There's been some recent failed drugs in this space notably recently FREQ Fx-322. That also showed efficacy in mice and reached phase 2 before being dropped.
Hearing is a complicated issue, there's many connections that need to be made for hearing to work even besides the brains ability to relearn and regonize said signals.
Good news but we've been here before.
> the researchers coaxed the hair cells to regrow in mice ...
ah hell after typing that I dont know why I didnt just ask an AI that had data up till late 2021
Take a look at some hearing response graphs to get an idea of how variable it can be across the frequency spectrum.