Biochemical autoregulatory gene therapy for focal epilepsy

Abstract

Despite the introduction of more than one dozen new antiepileptic drugs in the past 20 years, approximately one-third of people who develop epilepsy continue to have seizures on mono- or polytherapy. Viral-vector-mediated gene transfer offers the opportunity to design a rational treatment that builds on mechanistic understanding of seizure generation and that can be targeted to specific neuronal populations in epileptogenic foci. Several such strategies have shown encouraging results in different animal models, although clinical translation is limited by possible effects on circuits underlying cognitive, mnemonic, sensory or motor function. Here, we describe an autoregulatory antiepileptic gene therapy, which relies on neuronal inhibition in response to elevations in extracellular glutamate. It is effective in a rodent model of focal epilepsy and is well tolerated, thus lowering the barrier to clinical translation.

In vivo CRISPRa decreases seizures and rescues cognitive deficits in a rodent model of epilepsy

“…We complemented the chronic epilepsy study by looking at the effect of Kcna1-dCas9A treatment on acute seizures evoked by a different mechanism, focal pilocarpine injection in the visual cortex before and after doxycycline administration (Lieb et al, 2018;Magloire et al, 2019). We did not observe robust differences in EEG coastline and power in different frequency bands recorded for 1 hour after pilocarpine in either group, although there was a non-significant trend for Kcna1-dCas9 animals to show an attenuation in seizure severity ( Supplementary Figure 8).…”

“…Although the majority of drug-resistant epilepsies are focal, targeting drugs to a restricted brain region presents major challenges, and potentially curative surgery is limited to a minority of cases where the seizure focus is remote from eloquent cortex . Gene therapy holds promise as a rational replacement for surgery for intractable pharmaco-resistant epilepsy, and could in principle improve the prospect for seizure freedom in many people Lieb et al, 2018). Several approaches have been proposed to interfere with epileptogenesis or to decrease seizure frequency in chronic epilepsy (Simonato, 2014).…”

“…Several approaches have been proposed to interfere with epileptogenesis or to decrease seizure frequency in chronic epilepsy (Simonato, 2014). Current experimental gene therapies mainly rely on viral vector-mediated expression of genes encoding normal CNS proteins or exogenous non-mammalian proteins (Wykes et al, 2012;Krook-Magnuson et al, 2013;Katzel et al, 2014;Wykes et al, 2016;Lieb et al, 2018). This approach has several potential limitations, including a finite packaging capacity of viral vectors, difficulty in ensuring normal splicing and post-transcriptional processing, and, in the case of non-mammalian proteins, concerns about immunogenicity.…”

Olanzapine: a full and potent agonist at the hM4D(Gi) DREADD amenable to clinical translation of chemogenetics

“…To test whether OZP is effective in vivo we redesigned a codon-optimized version of hM4D(Gi) linked via a viral self-cleaving 2A-peptide to GFP (hM4D(Gi)opt), and put it under control of a human CamKIIα promoter for selective expression in excitatory neurons (26). We verified that the EC50 of OZP at hM4D(Gi)opt was similar to that at the original hM4D(Gi):…”

Dynorphin‐based “release on demand” gene therapy for drug‐resistant temporal lobe epilepsy

“…Numbers and duration of seizures were reduced, but long-term suppression of seizures in a therapeutic setting is still outstanding (Noe et al, 2010) (Ledri et al, 2016). A glutamate-sensitive chloride channel was tested only in acute seizures (Lieb et al, 2018). Recently, a mutated voltage-gated potassium channel Kv1.1 proofed beneficial in the model of systemic KA injection (Snowball et al, 2019).…”