Epilepsy Gene Therapy Using an Engineered Potassium Channel

Abstract

Refractory focal epilepsy is a devastating disease for which there is frequently no effective treatment. Gene therapy represents a promising alternative, but treating epilepsy in this way involves irreversible changes to brain tissue, so vector design must be carefully optimized to guarantee safety without compromising efficacy. We set out to develop an epilepsy gene therapy vector optimized for clinical translation. The gene encoding the voltage-gated potassium channel Kv1.1, KCNA1 , was codon optimized for human expression and mutated to accelerate the recovery of the channels from inactivation. For improved safety, this engineered potassium channel (EKC) gene was packaged into a nonintegrating lentiviral vector under the control of a cell type-specific CAMK2A promoter. In a blinded, randomized, placebo-controlled preclinical trial, the EKC lentivector robustly reduced seizure frequency in a male rat model of focal neocortical epilepsy characterized by discrete spontaneous seizures. When packaged into an adeno-associated viral vector (AAV2/9), the EKC gene was also effective at suppressing seizures in a male rat model of temporal lobe epilepsy. This demonstration of efficacy in a clinically relevant setting, combined with the improved safety conferred by cell type-specific expression and integration-deficient delivery, identify EKC gene therapy as being ready for clinical translation in the treatment of refractory focal epilepsy. SIGNIFICANCE STATEMENT Pharmacoresistant epilepsy affects up to 0.3% of the population. Although epilepsy surgery can be effective, it is limited by risks to normal brain function. We have developed a gene therapy that builds on a mechanistic understanding of altered neuronal and circuit excitability in cortical epilepsy. The potassium channel gene KCNA1 was mutated to bypass post-transcriptional editing and was packaged in a nonintegrating lentivector to reduce the risk of insertional mutagenesis. A randomized, blinded preclinical study demonstrated therapeutic effectiveness in a rodent model of focal neocortical epilepsy. Adeno-associated viral delivery of the channel to both hippocampi was also effective in a model of temporal lobe epilepsy. These results support clinical translation to address a major unmet need.

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

“…As a proof of principle, we chose the Kcna1 gene encoding the Kv1.1 channel, which is important for the regulation of neuronal action potential firing and synaptic transmission (Pinatel et al, 2017;Vivekananda et al, 2017). Lentivirus-or adeno-associated virus-mediated overexpression of Kcna1 reduces neuronal excitability and, when targeted to principal cells, suppresses seizures in rodent models of epilepsy (Wykes et al, 2012;Snowball et al, 2019). We first conducted a bioinformatic analysis to identify its promoter region.…”

Effect of transient receptor potential vanilloid 4 activation on the delayed rectifier potassium current in the hippocampal pyramidal neurons and Kv subunit expression in the hippocampi of mice

“…Mice lacking the Kv1.1 α subunit encoded by the KCNA1 gene develop recurrent behavioural seizures early in life [19]. Epilepsy gene therapy targeting KCNA1 suppresses seizures in TLE rat models [38]. Inhibition of Kv1.1 channels inactivation reduces neuronal excitability and epileptiform activity [39].…”

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

“…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).…”