Table 1.

IC₅₀ values (nM)^a of conjugate 1 compared with free SB-T-1214 and paclitaxel against cancer cell lines with varying levels of FR expression

	ID8b (FR+++)	MX-1c (FR++)	L1210-FRd (FR++)	WI-38e (FR−)
Paclitaxelf	13.8 ± 2.7	5.59 ± 2.12	27.6 ± 7.5	55.7 ± 9.5
SB-T-1214f	2.82 ± 0.70	1.89 ± 0.80	2.66 ± 1.33	4.89 ± 2.24
1f	2.52 ± 1.50	3.43 ± 2.23	3.51 ± 1.16	> 5,000
1g (GSH-OEt)	N.D.i	2.08 ± 1.30	3.35 ± 2.00	N.D.i
1h (GSH)	N.D.i	3.42 ± 2.98	3.87 ± 2.61	N.D.i

^aIC₅₀: concentration required for 50% growth inhibition;

^bmurine ovarian cancer cell line (FR⁺⁺⁺);

^chuman breast cancer cell line (FR⁺⁺);

^dmurine leukemia cell line (FR⁺⁺);

^ehuman lung fibroblasts (normal) cell line (FR−);

^fCells were incubated with each drug for 72 h.;

^gAfter cells were treated with 1 for 24 h, GSH-OEt (6 equiv.) was added and then incubated for another 48 h (Total 72 h);

^hAfter cells were treated with 1 for 24 h, GSH (6 equiv.) was added, and then incubated for another 48 h (total 72 h).

ⁱNot determined.