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P. C. Baciu, M. Ni, K. Lalwani, M. Ohlmeyer, E. Quadros, J. Liu, M. Webb, K. Appell; Predictive Value of Integrin vβ3 Antagonist Induced Talin Recruitment With in vivo Efficacy in Ocular Models of Neovascularization. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4593.
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© ARVO (1962-2015); The Authors (2016-present)
Investigate the induction of talin recruitment by integrin αvβ3 antagonists to predict in vivo efficacy in Rat Laser CNV and ROP models.
Starting from a αvβ3/αvβ5 integrin-selective library, 3 potent compounds, as defined by their ability to antagonize integrin-dependent binding and adhesion, were examined for efficacy in rat models of retinopathy of prematurity (ROP) and choroidal neovascularization (CNV). Compound dosing to achieve plasma levels 10-fold over the in vitro adhesion antagonist IC50s was conducted and monitored by analysis of terminal bleeds Quantitation of the neovascular response in both models was accomplished by visualizing choroidal or retinal flatmounts with IB4 lectin coupled to Alexa 488. Quantitation of the area of neovascularization was determined using Metamorph image analysis software. For analysis of talin recruitment, human umbilical vein endothelial cells (HUVEC) were treated with each of the compounds followed by immunocapture of the αvβ3 integrin complex and the levels of talin associated with the integrin determined by western blotting and quantitation using the Odyssey infrared image analysis system.
Three compounds (PS388023, PS780035 and PS680648) demonstrating similar antagonist IC50 values were initially tested in the rat ROP model. Two of the three compound (PS388023 and PS680648) inhibited the neovascular response >90%. The third compound (PS780035) failed to show inhibition. Consistent with this result, PS388023 was active and PS780035 was inactive in laser CNV model at comparable plasma concentrations. Analysis of talin recruitment demonstrated that compounds active in either ROP or CNV models induced a 6- to 7 -fold increase in talin association with αvβ3 integrin over controls, while inactive compounds induced a 2-fold enhancement in talin association
Defining antagonist activity of inhibitors targeting integrin αvβ3 using only binding/adhesion potencies is not predictive of in vivo efficacy. However, the ability of a compound to induce talin recruitment correlated with activity in either the ROP or CNV models. These studies suggest that development of in vivo active integrin antagonists need to account for signaling through the receptor as well as blocking receptor ligand interaction.
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