Inclusion Criteria:  Genetically confirmed GM1 Gangliosidosis or genetically confirmed Tay-Sachs or Sandhoff disease Onset of neurological symptoms on or after the patient's first birthday Achieved 12-month developmental milestones at normal developmental time points as per Principal Investigator's judgement Abnormal gait and/or speech disturbance  Exclusion Criteria:  Patients who have received (within 6 months before screening), are currently receiving or are planned to receive (within the following 6 months) gene therapy, stem cell transplantation, experimental drugs, or any drug, which, in the Investigator´s opinion, may (have) interfere(d) with disease progression