ABSTRACT
The αvß6 integrin plays a key role in the activation of transforming growth factor-ß (TGFß), a pro-fibrotic mediator that is pivotal to the development of idiopathic pulmonary fibrosis (IPF). We identified a selective small molecule αvß6 RGD-mimetic, GSK3008348, and profiled it in a range of disease relevant pre-clinical systems. To understand the relationship between target engagement and inhibition of fibrosis, we measured pharmacodynamic and disease-related end points. Here, we report, GSK3008348 binds to αvß6 with high affinity in human IPF lung and reduces downstream pro-fibrotic TGFß signaling to normal levels. In human lung epithelial cells, GSK3008348 induces rapid internalization and lysosomal degradation of the αvß6 integrin. In the murine bleomycin-induced lung fibrosis model, GSK3008348 engages αvß6, induces prolonged inhibition of TGFß signaling and reduces lung collagen deposition and serum C3M, a marker of IPF disease progression. These studies highlight the potential of inhaled GSK3008348 as an anti-fibrotic therapy.
Subject(s)
Butyrates/pharmacology , Idiopathic Pulmonary Fibrosis/drug therapy , Integrins/antagonists & inhibitors , Naphthyridines/pharmacology , Pyrazoles/pharmacology , Pyrrolidines/pharmacology , Administration, Inhalation , Animals , Antigens, Neoplasm/metabolism , Bleomycin/toxicity , Butyrates/administration & dosage , Butyrates/metabolism , Butyrates/pharmacokinetics , Collagen/metabolism , Disease Models, Animal , Epithelial Cells/drug effects , Humans , Idiopathic Pulmonary Fibrosis/chemically induced , Idiopathic Pulmonary Fibrosis/pathology , Integrins/metabolism , Male , Mice, Inbred C57BL , Molecular Docking Simulation , Naphthyridines/administration & dosage , Naphthyridines/metabolism , Naphthyridines/pharmacokinetics , Pyrazoles/administration & dosage , Pyrazoles/metabolism , Pyrazoles/pharmacokinetics , Pyrrolidines/administration & dosage , Pyrrolidines/metabolism , Pyrrolidines/pharmacokinetics , Small Molecule Libraries/chemistry , Small Molecule Libraries/pharmacology , Tomography, Emission-Computed, Single-Photon , Transforming Growth Factor beta/metabolism , Translational Research, BiomedicalABSTRACT
The alpha-v beta-6 (αvß6) integrin has been identified as playing a key role in the activation of transforming growth factor-ß (TGFß) that is hypothesised to be pivotal in the development of cancer and fibrotic diseases. Therefore, the αvß6 integrin is an attractive therapeutic target for these debilitating diseases and a drug discovery programme to identify small molecule αvß6 selective arginyl-glycinyl-aspartic acid (RGD)-mimetics was initiated within GlaxoSmithKline. The primary aim of this study was to pharmacologically characterise the binding to αvß6 of a novel clinical candidate, compound 1, using a radiolabelled form. Radioligand binding studies were completed with [(3)H]compound 1 against the human and mouse soluble protein forms of αvß6 to determine accurate affinity estimates and binding kinetics. The selectivity of compound 1 for the RGD integrin family was also determined using saturation binding studies (αvß1, αvß3, αvß5, αvß8, α5ß1 and α8ß1 integrins) and fibrinogen-induced platelet aggregation (αIIbß3 integrin). In addition, the relationship between divalent metal cation type and concentration and αvß6 RGD site binding was also investigated. Compound 1 has been demonstrated to bind with extremely high affinity and selectivity for the αvß6 integrin and has the potential as a clinical tool and therapeutic for investigating the role of αvß6 in a range of disease states both pre-clinically and clinically. In addition, this is the first study that has successfully applied radioligand binding to the RGD integrin field to accurately determine the affinity and selectivity profile of a small molecule RGD-mimetic.