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

Hsu, John T.-A.; Kuo, Chih-Jung; Hsieh, Hsing-Pang; Wang, Yeau-Ching; Huang, Kuo-Kuei; Lin, Coney P.-C.; Huang, Ping-Fang; Chen, Xin; Liang, Po-Huang

3C-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 phenylmercuric acetate, as well as hexachlorophene. As well, 1–10 μM of 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 competitive inhibitors (K(i)=0.7, 2.4, and 13.7 μM for phenylmercuric acetate, thimerosal, and hexachlorophene, respectively). A panel of metal ions including Zn(2+) and its conjugates were then evaluated for their anti-3CL protease activities. Inhibition was more pronounced using a zinc-conjugated compound (1-hydroxypyridine-2-thione zinc; Ki=0.17 μM) than using the ion alone (Ki=1.1 μM).