Table 3.

(A) EC₅₀, CC₅₀, and SI index of 3 compounds of interest in MRC5 cells infected with HCoV-229E or HCoV-OC43.

HCoV strain	Compound	EC50 (μM)	CC50 (μM)	SI index
HCoV-229E	Tanespimycin	0.0036	0.182	101
	Bortezomib	0.2518	0.5364	2
	Homoharringtonine	0.05106	0.2046	4
HCoV-OC43	Tanespimycin	0.0019	0.2528	133
	Bortezomib	0.666	0.5914	< 1
	Homoharringtonine	0.1261	0.1670	1

Tanespimycin and homoharringtonine exhibited anti-HCoV-229E with tanespimycin’s EC₅₀ 101 times lower than its CC₅₀ and homoharringtonine 4 times lower. Tanespimycin was also effective against anti-HCoV-OC43 with an EC₅₀ 133 times lower than its CC₅₀. Bortezomib exhibited no anti-viral activity against either strain.