Evaluating Possible Improvement in Tinnitus Severity After 28 Days Dosing of the Study Drug AUT00063 Compared to Placebo

Inclusion Criteria: * English-speaking, who are UK residents registered with a UK General Practitioner; * Experiencing stable tinnitus (consistent from day to day) * Tinnitus has existed for not less than 6 months, and not more than 18 months - Contraceptive methods must be used before and for at least 30 days after the stop of the study treatment. Exclusion Criteria: * Severe hearing impairment such that verbal communication is unreliable; * History of important cardiac, endocrine, pulmonary, neurologic, psychiatric, hepatic, renal, hematologic, immunologic, or other major diseases deemed clinically significant at the time of the study by the Investigator and which might be jeopardised by entering the study; * Moderate or severe depression or generalised anxiety * Participation in any clinical research study evaluating another investigational drug or therapy within 30 days of starting the investigational treatment * Participation in hearing study, involving an intervention, within 3 months from last study visit; * Central nervous system pathologies e.g. Multiple Sclerosis, Parkinson's disease; * Tinnitus as a concomitant symptom of a known otological condition (including but not limited to otitis externa, otitis media, otosclerosis, cholesteatoma, Ménière's disease or other vestibular problems, acoustic neuroma, or temporo-mandibular joint disorder); * Pulsatile tinnitus (rhythmical sounds that often beat in time with the heartbeat); * Intermittent tinnitus (comes and goes from one day to the next); * Surgery or medical condition that might would be expected to significantly affect absorption of medicines;