Discovery\nof Non-Covalent Inhibitors for SARS-CoV‑2\nPLpro: Integrating Virtual Screening, Synthesis, and Experimental\nValidation

The SARS-CoV-2 pandemic has significantly challenged\nglobal public\nhealth, highlighting the need for effective therapeutic options. This\nstudy focuses on the papain-like protease (PLpro) of SARS-CoV-2, which\nis a critical enzyme for viral polyprotein processing, maturation,\nand immune evasion. We employed a combined approach that began with\ncomputational models in a virtual screening campaign, prioritizing\ncompounds from our in-house chemical library against PLpro. Out of\n81 virtual hits evaluated through enzymatic and biophysical assays,\nwe identified a modest inhibitor featuring a naphthyridine core with\nan IC<sub>50</sub> of 73.61 μM and a <i>K</i><sub>i</sub> of 22 μM. Expanding our exploration, we synthesized\nand assessed 30 naphthyridine analogues, three of which emerged as\npromising noncovalent, nonpeptidomimetic inhibitors with IC<sub>50</sub> values between 15.06 and 51.81 μM. Furthermore, <i>in\nvitro</i> ADMET assays revealed these compounds to possess moderate\naqueous solubility, low cytotoxicity, and high microsomal stability,\nmaking them excellent candidates for further development targeting\nSARS-CoV-2 PLpro.