SHANGHAI -- Using an experimental gene therapy, a team led by Chinese scientists has recovered the hearing of five children born with a genetic defect that had left them profoundly deaf.

In a first-in-human clinical trial, they demonstrated the safety and efficacy of the gene therapy in treating patients with hereditary deafness, which afflicts up to 26 million people worldwide.

The researchers from the Eye & ENT Hospital of Fudan University developed the gene drug RRG-003 by mounting a human OTOF transgene on adeno-associated virus.

Then, they enrolled six eligible children with the autosomal recessive deafness 9. The deafness is caused by a mutation in the OTOF gene that is known for resulting in the failure to properly transmit sound stimulation signals from the ear to the brain.

After they administered the medicine into the patient's inner ear with a single injection, five participants showed significant recovery of auditory and speech functions, according to the study recently published in the journal Lancet.

The average auditory brainstem response threshold improved from greater than 95 dB at baseline to as low as 38 dB in one participant by the 26-week mark. Speech perception was then restored in participants who experienced hearing recovery.

The gene therapy is shown to be safe and efficacious as a novel treatment for children with autosomal recessive deafness 9, said the researchers.

Individuals from Southeast University in China and Harvard Medical School in the United States collaborated in the study.