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Abstracts

A PV-Interneuron Selective AAV9 Vector Restores SCN1A Expression and Rescues Phenotypes in a Mouse Model of Dravet Syndrome

Abstract number : 1.201
Submission category : 2. Translational Research / 2D. Models
Year : 2025
Submission ID : 1221
Source : www.aesnet.org
Presentation date : 12/6/2025 12:00:00 AM
Published date :

Authors :
Presenting Author: Kathryn Allaway, PhD – Regel Therapeutics

Perry Spratt, PhD – Regel Therapeutics
Andrew Field, PhD – Regel Therapeutics
Nicholas Trojanowski, PhD – Regel Therapeutics
Joshua Reiser, MS – Regel Therapeutics
Rajani George, PhD – Regel Therapeutics
Lucia Capano, PhD – Regel Therapeutics
Tessa Winialski, MS – Regel Therapeutics
Tasneem Rinvee, BS – Regel Therapeutics
Mia Brakebill, BS – Regel Therapeutics
Jeanne Duong, MS – Regel Therapeutics
Navneet Matharu, PhD – Regel Therapeutics
Jordane Dimidschstein, PhD – Regel Therapeutics

Rationale: Dravet syndrome is a rare and devastating form of epilepsy that typically begins in the first year of life, characterized by prolonged seizures that are often resistant to anti-seizure medications. Over 80% of Dravet syndrome cases are caused by loss-of-function mutations in one copy of the gene SCN1A, leading to a reduction in expression of the voltage-gated sodium channel Nav1.1. Nav1.1 is predominantly expressed in the axon initial segments of parvalbumin (PV)-expressing interneurons of the cerebral cortex and hippocampus, where it plays a key role in action potential initiation and propagation. PV interneurons, despite representing only ~4% of all cells in the cortex, play a central role in controlling the overall balance of excitatory and inhibitory signaling in the brain. Strategies that restore SCN1A expression specifically in PV interneurons present a promising therapeutic approach to treat the root cause of seizures and neurological symptoms in Dravet syndrome.

Methods: RT101 is an AAV9 vector designed to restore normal expression levels of Nav1.1 selectively in PV interneurons through the use of an SCN1A-targeted dCas9-VP64 module. Although AAV9 broadly transduces neurons, PV-selective expression of the therapeutic transgene is achieved using the E2 promoter, which has been well characterized for its specificity across species. The ability of RT101 to specifically upregulate SCN1A was evaluated in vitro using a luciferase reporter assay and tissue-relevant cell lines. RT101 was then tested in the Scn1a-tm1Kea mouse model of Dravet syndrome using intracerebroventricular (ICV) administration of RT101. Several phenotypic outcomes were evaluated, including survival and susceptibility to hyperthermia-induced seizures.

Results: The ability of RT101 to engage with the SCN1A locus was demonstrated using a luciferase assay and confirmed at the endogenous locus in vitro, where significant SCN1A transcript upregulation was observed. In silico analysis of predicted off-target sites revealed low off-target binding potential, which was further validated by RNA-sequencing analysis of cells treated with the RT101 dCas9-gRNA payload. In the Dravet mouse model, RT101 administration resulted in dose-dependent and statistically significant improvements in survival. Mice also exhibited significantly reduced susceptibility to hyperthermia-induced seizures and increased Nav1.1 protein expression. Together, these data demonstrate that RT101 selectively restores SCN1A expression with no evidence of off-target activity, leading to strong and clinically relevant  phenotypic rescue in a preclinical model of Dravet syndrome.

Conclusions: RT101, an AAV9 vector which expresses dCas9-VP64 selectively within PV interneurons, significantly upregulates SCN1A and significantly improves survival with a reversal of hyperthermia-induced seizure phenotypes in a mouse model of Dravet syndrome. These results provide strong proof-of-concept data supporting the use of PV interneuron-selective gene modulation therapy in Dravet syndrome. 

Funding:

Regel Therapeutics, Inc.



Translational Research