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Gene Therapy for Blindness

Posted by Ilena Di Toro | Posted on March 13, 2018

Recently a biotech firm in Philadelphia developed the first Food & Drug Administration (FDA) approved gene therapy for blindness. The company, Spark Therapeutics, developed the therapy known as LUXTURNA™, which improves eyesight in persons with confirmed biallelic RPE65 mutation-associated retinal dystrophy, also known as Leber Congenital Amaurosis (LCA). Patients with this genetic mutation have severe visual impairment at infancy or it develops during early childhood and the person becomes totally blind at middle age.

There are over 220 genes responsible for inherited retinal diseases. There are approximately 1000 cases of LCA in the US, and while the therapy does not lead to full restoration of vision, patients report that they are better at navigating in low light.

The RPE65 gene makes the proteins that make light receptors work in the retina and in this makes vision possible. LUXTURNA™ is a therapy that works through the use of a genetically engineered virus to insert new genes into the patient’s retina. The virus is specially designed to contain the genetic material needed to treat LCA. The new genes correct defects which lead to the mutation, and within weeks a patient’s vision improves. This treatment is utilizing genetic material as medicine, which signals a shift in focus from clinical based disease classification to genetic based classification. Also, this is a one-time therapy for patients. A one-time therapy saves both time and emotional energy for the patient. Medical procedures can be draining on one’s psyche. Having to do only one procedure makes this more appealing to those with this condition.

The study to test effectiveness began in 2007 in cooperation with Children’s Hospital of Philadelphia (CHOP) and the University of Pennsylvania. There were 12 patients ranging in age from 8 to 46. Half of the patients in this study had their vision improve to the point where they were no longer legally blind. Many of the participants are now doing things like reading chalkboards, recognizing faces, and even taking driver license tests. In fact, the first three patients who received this therapy are now in their 20s and 30s and they continue to enjoy their improved vision.

The great thing about the success of this therapy is that it can lead to other gene therapies that treat and even prevent disease. In fact, Spark Therapeutics is working on gene therapies to treat other inherited diseases, such as liver directed diseases, like, Hemophilia A and Pompe Disease and neuro-degenerative diseases, like Huntington’s Disease.

This also emphasizes the importance of genetic testing, so that people with inherited disease can one day benefit from genetic therapies. “The approval of the gene therapy approach for LCA opens up the door to develop therapies that target other mutations behind hereditary blindness and retinal diseases,” said Albert M. Maguire, MD, professor of Ophthalmology at the Perelman School of Medicine at the University of Pennsylvania, an attending physician at CHOP and the principal investigator for this study. “It also serves as a stepping stone to more prevalent diseases.”

The work of these and other researchers demonstrates that genetic blindness isn’t inevitable or untreatable.


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