Most of us know someone affected by hearing loss, but we may not fully appreciate the hardships that lack of hearing can bring. Hearing loss can lead to isolation, frustration, and a debilitating ringing in the ears known as tinnitus. It is also closely correlated with dementia.

The biotechnology company Frequency Therapeutics is seeking to reverse hearing loss—not with hearing aids or implants, but with a new kind of regenerative therapy that uses small molecules to program progenitor cells, a descendant of stem cells in the inner ear, to create the tiny hair cells that allow us to hear.

Hair cells die off when exposed to loud noises or drugs including certain chemotherapies and antibiotics. Frequency's drug candidate is designed to be injected into the ear to regenerate these cells within the cochlea. In clinical trials, the company has already improved people's hearing as measured by tests of speech perception — the ability to understand speech and recognize words.