Pharmacological characterisation of a tool αvβ1 integrin small molecule RGD-mimetic inhibitor

Compound 8 is a selective alpha v beta 1 small molecule inhibitor that has been used in pre-clinical studies to identify and characterise the alpha v beta 1 integrin as a potential target in fibrotic disease. In this study we further investigated the selectivity and pharmacokinetics of compound 8 to determine a link between the levels of alpha v beta 1 engagement required to achieve in vivo pharmacodynamic efficacy. The selectivity of compound 8 for the arginyl-glycinyl-aspartic acid and beta 1 integrins was measured using purified integrin protein preparations in radioligand binding studies with both labelled ([H-3]compound 8) and unlabelled versions. The pharmacokinetic profile of compound 8 was completed in in vitro blood protein binding assays and in in vivo studies using male C57BL/6 mouse following i.v. dosing. The high selectivity of compound 8 for alpha v beta 1 over the other alpha v integrins was confirmed, however a reduced selectivity was demonstrated for the beta 1 integrin family, with high affinity observed for alpha 4 beta 1 (comparable to alpha v beta 1), moderate affinity for alpha 2 beta 1, alpha 3 beta 1 and alpha 8 beta 1, and low affinity for alpha 5 beta 1 and alpha 9 beta 1. Compound 8 was shown to be cleared quickly from the blood with a short half-life of 0.5 h. In conclusion, the data in this study suggest that compound 8 has the potential to engage a number of integrins in vivo beyond alpha v beta 1, that raises a degree of uncertainty regarding its mechanism of action in models of fibrotic disease.