title: Characterisation of a novel, high affinity and selective αvβ6 integrin RGD-mimetic radioligand.
abstract: The alpha-v beta-6 (αvβ6) integrin has been identified as playing a key role in the activation of transforming growth factor-β (TGFβ) that is hypothesised to be pivotal in the development of cancer and fibrotic diseases. Therefore, the αvβ6 integrin is an attractive therapeutic target for these debilitating diseases and a drug discovery programme to identify small molecule αvβ6 selective arginyl-glycinyl-aspartic acid (RGD)-mimetics was initiated within GlaxoSmithKline. The primary aim of this study was to pharmacologically characterise the binding to αvβ6 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 αvβ6 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 (αvβ1, αvβ3, αvβ5, αvβ8, α5β1 and α8β1 integrins) and fibrinogen-induced platelet aggregation (αIIbβ3 integrin). In addition, the relationship between divalent metal cation type and concentration and αvβ6 RGD site binding was also investigated. Compound 1 has been demonstrated to bind with extremely high affinity and selectivity for the αvβ6 integrin and has the potential as a clinical tool and therapeutic for investigating the role of αvβ6 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.
authors: Fibrosis and Lung Injury Discovery Performance Unit, Respiratory TAU, GlaxoSmithKline, Gunnels Wood Road, Stevenage, Hertfordshire, UK.
authors: Eleanor R
authors: ER
authors: Hall
authors: Fibrosis and Lung Injury Discovery Performance Unit, Respiratory TAU, GlaxoSmithKline, Gunnels Wood Road, Stevenage, Hertfordshire, UK.
authors: Lloyd I
authors: LI
authors: Bibby
authors: Fibrosis and Lung Injury Discovery Performance Unit, Respiratory TAU, GlaxoSmithKline, Gunnels Wood Road, Stevenage, Hertfordshire, UK. Electronic address: Robert.X.Slack@gsk.com.
authors: Robert J
authors: RJ
authors: Slack
mesh_terms: D000465:Algorithms; D000495:Allosteric Site; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism*; D001667:Binding, Competitive; D032701:Biomimetics / Q000379:methods; D005340:Fibrinogen / Q000037:antagonists & inhibitors / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D016023:Integrins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D051379:Mice; D009287:Naphthyridines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism*; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D014316:Tritium
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D016023:Integrins; D008024:Ligands; D009287:Naphthyridines; D009842:Oligopeptides; D010975:Platelet Aggregation Inhibitors; D011994:Recombinant Proteins; C073878:integrin alphavbeta6; D014316:Tritium; C047981:arginyl-glycyl-aspartic acid; D005340:Fibrinogen
keywords: Alpha-v beta-6 integrin; Binding kinetics; RGD integrin selectivity; RGD-mimetic; Radioligand binding