Temperature instability of a mutation at a multidomain junction in Na,K-ATPase isoform ATP1A3 (p.Arg756His) produces a fever-induced neurological syndrome.

ATP1A3 encodes the α3 isoform of Na,K-ATPase. In the brain, it is expressed only in neurons. Human ATP1A3 mutations produce a wide spectrum of phenotypes, but particular syndromes are associated with unique substitutions. For arginine 756, at the junction of membrane and cytoplasmic domains, mutations produce encephalopathy during febrile infections. Here we tested the pathogenicity of p.Arg756His (R756H) in isogenic mammalian cells. R756H protein had sufficient transport activity to support cells when endogenous ATP1A1 was inhibited. It had half the turnover rate of wildtype, reduced affinity for Na+, and increased affinity for K+. There was modest endoplasmic reticulum retention during biosynthesis at 37 °C but little benefit from the folding drug phenylbutyrate (4-PBA), suggesting a tolerated level of misfolding. When cells were incubated at just 39 °C, however, α3 protein level dropped without loss of ß subunit, paralleled by an increase of endogenous α1. Elevated temperature resulted in internalization of α3 from the surface along with some ß subunit, accompanied by cytoplasmic redistribution of a marker of lysosomes and endosomes, lysosomal-associated membrane protein 1. After return to 37 °C, α3 protein levels recovered with cycloheximide-sensitive new protein synthesis. Heating in vitro showed activity loss at a rate 20- to 30-fold faster than wildtype, indicating a temperature-dependent destabilization of protein structure. Arg756 appears to confer thermal resistance as an anchor, forming hydrogen bonds among four linearly distant parts of the Na,K-ATPase structure. Taken together, our observations are consistent with fever-induced symptoms in patients.

Misfolding, altered membrane distributions, and the unfolded protein response contribute to pathogenicity differences in Na,K-ATPase ATP1A3 mutations.

Missense mutations in ATP1A3, the α3 isoform of Na,K-ATPase, cause neurological phenotypes that differ greatly in symptoms and severity. A mechanistic basis for differences is lacking, but reduction of activity alone cannot explain them. Isogenic cell lines with endogenous α1 and inducible exogenous α3 were constructed to compare mutation properties. Na,K-ATPase is made in the endoplasmic reticulum (ER), but the glycan-free catalytic α subunit complexes with glycosylated ß subunit in the ER to proceed through Golgi and post-Golgi trafficking. We previously observed classic evidence of protein misfolding in mutations with severe phenotypes: differences in ER retention of endogenous ß1 subunit, impaired trafficking of α3, and cytopathology, suggesting that they misfold during biosynthesis. Here we tested two mutations associated with different phenotypes: D923N, which has a median age of onset of hypotonia or dystonia at 3 years, and L924P, with severe infantile epilepsy and profound impairment. Misfolding during biosynthesis in the ER activates the unfolded protein response, a multiarmed program that enhances protein folding capacity, and if that fails, triggers apoptosis. L924P showed more nascent protein retention in ER than D923N; more ER-associated degradation of α3 (ERAD); larger differences in Na,K-ATPase subunit distributions among subcellular fractions; and greater inactivation of eIF2α, a major defensive step of the unfolded protein response. In L924P there was also altered subcellular distribution of endogenous α1 subunit, analogous to a dominant negative effect. Both mutations showed pro-apoptotic sensitization by reduced phosphorylation of BAD. Encouragingly, however, 4-phenylbutyrate, a pharmacological corrector, reduced L924P ER retention, increased α3 expression, and restored morphology.

A Multi-center Genome-wide Association Study of Cervical Dystonia.

BACKGROUND: Several monogenic causes for isolated dystonia have been identified, but they collectively account for only a small proportion of cases. Two genome-wide association studies have reported a few potential dystonia risk loci; but conclusions have been limited by small sample sizes, partial coverage of genetic variants, or poor reproducibility. OBJECTIVE: To identify robust genetic variants and loci in a large multicenter cervical dystonia cohort using a genome-wide approach. METHODS: We performed a genome-wide association study using cervical dystonia samples from the Dystonia Coalition. Logistic and linear regressions, including age, sex, and population structure as covariates, were employed to assess variant- and gene-based genetic associations with disease status and age at onset. We also performed a replication study for an identified genome-wide significant signal. RESULTS: After quality control, 919 cervical dystonia patients compared with 1491 controls of European ancestry were included in the analyses. We identified one genome-wide significant variant (rs2219975, chromosome 3, upstream of COL8A1, P-value 3.04 × 10-8 ). The association was not replicated in a newly genotyped sample of 473 cervical dystonia cases and 481 controls. Gene-based analysis identified DENND1A to be significantly associated with cervical dystonia (P-value 1.23 × 10-6 ). One low-frequency variant was associated with lower age-at-onset (16.4 ± 2.9 years, P-value = 3.07 × 10-8 , minor allele frequency = 0.01), located within the GABBR2 gene on chromosome 9 (rs147331823). CONCLUSION: The genetic underpinnings of cervical dystonia are complex and likely consist of multiple distinct variants of small effect sizes. Larger sample sizes may be needed to provide sufficient statistical power to address the presumably multi-genic etiology of cervical dystonia. © 2021 International Parkinson and Movement Disorder Society.

Predictive modeling of spread in adult-onset isolated dystonia: Key properties and effect of tremor inclusion.

BACKGROUND AND PURPOSE: Several clinical and demographic factors relate to anatomic spread of adult-onset isolated dystonia, but a predictive model is still lacking. The aims of this study were: (i) to develop and validate a predictive model of anatomic spread of adult-onset isolated dystonia; and (ii) to evaluate whether presence of tremor associated with dystonia influences model predictions of spread. METHODS: Adult-onset isolated dystonia participants with focal onset from the Dystonia Coalition Natural History Project database were included. We developed two prediction models, one with dystonia as sole disease manifestation ("dystonia-only") and one accepting dystonia OR tremor in any body part as disease manifestations ("dystonia OR tremor"). Demographic and clinical predictors were selected based on previous evidence, clinical plausibility of association with spread, or both. We used logistic regressions and evaluated model discrimination and calibration. Internal validation was carried out based on bootstrapping. RESULTS: Both predictive models showed an area under the curve of 0.65 (95% confidence intervals 0.62-0.70 and 0.62-0.69, respectively) and good calibration after internal validation. In both models, onset of dystonia in body regions other than the neck, older age, depression and history of neck trauma were predictors of spread. CONCLUSIONS: This predictive modeling of spread in adult-onset isolated dystonia based on accessible predictors (demographic and clinical) can be easily implemented to inform individuals' risk of spread. Because tremor did not influence prediction of spread, our results support the argument that tremor is a part of the dystonia syndrome, and not an independent or coincidental disorder.

Factors in the disease severity of ATP1A3 mutations: Impairment, misfolding, and allele competition.

Dominant mutations of ATP1A3, a neuronal Na,K-ATPase α subunit isoform, cause neurological disorders with an exceptionally wide range of severity. Several new mutations and their phenotypes are reported here (p.Asp366His, p.Asp742Tyr, p.Asp743His, p.Leu924Pro, and a VUS, p.Arg463Cys). Mutations associated with mild or severe phenotypes [rapid-onset dystonia-parkinsonism (RDP), alternating hemiplegia of childhood (AHC), or early infantile epileptic encephalopathy (EIEE)] were expressed in HEK-293 cells. Paradoxically, the severity of human symptoms did not correlate with whether there was enough residual activity to support cell survival. We hypothesized that distinct cellular consequences may result not only from pump inactivation but also from protein misfolding. Biosynthesis was investigated in four tetracycline-inducible isogenic cell lines representing different human phenotypes. Two cell biological complications were found. First, there was impaired trafficking of αß complex to Golgi apparatus and plasma membrane, as well as changes in cell morphology, for two mutations that produced microcephaly or regions of brain atrophy in patients. Second, there was competition between exogenous mutant ATP1A3 (α3) and endogenous ATP1A1 (α1) so that their sum was constant. This predicts that in patients, the ratio of normal to mutant ATP1A3 proteins will vary when misfolding occurs. At the two extremes, the results suggest that a heterozygous mutation that only impairs Na,K-ATPase activity will produce relatively mild disease, while one that activates the unfolded protein response could produce severe disease and may result in death of neurons independently of ion pump inactivation.

Revising rapid-onset dystonia-parkinsonism: Broadening indications for ATP1A3 testing.

BACKGROUND AND OBJECTIVES: Rapid-onset dystonia-parkinsonism (RDP) is caused by mutations in the ATP1A3 gene, which codes for the α-3 subunit of the Na+ /K+ ATPase. It has been characterized by rapid-onset bulbar dysfunction, limb dystonia, bradykinesia, and a rostrocaudal spatial gradient of expression, usually after a physiologic trigger. We reexamined whether these features were in fact characteristic. METHODS: We characterized phenotypic variation within a cohort of 50 ATP1A3 mutation-positive individuals (carriers) and 44 mutation-negative family members (noncarriers). Potential participants were gathered through referral for clinical suspicion of RDP or alternating hemiplegia of childhood. Inclusion criteria were having a ATP1A3 mutation or being a family member of such an individual. RESULTS: We found RDP is underdiagnosed if only "characteristic" patients are tested. Rapid onset and bulbar predominance were not universally present in carriers. Among those with at least mild symptoms of dystonia, rostrocaudal severity gradient was rare (7%). Symptoms began focally but progressed to be generalized (51%) or multifocal (49%). Arm (41%) onset was most common. Arms and voice were typically most severely affected (48% and 44%, respectively). Triggers preceded onset in 77% of the participants. Rapid onset, dystonia, parkinsonism, bulbar symptoms, headaches, seizures, frontal impairment, and a history of mood disorder and a history of psychosis were more common in carriers. Approximately half of the proband mutations occurred de novo (56%). CONCLUSIONS: Our findings suggest that patients should not be excluded from ATP1A3 testing because of slow onset, limb onset, absent family history, or onset in middle adulthood. RDP should be strongly considered in the differential for any bulbar dystonia. © 2019 International Parkinson and Movement Disorder Society.

A 500 U/2 mL dilution of abobotulinumtoxinA vs. placebo: randomized study in cervical dystonia.

Purpose/aim: AbobotulinumtoxinA (Dysport®, Ipsen Biopharmaceuticals, Inc., Basking Ridge, NJ, USA) is an acetylcholine release inhibitor and a neuromuscular blocking agent. The United States prescribing information for abobotulinumtoxinA previously indicated only one dilution for cervical dystonia: 500 U/1 mL. Clinical trial data supporting a larger volume with a 500 U/2 mL dilution would offer clinicians flexibility with injection volume to better meet patient needs. MATERIALS AND METHODS: We conducted a 12-week, phase 3b, multicenter, randomized, double-blind, placebo-controlled trial (NCT01753310). Adult subjects with a primary diagnosis of cervical dystonia were randomized (2:1) to receive a single injection of either abobotulinumtoxinA, 500 U/2 mL dilution, or placebo. The primary efficacy endpoint was changed from baseline in Toronto Western Spasmodic Torticollis Rating Scale total score at Week 4. RESULTS: A total of 134 subjects (abobotulinumtoxinA, n = 89; placebo, n = 45) were randomized (intent-to-treat population) and 129 (abobotulinumtoxinA, n = 84; placebo, n = 45) completed the Week 4 primary endpoint evaluation (modified intent-to-treat population). In the modified intent-to-treat population, subjects receiving abobotulinumtoxinA experienced significantly greater changes from baseline versus placebo on the primary endpoint (weighted overall treatment difference -8.3, P < 0.001). The most common treatment-emergent adverse events (TEAEs) were dysphagia, muscle weakness, neck pain and headache. Overall, TEAEs were consistent with those reported in the abobotulinumtoxinA prescribing information (1 mL dilution) for cervical dystonia patients. CONCLUSIONS: This trial provides evidence that a 500 U/2 mL dilution is an effective treatment for cervical dystonia and exhibits a safety profile consistent with the known safety profile of abobotulinumtoxinA.

Novel mutations in ATP1A3 associated with catastrophic early life epilepsy, episodic prolonged apnea, and postnatal microcephaly.

OBJECTIVE: Mutations of ATP1A3 have been associated with rapid onset dystonia-parkinsonism and more recently with alternating hemiplegia of childhood. Here we report one child with catastrophic early life epilepsy and shortened survival, and another with epilepsy, episodic prolonged apnea, postnatal microcephaly, and severe developmental disability. Novel heterozygous mutations (p.Gly358Val and p.Ile363Asn) were identified in ATP1A3 in these children. METHODS: Subjects underwent next-generation sequencing under a research protocol. Clinical data were collected retrospectively. The biochemical effects of the mutations on ATP1A3 protein function were investigated. Postmortem neuropathologic specimens from control and affected subjects were studied. RESULTS: The mutations localized to the P domain of the Na,K-ATPase α3 protein, and resulted in significant reduction of Na,K-ATPase activity in vitro. We demonstrate in both control human brain tissue and that from the subject with the p.Gly358Val mutation that ATP1A3 immunofluorescence is prominently associated with interneurons in the cortex, which may provide some insight into the pathogenesis of the disease. SIGNIFICANCE: The findings indicate these mutations cause severe phenotypes of ATP1A3-related disorder spectrum that include catastrophic early life epilepsy, episodic apnea, and postnatal microcephaly.

Rapid-onset dystonia-parkinsonism associated with the I758S mutation of the ATP1A3 gene: a neuropathologic and neuroanatomical study of four siblings.

Rapid-onset dystonia-parkinsonism (RDP) is a movement disorder associated with mutations in the ATP1A3 gene. Signs and symptoms of RDP commonly occur in adolescence or early adulthood and can be triggered by physical or psychological stress. Mutations in ATP1A3 are also associated with alternating hemiplegia of childhood (AHC). The neuropathologic substrate of these conditions is unknown. The central nervous system of four siblings, three affected by RDP and one asymptomatic, all carrying the I758S mutation in the ATP1A3 gene, was analyzed. This neuropathologic study is the first carried out in ATP1A3 mutation carriers, whether affected by RDP or AHC. Symptoms began in the third decade of life for two subjects and in the fifth for another. The present investigation aimed at identifying, in mutation carriers, anatomical areas potentially affected and contributing to RDP pathogenesis. Comorbid conditions, including cerebrovascular disease and Alzheimer disease, were evident in all subjects. We evaluated areas that may be relevant to RDP separately from those affected by the comorbid conditions. Anatomical areas identified as potential targets of I758S mutation were globus pallidus, subthalamic nucleus, red nucleus, inferior olivary nucleus, cerebellar Purkinje and granule cell layers, and dentate nucleus. Involvement of subcortical white matter tracts was also evident. Furthermore, in the spinal cord, a loss of dorsal column fibers was noted. This study has identified RDP-associated pathology in neuronal populations, which are part of complex motor and sensory loops. Their involvement would cause an interruption of cerebral and cerebellar connections which are essential for maintenance of motor control.

Cognitive impairment in rapid-onset dystonia-parkinsonism.

Rapid-onset dystonia-parkinsonism (RDP) is caused by mutations in the ATP1A3 gene. This observational study sought to determine if cognitive performance is decreased in patients with RDP compared with mutation-negative controls. We studied 22 familial RDP patients, 3 non-motor-manifesting mutation-positive family members, 29 mutation-negative family member controls in 9 families, and 4 unrelated RDP patients, totaling 58 individuals. We administered a movement disorder assessment, including the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and the Unified Parkinson's Disease Rating Scale (UPDRS) and a cognitive battery of memory and learning, psychomotor speed, attention, and executive function. The cognitive battery was designed to evaluate a wide range of functions; recognition memory instruments were selected to be relatively pure measures of delayed memory, devoid of significant motor or vocal production limitations. Comparisons of standardized cognitive scores were assessed both with and without controlling for psychomotor speed and similarly for severity of depressive symptoms. A majority of RDP patients had onset of motor symptoms by age 25 and had initial symptom presentation in the upper body (face, mouth, or arm). Among patients, the BFMDRS (mean ± SD, 52.1 ± 29.5) and UPDRS motor subscore (29.8 ± 12.7) confirmed dystonia-parkinsonism. The affected RDP patients performed more poorly, on average, than mutation-negative controls for all memory and learning, psychomotor speed, attention, and executive function scores (all P ≤ 0.01). These differences persisted after controlling for psychomotor speed and severity of depressive symptoms. Impaired cognitive function may be a manifestation of ATP1A3 mutation and RDP.

A randomized, double-blind study of repeated incobotulinumtoxinA (Xeomin(®)) in cervical dystonia.

IncobotulinumtoxinA (Xeomin(®), NT 201), a preparation without accessory (complexing) proteins, has shown comparable efficacy and safety to onabotulinumtoxinA in treating cervical dystonia (CD). This study evaluated the efficacy and safety of repeated incobotulinumtoxinA injections in subjects with CD. Following a ≤20-week placebo-controlled, randomized, double-blind, single-dose main period, subjects could enter a ≤68-week prospective, randomized, double-blind, repeated-dose, flexible-interval (minimum 6 weeks) extension period with 240 U or 120 U of incobotulinumtoxinA (≤5 injections). Outcome measures included the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and adverse events (AEs). Of 219 subjects completing the main period, 214 were randomized in the extension period to receive incobotulinumtoxinA 240 U (n = 111) or 120 U (n = 103); 169 subjects completed the extension period, with 90 receiving five injection sessions. Both doses of incobotulinumtoxinA provided statistically significant and clinically relevant improvements in mean TWSTRS-Total, -Severity, -Disability, and -Pain scores, from each injection session to respective 4-week follow-up visits. The most frequently reported AE was dysphagia (240 U: 23.4 %; 120 U: 12.6 %), which did not result in any study withdrawals. There was no impact of injection interval on the incidence of AEs (post hoc analysis). A major limitation of this study was the fixed dose design requested by regulatory authorities, which does not reflect clinical practice. However, repeated incobotulinumtoxinA injections (240 or 120 U; flexible intervals) provided sustained efficacy and were well tolerated, with no unexpected safety risks following repeated injections. The incidence of AEs was similar in subjects requiring repeated injections at shorter intervals (≤12 weeks) compared with those treated using longer intervals (>12 weeks).

The vital role of natural history studies in rare disease: insights from X-linked dystonia parkinsonism.

This scientific commentary refers to 'Establishing a natural history of X-linked dystonia parkinsonism', by Acuna et al. (https://doi.org/10.1093/braincomms/fcad106).

Rapid-onset dystonia-parkinsonism is associated with reduced cerebral blood flow without gray matter changes.

Purpose: Previous research showed discrete neuropathological changes associated with rapid-onset dystonia-parkinsonism (RDP) in brains from patients with an ATP1A3 variant, specifically in areas that mediate motor function. The purpose of this study was to determine if magnetic resonance imaging methodologies could identify differences between RDP patients and variant-negative controls in areas of the brain that mediate motor function in order to provide biomarkers for future treatment or prevention trials. Methods: Magnetic resonance imaging voxel-based morphometry and arterial spin labeling were used to measure gray matter volume and cerebral blood flow, respectively, in cortical motor areas, basal ganglia, thalamus, and cerebellum, in RDP patients with ATP1A3 variants (n = 19; mean age = 37 ± 14 years; 47% female) and variant-negative healthy controls (n = 11; mean age = 34 ± 19 years; 36% female). Results: We report age and sex-adjusted between group differences, with decreased cerebral blood flow among patients with ATP1A3 variants compared to variant-negative controls in the thalamus (p = 0.005, Bonferroni alpha level < 0.007 adjusted for regions). There were no statistically significant between-group differences for measures of gray matter volume. Conclusions: There is reduced cerebral blood flow within brain regions in patients with ATP1A3 variants within the thalamus. Additionally, the lack of corresponding gray matter volume differences may suggest an underlying functional etiology rather than structural abnormality.

ATP1A3 mutations in infants: a new rapid-onset dystonia-Parkinsonism phenotype characterized by motor delay and ataxia.

We report new clinical features of delayed motor development, hypotonia, and ataxia in two young children with mutations (R756H and D923N) in the ATP1A3 gene. In adults, mutations in ATP1A3 cause rapid-onset dystonia-Parkinsonism (RDP, DYT12) with abrupt onset of fixed dystonia. The parents and children were examined and videotaped, and samples were collected for mutation analysis. Case 1 presented with fluctuating spells of hypotonia, dysphagia, mutism, dystonia, and ataxia at 9 months. After three episodes of hypotonia, she developed ataxia, inability to speak or swallow, and eventual seizures. Case 2 presented with hypotonia at 14 months and pre-existing motor delay. At age 4 years, he had episodic slurred speech, followed by ataxia, drooling, and dysarthria. He remains mute. Both children had ATP1A3 gene mutations. To our knowledge, these are the earliest presentations of RDP, both with fluctuating features. Both children were initially misdiagnosed. RDP should be considered in children with discoordinated gait, and speech and swallowing difficulties.

Longitudinal goal attainment with integrated upper limb spasticity management including repeat injections of botulinum toxin A: Findings from the prospective, observational Upper Limb International Spasticity (ULIS-III) cohort study.

OBJECTIVE: To assess the longitudinal effects of integrated spasticity management incorporating repeated cycles of botulinum toxin A type A (BoNT-A) over 2 years. METHODS: The Upper Limb International Spasticity study was a prospective, observational, cohort study following adult patients over 2 years of integrated upper-limb spasticity management including repeat botulinum toxin (BoNT-A) treatment (any commercially-available product). RESULTS: A total of 1,004 participants from 14 countries were enrolled, of which 953 underwent ≥ 1 BoNT-A injection cycle (median 4 cycles) and had ≥ 1 goal attainment scaling assessment. Most participants (55.9-64.6% across cycles 1-6) saw a therapist after BoNT-A treatment; the most frequent therapy intervention was passive stretch (70.1-79.8% across cycles 1-6). Patients achieved their goals as expected over repeated cycles; mean cumulated goal attainment scaling T-score at 2 years was 49.5 (49.1, 49.9). Mean goal attainment scaling change scores of ≥ 10 were maintained across up to 7 cycles. Higher rates of goal achievement were seen for primary goals related to passive vs active function (86.6% vs 71.4% achievement). Standardized measures of spasticity, pain, involuntary movements, active and passive function improved significantly over the study. CONCLUSION: This large, international study provides evidence for benefit of repeated cycles of BoNT-A, over 2 years captured through person-centred goal attainment and standardized measures.

Assessing the effectiveness of upper-limb spasticity management using a structured approach to goal-setting and outcome measurement: First cycle results from the ULIS-III Study.

OBJECTIVE: To describe the utility of a structured approach to assessing effectiveness following injection with botulinum toxin-A alongside physical therapies, within the first cycle of the Upper Limb International Spasticity-III (ULIS-III) study. METHODS: ULIS-III (registered at clinicaltrials.gov as NCT02454803) is a large international, observation-al, longitudinal study of adults treated for upper-limb spasticity. It introduces novel methods for the structured evaluation of person-centred goal attainment alongside targeted standardized outcome measures: the Upper limb Spasticity Index, and the Upper Limb Spasticity Therapy Recording Schedule. RESULTS: A total of 953/1,004 enrolled patients (95%) completed cycle 1. Mean overall goal attainment scaling (GAS) T scores were 49.8 (95% confidence interval 49.2-50.3; 67.1% of patients met their primary goal, with highest achievement rates for goals related to involuntary movement, (75.6%) and range of movement (74.4%). Standardized measures of spasticity, pain, involuntary movements, active and passive function, all improved significantly over the treatment cycle. Overall, 59.7% of patients saw a therapist following botulinum toxin-A injection. Interventions varied, as expected, with the set treatment goals. After controlling for concomitant therapies using the upper limb spasticity therapy recording schedule, significant differences in injection intervals (p < 0.001) were seen between the commercially-available botulinum toxin-A agents. CONCLUSION: The results of this study confirm the utility of the Upper Limb Spasticity Index and Upper Limb Spasticity Therapy Recording Schedule as a structured approach to capturing goal-setting, therapy inputs and outcomes assessment.

Correction: Sustained functional benefits after a single set of injections with abobotulinumtoxinA using a 2-mL injection volume in adults with cervical dystonia: 12-week results from a randomized, double-blind, placebo-controlled phase 3b study.

[This corrects the article DOI: 10.1371/journal.pone.0245827.].

AbobotulinumtoxinA provides flexibility for the treatment of cervical dystonia with 500 U/1 mL and 500 U/2 mL dilutions.

INTRODUCTION: Cervical dystonia (CD) is a neurologic movement disorder with potentially disabling effects and significant impact on quality of life of those affected. AbobotulinumtoxinA (aboBoNT-A) was initially approved for a dilution of 500 U/1 mL and subsequently for a dilution of 500 U/2 mL, providing flexibility for clinicians to treat CD. Here, we explore the safety and efficacy of the 500 U/2 mL dilution versus 500 U/1 mL dilution of aboBoNT-A in a retrospective analysis based on published clinical trial data. METHODS: The safety and efficacy of aboBoNT-A in patients with CD was evaluated in three multicenter, double-blind, randomized, placebo-controlled trials and open-label extensions. Trials 1 (NCT00257660) and 2 (NCT00288509) evaluated the 500 U/1 mL dilution in 80 and 116 patients, respectively; Trial 3 (NCT01753310) evaluated the 500 U/2 mL dilution in 125 patients. RESULTS: Comparison of the adjusted mean difference in TWSTRS total scores at Week 4 from baseline for aboBoNT-A in Trial 1 (-6.0; 95% CI, -10.8, -1.3), Trial 2 (-8.8; 95% CI, -12.9, -4.7), and Trial 3 (-8.7; 95% CI, -13.2, -4.2) showed similar, significant improvements. Dysphagia and muscle weakness patterns were comparable across the three trials, indicating that an increased dilution of aboBoNT-A does not result in an increased risk of diffusion-related adverse events. CONCLUSION: The results of these trials show that aboBoNT-A is similarly efficacious using either dilution, with similar safety and tolerability across trials. Having the 500 U/1 mL and 500 U/2 mL dilution volumes available provides further flexibility in administration, benefiting patient care.

Sustained functional benefits after a single set of injections with abobotulinumtoxinA using a 2-mL injection volume in adults with cervical dystonia: 12-week results from a randomized, double-blind, placebo-controlled phase 3b study.

Cervical dystonia (CD) is primarily treated with botulinum toxin, at intervals of ≥ 12 weeks. We present efficacy, patient-reported outcomes (PROs), and safety in adults with CD at the last available visit after a single set of abobotulinumtoxinA (aboBoNT-A) injections versus placebo using 500 U in a 2-mL injection volume. In this 12-week, randomized, double-blind trial, patients were ≥ 18 years of age with primary idiopathic CD, had a Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score ≥ 20, and TWSTRS-Severity subscale score > 10 at baseline. Patients (N = 134) were randomized (2:1) to aboBoNT-A (n = 89) or placebo (n = 45), with aboBoNT-A patients treated with 500 units (U) if toxin-naïve, and 250 to 500 U based on previous onabotulinumtoxinA dose if non-naïve. Endpoints included total TWSTRS, Pain Numeric Rating Scale (NRS-Pain; 24-hour), Treatment Satisfaction Questionnaire for Medication, and other PROs for pain, depression, and global health. Results are for the intent-to-treat population, with "Week 12" (Wk12) comprising the last available post-baseline assessment (end-of-study or early withdrawal). Mean TWSTRS total scores improved from 42.5 at baseline to 35.4 at Wk12 with aboBoNT-A and 42.4 to 40.4 with placebo (treatment difference: -4.8; 95% confidence interval [CI]: -8.5, -1.1; p = 0.011). At Wk12, mean (95% CI) change from baseline in NRS-Pain was -1.0 (-1.59, -0.45) for aboBoNT-A and -0.2 (-0.96, 0.65) for placebo. AboBoNT-A demonstrated numeric improvements in other PROs. More aboBoNT-A-treated patients than patients receiving placebo reported being at least "somewhat satisfied" with treatment (60.4% vs 42.2%, respectively), symptom relief (57.0% vs 40.0%), and time for treatment to work (55.8% vs 33.3%). No new adverse events were reported. Results indicate that in patients with CD, treatment with aboBoNT-A using a 2-mL injection provided sustained improvement in the TWSTRS total score and patient-perceived benefits up to 12 weeks. Trial registration: Clinicaltrials.gov Identified: NCT01753310.