Engen K, Rosenström U, Axelsson H, Konda V, Dahllund L, Otrocka M, Sigmundsson K, Nikolaou A, Vauquelin G, Hallberg M, Jenmalm Jensen A, Lundbäck T, Larhed M
Assay Drug Dev Technol 14 (3) 180-193 [2016-04-00; online 2016-04-15]
Intracerebroventricular injection of angiotensin IV, a ligand of insulin-regulated aminopeptidase (IRAP), has been shown to improve cognitive functions in several animal models. Consequently, IRAP is considered a potential target for treatment of cognitive disorders. To identify nonpeptidic IRAP inhibitors, we adapted an established enzymatic assay based on membrane preparations from Chinese hamster ovary cells and a synthetic peptide-like substrate for high-throughput screening purposes. The 384-well microplate-based absorbance assay was used to screen a diverse set of 10,500 compounds for their inhibitory capacity of IRAP. The assay performance was robust with Z'-values ranging from 0.81 to 0.91, and the screen resulted in 23 compounds that displayed greater than 60% inhibition at a compound concentration of 10 μM. After hit confirmation experiments, purity analysis, and promiscuity investigations, three structurally different compounds were considered particularly interesting as starting points for the development of small-molecule-based IRAP inhibitors. After resynthesis, all three compounds confirmed low μM activity and were shown to be rapidly reversible. Additional characterization included activity in a fluorescence-based orthogonal assay and in the presence of a nonionic detergent and a reducing agent, respectively. Importantly, the characterized compounds also showed inhibition of the human ortholog, prompting our further interest in these novel IRAP inhibitors.