An experimental gene therapy appears safe and highly effective for restoring hearing to people born with a rare form of deafness, researchers reported Wednesday.
The study, the largest and longest to date to evaluate a gene therapy for hearing loss, provides powerful new evidence that the approach may provide the first way to restore hearing to people who are deaf.
"The results are really remarkable," Zheng-Yi Chen, an associate scientist at Mass Eye and Ear in Boston who led the study, published in the journal Nature. "This is really for the first time in the whole field a brand-new treatment option for genetic hearing loss. So that's very exciting."
The results, which confirm and extend a smaller study published two years ago, are consistent with those produced by several other research groups testing similar gene therapies for several forms of genetic deafness. In fact, a treatment developed by Regeneron Pharmaceuticals could soon become the first gene therapy for deafness to win approval from the Food and Drug Administration.
Scientists are encouraged by treatment progress
The flurry of advances is spurring increased interest in screening more babies for genetic deafness so they can be treated as young as possible. Early intervention appears to produce the best results.
"Being able to restore natural hearing, I think, is a game changer for our field," said Dr. Lawrence Lustig, who chairs the Department of Otolaryngology-Head & Neck Surgery at Columbia University's medical school.
While the form of deafness treated in the new study is very rare, affecting about 50 babies born each year in the U.S., the success is prompting researchers to explore similar approaches for other rare forms of genetic deafness, which taken together are a significant cause of pediatric deafness.
Researchers also hope gene therapy may some day produce treatments for more common hearing loss caused by aging and loud noise. "It's sparking a lot of interest," Lustig says. "I know of a lot of groups that are thinking about clinical trials for these more common forms of deafness."
The new study from Mass Eye and Ear involved 42 children and adults born with autosomal recessive deafness 9 (DFNB9), which is caused by mutations in the OTOF gene. The gene provides instructions to make a protein called otoferlin, which is necessary for hair cells in the inner ear to transmit sound signals to the brain.
"The children with this mutation will be born without any hearing. They're completely deaf. They couldn't hear anything," Chen says. "You could have an explosion next to their ear, and they wouldn't have any sensation."
A virus carries a healthy gene into the ear
Chen and colleagues at Fudan University in China infused used a virus called an adeno-associated virus into the ears of the deaf patients. The virus was carrying a healthy version of the gene that had been split in half to fit into the virus. The gene carries instructions to produce a working version of the otoferlin protein.
"The idea is to put what's missing in your ear so that your cells have this protein, will be able to function and can convert the sound into the signal so we can hear," Chen says.
The approach appears to have worked for about 90% of the patients, who ranged in age from babies less than a year old to adults as old as 32, according to the new report.
The patients began to start to hear for the first time within weeks, the researchers found. Their hearing usually continued to improve for about six months, according to the report. The quality of the hearing varied, but reached near normal for many of the patients and has now lasted more than two years for some.
"Now they could hear very well," Chen says. "In some patients, they can even hear even a whisper."
And significantly, the patients who benefited could start to learn to speak, enabling them to communicate much more easily with those around them.
The results indicate that this could be a one-and-done treatment that lasts a lifetime, profoundly transforming patients' lives, Chen says. "I couldn't be more excited about the results."
The treatment appears very safe, but patients will have to be followed longer to make sure that the treatment continues to be safe and the benefits will be long-lasting.
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