Sierra Smith holds her son, Travis, whose deafness was successfully treated with gene therapy. Regeneron Pharmaceuticals hide caption

toggle caption

Regeneron Pharmaceuticals

The Food and Drug Administration approved the first gene therapy to restore hearing for people who were born deaf.

The decision , while only immediately affecting people born with a very rare form of genetic deafness, is being hailed as a milestone in the quest to treat hearing loss.

"It's the first time in history there's a new drug for hearing loss," says Zheng-Yi Chen , an associate scientist at Mass Eye and Ear in Boston who was not involved in the development of the therapy approved by the FDA Thursday. But his research team reported very promising results with a similar approach Wednesday.…