Abstracts

Rationale:
Dravet syndrome is a debilitating and catastrophic childhood epilepsy. Despite the promise of Epidiolex, most individuals with Dravet continue to be pharmaco-refractory, demonstrating that new treatments are needed. Given that the first-line treatment for Dravet is a combination of two (valproic acid (VPA) + clobazam) or three (VPA + clobazam + stiripentol) antiseizure drugs, we used our metabolism-based drug screening platform to assay for other unexplored combinations that might be efficacious in this patient population. Here we comprehensively catalogued the efficacies of 250 possible ASD combinations in a zebrafish model of Dravet syndrome.
Method:
We used CRIPSR/cas9 to introduce mutations into the zebrafish ortholog of human SCN1A (e.g., scn1lab) to create a Dravet model. Extensive metabolic profiles of scn1lab mutant zebrafish were characterized using the XF24e Seahorse Bioanalyzer. We then conducted a shelf screen of 30 known ASDs as both a monotherapy and in over 250 dual therapy combinations to test their ability to restore altered metabolic functions as a proxy of disease burden. Drug combinations that restored mitochondrially-mediated bioenergetics to baseline (e.g., wild type) levels are being validated in Scn1a+/- Dravet mice using a hyperthermia-induced seizure assay.  
Results:
The scn1lab zebrafish exhibited distinct electrophysiological and metabolic phenotypes, including dysfunctions in basal respiration, mitochondrially-mediated respiration, and ATP-linked respiration. First line monotherapy drugs VPA, clobazam, and stiripentol restored altered metabolic functions in about half the mutants, whereas VPA + clobazam was effective when administered in combination. Also, combinations of clobazam or stiripentol + ketones, stiripentol + topiramate, ketone + topiramate (often used as second line add on) were efficacious in our model. Surprisingly, zonisamide, a third line add on drug was efficacious when combined with a number of first, second, or third line therapy drugs, including VPA, clobazam, stiripentol, topiramate, 3-OH butyrate, ethoxusimide, levetiracetam, lacosamide, retigabine and piracetam. Finally, acetazolamide when combined with either clobazam, 3-OH butyrate, topiramate or ethoxusimide were remarkably efficacious, an effect that was absent when combined with rufinamide, pregabalin or levetiracetam.
Conclusion:
Alternative combinations of ASD therapies might be efficacious for monogenic intractable epilepsies.
Funding:
:None