Table 1.

IC₅₀ on HIF-1 and UPR activation and for selective cytotoxicity under glucose deprivation and physical parameters of phenethyl derivatives

Compound	R	IC50 of transactivation (μM)		IC50 of cytotoxicity (μM)c		${\text{pK}}_{\mathrm{a}}^{\mathrm{d}}$	clogD (pH 7.4)e
		HIF-1a	GRP78b	GIc (+)	GIc (−)
Phenformin (1)		27.4±6.1	107.8±9.4	976.2±95.0	46.2±9.2	12.2	−6.64
2		23.3±8.0	46.1±7.3	>1,000	87.6±4.2	13.1	−2.23
3		>100	>100	>100	>100	−0.2	0.81
4		>100	>100	>100	>100	1.2	−1.81

Notes:

^aIC₅₀ values for inhibition of HIF-1 activity were obtained using HEK293 p2.1 #3 cells under hypoxia (1% O₂) for 24 hours with the test compounds

^bIC₅₀ values for inhibition of GRP78 promoter activity were obtained using HEK293 GRP78 #85 cells treated with 0.3 mM 2-DG and the test compounds for 24 hours

^cIC₅₀ values from MTT assay using HT29 cells treated with the test compounds incubated in normal or glucose-free medium for 48 hours. Values are the mean ± SD of triplicate experiments

^dthe pK_a values of neutral–monocation equilibria were calculated by ACD/pK_a DB Product version 12.5 (Fujitsu Limited, Tokyo, Japan)

^ethe clogD values were calculated by DS Accord for Excel version 7.1.5 (Accelrys Software, Inc., Santa Clara, CA, USA).

Abbreviations: 2-DG, 2-deoxyglucose; GRP, glucose-regulated protein; HEK, human embryo kidney; HIF, hypoxia-inducible factor; IC_50, half maximal inhibitory concentration; clogD, calculated distribution coefficient; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; SD, standard deviation; UPR, unfolded protein response.