Evaluation of metal-conjugated compounds as inhibitors of 3CL protease of SARS-CoV

C-like (3CL) protease is essential for the life cycle of severe acute respiratory syndrome-coronavirus (SARS-CoV) and therefore represents a key anti-viral target. A compound library consisting of 960 commercially available drugs and biologically active substances was screened for inhibition of SARS-CoV 3CL protease. Potent inhibition was achieved using the mercury-containing compounds thimerosal and phenylmer- curic acetate, as well as hexachlorophene. As well, 1-10 l Mo f each compound inhibited viral replication in Vero E6 cell culture. Detailed mechanism studies using a fluorescence-based protease assay demonstrated that the three compounds acted as compet- itive inhibitors (Ki = 0.7, 2.4, and 13.7 lM for phenylmercuric acetate, thimerosal, and hexachlorophene, respectively). A panel of metal ions including Zn 2þ and its conjugates were then evaluated for their anti-3CL protease activities. Inhibition was more pronounced using a zinc-conjugated compound (1-hydroxy- pyridine-2-thione zinc; Ki =0 :17 lM) than using the ion alone (Ki =1 :1 lM). 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.