Optimization of a series of 2,4-diaminopyridines as neuropeptide Y Y1 receptor antagonists with reduced hERG activity.

The synthesis and evaluation of a series of 2,4-diaminopyridine-based neuropeptide Y Y1 (NPY Y1) receptor antagonists are described. Compound 1 was previously reported by our laboratory to be a potent and selective Y1 antagonist; however, 1 was also found to have potent hERG inhibitory activity. The main focus of this communication is structure-activity relationship development aimed at eliminating the hERG activity of 1. This resulted in the identification of compound 3d as a potent and selective NPY Y1 antagonist with reduced hERG liability.