A profoundly deaf baby treated with Regeneron’s experimental gene therapy began hearing normally within six months, according to the company’s announcement. This data, presented at a medical conference, follows promising initial research from October. The baby, dosed at 11 months old, is one of the youngest to receive gene therapy for genetic deafness. A second patient, treated at age four, also showed hearing improvements after six weeks. Both children have a type of deafness caused by mutations in the otoferlin gene.