Discovery of 3-phenyl-1H-5-pyrazolylamides as PLpro inhibitors through virtual screening and structure optimization

The papain-like protease (PLpro) of SARS-CoV-2 has been identified as a pivotal enzyme in viral replication, indicating it a promising target for drug discovery. Utilizing a virtual screening strategy, compound 1 with the N-(3-(5-amino-1H-pyrazol-3-yl)phenyl) benzenesulfonamide scaffold was discovered as a hit targeting PLpro. Structural modification from virtually screened hit 1 led to the development of a series of substituted 3-phenyl-1H-5-pyrazolylamide derivatives. Notably, compounds 14h and 14e exhibited improved PLpro inhibitory activity (IC₅₀ = 14.2 μM and 12.0 μM, respectively) and low cytotoxicity. Further biological evaluation revealed that compound 14e with a thiophene aldehyde group displayed potent binding activity (K_D = 1.86 μM). This 3-phenyl-1H-5-pyrazolylamide scaffold offers significant potential for further development as a novel class of PLpro inhibitors.