Structure-Based Identification and Characterization of Inhibitors of the Epilepsy-Associated K1.1 (KCNT1) Potassium Channel.

Drug-resistant epileptic encephalopathies of infancy have been associated with KCNT1 gain-of-function mutations, which increase the activity of K1.1 sodium-activated potassium channels. Pharmacological inhibition of hyperactive K1.1 channels by quinidine has been proposed as a stratified treatment, but mostly this has not been successful, being linked to the low potency and lack of specificity of the drug. Here we describe the use of a previously determined cryo-electron microscopy-derived K1.1 structure and mutational analysis to identify how quinidine binds to the channel pore and, using computational methods, screened for compounds predicated to bind to this site. We describe six compounds that inhibited K1.1 channels with low- and sub-micromolar potencies, likely also through binding in the intracellular pore vestibule. In hERG inhibition and cytotoxicity assays, two compounds were ineffective. These may provide starting points for the development of new pharmacophores and could become tool compounds to study this channel further.