Hearing management

Updated 07 December 2017

Gene therapy for deafness moves a few steps closer

Gene therapy to improve hearing in those with genetic deafness has shown promise in a new trial - a treatment that could greatly improve the quality of life of children born with hearing impairments.

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Gene therapy for deafness is moving closer to reality, with new research on Wednesday showing the technique for fixing faulty DNA can improve responses in mice with genetic hearing loss.

Separately, a clinical trial backed by Novartis is under way to help a different group of people who have lost their hearing through damage or disease.

After missteps in the late 1990s and early 2000's, when safety scares set back research, gene therapy is enjoying a renaissance, with positive clinical results recently in conditions ranging from blood diseases to blindness.

"We are somewhat late in the auditory field but I think we are getting there now," said Tobias Moser of the University Medical Center Gottingen, Germany, who was not involved in the new research. "It's an exciting time for gene therapy in hearing."

A key element in current optimism is the development of better and safer viral delivery systems for getting corrective genes into the body. In the case of deafness, this involves injecting a gene-carrying engineered virus into the inner ear.

Read: Leaving childhood deafness untreated can be dangerous

Tackling hearing loss

There are currently no approved disease-modifying treatments for disabling hearing loss, which affects some 360 million people, or 5 percent of the world's population, according to the World Health Organisation.

Much of the hearing loss in older people is noise-induced or age-related, but at least half of deafness that occurs before a baby learns to speak is caused by defects in one of more than 70 individual genes.

It is these infants Swiss and U.S. researchers hope to help, after showing that replacing a mutated gene improved the function of hair cells of the inner ear and partially restored hearing in deaf mice.

Scientists from the Ecole Polytechnique Federale de Lausanne and the Boston Children's Hospital, who reported their work in the journal Science Translational Medicine, tested hearing in newborn mutant mice by seeing how high they jumped when startled by a noise.

Read: Is your child hearing you?

TMC1 gene is key

The team focused on a gene called TMC1, which is a common cause of human genetic deafness, accounting for 4 to 8 percent of cases. But other forms of hereditary deafness could also be fixed using the same strategy.

Jeffrey Holt of Boston Children's said the technique still needed "tweaking" but he hopes clinical trials will start within five to 10 years.

Work at Novartis is more advanced, with the first patient treated last October in an early-stage clinical trial that will recruit 45 subjects in the United States, with results due in 2017. 

The Swiss company's product, acquired in a 2010 deal with GenVec worth up to $214 million, delivers a gene called Atoh1 that acts as a master switch for turning on the growth of inner ear hair cells that are central to hearing.

Novartis research head Mark Fishman describes it as a "spare parts" approach to fixing ageing-related frailty.

The process offers hope to adults whose hair cells have been damaged by excessive noise, disease or exposure to certain drugs, including some antibiotics. But it will not help the one to three babies per 1,000 born with severe genetic hearing loss in both ears.

"There are a big range of deafness types needing different approaches," said Moser.

Read more:

1.1 billion youths risk hearing loss due to loud music

Can hearing aids reduce forgetfulness?

What are the symptoms of hearing deficiency?

 

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Hearing Expert

Dr Kara Hoffman graduated from UCT in 2004, thereafter she completed her year of community service in Durban. In 2010 she completed her Masters Degree in Paediatric Aural Rehabilitation from UKZN. In 2016, she became a Doctor of Audiology through the University of Arizona (ATSU). Dr Hoffman and her partner Lauren Thompson opened a fully diagnostic audiology practice called Thompson & Hoffman Audiology Inc. In 2011 with world-class technology and equipment to be able to offer the broad public all hearing-related services including hearing testing for adults and babies, vestibular (balance) assessments and rehabilitation, industrial audiology, hearing devices, central auditory processing assessments for school-aged children, school screening, neonatal hearing screening programmes at Alberlito and Parklands Hospital, cochlear implants and other implantable devices, medicolegal assessments and advanced electroacoustic assessments of hearing. Thompson and Hoffman Audiology Inc. are based at Alberlito Hospital in Ballito, St Augustines Hospital in Durban and at 345 Essenwood Road, Musgrave. The practices are all wheelchair friendly. There are three audiologists that practice from Thompson & Hoffman – including Dr Kara Hoffman, Lauren Thompson & Minette Lister. The practice boasts professional, highly qualified, and extensive diagnostic services where all your hearing healthcare needs can be met. The additional licensing in vestibular assessment and rehabilitation, paediatric rehabilitation and cochlear implantation places this practice in one of the top specialist audiological positions in South Africa, with a wealth of experience in all clinical areas of audiology and is a very well respected and sought-after practice.

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