Treating hereditary blindness



More than 16 million people worldwide, including 60,000 Canadians and 18,000 Quebecers, suffer from hereditary blindness caused by the premature death of photoreceptor cells.

The two most common forms of hereditary blindness are retinitis pigmentosa (RP) and Leber's congenital amaurosis (LCA). Hereditary blindness generally appears at birth or within the first months of life, but it may also affect young adults.

5,000 Quebecers have learned that they suffer from hereditary blindness (RP or LCA) and will now have access to new treatments.

These conditions can have devastating consequences for the people who suffer from them and those around them, and require radical lifestyle changes. Blindness in adults can frequently lead to loss of employment. The costs associated with job loss, as well as the provision of services for the blind, represent millions of dollars of annual expenditure for Québec taxpayers.

Robert Koenekoop, ophthalmology researcher at the Montreal Children's Hospital of the McGill University Health Centre, has devoted his career to finding the causes and possible treatments of this disease which, until recently, was considered to be incurable. He has established a research program dedicated to identifying and classifying the genes responsible for retinal blindness caused by RP and LCA.

The researcher and his team have developed a four-step protocol to help them discover new genes responsible for the disease and to accelerate the identification of mutations: using DNA chips, they can identify in just a few hours the region of the patient's genetic code where a mutation is located. A DNA chip is a small plate containing millions of short DNA fragments from a healthy individual. DNA from the patient is allowed to bind to the DNA on the plate, producing fluorescence of a different colour in any regions where the patient's code is not identical to that of the control sample.

With the help of this protocol, a new gene called NMNAT1 has been identified in Quebecers with LCA. As this gene plays a role in neuronal protection, a defective NMNAT1 can lead to premature photoreceptor death. This gene had never previously been associated with any human disease.

Just six months after the gene's discovery, treatment for mutations in NMNAT1 was being tested. Patients with NMNAT1 variants are now admissible for a clinical trial aimed at testing a new molecule called QLT091001. QLT09100 restores vision by replacing an essential molecule that is no longer produced by cells with a NMNAT1 mutation.

A safety and efficacy study conducted on 14 patients showed significant improvements in vision. These studies were carried out at the Ocular Genetics Laboratory of McGill University, which provides patients with accurate diagnosis and prognosis as well as counselling on the various treatment options.

Thanks to the services of this clinic, one of its kind in Canada, and recent advances in genetics research, some 5,000 Quebecers have learned that they suffer from hereditary blindness (RP or LCA) and will now have access to new treatments or treatments currently under development.