Gene therapy restores hearing in mice

After researchers successfully restored hearing in mice suffering from genetic form of deafness with gene therapy, plans are afoot to use the treatment on humans.

Jeffrey Holt of Boston Children's Hospital and Harvard Medical School said that their gene therapy protocol was not ready yet for clinical trials as they needed to refine it a bit more, though, in the not-too-distant future he thought it could be developed for therapeutic use in humans.

The researchers tested gene therapy in two types of mutant mice, with one type having the TMC1 gene completely deleted, a good model for recessive TMC1 mutations in humans - children with two mutant copies of TMC1 had profound hearing loss from a very young age, usually by around 2 years.

The researchers were able to restore the ability of sensory hair cells to respond to sound in the recessive deafness model. With the gene therapy in TMC1 model, sensory hair cells were able to respond to sound producing a measurable electrical current. The therapy also restored activity in the auditory portion of the brain stem.

Gene therapy in the dominant deafness model, with a related gene, TMC2 proved to be successful at the cellular and brain level, and was partially successful at restoring actual hearing in the startle test.

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

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

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

According to Novartis research head Mark Fishman, it was a ''spare parts'' approach to fixing ageing-related frailty.

The therapy held out hope for adults whose hair cells had been damaged by excessive noise, disease or exposure to certain drugs, including certain antibiotics.

It would however, not help the one to three babies per 1,000 born with severe genetic hearing loss in both ears.