A comprehensive approach to identifying repurposed drugs to treat SCN8A epilepsy.

Abstract

OBJECTIVE:

Many previous studies of drug repurposing have relied on literature review followed by evaluation of a limited number of candidate compounds. Here, we demonstrate the feasibility of a more comprehensive approach using high-throughput screening to identify inhibitors of a gain-of-function mutation in the SCN8A gene associated with severe pediatric epilepsy.

METHODS:

We developed cellular models expressing wild-type or an R1872Q mutation in the Nav 1.6 sodium channel encoded by SCN8A. Voltage clamp experiments in HEK-293 cells expressing the SCN8A R1872Q mutation demonstrated a leftward shift in sodium channel activation as well as delayed inactivation; both changes are consistent with a gain-of-function mutation. We next developed a fluorescence-based, sodium flux assay and used it to assess an extensive library of approved drugs, including a panel of antiepileptic drugs, for inhibitory activity in the mutated cell line. Lead candidates were evaluated in follow-on studies to generate concentration-response curves for inhibiting sodium influx. Select compounds of clinical interest were evaluated by electrophysiology to further characterize drug effects on wild-type and mutant sodium channel functions.

RESULTS:

The screen identified 90 drugs that significantly inhibited sodium influx in the R1872Q cell line. Four drugs of potential clinical interest-amitriptyline, carvedilol, nilvadipine, and carbamazepine-were further investigated and demonstrated concentration-dependent inhibition of sodium channel currents.

SIGNIFICANCE:

A comprehensive drug repurposing screen identified potential new candidates for the treatment of epilepsy caused by the R1872Q mutation in the SCN8A gene.

• Authors: Talia A Atkin, Chani M Maher, Aaron C Gerlach, Bryant C Gay, Brett M Antonio, Sonia C Santos, Karen M Padilla, JulieAnn Rader, Douglas S Krafte, Matthew A Fox, Gregory R Stewart, Slavé Petrovski, Orrin Devinsky, Matthew Might, Steven Petrou, David B Goldstein
• Journal: Epilepsia (Epilepsia) Vol. 59 Issue 4 Pg. 802-813 (04 2018) ISSN: 1528-1167 [Electronic] United States
• PMID: 29574705 (Publication Type: Case Reports, Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)
• Copyright: Wiley Periodicals, Inc. © 2018 International League Against Epilepsy.

Chemical References

• Anticonvulsants
• NAV1.6 Voltage-Gated Sodium Channel
• SCN8A protein, human

Topics

• Anticonvulsants (pharmacology, therapeutic use)
• Child
• Dose-Response Relationship, Drug
• Drug Repositioning (methods)
• Epilepsy (diagnosis, drug therapy, genetics)
• Female
• HEK293 Cells
• High-Throughput Screening Assays (methods)
• Humans
• Male
• Mutation (drug effects, genetics)
• NAV1.6 Voltage-Gated Sodium Channel (genetics)