A class of drugs developed to treat HIV could be useful in treating age-related macular degeneration, a disease that leads to progressive loss of vision.

A class of 30-year-old HIV drugs could in future be used to prevent a common cause of incurable blindness, scientists believe.

Nucleoside Reverse Transcriptase Inhibitors (NRTIs) were originally developed to treat cancer but later harnessed to combat HIV and AIDS.

New research shows that they block an inflammatory pathway closely linked to age-related macular degeneration, a disease that leads to progressive loss of vision.

There are two forms of AMD, wet and dry, classified by the presence or absence of blood vessels invading the retina. Although several therapies exist for the wet form, there is no approved treatment for dry AMD.

Dr Mark Young, from the Cardiff University School of Biosciences, said: "Our work presents the first evidence for a potential therapy for the untreatable dry form of AMD, a condition which affects millions of people worldwide, with a drug that is already approved for use in humans.

"It also paves the way for repurposing of the NRTI drug family for treatment of a wide variety of inflammatory diseases."

The drugs target a cell-surface protein called P2X7 that is known to play a role in a number of inflammatory disorders. In the study, a number of different NRTIs were found to prevent retinal degeneration in mice affected by AMD.

"So far the efficacy of the NRTIs in combating AMD has only been proven in mouse models, but given that the drug is already licensed for use in humans, we hope that clinical trials can begin as soon as possible," said Dr Young.

The research, led by a US team from the University of Kentucky, was reported in an online edition of the journal Science.

NRTIs are the most widely used class of anti-HIV drugs. They act on the enzyme reverse transcriptase which is necessary for the replication of HIV.

Previous research has shown that a toxic molecule called Alu RNA that accumulates in the retina in patients with dry AMD also depends on reverse transcriptase.

AAP.