Scaffold identification of a new class of potent and selective BCRP inhibitors.

We recently reported the synthesis and quantitative structure-activity relationships of a new breast cancer resistance protein (BCRP) inhibitor class. In the study presented herein, we investigated the possibility to better define the scaffold of this compound class by removing or modifying the aromatic ring A with various substituents selected on the basis of their electronic and lipophilic properties. The results show that this aromatic ring is important, but not essential, for activity. Many of the selected substituents led to compounds with low activity, but in some cases activity was retained. Among these, a phenolic hydroxy group proved to impart as much potency to the molecule as a hydroxyethyl side chain, initially considered necessary for activity. This derivative is one of the most active compounds in this class, maintaining an inhibitory activity similar to that of the reference compound; it is also selective for BCRP.