A Safety and Efficacy of Intrathecally Administered ION283 in Patients With Lafora Disease

Inclusion Criteria: General Inclusion Criteria * Must give written informed consent (and assent if indicated by patient's age and in accordance with local requirements) and be willing/able to comply with all study requirements. * Aged 10-18 (inclusive) years old at the time of informed consent. * Non-pregnant and non-lactating females * All male participants and women of childbearing potential must refrain from sperm/egg donation from the time of signing the informed consent/assent form until at least 12 weeks (approximately 5 half-lives of ION283) after the dose of Study Drug. * For participants engaged in sexual relations of childbearing potential, highly effective contraception must be used from the time of signing the informed consent/assent form until at least 12 weeks (approximately 5 half-lives of ION283) after receiving Study Drug. Target Inclusion Criteria * Genetically confirmed diagnosis of Lafora disease before or at enrollment (documented pathogenic mutations in known causative genes (EPM2A/laforin, EPM2B/NHLRC1/malin) * Must have LDPS score ≥ 9 and LDPS motor subscore of ≥ 2 (independent ambulation- walking 10 steps independently) Exclusion Criteria * Clinically significant abnormalities in medical history (e.g., previous stroke within 6 months of Screening, major surgery within 3 months of Screening) or physical examination * Platelet count \< 80,000/mm3 or any other clinically significant laboratory abnormalities that would render a patient unsuitable fo…