Table 1.

Cellular Sensitivity to Gimatecan (ST1481) and Topotecan.

Drug	Exposure Time	IC50 (ng/ml)*
		MCR	HT1376
Topotecan	1	900 ± 40	800 ± 20
ST1481	1	90 ± 3	9.0 ± 0.4
	1†	81 ± 20†	20 ± 9†
	24	5.0 ± 0.2	2.8 ± 0.1

^*IC₅₀ values were calculated from the dose-response curve.

^†Cells were exposed to the drug for the indicated times and the antiproliferative effects were determined after incubation in drug-free medium for 72 hours, with the cell counting method or SRB method.