Table 1.

Effects of (R)-Roscovitine, Purvalanol A and Its Four Analogues on the Catalytic Activity of Various CDKs^a

	IC50 (µM)b
Compound	CDK1/ cyclin B	CDK2/ cyclin A	CDK5/ p25	CDK7/ cyclin H	CDK9/ cyclin T
(R)-Roscovitine	0.33	0.22	0.27	0.80	0.23
Purvalanol A7a	0.004	0.070	0.075	NDc	ND
7a	0.073	0.04	0.07	0.50	0.043
7b	ND	ND	0.13	ND	ND
7c	0.08	0.06	0.06	> 100	> 100
13	0.40	0.22	0.32	0.60	0.20

^a(R)-Roscovitine and its analogues were tested at various concentrations for their effects on 5 CDKs.

^bIC₅₀ values were calculated from the dose-response curves and are reported in µM.

^cND, not determined.