Discovery of Small Molecule Slack Inhibitors for the Treatment of MMPSI: SAR Development in the Western and Central Region of Hit Compound VU0606170

Introduction: Malignant Migrating Partial Seizures of Infancy (MMPSI) is a severe and pharmacoresistant form of epilepsy. Slack channels are sodium-activated potassium channels regulating essential electrical activity in CNS. Gain-of-function mutations in Slack channels have been linked to MMPSI. Objective: To develop small molecule selective Slack inhibitors employing a library synthesis based iterative hit optimization approach to discover leads for development into MMPSI therapeutics. Methods: Classical and state-of-the-art synthetic chemistry techniques including microwave assisted organic synthesis and flow chemistry were employed. Purification was by automated liquid chromatography. Bruker Fourier 300HD and Agilent 6230 time-of-flight LC/MS were utilized to obtain NMR and HRMS, respectively. Inhibitory activity of Slack was measured utilizing a Thallium flux assay in HEK293 cells stably expressing either WT or Slack mutants. Results: SAR studies around hit compound VU0606170 identified a chiral-methyl analog in the piperizine core as optimal for potency. Other new core analogs were less potent than their piperazine counterparts. Several western urea and amide analogs were prepared, and a few moderately potent compounds were identified. Replacement of sulfamide linkers with a sulfonamide gave encouraging results. Lastly, in-vitro DMPK studies with selected compounds revealed high clearance, high protein binding, and good permeability. Conclusion: SAR was identified for Slack activity, mutant selectivity, and DMPK properties around the western and central region of VU0606170. At present, synthesis of analogs that combine optimal functional groups from the entire chemotype are underway with a goal of improving potency and DMPK properties.