Development of improved PPARß/δ inhibitors.

GSK0660 (1) is the first peroxisome proliferator-activated receptor (PPAR) ß/δ-selective inhibitory ligand described in the literature. Based on its structure, we designed and synthesized a series of modified compounds to establish preliminary structure-activity relationships. Most beneficial for increased binding affinity towards the PPARß/δ ligand binding domain was the replacement of the 4'-aminophenyl substituent by medium-length n-alkyl chains, such as n-butyl or iso-pentyl. These compounds show activity down to the one-digit nanomolar range, thus possessing up to a tenfold higher binding affinity compared with GSK0660. Additionally, the subtype-specific inhibition of PPARß/δ was confirmed in a cell-based assay making these compounds invaluable tools for the further exploration of the functions of PPARß/δ.