Normal development and tissue repair are controlled in part by SMADs, a family of intracellular proteins that are activated by signaling via serine/threonine kinase receptors of the TGF-β superfamily. LDN-193189 inhibits SMAD1/5/8 phosphorylation by the bone morphogenetic protein (BMP) type I receptors, which are known as activin receptor-like kinases (ALKs), with an IC50 value of 4.9 nM. In in vitro kinase assays, it shows specificity for ALK1, 2, 3, and 6 (IC50s = 0.8, 0.8, 5.3, and 16.7 nM, respectively) over ALK4 and 5 (IC50s = 101 and 350 nM, respectively). LDN-193189 has been used to inhibit BMP type I receptor activity to study the pathogenesis of fibrodysplasia ossificans progressive, a congenital hyperossification disorder, and to examine the role of osteogenesis in prostate tumor metastases in bone.
