An 11-year-old boy who was born with congenital hearing loss has become the first patient to receive a new gene therapy procedure, and it’s allowed him to hear sounds for the first time in his life.
“Gene therapy for hearing loss is something that we physicians and scientists in the world of hearing loss have been working toward for over 20 years, and it is finally here,” said Dr John A. Germiller, Director of Clinical Research in the Division of Otolaryngology at Children’s Hospital of Philadelphia (CHOP), in a statement.
“While the gene therapy we performed in our patient was to correct an abnormality in one, very rare gene, these studies may open the door for future use for some of the over 150 other genes that cause childhood hearing loss.”
The patient, Moroccan-born Aissam Dam, has an extremely rare form of deafness that is thought to affect only about 200,000 people worldwide. It is caused by a recessive mutation in the otoferlin (OTOF) gene. Dam was born with profound hearing loss in both ears, but for safety reasons, the researchers had to start by treating only one ear.
During surgery, the patient’s eardrum was partially lifted to open a tiny access window into the cochlea. A single dose of the experimental gene therapy was then inserted directly into the inner ear – a harmless viral vector containing copies of the normal OTOF gene. The idea is that having the functioning gene in place will allow the sensory cells to transmit signals along the auditory nerve to the brain, as happens in hearing people, although the scientists weren't certain it would work in someone who had been deaf for 11 years.
However, four months later, the hearing in the treated ear has recovered to only mild/moderate hearing loss, meaning that Dam can hear sounds for the first time in his life. In an interview with the New York Times, with the help of a translator, his father explained how he could hear traffic noises only days after the surgery.
“There’s no sound I don’t like,” Dam expressed through interpreters. “They’re all good.”
The surgical technique that makes this treatment possible was developed 10 years ago by Dr Germiller, and it is used for a different diagnostic procedure in young children. Combining this with cutting-edge gene therapy research from Akouos, Inc., a subsidiary of pharma giant Eli Lilly and Company, has led to the current clinical trial.
“As more patients at different ages are treated with this gene therapy, researchers will learn more about the degree to which hearing is improved and whether that level of hearing can be sustained over many years,” Dr Germiller said. “What we have learned from following this patient’s progress will help direct our efforts toward helping as many patients as we can.”
The New York Times reports that another child was similarly treated in Taiwan towards the end of last year, and the CHOP team has two further candidates lined up for surgery. A 3-year-old boy from Miami and a 3-year-old girl from San Francisco will both be treated in one ear, while their other ears have already been fitted with cochlear implants.
If the trials continue to produce such positive results, attention is likely to turn to the other 150-plus genes that are implicated in congenital hearing loss. However, the idea of providing a “treatment” for deafness at all is a controversial one, with some members of the Deaf community rejecting the characterization of hearing loss as a disability.
In cases where parents do choose to seek treatment for their children born with hearing loss, the results of this trial represent an exciting possibility for the future.
“For decades people have been saying, ‘When is this going to work?’,” Dr Margaret Kenna, an otolaryngologist and professor of otolaryngology at Harvard Medical School, told the New York Times. “I didn’t think gene therapy would begin in my practice lifetime. But here it is.”
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