Tetrabenazine has been known since the late 1950’s to be a potent and selective depletor of monoamines from neurons in the central nervous system (CNS). The mechanism of action of tetrabenazine involves inhibition of vesicular monoamine transporter 2 (VMAT2), one of the principal brain synaptic vesicular monoamine transporters. VMAT2 is one of the two VMAT isoforms and expressed nearly exclusively in the brain, whereas the VMAT1 isoform is expressed in peripheral tissues. The potent and selective binding of tetrabenazine to VMAT2 as seen in the laboratory studies helps to explain why its dopamine-depleting effects are seen in the CNS but not in the peripheral neurons. We have been granted exclusive rights from Cambridge Laboratories (Ireland) Limited to develop and commercialize tetrabenazine in the U.S. and Canada.

Tetrabenazine is an investigational drug in the U.S. We conducted pivotal trials in the United States and have filed a New Drug Application (NDA) with the U.S. Food and Drug Administration (FDA) for tetrabenazine as a treatment for chorea associated with Huntington’s disease. The FDA has granted tetrabenazine orphan drug designations for Huntington’s disease and for moderate to severe tardive dyskinesia. The product also has been granted a fast track designation as a treatment for chorea associated with Huntington’s disease.

Tetrabenazine is currently approved in 10 countries outside of the U.S. Tetrabenazine has been commercially available in a number of European countries for over 35 years and in Canada for over 10 years. In the United States, tetrabenazine is an investigational drug.