Gene Therapy Restores Vision in Leber Congenital Amaurosis

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Five children and seven adults with Leber congenital amaurosis, a rare, progressive retinal disease that causes blindness, have had their sight partially restored after receiving a single injection of gene therapy. Among the patients treated with the gene therapy, who ranged in age from 8 to 44 years at the time of treatment, the children experienced the most improvement in vision.

Leber congenital amaurosis is an inherited retinal degenerative disease in which individuals experience a severe loss of vision at birth. Signs and symptoms such as deep-set eyes, roving eye movements (nystagmus), and hypersensitivity to bright light also occur. Initially, Leber congenital amaurosis can be confused with early onset retinitis pigmentosa, cortical blindness, congenital and hereditary optic atrophy, and flecked retina syndrome. Diagnostic tests including electroretinography, which measures retinal function, along with accurate documentation of family history can distinguish between these related vision problems. People with Leber congenital amaurosis display little if any activity in the retina.

The current study, which was conducted by researchers from the University of Pennsylvania School of Medicine and the Center for Cellular and Molecular Therapeutics at The Children’s Hospital of Philadelphia, is a great leap forward for the field of gene therapy. While this study of gene therapy for Leber congenital amaurosis provides a treatment option for individuals who had none before, the authors of the study also note that their results may open the door for treatment of more common retinal diseases, including age-related macular degeneration.

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Half of the twelve patients achieved an improvement in vision so they are no longer classified as legally blind. Among the children who were treated with gene therapy, they “are now able to walk and play just like any normally sighted child,” said Albert M. Maguire, MD, an associate professor of ophthalmology at University of Pennsylvania School of Medicine and a physician at Children’s Hospital, in a release issued by the hospital.

In the study, patients received a single injection of genes designed to produce proteins to make the light receptors work in their retinas. Each patient received the injection in the eye that had the poorer function. In an earlier part of the study, results concerning the first three young adults to receive gene therapy for the disease were published. Following this success, five children received gene therapy, along with four other adults. None of the patients experienced any serious adverse effects from the gene therapy.

Two weeks after receiving gene therapy, all the patients reported an improvement in vision in dimly lit environments. All the patients were able to detect significantly more light and had greater light sensitivity in the treated eye compared with the untreated one. Of the nine patients that had nystagmus before treatment, seven reported significant improvement after receiving gene therapy.

Scientists plan follow-up studies to determine whether gene therapy can stop progression of Leber congenital amaurosis. Additional studies may investigate whether gene therapy can benefit people who have other retinal diseases.

SOURCES:
Children’s Hospital of Philadelphia news release October 24, 2009
Foundation Fighting Blindness

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