Hepatitis B cure: From discovery to regulatory approval

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.

Okuda lecture: Challenges of hepatitis B in the era of antiviral therapy

Nucleos(t)ide analogs (NAs) are effective, safe, and convenient antiviral therapy to suppress replication of hepatitis B virus, which can be translated into improved long-term outcome of chronic hepatitis B patients. The current recommended first-line NAs, namely, entecavir and tenofovir, are largely free from problems of drug resistance. Nonetheless, there are still a few challenges in the era of NA. First, the risk of hepatocellular carcinoma can only be reduced but not eliminated, particularly among cirrhotic patients. For cirrhotic patients who have persistent low-level viremia on NA, that is, partial responders, the risk of hepatocellular carcinoma is higher than those with complete viral suppression. The best strategy to manage partial responders to entecavir or tenofovir is uncertain. Second, immune-tolerant patients are very difficult to treat with NA. A significant proportion of immune-tolerant patients will have detectable viremia despite a few years of continuous NA treatment, and the rate of hepatitis B e-antigen seroconversion is very low. Third, most patients need long-term treatment as NA cannot eliminate covalently closed circular DNA in the hepatocytes. Some patients can consider stop NA according to treatment guidelines, but viral and clinical relapses often occur after treatment cessation. There is no concrete consensus on when one should stop NA in a hepatitis B e-antigen-negative patient among different treatment guidelines. New biomarkers such as hepatitis B surface antigen level can be used to select patients to stop NA, but the data are still preliminary.

Unmet need in chronic hepatitis B management

Despite all these exciting developments, there remain some unmet needs in the management for patients with chronic hepatitis B (CHB). As majority of CHB patients are going to use oral nucleos(t)ide analogues (NAs) for decades, Safety profile of NAs is of no doubt an important issue. The newest nucleotide analogue tenofovir alafenamide is potent in terms of viral suppression, together with favourable renal and bone safety profile. Biochemical response as reflected by alanine aminotransferase (ALT) normalization is recently found to be prognostically important. Patients who achieved ALT normalization have reduced the risk of hepatic events by 49%. Functional cure as reflected by hepatitis B surface antigen seroclearance not only implies patients may stop NA treatment, it also confers to a reduced risk of hepatocellular carcinoma and other hepatic events. Hence functional cure should be the ultimate treatment goal in CHB patients. Preemptive antiviral treatment may reduce mother-to-child transmission of hepatitis B virus, especially if birth dose of vaccination cannot be given in the first two hours after delivery. Lastly, despite the currently first-line NAs have high-genetic barrier to drug resistance mutations, there are still are many patients who were previously treated with low barrier of resistance including lamivudine, telbivudine or adefovir dipivoxil which could lead to antiviral resistance and affecting the choice of NAs.

Spontaneous loss of surface antigen among adults living with chronic hepatitis B virus infection: a systematic review and pooled meta-analyses

BACKGROUND

Spontaneous loss of HBsAg (known as functional cure) in patients with chronic hepatitis B virus (HBV) infection significantly reduces liver-related complications. HBsAg loss has been suggested to be higher in non-endemic regions than in endemic regions in individual studies. We systematically determined a pooled annual rate of HBsAg loss in adults with untreated chronic HBV infection and examined the effect of regional endemicity.

METHODS

In this systematic review and meta-analysis, we searched PubMed and Embase for observational cohort studies and non-treatment arms of randomised controlled trials reporting proportions of patients with chronic HBV infection that achieved spontaneous HBsAg loss, published up to Oct 1, 2018. We excluded randomised controlled trials from meta-analyses because of substantial cohort differences. Two reviewers (KZ and CC) independently extracted data from accepted full-text studies, with discrepancies discussed with a third reviewer (NT). We assessed rate of HBsAg loss, and stratified results by whether the underlying cohort arose primarily from an endemic region (defined as having prevalence of chronic HBV greater than 2%) or non-endemic region. This study is registered with PROSPERO, number CRD42018074086.

FINDINGS

Of 5186 studies screened, 67 (11 randomised controlled trials, 39 prospective and 17 retrospective cohort studies) met the inclusion criteria and 56 were included in meta-analyses after exclusion of randomised controlled trials. Spontaneous HBsAg loss occurred in 3837 (7·8%) of 48 972 patients, with cumulative 352 381 person-years of follow-up. The pooled annual incidence of HBsAg loss was 1·17% (95% CI 0·94-1·41, I²=97%). Rates did not differ by endemicity: 1·19% (0·88-1·54) in endemic versus 1·29% (0·99-1·62) in non-endemic cohorts.

INTERPRETATION

Globally, spontaneous HBsAg loss occurs infrequently (about 1% per year) in treatment-naive adults with chronic HBV infection. The low and homogeneous rate of HBsAg loss highlights the need for new therapeutics aimed at achieving functional cure across different patient groups and geographical regions.

FUNDING

NIH National Institute of Diabetes and Digestive and Kidney Diseases.

Switching to peginterferon for chronic hepatitis B patients with hepatitis B e antigen seroconversion on entecavir - A prospective study

Nucleos(t)ide analogues (NA) are effective in suppressing hepatitis B virus (HBV) replication, but most patients require long-term treatment. This study aimed to investigate switching to peginterferon as a strategy to stop NA. Hepatitis B e antigen (HBeAg)-positive chronic hepatitis B patients who developed HBeAg seroconversion during NA treatment were studied. All patients received open-label peginterferon alfa-2a 180 μg/wk for 48 weeks, and NA was stopped at week 4 of peginterferon treatment. The primary endpoint was sustained response, which was defined as negative HBeAg, positive anti-HBe and HBV DNA <2000 IU/mL at week 72. Other secondary endpoints including HBsAg loss at week 72 were also studied. Forty-one patients treated with entecavir for 56 ± 23 months were recruited. Sustained response was achieved in 30 patients (73%, 95% confidence interval 58%-84%). At week 72, 31 (76%) patients had HBeAg seroconversion, 56 (23%) patients had undetectable HBV DNA, 31 (76%) patients had normal ALT, and 6 patients (15%) had HBsAg loss. Baseline HBsAg level was the best predictor for both sustained response and HBsAg loss; the best HBsAg cut-off for sustained response was <1500 IU/mL and that for HBsAg loss was <500 IU/mL by receiver operating characteristic curve analysis. Twenty-two of 25 (88%) patients with baseline HBsAg <1500 IU/mL had sustained response. Five of 10 (50%) patients with baseline HBsAg <500 IU/mL developed HBsAg loss. Switching to peginterferon can be considered as a treatment option in NA-treated patients with HBeAg seroconversion, particularly among those with lower HBsAg levels.

Hepatitis B Virus Serum DNA andRNA Levels in Nucleos(t)ide Analog-Treated or Untreated Patients During Chronic and Acute Infection

Treatment of chronic hepatitis B (CHB) patients with nucleos(t)ide analogs (NAs) suppresses hepatitis B virus (HBV) DNA synthesis but does not affect synthesis of HBV pregenomic RNA (pgRNA). Hepatitis B virus pgRNA is detectable in the serum during NA treatment and has been proposed as a marker of HBV covalently closed circular DNA activity within the infected hepatocyte. We developed an automated assay for the quantification of serum HBV pgRNA using a dual-target real-time quantitative PCR approach on the Abbott m2000sp/rt system. We demonstrate accurate detection and quantification of serum HBV RNA. Hepatitis B virus DNA was quantified using the Abbott RealTime HBV viral load assay. We further compared serum nucleic acid levels and kinetics in HBV-positive populations. Samples included on-therapy CHB samples (n = 16), samples (n = 89) from 10 treatment naïve CHB subjects receiving 12 weeks of NA treatment with 8-week follow-up, hepatitis B surface antigen-positive blood donor samples (n = 102), and three seroconversion series from plasmapheresis donors (n = 79 samples). Conclusion: During NA treatment of CHB subjects, we observed low correlation of HBV DNA to pgRNA levels; pgRNA concentration was generally higher than HBV DNA concentrations. In contrast, when NA treatment was absent we observed serum pgRNA at concentrations that correlated to HBV DNA and were approximately 2 log lower than HBV DNA. Importantly, we observe this trend in untreated subject samples from both chronic infections and throughout seroconversion during acute infection. Results demonstrate that the presence of pgRNA in serum is part of the HBV lifecycle; constant relative detection of pgRNA and HBV DNA in the serum is suggestive of a linked mechanism for egress for HBV DNA or pgRNA containing virions.

HIV, HCV and HBV: A Review of Parallels and Differences

Elimination of the three blood-borne viruses-human immunodeficiency virus (HIV), hepatitis B (HBV) and hepatitis C (HCV)-as public health issues may be plausible in the near future. Spectacular advances have been made with the introduction of highly effective antiviral agents into clinical practice, and prevention strategies are available for all three infections. Effective disease control, laid out by WHO global strategies, is currently feasible for all three viruses. However, for worldwide elimination of these viruses, effective vaccines are required that are currently only available for HBV. In this review differences and parallels among HIV, HCV and HBV will be discussed with a focus on virologic and therapeutic issues, and prospects for the future of HBV will be presented.

HBV antigen and DNA loss from mouse serum is associated with novel vaccine-induced HBV surface antigen-specific cell-mediated immunity and cytokine production

Therapeutic vaccination is a promising strategy for controlling chronic hepatitis B virus (HBV). Here, we tested whether several novel vaccination strategies could be used to induce HBV-specific adaptive immune responses and control/eradicate HBV in a mouse model. Robust HBV antigen-specific antibody responses were elicited by several vaccination strategies using a novel particle vaccine (HBSS1), which expresses a fusion of the S (amino acids [aa] 1-223) and preS1 (aa 21-47) antigens, and/or a recombinant adenovirus rAdSS1 vaccine. However, antigen-specific cell-mediated immunity and high levels of production of multiple cytokines were elicited only by heterologous prime-boost immunization; i.e., priming with the HBSS1 vaccine followed by a rAdSS1 boost. Furthermore, the most rapid loss of serum HBsAg, HBeAg and DNA was achieved by the novel vaccination regimen (priming with HBSS1 formulated with adjuvants [alum plus PolyI:C]), which was strongly associated with more potent and functional HBsAg-specific CD4⁺ and CD8⁺ T-cell responses and increased production of interleukin (IL)-2, interferon (IFN)-γ, tumor necrosis factor-α, IL-12, and IFN-γ-induced protein (IP)-10. Thus, our novel heterogeneous prime-boost vaccine regimen shows promise as a therapeutic strategy against HBV.

HBx-Derived Constrained Peptides Inhibit the Secretion of Hepatitis B Virus Antigens

Hepatitis B virus (HBV) infection is the primary cause of cirrhosis and liver cancer. Protein-protein interactions (PPIs) between HBV x protein (HBx) and its host targets, including Bcl-2, are important for cell death and viral replication. No modulators targeting these PPIs have been reported yet. Here, we developed HBx-derived constrained peptides generated by a facile macrocyclization method by joining two methionine side chains of unprotected peptides with chemoselective alkylating linkers. The resulting constrained peptides with improved cell permeability and binding affinity were effective anti-HBV modulators by blocking the secretion of viral antigens. This study clearly demonstrated HBx as a potentially important PPI target and the potential application of this efficient peptide macrocyclization strategy for targeting key PPIs.

New viral biomarkers for Hepatitis B: Are we able to change practice?

The management of chronic hepatitis B virus (HBV) infection is challenged by its varying natural course and its stealthy nature. Not all HBV-infected patients will develop complications of infection; however, it is of utmost importance to identify patients who are at risk and require antiviral treatment and/or close surveillance. Hepatic inflammation and quantification of HBV DNA have guided treatment decisions in the last decade, and these guided interventions have been shown to reduce liver-related complications and death. Data on the quantification of additional HBV markers such as hepatitis B surface antigen (HBsAg), hepatitis B core-related antigen (HBcrAg) and hepatitis B virus RNA (HBV RNA) have accumulated in recent years. Here, we review the current evidence of how to use these markers and discuss open issues that require additional research.

Liver-Targeted Co-delivery of Entecavir and Glycyrrhetinic Acid Based on Albumin Nanoparticle To Enhance the Accumulation of Entecavir

Hepatitis B, one of the most common contagious viral hepatitis with high infection rate, is challenging to treat. Although the treatment for hepatitis B has been improved over the years, many therapeutic drugs still have either severe adverse effects or insufficient effectiveness via systemic administration. In this study, we confirmed that glycyrrhetinic acid can enhance the accumulation of entecavir in HepaRG cell and liver. Then we constructed a novel albumin nanoparticle co-loading entecavir and glycyrrhetinic acid (ETV-GA-AN) to improve liver accumulation of entecavir and investigated its ability to deliver both drugs to liver. In vitro cellular uptake study and in vivo tissue distribution experiment showed that these negatively charged ETV-GA-AN (112 ± 2 nm in diameter) can increase the accumulation of entecavir in hepatic HepaRG cells and improve entecavir distribution in liver. We also revealed the mechanism that glycyrrhetinic acid enhances intracellular accumulation of entecavir by inhibiting the activity of specific efflux transporters. Our delivery system is the first liver-targeted albumin nanoparticle that utilizes the site-specific co-delivery strategy to delivery entecavir and glycyrrhetinic acid. As it combines high efficiency and low toxicity, it possess great potential for treating hepatitis B.

Hepatitis B virus infection: Defective surface antigen expression and pathogenesis

Hepatitis B virus (HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.

When Hepatitis B Virus Meets Interferons

Chronic hepatitis B virus (HBV) infection imposes a severe burden on global public health. Currently, there are no curative therapies for millions of chronic HBV-infected patients (Lok et al., 2017). Interferon (IFN; including pegylated IFN) is an approved anti-HBV drug that not only exerts direct antiviral activity, but also augments immunity against HBV infection. Through a systematic review of the literature, here we summarize and present recent progress in research regarding the interactions between IFN and HBV as well as dissect the antiviral mechanisms of IFN. We focus on inhibition of HBV replication by IFN-stimulated genes (ISGs) as well as inhibition of IFN signaling by HBV and viral proteins. Finally, we briefly discuss current IFN-based HBV treatment strategies. This review may help to better understand the mechanisms involved in the therapeutic action of IFN as well as the crosstalk between IFN and HBV, and facilitate the development of both direct-acting and immunology-based new HBV drugs.

Modulators of innate immunity as novel therapeutics for treatment of chronic hepatitis B

The first line defense mechanisms against viral infection are mediated by the innate immune system. Viral components are detected by infected cells and/or innate immune cells that express different sensory receptors. They in turn mediate induction of direct antiviral mechanisms and further modulation of innate and adaptive immune responses. For evading the innate system, most viruses have evolved efficient mechanisms to block sensing and/or antiviral functions of the innate response. Interestingly, hepatitis B virus (HBV) seems to act like a stealth virus that escapes cell intrinsic antiviral mechanisms through avoiding recognition by the innate system rather than blocking its effector functions. In line with this concept, agonistic activation of innate immunity has emerged as a promising novel anti-HBV therapy approach with several compounds having advanced to the clinical stage.

Overcoming immune tolerance in chronic hepatitis B by therapeutic vaccination

The currently used nucleoside analogs (i.e. entecavir and tenofovir) with high barrier-to-resistance efficiently suppress viral replication, limit inflammation and reduce the sequelae of chronic hepatitis B, but cannot cure the disease and thus have to be applied long-term. Therapeutic vaccination as an approach to cure chronic hepatitis B has shown promising pre-clinical results, nevertheless the proof of its efficacy in clinical trials is still missing. This may be partially due to suboptimal vaccine design. A main obstacle in chronic hepatitis B, however, is the high load of viral antigens expressed and secreted, which has been proposed to cause antigen-specific immune tolerance. Reduction of the viral antigen load is therefore considered a key factor for success of immune-based therapies. Although nucleoside analogs do not reduce viral antigen expression, new antiviral strategies are becoming available. Targeting viral translation by siRNA or targeting release of HBsAg from infected hepatocytes by nucleic acid polymers both reduce the antigen load. They may be considered as pre-treatment for therapeutic vaccination to increase the potential to elicit an HBV-specific immune response able to control and cure chronic HBV infection.

Why, who and when to start treatment for chronic hepatitis B infection

Chronic hepatitis B remains a major global health challenge due to morbidity and mortality from hepatocellular carcinoma and complications of liver cirrhosis. Current treatment regimens are non-curative and, once initiated, treatment is of indefinite duration for the majority. The decision to initiate treatment decisions is based on risk stratification. Advances in our understanding of the natural history of chronic hepatitis B have led to a paradigm shift in recommendations for treatment. Emerging non-invasive biomarkers of disease activity will further enhance disease stratification. In this review, we summarise the guidance from major international societies on treatment for chronic hepatitis B and explore some of the novel approaches to disease assessment.

An Overview of Hepatitis B Virus Surface Antigen Secretion Inhibitors

Current anti-hepatitis B virus (HBV) regimen do not meet ideal result due to emerging resistance strains, cytotoxicity, and unfavorable adverse effects. In chronic HBV infection, high rates of sub-viral particles (SVPs) bearing HBV surface antigen (HBsAg) is a major obstacle regarding to raise effective immune responses and subsequently virus clearance. Development of potent HBsAg secretion inhibitors would provide a better insight into HBV immunopathogenesis and therapy. Investigating new non-toxic HBsAg secretion inhibitors targeting either viral or cellular factors could restore the immune response to remove virally infected hepatocytes after inhibiting SVPs. In this study, we overview several classes of HBV inhibitors with focus on their limitations and advantages over anti-HBsAg secretion potential.

Towards HBV curative therapies

Tremendous progress has been made over the last 2 decades to discover and develop approaches to control hepatitis B virus (HBV) infections and to prevent the development of hepatocellular carcinoma using various interferons and small molecules as antiviral agents. However, none of these agents have significant impact on eliminating HBV from infected cells. Currently the emphasis is on silencing or eliminating cccDNA, which could lead to a cure for HBV. Various approaches are being developed including the development of capsid effectors, CRISPR/Cas9, TALENS, siRNA, entry and secretion inhibitors, as well as immunological approaches. It is very likely that a combination of these modalities will need to be employed to successfully eliminate HBV or prevent virus rebound on discontinuation of therapy. In the next 5 years clinical data will emerge which will provide insight on the safety and feasibility of these approaches and if they can be applied to eradicate HBV infections globally. In this review, we summarize current treatments and we highlight and examine recent therapeutic strategies that are currently being evaluated at the preclinical and clinical stage.

How to improve long-term outcome after liver transplantation?

The outcome of liver transplantation has markedly improved in the last 3 decades. Although early post-transplantation outcomes have improved over time, this is not true of the long-term outcome. The majority of late deaths are not related to graft dysfunction, and with the advent of new antiviral agents, recurrence of hepatitis B and hepatitis C after transplantation may no longer represent a source of graft loss and patient's death in the long term. The complications of metabolic syndrome may represent an increasing source of morbidity and mortality after transplantation. This study discusses these modifiable factors associated with late mortality to improve the long-term results of transplantation.