Registry and Natural History Study for Progressive Myoclonus Epilepsy Type 1 (EPM1)

Progressive myoclonus-epilepsies (PME) are severe epilepsies that insinuate into the lives of previously healthy children or young adults, irrevocably intensify, and become intractable. Progressive Myoclonic Epilepsy type 1 (EPM1), also known as Unverricht-Lundborg disease (ULD), is the prototypical and most common PME. It is caused by bi-allelic variants in the CSTB gene. The phenotypic spectrum of EPM1 is broad and reflects the amount of residual CSTB protein function in an individual. Individuals with classic EPM1 typically develop seizures between 6-16 years of age, followed by progressive non-epileptic action- and stimulus-induced myoclonus, ataxia, and cerebellar dysfunction with speech and swallowing impairment. These individuals generally have one or both CSTB variants partially functional. On the severe end of the spectrum are patients with a complete loss of the CSTB protein due to bi-allelic null variants.

The characterization of disease progression and biomarker discovery are necessary to define clinically meaningful endpoints for future interventional trials and to meet regulatory requirements for phase 1/2 and later-stage trials.

As an ultra-rare disease, patients with EPM1 are dispersed across the United States, making on-site visits for natural history studies burdensome to families. In this study, we will overcome this obstacle by adapting a remote- assessment-driven natural history study with clinical, electrophysiological, and biochemical biomarkers. The proposed study will delineate the natural history and evolution of myoclonus as a key disease feature in EPM1 and CSTB-related disease, will create a biobank for biospecimen, and will assess health-related quality of life. This approach will further clinical trial readiness for EPM1-related disease.

Specifically, the objectives of this protocol are to:

1. Determine the natural history and genotype-phenotype correlations of disease-causing variants in EPM1-related disease.

2. Facilitate an early diagnosis, enable counseling with anticipatory guidance of affected families and help define clinically meaningful endpoints for future interventional traits.

Specific aims include:

1. Perform longitudinal Unified Myoclonus Rating Scale (UMRS) assessments and clinical interviews via video-teleconference with study participants to track functional impairment and disease progression.

2. Establish a biobank for samples from participants with CSTB mutations, including EPM1 and CSTB-null disease, enabling quantitative profiling of biochemical biomarkers.

3. Conduct a health-related quality of life survey about participants with EPM1 and CSTB-null disease to understand the impact on patients and caregivers.