Morphothiadine Mesylate

Interfering hepatitis B virus (HBV) capsid assembly holds promise as a therapeutic approach for chronic hepatitis B (CHB). Novel anti-HBV agents are urgently needed to overcome drug resistance challenges, with targeted protein degradation (TPD) emerging as a hopeful strategy. Herein, we report the first degradation of HBV core protein (HBC), a multifunctional structural protein, using small-molecule degraders developed by hydrophobic tagging (HyT) technology. Structure-activity relationship (SAR) analysis identified compound HyT-S7, featuring an adamantyl group, exhibiting potent inhibitory activity (EC₅₀ = 0.46 μmol/L, HepAD38 cells) and degradation ability (DC₅₀ = 3.02 ± 0.54 μmol/L) in a dose- and time-dependent manner. Mechanistic studies demonstrated that the autophagy-lysosome pathway was a potential driver of HyT-S7-induced HBC degradation. Remarkably, HyT-S7 effectively degraded 11 drug-resistant mutants, including highly resistant strains P25G and T33N, to Phase III drug GLS4. Furthermore, cellular thermal shift assay, surface plasmon resonance assay, and molecular dynamics simulations revealed the precise mode of HyT-S7 binding to HBC with the adamantyl group potentially mimicking protein misfolding to facilitate HBC degradation. This first proof-of-concept study highlights the potential of HyT-mediated TPD in HBC as a promising avenue for discovering novel HBV and other antiviral agents with favorable drug resistance profiles.

GLS4 is a first-in-class hepatitis B virus (HBV) capsid assembly modulator that inhibits HBV replication by interfering with assembly and disassembly of the virus nucleocapsid, this prospective, open-label, comparative, phase 2b trial evaluated the antiviral activity and safety of GLS4/ritonavir (RTV) combined with entecavir in hepatitis B e antigen-positive patients.

250 CHB patients were enrolled, including treatment-naïve patients and those interrupted anti-HBV drugs for ≥ 6 months (Part A, n=125), and patients who had taken ETV for ≥1 year and had achieved viral suppression (Part B, n=125). Patients were randomly allocated to receive 120 mg GLS4/100 mg RTV plus 0.5 mg ETV or 0.5 mg ETV monotherapy for 96 weeks.

In the mid-term, in Part A (n=122), greater least-squares mean (LSM) changes from baseline were observed in the GLS4/RTV plus ETV cohort than in ETV monotherapy cohort in HBV DNA (-6.28 vs -5.72 log10 IU/ml, p=0.0005), HBsAg (-0.87 vs -0.65 log10 IU/ml, p=0.0653), HBV pgRNA (-3.83 vs -1.91 log10 copies/ml, p<0.0001); The proportions of both HBV DNA and pgRNA negative patients were 17.3% (13/75, GLS4/RTV plus ETV) and 0% (0/30, ETV monotherapy). In Part B (n=123), greater mean LSM reductions in HBsAg (-0.17 vs -0.06 log10 IU/ml, p=0.0013), HBV pgRNA (-1.61 vs -0.28 log10 copies/ml, p<0.0001) were also observed in the GLS4/RTV+ETV cohort. the proportions of both HBV DNA and pgRNA-negative patients were 71.6% (48/67, GLS4/RTV plus ETV) and 18.9% (7/37, ETV monotherapy), respectively. No patients achieved HBsAg loss at week 48. GLS4/RTV + ETV were well tolerated, the most common adverse events were elevated alanine aminotransferase levels and hypertriglyceridemia, which were reversed by temporary GLS4/RTV discontinuation.

The primary analysis at week 48 showed that the antiviral efficacy of GLS4/RTV with ETV was clearly superior to that of ETV monotherapy. GLS4/RTV with ETV was well tolerated; further studies evaluating its safety and efficacy are ongoing. (clinical trial identifier: NCT04147208).