A potent GalNAc-siRNA drug, RBD1016, leads to sustained HBsAg reduction and seroconversion in mouse models of HBV...

Potent small interfering RNA (siRNA) drugs that could achieve hepatitis B surface antigen (HBsAg) seroconversion and functional cure are currently lacking. The purpose of this study is to evaluate the therapeutic potential of RBD1016, a novel GalNAc-conjugated siRNA drug targeting transcripts of hepatitis B virus (HBV), in animal models. RBD1016 was designed to target X gene of HBV (HBx) and showed strong activities on HBV DNA and HBsAg for multiple HBV genotypes and nucleoside-resistant viral strains in in vitro studies. Through single and repeated administration of RBD1016 in two different HBV animal models, a robust reduction of both serum HBsAg and HBV DNA (maximum reduction 3.7 log) was demonstrated. The durable anti-HBV effects of RBD1016 could still be observed on day 169. Importantly, repeated or single administration of RBD1016 caused de novo production of hepatitis B surface antibody (HBsAb), i.e., seroconversion in animals, which is an important hallmark of immune response induction. Furthermore, the combination of RBD1016 and entecavir (ETV) demonstrated an enhanced effect on serum HBV DNA inhibition. A strong and durable anti-HBV effect of RBD1016, both alone and in combination with nucleoside analogues (NAs), indicates significant therapeutic potential for chronic hepatitis B (CHB) patients.