X-ray Structural andBiological Evaluationof a Series of Potent and Highly Selective Inhibitors of Human CoronavirusPapain-like Proteases.

Structure-guideddesign was used to generate a series of noncovalentinhibitors with nanomolar potency against the papain-like protease(PLpro) from the SARS coronavirus (CoV). A number of inhibitors exhibitantiviral activity against SARS-CoV infected Vero E6 cells and broadenedspecificity toward the homologous PLP2 enzyme from the human coronavirusNL63. Selectivity and cytotoxicity studies established a more than100-fold preference for the coronaviral enzyme over homologous humandeubiquitinating enzymes (DUBs), and no significant cytotoxicity inVero E6 and HEK293 cell lines is observed. X-ray structural analysesof inhibitor-bound crystal structures revealed subtle differencesbetween binding modes of the initial benzodioxolane lead (15g) and the most potent analogues 3kand 3j, featuring a monofluoro substitution at para and meta positionsof the benzyl ring, respectively. Finally, the less lipophilic bis(amide) 3eand methoxypyridine 5cexhibit significantlyimproved metabolic stability and are viable candidates for advancingto in vivo studies. [ABSTRACT FROM AUTHOR]