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

Purpose: Malignant Migrating Partial Seizures of Infancy (MMPSI) is a severe form of pharmacoresistant epilepsy. Slack channels are sodium-activated potassium channels, which are critical regulators of electrical activity in the CNS. MMPSI has been linked to gain-of-function mutations of Slack channels. Our objective is to develop small molecule selective Slack inhibitors through an iterative hit optimization library synthesis approach to identify lead compounds 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 developed around hit compound VU0606170 revealed that a 2,5-di-substitution pattern on the eastern phenyl ring was optimal for Slack activity. Compounds were identified that are selective for the A934T Slack variant versus WT. Modifications to the linker portion led to a loss of Slack activity. 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 eastern portion of VU0606170. These findings are presently being combined with SAR obtained from other regions of the molecule in search of compounds with improved potency and a more favorable DMPK profile.