I will start by saying that I hope I am wrong, but ...
I've followed Hough for a few years now, and if you believe their web site, they have been on the verge of curing hearing loss for years. They just need a few hundred thousand dollars because their federal funding has fallen by 85%. Seems likely that if they could demonstrate that they were on the verge of a major breakthrough, their funding would not have fallen that much. Research funding in the US has fallen generally, but other labs working on similar ideas have not seen drops like that. Additionally, Otologic attracted $4 million with the start of their trial. Since then, there is no evidence of additional funding, but Decibel and Frequency have attracted something like 80 million dollars. (I've written more about Hough elsewhere which a search would surely find.)
The trial alluded to above was a Phase I trial that was completed in 2015 (
https://clinicaltrials.gov/ct2/show/NCT02259595), but there hasn't been an announcement of a Phase II study in the last 2 1/2 years or any publications on the safety of the drug (NAC + HPN-07). They are, however, continuing to do animal studies:
https://www.ncbi.nlm.nih.gov/pubmed/28438658
I've contacted them in the past asking about new papers or evidence of their claims, and they have not responded. Hopefully they are where they say they are, but in the absence of significant publications their "announcements" sound like fundraising pitches to me.