Table 5.

Cytotoxicity of second-generation taxoids with modifications at C1O (IC₅₀ nM)^a

Taxoid	R	LCC6-WTb	LCC6-MDRc	R/S
Paclitaxel	--	3.1	346	112
6a	Bz	1.8	4.8	2.7
6b		2.1	5.8	2.7
6c		2.8	5.1	1.8
6d		3.8	4.7	1.2
6e		2.1	5.7	2.7
6f		5.3	15.2	2.9
6g		6.3	15.2	2.4
6h	Cbz	1.8	16.7	9.3
6i		2.3	13.8	6.0
6j		2.1	20.3	9.7
6k		1.4	38.4	27.4
6l		5.1	31.2	6.1
6m		1.5	5.0	3.3
6n		3.7	6.7	1.8
6o		1.7	4.9	2.9

^aConcentration of compound which inhibits 50% (IC₅₀, nM) of the growth of human tumor cell line after 72 h drug exposure.

^bLCC6-WT: human breast carcinoma cell line (Pgp−).

^cLCC6-MDR: mdrl transduced cell line (Pgp+).

^dResistance factor = (IC₅₀ for drug resistant cell line, R)/(IC₅₀ for drug-sensitive cell line, S).