Discovery of Diphenyl Ether Derivatives as Novel BK Ca Channel Activators: Structure-Activity Relationship, Cryo-EM Complex Structures, and In Vivo Animal Studies.

The BK _Ca channel, a large-conductance calcium-activated potassium channel, plays a crucial role in maintaining the homeostasis of the micturition cycle and airway-related functions. In this study, we optimized a novel BK _Ca channel activator, 4d , with a diphenyl ether structure identified from library screening. This led to the discovery of potent activators, 10b (EC ₅₀ = 0.12 μM, cell-based assay) and 51b , an orally bioavailable derivative. Compound 10b demonstrated potent in vivo efficacy in a spontaneous hypertensive rat (SHR) of urinary incontinence model, while compound 51b showed dose-dependent cough suppression efficacy with an ED ₅₀ of 11.8 mg/kg in a citric acid-induced cough model. Furthermore, we reported the cryo-electron microscopy (cryo-EM) structures of the BK _Ca channel in complex with 10b and 51b at resolutions of 2.8 and 3.4 Å. Based on structural analyses, we determined the binding sites and key interaction residues of 51b , which were validated via mutation studies.