Table 2.

Activity of compounds against 3CL^pro of different human coronaviruses.

Cpd	hCoV-229E (Alpha-CoV) 3CLpro IC50 μM (pIC50 ± SD)	SARS-CoV-2 (Beta-CoV) 3CLpro IC50 μM (pIC50 ± SD)	SARS-CoV (Beta-CoV) 3CLpro IC50 μM (pIC50 ± SD)	MERS-CoV (Beta-CoV) 3CLpro IC50 μM (pIC50 ± SD)
1	0.016 (7.79 ± 0.14)	0.021 (7.67 ± 0.30)	0.383 (6.42 ± 0.18)	2.00 (5.70 ± 0.10)
1x	0.019 (7.73 ± 0.10)	0.027 (7.57 ± 0.22)	0.165 (6.78 ± 0.32)	1.36 (5.87 ± 0.21)
GC-376	0.028 (7.56 ± 0.09)	0.012 (7.92 ± 0.02)	0.161a (6.79 ± 0.43)	0.43 (6.37 ± 0.06)

Enzymatic assays were performed without GSH in the buffer. The enzymes were pre-incubated for 1 h with compound at increasing concentrations before starting the reaction with the substrate. Initial rates were used to calculate % inhibitions and IC₅₀ were obtained from concentration-response curves by a nonlinear regression analysis of the data. IC₅₀ values are averages of at least three independent experiments.

^an = 2.