Valbenazine, approved for tardive dyskinesia, exerts its therapeutic effect through which molecular mechanism?

• A Partial agonism at dopamine D2 receptors
• B Reversible inhibition of vesicular monoamine transporter 2 (VMAT2) ✓
• C Irreversible inhibition of monoamine oxidase B
• D Antagonism of dopamine D3 receptors selectively

Explanation

Valbenazine is a reversible, highly selective VMAT2 inhibitor that depletes presynaptic dopamine stores, reducing involuntary movements of tardive dyskinesia without causing the depression seen with older irreversible depletors like reserpine. Deutetrabenazine shares this mechanism. Partial D2 agonism describes aripiprazole, and selective D3 antagonism is not an established anti-dyskinetic strategy, eliminating options A and D.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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