Eli Lilly is expanding its work on gene therapies to treat hearing loss[6]. Gene therapy works by having a modified virus deliver the correct version of the OTOF gene to the inner ear with a single injection[2]. This therapy is intended for patients with auditory neuropathy, which is caused by a malfunction of the OTOF gene, which created the otoferlin protein that allows the cells in the ear to communicate with the auditory nerve[1]. Experimental studies have shown encouraging results - out of six deaf children aged 1 to 7 years, five improved their hearing after the application of gene therapy[7]. Within a few weeks after the therapy, the children recovered their hearing to a sufficient extent, were able to locate the sources of sounds and recognize speech in a noisy environment[4]. Researchers are continuing studies in the US, Europe and China to expand the application of this therapy to deafness caused by other genes[4].