Radioligand binding studies were completed with [3H]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.