This study aims to demonstrate that the new medicine AUT00063 is effective and safe in the treatment of tinnitus.

Reduced activity at certain sites in the brain (called "voltage-gated potassium channels") has been linked to hearing problems, like age-related loss of hearing or tinnitus (a 'ringing' or buzzing noise in the ears).

AUT00063 is an experimental new medicine that has been developed to improve the action of these specific channels and so treat the brain component of these hearing problems.

The main purpose of this study is to try to demonstrate an improvement in the severity of tinnitus after 4 weeks of treatment with the study medicine or the placebo (dummy drug which does not contain the medication). Subjects will undergo a safety follow-up after the treatment period.

Safety and efficacy will be determined by looking at a number of assessments (physical examinations, blood sampling, hearing assessments, questionnaires, etc.) and in case of any serious medical event during the study. The amount of drug in the blood will also be measured.

It is expected that up to 152 people with tinnitus may take part in the study. The study participants will be recruited at around 16 Hospital sites in the UK.

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;