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What is Leber Congenital Amaurosis?
Leber Congenital Amaurosis (LCA) is a group of inherited diseases characterized by severe vision loss at birth that progresses to blindness in childhood. LCA is rare and has been estimated to occur in 1 of 81,000 newborns in the U.S. and 3 out of 100,000 newborns worldwide. LCA accounts for approximately 20% of children in schools for the blind.
What causes LCA?
To date, 16 gene defects have been found to cause LCA. These mutations account for 70% of all LCA cases. The cause for the remaining 30% remains unknown.
Two subtypes of LCA are of interest to QLT: those due to defects in retinal pigment epithelial protein 65 (RPE65) and lecithin-retinol acyltransferase (LRAT) genes, which are part of a biochemical pathway called the visual cycle. The visual cycle is responsible for supplying the rod and cone cells of the retina with a chemical called 11-cis-retinal. When these genes are defective, 11-cis-retinal is not produced at adequate levels. Without 11-cis-retinal, the rods and cones cannot sense light, and this results in vision loss. Mutations in the genes for RPE65 and LRAT occur in approximately 10% of patients with LCA.
What are the current treatments for LCA?
Current treatment of LCA is supportive and includes periodic ophthalmic evaluation for vision assessment and in those patients with residual vision, assessment of the presence of amblyopia, glaucoma or cataract. Treatments under investigation include gene therapy, neuroprotection, and retinal implants. QLT is investigating a synthetic retinoid replacement, QLT091001, as a potential treatment for LCA.
The retinas in young patients with LCA still have relatively normal appearance, even though they lack normal function. There may, therefore, be a potential for treatment intervention to stop the degeneration before much of the permanent damage takes place.
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