Conformationally Constrained Isoquinolinones as Orally Efficacious Hepatitis B Capsid Assembly Modulators.

Isoquinolinone-based HBV capsid assembly modulators that bind at the dimer:dimer interface of HBV core protein have been shown to suppress viral replication in chronic hepatitis B patients. Analysis of their binding mode by protein X-ray crystallography has identified a region of the small molecule where the application of a constraint can lock the preferred binding conformation and has allowed for further optimization of this class of compounds. Key analogues demonstrated single digit nM EC values in reducing HBV DNA in a HepDE19 cellular assay in addition to favorable ADME and pharmacokinetic properties, leading to a high degree of oral efficacy in a relevant hydrodynamic injection mouse model of HBV infection, with effecting a 3 log decline in serum HBV DNA levels at a once daily dose of 1 mg/kg. Additionally, maintenance of activity was observed in clinically relevant HBV core protein variants T33N and I105T.