Scientists are of the opinion that a set of HIV drugs, which is 30 years old, could at some point be useful in preventing the main cause of visual impairment and blindness in the UK.
This is the result of a study which was led by the University of Kentucky, in collaboration with scientists from Cardiff University. It was found that Nucleoside Reverse Transcriptase Inhibitors (NRTIs) which have been in use for the past three decades, initially as a treatment for cancer, but later used to combat HIV, may now be effective in the treatment of age-related macular degeneration (AMD) and other inflammatory disorders.
AMD affects around 600000 people in Britain and is a progressive condition, which is not treatable in around 90% of patients. There are two types of AMS – dry and wet. They are classified by the absence or presence of blood vessels which have entered the retina. An understanding of the molecular mechanisms related to wet AMD has resulted in several treatment methods. However, there are no treatment options for dry AMD, but the latest research offers new hope.
Dr Mark Young, based at the School of Biosciences, stated their excitement at finding that NRTIs were effective in treating AMD by blocking the signals from a protein molecule which is already known to be involved in a range of inflammatory disorders. He said their new research offers the first evidence of a potential therapy for dry AMD, with an existing drug. He added that it also opens the doors for repurposing of the NRTI family of drugs in treatment for a range of inflammatory diseases.
He stated that the efficiency of the drug in treating AMD has only been effectively proven in mouse models. However, with the drug already having been licensed for human use, they are hoping to start clinical trials very soon.
NRTIs are widely used as anti-HIV drugs. It is believed to target the enzyme reverse transcriptase, which is vital in the replication of HIV. Previous studies discovered that there is a toxic molecule, named Alu RNA, which builds up in the retina and causes dry AMD. It has been found that HIV and Alu RNA are very similar in that both need reverse transcriptase to fulfil its life cycle.
The researchers reported that in a mouse model of dry AMD, the multiple NRTIs stopped retinal degeneration. This effect was not caused by the functioning of the drug in which it prevents reverse transcriptase, but rather from it blocking a pathway, called the ‘inflammasome’ which prevented the NRTIs from blocking reverse transcriptase.
The scientists also indicated that NRTIs had an impact in other diseases which share the same signalling pathways as the dry AMD model, including wet AMD. Wet AMD, even after treatment, does not result in a substantial improvement in vision in around 67% of patients.
Image Credit: Ahmed Sinan