that 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.
“It’s like in real estate, where you’ve heard it’s about location, location, location,” Wadsworth says. “This is about delivery, delivery, delivery. If you can place the vector (for delivering genes) right where you want it, you’re better off.”
Part of this philosophy is built on some the hard knocks from past experiments with gene therapy, which have shown it is difficult to get tiny modified viruses to deliver genes everywhere they need to go in the body. More successes have been reported with local delivery, including a couple of people who had “amazing” results with a rare genetic form of blindness,Wadsworth says.
Wadsworth sees reason for encouragement based on these cases of Leber’s Congenital Amaurosis, that were published in 2007 in the New England Journal of Medicine. He didn’t have any more data like that to share with me about bringing back people’s eyesight, but he said Genzyme does have some data it is looking forward to presenting soon.
This trial examines whether Genzyme can deliver new copies of a gene for HIF-1 alpha, a protein associated with growth of new blood vessels. The idea is that people with peripheral artery disease have clogged arteries, and one to help them improve circulation in the legs is to form new vessels that circumvent the blockages, Wadsworth says. If that trial turns out positive, Genzyme will be prepared to advance that program into the final stage of clinical trials—where a competing gene therapy from Sanofi-Aventis has already ventured.
If scientists can report a couple of successes in trials this large, Wadsworth says he still thinks gene therapy could repeat the history of antibody drugs. There was an initial wave of hype in the early days of the 1970s, followed by failures, and then the first successful products arrived more than 20 years after the seminal discoveries.
“With monoclonal antibodies, it was hyped and then it took a long time to work out the kinks,” Wadsworth says. “The analogy of gene therapy to monoclonal antibodies is not a bad one.”
