About Gene Therapy
Gene therapy is a treatment approach that attempts to treat a genetic problem at its source. When a mutated gene occurs in your body, it can affect how your cells create proteins and how those proteins behave, leading to disease. Gene therapy attempts to add a working copy of a defective gene to the patient’s cells, helping the cells function normally. This is different from a traditional drug-based approach, which may treat symptoms but not the actual genetic problems.
Since genes can’t be delivered into cells on their own, they need to have a helper, called a vector. Viruses are often used as vectors because they can easily penetrate the cell. Once inside, the information in the gene is used by the cell to build RNA and proteins. The proteins (or RNA) can then carry out their job in the cells. SB-318, the investigational drug in this study, is a type of gene therapy known as genome editing.
For MPS I, the goal is to deliver a normal gene into liver cells so they can produce the right amount of the IDUA enzyme that processes large molecules that build up and cause MPS I. SB-318 (the investigational therapy) consists of three vectors, each carrying a different gene. Two of these vectors carry genes for proteins that work like scissors to cut a piece of DNA in your liver cells. The third vector, carrying the IDUA gene, can then be inserted into the DNA in your liver cells. This process is known as gene editing.
The vectors to be used in this study are adeno-associated viruses (AAV) that have been changed so they can carry genes that are potentially therapeutic. These viruses infect humans but don’t cause any known disease. These viruses have been changed in the laboratory so they can no longer grow or reproduce in the human body.
These vectors can go to the liver, where the gene for normal IDUA will be introduced following a single infusion of SB-318 into a vein in your arm. In this way, the liver cells will produce IDUA and release it into your blood. Because the gene is added into your DNA, it may enable production of IDUA for a long time. This is something that will be evaluated in this study.