Glycoconjugates of adefovir and tenofovir as asialoglycoprotein-mediated Anti-HBV prodrugs with enhanced liver targeting

Abstract

Hepatitis B virus (HBV) infection remains a significant global health challenge, often leading to severe liver complications such as cirrhosis and cancer. Current treatments rely heavily on nucleos(t)ide analogues like adefovir and tenofovir due to their potent antiviral effects. However, their clinical utility is limited by insufficient liver targeting, leading to off-target side effects, particularly nephrotoxicity. To improve liver-specific drug delivery and reduce adverse effects, we designed novel liver-targeted prodrugs by conjugating adefovir and tenofovir with N-acetylgalactosamine (GalNAc) and tris-GalNAc ligands, which have high affinity for the asialoglycoprotein receptor (ASGPR) predominantly expressed in hepatocytes. Four prodrugs (A1, A2, T1, and T2) were synthesized and evaluated for cytotoxicity, maximum tolerated dose, anti-HBV activity, metabolic stability, pharmacokinetics, and liver-targeting properties. The prodrugs exhibited low cytotoxicity, robust anti-HBV activity, and enhanced selectivity compared to their parent drugs. Notably, the tris-GalNAc conjugates A2 and T2 demonstrated superior liver targeting, showing a threefold higher concentration in the liver compared to the kidneys, thus minimizing renal exposure. These findings suggest that GalNAc and tris-GalNAc conjugation is a promising strategy for enhancing the therapeutic efficacy and safety of adefovir and tenofovir, with potential for further optimization as liver-targeted anti-HBV prodrugs.

Keywords: Anti-HBV prodrugs; Asialoglycoprotein receptor; Liver targeting.