A single-dose gene therapy restored hearing in rare genetic deafness. Digest
What if deafness could be treated with a single injection instead of a lifelong device? A new clinical trial tested whether gene therapy could improve hearing in people born with mutations in a key hearing gene.
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The study included 10 participants aged 1.5 to 23.9 with a condition called OTOF-related hearing loss. The OTOF gene provides instructions for making otoferlin, a protein that allows inner ear cells to send signals to the auditory nerve. When otoferlin is missing or not working properly, sound can still be detected by the ear, but the signal is not properly transmitted to the brain. To address this, researchers injected a harmless virus carrying a working copy of the OTOF gene directly into the cochlea, the part of the inner ear that converts sound vibrations into electrical signals the brain can interpret.
- While responses varied widely, hearing improved in all participants.
- On average, pure-tone hearing thresholds, a measure based on a hearing test that captures the quietest sounds a person can hear, improved from 106 to 52 decibels (dB) by six months.
- Most of the total hearing improvement occurred within the first month after treatment.
- Objective hearing tests also improved. These tests measured how well sound signals traveled from the ear to the brain. After treatment, participants' brains responded to much quieter sounds than before, with improvements of about 16 to 53 dB, depending on the type of test.
- The strongest gains were seen in children between 5 and 8 years old. One 7-year-old improved enough to hold everyday conversations with her mother without using her hearing device (cochlear implant) or lipreading. However, a 14-year-old and a 23-year-old also experienced benefits.
- Safety was encouraging, as no serious complications occurred.
This was a small, early-stage study that lacked a control group, included only one adult, and followed participants for just 6 to 12 months. The researchers also could not fully explain why responses varied so much between individuals. Nevertheless, the results add to the growing evidence that gene therapies may be a promising way to treat a range of genetic diseases. In episode #77, Dr. George Church discusses revolutionary technologies in the field of genetic engineering.