An international group of scientists has discovered that a class of HIV drugs used for the last three decades to treat people suffering from Aids could be re-purposed to block and prevent blindness amongst elderly people.

Nucleoside reverse transcriptase inhibitors (NRTIs) are a class of antiretroviral drugs including AZT, ddl, 3TC and FTC that have been widely used in the world to treat people with HIV since the 1960s.

NRTIs are used to block an enzyme used by the HIV virus to replicate itself in the human body, but new research shows that these drugs are also able to block the activity of the inflammasome, a biological pathway responsible for activating inflammatory processes in the body.

In particular, when the researchers experimented with the NRTIs on mice, the drugs were able to block inflammasome proteins from killing cells in the mice retinas, thus preserving their vision.

Their research, entitled "Nucleoside reverse transcriptase inhibitors possess intrinsic anti-inflammatory activity" is published in the journal Science.

What is AMD?

Age-related macular degeneration (AMD) is a progressive, painless eye condition that leads to the gradual loss of central vision, i.e. the ability to see objects that are located directly in front of you.

According to the researchers, AMD will affect 200 million people by 2020 as the world's aging population continues to grow, so something must be done about it now.

There are two forms of the condition – wet AMD, where blood vessels succeed in getting into the retina, and dry AMD, where a build-up of waste products called drusen similarly cause damage to the part of the eye known as the macular.

At present, AMD is untreatable in up to 90% of patients and is the leading cause of blindness amongst elderly people.

NRTIs could treat graft-versus-host disease

The HIV drugs could also be used to treat other inflammatory disorders, such as graft-versus-host disease, a rare problem where the white blood cells in a stem cell or bone marrow transplant start attacking the cells in the recipient's body.

The idea of blocking inflammasome proteins itself is not new, and there has been a lot of research in recent years into how blocking the pathway could help with other conditions, from traumatic central nervous system injuries to breast cancer progression to helping wounds to heal faster in diabetic patients.

"Repurposing of NRTIs could be advantageous, for one, because they are very inexpensive. Moreover, through decades of clinical experience, we know that some of the drugs we tested are incredibly safe," said Benjamin Fowler, the lead author and a postdoctoral fellow in the Department of Ophthalmology & Visual Sciences at the University of Kentucky.

"Since these NRTIs are already FDA-approved, they could be rapidly and inexpensively translated into therapies for a variety of untreatable or poorly treatable conditions."

The study was led by Dr Jayakrishna Ambati, professor & vice chair of the Department of Ophthalmology & Visual Sciences at the University of Kentucky, with collaboration from Cardiff University; the Institute of Genetics and Biophysics, CNR; the US National Cancer Institute; the University of Calgary, Chapman University School of Pharmacy and the University of Southern California.