VMAT2 inhibitors for the treatment of hyperkinetic movement disorders

Risk of VMAT2 inhibitors on suicidality and parkinsonism: report utilizing the United States Food and Drug Administration adverse event reporting system

Prescription of vesicular monoamine transporter 2 (VMAT2) inhibitors, valbenazine, deutetrabenazine, and tetrabenazine, is becoming increasingly common in persons treated with antipsychotics. Reported suicidality and parkinsonism are safety concerns with VMAT2 inhibitors. Herein, we aim to evaluate the aforementioned safety outcomes using the FDA Adverse Event Reporting System. Reporting odds ratios (RORs) and lower limits of 95% confidence intervals of information components (IC 025 ) were calculated to quantify VMAT2 inhibitor-associated adverse events. Acetaminophen was the reference agent. Suicidal ideation was significantly associated with VMAT2 inhibitors, with RORs ranging from 2.38 to 10.67 and IC 025 ranging from 0.73 to 2.39. Increased odds of suicidal behavior was observed with tetrabenazine (ROR 3.011, IC 025 0.0087), but not deutetrabenazine or valbenazine. Decreased odds of suicide attempts and completed suicide were observed with VMAT2 inhibitors, with RORs ranging from 0.011 to 0.10 (all IC 025  < 0). Increased odds of parkinsonism were reported for all VMAT2 inhibitors, with RORs and IC 025 ranging from 19.49 to 25.37 and 1.66 to 2.93, respectively. The mixed results with VMAT2 inhibitor-associated suicidality and parkinsonism do not establish causal relationships. The parameters of suicidality may be explained by underlying psychiatric disorders.

Sex-specific attenuation of photoreceptor degeneration by reserpine in a rhodopsin P23H rat model of autosomal dominant retinitis pigmentosa

Inherited retinal degenerations (IRDs) constitute a group of clinically and genetically diverse vision-impairing disorders. Retinitis pigmentosa (RP), the most common form of IRD, is characterized by gradual dysfunction and degeneration of rod photoreceptors, followed by the loss of cone photoreceptors. Recently, we identified reserpine as a lead molecule for maintaining rod survival in mouse and human retinal organoids as well as in the rd16 mouse, which phenocopy Leber congenital amaurosis caused by mutations in the cilia-centrosomal gene CEP290 (Chen et al., 2023). Here, we show the therapeutic potential of reserpine in a rhodopsin P23H rat model of autosomal dominant RP. At postnatal day (P) 68, when males and females are analyzed together, the reserpine-treated rats exhibit higher rod-derived scotopic b-wave amplitudes compared to the controls with little or no change in scotopic a-wave or cone-derived photopic b-wave. Interestingly, the reserpine-treated female rats display enhanced scotopic a- and b-waves and photopic b-wave responses at P68, along with a better contrast threshold and increased outer nuclear layer thickness. The female rats demonstrate better preservation of both rod and cone photoreceptors following reserpine treatment. Retinal transcriptome analysis reveals sex-specific responses to reserpine, with significant upregulation of phototransduction genes and proteostasis-related pathways, and notably, genes associated with stress response. This study builds upon our previously reported results reaffirming the potential of reserpine for gene-agnostic treatment of IRDs and emphasizes the importance of biological sex in retinal disease research and therapy development.

PYK2 in the dorsal striatum of Huntington's disease R6/2 mouse model

Huntington's disease (HD) is a devastating disease due to autosomal dominant mutation in the HTT gene. Its pathophysiology involves multiple molecular alterations including transcriptional defects. We previously showed that in HD patients and mouse model, the protein levels of the non-receptor tyrosine kinase PYK2 were decreased in the hippocampus and that viral expression of PYK2 improved the hippocampal phenotype. Here, we investigated the possible contribution of PYK2 in the striatum, a brain region particularly altered in HD. PYK2 mRNA levels were decreased in the striatum and hippocampus of R6/2 mice, a severe HD model. Striatal PYK2 protein levels were also decreased in R6/2 mice and human patients. PYK2 knockout by itself did not result in motor symptoms observed in HD mouse models. We examined whether PYK2 deficiency participated in the R6/2 mice phenotype by expressing PYK2 in their dorsal striatum using AAV vectors. With an AAV1/Camk2a promoter, we did not observe significant improvement of body weight, clasping, motor activity and coordination (rotarod) alterations observed in R6/2 mice. With an AAV9/SYN1 promoter we found a slightly higher body weight and a trend to better rotarod performance. Both viruses similarly transduced striatal projection neurons and somatostatin-positive interneurons but only AAV9/SYN1 led to PYK2 expression in cholinergic and parvalbumin-positive interneurons. Expression of PYK2 in cholinergic interneurons may contribute to the slight effects observed. We conclude that PYK2 mRNA and protein levels are decreased in the striatum as in hippocampus of HD patients and mouse models. However, in contrast to hippocampus, striatal viral expression of PYK2 has only a minor effect on the R6/2 model striatal phenotype.

Real-world safety analysis of deutetrabenazine post-marketing: a disproportionality study leveraging the FDA Adverse Event Reporting System (FAERS) database

BACKGROUND

Deutetrabenazine, a selective vesicular monoamine transporter type 2 (VMAT2) inhibitor, has been demonstrated efficacy in treating refractory neurologic disorders such as Tardive Dyskinesia (TD) and Huntington's disease but have potential adverse events (AEs) that require detailed pharmacovigilance. This study aimed to comprehensively assess the safety profile of deutetrabenazine in real-world settings by analyzing AEs reported from the FDA Adverse Event Reporting System (FAERS) database.

METHODS

We conducted a retrospective pharmacovigilance study using FAERS data from Q3 2017 to Q3 2024, focusing on deutetrabenazine-related AEs. We applied four disproportionality analysis methods-Reporting Odds Ratio (ROR), Proportional Reporting Ratio (PRR), Bayesian Confidence Propagation Neural Network (BCPNN) and Multinomial Gamma Poisson Shrinkage (MGPS)--to identify potential safety signals. Furthermore, we utilized the Weibull distribution model to analyze the temporal risk of AEs.

RESULTS

Among the 10,571,578 reports obtained from the FAERS database, 4,337 AE reports were associated with deutetrabenazine. Using four independent computational methods at the preferred term (PT) level, we identified 1,131 PTs that indicated noteworthy adverse reactions. The drug's label-listed adverse reactions, including depression, somnolence, suicidal ideation, and fatigue, showed remarkable signals. Furthermore, we detected potential adverse reactions that were not specified on the label, such as drug ineffectiveness, dyskinesia, death, falls, and insomnia. The majority of these AEs were reported within the initial month of deutetrabenazine treatment, with a median time to onset of 40.5 days.

CONCLUSION

This research has yielded initial safety insights into the practical use of deutetrabenazine, validating established adverse reactions and uncovering further possible risks. These findings present essential safety considerations for physicians when prescribing deutetrabenazine for the clinical treatment.

Electrophysiological Alterations in the Progression of Parkinson's Disease and the Therapeutic Effect of Tetrabenazine on Rats With Levodopa-Induced Dyskinesia

AIMS

Dopamine replacement therapy is the backbone of Parkinson's disease (PD) treatment. However, long-term levodopa (L-DOPA) administration can lead to the severely disabling motor complication L-DOPA-induced dyskinesia (LID), for which standard, effective therapy is currently lacking. This study was conducted to characterize the distinct neural electrophysiological patterns involved in the progression of PD and to examine the efficacy of tetrabenazine, a vesicular monoamine transporter-2 inhibitor, in alleviating dyskinesia and its underlying electrophysiological mechanism.

METHODS

Electrophysiological analysis was performed to obtain power spectrum density and functional connectivity information from local field potential (LFP) data recorded from the primary motor cortex (M1) and dorsolateral striatum (DLS) during different pathological states in PD model rats. Behavioral tests and abnormal involuntary movements (AIMs) scoring were conducted to confirm PD model establishment and assess LID severity.

RESULTS

Increased beta oscillations and abnormally strengthened beta causality in the M1 → DLS direction and exaggerated beta-band M1-DLS functional connectivity were observed in the PD state. L-DOPA administration suppressed beta activity and augmented gamma power in the M1 and DLS, with increased gamma causality in the M1 → DLS direction and beta causality in the DLS → M1 direction, as well as elevated gamma-band M1-DLS functional connectivity. Tetrabenazine strongly ameliorated dyskinetic manifestations. It suppressed gamma power in the M1 and DLS, reduced gamma causality and increased beta causality in the M1 → DLS direction, reduced beta causality in the DLS → M1 direction, and reduced gamma-band M1-DLS functional connectivity.

CONCLUSION

Tetrabenazine abrogated aberrant gamma activity to improve LID symptoms, which provides compelling evidence for its future clinical application in LID therapy.

Structural insights into substrate transport and drug inhibition of the human vesicular monoamine transporter 2 (VMAT2)

Vesicular monoamine transporter 2 (VMAT2) is a proton-monoamine antiporter that is widely expressed in central and peripheral neurons and plays a crucial role in loading monoamine neurotransmitters into secretory vesicles. Dysfunction of VMAT2 causes many neuropsychiatric disorders, such as depression and Parkinson's disease. Consequently, VMAT2 is a valid and important therapeutic target. Reserpine alleviates symptoms of hypertension via potent inhibition of VMAT2. Tetrabenazine selectively inhibits VMAT2 and has been used for the management of chorea, including Huntington's disease. Decades of extensive studies have defined the substrate specificity and transport kinetics of VMAT2. However, the structure and precise mechanisms of monoamine recognition and drug inhibition in VMAT2 remain unknown. Recently, we determined an ensemble of high-resolution cryo-EM structures of human VMAT2 in three distinct states bound to multiple substrates and inhibitors. These results lay a structural foundation for a comprehensive understanding of substrate recognition and transport, drug inhibition, and proton coupling in VMAT2 and shed light on future therapeutic development.

An update on the pharmacological management of Tourette syndrome and emerging treatment paradigms

INTRODUCTION

Tourette syndrome (TS) is a childhood-onset neurobehavioral disorder characterized by tics. Pharmacotherapy is advised for patients whose symptoms affect their quality of life.

AREAS COVERED

The authors review the tic phenomenology and TS diagnostic criteria. The bulk of this article focuses on pharmacotherapeutic options for treating tics. They also highlight pharmacotherapies in the research pipeline.

EXPERT OPINION

Tic treatment must be tailored to individual needs. Behavioral therapy is the first line of treatment. Most with bothersome tics need pharmacotherapy and rarely, for medication-refractory cases, surgical therapy is indicated. Alpha-2 agonists are considered in patients with mild tics, especially in those with attention deficit with or without hyperactivity. Second-generation antipsychotics like aripiprazole and tiapride may be considered for severe tics. However, prescribers should be mindful of potential side effects, especially drug-induced movement disorders. Botulinum toxin injections may be considered for focal motor tics. Topiramate can be considered when other treatments are ineffective, and its benefits outweigh the risks. The same holds true for vesicular monoamine transporter-2 inhibitors, as they are deemed to be safe and effective in real-world use and open-label trials despite not meeting primary endpoints in placebo-controlled trials. Cannabinoids may be considered in adults if the approaches above do not control tics.

Native State Stabilization of Amyloidogenic Proteins by Kinetic Stabilizers: Inhibition of Protein Aggregation and Clinical Relevance

Proteinopathies or amyloidoses are a group of life-threatening disorders that result from misfolding of proteins and aggregation into toxic insoluble amyloid aggregates. Amyloid aggregates have low clearance from the body due to the insoluble nature, leading to their deposition in various organs and consequent organ dysfunction. While amyloid deposition in the central nervous system leads to neurodegenerative diseases that mostly cause dementia and difficulty in movement, several other organs, including heart, liver and kidney are also affected by systemic amyloidoses. Regardless of the site of amyloid deposition, misfolding and structural alteration of the precursor proteins play the central role in amyloid formation. Kinetic stabilizers are an emerging class of drugs, which act like pharmacological chaperones to stabilize the native state structure of amyloidogenic proteins and to increase the activation energy barrier that is required for adopting a misfolded structure or conformation, ultimately leading to the inhibition of protein aggregation. In this review, we discuss the kinetic stabilizers that stabilize the native quaternary structure of transthyretin, immunoglobulin light chain and superoxide dismutase 1 that cause transthyretin amyloidoses, light chain amyloidosis and familial amyotrophic lateral sclerosis, respectively.

2024 FDA-approved psychotropic medications: A conspectus

As of August 2024, (US) FDA has granted approval for a number of psychotropic drugs on market that might usher an innovative sparkle in psychopharmacotherapy. This is a recap to update busy clinicians.

Profiling deutetrabenazine extended-release tablets for tardive dyskinesia and chorea associated with Huntington's disease

INTRODUCTION

Tardive dyskinesia (TD) and Huntington's disease (HD)-associated chorea are persistent and disabling hyperkinetic disorders that can be treated with vesicular monoamine transporter type 2 (VMAT2) inhibitors, including the recently approved once-daily (QD) formulation of deutetrabenazine (DTBZ ER). While its efficacy and safety profile have not been directly investigated, currently available data confirms bioequivalence and similar bioavailability to the twice-daily formulation (DTBZ BID).

AREAS COVERED

The authors briefly review the pivotal trials establishing efficacy of DTBZ for TD and HD-associated chorea, the pharmacokinetic data for bioequivalence between QD and BID dosing of DTBZ, as well as dose proportionality evidence, titration recommendations, and safety profile for DTBZ ER.

EXPERT OPINION

Long-term data show that DTBZ is efficacious and well tolerated for the treatment of TD and HD-associated chorea. DTBZ ER likely demonstrates therapeutic equivalence with no new safety signals. Due to the lack of comparative clinical trial data, no evidence-based recommendation about choice of VMAT2 inhibitor or switching between VMAT2 inhibitors can be made about best practice. Ultimately, QD dosing may offer the chance of improved medication adherence, an important consideration in patients with complex treatment regimens and/or patients with cognitive decline.

Modulating amacrine cell-derived dopamine signaling promotes optic nerve regeneration and preserves visual function

As part of the central nervous system, the optic nerve, composed of axons from retinal ganglion cells (RGCs), generally fails to regenerate on its own when injured in adult mammals. An innovative approach to promoting optic nerve regeneration involves manipulating the interactions between amacrine cells (ACs) and RGCs. Here, we identified a unique AC subtype, dopaminergic ACs (DACs), that responded early after optic nerve crush by down-regulating neuronal activity and reducing retinal dopamine (DA) release. Activating DACs or augmenting DA release with levodopa demonstrated neuroprotective effects and modestly enhanced axon regeneration. Within this context, we pinpointed the DA receptor D1 (DRD1) as a critical mediator of DAC-derived DA and showed that RGC-specific Drd1 overexpression effectively overcame subtype-specific barriers to regeneration. This strategy markedly boosted RGC survival and axon regeneration after crush and preserved vision in a glaucoma model. This study unveils the crucial role of DAC-derived DA signaling in optic nerve regeneration, holding promise for therapeutic insights into neural repair.

Real-world experience with Deutetrabenazine management in patients with Huntington's disease using video-based telemedicine

BACKGROUND

Huntington's disease (HD) is a rare progressive neurological disorder, and telemedicine has the potential to improve the quality of care for patients with HD. Deutetrabenazine (DTBZ) can reduce chorea symptoms in HD; however, there is limited experience with this medication in Asian countries.

METHODS

Retrospective and prospective studies were employed to explore the feasibility and reliability of a video-based telemedicine system for HD patient care. Reliability was demonstrated through consistency between selected-item scores (SIS) and total motor scores (TMS) and the agreement of scores obtained from hospital and home videos. Finally, a single-centre real-world DTBZ management study was conducted based on the telemedicine system to explore the efficacy of DTBZ in patients with HD.

RESULTS

There were 77 patients included in the retrospective study, and a strong correlation was found between SIS and TMS (r = 0.911, P < 0.0001), indicating good representativeness. There were 32 patients enrolled in the prospective study. The reliability was further confirmed, indicated by correlations between SIS and TMS (r = 0.964, P < 0.0001) and consistency of SIS derived from the in-person and virtual visits (r = 0.969, P < 0.0001). There were 17 patients included in the DTBZ study with a mean 1.41 (95% confidence interval, 0.37-2.46) improvement in chorea score and reported treatment success.

CONCLUSIONS

A video-based telemedicine system is a feasible and reliable option for HD patient care. It may also be used for drug management as a supplementary tool for clinical visits.

Comparative Analysis of Deutetrabenazine and Valbenazine as VMAT2 Inhibitors for Tardive Dyskinesia: A Systematic Review

Background

Tardive Dyskinesia (TD) is a neurological disorder characterized by involuntary movements, often caused by dopamine receptor antagonists. Vesicular Monoamine Transporter 2 (VMAT2) inhibitors, such as valbenazine and deutetrabenazine, have emerged as promising therapies for TD and several clinical trials have shown their efficacy. This study aims to compare the efficacy and safety profile of VMAT2 inhibitors, focusing on a recent trial conducted in the Asian population.

Methods

We reviewed the PubMed, Cochrane Library, Embase database, and clinicaltrials.gov between January 2017 and October 2023, using the keywords "tardive dyskinesia" AND ("valbenazine" [all fields] OR " deutetrabenazine " [all fields]) AND "clinical trial". The reviewed articles were studied for efficacy and side effects.

Results

An initial search yielded 230 articles, of which 104 were duplicates. Following the title and abstract screening, 25 additional articles were excluded. A full-text review resulted in the exclusion of 96 more articles. Ultimately, four double-blind clinical trials met the inclusion criteria. The deutetrabenazine studies demonstrated significant improvements in Abnormal Involuntary Movement Scale (AIMS) scores compared to placebo, with no difference in adverse events. The valbenazine studies showed favorable results in reducing TD symptoms and were well-tolerated.

Discussion

The studies reviewed in this analysis underscore the potential of deutetrabenazine and valbenazine as valuable treatment options for TD in diverse populations. Both medications demonstrated significant improvements in AIMS scores, suggesting their effectiveness in managing TD symptoms. Additionally, they exhibited favorable safety profiles, with low rates of serious adverse events and no significant increase in QT prolongation, parkinsonism, suicidal ideation, or mortality.

Conclusion

The studies reviewed highlight the promising efficacy and tolerability of deutetrabenazine and valbenazine as treatments for Tardive Dyskinesia, providing new hope for individuals affected by this challenging condition.

Vesicular monoamine transporter (VMAT) regional expression and roles in pathological conditions

Vesicular monoamine transporters (VMATs) are key regulators of neurotransmitter release responsible for controlling numerous physiological, cognitive, emotional, and behavioral functions. They represent important therapeutic targets for numerous pathological conditions. There are two isoforms of VMAT transporter proteins that function as secondary active transporters into the vesicle for storage and release via exocytosis: VMAT1 (SLC18A1) and VMAT2 (SLC18A2) which differ in their function, quantity, and regional expression. VMAT2 has gained considerable interest as a therapeutic target and diagnostic marker. Inhibitors of VMAT2 have been used as an effective therapy for a range of pathological conditions. Additionally, the functionality and phenotypic classification of classical and nonclassical catecholaminergic neurons are identified by the presence of VMAT2 in catecholaminergic neurons. Dysregulation of VMAT2 is also implicated in many neuropsychiatric diseases. Despite the complex role of VMAT2, many aspects of its function remain unclear. Therefore, our aim is to expand our knowledge of the role of VMAT with a special focus on VMAT2 in different systems and cellular pathways which may potentially facilitate development of novel, more specific therapeutic targets. The current review provides a summary demonstrating the mechanism of action of VMAT, its functional role, and its contribution to disease progression and utilization as therapeutic targets.

Huntington's Disease Drug Development: A Phase 3 Pipeline Analysis

Huntington's Disease (HD) is a severely debilitating neurodegenerative disorder in which sufferers exhibit different combinations of movement disorders, dementia, and behavioral or psychiatric abnormalities. The disorder is a result of a trinucleotide repeat expansion mutation that is inherited in an autosomal dominant manner. While there is currently no treatment to alter the course of HD, there are medications that lessen abnormal movement and psychiatric symptoms. ClinicalTrials.gov was searched to identify drugs that are currently in or have completed phase III drug trials for the treatment of HD. The described phase III trials were further limited to interventional studies that were recruiting, active not recruiting, or completed. In addition, all studies must have posted an update within the past year. PubMed was used to gather further information on these interventional studies. Of the nine clinical trials that met these criteria, eight involved the following drugs: metformin, dextromethorphan/quinidine, deutetrabenazine, valbenazine, Cellavita HD, pridopidine, SAGE-718, and RO7234292 (RG6042). Of these drug treatments, four are already FDA approved. This systematic review provides a resource that summarizes the present therapies for treating this devastating condition that are currently in phase III clinical trials in the United States.

Real-world experience with VMAT2 inhibitors in Tourette syndrome

OBJECTIVES

We aimed to review our "real-world" experience with the vesicular monoamine transporter 2 (VMAT2) inhibitors tetrabenazine, deutetrabenazine, and valbenazine for treatment of Tourette syndrome, focusing on therapeutic benefits, side effect profile, and accessibility for the off-label use of these drugs.

METHODS

We performed a retrospective chart review, supplemented with a telephone survey, of all our patients treated for their tics with VMAT2 inhibitors over a period of 4 years from January 2017 until January 2021.

RESULTS

We identified 164 patients treated with the various VMAT2 inhibitors (tetrabenazine, n = 135; deutetrabenazine, n = 71; valbenazine, n = 20). Data on the mean treatment duration and daily dosages were collected. The response to VMAT2 inhibitors was assessed by a Likert scale by comparing the symptom severity before initiation and while on treatment. Side effects were mild and mostly consisted of depression as the major side effect but there was no suicidality reported.

CONCLUSION

VMAT2 inhibitors are effective and safe in the treatment of tics associated with Tourette syndrome but are not readily accessible by patients in the United States, partly because of lack of approval by the Food and Drug Administration.

Movement disorders associated with substance use in adults living in precarious housing or homelessness

OBJECTIVE

Many individuals living in precarious housing or homelessness have multimorbid illnesses, including substance use, psychiatric, and neurological disorders. Movement disorders (MDs) associated substance use are amongst the poorly studied subtopics of drug-induced MDs. The aim of the present study was, therefore, to determine the proportion affected and severity of different signs of MDs, as well as their associations with substance use in a community-based sample of precariously housed and homeless individuals.

METHODS

Participants were recruited from an impoverished urban neighborhood and were assessed for substance dependence and self-reported substance use (alcohol, cannabis, cocaine, methamphetamine, nicotine, and opioids), as well as for the severity of signs of MDs (akathisia, dyskinesia, dystonia, and parkinsonism). Adjusted regression models were used to estimate the associations of the severity of signs with the frequency of substance use over the past 4 weeks and with the baseline diagnosis of substance dependence.

RESULTS

The proportion of the sample with clinically relevant signs of MDs in any of the four categories was 18.6% (n = 401), and these participants demonstrated lower levels of functioning than those without signs. Of the different types of substance use, only methamphetamine (its frequency of use and dependence) was significantly associated with greater severity of overall signs of MDs. Frequency of methamphetamine use significantly interacted with age and sex, whereby older female participants exhibited the greatest overall severity with increased methamphetamine use. Of the different signs of MDs, methamphetamine use frequency was positively associated with the severity of trunk/limb dyskinesia and hypokinetic parkinsonism. Relative to no use, concurrent use of antipsychotics demonstrated lower severity of trunk/limb dyskinesia and greater severity of hypokinetic parkinsonism with methamphetamine use, and greater severity of dystonia with cocaine use.

CONCLUSIONS

Our study found a high proportion of MDs in a relatively young sample, and their severity was consistently associated with methamphetamine use, moderated by participant demographics and antipsychotic use. These disabling sequelae represent an important and understudied neurological condition that may affect quality of life and will require further study.

Inhibition of VMAT2 by β2-adrenergic agonists, antagonists, and the atypical antipsychotic ziprasidone

Vesicular monoamine transporter 2 (VMAT2) is responsible for packing monoamine neurotransmitters into synaptic vesicles for storage and subsequent neurotransmission. VMAT2 inhibitors are approved for symptomatic treatment of tardive dyskinesia and Huntington's chorea, but despite being much-studied inhibitors their exact binding site and mechanism behind binding and inhibition of monoamine transport are not known. Here we report the identification of several approved drugs, notably β2-adrenergic agonists salmeterol, vilanterol and formoterol, β2-adrenergic antagonist carvedilol and the atypical antipsychotic ziprasidone as inhibitors of rat VMAT2. Further, plausible binding modes of the established VMAT2 inhibitors reserpine and tetrabenazine and hit compounds salmeterol and ziprasidone were identified using molecular dynamics simulations and functional assays using VMAT2 wild-type and mutants. Our findings show VMAT2 as a potential off-target of treatments with several approved drugs in use today and can also provide important first steps in both drug repurposing and therapy development targeting VMAT2 function.

Long-Term Deutetrabenazine Treatment for Tardive Dyskinesia Is Associated With Sustained Benefits and Safety: A 3-Year, Open-Label Extension Study

Background

Deutetrabenazine is a vesicular monoamine transporter 2 inhibitor approved for the treatment of tardive dyskinesia (TD) in adults. In two 12-week pivotal studies, deutetrabenazine demonstrated statistically significant improvements in Abnormal Involuntary Movement Scale (AIMS) scores, with favorable safety/tolerability in TD patients. This study reports long-term efficacy and safety of deutetrabenazine in a 3-year, single-arm, open-label extension (OLE) study.

Methods

Patients who completed the pivotal studies could enroll in this single-arm OLE study, titrating up to 48 mg/day based on dyskinesia control and tolerability. Efficacy was assessed based on change from baseline in total motor AIMS score, Clinical Global Impression of Change (CGIC) and Patient Global Impression of Change (PGIC), and quality of life (QOL) assessments. Safety evaluation included adverse event (AE) incidence, reported using exposure-adjusted incidence rates, and safety scales.

Results

343 patients enrolled in the study (6 patients were excluded). At Week 145 (mean dose: 39.4 ± 0.83 mg/day), mean ± SE change from baseline in total motor AIMS score was -6.6 ± 0.37 and 67% of patients achieved ≥50% improvement in total motor AIMS score. Based on CGIC and PGIC, 73% and 63% of patients achieved treatment success, respectively. QOL improvements were also observed. Deutetrabenazine was generally well tolerated, with low rates of mild-to-moderate AEs and no new safety signals; most safety scales remained unchanged over time.

Conclusions

Long-term deutetrabenazine treatment was associated with sustained improvement in AIMS scores, indicative of clinically meaningful long-term benefit, and was generally well tolerated. Results suggest deutetrabenazine may provide increasing benefit over time without increases in dose.

State-of-the-art pharmacological approaches to reduce chorea in Huntington's disease

Introduction Chorea is a common motor manifestation of Huntington's disease (HD). Two vesicular monoamine transporter type 2 (VMAT-2) inhibitors have been approved by the FDA for treatment of HD chorea, and a third is currently being assessed in a phase 3 trial. Antipsychotic therapies are used off-label for treatment of chorea and can treat comorbid psychiatric symptoms. There is considerable clinical equipoise regarding the safe and effective treatment of chorea and comorbid symptoms in HD.Areas covered: The authors review existing medications used to treat HD chorea in the United States of America (USA). Implications for common comorbid symptoms (e.g. psychiatric, metabolic) are also discussed. Available therapies vary widely in cost, dosing frequency, and off -target effects, both beneficial or negative.Expert opinion: Treatment considerations for chorea should account for patient comorbidities. The authors recommend prospective, observational clinical effectiveness studies which can evaluate the long-term comparative effectiveness and safety of VMAT-2 inhibitors and antipsychotics in HD. Data regarding safety of dual therapy is another critical need. This is especially timely given the changing landscape of HD therapies which may increase cost burden and possibly extend both asymptomatic and symptomatic years for HD patients.