Clinical trial results have revealed that several children who were born with a rare and inherited form of deafness are now able to hear because of two gene therapies.
Gene Therapies For Restoring Hearing
The therapies aim for the otoferlin gene, a protein within the inner ear that lets nerve cells translate sound vibrations into electrical signals that the brain can interpret. Otoferlin gene mutations account for roughly 1% to 8% of congenital deafness cases. This refers to when a child is born deaf.
However, mutations in this gene are quite rare. Estimates reveal that roughly 200,000 people across the world are affected by it.
The novel gene therapies make use of modified and harmless viruses to bring otoferlin genes right into the inner ear. Early data shows that the therapies work for the majority of patients. However, further research is necessary to gain full approval for such treatments.
Associate scientist Zheng-Yi Chen from the Eaton-Peabody Laboratories of Mass Eye and Ear, who is also an associate professor from Harvard Medical School, explains that the study results are quite remarkable, as they were able to observe that the children's hearing ability dramatically improved on a week-to-week basis.
The trial results were published in the "AAV1-hOTOF gene therapy for autosomal recessive deafness 9: a single-arm trial" study. Researchers will also present the findings during the Association for Research in Otolaryngology's (ARO) annual meeting.
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Restoring Hearing Among Children
The clinical trials covered six children who received hospital treatment at an institution associated with Shanghai's Fudan University. Each kid had two otoferlin mutant copies. Prior to treatment, they had total hearing loss. These children were one to six years in age.
The gene therapy that was administered contained adeno-associated viruses, which are a certain type of virus that is usually employed for gene therapy. The genes were taken out and replaced with the focused otoferlin gene.
However, due to the large size of the otoferlin gene, the genetic material is typically split further into half. The portions are then placed inside each vessel.
Previously, the researchers tested the treatment's effectiveness and safety among animals, including other primates and mice.
As part of the trial, the gene therapy was injected into one of the child's ears. This was done through a membrane that separates the middle from the inner ear. All the children, except one, exhibited great hearing recovery in 26 weeks. These improvements started surfacing roughly four to six weeks after treatment, along with improvements in the speech perception of the kids.
Three out of the five children had a cochlear implant in their ear that was not treated. These aid with hearing by bypassing within the inner ear, offering another channel for sound to arrive at the brain. This allows children with deafness associated with otoferlin to hear some sound. However, the sound quality is not as full and rich.
After undergoing treatment, the said three children had improved speech perception and verbal communication through phone and in person with implants turned off. The two children who did not have implants moved from being unable to perceive speech to being able to hear it for the first time.
No serious side effects resulted from the treatment, though there were temporary and mild effects, such as fever and transient white blood cell count changes. However, further research involving a larger sample group is necessary to determine the dosage of a single therapy that would be most effective and safe.
Similar Gene Therapy
Aside from this, a similar gene therapy trial also began recently in the US. On October 2023, an 11-year-old boy became the first to be treated as part of the clinical trials in the US. During his procedures, one of his eardrums was partially lifted by the doctors. The specialists then added a medical device to the membrane that separates the inner and middle ear. The said device brought gene therapy to the cells of the inner ear.
Now, roughly four months post-treatment, the child has gone from profound deafness to having just mild to moderate hearing loss.
This boy is the first recipient of the therapy in the US. The initial findings will also be presented at the ARO meeting. The findings also pave the way for trial researchers to conduct tests among younger children.
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