Table 2. Enzyme versus cellular inhibitory activity of unsubstituted (23), homocarboxamide (66) and homosulfonamide (87) 2-arylamino-6-ethynylpurines.

Compound	R	IC50 (μM)	GI50 (μM)
		Nek2 a	U2OS	HeLa
23	Ph	0.14 ± 0.1	2.1 ± 1.0	1.2 ± 0.5
66		0.062 ± 0.01	71.0	47.1 ± 2.1
87		0.13	N.D.	N.D.

^aNek2 IC₅₀ values determined at 30 μM ATP concentration following a 30 minute incubation; N.D. not determined.