Effect of Alprazolam and Ketamine on Seizures Induced by Two Different Convulsants

New GABA-Targeting Therapies for the Treatment of Seizures and Epilepsy: II. Treatments in Clinical Development

The inhibitory neurotransmitter γ-aminobutyric acid (GABA) plays an important role in the modulation of neuronal excitability, and a disruption of GABAergic transmission contributes to the pathogenesis of some seizure disorders. Although many currently available antiseizure medications do act at least in part by potentiating GABAergic transmission, there is an opportunity for further research aimed at developing more innovative GABA-targeting therapies. The present article summarises available evidence on a number of such treatments in clinical development. These can be broadly divided into three groups. The first group consists of positive allosteric modulators of GABAA receptors and includes Staccato® alprazolam (an already marketed benzodiazepine being repurposed in epilepsy as a potential rescue inhalation treatment for prolonged and repetitive seizures), the α2/3/5 subtype-selective agents darigabat and ENX-101, and the orally active neurosteroids ETX155 and LPCN 2101. A second group comprises two drugs already marketed for non-neurological indications, which could be repurposed as treatments for seizure disorders. These include bumetanide, a diuretic agent that has undergone clinical trials in phenobarbital-resistant neonatal seizures and for which the rationale for further development in this indication is under debate, and ivermectin, an antiparasitic drug currently investigated in a randomised double-blind trial in focal epilepsy. The last group comprises a series of highly innovative therapies, namely GABAergic interneurons (NRTX-001) delivered via stereotactic cerebral implantation as a treatment for mesial temporal lobe epilepsy, an antisense oligonucleotide (STK-001) aimed at upregulating NaV1.1 currents and restoring the function of GABAergic interneurons, currently tested in a trial in patients with Dravet syndrome, and an adenoviral vector-based gene therapy (ETX-101) scheduled for investigation in Dravet syndrome. Another agent, a subcutaneously administered neuroactive peptide (NRP2945) that reportedly upregulates the expression of GABAA receptor α and β subunits is being investigated, with Lennox-Gastaut syndrome and other epilepsies as proposed indications. The diversity of the current pipeline underscores a strong interest in the GABA system as a target for new treatment development in epilepsy. To date, limited clinical data are available for these investigational treatments and further studies are required to assess their potential value in addressing unmet needs in epilepsy management.

A randomized phase 2b efficacy study in patients with seizure episodes with a predictable pattern using Staccato® alprazolam for rapid seizure termination

OBJECTIVE

Alprazolam administered via the Staccato® breath-actuated device is delivered into the deep lung for rapid systemic exposure and is a potential therapy for rapid epileptic seizure termination (REST). We conducted an inpatient study (ENGAGE-E-001 [NCT03478982]) in patients with stereotypic seizure episodes with prolonged or repetitive seizures to determine whether Staccato alprazolam rapidly terminates seizures in a small observed population after administration under direct supervision.

METHODS

Adult patients with established diagnosis of focal and/or generalized epilepsy with a documented history of seizure episodes with a predictable pattern were enrolled. They were randomized 1:1:1 to double-blind treatment of a single seizure event with one dose of Staccato alprazolam 1.0 mg or 2.0 mg, or Staccato placebo in an inpatient unit. The primary end point of the study was the proportion of responders in each treatment group achieving seizure activity cessation within 2 min after administration of study drug and no recurrence of seizure activity within 2 h.

RESULTS

A total of 273 patients were screened, and 116 randomized patients received treatment with the study drug in the double-blind part. The proportion of treated patients who were responders was 65.8% for each of Staccato alprazolam 1.0 mg (n = 38; p = .0392) and 2.0 mg (n = 38; p = .0392), compared with 42.5% for Staccato placebo (n = 40). Staccato alprazolam was well tolerated when administered as a single dose of 1.0 or 2.0 mg: cough and somnolence were the most common adverse events (AEs) (both 14.5%), followed by dysgeusia (13.2%). AEs were mostly mild or moderate in intensity; there were no treatment-related serious AEs.

SIGNIFICANCE

Both 1.0 mg and 2.0 mg doses of Staccato alprazolam demonstrated efficacy in rapidly terminating seizures in an inpatient setting and were well tolerated. The next step is a Phase 3 confirmatory study to demonstrate efficacy and safety of Staccato alprazolam for rapid cessation of seizures in an outpatient setting.

Inhaled alprazolam rapidly suppresses epileptic activity in photosensitive participants

OBJECTIVE

Treatment options for seizure clusters are limited; the need for easy-to-administer treatments remains. The Staccato system delivers drug deep into the lung via inhalation. In this phase 2a study, we investigated the ability of three different doses of Staccato alprazolam to suppress the electroencephalographic (EEG) photoparoxysmal response (PPR) compared with placebo in participants with photosensitive seizures.

METHODS

Adults (18-60 years) with a diagnosis and history of PPR on EEG with or without an epilepsy diagnosis were eligible to participate. Participants received Staccato alprazolam 0.5, 1.0, and 2.0 mg, and Staccato placebo (twice) in random order. Intermittent photic stimulation and clinical assessments were performed at one predose and seven postdose time points. The primary endpoint of the study was the change in standardized photosensitivity range (SPR) in participants receiving each dose of Staccato alprazolam.

RESULTS

Fifteen participants with a prior epilepsy diagnosis were screened; five were enrolled, randomized, and completed the study. All participants were white females with a mean (SD) age of 27.2 (6.8) years. All doses of Staccato alprazolam reduced the SPR at 2 minutes; the effect was sustained through 4 hours for the 0.5-mg dose and 6 hours for the 1.0- and 2.0-mg doses. The magnitude and duration of sedation and sleepiness were dose-related. Four participants (80%) experienced ≥1 adverse event (AE); none was severe or serious. Cough, diarrhea, dysgeusia, oral dysesthesia, sedation, and somnolence were experienced by two participants (40%) each.

SIGNIFICANCE

This proof-of-concept study demonstrated that Staccato alprazolam 0.5, 1.0, and 2.0 mg rapidly suppressed epileptiform activity in photosensitive participants with epilepsy. The AE profile of Staccato alprazolam was similar to what has been reported for alprazolam for other indications. The results support further development of Staccato alprazolam as a rescue medication for the acute treatment of seizures.

The NMDA receptor complex as a therapeutic target in epilepsy: a review

A substantial amount of research has shown that N-methyl-D-aspartate receptors (NMDARs) may play a key role in the pathophysiology of several neurological diseases, including epilepsy. Animal models of epilepsy and clinical studies demonstrate that NMDAR activity and expression can be altered in association with epilepsy and particularly in some specific seizure types. NMDAR antagonists have been shown to have antiepileptic effects in both clinical and preclinical studies. There is some evidence that conventional antiepileptic drugs may also affect NMDAR function. In this review, we describe the evidence for the involvement of NMDARs in the pathophysiology of epilepsy and provide an overview of NMDAR antagonists that have been investigated in clinical trials and animal models of epilepsy.