This is a 2-part study of OTO-104 in subjects with unilateral Meniere's disease in the United Kingdom. The first part is a randomized, placebo-controlled study comparing the safety profile of 2 injections of OTO-104 or placebo spaced 3 months apart. The second part is an open-label extension where all subjects will receive an additional 2 intratympanic injections of OTO-104 spaced 3 months apart. Each subject will participate on the study for a total of 1 year.

Inclusion Criteria includes, but is not limited to:

• Subject has a diagnosis of definite unilateral Meniere's disease.
• Subject agrees to maintain their current standard of care treatments for Meniere's disease while on-study.

Exclusion Criteria includes, but is not limited to:

• Subject is pregnant or lactating.
• Subject has a history of immunodeficiency disease.
• Subject has a history of previous endolymphatic sac surgery.
• Subject has a history of previous use of intratympanic gentamicin in the affected ear.
• Subject has a history of drop attacks.
• Subject has experienced an adverse reaction to intratympanic injection of steroids.