By Fiona Macrae
Last updated at 2:07 AM on 18th October 2010
A drug based on vitamin A could prevent millions from going blind as they get older, doctors believe.
The treatment was able to stop the most common cause of blindness in old age during trials.
Researchers behind the drug, fenretinide, found it halted the advance of age-related macular degeneration, for which there is currently no cure.
They targeted the most prevalent form of the condition, known as ‘dry’ AMD, which is caused by the deterioration and death of cells in the macula – the part of the retina used to see straight ahead.
The disease robs sufferers of their sight by creating a blackspot in the centre of their vision.
It can make it impossible to carry out everyday tasks such as reading, driving and watching television.
While the less common ‘wet’ form can be treated, nothing can be done to help the bulk of patients.
The U.S. research studied fenretinide, which is derived from vitamin A, the vitamin found in carrots, and which was originally designed to tackle arthritis.
Almost 250 men and women with dry AMD took a fenretinide pill a day or a placebo.
In the highest dose, the drug halted visual deterioration after a year. This suggests that while it was unable to do anything to stop cells that were already damaged from dying, it protected healthy cells. Although the research is still preliminary, it offers promise of a treatment for the disease.
It affects millions across the world and 300,000 Britons. The number of UK sufferers could more than treble to one million within 25 years as the population ages.
Dr Jason Slakter, of New York University School of Medicine, said: ‘There are currently no effective treatments for dry AMD and the need for finding one is grave.
‘Our study wasn’t designed to give a final answer.
‘It was designed to see if there was a biological effect and if the drug was working in the way we’d expect and to find out if it was well tolerated by patents.
‘I think we answered all of these points favourably. The bottom line is that I am excited about doing more studies.’
Further, larger trials are planned for the end of next year.
If the drug lives up to its initial promise, it could be in widespread use for dry AMD by 2015.
The treatment works because in normal circumstances the eye needs vitamin A to help it see. The retina naturally uses the vitamin and is helped to do so by a compound called retinol binding protein, or RBP.
However in some patients, the vitamin can produce poisons that kill the delicate cells, leading to loss of vision.
Fenretinide acts as a decoy, attaching itself to the RBP and stopping vitamin A from causing harm, the American Academy of Ophthalmology’s annual conference heard.
Wet AMD, in which tiny blood vessels bleed into the retina, is less common, but progresses more rapidly, with central vision being lost within months of diagnosis.
Caught early enough, wet AMD can be stopped in its tracks by a technique called photodynamic therapy, which uses a light-activated dye to destroy abnormal blood vessels. Drug treatments are also available.
Fenretinide also halved the odds of the patients, who already had dry AMD, going on to develop wet AMD.
A spokesman for the research team said: ‘Years of use of fenretinide to treat cancers, rheumatoid arthritis have shown it to be safe and well-tolerated.’
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