I get that they're trying to limit the study to noise induced tinnitus but audiogram is a really crap way to diagnose tinnitus.
From their website:
A. The study requires subjects to have a small (>20dB) hearing loss at one or more frequencies from 0.5kHz up to 8kHz; this is a minimal loss and most tinnitus sufferers will have this.
So if you have hearing loss at frequency they won't test for you can't get into the trial. If you have hearing loss at 8500 hz you still can't get in the trial. If you are subject to an acoustic trauma with a temporary threshold shift, and your hearing comes back but tinnitus remains (quite common) you can't participate in the study.
Also from their website:
Q. Can a subject with hearing loss in only 1 ear still take part?
A. This will depend upon how large is the difference from one ear to the other; this will be checked by the audiologist before entry into the study.
If you have a firecracker popping next to one of your hears or someone yelled in your left ear, well guess what? You won't be able to participate either.
Given that audiograms are really poor indicators of anything tinnitus related I do not know why they chose these criteria. Seems like not much thought was put into that one.
With the following statement in mind:
Q. If I also suffer from hearing loss, can I expect to see an improvement in my audiogram, as I know AUT00063 is being tested also for Age Related Hearing Loss in the USA
A. No, we do not expect AUT00063 to improve the pure tone audiogram as the drug does not work on mechanisms is the cochlea itself. "063" is designed to improve auditory processing in the brain, and of course to reduce the central auditory activity that gives rise to tinnitus. A decline in central auditory processing is an important aspect of age related hearing loss, and gives rise to the difficult people have understanding speech in difficult listening environments, such as in a background of noise. In preclinical models, AUT00063 has been shown to improve central auditory processing.
Why bother with pure tone audiogram requirements if their drug won't even affect that? No idea.