SD 208 is a potent, orally active ATP-competitive transforming growth factor-β receptor 1 (TGF-βRI) inhibitor (IC50= 49 nM); displays > 100-fold and > 17-fold selectivity over TGF-βRII and other common kinases respectively.

TGF-β is a cell growth and differentiation factor that has roles in cancer, fibrosis, and numerous other pathologies.TGF-β signals through two receptor tyrosine kinases, TGF-βRI and TGF-βRII. SD 208 is a potent inhibitor of TGF-βRI kinase (EC50 = 48 nM) that has minimal or no effect at a variety of other tyrosine or serine/threonine kinases, including TGF-βRII kinase.It blocks both autocrine and paracrine TGF-β signaling in glioma cells, inhibiting TGF-β-induced migration and invasion without affecting viability or proliferation.SD 208 is orally bioavailable and prevents TGF-β-induced Smad phosphorylation in spleens and brains of mice.It improves survival in mice with xenografted glioma by heightening the immune response against tumor cells and reverses bronchial hyperresponsiveness to allergens in ovalbumin-exposed mice.SD 208 also suppresses TGF-β-induced differentiation of proliferating myofibroblasts and induces dedifferentiation in the absence of TGF-β.