Table 2. Initial SAR Exploration.

			enzyme IC50 (μM)a			cell IC50 (μM)b
compd	R1	X	TGF-βRII	ACVR2A	ALK5	TGF-β	activin
5	H	CH	1.0	>20	NTc	>38	NT
6	H	N	0.0039	1.1	4.1	4.8	14
7	Me	N	0.0029	1.3	2.0	5.4	22
8	vinyl	N	<0.003 (82%)	0.19	1.4	0.38	4.1
9	Et	N	0.0015	0.70	1.9	1.3	11
10	c-Pr	N	0.0037	0.63	8.9	6.9	12
11	MeO	N	0.0010	0.31	0.71	0.33	4.8

^aIC₅₀ values are mean values determined from three replicates.

^bValues of IC₅₀ are mean values determined from four replicates.

^cNT = not tested.