Table 1.

Enzymatic inhibitory activities of thiazolo[5,4-b]pyridine derivatives 6a–w and 7a–h against c-KIT.

Entry	R1	R2	IC50 (μM) a	Entry	R1	R2	IC50 (μM) a
imatinib	-	-	0.27	6p		-	5.72
sunitinib	-	-	0.14	6q		-	3.23
6 a		-	inactiveb	6r		-	0.14
6b		-	inactiveb	6s		-	0.37
6c		-	inactiveb	6t		-	1.25
6d		-	inactiveb	6u		-	4.56
6e		-	inactiveb	6v		-	0.39
6f		-	inactiveb	6w		-	0.25
6g		-	inactiveb	7a		cyclohexyl	1.51
6h		-	9.87	7b		phenyl	0.74
6i		-	inactiveb	7c		methyl	0.10
6j		-	inactiveb	7d		cyclohexyl	inactiveb
6k		-	4.31	7e		methyl	0.88
6l		-	1.76	7f		methyl	3.63
6m		-	2.17	7g		methyl	0.18
6n		-	Inactive b	7h		methyl	0.10
6o		-	5.03

^a Radiometric biochemical kinase assay results. ^b less than 50% inhibition at a concentration of 10 μM.