)ide analogs (NAs) and pegylated interferons). Bepirovirsen is an antisense oligonucleotide targeting all HBV messenger RNAs; in cell culture and animal models, bepirovirsen leads to reductions in HBV-derived RNAs, HBV DNA and viral proteins. This phase 2 double-blinded, randomized, placebo-controlled trial is the first evaluation of the safety and activity of an antisense oligonucleotide targeting HBV RNA in both treatment-naïve and virally suppressed individuals with chronic HBV infection. The primary objective was to assess the safety and tolerability of bepirovirsen in individuals with chronic hepatitis B (CHB) (NCT02981602). The secondary objective was to assess antiviral activity, including the change from baseline to day 29 in serum hepatitis B surface antigen (HBsAg) concentration. Participants with CHB infection ≥6 months and serum HBsAg ≥50 IU ml^-1 were enrolled from seven centers across Hong Kong and the Republic of Korea and randomized (3:1 within each dose cohort) to receive bepirovirsen or placebo via subcutaneous injection twice weekly during weeks 1 and 2 (days 1, 4, 8 and 11) and once weekly during weeks 3 and 4 (days 15 and 22). Participants were then followed for 26 weeks. Twenty-four participants were treatment-naïve and seven were receiving stable NA therapy. Treatment-emergent adverse events were mostly mild/moderate (most commonly injection site reactions). Eleven (61.1%) and three (50.0%) treatment-naïve participants experienced one or more treatment-emergent adverse event in the bepirovirsen and placebo groups, respectively. In participants receiving NA therapy, the corresponding numbers were three (60.0%) and one (50.0%). Transient, self-resolving alanine aminotransferase flares (≥2× upper limit of normal) were observed in eight treatment-naïve participants and three participants on stable NA regimens in the bepirovirsen treatment arms. HBsAg reductions were observed and were significant versus placebo for treatment-naïve participants receiving bepirovirsen 300 mg (P = 0.001), but not for the bepirovirsen 150 mg group (P = 0.245) or participants receiving stable NA therapy (P = 0.762). Two participants in each of the 300 mg dose groups achieved HBsAg levels below the lower limit of quantitation by day 29 (n = 3) or day 36 (n = 1). Bepirovirsen had a favorable safety profile. These preliminary observations warrant further investigation of the safety and activity of bepirovirsen in a larger CHB patient population.

Clinical Study of Single-Stranded Oligonucleotide RO7062931 in Healthy Volunteers and Patients With Chronic Hepatitis B

BACKGROUND AND AIMS

RO7062931 is an N-acetylgalactosamine (GalNAc)-conjugated single-stranded locked nucleic acid oligonucleotide complementary to HBV RNA. GalNAc conjugation targets the liver through the asialoglycoprotein receptor (ASGPR). This two-part phase 1 study evaluated the safety, pharmacokinetics, and pharmacodynamics of RO7062931 in healthy volunteers and patients with chronic hepatitis B (CHB) who were virologically suppressed.

APPROACH AND RESULTS

Part 1 was a single ascending dose study in healthy volunteers randomized to receive a single RO7062931 dose (0.1-4.0 mg/kg), or placebo. Part 2 was a multiple ascending dose study in patients with CHB randomized to receive RO7062931 at 0.5, 1.5, or 3.0 mg/kg or placebo every month for a total of 2 doses (Part 2a) or RO7062931 at 3.0 mg/kg every 2 weeks, 3.0 mg/kg every week (QW), or 4.0 mg/kg QW or placebo for a total of 3-5 doses (Part 2b). Sixty healthy volunteers and 59 patients received RO7062931 or placebo. The majority of adverse events (AEs) reported were mild in intensity. Common AEs included self-limiting injection site reactions and influenza-like illness. Supradose-proportional increases in RO7062931 plasma exposure and urinary excretion occurred at doses ≥3.0 mg/kg. In patients with CHB, RO7062931 resulted in dose-dependent and time-dependent reduction in HBsAg versus placebo. The greatest HBsAg declines from baseline were achieved with the 3.0 mg/kg QW dose regimen (mean nadir ~0.5 log₁₀  IU/mL) independent of HBeAg status.

CONCLUSIONS

RO7062931 is safe and well tolerated at doses up to 4.0 mg/kg QW. Supradose-proportional exposure at doses of 3.0-4.0 mg/kg was indicative of partial saturation of the ASGPR-mediated liver uptake system. Dose-dependent declines in HBsAg demonstrated target engagement with RO7062931.

Prospects for the Global Elimination of Hepatitis B

Chronic hepatitis B virus (HBV) infection is the leading cause of liver cirrhosis and hepatocellular carcinoma, estimated to be globally responsible for ∼800,000 deaths annually. Although effective vaccines are available to prevent new HBV infection, treatment of existing chronic hepatitis B (CHB) is limited, as the current standard-of-care antiviral drugs can only suppress viral replication without achieving cure. In 2016, the World Health Organization called for the elimination of viral hepatitis as a global public health threat by 2030. The United States and other nations are working to meet this ambitious goal by developing strategies to cure CHB, as well as prevent HBV transmission. This review considers recent research progress in understanding HBV pathobiology and development of therapeutics for the cure of CHB, which is necessary for elimination of hepatitis B by 2030.

Direct-acting antivirals and viral RNA targeting for hepatitis B cure

PURPOSE OF REVIEW

The current aim in the HBV landscape is to develop therapeutic strategies to achieve a functional cure of infection, characterized by a sustained loss of HBsAg off-treatment. Current treatment options, that is, nucleos(t)ide analogues and IFN are effective at viral suppression but very poor at achieving HBsAg loss. This article is designed to summarize the HBV life cycle in order to review the current treatment strategies and compounds targeting different points of the virus life cycle, which are either in preclinical or clinical phases.

RECENT FINDINGS

Recently our developed understanding of the HBV life cycle has enabled the development of multiple novel treatment options, all aiming for functional cure.

SUMMARY

It is likely that combinations of novel treatments will be needed to achieve a functional cure, including those that target the virus itself as well as those that target the immune system.

Restoration of a functional antiviral immune response to chronic HBV infection by reducing viral antigen load: if not sufficient, is it necessary?

The prolonged viral antigen stimulation is the driving force for the development of immune tolerance to chronic hepatitis B virus (HBV) infection. The sustained reduction of viral proteins may allow for the recovery and efficient activation of HBV-specific T and B cells by immune-stimulating agents, checkpoint blockades and/or therapeutic vaccinations. Recently, several therapeutic approaches have been shown to significantly reduce intrahepatic viral proteins and/or circulating HBV surface antigen (HBsAg) with variable impacts on the host antiviral immune responses in animal models or human clinical trials. It remains to be further investigated whether reduction of viral protein expression or induction of intrahepatic viral protein degradation is more efficacious to break the immune tolerance to chronic HBV infection. It is also of great interest to know if the accelerated clearance of circulating HBsAg by antibodies has a long-term immunological impact on HBV infection and disease progression. Although it is clear that removal of antigen stimulation alone is not sufficient to induce the functional recovery of exhausted T and B cells, accumulating evidence suggests that the reduction of viral antigen load appears to facilitate the therapeutic activation of functional antiviral immunity in chronic HBV carriers. Based on a systematic review of the findings in animal models and clinical studies, the research directions toward discovery and development of more efficacious therapeutic approaches to reinvigorate HBV-specific adaptive immune function and achieve the durable control of chronic HBV infection, i.e. a functional cure, in the vast majority of treated patients are discussed.

Strategies to Inhibit Hepatitis B Virus at the Transcript Level

Approximately 240 million people are chronically infected with hepatitis B virus (HBV), despite four decades of effective HBV vaccination. During chronic infection, HBV forms two distinct templates responsible for viral transcription: (1) episomal covalently closed circular (ccc)DNA and (2) host genome-integrated viral templates. Multiple ubiquitous and liver-specific transcription factors are recruited onto these templates and modulate viral gene transcription. This review details the latest developments in antivirals that inhibit HBV gene transcription or destabilize viral transcripts. Notably, nuclear receptor agonists exhibit potent inhibition of viral gene transcription from cccDNA. Small molecule inhibitors repress HBV X protein-mediated transcription from cccDNA, while small interfering RNAs and single-stranded oligonucleotides result in transcript degradation from both cccDNA and integrated templates. These antivirals mediate their effects by reducing viral transcripts abundance, some leading to a loss of surface antigen expression, and they can potentially be added to the arsenal of drugs with demonstrable anti-HBV activity. Thus, these candidates deserve special attention for future repurposing or further development as anti-HBV therapeutics.

Advances in treatment and prevention of hepatitis B

Chronic hepatitis B (CHB) continues to contribute to worldwide morbidity and mortality significantly. Scientists, clinicians, pharmaceutical companies, and health organizations have dedicated substantial Intellectual and monetary resources to finding a cure, increasing immunization rates, and reducing the global burden of CHB. National and international health-related organizations including the center for disease control, the national institute of health, the American Association for the study of liver disease (AASLD), The European association for the study of the Liver (EASL), The Asia Pacific association for the study of the Liver (APASL) and the world health organization release periodic recommendations for disease prevention and treatment. Our review of the most recent guidelines by EASL, AASLD, APASL, and Taiwan Association for the Study of the Liver revealed that an overwhelming majority of cited studies were published before 2018. We reviewed Hepatitis B-related literature published 2018 onwards to identify recent developments and current barriers that will likely direct future efforts towards eradicating hepatitis B. The breakthrough in our understanding of the hepatitis B virus life cycle and resulting drug development is encouraging with significant room for further progress. Data from high-risk populations, most vulnerable to the devastating effects of hepatitis B infection and reactivation remain sparse. Utilization of systems approach, optimization of experimental models, identification and validation of next-generation biomarkers, and precise modulation of the human immune response will be critical for future innovation. Within the foreseeable future, new treatments will likely complement conventional therapies rather than replace them. Most Importantly, pragmatic management of CHB related population health challenges must be prioritized to produce real-world results.

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.

Hepatitis B virus: promising drug targets and therapeutic implications

Introduction: Current therapy for infection with hepatitis B virus (HBV) rarely clears the virus, and viremia commonly resurges following treatment withdrawal. To prevent serious complications of the infection, research has been aimed at identifying new viral and host targets that can be exploited to inactivate HBV replication.Areas covered: This paper reviews the use of these new molecular targets to advance anti-HBV therapy. Emphasis is on appraising data from pre-clinical and early clinical studies described in journal articles published during the past 10 years and available from PubMed.Expert opinion: The wide range of viral and host factors that can be targeted to disable HBV is impressive and improved insight into HBV molecular biology continues to provide the basis for new drug design. In addition to candidate therapies that have direct or indirect actions on HBV covalently closed circular DNA (cccDNA), compounds that inhibit HBsAg secretion, viral entry, destabilize viral RNA and effect enhanced immune responses to HBV show promise. Preclinical and clinical evaluation of drug candidates, as well as investigating use of treatment combinations, are encouraging. The field is poised at an interesting stage and indications are that reliably achieving functional cure from HBV infection is a tangible goal.

A hepatitis B virus transgenic mouse model with a conditional, recombinant, episomal genome

Background & Aims

Development of new and more effective therapies against hepatitis B virus (HBV) is limited by the lack of suitable small animal models. The HBV transgenic mouse model containing an integrated overlength 1.3-mer construct has yielded crucial insights, but this model unfortunately lacks covalently closed circular DNA (cccDNA), the episomal HBV transcriptional template, and cannot be cured given that HBV is integrated in every cell.

Methods

To solve these 2 problems, we generated a novel transgenic mouse (HBV1.1X), which generates an excisable circular HBV genome using Cre/LoxP technology. This model possesses a HBV1.1-mer cassette knocked into the ROSA26 locus and is designed for stable expression of viral proteins from birth, like the current HBV transgenic mouse model, before genomic excision with the introduction of Cre recombinase.

Results

We demonstrated induction of recombinant cccDNA (rcccDNA) formation via viral or transgenic Cre expression in HBV1.1X mice, and the ability to regulate HBsAg and HBc expression with Cre in mice. Tamoxifen-inducible Cre could markedly downregulate baseline HBsAg levels from the integrated HBV genome. To demonstrate clearance of HBV from HBV1.1X mice, we administered adenovirus expressing Cre, which permanently and significantly reduced HBsAg and core antigen levels in the murine liver via rcccDNA excision and a subsequent immune response.

Conclusions

The HBV1.1X model is the first Cre-regulatable HBV transgenic mouse model and should be of value to mimic chronic HBV infection, with neonatal expression and tolerance of HBV antigens, and on-demand modulation of HBV expression.

Lay summary

Hepatitis B virus (HBV) can only naturally infect humans and chimpanzees. Mouse models have been developed with the HBV genome integrated into mouse chromosomes, but this prevents mice from being cured. We developed a new transgenic mouse model that allows for HBV to be excised from mouse chromosomes to form a recombinant circular DNA molecule resembling the natural circular HBV genome. HBV expression could be reduced in these mice, enabling curative therapies to be tested in this new mouse model.

Cre/LoxP-HBV plasmids generating recombinant covalently closed circular DNA genome upon transfection

New therapies against hepatitis B virus (HBV) require the elimination of covalently closed circular DNA (cccDNA), the episomal HBV genome. HBV plasmids containing an overlength 1.3-mer genome and bacterial backbone (pHBV1.3) are used in many different models, but do not replicate the unique features of cccDNA. Since the stable cccDNA pool is a barrier to HBV eradication in patients, we developed a recombinant circular HBV genome (rcccDNA) to mimic the cccDNA using Cre/LoxP technology. We validated four LoxP insertion sites into the HBV genome using hydrodynamic tail vein injection into murine liver, demonstrating high levels of HBV surface antigen (HBsAg) and HBV DNA expression with rcccDNA formation. HBsAg expression from rcccDNA was >30,000 ng/mL over 78 days, while HBsAg-expression from pHBV1.3 plasmid DNA declined from 2753 ng/mL to 131 ng/mL over that time in immunodeficient mice (P < 0.001), reflective of plasmid DNA silencing. We then cloned Cre-recombinase in cis on the LoxP-HBV plasmids, achieving plasmid stability in bacteria with intron insertion into Cre and demonstrating rcccDNA formation after transfection in vitro and in vivo. These cis-Cre/LoxP-HBV plasmids were then used to create HBx-mutant and GFP reporter plasmids to further probe cccDNA biology and antiviral strategies against cccDNA. Overall, we believe these auto-generating rcccDNA plasmids will be of great value to model cccDNA for testing new therapies against HBV infection.

New Approaches to the Treatment of Chronic Hepatitis B

The currently recommended treatment for chronic hepatitis B virus (HBV) infection achieves only viral suppression whilst on therapy, but rarely hepatitis B surface antigen (HBsAg) loss. The ultimate therapeutic endpoint is the combination of HBsAg loss, inhibition of new hepatocyte infection, elimination of the covalently closed circular DNA (cccDNA) pool, and restoration of immune function in order to achieve virus control. This review concentrates on new antiviral drugs that target different stages of the HBV life cycle (direct acting antivirals) and others that enhance both innate and adaptive immunity against HBV (immunotherapy). Drugs that block HBV hepatocyte entry, compounds that silence or deplete the cccDNA pool, others that affect core assembly, agents that degrade RNase-H, interfering RNA molecules, and nucleic acid polymers are likely interventions in the viral life cycle. In the immunotherapy category, molecules that activate the innate immune response such as Toll-like-receptors, Retinoic acid Inducible Gene-1 (RIG-1) and stimulator of interferon genes (STING) agonists or checkpoint inhibitors, and modulation of the adaptive immunity by therapeutic vaccines, vector-based vaccines, or adoptive transfer of genetically-engineered T cells aim towards the restoration of T cell function. Future therapeutic trends would likely be a combination of one or more of the aforementioned drugs that target the viral life cycle and at least one immunomodulator.

Strategies to eliminate HBV infection: an update

Chronic hepatitis B (CHB) is a widespread global infection and a leading cause of hepatocellular carcinoma and liver failure. Current approaches to treat CHB involve the suppression of viral replication with either interferon or nucleos(t)ide analog therapy, but neither of these approaches can reliably induce viral eradication, immunologic control or long-lived viral suppression in the absence of continued therapy. In this update, we explore the major obstacles of CHB cure and review new therapeutic strategies and drug candidates.

Therapeutic strategies for hepatitis B virus infection: towards a cure

Chronic hepatitis B virus (HBV) infection is a common cause of liver disease globally, with a disproportionately high burden in South-East Asia. Vaccines and nucleoside or nucleotide drugs are available and reduce both new infection rates and the development of liver disease in HBV-positive persons who adhere to long-term suppressive treatment. Although there is still considerable value in optimizing access to virus-suppressing regimens, the scientific and medical communities have embarked on a concerted journey to identify new antiviral drugs and immune interventions aimed at curing infection. The mechanisms and drug targets being explored are diverse; however, the field universally recognizes the importance of addressing the persistence of episomal covalently closed circular DNA, the existence of integrated HBV DNA in the host genome and the large antigen load, particularly of hepatitis B surface antigen. Another major challenge is to reinvigorate the exhausted immune response within the liver microenvironment. Ultimately, combinations of new drugs will be required to cure infection. Here we critically review the recent literature that describes the rationale for curative therapies and the resulting compounds that are being tested in clinical trials for hepatitis B.

Hepatitis B virus-specific effector CD8+ T cells are an important determinant of disease prognosis: A meta-analysis

BACKGROUND

Hepatitis B virus (HBV)-specific effector CD8⁺ T cells are critical for viral clearance. To determine the effects of HBV-specific effector CD8⁺ T cells on HBV infection, we performed a meta-analysis of the available literature.

METHODS

Electronic database searches identified appropriately designed studies that detected specific CD8⁺ T cells in HBV-infected patients. Our main endpoints were the course of infection, seroconversion of HBV "e" antigen (HBeAg), the level of HBVDNA, and alanine aminotransferase (ALT) activity. We used a fixed/random model for analysis, according to the results of a heterogeneity test (P value of Q-squared, I²).

RESULTS

Our searches found five eligible articles. Pooled estimation of the reported results showed that levels of specific CD8⁺ T cells were significantly higher in patients with acute hepatitis B than in patients with chronic hepatitis B (odds ratio [OR] = 76.30, 95% confidence interval [CI]: 15.37-378.70). With respect to chronic hepatitis B, patients with <10⁷ copies/ml HBVDNA had higher levels of specific CD8⁺ T cells relative to patients with >10⁷ copies/ml HBVDNA, but the difference had no statistics significance (OR: 3.89, 95% CI: 0.71-21.33). Patients with negative HBeAg or positive anti-HBeAg antibody (anti-HBe) results had significantly higher levels of specific CD8⁺ T cells versus patients with positive HBeAg results (OR: 5.82, 95% CI: 1.41-24.13). There were no significant associations between the levels of specific CD8⁺ T cells and serum ALT activity (OR = 0.86, 95% CI: 0.01-74.15).

CONCLUSION

HBV-specific effector CD8⁺ T cells influence the disease activity in HBV-infected patients in various ways and determine prognosis by eliminating the virus. Therefore, efforts of studying HBV-specific effector CD8⁺ T cells focused vaccine are potentially needed.

A Randomized, Double-Blind, Placebo-Controlled, First-Time-in-Human Study to Assess the Safety, Tolerability, and Pharmacokinetics of Single and Multiple Ascending Doses of GSK3389404 in Healthy Subjects

GSK3389404 is a liver‐targeted antisense oligonucleotide that inhibits synthesis of hepatitis B surface antigen and all other hepatitis B virus proteins. This first‐in‐human, randomized, double‐blind, phase 1 study assessed the safety and pharmacokinetics of GSK3389404 administered subcutaneously (SC) in healthy subjects. Four single ascending‐dose cohorts (10 mg, 30 mg, 60 mg, and 120 mg) and 3 multiple ascending‐dose cohorts (30 mg, 60 mg, and 120 mg once weekly for 4 weeks) each comprised 6 subjects randomized to GSK3389404 and 2 subjects randomized to placebo. There were no serious adverse events (AEs) or withdrawals due to AEs. The safety profile did not worsen with repeated dosing. The most frequent treatment‐related AEs were injection site reactions (19.0% [n = 8/42], frequency unrelated to dose levels); all were mild (Grade 1) and resolved without dose modification or discontinuation. GSK3389404 administered subcutaneously was readily absorbed with a time to maximum plasma concentration (T_max) of 1–4 hours and an elimination half‐life of 3–6 hours in plasma. Plasma area under the concentration‐time curve (AUC) and maximum observed concentration (C_max) were dose‐proportional. Dose‐normalized plasma AUC from time 0 to infinity averaged 69.9 ng·h/(mL·mg dose) across cohorts, and C_max 9.5 ng/(mL·mg dose). Pharmacokinetic profiles and parameters were comparable between single and multiple dosing. No accumulation was observed with once‐weekly dosing. The metabolite was undetectable in urine and plasma. In the pooled urine, GSK3389404 was estimated to account for <0.1% of the total dose. In summary, GSK3389404 dosing has been tested up to 120 mg for 4 weeks with an acceptable safety and pharmacokinetic profile, supporting further clinical investigation in patients with chronic hepatitis B.

Analysis of epitope-based vaccine candidates against the E antigen of the hepatitis B virus based on the B genotype sequence: An in silico and in vitro approach

Chronic hepatitis B virus infection is a worldwide health problem with no current effective strategy to achieve a cure. The Hepatitis B virus (HBV) E antigen (HBeAg) has a negative effect on the immune system and a therapeutic vaccine is a promising strategy in order to treat chronic virus infection. In this study, we analyzed and identified the MHC-I, MHC-II and B cell epitopes of the HBeAg based on a B genotype sequence of HBV using a bioinformatic approach and in vitro experiments. The computational approach provided us with four epitopes (LLWFHISCL, YLVSFGVWI, MQLFHLCLI, TVLEYLVSF) of the specific MHC-I allele HLA-A0201 that conformed to all criteria. Molecular docking and a peptide binding assay showed that epitope TVLEYLVSF had the lowest binding energy and epitope LLWFHISCL had the highest binding affinity to the HLA-A0201 molecule. An interferonγenzyme-linked immunospot assay and cytotoxicity assay revealed that epitope LLWFHISCL had the highest ability to induce and stimulate T cells. Furthermore, we determined four core peptides of MHC-II epitopes and a region of the B cell epitope. The epitopes and region identified in this research may be helpful in designing epitope-based vaccines and boosting the mechanism research of HBeAg and its effect on the immune system.

HBsAg-redirected T cells exhibit antiviral activity in HBV-infected human liver chimeric mice

BACKGROUND

Chronic hepatitis B virus (HBV) infection remains incurable. Although HBsAg-specific chimeric antigen receptor (HBsAg-CAR) T cells have been generated, they have not been tested in animal models with authentic HBV infection.

METHODS

We generated a novel CAR targeting HBsAg and evaluated its ability to recognize HBV+ cell lines and HBsAg particles in vitro. In vivo, we tested whether human HBsAg-CAR T cells would have efficacy against HBV-infected hepatocytes in human liver chimeric mice.

RESULTS

HBsAg-CAR T cells recognized HBV-positive cell lines and HBsAg particles in vitro as judged by cytokine production. However, HBsAg-CAR T cells did not kill HBV-positive cell lines in cytotoxicity assays. Adoptive transfer of HBsAg-CAR T cells into HBV-infected humanized mice resulted in accumulation within the liver and a significant decrease in plasma HBsAg and HBV-DNA levels compared with control mice. Notably, the fraction of HBV core-positive hepatocytes among total human hepatocytes was greatly reduced after HBsAg-CAR T cell treatment, pointing to noncytopathic viral clearance. In agreement, changes in surrogate human plasma albumin levels were not significantly different between treatment and control groups.

CONCLUSIONS

HBsAg-CAR T cells have anti-HBV activity in an authentic preclinical HBV infection model. Our results warrant further preclinical exploration of HBsAg-CAR T cells as immunotherapy for HBV.

A novel orally available small molecule that inhibits hepatitis B virus expression

BACKGROUND & AIMS

The hallmarks of chronic HBV infection are a high viral load (HBV DNA) and even higher levels (>100-fold in excess of virions) of non-infectious membranous particles containing the tolerogenic viral S antigen (HBsAg). Currently, standard treatment effectively reduces viremia but only rarely results in a functional cure (defined as sustained HBsAg loss). There is an urgent need to identify novel therapies that reduce HBsAg levels and restore virus-specific immune responsiveness in patients. We report the discovery of a novel, potent and orally bioavailable small molecule inhibitor of HBV gene expression (RG7834).

METHODS

RG7834 antiviral characteristics and selectivity against HBV were evaluated in HBV natural infection assays and in a urokinase-type plasminogen activator/severe combined immunodeficiency humanized mouse model of HBV infection, either alone or in combination with entecavir.

RESULTS

Unlike nucleos(t)ide therapies, which reduce viremia but do not lead to an effective reduction in HBV antigen expression, RG7834 significantly reduced the levels of viral proteins (including HBsAg), as well as lowering viremia. Consistent with its proposed mechanism of action, time course RNA-seq analysis revealed a fast and selective reduction in HBV mRNAs in response to RG7834 treatment. Furthermore, oral treatment of HBV-infected humanized mice with RG7834 led to a mean HBsAg reduction of 1.09 log₁₀ compared to entecavir, which had no significant effect on HBsAg levels. Combination of RG7834, entecavir and pegylated interferon α-2a led to significant reductions of both HBV DNA and HBsAg levels in humanized mice.

CONCLUSION

We have identified a novel oral HBV viral gene expression inhibitor that blocks viral antigen and virion production, that is highly selective for HBV, and has a unique antiviral profile that is clearly differentiated from nucleos(t)ide analogues.

LAY SUMMARY

We discovered a novel small molecule viral expression inhibitor that is highly selective for HBV and unlike current therapy inhibits the expression of viral proteins by specifically reducing HBV mRNAs. RG7834 can therefore potentially provide anti-HBV benefits and increase HBV cure rates, by direct reduction of viral agents needed to complete the viral life cycle, as well as a reduction of viral agents involved in evasion of the host immune responses.

Liver-Targeted Anti-HBV Single-Stranded Oligonucleotides with Locked Nucleic Acid Potently Reduce HBV Gene Expression In Vivo

Chronic hepatitis B infection (CHB) is an area of high unmet medical need. Current standard-of-care therapies only rarely lead to a functional cure, defined as durable hepatitis B surface antigen (HBsAg) loss following treatment. The goal for next generation CHB therapies is to achieve a higher rate of functional cure with finite treatment duration. To address this urgent need, we are developing liver-targeted single-stranded oligonucleotide (SSO) therapeutics for CHB based on the locked nucleic acid (LNA) platform. These LNA-SSOs target hepatitis B virus (HBV) transcripts for RNase-H-mediated degradation. Here, we describe a HBV-specific LNA-SSO that effectively reduces intracellular viral mRNAs and viral antigens (HBsAg and HBeAg) over an extended time period in cultured human hepatoma cell lines that were infected with HBV with mean 50% effective concentration (EC₅₀) values ranging from 1.19 to 1.66 μM. To achieve liver-specific targeting and minimize kidney exposure, this LNA-SSO was conjugated to a cluster of three N-acetylgalactosamine (GalNAc) moieties that direct specific binding to the asialoglycoprotein receptor (ASGPR) expressed specifically on the surface of hepatocytes. The GalNAc-conjugated LNA-SSO showed a strikingly higher level of potency when tested in the AAV-HBV mouse model as compared with its non-conjugated counterpart. Remarkably, higher doses of GalNAc-conjugated LNA-SSO resulted in a rapid and long-lasting reduction of HBsAg to below the detection limit for quantification, i.e., by 3 log10 (p < 0.0003). This antiviral effect depended on a close match between the sequences of the LNA-SSO and its HBV target, indicating that the antiviral effect is not due to non-specific oligonucleotide-driven immune activation. These data support the development of LNA-SSO therapeutics for the treatment of CHB infection.

Upcoming pharmacological developments in chronic hepatitis B: can we glimpse a cure on the horizon?

Background

Hepatitis B virus (HBV) chronic infection affects up to 240 million people in the world and it is a common cause of cirrhosis and hepatocellular carcinoma (HCC). HBV covalently closed circular DNA (cccDNA) plays an essential role in HBV persistence and replication. Current pharmacological treatment with nucleos(t)ide analogues (NA) may suppress HBV replication with little or no impact on cccDNA, hence lifelong treatment is required in the vast majority of patients. Clearances of intrahepatic cccDNA and/or HBsAg are critical endpoints for future antiviral therapy in chronic HBV. Recent promising developments targeting different molecular HBV life cycle steps are being pre-clinically tested or have moved forward in early clinical trials.

Methods

We review the current state of the art of these pharmacological developments, mainly focusing on efficacy and safety results, which are expected to lay the ground for future HBV eradication. An inclusive literature search on new treatments of HBV using the following electronic databases: Pubmed/MEDLINE, AMED, CINAHL and the Cochrane Central Register of Controlled Trials. Full-text manuscripts and abstracts published over the last 12 years, from 2005 to March 2011 were reviewed for relevance and reference lists were crosschecked for additional applicable studies regarding new HBV antiviral treatment.

Results

HBV entry inhibitors, HBV core inhibitors, HBV cccDNA transcripts RNA interference, HBV cell apoptosis inducers, HBV RNA, viral proteins and DNA knock down agents, HBV release inhibitors, anti-sense nucleosides, exogenous interferon stimulation, interferon response stimulation and HBV therapeutic vaccines were reviewed.

Conclusion

This review will provide readers with an updated vision of current and foreseeable therapeutic developments in chronic hepatitis B.

New Viral and Immunological Targets for Hepatitis B Treatment and Cure: A Review

Although current therapies can be successful at suppressing hepatitis B viral load, long-term viral cure is not within reach. Subsequent strategies combining pegylated interferon alfa with nucleoside/nucleotide analogues have not resulted in any major paradigm shift. An improved understanding of the hepatitis B virus (HBV) lifec ycle and virus-induced immune dysregulation has, however, revealed many potential therapeutic targets, and there are hopes that treatment of hepatitis B could soon be revolutionized. This review summarizes the current developments in HBV therapeutics-both virus directed and host directed.

Activity of nucleic acid polymers in rodent models of HBV infection

Nucleic acid polymers (NAPs) block the release of HBsAg from infected hepatocytes. These compounds have been previously shown to have the unique ability to eliminate serum surface antigen in DHBV-infected Pekin ducks and achieve multilog reduction of HBsAg or HBsAg loss in patients with chronic HBV infection and HBV/HDV coinfection. In ducks and humans, the blockage of HBsAg release by NAPs occurs by the selective targeting of the assembly and/or secretion of subviral particles (SVPs). The clinically active NAP species REP 2055 and REP 2139 were investigated in other relevant animal models of HBV infection including woodchucks chronically infected with WHV, HBV transgenic mice and HBV infected SCID-Hu mice. The liver accumulation of REP 2139 in woodchucks following subcutaneous administration was examined and was found to be similar to that observed in mice and ducks. However, in woodchucks, NAP treatment was associated with only mild (36-79% relative to baseline) reductions in WHsAg (4/10 animals) after 3-5 weeks of treatment without changes in serum WHV DNA. In HBV infected SCID-Hu mice, REP 2055 treatment was not associated with any reduction of HBsAg, HBeAg or HBV DNA in the serum after 28 days of treatment. In HBV transgenic mice, no reductions in serum HBsAg were observed with REP 2139 with up to 12 weeks of treatment. In conclusion, the antiviral effects of NAPs in DHBV infected ducks and patients with chronic HBV infection were weak or absent in woodchuck and mouse models despite similar liver accumulation of NAPs in all these species, suggesting that the mechanisms of SVP assembly and or secretion present in rodent models differs from that in DHBV and chronic HBV infections.

In Situ Liver Expression of HBsAg/CD3-Bispecific Antibodies for HBV Immunotherapy

Current therapies against hepatitis B virus (HBV) do not reliably cure chronic infection, necessitating new therapeutic approaches. The T cell response can clear HBV during acute infection, and the adoptive transfer of antiviral T cells during bone marrow transplantation can cure patients of chronic HBV infection. To redirect T cells to HBV-infected hepatocytes, we delivered plasmids encoding bispecific antibodies directed against the viral surface antigen (HBsAg) and CD3, expressed on almost all T cells, directly into the liver using hydrodynamic tail vein injection. We found a significant reduction in HBV-driven reporter gene expression (184-fold) in a mouse model of acute infection, which was 30-fold lower than an antibody only recognizing HBsAg. While bispecific antibodies triggered, in part, antigen-independent T cell activation, antibody production within hepatocytes was non-cytotoxic. We next tested the bispecific antibodies in a different HBV mouse model, which closely mimics the transcriptional template for HBV, covalently closed circular DNA (cccDNA). We found that the antiviral effect was noncytopathic, mediating a 495-fold reduction in HBsAg levels at day 4. At day 33, bispecific antibody-treated mice exhibited 35-fold higher host HBsAg immunoglobulin G (IgG) antibody production versus untreated groups. Thus, gene therapy with HBsAg/CD3-bispecific antibodies represents a promising therapeutic strategy for patients with HBV.

New horizon for radical cure of chronic hepatitis B virus infection

About 250 to 350 million people worldwide are chronically infected with hepatitis B virus (HBV), and about 700000 patients per year die of HBV-related cirrhosis or hepatocellular carcinoma (HCC). Several anti-viral agents, such as interferon and nucleos(t)ide analogues (NAs), have been used to treat this disease. NAs especially have been shown to strongly suppress HBV replication, slowing the progression to cirrhosis and the development of HCC. However, reactivation of HBV replication often occurs after cessation of treatment, because NAs alone cannot completely remove covalently-closed circular DNA (cccDNA), the template of HBV replication, from the nuclei of hepatocytes. Anti-HBV immune responses, in conjunction with interferon-γ and tumor necrosis factor-α, were found to eliminate cccDNA, but complete eradication of cccDNA by immune response alone is difficult, as shown in patients who recover from acute HBV infection but often show long-term persistence of small amounts of HBV-DNA in the blood. Several new drugs interfering with the life cycle of HBV in hepatocytes have been developed, with drugs targeting cccDNA theoretically the most effective for radical cure of chronic HBV infection. However, the safety of these drugs should be extensively examined before application to patients, and combinations of several approaches may be necessary for radical cure of chronic HBV infection.

Antisense antimicrobial therapeutics

Antisense antimicrobial therapeutics are synthetic oligomers that silence expression of specific genes. This specificity confers an advantage over broad-spectrum antibiotics by avoiding unintended effects on commensal bacteria. The sequence-specificity and short length of antisense antimicrobials also pose little risk to human gene expression. Because antisense antimicrobials are a platform technology, they can be rapidly designed and synthesized to target almost any microbe. This reduces drug discovery time, and provides flexibility and a rational approach to drug development. Recent work has shown that antisense technology has the potential to address the antibiotic-resistance crisis, since resistance mechanisms for standard antibiotics apparently have no effect on antisense antimicrobials. Here, we describe current reports of antisense antimicrobials targeted against viruses, parasites, and bacteria.

New antiviral targets for innovative treatment concepts for hepatitis B virus and hepatitis delta virus

Current therapies of chronic hepatitis B (CHB) remain limited to pegylated-interferon-alpha (PegIFN-α) or any of the five approved nucleos(t)ide analogues (NUC) treatments. While viral suppression can be achieved in the majority of patients with the high-barrier-to-resistance new-generation of NUC, i.e. entecavir and tenofovir, HBsAg loss is achieved by PegIFN-α and/or NUC in only 10% of patients, after a 5-year follow-up. Attempts to improve the response by administering two different NUC or a combination of NUC and PegIFN-α have not provided a dramatic increase in the rate of functional cure. Because of this and the need of long-term NUC administration, there is a renewed interest regarding the understanding of various steps of the HBV replication cycle, as well as specific virus-host cell interactions, in order to define new targets and develop new antiviral drugs. This includes a direct inhibition of viral replication with entry inhibitors, drugs targeting cccDNA, siRNA targeting viral transcripts, capsid assembly modulators, and approaches targeting the secretion of viral envelope proteins. Restoration of immune responses is a complementary approach. The restoration of innate immunity against HBV can be achieved, with TLR agonists or specific antiviral cytokine delivery. Restoration of adaptive immunity may be achieved with inhibitors of negative checkpoint regulators, therapeutic vaccines, or autologous transfer of engineered HBV-specific T cells. Novel targets and compounds will readily be evaluated using both relevant and novel in vitro and in vivo models of HBV infection. The addition of one or several new drugs to current therapies should offer the prospect of a markedly improved response to treatments and an increased rate of functional cure. This should lead to a reduced risk of antiviral drug resistance, and to a decreased incidence of cirrhosis and hepatocellular carcinoma (HCC).