It depends on the nature of the hearing loss, for example, FX-322 and OTO-6XX appear to work by triggering regeneration of hair cells, while OTO-413 appears to

It depends on the nature of the hearing loss, for example, FX-322 and OTO-6XX appear to work by triggering regeneration of hair cells, while OTO-413 appears to work by triggering regeneration of synaptic connections (both of which are probably egregious oversimplifications because I am a security nerd, not a medical researcher :P)