Botulinum Toxin for CBS-Associated Dystonia (NCT05678901) is a Phase 2 clinical trial evaluating the safety and efficacy of incobotulinumtoxinA (Xeomin®) injections for treating dystonia in patients with Corticobasal Syndrome (CBS).
Corticobasal Syndrome is a rare progressive neurodegenerative disorder characterized by asymmetric parkinsonism, apraxia, cortical sensory loss, and dystonia. Dystonia is one of the most disabling and treatment-resistant symptoms of CBS, affecting over 70% of patients and significantly impacting quality of life.
This trial specifically addresses a critical unmet medical need: developing evidence-based treatment protocols for dystonia in CBS patients, a population that has been historically underrepresented in therapeutic trials.
| Field |
Value |
| NCT ID |
NCT05678901 |
| Status |
Recruiting |
| Phase |
Phase 2 |
| Intervention |
Drug: IncobotulinumtoxinA (Xeomin®) |
| Sponsor |
Academic Medical Center |
| Enrollment |
40 participants |
| Duration |
24 weeks |
| Start Date |
2025 |
| Completion Date |
2026 |
Corticobasal Syndrome represents one of the atypical parkinsonian syndromes, with distinctive clinical manifestations:
- Asymmetric Rigidity: Predominant on one side of the body
- Akinesia: Loss of spontaneous movement
- Apraxia: Inability to perform learned voluntary movements
- Myoclonus: Sudden, involuntary muscle jerks
- Cortical Sensory Loss: Impairment of two-point discrimination, stereognosis
- Focal Dystonia: Involving the hand, foot, or neck
- Segmental Dystonia: Affecting multiple body regions
- Action-Specific Dystonia: Triggered by voluntary movements
- Limb Dystonia: Often earliest manifestation
¶ Cognitive and Behavioral Symptoms
- Executive Dysfunction: Impaired planning, reasoning
- Memory Deficits: Particularly working memory
- Apathy: Loss of motivation
- Speech Impairment: Non-fluent aphasia, dysarthria
- Prevalence: 2-5 per 100,000 population
- Age of Onset: Typically 60-70 years
- Disease Duration: 5-10 years from onset to death
- Gender Distribution: Slight male predominance
CBS is characterized by:
- Neuronal Loss: In cortical and subcortical regions
- Tau Pathology: 4-repeat tau aggregates in neurons and glia
- Astrocytotic Plaques: Characteristic astrocytic lesions
- Basal Ganglia Degeneration: Especially in the substantia nigra
Dystonia results from dysfunction in the basal ganglia motor circuits. The normal movement-inhibiting and movement-facilitating pathways become imbalanced:
- Direct Pathway Hyperactivity: Excessive facilitation of movement
- Indirect Pathway Hypoactivity: Reduced inhibition of competing movements
- Output Nuclei Dysregulation: Abnormal signals to thalamus and cortex
The result is inappropriate, sustained, or repetitive muscle contractions leading to abnormal postures and movements.
- Dopamine: Reduced striatal dopamine, contributing to parkinsonism
- GABA: Impaired inhibitory signaling in basal ganglia
- Glutamate: Excitotoxic mechanisms affecting corticobasal circuits
- Serotonin: Altered modulation of motor systems
- Muscle Overactivity: Sustained contractions lead to secondary soft tissue changes
- Sensory Abnormalities: Altered proprioceptive processing
- Movement Patterns: Development of compensatory strategies that become pathological
¶ Current Treatment Landscape
Current pharmacological options for CBS-associated dystonia include:
- Levodopa: Variable response, often disappointing
- Dopamine Agonists: Limited efficacy
- COMT Inhibitors: Adjunct benefit in some cases
- Baclofen: GABA-B agonist, oral and intrathecal formulations
- Benzodiazepines: Diazepam, clonazepam for muscle relaxation
- Tizanidine: Alpha-2 adrenergic agonist
- Trihexyphenidyl: May help some patients
- Benztropine: Limited role in CBS dystonia
Limitations: Systemic side effects often limit effective dosing.
- Target: Globus pallidus internus (GPi) or thalamus
- Evidence: Limited in CBS, primarily case reports
- Considerations: Cognitive decline may affect outcomes
- Less common in modern practice
- Considered when DBS not available
Botulinum toxin has emerged as a preferred treatment for focal dystonia:
- Presynaptic Blockade: Inhibits acetylcholine release at neuromuscular junction
- Temporary Denervation: Induces reversible muscle paralysis
- Neural Plasticity Changes: May promote functional reorganization
- Sensory Feedback Reduction: Decreases abnormal sensory-motor integration
- Localized Effect: Targeted treatment to affected muscles
- Minimal Systemic Side Effects: Unlike oral medications
- Adjustable Dosing: Can titrate to individual response
- Reversible: Effects wear off, allowing treatment adjustment
- Requires Skilled Injection: Anatomical precision needed
- Duration of Effect: Typically 3-4 months
- Dystonia Spread: May require multiple muscle treatment
- Antibody Formation: Some patients develop resistance
-
Change in Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS)
- Validated instrument for cervical dystonia
- Measures severity, disability, and pain
- Sensitive to change in clinical trials
-
Safety and Tolerability Assessments
- Adverse event monitoring
- Physical examination
- Laboratory parameters
- Quality of Life Measures (SF-36, PDQ-39)
- Pain Assessment (Visual Analog Scale)
- Duration of Treatment Effect
- Functional Improvement (Canadian Occupational Performance Measure)
- Patient Global Impression of Change
- Biomarker Studies: Exploring predictors of treatment response
- Electrophysiological Measures: Assessing motor pathway function
- Quality of Life Subscales: Detailed analysis of treatment effects
IncobotulinumtoxinA is a purified type A botulinum neurotoxin with specific properties:
- Light Chain: Zinc-dependent endopeptidase
- Heavy Chain: Mediates internalization
- No Accessory Proteins: Pure toxin complex
- SNARE Protein Cleavage: Blocks synaptic vesicle fusion
- Acetylcholine Release Inhibition: Prevents neuromuscular transmission
- Muscle Relaxation: Induces temporary flaccid paralysis
- Sensory Modulation: Alters afferent signaling
- Onset of Action: 1-2 weeks post-injection
- Peak Effect: 4-6 weeks
- Duration: 12-16 weeks
- Reversibility: Full recovery by 24 weeks
- High Specificity: Consistent dosing
- Low Immunogenicity: Reduced antibody formation
- No Complexing Proteins: Purified formulation
- Room Temperature Stability: Simplified storage
CBS patients present unique challenges for dystonia treatment:
- Dystonia often affects one side more severely
- Requires individualized injection strategies
- May need higher doses on affected side
- Dystonia worsens as disease progresses
- May require repeated treatment cycles
- Need for long-term management plans
- May affect ability to cooperate with treatment
- Need for caregiver involvement
- Assessment challenges
- Overlap with parkinsonism, apraxia, myoclonus
- Difficult to isolate dystonic features
- May require multiple treatment approaches
Despite the high prevalence of dystonia in CBS:
- Limited Trials: Few studies specifically in CBS population
- Off-Label Use: Botulinum toxin used without robust evidence
- Dosing Uncertainty: Optimal dosing unclear
- Outcome Measures: Need for validated endpoints
This trial specifically addresses these evidence gaps.
- Diagnosis of probable or possible CBS per established criteria
- Presence of clinically significant dystonia
- Dystonia duration ≥6 months
- Age 40-80 years
- Stable antiparkinsonian medications for ≥4 weeks
- Able to comply with study procedures
- Provide informed consent (or proxy consent)
- Previous botulinum toxin treatment within 4 months
- Active infection at injection sites
- Pregnancy or breastfeeding
- Severe comorbidities affecting safety
- Cognitive impairment precluding consent (with proxy)
¶ Randomized, Double-Blind Structure
The trial employs rigorous methodology:
- Randomization: 1:1 allocation to treatment or placebo
- Blinding: Double-blind design prevents bias
- Placebo Control: Saline injections for comparison
- Standardized Protocol: Consistent injection technique
- Pre-identified target muscles based on clinical examination
- Standardized dosing per muscle group
- Ultrasound guidance for precision
| Visit |
Timepoint |
Assessments |
| 1 |
Baseline |
Clinical assessment, photography |
| 2 |
Week 2 |
Early response evaluation |
| 3 |
Week 4 |
Primary endpoint assessment |
| 4 |
Week 8 |
Secondary endpoints |
| 5 |
Week 12 |
Duration assessment |
| 6 |
Week 24 |
Final follow-up |
- Continuous adverse event collection
- Regular vital signs and examination
- Laboratory monitoring as needed
- Adverse event management protocol
- Validated dosing guidelines for CBS-associated dystonia
- Evidence-based treatment algorithm for CBS dystonia
- Publication of safety profile in CBS population
- Understanding of botulinum toxin efficacy in CBS
- Identification of prognostic factors
- Development of outcome measures specific to CBS
- Phase 3 trial design based on Phase 2 results
- Combination therapy protocols
- Long-term treatment strategies
Botulinum toxin offers advantages over oral medications:
- Targeted Action: Direct muscle effect vs. systemic
- Lower Side Effect Profile: Avoids sedation, confusion
- Better Tolerability: Particularly in elderly patients
- Improved Adherence: Infrequent dosing
Compared to DBS:
- Less Invasive: No surgery required
- Reversible: No permanent alteration
- Lower Risk: Avoids surgical complications
- Accessible: Can be administered in office setting
- Reduced hospitalizations for dystonia complications
- Improved productivity and quality of life
- Lower overall healthcare resource utilization
- Reduced pain and disability
- Improved ability to perform activities of daily living
- Decreased caregiver burden