Envisioning a hepatitis delta cure with new antivirals

Prospects for Controlling Hepatitis B Globally

Infection with the hepatitis B virus (HBV) is highly prevalent globally. Over 250 million people suffer from chronic hepatitis B, and more than 800,000 patients die each year due to hepatitis B complications, including liver cancer. Although protective HBV vaccines are recommended for all newborns, global coverage is suboptimal. In adults, sexual transmission is by far the most frequent route of contagion. The WHO estimates that 1.5 million new HBV infections occur annually. Oral nucleos(t)ide analogues entecavir and tenofovir are the most frequent antivirals prescribed as HBV therapy. Almost all patients adherent to the medication achieve undetectable plasma viremia beyond 6 months of monotherapy. However, less than 5% achieve anti-HBs seroconversion, and viral rebound occurs following drug discontinuation. Therefore, nucleos(t)ide analogues need to be lifelong. New long-acting formulations of tenofovir and entecavir are being developed that will maximize treatment benefit and overcome adherence barriers. Furthermore, new antiviral agents are in development, including entry inhibitors, capside assembly modulators, and RNA interference molecules. The use of combination therapy pursues a functional HBV cure, meaning it is negative for both circulating HBV-DNA and HBsAg. Even when this goal is achieved, the cccDNA reservoir within infected hepatocytes remains a signal of past infection, and HBV can reactivate under immune suppression. Therefore, new gene therapies, including gene editing, are eagerly being pursued to silence or definitively disrupt HBV genomes within infected hepatocytes and, in this way, ultimately cure hepatitis B. At this time, three actions can be taken to push HBV eradication globally: (1) expand universal newborn HBV vaccination; (2) perform once-in-life testing of all adults to identify susceptible HBV persons that could be vaccinated (or re-vaccinated) and unveil asymptomatic carriers that could benefit from treatment; and (3) provide earlier antiviral therapy to chronic HBV carriers, as being aviremic reduces the risk of both clinical progression and transmission.

Triple Threat: HDV, HBV, HIV Coinfection

Hepatitis delta virus (HDV) only infects patients with hepatitis B virus (HBV) due to its reliance on HBV surface proteins to form its envelope. With shared routes of transmission, HDV coinfection is estimated to occur in 15% of patients with HIV and HBV. However, HDV is often underdiagnosed and may be missed particularly in people living with HIV (PLWH) who are already on antiretroviral therapy with anti-HBV activity and coincidental HBV suppression. At the same time, HDV causes the most severe form of chronic viral hepatitis and leads to faster progression of liver disease and hepatocellular carcinoma. Thus, increased recognition and effective treatment are paramount, and as novel treatment options approach global markets, the study of their efficacy in PLWH should be pursued.

Treatment of hepatitis delta and HIV infection

Hepatitis delta virus (HDV) is a defective agent that only infects individuals with hepatitis B virus (HBV). Around 5-10% of chronic hepatitis B patients worldwide are superinfected with HDV, which means 15-25 million people. Hepatitis delta is the most severe of all chronic viral hepatitis, leading to cirrhosis, liver cancer and/or transplantation in most patients. Despite it, many HDV patients remain undiagnosed. The only treatment available until recently was peginterferon alfa, with poor results and significant side effects. The recent approval of bulevirtide, a lipopeptide that blocks HBV/HDV entry, has revolutionized the field. Another drug, lonafarnib, already approved to treat progeria, is expected to be available soon as HDV therapy. Since there is no cell reservoir for the HDV RNA genome, hypothetically viral clearance could be achieved if complete blocking of viral replication occurs for a minimum time frame. This is what happens in hepatitis C using direct-acting antivirals, with the achievement of cure in nearly all treated patients. We envision the cure of hepatitis delta using combination antiviral therapy. Given that sexual and parenteral transmission routes are the most frequent for the acquisition of HBV and HDV, shared with HIV infection and HBV/HDV and HIV coinfection. The clinical outcome of hepatitis delta is worst in the HIV setting, with more frequent liver complications. Since most persons infected with HIV are on regular health care follow-up, we propose that HIV-HDV patients should be prioritized for moving forward new and potentially curative treatments for hepatitis delta.

Emerging drugs for hepatitis D

INTRODUCTION

Chronic hepatitis delta (CHD) is the most severe form of chronic viral hepatitis. Until recently, its treatment consisted of pegylated interferon alfa (pegIFN) use.

AREAS COVERED

Current and new drugs for treating CHD. Virus entry inhibitor bulevirtide has received conditional approval by the European Medicines Agency. Prenylation inhibitor lonafarnib and pegIFN lambda are in phase 3 and nucleic acid polymers in phase 2 of drug development.

EXPERT OPINION

Bulevirtide appears to be safe. Its antiviral efficacy increases with treatment duration. Combining bulevirtide with pegIFN has the highest antiviral efficacy short-term. The prenylation inhibitor lonafarnib prevents hepatitis D virus assembly. It is associated with dose dependent gastrointestinal toxicity and is better used with ritonavir which increases liver lonafarnib concentrations. Lonafarnib also possesses immune modulatory properties which explains some post-treatment beneficial flare cases. Combining lonafarnib/ritonavir with pegIFN has superior antiviral efficacy. Nucleic acid polymers are amphipathic oligonucleotides whose effect appears to be a consequence of phosphorothioate modification of internucleotide linkages. These compounds led to HBsAg clearance in a sizeable proportion of patients. PegIFN lambda is associated with less IFN typical side effects. In a phase 2 study it led to 6 months off treatment viral response in one third of patients.

Hepatitis delta coinfection in persons with HIV: misdiagnosis and disease burden in Italy

Hepatitis Delta virus (HDV) causes severe liver disease. Due to similarities in transmission routes, persons living with HIV (PLWH) are at risk of HDV infection. This analysis investigates the prevalence and the long-term clinical outcome of people with HDV in a large cohort of PLWH. We retrieved HBsAg ± anti-HDV positive PLWH enrolled from 1997 to 2015 in the multicentre, prospective ICONA study. The primary endpoint was a composite clinical outcome (CCO = having experienced ≥1 of the following: Fib4 score >3.25; diagnosis of cirrhosis; decompensation; hepatocellular carcinoma or liver-related death). Kaplan-Meier curves and unweighted and weighted Cox regression models were used for data analysis. Less than half of HBsAg positive patients had been tested for anti-HDV in clinical practice. After testing stored sera, among 617 HBV/HIV cases, 115 (19%) were anti-HDV positive; 405 (65%) HBV monoinfected; 99 (16%) undeterminate. The prevalence declined over the observation period. HDV patients were more often males, intravenous drug users, HCV coinfected. After a median of 26 months, 55/115 (48%) developed CCO among HDV+; 98/403 (24%) among HBV monoinfected; 18/99 (18%) in HDV unknown (p < 0.001). After controlling for geographical region, alcohol consumption, CD4 count, anti-HCV status and IFN-based therapies, the association with HDV retained statistical significance [HR = 1.67 (1.15, 2.95; p = 0.025)]. HDV infection among PLWH is underdiagnosed, although HDV entails an high risk of liver disease progression. Because effective drugs to treat HDV are now available, it is even more crucial to identify PLWH at an early stage of liver disease.

Bulevirtide in the Treatment of Hepatitis Delta: Drug Discovery, Clinical Development and Place in Therapy

It has been ten years since the identification of NTCP as the cell surface receptor for HBV and HDV entry into hepatocytes. The search for molecules interfering with the binding of NTCP and HBV/HDV led to design bulevirtide (BLV). This large polypeptide mimics a region of the pre-S1 HBsAg and blocks viral entry by inhibitory competition. BLV was initially tested in cell cultures, animal models and more recently in Phase I-III human trials (called 'MYRS'). As monotherapy or in combination with peginterferon, BLV is well tolerated and exhibits potent antiviral activity. Plasma viremia significantly declines and/or becomes undetectable in more than 75% of patients treated for >24 weeks. However, serum HBsAg concentrations remain unchanged. No selection of BLV resistance in HBV/HDV has been reported in vivo to date. BLV is administered subcutaneously once daily at doses between 2 and 10 mg. BLV received conditional approval in Europe in 2020 to treat chronic hepatitis delta. The advent of peginterferon lambda or new specific anti-HDV antivirals (lonafarnib, etc.) will open the door for combination therapies with BLV. Since there is no stable reservoir for HDV-RNA within infected hepatocytes, viral clearance might be achieved using antivirals for a minimum timeframe. This is what happens in hepatitis C combining several antivirals, curing nearly all patients treated for 3 months. Clearance of HDV-RNA genomes may occur despite HBV persistence as cccDNA or chromosome integrated HBV-DNA within hepatocytes. This is supported by cases of HDV elimination using BLV despite persistence of serum HBsAg. Another path for HDV cure will derive from achieving HBsAg clearance, the goal of new promising anti-HBV gene therapies (bepirovirsen, etc.). In summary, the advent of BLV has triggered a renovated interest for antiviral therapy in hepatitis delta. We envision combination therapies that will lead to HDV cure in the near future.

Liver cancer and hepatic decompensation events in patients hospitalized with viral hepatitis in Spain

BACKGROUND

Chronic viral hepatitis B, C, and D are the main causes of decompensated cirrhosis and liver cancer worldwide. Newborn HBV vaccination was implemented more than 2 decades ago in most EU countries. Furthermore, potent oral antivirals have been available to treat HBV for 15 years and to cure HCV since 2014. The real-life clinical benefits of these interventions at country level have not been assessed, especially regarding major hepatic outcomes such as cirrhotic decompensation events and hepatocellular carcinoma (HCC).

METHODS

Retrospective study of all hospitalizations in Spain having HBV, HCV, and HDV as diagnosis using the Spanish National Registry of Hospital Discharges. Information was retrieved from 1997 up to 2017.

RESULTS

From a total of 73,939,642 hospital admissions during the study period, a diagnosis of HBV, HCV, and HDV was made in 124,915 (1.7‰), 981,985 (13.3‰), and 4850 (0.07‰) patients, respectively. The median age of patients hospitalized within each group was 53.2, 55.9, and 47.0 years, respectively. Significant increases in mean age at hospitalization occurred in all groups (0.6 years older per calendar year on average). The overall rate of hepatic decompensation events for HBV, HCV, and HDV was 12.1%, 14.1%, and 18.8%, respectively. For HCC hospitalizations, these figures were 6.7%, 8.0%, and 7.8%, respectively. Whereas, the rate of decompensation events declined in recent years for HBV, and more recently for HCV, it continued rising up for HDV. Likewise, liver cancer rates recently plateaued for HBV and HCV, but kept growing for HDV.

CONCLUSION

The rate of hepatic decompensation events and liver cancer has declined and/or plateaued in recent years for patients hospitalized with HBV and HCV infections, following the widespread use of oral antiviral therapies for these viruses. In contrast, the rate of decompensated cirrhotic events and HCC has kept rising up for patients with hepatitis delta, for which effective antiviral treatment does not exist yet.

Ultra-long-acting (XLA) antivirals for chronic viral hepatitis

Viral hepatitis is among the top four causes of mortality globally, causing 1.4 million deaths each year, exceeding tuberculosis, malaria and human immunodeficiency virus. Hepatitis B and C are responsible for 90% of hepatitis deaths, and the remaining 10% are caused by other hepatitis viruses. The annual number of deaths from hepatitis C is declining, whereas the numbers of deaths from hepatitis B and D are increasing. Hepatitis B alone represents the seven highest cause of mortality worldwide. Spurred on by development of curative antivirals for hepatitis C and expanding access to hepatitis B virus (HBV) vaccination, the World Health Organization has committed to eliminating viral hepatitis as a public health threat by 2030.

Like the majority of current antivirals, those available for HBV are virostatic. They are capable of suppressing viral replication but cannot eliminate the virus from infected patients. Therefore, treatment is lifelong. Long-term adherence to medication continues to represent a major challenge. Importantly, HBV often reactivates, leading to potential life-threatening events in immunosuppressed patients. Therapeutic options are limited for hepatitis D; however, promising new, effective antivirals are on the horizon.

Recent advances have emerged in medicinal chemistry and drug delivery approaches to produce ultra-long-acting (XLA) antivirals. These can extend antiviral activity from months to 1 year or even longer. These new formulations can overcome the challenges of daily dosing and maximize drug exposure. The development of XLA antivirals targeting viral hepatitis may also facilitate cure strategies.