LDN193189 is a small molecule inhibitor of BMP type I receptors ALK2 and ALK3 (IC50 = 5 nM and 30 nM respectively).
It only weakly inhibits ALK4, ALK5, and ALK7. LDN193189 functions primarily through prevention of Smad1, Smad5, and Smad8 phosphorylation.
BMP signaling coordinates developmental patterning and has essential physiological roles in mature organisms.