Table 2. Hinge Binder Exploration in the Pyridazine Core.

compound	R	ALK5 pKia
2A	–	7.1 ± 0.65
4	2-NH2	8.5 ± 0.10
5	3-NH2	7.3 ± 0.24
6	2-CONH2	6.5 ± 0.02
7	3-CONH2	8.3 ± 0.27
8	2-OMe	6.1 ± 0.09
9	3-OMe	7.8 ± 0.09

^aPotency values are reported as arithmetic mean ± standard deviation from at least two independent experiments; all data were obtained as described in Table 1.