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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2008;28:665.)
© 2008 American Heart Association, Inc.

Integrative Physiology/Experimental Medicine

SM16, an Orally Active TGF-β Type I Receptor Inhibitor Prevents Myofibroblast Induction and Vascular Fibrosis in the Rat Carotid Injury Model

Kai Fu; Michael J. Corbley; Lihong Sun; Jessica E. Friedman; Feng Shan; James L. Papadatos; Donald Costa; Frank Lutterodt; Harry Sweigard; Scott Bowes; Michael Choi; P. Ann Boriack-Sjodin; Robert M. Arduini; Dongyu Sun; Miki N. Newman; Xiamei Zhang; Jonathan N. Mead; Claudio E. Chuaqui; H. -Kam Cheung; Xin Zhang; Mark Cornebise; Mary Beth Carter; Serene Josiah; Juswinder Singh; Wen-Cherng Lee; Alan Gill; Leona E. Ling

From the Departments of Pharmacology (K.F., D.C., F.L., A.G.), Molecular and Cellular Biology (M.J.C., X.Z., J.N.M., H.-K.C., L.E.L.), Medicinal Chemistry (L.S., F.S., M.C., M.C., M.B.C., W.-C.L.), Assay Development and Compound Profiling (J.E.F., J.L.P., S.B., D.S., M.N.N., S.J.), Research Pathology (H.S.), Structural Biochemistry (P.A.B.-S.), Target Biochemistry (R.M.A.), and Structural Informatics (S.B., C.E.C., X.Z., J.S.) Biogen Idec, Cambridge, Mass.

Correspondence to Leona E. Ling, Biogen Idec, 14 Cambridge Center, Cambridge, MA 02142. E-mail leona.ling{at}biogenidec.com

Abstract

Objective— TGF-β plays a significant role in vascular injury-induced stenosis. This study evaluates the efficacy of a novel, small molecule inhibitor of ALK5/ALK4 kinase, in the rat carotid injury model of vascular fibrosis.

Methods and Results— The small molecule, SM16, was shown to bind with high affinity to ALK5 kinase ATP binding site using a competitive binding assay and biacore analysis. SM16 blocked TGF-β and activin-induced Smad2/3 phosphorylation and TGF-β-induced plasminogen activator inhibitor (PAI)-luciferase activity in cells. Good overall selectivity was demonstrated in a large panel of kinase assays, but SM16 also showed nanomolar inhibition of ALK4 and weak (micromolar) inhibition of Raf and p38. In the rat carotid injury model, SM16 dosed once daily orally at 15 or 30 mg/kg SM16 for 14 days caused significant inhibition of neointimal thickening and lumenal narrowing. SM16 also prevented induction of adventitial smooth muscle -actin–positive myofibroblasts and the production of intimal collagen, but did not decrease the percentage of proliferative cells.

Conclusion— These results are the first to demonstrate the efficacy of an orally active, small-molecule ALK5/ALK4 inhibitor in a vascular fibrosis model and suggest the potential therapeutic application of these inhibitors in vascular fibrosis.

Key Words: TGF beta • restenosis • fibrosis • neointimal formation • activin