By: Bec Crew/Science Alert A small and preliminary clinical trial has found that injecting a common cold-like virus into the eyes of age-related macular degeneration (AMD) patients – one of the leading causes of blindness in the US – can halt and even reverse the progression of the disease.
The results will need to be replicated in a much larger group of patients, but the early signs suggest that a single injection of the specially engineered virus can kick the body’s natural immune response into gear, and clear out the fluid that causes permanent vision loss.
The approach, trialled by researchers at Johns Hopkins Medicine in Maryland, targeted a protein called vascular endothelial growth factor (VEGF), which is overactive in people with wet AMD – a rare and more severe form of the disease, which causes new blood vessels to grow beneath the retina and leak blood and fluid into the eye.
This build-up of fluid causes permanent damage to light-sensitive retinal cells, prompting them to progressively die off, leaving blind spots in the center of a person’s vision. Wet AMD affects around 10 percent of all AMD patients.
While treatments do currently exist for wet AMD, they involve getting injections in the eye once every four weeks – and if you want to maintain the benefits, you have to keep up those monthly injections for the rest of your life.
Side effects of current medications include eye infections and a heightened risk of stroke.
What the team at Johns Hopkins has demonstrated in a handful of patients is that, in some cases, there could be a way to halt and even reverse the progression of wet AMD with a single injection.
“This preliminary study is a small but a promising step towards a new approach that will not only reduce doctor visits and the anxiety and discomfort associated with repeated injections in the eye but may improve long-term outcomes,” says one of the team, Peter Campochiaro.
“[P]rolonged suppression of VEGF is needed to preserve vision, and that is difficult to achieve with repeated injections because life often gets in the way.”
The phase 1 clinical trial involved 19 men and women, who were 50 years or older, with advanced wet AMD.
They were divided into five groups that received increasing doses of a viral vector called AAV2 – a common cold-like virus that’s been genetically engineered to penetrate the patients’ retinal cells and deposit a gene that prompts the production of a protein called sFLT01.
“After the virus deposited the gene, the cells began secreting sFLT01 which bound to VEGF and prevented it from stimulating leakage and growth of abnormal blood vessels,” the team explains.
“The goal is for the retinal cells infected by the virus to produce enough sFLT01 to permanently stop the progression of AMD.”
Previous research has shown that sFLT01 can inactivate VEGF, but until now, scientists had struggled to get the body to produce it on its own – instead, they’ve had to regularly inject VEGF-suppressing proteins to keep it at bay.
The first three groups were given the lowest doses of the AAV2 virus, and after they showed no negative side effects, the final two groups were given the maximum dose. No severe side effects were observed in either group.
“Even at the highest dose, the treatment was quite safe. We found there were almost no adverse reactions in our patients,” says Campochiaro.
The 19 participants were all selected based on their lack of response to all other standard treatment options – eight of which were unlikely to respond even to their new treatment.
Of the remaining 11, four showed dramatic improvements after a single viral injection, with the amount of fluid in their eyes reducing from severe to “almost nothing”, the team reports. Two more patients experienced a partial reduction in the amount of fluid in their eyes.
The remaining five patients weren’t so lucky, experiencing no improvement in vision after the injection, but for good reason – the researchers realized that their bodies naturally produced antibodies that attack the AAV2 virus.
And therein lies the rub, because the researchers suspect that these natural antibodies could be widespread in the US at least, because of adeno-associated viral infections – a relative of the AAV2 virus – are quite common.
It will take a much larger clinical trial to figure out if the almost 50-50 chance of success in this study is an accurate indication of how the wider population will respond to their new treatment, but it’s a promising development.
With advanced age-related macular degeneration expected to increase from approximately 2.07 million Americans in 2010 to 5.44 million in 2050, the treatment that works for only half of wet AMD patients could still change hundreds of thousands of lives.