Foundation News » Macular Degeneration
What’s Next for Gene Therapy: Your Questions Answered
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Over the past two years, more than 20 people who were nearly blind from a severe form of retinitis pigmentosa known as Leber congenital amaurosis (LCA) have had significant vision restored thanks to three landmark Phase I clinical trials of gene therapy. This breakthrough has received media attention and scientific accolades from around the world. Following our report of the latest findings from the trial at The Children’s Hospital of Philadelphia in October 2009, we have received a number of excellent questions from you, our members, about gene therapy and the potential that it holds for treating the entire spectrum of retinal diseases. Stephen Rose, Ph.D., chief research officer of the Foundation Fighting Blindness, answers some of your most common questions. What happens next in the three LCA gene therapy trials? Investigators at The Children’s Hospital of Philadelphia are working to move their gene therapy into a Phase II clinical study, which would involve younger participants — even younger than the nine-year-old boy (he was eight when treated) who had dramatic vision improvement. While the other institutions conducting LCA gene therapy clinical trials — the Universities of Pennsylvania and Florida and Moorfields Eye Hospital (London) — have not announced their next steps, I presume that they, too, are working toward Phase II studies. But that is purely speculation on my part at this point. A company called Applied Genetic Technologies Corporation (AGTC) is also launching a Phase I/II clinical study of gene therapy for LCA to be conducted at the Foundation-supported Oregon Health and Science University and the University of Massachusetts. Why are there three studies of the same treatment for the same form of LCA? All three studies (four studies if you include AGTC) involve correction of LCA caused by variations in a gene known as RPE65. While all the studies are evaluating similar treatments, each treatment is, in fact, different. The actual composition and strengths are different. Also, investigators are treating different areas of the retina. So, each clinical trial is contributing its own, unique information toward identifying the best approach to using gene therapy to treat this form of LCA. Getting this treatment right is critical to the advancement of gene therapy for treating all retinal diseases. Why did researchers choose to treat LCA first? LCA caused by RPE65 variations is easier to treat than most other retinal diseases, because the retina doesn’t degenerate that much when affected people are young. That’s why the younger patients have had significant vision improvement. You can look at this particular disease like a car with a good engine but the wrong fuel. The treatment corrects the fuel problem and then the car runs well. However, if the car sits in the garage for several years, the engine may lock up and need additional repair (i.e., the retina degenerates). So, you want to correct the fuel problem early for the best results, and if you do that, the results can be dramatic. When will researchers begin developing gene therapy for other retinal degenerative diseases? Success in the three LCA studies has opened the door for the development of gene therapies to treat a broad spectrum of retinal diseases, and the Foundation is funding a majority of them. Here is a quick summary of some of the gene therapy projects currently underway:
When will gene therapy be available for my disease? As reflected in the answer to the previous question, gene therapy has come a long way in the last two years thanks to the success of the LCA clinical trials. However, it still has a long way to go. The Foundation is working as hard as it can to raise revenue to fund the development of gene therapies for every retinal degenerative disease. We are getting there, but it takes a lot of money and time. Keep in mind that gene therapy may not be the best treatment option for every disease or every individual. In some cases, a drug or cell-based treatment may be a better option. Depending on a person’s age and the extent of their disease, protecting and preserving the retina may be a better approach. This is why the Foundation funds such a wide variety of treatment approaches. Different treatments will work better for different people. What can I do now? Stay in touch with your retinal specialist to make sure he or she is addressing any complications, and helping you to make the most of your vision. Your doctor may prescribe a nutritional regimen or sunglasses. Your doctor can also keep you abreast of the latest research or about upcoming clinical trials. Read Why it is Important to Stay in Touch with Your Retinal Specialist for more information. You might also consider genetic testing to gain a better understanding of your disease and position yourself for future clinical studies. I strongly encourage you to read Is a Genetic Test Right for You? to learn more about the genetic testing process and its pros and cons. And, of course, keep supporting the Foundation. Your contributions are what drive the research and move us closer to treatments and cures. We can only fund a fraction of the high-quality research projects available to us, so every dollar helps tremendously. How Does Gene Therapy Work? Virtually every cell in your body carries a complete set of an estimated 20,000 to 25,000 genes. Genes instruct cells which proteins to make, and these proteins are essential to the health and functioning of all your cells. Most inherited retinal degenerative diseases are caused by a small variation (mutation) in a single gene. These variations are like small misspellings in an instruction manual. Even a small misspelling can cause the wrong protein or wrong amount of protein to be made. That can lead to serious consequences like degeneration of the retinal cells that enable you to see. Scientists are developing gene therapies to deliver a new, corrective gene to the retina, so cells make the right proteins, and stay healthy and functioning properly. Man-made therapeutic viruses are one way to deliver the corrective gene to the cells. The viruses are said to “transfect” — or penetrate — the cells with their healthy genetic cargo. Gene therapy is administered by injecting a tiny drop of solution — which contains the virus and new gene — underneath the retina. The solution is absorbed into the retina over a period of hours. The elegance of gene therapy is that one treatment can potentially be effective for several years or perhaps a lifetime. |
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