Development of acylhydrazone linked thiazoles as non-covalent dual inhibitors of SARS-CoV-2 proteases.

SARS-CoV-2's papain-like protease (PLPro) and main protease (MPro) are essential for viral maturation and replication. Currently, Paxlovid is recommended to treat viral infections, but the emergence of Nirmatrelvir resistance new variants poses serious global risks. Dual targeting agents restrict viral replication, act on other crucial viral pathways, or exert simultaneous protease inhibition, increasing the complexity for the virus to develop resistance, and the design of dual inhibitors is an attractive strategy. Herein, we present research on new thiazole-aryl and thiazole-ester compounds that function as cysteine specific non-covalent competitive dual inhibitors of SARS-CoV-2's papain-like protease (PLPro) and main protease (MPro). Twelve of the 36 compounds demonstrated dual inhibition in the range of nanomolar to low micromolar concentrations while five others exhibit selective PLPro inhibition. Minimal cytotoxicity against two mammalian cell lines and no oral toxicity in rats (LD50 > 2000 mg/kg) were observed. SARS-CoV-2 viral load was successfully reduced by several compounds tested. N-acyl hydrazone (NAH)-thiazole core while forms π-π interactions with the catalytic histidine side chain (H41) in MPro active site, it exhibits a series of hydrophobic and hydrophilic interaction in the interface of BL2 loop and the active site of PLPro. Non-covalent dual inhibition demonstrated by novel NAH-thiazole derivatives in this study provides a path for the development of efficient antiviral agents against coronaviruses.