By Peter G. Volsky, MD
Over the past two years, clinical trials of prospective medical treatments for acquired sensorineural hearing loss have multiplied.
This promising area of research is focused on experimental molecular-based pharmaceuticals that target cells in the inner ear to regenerate hearing, generally by stimulating the growth of new nerve endings or cochlear hair cells.
ENT specialists have long been interested in this potential approach, especially in light of scientific discoveries that spontaneous hair cell regrowth can occur in many species of birds, reptiles and fish that have suffered hearing damage.
Today, our field seems to be evolving in this direction as active clinical trials have progressed beyond initial safety and efficacy phases.
Just one such example is a Phase 1b clinical research study now enrolling adult patients at Eastern Virginia Medical School, which will evaluate the safety of an investigational intratympanic injection designed to restore sensory hair cells.
The multicenter, randomized, double-blind and placebo-controlled trial will examine a fixed ratio dose combination of two small molecules in patients ages 18 to 65 with severe sensorineural hearing loss.
Sensorineural hearing loss accounts for about 90 percent of all hearing loss, whether due to aging, excessive noise exposure, head trauma, ototoxic medications, malformations of the inner ear, and/or diseases such as Meniere’s. Cases also can be idiopathic in nature.
To date, medication options have centered on transtympanic corticosteroid injections, which aim to reduce cochlear hair cell swelling and inflammation. Many patients also choose to add hearing aids, cochlear implants and/or other assistive listening devices.
As momentum for more drug modalities grows, research in the past five to ten years also has explored experimental systems for delivering drugs to the inner ear more efficiently, while also better controlling the release of these pharmaceuticals.
Currently, we rely largely on systemic absorption – via oral pills or injections – or a slow diffusion achieved by using a small needle to puncture the eardrum and flooding the middle ear with injected fluids.
New approaches in the testing stage include micropumps for timed delivery of multiple drug agents, cochlear implants coated with neurotrophin-producing cells for sustained release to the spiral ganglion, and microneedles for controlled perforation of the round window membrane – potentially for improved permeability compared to an eardrum puncture.
It should be noted that research on these medications and delivery systems is proceeding simultaneously with separate trials into gene therapy and hypothermic inner ear treatments, which also are promising potential options for hearing loss patients.
As we wait for aggregated results from the latest clinical trials, physicians and interested patients should begin to consider the exciting possibility that medications for hearing loss may soon become a reality on the healthcare market.
Dr. Volsky is an Assistant Professor at EVMS and a specialist in otology, neurology and skull base surgery with EVMS Ear Nose and Throat Surgeons, practicing in Norfolk and Virginia Beach. evms.edu