Design optimization for clinical trials in early-stage manifest Huntington's disease.

OBJECTIVES: The purpose of this study was to inform the design of randomized clinical trials in early-stage manifest Huntington's disease through analysis of longitudinal data from TRACK-Huntington's Disease (TRACK-HD), a multicenter observational study. METHODS: We compute sample sizes required for trials with candidate clinical, functional, and imaging outcomes, whose aims are to reduce rates of change. The calculations use a 2-stage approach: first using linear mixed models to estimate mean rates of change and components of variability from TRACK-HD data and second using these to predict sample sizes for a range of trial designs. RESULTS: For each outcome, the primary drivers of the required sample size were the anticipated treatment effect and the duration of treatment. Extending durations from 1 to 2 years yielded large sample size reductions. Including interim visits and incorporating stratified randomization on predictors of outcome together with covariate adjustment gave more modest, but nontrivial, benefits. Caudate atrophy, expressed as a percentage of its baseline, was the outcome that gave smallest required sample sizes. DISCUSSION: Here we consider potential required sample sizes for clinical trials estimated from naturalistic observation of longitudinal change. Choice among outcome measures for a trial must additionally consider their relevance to patients and the expected effect of the treatment under study. For all outcomes considered, our results provide compelling arguments for 2-year trials, and we also demonstrate the benefits of incorporating stratified randomization coupled with covariate adjustment, particularly for trials with caudate atrophy as the primary outcome. The benefits of enrichment are more debatable, with statistical benefits offset by potential recruitment difficulties and reduced generalizability. © 2017 International Parkinson and Movement Disorder Society.

Natural variation in sensory-motor white matter organization influences manifestations of Huntington's disease.

While the HTT CAG-repeat expansion mutation causing Huntington's disease (HD) is highly correlated with the rate of pathogenesis leading to disease onset, considerable variance in age-at-onset remains unexplained. Therefore, other factors must influence the pathogenic process. We asked whether these factors were related to natural biological variation in the sensory-motor system. In 243 participants (96 premanifest and 35 manifest HD; 112 controls), sensory-motor structural MRI, tractography, resting-state fMRI, electrophysiology (including SEP amplitudes), motor score ratings, and grip force as sensory-motor performance were measured. Following individual modality analyses, we used principal component analysis (PCA) to identify patterns associated with sensory-motor performance, and manifest versus premanifest HD discrimination. We did not detect longitudinal differences over 12 months. PCA showed a pattern of loss of caudate, grey and white matter volume, cortical thickness in premotor and sensory cortex, and disturbed diffusivity in sensory-motor white matter tracts that was connected to CAG repeat length. Two further major principal components appeared in controls and HD individuals indicating that they represent natural biological variation unconnected to the HD mutation. One of these components did not influence HD while the other non-CAG-driven component of axial versus radial diffusivity contrast in white matter tracts were associated with sensory-motor performance and manifest HD. The first component reflects the expected CAG expansion effects on HD pathogenesis. One non-CAG-driven component reveals an independent influence on pathogenesis of biological variation in white matter tracts and merits further investigation to delineate the underlying mechanism and the potential it offers for disease modification. Hum Brain Mapp 37:4615-4628, 2016. © 2016 Wiley Periodicals, Inc.

Sleep deficits but no metabolic deficits in premanifest Huntington's disease.

OBJECTIVE: Huntington disease (HD) is a fatal autosomal dominant, neurodegenerative condition characterized by progressively worsening motor and nonmotor problems including cognitive and neuropsychiatric disturbances, along with sleep abnormalities and weight loss. However, it is not known whether sleep disturbances and metabolic abnormalities underlying the weight loss are present at a premanifest stage. METHODS: We performed a comprehensive sleep and metabolic study in 38 premanifest gene carrier individuals and 36 age- and sex-matched controls. The study consisted of 2 weeks of actigraphy at home, 2 nights of polysomnography and multiple sleep latency tests in the laboratory, and body composition assessment using dual energy x-ray absorptiometry scanning with energy expenditure measured over 10 days at home by doubly labeled water and for 36 hours in the laboratory by indirect calorimetry along with detailed cognitive and clinical assessments. We performed a principal component analyses across all measures within each studied domain. RESULTS: Compared to controls, premanifest gene carriers had more disrupted sleep, which was best characterized by a fragmented sleep profile. These abnormalities, as well as a theta power (4-7Hz) decrease in rapid eye movement sleep, were associated with disease burden score. Objectively measured sleep problems coincided with the development of cognitive, affective, and subtle motor deficits and were not associated with any metabolic alterations. INTERPRETATION: The results show that among the earliest abnormalities in premanifest HD is sleep disturbances. This raises questions as to where the pathology in HD begins and also whether it could drive some of the early features and even possibly the pathology.

Visuospatial Processing Deficits Linked to Posterior Brain Regions in Premanifest and Early Stage Huntington's Disease.

OBJECTIVES: Visuospatial processing deficits have been reported in Huntington's disease (HD). To date, no study has examined associations between visuospatial cognition and posterior brain findings in HD. METHODS: We compared 119 premanifest (55> and 64<10.8 years to expected disease onset) and 104 early symptomatic (59 stage-1 and 45 stage-2) gene carriers, with 110 controls on visual search and mental rotation performance at baseline and 12 months. In the disease groups, we also examined associations between task performance and disease severity, functional capacity and structural brain measures. RESULTS: Cross-sectionally, there were strong differences between all disease groups and controls on visual search, and between diagnosed groups and controls on mental rotation accuracy. Only the premanifest participants close to onset took longer than controls to respond correctly to mental rotation. Visual search negatively correlated with disease burden and motor symptoms in diagnosed individuals, and positively correlated with functional capacity. Mental rotation ("same") was negatively correlated with motor symptoms in stage-2 individuals, and positively correlated with functional capacity. Visual search and mental rotation were associated with parieto-occipital (pre-/cuneus, calcarine, lingual) and temporal (posterior fusiform) volume and cortical thickness. Longitudinally, visual search deteriorated over 12 months in stage-2 individuals, with no evidence of declines in mental rotation. CONCLUSIONS: Our findings provide evidence linking early visuospatial deficits to functioning and posterior cortical dysfunction in HD. The findings are important since large research efforts have focused on fronto-striatal mediated cognitive changes, with little attention given to aspects of cognition outside of these areas. (JINS, 2016, 22, 595-608).

Clinical trials in Huntington's disease: Interventions in early clinical development and newer methodological approaches.

Since the identification of the Huntington's disease (HD) gene, knowledge has accumulated about mechanisms directly or indirectly affected by the mutated Huntingtin protein. Transgenic and knock-in animal models of HD facilitate the preclinical evaluation of these targets. Several treatment approaches with varying, but growing, preclinical evidence have been translated into clinical trials. We review major landmarks in clinical development and report on the main clinical trials that are ongoing or have been recently completed. We also review clinical trial settings and designs that influence drug-development decisions, particularly given that HD is an orphan disease. In addition, we provide a critical analysis of the evolution of the methodology of HD clinical trials to identify trends toward new processes and endpoints. Biomarker studies, such as TRACK-HD and PREDICT-HD, have generated evidence for the potential usefulness of novel outcome measures for HD clinical trials, such as volumetric imaging, quantitative motor (Q-Motor) measures, and novel cognitive endpoints. All of these endpoints are currently applied in ongoing clinical trials, which will provide insight into their reliability, sensitivity, and validity, and their use may expedite proof-of-concept studies. We also outline the specific opportunities that could provide a framework for a successful avenue toward identifying and efficiently testing and translating novel mechanisms of action in the HD field.

HD-CAB: a cognitive assessment battery for clinical trials in Huntington's disease 1,2,3.

Cognitive dysfunction is central to Huntington's disease (HD) and undermines quality of life. Clinical trials are now targeting cognitive outcomes in HD; however, no cognitive battery has been optimized for HD clinical trials. We evaluated 16 cognitive tests in a 20-site, five-country, observational study designed to mimic aspects of a clinical trial (e.g., data collection managed by a contract research organization, repeated testing, prespecified statistical analyses). Fifty-five early HD, 103 premanifest HD (pre-HD), and 105 controls were tested at visit 1, visit 2 (1-3 days later), and visit 3 (5-7 weeks after visit 1). For inclusion in a recommended battery, tests were evaluated for sensitivity, practice effects, reliability, domain coverage, feasibility, and tolerability. Most tests differentiated controls from pre-HD and early HD and showed excellent psychometric properties. We selected six tests to constitute the Huntington's Disease Cognitive Assessment Battery (HD-CAB): Symbol Digit Modalities Test, Paced Tapping, One Touch Stockings of Cambridge (abbreviated), Emotion Recognition, Trail Making B, and the Hopkins Verbal Learning Test. These tests demonstrated sensitivity to disease status (Cohen's d effect sizes: early HD= -1.38 to -1.90 and pre-HD= -0.41 to -0.78), and acceptable reliability (r's 0.73-0.93). A composite score yielded large effect sizes (early HD = -2.44 and pre-HD = -0.87) and high reliability (r = 0.95). HD-CAB is the first cognitive battery designed specifically for use in late premanifest and early HD clinical trials. Adoption of the HD-CAB will facilitate evaluation of treatments to improve cognition in HD.

Safety and efficacy of laquinimod for Huntington's disease (LEGATO-HD): a multicentre, randomised, double-blind, placebo-controlled, phase 2 study.

BACKGROUND: Laquinimod modulates CNS inflammatory pathways thought to be involved in the pathology of Huntington's disease. Studies with laquinimod in transgenic rodent models of Huntington's disease suggested improvements in motor function, reduction of brain volume loss, and prolonged survival. We aimed to evaluate the safety and efficacy of laquinimod in improving motor function and reducing caudate volume loss in patients with Huntington's disease. METHODS: LEGATO-HD was a multicentre, double-blind, placebo-controlled, phase 2 study done at 48 sites across ten countries (Canada, Czech Republic, Germany, Italy, Netherlands, Portugal, Russia, Spain, UK, and USA). Patients aged 21-55 years with a cytosine-adenosine-guanine (CAG) repeat length of between 36 and 49 who had symptomatic Huntington's disease with a Unified Huntington's Disease Rating Scale-Total Motor Score (UHDRS-TMS) of higher than 5 and a Total Functional Capacity score of 8 or higher were randomly assigned (1:1:1:1) by centralised interactive response technology to laquinimod 0·5 mg, 1·0 mg, or 1·5 mg, or to matching placebo, administered orally once daily over 52 weeks; people involved in the randomisation had no other role in the study. Participants, investigators, and study personnel were masked to treatment assignment. The 1·5 mg group was discontinued before recruitment was finished because of cardiovascular safety concerns in multiple sclerosis studies. The primary endpoint was change from baseline in the UHDRS-TMS and the secondary endpoint was percent change in caudate volume, both comparing the 1·0 mg group with the placebo group at week 52. Primary and secondary endpoints were assessed in the full analysis set (ie, all randomised patients who received at least one dose of study drug and had at least one post-baseline UHDRS-TMS assessment). Safety measures included adverse event frequency and severity, and clinical and laboratory examinations, and were assessed in the safety analysis set (ie, all randomised patients who received at least one dose of study drug). This trial is registered with ClinicalTrials.gov, NCT02215616, and EudraCT, 2014-000418-75, and is now complete. FINDINGS: Between Oct 28, 2014, and June 19, 2018, 352 adults with Huntington's disease (179 [51%] men and 173 [49%] women; mean age 43·9 [SD 7·6] years and 340 [97%] White) were randomly assigned: 107 to laquinimod 0·5 mg, 107 to laquinimod 1·0 mg, 30 to laquinimod 1·5 mg, and 108 to matching placebo. Least squares mean change from baseline in UHDRS-TMS at week 52 was 1·98 (SE 0·83) in the laquinimod 1·0 mg group and 1·2 (0·82) in the placebo group (least squares mean difference 0·78 [95% CI -1·42 to 2·98], p=0·4853). Least squares mean change in caudate volume was 3·10% (SE 0·38) in the 1·0 mg group and 4·86% (0·38) in the placebo group (least squares mean difference -1·76% [95% CI -2·67 to -0·85]; p=0·0002). Laquinimod was well tolerated and there were no new safety findings. Serious adverse events were reported by eight (7%) patients on placebo, seven (7%) on laquinimod 0·5 mg, five (5%) on laquinimod 1·0 mg, and one (3%) on laquinimod 1·5 mg. There was one death, which occurred in the placebo group and was unrelated to treatment. The most frequent adverse events in all laquinimod dosed groups (0·5 mg, 1·0 mg, and 1·5 mg) were headache (38 [16%]), diarrhoea (24 [10%]), fall (18 [7%]), nasopharyngitis (20 [8%]), influenza (15 [6%]), vomiting (13 [5%]), arthralgia (11 [5%]), irritability (ten [4%]), fatigue (eight [3%]), and insomnia (eight [3%]). INTERPRETATION: Laquinimod did not show a significant effect on motor symptoms assessed by the UHDRS-TMS, but significantly reduced caudate volume loss compared with placebo at week 52. Huntington's disease has a chronic and slowly progressive course, and this study does not address whether a longer duration of laquinimod treatment could have produced detectable and meaningful changes in the clinical assessments. FUNDING: Teva Pharmaceutical Industries.

Functional and connectivity changes during working memory in Huntington's disease: 18 month longitudinal data from the IMAGE-HD study.

BACKGROUND: This study aimed to characterize, for the first time, 18 month longitudinal changes in both functional activation and functional connectivity during working memory in premanifest Huntington's disease (pre-HD) and symptomatic HD (symp-HD). METHODS: Functional magnetic resonance imaging (fMRI) was used to investigate longitudinal changes in neuronal activity during working memory performance via an N-BACK task (0-BACK and 1-BACK) in 27 pre-HD, 17 symp-HD, and 23 control participants. Whole-brain analysis of activation and region-of-interest analysis of functional connectivity was applied to longitudinal fMRI data collected at baseline and 18 months follow-up. RESULTS: Compared with controls, the pre-HD group showed significantly increased activation longitudinally during 1-BACK versus 0-BACK in the lateral and medial prefrontal, anterior cingulate, primary motor, and temporal areas cortically, and caudate and putamen subcortically. Pre-HD far from onset, compared with controls, showed further longitudinal increases in the right and left dorsolateral prefrontal cortex (DLPFC). Longitudinal increased activation in anterior cingulate and medial primary motor areas were associated with disease burden in the pre-HD group. Moreover, in pre-HD increased activation over time in primary motor and putamen regions were associated with average response time during 1-BACK performance. During 1-BACK, functional connectivity between the right DLPFC and posterior parietal, anterior cingulate, and caudate was significantly reduced over 18months only in the pre-HD group. CONCLUSIONS: Longitudinal reductions in connectivity over 18 months may represent an early signature of cortico-cortical and cortico-striatal functional disconnectivity in pre-HD, whereas the concomitant increased cortical and subcortical activation may reflect a compensatory response to the demands for cognitive resources required during task performance. Our findings demonstrate that functional imaging modalities have the potential to serve as sensitive methods for the assessment of cortical and subcortical responses to future treatment measures.

A PET-CT study on neuroinflammation in Huntington's disease patients participating in a randomized trial with laquinimod.

Microglia activation, an indicator of central nervous system inflammation, is believed to contribute to the pathology of Huntington's disease. Laquinimod is capable of regulating microglia. By targeting the translocator protein, 11C-PBR28 PET-CT imaging can be used to assess the state of regional gliosis in vivo and explore the effects of laquinimod treatment. This study relates to the LEGATO-HD, multi-centre, double-blinded, Phase 2 clinical trial with laquinimod (US National Registration: NCT02215616). Fifteen patients of the UK LEGATO-HD cohort (mean age: 45.2 ± 7.4 years; disease duration: 5.6 ± 3.0 years) were treated with laquinimod (0.5 mg, N = 4; 1.0 mg, N = 6) or placebo (N = 5) daily. All participants had one 11C-PBR28 PET-CT and one brain MRI scan before laquinimod (or placebo) and at the end of treatment (12 months apart). PET imaging data were quantified to produce 11C-PBR28 distribution volume ratios. These ratios were calculated for the caudate and putamen using the reference Logan plot with the corpus callosum as the reference region. Partial volume effect corrections (Müller-Gartner algorithm) were applied. Differences were sought in Unified Huntington's Disease Rating Scale scores and regional distribution volume ratios between baseline and follow-up and between the two treatment groups (laquinimod versus placebo). No significant change in 11C-PBR28 distribution volume ratios was found post treatment in the caudate and putamen for both those treated with laquinimod (N = 10) and those treated with placebo (N = 5). Over time, the patients treated with laquinimod did not show a significant clinical improvement. Data from the 11C-PBR28 PET-CT study indicate that laquinimod may not have affected regional translocator protein expression and clinical performance over the studied period.

A biological classification of Huntington's disease: the Integrated Staging System.

The current research paradigm for Huntington's disease is based on participants with overt clinical phenotypes and does not address its pathophysiology nor the biomarker changes that can precede by decades the functional decline. We have generated a new research framework to standardise clinical research and enable interventional studies earlier in the disease course. The Huntington's Disease Integrated Staging System (HD-ISS) comprises a biological research definition and evidence-based staging centred on biological, clinical, and functional assessments. We used a formal consensus method that involved representatives from academia, industry, and non-profit organisations. The HD-ISS characterises individuals for research purposes from birth, starting at Stage 0 (ie, individuals with the Huntington's disease genetic mutation without any detectable pathological change) by using a genetic definition of Huntington's disease. Huntington's disease progression is then marked by measurable indicators of underlying pathophysiology (Stage 1), a detectable clinical phenotype (Stage 2), and then decline in function (Stage 3). Individuals can be precisely classified into stages based on thresholds of stage-specific landmark assessments. We also demonstrated the internal validity of this system. The adoption of the HD-ISS could facilitate the design of clinical trials targeting populations before clinical motor diagnosis and enable data standardisation across ongoing and future studies.

An orally available, brain penetrant, small molecule lowers huntingtin levels by enhancing pseudoexon inclusion.

Huntington's Disease (HD) is a progressive neurodegenerative disorder caused by CAG trinucleotide repeat expansions in exon 1 of the huntingtin (HTT) gene. The mutant HTT (mHTT) protein causes neuronal dysfunction, causing progressive motor, cognitive and behavioral abnormalities. Current treatments for HD only alleviate symptoms, but cerebral spinal fluid (CSF) or central nervous system (CNS) delivery of antisense oligonucleotides (ASOs) or virus vectors expressing RNA-induced silencing (RNAi) moieties designed to induce mHTT mRNA lowering have progressed to clinical trials. Here, we present an alternative disease modifying therapy the orally available, brain penetrant small molecule branaplam. By promoting inclusion of a pseudoexon in the primary transcript, branaplam lowers mHTT protein levels in HD patient cells, in an HD mouse model and in blood samples from Spinal Muscular Atrophy (SMA) Type I patients dosed orally for SMA (NCT02268552). Our work paves the way for evaluating branaplam's utility as an  HD therapy, leveraging small molecule splicing modulators to reduce expression of dominant disease genes by driving pseudoexon inclusion.

An item response analysis of the motor and behavioral subscales of the unified Huntington's disease rating scale in huntington disease gene expansion carriers.

Although the Unified Huntington's Disease Rating Scale (UHDRS) is widely used in the assessment of Huntington disease (HD), the ability of individual items to discriminate individual differences in motor or behavioral manifestations has not been extensively studied in HD gene expansion carriers without a motor-defined clinical diagnosis (ie, prodromal-HD or prHD). To elucidate the relationship between scores on individual motor and behavioral UHDRS items and total score for each subscale, a nonparametric item response analysis was performed on retrospective data from 2 multicenter longitudinal studies. Motor and behavioral assessments were supplied for 737 prHD individuals with data from 2114 visits (PREDICT-HD) and 686 HD individuals with data from 1482 visits (REGISTRY). Option characteristic curves were generated for UHDRS subscale items in relation to their subscale score. In prHD, overall severity of motor signs was low, and participants had scores of 2 or above on very few items. In HD, motor items that assessed ocular pursuit, saccade initiation, finger tapping, tandem walking, and to a lesser extent, saccade velocity, dysarthria, tongue protrusion, pronation/supination, Luria, bradykinesia, choreas, gait, and balance on the retropulsion test were found to discriminate individual differences across a broad range of motor severity. In prHD, depressed mood, anxiety, and irritable behavior demonstrated good discriminative properties. In HD, depressed mood demonstrated a good relationship with the overall behavioral score. These data suggest that at least some UHDRS items appear to have utility across a broad range of severity, although many items demonstrate problematic features.

Antidepressant, anxiolytic and anorectic effects of a melanin-concentrating hormone-1 receptor antagonist.

Melanin concentrating hormone (MCH) is an orexigenic hypothalamic neuropeptide, which plays an important role in the complex regulation of energy balance and body weight. Here we show that SNAP-7941, a selective, high-affinity MCH1 receptor (MCH1-R) antagonist, inhibited food intake stimulated by central administration of MCH, reduced consumption of palatable food, and, after chronic administration to rats with diet-induced obesity, resulted in a marked, sustained decrease in body weight. In addition, after mapping the binding sites for [(3)H]SNAP-7941 in rat brain, we evaluated its effects in a series of behavioral models. SNAP-7941 produced effects similar to clinically used antidepressants and anxiolytics in three animal models of depression/anxiety: the rat forced-swim test, rat social interaction and guinea pig maternal-separation vocalization tests. Given these observations, an MCH1-R antagonist may be useful not only in the management of obesity but also as a treatment for depression and/or anxiety.

Longitudinal expression changes are weak correlates of disease progression in Huntington's disease.

Huntington's disease is a severe but slowly progressive hereditary illness for which only symptomatic treatments are presently available. Clinical measures of disease progression are somewhat subjective and may require years to detect significant change. There is a clear need to identify more sensitive, objective and consistent measures to detect disease progression in Huntington's disease clinical trials. Whereas Huntington's disease demonstrates a robust and consistent gene expression signature in the brain, previous studies of blood cell RNAs have lacked concordance with clinical disease stage. Here we utilized longitudinally collected samples from a well-characterized cohort of control, Huntington's disease-at-risk and Huntington's disease subjects to evaluate the possible correlation of gene expression and disease status within individuals. We interrogated these data in both cross-sectional and longitudinal analyses. A number of changes in gene expression showed consistency within this study and as compared to previous reports in the literature. The magnitude of the mean disease effect over 2 years' time was small, however, and did not track closely with motor symptom progression over the same time period. We therefore conclude that while blood-derived gene expression indicators can be of value in understanding Huntington's disease pathogenesis, they are insufficiently sensitive to be of use as state biomarkers.

Biological and clinical manifestations of Huntington's disease in the longitudinal TRACK-HD study: cross-sectional analysis of baseline data.

BACKGROUND: Huntington's disease (HD) is an autosomal dominant, fully penetrant, neurodegenerative disease that most commonly affects adults in mid-life. Our aim was to identify sensitive and reliable biomarkers in premanifest carriers of mutated HTT and in individuals with early HD that could provide essential methodology for the assessment of therapeutic interventions. METHODS: This multicentre study uses an extensive battery of novel assessments, including multi-site 3T MRI, clinical, cognitive, quantitative motor, oculomotor, and neuropsychiatric measures. Blinded analyses were done on the baseline cross-sectional data from 366 individuals: 123 controls, 120 premanifest (pre-HD) individuals, and 123 patients with early HD. FINDINGS: The first participant was enrolled in January, 2008, and all assessments were completed by August, 2008. Cross-sectional analyses identified significant changes in whole-brain volume, regional grey and white matter differences, impairment in a range of voluntary neurophysiological motor, and oculomotor tasks, and cognitive and neuropsychiatric dysfunction in premanifest HD gene carriers with normal motor scores through to early clinical stage 2 disease. INTERPRETATION: We show the feasibility of rapid data acquisition and the use of multi-site 3T MRI and neurophysiological motor measures in a large multicentre study. Our results provide evidence for quantifiable biological and clinical alterations in HTT expansion carriers compared with age-matched controls. Many parameters differ from age-matched controls in a graded fashion and show changes of increasing magnitude across our cohort, who range from about 16 years from predicted disease diagnosis to early HD. These findings might help to define novel quantifiable endpoints and methods for rapid and reliable data acquisition, which could aid the design of therapeutic trials.

Safety and efficacy of pridopidine in patients with Huntington's disease (PRIDE-HD): a phase 2, randomised, placebo-controlled, multicentre, dose-ranging study.

BACKGROUND: Previous trials have shown that pridopidine might reduce motor impairment in patients with Huntington's disease. The aim of this study was to ascertain whether higher doses of pridopidine than previously tested reduce motor symptoms in a dose-dependent manner while maintaining acceptable safety and tolerability. METHODS: PRIDE-HD was a randomised, placebo-controlled, phase 2, dose-ranging study in adults (aged ≥21 years) with Huntington's disease at outpatient clinics in 53 sites across 12 countries (Australia, Austria, Canada, Denmark, France, Germany, Italy, Poland, Russia, the Netherlands, the UK, and the USA). Eligible patients had clinical onset after age 18 years, 36 or more cytosine-adenine-guanine repeats in the huntingtin gene, motor symptoms (Unified Huntington's Disease Rating Scale total motor score [UHDRS-TMS] ≥25 points), and reduced independence (UHDRS independence score ≤90%). Patients were randomly assigned (1:1:1:1:1) with centralised interactive-response technology to receive one of four doses of pridopidine (45, 67·5, 90, or 112·5 mg) or placebo orally twice a day for 52 weeks. Randomisation was stratified within centres by neuroleptic drug use. The primary efficacy endpoint was change in the UHDRS-TMS from baseline to 26 weeks, which was assessed in all randomised patients who received at least one dose of study drug and had at least one post-baseline efficacy assessment (full analysis set). Participants and investigators were masked to treatment assignment. This trial is registered with EudraCT (2013-001888-23) and ClinicalTrials.gov (NCT02006472). FINDINGS: Between Feb 13, 2014, and July 5, 2016, 408 patients were enrolled and randomly assigned to receive placebo (n=82) or pridopidine 45 mg (n=81), 67·5 mg (n=82), 90 mg (n=81), or 112·5 mg (n=82) twice daily for 26 weeks. The full analysis set included 397 patients (81 in the placebo group, 75 in the 45 mg group, 79 in the 67·5 mg group, 81 in the 90 mg group, and 81 in the 112·5 mg group). Pridopidine did not significantly change the UHDRS-TMS at 26 weeks compared with placebo at any dose. The most frequent adverse events across all groups were diarrhoea, vomiting, nasopharyngitis, falls, headache, insomnia, and anxiety. The most common treatment-related adverse events were insomnia, diarrhoea, nausea, and dizziness. Serious adverse events occurred in the pridopidine groups only and were most frequently falls (n=5), suicide attempt (n=4), suicidal ideation (n=3), head injury (n=3), and aspiration pneumonia (n=3). No new safety or tolerability concerns emerged in this study. One death in the pridopidine 112·5 mg group due to aspiration pneumonia was considered to be possibly related to the study drug. INTERPRETATION: Pridopidine did not improve the UHDRS-TMS at week 26 compared with placebo and, thus, the results of secondary or tertiary analyses in previous trials were not replicated. A potentially strong placebo effect needs to be ruled out in future studies. FUNDING: Teva Pharmaceutical Industries.

Association of CAG Repeats With Long-term Progression in Huntington Disease.

IMPORTANCE: In Huntington disease (HD), mutation severity is defined by the length of the CAG trinucleotide sequence, a well-known predictor of clinical onset age. The association with disease trajectory is less well characterized. Quantifiable summary measures of trajectory applicable over decades of early disease progression are lacking. An accurate model of the age-CAG association with early progression is critical to clinical trial design, informing both sample size and intervention timing. OBJECTIVE: To succinctly capture the decades-long early progression of HD and its dependence on CAG repeat length. DESIGN, SETTING, AND PARTICIPANTS: Prospective study at 4 academic HD treatment and research centers. Participants were the combined sample from the TRACK-HD and Track-On HD studies consisting of 290 gene carriers (presymptomatic to stage II), recruited from research registries at participating centers, and 153 nonbiologically related controls, generally spouses or friends. Recruitment was targeted to match a balanced, prespecified spectrum of age, CAG repeat length, and diagnostic status. In the TRACK-HD and Track-On HD studies, 13 and 5 potential participants, respectively, failed study screening. Follow-up ranged from 0 to 6 years. The study dates were January 2008 to November 2014. These analyses were performed between December 2015 and January 2019. MAIN OUTCOMES AND MEASURES: The outcome measures were principal component summary scores of motor-cognitive function and of brain volumes. The main outcome was the association of these scores with age and CAG repeat length. RESULTS: We analyzed 2065 visits from 443 participants (247 female [55.8%]; mean [SD] age, 44.4 [10.3] years). Motor-cognitive measures were highly correlated and had similar CAG repeat length-dependent associations with age. A composite summary score accounted for 67.6% of their combined variance. This score was well approximated by a score combining 3 items (total motor score, Symbol Digit Modalities Test, and Stroop word reading) from the Unified Huntington's Disease Rating Scale. For either score, initial progression age and then acceleration rate were highly CAG repeat length dependent. The acceleration continues through at least stage II disease. In contrast, 3 distinct patterns emerged among brain measures (basal ganglia, gray matter, and a combination of whole-brain, ventricular, and white matter volumes). The basal ganglia pattern showed considerable change in even the youngest participants but demonstrated minimal acceleration of loss with aging. Each clinical and brain summary score was strongly associated with the onset and rate of decline in total functional capacity. CONCLUSIONS AND RELEVANCE: Results of this study suggest that succinct summary measures of function and brain loss characterize HD progression across a wide disease span. CAG repeat length strongly predicts their decline rate. This work aids our understanding of the age and CAG repeat length-dependent association between changes in the brain and clinical manifestations of HD.

Longitudinal changes in the fronto-striatal network are associated with executive dysfunction and behavioral dysregulation in Huntington's disease: 30 months IMAGE-HD data.

Neuropsychiatric disturbance-particularly executive dysfunction and behavioral dysregulation-is a common feature of Huntington's disease (HD), with implications for functional capacity and quality of life. No study to date has ascertained whether longitudinal change in brain activity is associated with neuropsychiatric deficits in HD. We used a set-response-shifting task together with functional magnetic resonance imaging to investigate 30-month longitudinal blood-oxygen level dependent (BOLD) signal changes in the fronto-striatal attentional control network in premanifest and symptomatic HD (pre-HD and symp-HD, respectively), relative to healthy control participants. We also assessed the extent to which changes in the BOLD signal over time were related to neuropsychiatric measures in the domains of executive dysfunction and behavioral dysregulation. Associations were also evaluated with clinical and disease severity. We found no longitudinal BOLD differences between pre-HD and controls over 30 months. In contrast, reduction in BOLD response over time was greater in symp-HD, relative to controls, in task-related areas (e.g., anterior cingulate cortex and striatum) and in regions from the default mode network (e.g., medial prefrontal cortex and posterior cingulate/precuneus). Moreover, when considered across both premanifest and symptomatic stages, longitudinal BOLD signal decline in the right dorsolateral prefrontal cortex and putamen was associated with executive dysfunction and behavioral dysregulation measures. In addition, longitudinal reduction in BOLD signal, in fronto-striatal and default mode networks, correlated with disease severity. These results suggest that longitudinal change in fronto-striatal and default mode networks may be useful in understanding the biological underpinnings of functional decline in HD. Such findings offer new avenues for targeted treatments in terms of minimizing psychiatric impairment and potentially maximizing cognitive function.

A Computational Cognitive Biomarker for Early-Stage Huntington's Disease.

Huntington's disease (HD) is genetically determined but with variability in symptom onset, leading to uncertainty as to when pharmacological intervention should be initiated. Here we take a computational approach based on neurocognitive phenotyping, computational modeling, and classification, in an effort to provide quantitative predictors of HD before symptom onset. A large sample of subjects-consisting of both pre-manifest individuals carrying the HD mutation (pre-HD), and early symptomatic-as well as healthy controls performed the antisaccade conflict task, which requires executive control and response inhibition. While symptomatic HD subjects differed substantially from controls in behavioral measures [reaction time (RT) and error rates], there was no such clear behavioral differences in pre-HD. RT distributions and error rates were fit with an accumulator-based model which summarizes the computational processes involved and which are related to identified mechanisms in more detailed neural models of prefrontal cortex and basal ganglia. Classification based on fitted model parameters revealed a key parameter related to executive control differentiated pre-HD from controls, whereas the response inhibition parameter declined only after symptom onset. These findings demonstrate the utility of computational approaches for classification and prediction of brain disorders, and provide clues as to the underlying neural mechanisms.

Medication Use in Early-HD Participants in Track-HD: an Investigation of its Effects on Clinical Performance.

 Insufficient evidence exists to guide the long-term pharmacological management of Huntington's disease (HD) although most current interventions rely on symptomatic management. The effect of many frontline treatments on potential endpoints for HD clinical trials remains unknown. Our objective was to investigate how therapies widely used to manage HD affect the symptom for which they are prescribed and other endpoints using data from TRACK-HD. We used longitudinal models to estimate effects of medication use on performance on tests of motor, cognitive and neuropsychiatric function using data from 123 TRACK-HD stage 1/2 participants across four study visits. Adjustment for confounding by prior medication use, prior clinical performance, concomitant use of other medications, and baseline variables (sex, disease group, age, CAG, study site, education) enabled a closer-to-causal interpretation of the associations. Adjusting for baseline variables only, medication use was typically associated with worse clinical performance, reflecting greater medication use in more advanced patients. After additional adjustment for longitudinal confounders such "inverse" associations were generally eliminated and in the expected directions: participants taking neuroleptics tended to have better motor performance, improved affect and poorer cognitive performance, and those taking SSRI/SNRIs had less apathy, less affect and better total behaviour scores. However, we uncovered few statistically significant associations. Limitations include sample size and unmeasured confounding. In conclusion, adjustment for confounding by prior measurements largely eliminated associations between medication use and poorer clinical performance from simple analyses. However, there was little convincing evidence of causal effects of medication on clinical performance and larger cohorts or trials are needed.