Inhibition of Hepatitis B Virus Replication by a Novel GalNAc-siRNA In Vivo and In Vitro

Current antiviral therapy for the chronic hepatitis B virus (HBV) has a low clinical cure rate, high administration frequency, and limited efficacy in reducing HBsAg levels, leading to poor patient compliance. Novel agents are required to achieve HBV functional cure, and reduction of HBV antigenemia may enhance the activation of effective and long-lasting host immune control. HT-101 is a siRNA currently in phase I clinical trials with promising prospects for future applications. By designing and synthesizing siRNA targeting the conserved HBV S region, we evaluated its inhibitory effect on HBV biomarkers across four different genotypes (A-D). Additionally, potential cytotoxic effects were investigated. The in vivo effects and duration of inhibition were assessed using a HBV/adeno-associated virus mouse model. The EC50 values for HBV DNA, HBsAg, HBeAg, and HBV RNA in the supernatant of HepG2.2.15 cells were determined to be 0.3348 0.1696, 4.329, and 2.831 nM, respectively, while the CC50 of HT-101 against the viability of Hep2, H1 HeLa, MRC-5, HEK293, and Huh7 cell lines all exceeded 1 mu M significantly. Compared with the vehicle group from days 7 to 70 postdosing, especially in the high-dose group (9 mpk), plasma levels of HBsAg, HBeAg, and HBV DNA were significantly reduced with mean reduction values ranging from 1.72 to 3.38 log10 copy/mL due to long-lasting suppression of HBsAg below the lower limit of quantitation (LLOQ), ultimately leading to induction of anti-HBs. In summary, the preclinical data demonstrate that HT-101 represents a significant breakthrough in reducing antigens and provides a promising strategy for functional cure of HBV.