The latest gene therapy treatments that are working through clinical trials are targeting problems that are localized in the body. Eventually there will be gene therapy success on non-localized problems. There is work to improve delivery of gene therapy without using viruses to avoid triggering immune response. There is also work on making genetic engineering changes on many genes at the same time instead of just one. The limitations of current early work may not limit more advanced methods.
Genzyme has three programs—peripheral artery disease, Parkinson’s disease, macular degeneration—that share some features in common. They can be treated with localized therapy, which doesn’t need to circulate throughout the body, they are serious illnesses that don’t require treatments with absolutely squeaky-clean safety profiles, and they appear suitable to a single-shot gene therapy approach. Eliminating the need for multiple injections is especially useful in the case of gene therapy for Parkinson’s, in which doctors drill a hole in the skull to deliver genes to a precise region of the brain, or for macular degeneration, in which doctors make an injection behind the eye.
Local delivery is the key, Wadsworth says. Doing it that way makes it much less likely that the body’s immune system will mount a reaction to the viruses used to deliver the genes, he says.
Genzyme (NASDAQ: GENZ), with headquarters in Cambridge, MA and a gene therapy manufacturing unit in San Diego, is planning to present results this month at the American College of Cardiology from a clinical trial of 289 patients who took its experimental gene therapy for peripheral artery disease. This treatment is designed to encourage re-growth of new blood vessels to circumvent clogged arteries in the legs. If successful, this trial will show whether a single shot can help patients with severely limited mobility keep walking for longer periods without pausing to rest.
OTHER MEDICAL RESEARCH
Others are working on using gene therapy to treat deafness.
Deafness affects more than 250 million people worldwide. It typically involves the loss of sensory receptors, called hair cells, for their “tufts” of hair-like protrusions, and their associated neurons. A new study led by Dr. Marcelo N. Rivolta of the University of Sheffield has successfully isolated human auditory stem cells from fetal cochleae (the auditory portion of the inner ear) and found they had the capacity to differentiate into sensory hair cells and neurons.