Optimization and Synthesis of Pyridazinone Derivatives as Novel Inhibitors of Hepatitis B Virus by Inducing Genome-free Capsid Formation

The capsid of hepatitis B virus (HBV) plays a vital role in virus DNA replication. Targeting nucleocapsid function has been demonstrated as an effective approach for anti-HBV drug development. A high-throughput screening and mechanism study revealed the hit compound <b>4a</b> as an HBV assembly effector (AEf), which could inhibit HBV replication by inducing the formation of HBV DNA-free capsids. The subsequent SAR study and drug-like optimization resulted in the discovery of the lead candidate <b>4r</b>, with potent antiviral activity (IC₅₀ = 0.087 ± 0.002 μM), low cytotoxicity (CC₅₀ = 90.6 ± 2.06 μM), sensitivity to nucleoside analogue-resistant HBV mutants, and synergistic effect with nucleoside analogues in HepG2.2.15 cells

Discovery of Novel Small Molecule Inhibitors of Dengue Viral NS2B-NS3 Protease Using Virtual Screening and Scaffold Hopping

By virtual screening, compound <b>1</b> was found to be active against NS2B-NS3 protease (IC₅₀ = 13.12 ± 1.03 μM). Fourteen derivatives (<b>22</b>) of compound <b>1</b> were synthesized, leading to the discovery of four new inhibitors with biological activity. In order to expand the chemical diversity of the inhibitors, small-molecule-based scaffold hopping was performed on the basis of the common scaffold of compounds <b>1</b> and <b>22</b>. Twenty-one new compounds (<b>23</b>, <b>24</b>) containing quinoline (new scaffold) were designed and synthesized. Protease inhibition assays revealed that 12 compounds with the new scaffold are inhibitors of NS2B-NS3 protease. Taken together, 17 new compounds were discovered as NS2B-NS3 protease inhibitors with IC₅₀ values of 7.46 ± 1.15 to 48.59 ± 3.46 μM, and 8 compounds belonging to two different scaffolds are active to some extent against DENV based on luciferase reporter replicon-based assays. These novel chemical entities could serve as lead structures for discovering therapies against DENV