Why is gene therapy given as only one dose?

Most medicines have to be taken again and again because the body breaks them down. Gene therapy works differently. Instead of delivering a drug, it delivers instructions: a working gene that the patient's own cells can use to make the missing protein.

With AAV vectors, the delivered gene generally stays in the nucleus of the cell without becoming part of the chromosomes. In cells that don't divide, such as nerve cells, it can keep working for a long time. That's why AAV therapies are designed as a single treatment.

There's also a practical reason. After someone receives an AAV vector, their immune system usually makes antibodies against it, which can make a second dose of the same vector difficult or ineffective. So researchers work hard to get the dose right the first time.

For Drake and Vivian, one dose would mean one carefully planned treatment rather than a lifetime of daily glycine-lowering medications, though no one yet knows how they will respond. That single dose depends on fully funding manufacturing and the trial. Give to help them get there.

Sources: U.S. FDA: What is Gene Therapy? · MedlinePlus Genetics: What is gene therapy?