Evaluation of Vormatrigine and PRAX-628 in Adult Patients with Focal Onset or Primary Generalized Tonic-Clonic Seizures: An Open-Label Extension Study

Trial ID: 2025-521640-38-00
Protocol: PRAX-628-323
Sponsor: Praxis Precision Medicines Inc.

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Diseases & Conditions

Generalised tonic-clonic seizure Partial seizures

Objectives

The primary objective of this study is to evaluate the safety and tolerability of vormatrigine in adults diagnosed with epilepsy involving focal onset seizures or primary generalized tonic-clonic seizures. Secondary exploratory objectives include:

Assessment of efficacy regarding the frequency of focal or primary generalized tonic-clonic seizures.
Characterization of the effect of the investigational product on global impressions.
Determination of pharmacokinetic exposure at selected timepoints following administration.

Participants

The study involves a total of 140 patients. The population consists of adults experiencing either focal onset seizures or primary generalized tonic-clonic seizures. Both males and females are included in the cohort. Eligible participants must have completed a previous clinical trial involving vormatrigine or have received the investigational product through an expanded access program. Additionally, subjects must have demonstrated consistent adherence to seizure diary documentation and study procedures.

Plans and Procedures

This Phase 3 open label extension trial is designed to evaluate the long-term safety and tolerability of vormatrigine in adults experiencing focal onset seizures or primary generalized tonic-clonic seizures. The study includes participants who have previously completed an eligible clinical trial or have received the investigational product through an expanded access program. The primary objective is to monitor the incidence and severity of treatment-emergent adverse events, changes in vital signs, clinical laboratory results, electrocardiogram parameters, and suicidality as assessed by the Columbia Suicide Severity Rating Scale. Secondary exploratory endpoints include changes in monthly seizure frequency, plasma concentrations, and clinician-rated global impressions. The trial is estimated to occur between August 2025 and August 2027.

Treatment

The experimental medication is vormatrigine, administered as a tablet via the oral route. The investigational product is identified as PRAX-628.

Efficacy

The assessment of efficacy in this clinical trial involves several exploratory endpoints. The percent change in monthly 28-day focal onset seizures or primary generalized tonic-clonic seizures frequency will be evaluated relative to the screening or observation period of the primary trial. Additionally, changes from baseline over time will be measured using the Patient Global Impression of Severity (PGI-S) and the Clinician Global Impression of Severity (CGI-S).

Further exploratory assessments include the monitoring of vormatrigine plasma concentrations. Changes in clinical status will also be evaluated through the Patient Global Impression of Improvement (PGI-C), Clinician Global Impression of Improvement (CGI-C), and the Clinician Global Impression of Change (CaGI-C) over time following the screening period.

Inclusion and Exclusion Criteria

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Inclusion Criteria

Participant and caregiver (if applicable), is willing to sign an informed consent document in accordance with International Council for Harmonisation (ICH) Good Clinical Practice (GCP) guidelines, indicating that they understand the purpose of the clinical trial; understands and can perform, complete, and comply with all the procedures and assessments that are required during the clinical trial, including the seizure diary and contraception, and is willing to participate in the clinical trial.
Participant who completed an eligible clinical trial (unless agreed by the sponsor medical monitor), including PRAX-628-212, PRAX-628-321 or other vormatrigine trial, or participant who has received vormatrigine outside of an eligible clinical trial (such as an expanded access program).
Participant who had adequate seizure diary and vormatrigine adherence and had been otherwise adherent to the study procedures in the opinion of the investigator unless deemed unacceptable by sponsor.

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Exclusion Criteria

Participant who withdrew or discontinued treatment from the treatment period of an eligible clinical trial unless deemed acceptable by the sponsor.
Participant who plans to enter another interventional investigational study or is on any prohibited medication listed in Table 7.
Participant who is pregnant, lactating or planning to become pregnant.
Participant who is ineligible for the extension clinical trial in the view of the investigator.