Table 4.

2-Aminopyridines/pyrimidines CDK9 inhibitors published by Bayer.

Compound*	IC50 (nM)			mg/L	Efflux ratio in Caco2 permeability assay	Ref
	CDK9	CDK2	Cytotoxicityᶧ	Aqueous solubility
19	5	>20000	160	ND	ND	57
20	5	16200	157	ND	ND	57
21	2	2450	NT	ND	ND	58
22	3	3590	55	ND	ND	58
23	3	87	25	ND	ND	59
24	4	71	33	ND	ND	59
25	4	69	77	ND	ND	59
26	13	790	370	155	5.6	60
27	17	2300	309	1.2	1.1	60
28	4	400	142	2.2	1.6	60
29	15	1300	682	97	ND	60
30	4	400	140	2.2	1.6	60
31	20	20000	1050	ND	ND	61
32	13	410	3000	ND	ND	61

CDK: cyclin-dependent kinase; IC₅₀: half maximal inhibitory concentration; ND: not determined. *From corresponding structures in Figure 3. ᶧAverage of eight cell lines.