• Experimental treatment injected into ear could restore hearing by growing new ‘hair’ cells
For more than half a century, hearing aids have been the only effective treatment for the millions struggling with deafness.
But they can be unsightly, uncomfortable and, in the eyes of some, label users as ‘old’ before their time.
Now, scientists are testing new drugs that could banish hearing aids for good for people with moderate to severe deafness.
Two major clinical trials have started in recent months, which, it is hoped, will produce ground-breaking medicines capable of helping millions who cannot hear properly.
Both studies involve injecting experimental medicines into the ear with the intention of repairing the damage that caused the hearing loss in the first place.
Scientists at University College London’s Ear Institute are taking part in an international trial injecting a drug called a gamma-secretase inhibitor into the ears of 24 patients who have had partial deafness for up to ten years and use a hearing aid.
They believe the drug will restore hearing by stimulating the growth of healthy new ‘hair’ cells deep inside the ear.
In a healthy ear, sound enters the cochlea (a snail-shaped compartment inside the ear) and is picked up by sensory cells that resemble tiny hairs.
These hairs convert sounds into an electrical impulse that can travel along the auditory nerve to the brain.
These hairs can be damaged or destroyed by ageing, loud noise or infection and, until recently, it was thought it was impossible to regenerate them.
But laboratory tests at the Massachusetts Eye and Ear Infirmary in Boston in 2013 found that injecting gamma-secretase inhibitors into a type of cell called a progenitor cell led to the growth of healthy new hair cells. Progenitor cells are a form of stem cell that, unlike most stem cells, cannot develop into almost any form of body tissue.
Instead, they are more likely to develop into ‘local’ cells, according to where they are in the body.
So progenitor cells in the inner ear are most likely to develop into cells typically found in the ear — such as the tiny hair cells that transmit sound. However, a protein, called a notch protein, stops that from happening. The new drug works by blocking the effects of the notch protein, allowing the progenitor cells to turn into hair cells.
Tests to make sure the drug is safe were completed on 24 patients in the UK at the end of 2017. Each volunteer had three, weekly injections into the eardrum, using a local anaesthetic first to numb the eardrum.
Trials to measure how effective it is could now begin within the next few months.
Meanwhile, U.S. firm Frequency Therapeutics, is working on a similar treatment that also stimulates progenitor cells to grow into healthy hair cells.
It is using a treatment codenamed FX-322, made up of an undisclosed combination of different drugs.
In December, at the Royal Victorian Eye and Ear Hospital in Melbourne, Australia, the first nine patients were injected with FX-322 to check its safety.
None of them suffered significant side-effects and more in-depth studies will be carried out over the next two years.
FX-322 involves a one-off injection into the ear of a slow-release gel, which allows the active medicine to gradually seep into the inner ear over the space of a few days, to increase the time that progenitor cells are exposed to the drug — and potentially improving the chances of success. The landmark treatments could not only reduce the need for hearing aids, but also for cochlear implants — the high-tech devices that restore hearing to the profoundly deaf.
These bypass the damaged inner ear and stimulate the auditory nerve, which carries sound to the brain. Around 14,000 people in the UK currently have a cochlear implant, which cost around £40,000 each.
Source: The Guardian News