Design, synthesis and anti-HBV activity study of novel HBV capsid assembly modulators

Capsid assembly modulators (CAMs) have the potential to cure chronic hepatitis B, as demonstrated in clinical trials. Lead compounds NVR3-778 and 5a were found to exist in normal and flipped conformations through induced fit docking. Therefore, we designed and synthesized series I and II compounds by interchanging the amide and sulfonamide bonds of 5a to modify both the tolerance region and solvent-opening region. Among them, compound 4a (EC₅₀ = 0.24 ± 0.10 μM, CC₅₀ > 100 μM) exhibited potent anti-HBV activity with low toxicity, surpassing the lead compounds NVR3-778 (EC₅₀ = 0.29 ± 0.03 μM, CC₅₀ = 20.78 ± 2.29 μM) and 5a (EC₅₀ = 0.50 ± 0.07 μM, CC₅₀ = 48.16 ± 9.15 μM) in HepAD38 cells. Additionally, compared with the lead compound, 4a displayed a stronger inhibitory effect on HBV capsid protein assembly. Molecular dynamics (MD) simulations confirmed that the normal conformation of 4a had relatively stable conformation at different frames of binding modes. Furthermore, 4a showed better metabolic stability in human plasma than positive control drugs. Therefore, compound 4a could be further structurally modified as a potent lead compound.