Arylamino Esters as P-Glycoprotein Modulators: SAR Studies to Establish Requirements for Potency and Selectivity

A set of basic aryl-group-containing compounds was synthesized with the aim of developing potent and selective P-glycoprotein (P-gp) modulators that are able to reverse multidrug resistance (MDR). The natures of the spacer (dicyclohexylamine or dialkylamine) and the aryl moieties were modified to investigate selectivity and the mechanism of P-gp interaction. The inhibitory activities of the compounds toward P-gp, multidrug resistance-associated protein 1 (MRP1), and breast cancer resistance protein (BCRP), the most relevant ATP binding cassette (ABC) transporters for MDR, were evaluated. The mechanism of P-gp interaction for each compound was investigated with three biological assays: apparent permeability (Papp) determination (BA/AB) in Caco-2 cell monolayers, ATP cell depletion, and inhibition of Calcein-AM transport in MDCK-MDR1 cells. These assays allowed us to estimate the selectivity of the compounds for the three efflux pumps and to identify the structural requirements that define the P-gp-interaction profile. All dicyclohexylamine derivatives were found to be P-gp substrates, whereas one dialkylamine derivative was shown to be a P-gp inhibitor. The good MRP1 activity of one cis/cis isomer highlighted this as a lead candidate for the development of MRP1 ligands.