Image showing the inner ear highlighted


Contributed by Joy Victory, managing editor, Healthy Hearing
Last updated 2020-01-20T00:00:00-06:00

An experimental hearing loss drug that’s delivered directly into the eardrum moved to the next phase of drug testing, reported Massachusetts-based Frequency Therapeutics, the drug’s developer, in late 2019.

Image showing the inner ear highlighted
The experimental drug is delivered via

injection into the middle ear, where

it is absorbed by the inner ear.

The drug, dubbed FX-322, is given via injection into the ear drum. Researchers hope it will successfully and safely convert stem cells into stereocilia, the hair cells in the cochlea that are responsible for hearing.

The drug is now being tested in what’s known as a phase 2a trial for noise-induced hearing loss and idiopathic sudden sensorineural ​​​​​​hearing loss

A phase 2a clinical trials means they’ll continue to explore the drug’s safety, as they did in previous trials. Researchers also will look more closely at dosing requirements and effectiveness. The trial is scheduled to end in September 2020.

Clinical trial of hearing loss drug

The federal Clinical Trials registry states the trial “will assess the exploratory efficacy, as well as the local and systemic safety of single and repeat intratympanic doses of FX-322 compared to placebo in approximately 96 subjects with stable mild to moderately severe sensorineural hearing loss, with a medical history consistent with either excessive noise exposure or idiopathic sudden sensorineural hearing loss.”

Let’s break that down into more understandable terms:

Exploratory efficacy: “Exploratory” means the researchers are trying to determine the best and safest dose, and whether that dose should be given once or multiple times. Efficacy means how well the drug works. They’ll also be watching for any negative impacts on the inner ear (local), and the entire body (systemic), such as high blood pressure. Note: Because the total number of study participants is only going to be around 96 people, and the dosages and frequencies will vary, the true effectiveness of the drug won’t be known until larger clinical trials are held.

Intratympanic doses of FX-322: “FX-322” is the current name for the experimental drug. That will likely change if the drug is approved. “Intratympanic” means it’s given inside the ear drum, via injection. 

Compared to placebo: Some people in the trial will get the drug, while others will get injections containing non-active ingredients. The trial also will be randomized and double-blinded, meaning neither the study participants nor the people administering the drug testing will know who is getting the drug versus the placebo. Only the researchers will know. 

If all goes well, the next step is a larger phase 2b trial, which determines the best dosage before starting a large, more rigorous phase 3 trial. Phase 3 trials are generally the last step before a drug is reviewed by the FDA. 

How are they measuring the drug’s effectiveness?

Over a span of about 200 days, the researchers will track changes in several common hearing tests, including:

  • speech audiometry (word recognition, and speech-in-noise),
  • pure-tone audiometric testing, 
  • tinnitus functional index,
  • and self-reported assessments of hearing handicap and impacts on quality of life. 

They’ll also measure any adverse events (side effects), as well as any abnormal changes in anatomy and ear pressure.

This drug isn’t being tested for age-related hearing loss

No cure yet

The trials are an important contribution to research on reversing certain types of sensorineural hearing loss, one of the most common forms of hearing loss among the 48 million Americans who report some degree of hearing impairment.

Specifically, sensorineural hearing loss is caused by damage to hair cells of the inner ear and/or the auditory nerve that connects the ear to the brain. Damage can be caused by genetic disorders, the aging process and/or from either a one-time or prolonged exposure to excessive noise.

It’s unclear if the experimental drug (if approved) could ever be used for age-related hearing loss, since they are not testing it for that type of sensorineural hearing loss.

Currently, sensorineural hearing loss is typically treated with hearing aids or cochlear implants, which work with a person’s remaining sense of hearing to amplify sounds. Although today’s digital hearing devices are more effective than they were 10 years ago, they do not restore the sense of hearing to its normal state.

Still experimental and far from being approved

The study’s researchers envision these drugs will eventually be injected into the middle ear, much like injections currently used to treat infections, but the treatment is far from being available at your local hearing center. New drug therapies must undergo extensive efficacy and safety testing and approval from the Food and Drug Administration (FDA) which can take many years.

If you have hearing loss now, hearing aids and other assistive listening devices are still the best treatment for sensorineural hearing loss for the foreseeable future.


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