IMHO, gene therapy is a double-edged sword. It can be used for good, or extreme evil..

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Several gene therapies aim to restore a protein necessary for transmitting sound signals from the ear to the brain.

Born deaf, the 1-year-old boy had never responded to sound or speech before. But after receiving an experimental treatment injected into one of his ears, he started turning his head when his parents called his name. Five months later, he spoke his first words.

The boy is one of six children with a type of hereditary deafness who are part of a gene therapy trial. Five of the children can now hear, according to results reported today in the scientific journal The Lancet. The news follows an announcement this week that yet another child born with profound deafness can hear after receiving a similar treatment developed by US drugmaker Eli Lilly.

“It’s remarkable,” says Lawrence Lustig, a hearing loss expert at Columbia University who was not involved in the trials. “We’ve never had a therapy that restores even partial hearing for someone who’s totally deaf other than a cochlear implant.”

The children were all born with a mutation in a gene that makes a protein needed for hearing called otoferlin. We hear things when sound waves in the air cause the thousands of sensory hair cells in our inner ears to vibrate and release a chemical that relays that information to the brain. Otoferlin is necessary for the release of this chemical messenger. Without it, the ear can’t communicate with the brain.

More than half of hearing loss cases in children are due to genetic causes, and otoferlin mutations account for 1 to 8 percent of those, affecting about 200,000 people worldwide.

The treatment the children received works by delivering a working version of the otoferlin gene to the inner ear. The cells of the inner ear then read this gene and produce the protein. In the US and Europe, a handful of these cutting-edge therapies have been approved, including one for a type of inherited blindness. Given just once, they’re designed to correct disease-causing genes—hopefully permanently.