A novel, small anti-HBV compound reduces HBsAg and HBV-DNA by destabilizing HBV-RNA

Clinical potential of SAG-524: A novel HBV RNA destabilizer with a unique mechanism of action

SAG-524 is a novel, oral HBV RNA destabilizer developed to address the limitations of treatment with nucleos(t)ide analogues (NAs), which are effective against HBV DNA but show limited efficacy in reducing hepatitis B surface antigen (HBsAg) levels. SAG-524 exerts its effect by destabilizing HBV RNA by shortening the poly(A) tail, which leads to a significant reduction of both pgRNA and PreS/S mRNA. This destabilization seems to be specific for HBV RNA molecules. The mechanism involves the recruitment of PAPD5/7 by ZCCHC14 to the HBV RNA, where guanine is incorporated into the poly(A) tail to protect against degradation. SAG-524 disrupts this process by directly targeting PAPD5, thus destabilizing HBV RNA. In preclinical trials, oral administration of SAG-524 reduced serum HBsAg levels in HBV-infected PXB mice. When combined with NAs or capsid assembly modulators (CAMs), significant reductions in HBsAg, HBV DNA, and intrahepatic covalently closed circular DNA were observed. Safety studies conducted over 13 weeks in mice and monkeys revealed no significant toxicity, demonstrating the drug demonstrated a favorable safety profile. In conclusion, the novel mechanism of action, high oral bioavailability, and strong suppression of HBsAg make SAG-524 a promising candidate for future therapeutic use. The potential for combination therapy with NAs or CAMs underscores its capacity to contribute to achieving a functional cure for chronic HBV infection.

Hepatitis B virus infection and its treatment in Eastern Ethiopia

Hepatitis B virus (HBV) infection causes acute and chronic hepatitis, compensated and decompensated cirrhosis, and hepatocellular carcinoma worldwide. The actual status of HBV infection and its treatment in certain regions of Asian and African countries, including Ethiopia, has not been well-documented thus far. Antiviral therapy for HBV infection can prevent the progression of HBV-related liver diseases and decrease the HBV-related symptoms, such as abdominal symptoms, fatigue, systemic symptoms and others. In Eastern Ethiopia, HBV-infected patients with cirrhosis were found to be positive for the HBV e antigen and to have a higher viral load than those without cirrhosis. Notably, 54.4% of patients practiced khat chewing and 18.1% consumed excessive amounts of alcohol. Tenofovir disoproxil fumarate effectively suppressed HBV DNA in those infected with HBV. It is important to elucidate the actual status of HBV infection in Eastern Ethiopia to eliminate HBV infection worldwide by 2030. HBV vaccination and the educational programs for Health Science students that provide practical strategies could help to reduce HBV infection in Eastern Ethiopia.

Progress of Infection and Replication Systems of Hepatitis B Virus

Despite the long-standing availability of effective prophylaxis, chronic hepatitis B virus (HBV) infection remains a formidable public health threat. Antiviral treatments can limit viral propagation, but prolonged therapy is necessary to control HBV replication. Robust in vitro models of HBV infection are indispensable prerequisites for elucidating viral pathogenesis, delineating virus-host interplay and developing novel therapeutic, preventative countermeasures. Buoyed by advances in molecular techniques and tissue culture systems, investigators have engineered numerous in vitro models of the HBV life cycle. However, all current platforms harbor limitations in the recapitulation of natural infection. In this article, we comprehensively review the HBV life cycle, provide an overview of existing in vitro HBV infection and replication systems, and succinctly present the benefits and caveats in each model with the primary objective of constructing refined experimental models that closely mimic native viral infection and offering robust support for the ambitious "elimination of hepatitis by 2030" initiative.

Preclinical Antiviral and Safety Profiling of the HBV RNA Destabilizer AB-161

HBV RNA destabilizers are a class of small-molecule compounds that target the noncanonical poly(A) RNA polymerases PAPD5 and PAPD7, resulting in HBV RNA degradation and the suppression of viral proteins including the hepatitis B surface antigen (HBsAg). AB-161 is a next-generation HBV RNA destabilizer with potent antiviral activity, inhibiting HBsAg expressed from cccDNA and integrated HBV DNA in HBV cell-based models. AB-161 exhibits broad HBV genotype coverage, maintains activity against variants resistant to nucleoside analogs, and shows additive effects on HBV replication when combined with other classes of HBV inhibitors. In AAV-HBV-transduced mice, the dose-dependent reduction of HBsAg correlated with concentrations of AB-161 in the liver reaching above its effective concentration mediating 90% inhibition (EC90), compared to concentrations in plasma which were substantially below its EC90, indicating that high liver exposure drives antiviral activities. In preclinical 13-week safety studies, minor non-adverse delays in sensory nerve conductance velocity were noted in the high-dose groups in rats and dogs. However, all nerve conduction metrics remained within physiologically normal ranges, with no neurobehavioral or histopathological findings. Despite the improved neurotoxicity profile, microscopic findings associated with male reproductive toxicity were detected in dogs, which subsequently led to the discontinuation of AB-161's clinical development.