For the first time, scientists have been able to delay — and in some cases reverse — a hereditary blindness disorder called Leber’s hereditary optic neuropathy using a daily drug treatment. The disease is a mitochondrial disease that causes the rapid onset of blindness in men in their twenties. It leads to total loss of vision within three to six months after the first symptoms begin to appear. This marks the first time that an inherited mitochondrial disease has been treated using a drug.
Researchers from Newcastle University (UK) led by Patrick Chinnery conducted a clinical trial of the drug Idebenone. During the six month trial 55 people were given the drug, and 30 were given a placebo. The study showed that 11 people who received the drug were able to read an extra two lines of increased difficulty on a standard vision chart, and nine people who couldn’t read at all were able to discern letters by the end of the trial. No negative side effects of the drug were reported. While the improvement of just 20 patients may not seem like much, it does suggest that Idebenone has a significant effect on restoring sight when the disease is caught in an early stage.
According to Chinnery, this gives the researchers hope that other mitochondrial diseases could be treated. But, hope is not the same thing as a cure and the researchers want to be clear that what they have developed is a groundbreaking treatment option, not something that is going to cure blindness for everyone. Among the patients who received the drug, the researchers noticed that the people who benefitted most were those who had better vision in one eye over the other at the onset of the trial. This means that the disease is probably more treatable by the drug when it is in its early stages.
Leber’s hereditary optic neuropathy attacks the retinal ganglion cells in the eye. These cells connect the light-sensitive retina cells to the brain through the optic nerve. When mitochondrial enzymes fail to generate energy by delivering electrons to the cells, damage to these structures occurs. Idebenone is believed to step in where the defective enzymes fall down on the job.
This type of blindness is hereditary, meaning that it is passed on genetically. According to Chinnery, if a test were developed to identify the carriers of this disease before it set in, it might be possible to prevent the blindness from taking hold in the first place by administering Idebenone. The research was published in the neurology journal Brain.