Small molecules targeting severe acute respiratory syndrome human coronavirus

doi:10.1073/pnas.0403596101

Small molecules targeting severe acute respiratory syndrome human coronavirus

^*Genomics Research Center and Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan; ^†Institute of Preventive Medicine, National Defense Medical Center, National Defense University, Taipei 114, Taiwan; ^§Department of Chemical Engineering, National Taipei University of Technology, Taipei 106, Taiwan; ^**Department of Chemistry, National Taiwan University, Taipei 106, Taiwan; ^¶Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037; and ^∥Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan

Contributed by Chi-Huey Wong, May 26, 2004

Abstract

Severe acute respiratory syndrome (SARS) is an infectious disease caused by a novel human coronavirus. Currently, no effective antiviral agents exist against this type of virus. A cell-based assay, with SARS virus and Vero E6 cells, was developed to screen existing drugs, natural products, and synthetic compounds to identify effective anti-SARS agents. Of >10,000 agents tested, ≈50 compounds were found active at 10 μM; among these compounds, two are existing drugs (Reserpine 13 and Aescin 5) and several are in clinical development. These 50 active compounds were tested again, and compounds 2–6, 10, and 13 showed active at 3 μM. The 50% inhibitory concentrations for the inhibition of viral replication (EC₅₀) and host growth (CC₅₀) were then measured and the selectivity index (SI = CC₅₀/EC₅₀) was determined. The EC₅₀, based on ELISA, and SI for Reserpine, Aescim, and Valinomycin are 3.4 μM (SI = 7.3), 6.0 μM (SI = 2.5), and 0.85 μM (SI = 80), respectively. Additional studies were carried out to further understand the mode of action of some active compounds, including ELISA, Western blot analysis, immunofluorescence and flow cytometry assays, and inhibition against the 3CL protease and viral entry. Of particular interest are the two anti-HIV agents, one as an entry blocker and the other as a 3CL protease inhibitor (K _i = 0.6 μM).

Footnotes

↵ ^‡To whom correspondence may be sent at the † address. E-mail: tsrong33{at}pchome.com.tw1. ^††To whom correspondence may be addressed at: The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, and Genomics Research Center, Academia Sinica, Taipei 115, Taiwan. E-mail: wong{at}scripps.edu or chwong{at}gate.sinica.edu.tw.
Abbreviations: SARS, severe acute respiratory syndrome; CoV, coronavirus; IFA, immunofluorescence assay; SI, selectivity index; MTS, 3-(4,5-dimethylthiazole-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt.