A 1120, a nonretinoid retinol-binding protein 4 (RBP4) antagonist, has a high affinity with the Ki value of 8.3 nM, which disrupts the interaction between RBP4 and its binding partner transthyretin[1][2].
The IC50 of A 1120 is 90 nM on human RBP4 and 66 nM on mouse RBP4[1].
References:
[1]. Motani A, et al. Identification and characterization of a non-retinoid ligand for retinol-binding protein 4 which lowers serum retinol-binding protein 4 levels in vivo. J Biol Chem. 2009 Mar 20;284(12):7673-80.
[2]. Dobri N, et al. A1120, a nonretinoid RBP4 antagonist, inhibits formation of cytotoxic bisretinoids in the animal model of enhanced retinal lipofuscinogenesis. Invest Ophthalmol Vis Sci. 2013 Jan 7;54(1):85-95.