Gene and cell therapies used in treatment

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By Aleksandra Rachitskaya, MD, as reported to Hallie Levine

A diagnosis of hereditary retinal dystrophy (IRD) can be devastating. These rare, inherited eye diseases lead to progressive vision loss and sometimes even blindness. Here at the Cleveland Clinic, we’ve seen more patients than ever with IRDs. Our number has increased from 327 patients in 2015 to nearly 800 in 2019. The reason? We’ve gotten a lot better at both diagnosis and treatment.

In the last 2 decades we have learned that around 300 genes are associated with IRDs. Thanks to advances in genetic testing technology, we are able to diagnose gene mutations in over 70% of all cases.

That’s great news, because once we know what genetic mutation drives your disease, we can often refer you to an appropriate clinical trial that may help you improve or maintain your vision. While we can’t now thanks to gene therapy, there’s a very real chance that within the next decade or two there will be a revolutionary new treatment to save your sight.

Here’s why we’re so excited about gene therapy, what’s available now, and how to find a clinical trial near you.

Why gene therapy for IRDs shows so much promise

Gene therapy involves replacing an abnormal gene with a normal one. Although there are many ways to do this, the most common method is to use a vector – a virus without the disease-causing parts – to deliver a healthy gene into cells. This is done through surgery on the eye by a doctor. The hope is that the cells with the new, functional copy of a gene will now function properly.

As it turns out, the eye itself is an ideal candidate for gene therapy. There are mutliple reasons for this. For one thing, the retina itself is relatively easy to access compared to other parts of the body like the heart or lungs. The second is that the eye is “immune privileged.” This means its immune response is not as active as in other parts of the body. This is important because when a virus vector with a normal gene is injected into the eye, you don’t want the eye’s immune response to go into overdrive.

What treatments are currently available for IRDs?

There is only one FDA-approved gene therapy for inherited retinal disorders: Luxturna, which was approved in 2017 RPE65 Gen. This can be seen in two diseases: retinitis pigmentosa and Leber’s congenital amaurosis (LCA). The treatment returns a working copy of the RPE65 gene in the retinal cells of the eye. These cells then produce the normal protein that converts light into an electrical signal in the retina. This helps slow the progression of the disease and a patient’s vision loss.

Patients with these forms of IRD initially find that they have trouble seeing at night. They then begin to lose their peripheral or lateral vision and eventually their central vision. During the Luxturna clinical trials, researchers had patients walk through a mobility maze before and after treatment. Almost all saw significant improvements in their ability to get through the maze, even in a darker environment, which is usually more difficult. There are some amazing stories of children whose sight has been restored through this procedure.

There are many other clinical trials being conducted in medical centers across the country. Here at the Cleveland Clinic, we accept patients with a type of retinitis pigmentosa known as X-linked retinitis pigmentosa. Being an X-linked condition, it mainly affects males because they have a single copy of the X chromosome that carries the mutation. (In females, the effect of the mutation is masked by the second healthy copy of the X chromosome. However, they can still be carriers of the disease and sometimes show visual changes.) We will use gene therapy to try to treat an eye of eligible patients that prevent the disease from progressing to more severe stages.

Other gene therapy clinical trials are also ongoing for other IRDs, such as B. choroideremia and achromatopsia. It promises to stop the progression of vision loss and sometimes even improve vision.

Why gene therapy gives hope to people with IRDs

Gene therapy has the potential to revolutionize the treatment of inherited retinal diseases. Just a decade ago, patients would go to the ophthalmologist and be offered nothing but low-vision therapy. Now we can test them for specific genetic mutations that cause disease and ideally link them to a gene therapy study to replace that faulty gene.

It’s important to understand that if you have IRD and it’s very advanced, introducing a healthy normal gene won’t do much. You want to identify and treat the disease before it progresses too far. This is why the genetic test itself is so important. Once that’s done, we can search across the country to see if there’s a clinical trial. You can also keep yourself updated on active and recruiting clinical trials in the United States or even worldwide via https://clinicaltrials.gov.

I think it’s important to keep an eye on your eye health even if you don’t have a diagnosed IRD yourself but do have a family history. On the recommendation of your doctor or genetic counselor, it is important to have a genetic test done to make sure you are not a carrier and to encourage other family members to get tested too. This way an IRD can be picked up as early as possible.

Looking further down the pipeline, there’s a lot of excitement surrounding cell therapy. Here, diseased retinal cells are replaced by stem cells that can develop into healthy ones. Studies on this are still in the very early stages, and the science isn’t as robust as it is for gene therapy. But this type of treatment may show promise, not only for people with IRDs, but also for people with other common diseases of the retina, such as age-related macular degeneration.

Overall, the future has never looked brighter for people with IRDs. We can’t promise you 20/20 vision, but hopefully we can introduce you to a clinical study that could improve your vision.



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