Table 1.

Cell growth inhibition (presented as IC₅₀ values in μM) induced by Hsp90 inhibitors with different affinity of binding to Hsp90.

Compound	NCI-H460	NCI-H460/R	DLD1	DLD1-TxR	MRC-5 #	Relative Selectivity RS	Hsp90 Affinity binding (μM) [15]	LogP
3	0.785 ± 0.032 *	0.599 ± 0.020 CS	0.925 ± 0.032	0.644 ± 0.020 CS	0.636 ± 0.023	NO	7.850	3.24
4	0.935 ± 0.048	0.579 ± 0.018 CS	1.523 ± 0.054	1.059 ± 0.025 CS	1.747 ± 0.083	1.71	5.840	3.08
5	5.722 ± 0.073	25.496 ± 0.925 R	5.683 ± 0.163	11.060 ± 0.304 R	127.677 ± 38.976	10.64	1.550	2.93
6	0.807 ± 0.035	0.472 ± 0.018 CS	0.439 ± 0.006	0.439 ± 0.010 E	4.737 ± 0.473	8.79	1.200	2.88
7	0.199 ± 0.005	0.231 ± 0.006 E	0.156 ± 0.004	0.138 ± 0.003 E	0.599 ± 0.015	3.31	0.390	2.02
8	0.159 ± 0.003	0.351 ± 0.005 R	0.251 ± 0.003	3.364 ± 0.049 R	11.021 ± 0.366	10.69	0.034	-0.20
9	0.096 ± 0.002	0.172 ± 0.005 R	0.045 ± 0.001	0.050 ± 0.001 E	0.302 ± 0.008	3.33	0.540	2.02
10	1.269 ± 0.014	1.375 ± 0.012 E	2.645 ± 0.035	1.787 ± 0.036 CS	0.257 ± 0.004	NO	1.060	2.40
13	1.250 ± 0.028	1.060 ± 0.012 E	1.895 ± 0.036	1.004 ± 0.016 CS	0.174 ± 0.004	NO	1.900	1.86
14	0.978 ± 0.018	23.597 ± 0.470 R	7.449 ± 0.212	10.632 ± 0.270 R	53.283 ± 1.729	5.00	0.340	–0.36
15	0.052 ± 0.002	0.039 ± 0.001 E	0.044 ± 0.001	0.193 ± 0.007 R	0.250 ± 0.014	3.05	0.084	1.63

* All values are presented as an average IC₅₀ from three independent experiments and given in μM. ^# MRC-5 human embryonic fibroblasts were used to determine relative selectivity to cancer cells. ^CS Collateral Sensitivity (IC₅₀ values lower in MDR cells than in corresponding sensitive cells). ^R Resistance (IC₅₀ values higher in MDR cells than in corresponding sensitive cells). ^E Evading resistance mechanisms (similar IC₅₀ values between MDR and corresponding sensitive cells). ^RS Relative selectivity towards cancer cells: A relation between IC₅₀ value obtained in MRC-5 cells and an average IC₅₀ value from four tested cancer cell lines.