NVR-3-778

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.

In recent years, hepatitis B virus (HBV) core protein allosteric modulators (CpAMs) have become a hot spot to develop new anti‐HBV drugs. Sulfonamide analogues are a new class of CpAMs targeting HBV core protein (Cp), while their biological activity is still needed to be improved and the binding mechanism is unclear still. In this study, we utilized molecular docking and molecular dynamics simulation to explore the binding mode between the novel compounds and HBV Cp. Combining with binding free energy calculation and decomposition, we inferred that TyrE132, ValE124, ThrE128, ThrD109, and IleD105 were key residues during the binding process, and especially, the conformational change of TryE132 was responsible for the stable binding. Besides, reasonable CoMFA (q2 = 0.515, r2ncv = 0.994, and r2pred = 0.628) and CoMSIA (q2 = 0.602, r2ncv = 0.988, and r2pred = 0.681) models were constructed to explore the 3D structure‐activity relationship of the novel compounds. The results suggested that it was favorable to increase the biological activity of sulfonamide analogues when introducing hydrophobic groups to R1 and electronegative groups to R2. In conclusion, we explored the binding mode and structure‐activity relationship between sulfonamides and HBV Cp and provided a theoretical basis for the optimization of this series of compounds.