Valbenazine Treatment of Tardive Dyskinesia in Adults With Intellectual/Developmental Disabilities

The goal of this open-label clinical trial is to test the safety and efficacy of valbenazine treatment in patients with Intellectual/Developmental Disability (IDD) who have a diagnosis of Tardive dyskinesia (TD). The main questions this study aims to answer are:

* Does valbenazine treatment of TD in the previously untreated patient population of adults with IDD produce comparable amelioration of signs of movement disorder as what has historically been reported in adults without IDD?
* Is valbenazine treatment of TD in persons with IDD as safe as what has historically been reported in adults without IDD?
* Does valbenazine treatment improve Quality of Life (QOL) in persons with IDD and TD treated with valbenazine?
* Does valbenazine treatment produce positive change in Activities of Daily Living (ADLs) in persons with IDD and TD?
* Does valbenazine treatment of TD in persons with IDD reduce caregiver burden?

In this study, 25 participants with IDD and TD will undergo valbenazine treatment for 24 weeks. The participants will be seen for a total of 5 visits: at baseline, and at follow up visits at 3 weeks, 6 weeks, 12 weeks, and 24 weeks.

This study does not include a comparison group. Therefore, researchers will compare the response of the study participants to valbenazine treatment with those from a previous reported work that resulted in the FDA approval of this medication.

Tardive dyskinesia (TD) is recognized as a common and often debilitating movement disorder, associated with treatment of a variety of illnesses with dopamine receptor-blocking medications (also commonly known as antipsychotic medications. In addition to the distressing and disfiguring movements of TD, there is now also evidence of a reduced quality of life in patients with TD compared to peers with similar psychiatric disorders without TD.

When originally described, TD had been thought to be primarily associated with use of First-Generation Antipsychotics (FGA's, also known as typical antipsychotics), but there are now good studies to suggest that TD is also frequently a result of exposure to Second Generation Antipsychotics (SGA's) as well. Valbenazine, a selective vesicular monoamine transporter 2 inhibitor, is now available to treat the symptoms of TD, with a favorable efficacy and safety profile. This medication offers, for the first time, a treatment option for patients - as well as their caregivers and families - suffering with TD.

Individuals with intellectual and developmental disabilities (IDD) commonly suffer from co-occurring psychiatric and/or behavioral disorders (informally known as a "dual diagnosis"). Such individuals are commonly prescribed antipsychotic medications to treat these co-occurring disorders. Several authors have noted that antipsychotic medications have frequently been over-prescribed for individuals with IDD, often in the absence of an identified psychotic illness. Some studies have shown that up to 20-30% of adults with IDD are prescribed antipsychotic medications across a variety of residential settings.

Surrounding this frequent use of antipsychotic medications in persons with IDD, it is now well-established that persons and that having intellectual disability is a recognized risk factor for developing TD when treated with antipsychotic medications. Finally, recent research has confirmed the long-suspected belief that persons with IDD are MORE susceptible to movement disorder side effects when treated with antipsychotic medications when compared to persons without IDD.

Based on their increased exposure to antipsychotics, and increased susceptibility to movement disorders including TD, it would seem that persons with IDD who have TD are a group who could benefit most from treatment with a novel agent which can address this movement disorder.

Before TD can be treated, it must be clinically identified and formally diagnosed. Once diagnosed, patients and families must be educated on the availability of treatment options, outcomes when no treatment is undertaken, and the potential benefits (and risks) of treatment itself.

Movement disorders such as TD have been diagnosed on the basis of clinical examination, often using formal assessment tools to identify and quantify the movement abnormalities seen. One such instrument is the Abnormal Involuntary Movement Scale (AIMS). The AIMS has been used for many years as the gold standard for this purpose. In addition, there have been recent attempts to quantify the amount of improvement (change in movement intensity, and reduction in AIMS scores) that are considered clinically significant in rating improvement. Additionally, a number of authors have noted the difficulty in using the AIMS in persons with IDD who cannot cooperate fully in the examination process. For this reason, some have suggested using videotaped AIMS exams as a methodology for more accurately quantifying change. Videotaping of exams pre- and post-treatment for blind rating of improvement has been a methodology utilized in a number of recent studies of valbenazine.

In this study, 25 participants with IDD and TD will undergo valbenazine treatment for 24 weeks. The participants will be seen for a total of 5 visits: at baseline, and at follow up visits at 3 weeks, 6 weeks, 12 weeks, and 24 weeks. Consented participants will have an AIMS administered and videotaped at each visit, initially to identify and quantify TD, and subsequently to measure possible response to valbenazine. Subjects' TD response to valbenazine will also be assessed using the Clinical Global Impression of Change (CGI-C) scale (by investigator) and Caregiver Global Impression Scale (by proxy caregiver). Subjects' quality of life will be assessed with the World Health Organization Quality of Life Scale- For Persons with Disability (WHOQOL-DIS), a proxy-reported instrument designed for individuals with IDD, before and after valbenazine treatment. Participants' behavior will be assessed with the Aberrant Behavior Checklist-Irritability Subscale, before and after valbenazine treatment. Subjects' Activities of Daily Living (ADL's) will be assessed with the Waisman Activities of Daily Living Scale (W-ADL), a proxy-reported instrument designed for individuals with IDD and other disabilities, before and after valbenazine treatment. Caregiver burden will be assessed with the Zarit Burden Inventory, short version, before and after valbenazine treatment.

Eligibility Criteria:
Inclusion Criteria:

* Diagnosis of IDD (IQ \< 70; social/adaptive dysfunction, onset \< age 22) as per DSM-5
* Clinical diagnosis of Tardive Dyskinesia (TD) per DSM-5 for at least 3 months before study inclusion (presence of movement disorder for at least 3 months, in absence of previous formal diagnosis of TD).
* Eligible to receive valbenazine according to current product labeling.
* Stable doses of all psychotropic medications for minimum of three months before study inclusion.
* Willing to remain on stable doses of all psychotropics for 24 weeks of study. If female of childbearing age, practicing acceptable form for birth control throughout study duration.
* Subject able to comply with scheduled visits and assessments.
* Consent of subject, or legally authorized representative to study protocol.

Exclusion Criteria:

* Previous treatment with a VMAT2 inhibitor (tetrabenazine, valbenazine, or deutetrabenazine).
* Treatment with any investigational drug in the 30 days prior to study entry.
* Currently taking a strong CYP3A4 inducer such as carbamazepine, phenobarbital, diphenylhydantoin, or primidone.
* Any unstable medical condition in the 60 days prior to study entry.
* Pregnant or breast-feeding.
* Inability to take study medication.
* History of neuroleptic malignant syndrome.
* History of long QTc on electrocardiogram, bundle branch block (BBB), atrioventricular block, serious cardiac arrhythmia, or heart failure.
* QTc on EKG \> 450 msec (Fredericia formula) on EKG within 3 months prior to study entry.
* History of substance abuse or dependence in the 3 months prior to study entry.
* Significant risk of suicide or dangerous aggression to others at time of or 3 months prior to study entry.