Mucopolysaccharidosis type II (MPSII, Hunter Syndrome) is a rare paediatric X-linked lysosomal storage disease caused by a deficiency in iduronate-2-sulphatase (IDS), due to a mutation on the IDS gene. IDS is essential for the breakdown of glycosaminoglycans (GAGs), in particular, heparan sulphate (HS) and dermatan sulphate (DS). Currently, enzyme replacement therapy (ERT) is the only clinically approved treatment available for MPSII. However, ERT is a supportive therapy and is intended to alleviate symptoms and improve patient quality of life, rather than addressing the pathogenic mechanisms of the disease. To date, there is no effective disease-modifying treatment.~This study aims to recruit 5 patients with MPS II who satisfy the inclusion and exclusion criteria and provide full consent, between 3 months and 12 months of age at screening. The investigational medicinal product (IMP) will be a cell-based gene therapy that uses genetically modified autologous CD34+ haematopoietic stem cells transduced with a lentiviral vector containing the human IDS gene tagged with ApoEII. Patients will be followed up for a minimum of 2 years after gene therapy.
Patients with MPS II have a clinical disorder marked by progressive brain disease, neurological and somatic symptoms due to the accumulation of undigested glycosaminoglycans in all cells of the body.~This study will be the first in human clinical trial to explore the safety, tolerability and clinical efficacy of ex vivo gene therapy (autologous CD34+ cells transduced with a lentiviral vector containing the human IDS gene) in MPSII patients. Following treatment with the gene therapy patients will be followed up for a minimum of 2 years.