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Aug 13, 2015
 |  BC Innovations  |  Tools & Techniques

Helping Beethoven hear

How gene therapy could become the first therapeutic for genetic hearing loss

Little progress has been made in developing therapies for hearing loss that go beyond the temporary and partial solutions provided by hearing aids and cochlear implants, and most company activity is focused on acquired forms of the disease. Now, a group at Boston Children's Hospital has looked at genetic causes of deafness and designed a gene therapy to restore function in TMC1, one of the disease's most commonly mutated targets.

Attempting gene therapy is still relatively uncommon in hearing loss. Novartis AG and GenVec Inc. have the CGF166 gene therapy in Phase I/II testing for acquired hearing loss, but the majority of companies in the space have programs based on small molecules. (See Table: Commercial programs in hearing loss)

Now, in a study published in Science Translational Medicine, the Boston researchers have shown that TMC1 gene therapy reversed hearing loss in the Beethoven strain of mice that modeled an adolescent-onset form of the disease, and restored function in a second model that mimicked neonatal deafness.

Jeffrey Holt, principal investigator on the study, told BioCentury that the ear is a good organ for gene therapy because, like the eye, it is a relatively self-contained, fluid-filled space. "What you inject into the inner ear tends to stay there and not go systemic," he said. "It is also immunoprivileged to some degree, so gene therapies won't induce a strong immune response." Holt is associate professor of otolaryngology at the F.M. Kirby Neurobiology Center of Boston Children's.

Although most gene therapies focus on diseases of the eye and liver, GenVec CSO Douglas Brough agreed it makes sense to extend the modality to deafness and other otologic diseases.

"The ear is one of the last unknown druggable targets, and it is really exciting that gene therapy technology is helping to move the field forward," he told BioCentury.

Despite improvements in hearing aids and advances with cochlear implants, many believe that the real goal in hearing loss should be to correct the underlying pathology.

"As great as they are, they're still devices and when your batteries run out or you take it out at night, you're still deaf," said Hinrich Staecker, professor of otolaryngology, head and neck surgery at the University of Kansas Medical Center. "In the long term, having a restorative, molecular therapeutic would be preferable."

Lawrence Lustig added that the sounds heard with cochlear implants are very mechanical. "The devices just can't make sounds like music sound very good," he said. "They are really no substitute for restoration of natural hearing." Lustig...

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