Authors :
Presenting Author: Anne Danks, PhD – Longboard Pharmaceuticals, Inc.
Marco Peters, PhD – Longboard Pharmaceuticals, Inc.; Randall Kaye, MD – Longboard Pharmaceuticals, Inc.
Rationale:
5-HT
2 receptor agonists have demonstrated efficacy for a variety of seizure types and seizure disorders. LP352 is a potent, selective 5-HT
2C superagonist being developed for the treatment of developmental and epileptic encephalopathies (DEE). Proof of concept for the utility of LP352 across a range of seizure etiologies was established in zebrafish and mouse model systems. Due to rapid reproductive capacity and ease of genetic manipulation, both zebrafish and mice are highly useful model systems for studying many human diseases. Both have been validated as experimental models for seizures and epilepsy and show sensitivity to many classes of anti-seizure medications.
Methods:
For zebrafish studies, locomotor activity of individual larvae in 96-well plates was tracked with an automated tracking device. Local field potentials were recorded via non-invasive surface recordings from the skin above the optic tectum, and epileptiform activity was quantified. Exp 1: Mutations in the human SCN1A gene, which encodes for a voltage-gated sodium channel α-subunit, have been associated with the genetic epilepsy known as Dravet Syndrome. Zebrafish larvae containing mutations in the fish ortholog gene (scn1Lab-/-) were treated with LP352 or vehicle, and motor behavior and brain epileptiform activity were measured. Exp 2: Wild-type zebrafish larvae were treated with ethyl ketopentenoate (EKP), which reduces the synthesis of the inhibitory neurotransmitter GABA, to induce generalized seizures. EKP-treated larvae were exposed to LP352, and brain epileptiform activity was recorded. Exp 3: Wild-type zebrafish larvae were treated with kainic acid (KA), a cyclic analog of L-glutamate that binds to and activates excitatory glutamate receptors, to induce acute and chronic seizures in zebrafish in a model of temporal lobe epilepsy. KA-treated larvae were exposed to LP352, and brain epileptiform activity was recorded. Exp 4: Mice were given intravenous pentylenetetrazol (PTZ), an antagonist of the GABA-A receptor, to produce myoclonic and tonic-clonic seizures in a model of generalized epilepsy. LP352 was administered orally prior to PTZ administration, and time to the first myoclonic twitch or onset of generalized clonus was recorded.Results:
Exp 1: LP352 treatment reduced locomotor activity and both the frequency and the mean cumulative duration of epileptiform events (84% and 85%, respectively). Exp 2: LP352 treatment reduced brain seizure activity an average of 69.1%. Exp 3: LP352 treatment produced an 82.4% reduction in brain seizure activity. Exp 4: LP352 administration produced a dose-dependent increase in the time to the first myoclonic twitch and the time of onset to generalized clonus.
Conclusions:
LP352 broadly reduces a wide variety of seizure activities stemming from numerous underlying causes including genetic mutations in neuronal sodium channels, reduced GABAergic signaling, and excessive glutamatergic excitation. These data support the potential of LP352 to be useful in treating DEE patients with heterogeneous underlying pathologies.
Funding:
This study was sponsored by Longboard Pharmaceuticals, Inc.