According to the latest research it is not so much the destruction of sound receptor hair cells, rather it is damage to cochlear synapses (which in turns causes progressive auditory nerve degeneration) that is the most significant cause of both tinnitus and loss of sound clarity perception.
The only regenerative therapy I've seen targeting auditory synapses is OTO-413. The problem is Otonomy appears to be specifically trying to exclude tinnitus from its endpoints.
See:
OTO-413 in Subjects With Speech-in-Noise Hearing Impairment
"Exclusion Criteria: Subject self-reports bothersome, subjective tinnitus and is consistently aware of their tinnitus throughout much of the waking day."
It's like Otonomy despite having so many neurotology experts doesn't realized that hearing loss and tinnitus are integrally connected. We know that tinnitus is usually caused by auditory damage from external sources such as noise or drugs. Reversing the damage through regenerative treatments would thus also reverse the tinnitus. Yet it appears they are excluding the group that would most be helped by OTO-413, people who are "consistently aware of their tinnitus" all day.
Perhaps if OTO-413 is approved for "hidden" hearing loss, it can nonetheless less be used off-label for tinnitus. It would've been better however seeing them state up front that it's for both tinnitus and hearing loss.
Another note, it would be great to see companies begin trying a treatment that includes both regeneration of the synapses and hair cells. All of the drugs in being studied either focus only on restoring hair cells (FX-322 progenitor cell stimulating small molecule) or regenerating synapses, OTO-413. It seems self evident that doing both would be the most effective. Such an approach is also more likely to get approved as a treatment because it would most likely yield clinically significant improvements.