A 56-year-old female with schizoaffective disorder managed on paliperidone long-acting injectable presents with involuntary repetitive tongue protrusions, lip smacking, and choreiform finger movements that have progressively worsened over 6 months. Her Abnormal Involuntary Movement Scale (AIMS) total score is 14. The PMHNP diagnoses tardive dyskinesia and initiates deutetrabenazine. Which of the following best describes the mechanism by which deutetrabenazine reduces these involuntary movements?