Study With Batten-1 (Miglustat Liquid Formulation) to Treat Ceroid Lipofuscinosis Neuronal 3 (CLN3) Disease

The goal of this open-label, single-arm, multicenter study is to assess the efficacy and safety of Batten-1 (oral liquid formulation of miglustat) (15 mg/kg up to 600 mg/day) in approximately 27 pediatric subjects with CLN3 disease over a period of 52 weeks, using visual acuity as primary efficacy endpoint, The main questions it aims to answer are: * Does Batten-1 slow down or stabilize the visual acuity decline in pediatric CLN3 patients ? * What medical problems do participants have when taking Batten-1? in comparison with an external group of non-treated CLN3 disease subjects from natural history studies. After a titration period of 8 weeks, participants will take Batten-1 every day up to 52 weeks and will visit the clinic every 24 weeks for checkups and tests. Participants will keep a diary for potential seizure occurrence and compliance to study drug. Interventions they'll be given include: * visual acuity assessement * motor and capability assessement * safety assessment including lab tests and electrocardiogram * assessment of the effect of the body on Batten-1 * assessment of quality of life

Inclusion Criteria: * Male or female subjects ≥ 4 years and \ 1.9 for best corrected visual acuity. * Have any ocular conditions that in the opinion of the investigator might affect visual assessments (e.g. cataract, glaucoma, diabetes, amblyopia, etc…). * Have received gene therapy or stem cell therapy intended to modify the course of CLN3 disease. * Have participated in another interventional study during the last three months before screening. * Have been exposed to miglustat within 1 week prior to baseline, or is scheduled to receive an investigational device or drug (other than test product) during the study. * Have a medical condition that, in the opinion of the investigator, would interfere with the efficacy or safety assessments or increase the subject's risk of adverse events (AEs), including any active malignancy of any type except non-melanoma skin cancer. * Have a clinically significant abnormality in their clinical laboratory values (hematology, chemistry) at screening that would preclude their participation in the study. * Have a cardiac impairment including repolarization disturbances (prolonged QTc), ventricular hypertrophy and sinus node dysfunction with severe bradycardia and other conduction issues. * Have a known allergy or hypersensitivity to miglustat, or any component of the Investigational Medicinal Product (IMP) formulation. * Have a severe renal disease (estimated Glomerular Filtration Rate (eGFR) \< 30 mL/min). * Have a medical history of HIV, hepatitis B, hepatitis C, or positive results at screening.