Comparison of botulinum toxin serotypes A and B for the treatment of cervical dystonia

Botulinum Toxin Therapy: A Comprehensive Review on Clinical and Pharmacological Insights

Background: Botulinum toxin (BoNT), produced by Clostridium botulinum, has transitioned from being a lethal neurotoxin to a versatile therapeutic agent. Its ability to inhibit neurotransmitter release by targeting Soluble N-ethylmaleimide-sensitive factor Attachment Protein Receptor (SNARE) proteins underpins its applications in treating conditions such as spasticity, dystonia, chronic pain, and overactive bladder. The clinical and pharmacological properties of BoNT have been extensively studied, with significant advancements in its therapeutic use, safety profile, and understanding of associated adverse effects. Objective: This comprehensive review aims to consolidate historical developments, molecular mechanisms, clinical applications, and challenges associated with BoNT, with a focus on expanding its therapeutic scope while ensuring safety and efficacy. Method: A narrative approach was used to analyze and synthesize insights from 155 references spanning experimental studies, clinical trials, and reviews. Key topics included BoNT's historical milestones, mechanisms of action, therapeutic applications, and adverse events. Findings: BoNT demonstrates remarkable efficacy in a wide range of medical and cosmetic applications. In movement disorders such as dystonia and spasticity, it reduces muscle overactivity and improves functional outcomes. In chronic pain management, including migraines and neuropathic pain, BoNT significantly alleviates symptoms by modulating neurotransmitter activity. Cosmetic use for conditions like glabellar lines and hyperhidrosis highlights its precision and safety when administered appropriately. For conditions like strabismus and blepharospasm, BoNT effectively restores muscle control, reducing involuntary contractions. In urological applications, BoNT has proven to be an effective therapy for overactive bladder, offering significant symptom relief in refractory cases. However, concerns about long-distance effects, where the toxin may spread beyond the injection site to affect distant muscles or systems, have been reported in certain high-dose or sensitive populations. These findings emphasize the importance of dose optimization and patient-specific approaches. Adverse effects such as localized pain, hematoma, dysphagia, and systemic effects, particularly in high-risk groups, underscore the need for careful monitoring. The development of immunogenicity, leading to neutralizing antibodies, remains a challenge that impacts long-term therapeutic efficacy. Emerging research on novel serotypes, including BoNT/X, and innovations in delivery mechanisms, offer promising avenues to address current limitations. Advances in optimizing dosing regimens and refining injection techniques have also contributed to minimizing complications and improving outcomes across diverse patient populations. Conclusions: BoNT remains a cornerstone in neurology and cosmetic medicine, with its therapeutic potential still expanding. The balance between efficacy and safety, driven by innovations in formulation and application, underscores the importance of continued research. Future directions should focus on minimizing adverse effects, reducing immunogenicity, and exploring novel indications to further enhance its clinical utility.

Efficacy Remaining at Time of Requested Re-Treatment for Cervical Dystonia: A Potential New Treatment Paradigm with DaxibotulinumtoxinA

The therapeutic efficacy remaining from prior treatments with botulinum toxins (BoNTs) when cervical dystonia (CD) patients prefer to be re-treated has not been well characterized. Here, we assessed the residual therapeutic efficacy of BoNT injections at the time of a patient-desired re-treatment. In pivotal trials for daxibotulinumtoxinA (DAXI) in CD, subjects could request re-treatment before returning to pre-treatment symptom levels (defined as ≤20% of peak efficacy remaining). In this post hoc analysis of the Phase 3 ASPEN-OLS trial, the median percent efficacy remaining (based on change in TWSTRS total score) was determined in subjects who requested re-injection before returning to pre-treatment symptoms. Dysphagia and muscle weakness were evaluated in patients requesting re-treatment with efficacy remaining, relative to those waiting to return to baseline. There were 264 (28.7% of 920 total treatments) patient requests for re-treatment before returning to pre-treatment status across the study. The median percent efficacy remaining at the time of requested re-injection was 45.5%, which corresponded to a median of 16.0 weeks (range 10.9-40.3) post-treatment. The rates of dysphagia (≤4.9%) and muscle weakness (≤6.8%) were low and were not significantly different in those who waited for return to pre-treatment symptom status versus subjects who requested re-injection with efficacy remaining. A significant proportion of CD patients wished to be re-treated with efficacy still remaining from prior BoNT injections as early symptoms re-emerged. With the overall clinical profile of DAXI, physicians can safely provide individualized treatment regimens based on the treatment goals or symptomatic needs of their patients.

An update on botulinum toxin treatment of painful diabetic neuropathy, post-traumatic painful neuropathy/neuralgia, post-herpetic neuralgia and occipital neuralgia

The literature in botulinum toxin treatment for painful diabetic neuropathy (PDN), post traumatic neuralgia (PTN), postherpetic neuralgia (PHN) and occipital neuralgia (ON) was reviewed up to Oct 1st, 2024. Using the efficacy criteria set forth by the Assessment and Guideline subcommittee of the American Academy of Neurology, the current levels of efficacy for these conditions could be designated as followings: PDN: B (probably effective, two class II study), PTN: A (effective, two class I studies); PHN: A (effective, two class I studies), ON: (undetermined due to lack of blinded investigations). Due to the small number of patients in these studies, proof of efficacy requires conduction of controlled and blinded studies in large cohorts of patients with longer follow ups. Future prospects of botulinum therapy for these pain disorders were discussed along with the advantages of this mode of treatment over the current modes of treatment.

A brief review of complex regional pain syndrome and current management

Complex regional pain syndrome (CRPS) is a debilitating chronic pain condition that, although exceedingly rare, carries a significant burden for the affected patient population. The complex and ambiguous pathophysiology of this condition further complicates clinical management and therapeutic interventions. Furthermore, being a diagnosis of exclusion requires a diligent workup to ensure an accurate diagnosis and subsequent targeted management. The development of the Budapest diagnostic criteria helped to consolidate existing definitions of CRPS but extensive work remains in identifying the underlying pathways. Currently, two distinct types are identified by the presence (CRPS type 1) or absence (CRPS type 2) of neuronal injury. Current management directed at this disease is broad and growing, ranging from non-invasive modalities such as physical and psychological therapy to more invasive techniques such as dorsal root ganglion stimulation and potentially amputation. Ideal therapeutic interventions are multimodal in nature to address the likely multifactorial pathological development of CRPS. Regardless, a significant need remains for continued studies to elucidate the pathways involved in developing CRPS as well as more robust clinical trials for various treatment modalities.

Dysphagia and Muscle Weakness Secondary to Botulinum Toxin Type A Treatment of Cervical Dystonia: A Drug Class Analysis of Prescribing Information

The first-line management of cervical dystonia (CD) symptoms is intramuscular injection of botulinum toxin type A (BoNTA). However, a comparison of safety among BoNTAs is difficult because, per regulatory authorities, units of BoNTA activity are not interchangeable. Dysphagia and muscle weakness are widely considered two key adverse events to monitor closely in the treatment of CD. This integrated analysis compared the safety of BoNTAs approved for CD in the US by evaluating relationships between the incidence of dysphagia and muscle weakness in prescribing information and the core neurotoxin content. Coefficients The coefficients of determination (R2) and trendlines were estimated via regression-based lines of best fit. Adverse drug reaction (ADR) rates were strongly correlated with core neurotoxin amounts for conventional BoNTAs (slope coefficients: dysphagia = 0.048, R2 = 0.74; muscle weakness = 0.096, R2 = 0.82). The published ADR rates at approved doses for conventional BoNTAs were higher compared with DaxibotulinumtoxinA (DAXI; DAXXIFY®, Revance Therapeutics, Inc., Nashville, TN, USA) by core neurotoxin content. The use of a core neurotoxin amount was found to be an effective method for comparing the safety of BoNTA products. Current clinical trials suggest that DAXI, a novel BoNTA formulation, provides a potentially wider safety margin compared with other approved BoNTAs for CD. The lower amount of core neurotoxin administered at approved doses compared with conventional BoNTAs may explain low on-target ADRs like muscle weakness, whereas reduced diffusion from the injection site is thought to be responsible for low off-target ADRs like dysphagia.

RimabotulinumtoxinB: An Update

BACKGROUND

Botulinum type-A toxin is a well established aesthetic and medical treatment. While the usage of type-B toxin is less common, there is a growing interest in using type-B toxin, especially in those who are treatment resistant.

OBJECTIVE

To evaluate the primary FDA-approved clinical applications of rimabotulinumtoxinB, along with established and emerging off-label clinical indications.

MATERIAL AND METHODS

Articles were reviewed from PubMed database and Food and Drug Adminstration guidelines.

RESULTS

Facial rhytids tend to use a higher conversion ratio between type A and type B toxin, due to type B toxin's weaker affinity to muscles and higher affinity for sweat glands. Specially, a 1:100 to 1:50 ratio was utilized for glabellar rhytids, a 1:25 to 1:50 ratio for periocular rhytids, a 1:50 to 1:66.6 ratio for cervical dystonia, a 1:20 to 1:50 ratio for hyperhidrosis, and a 1:25 to 30 ratio for sialorrhea.

CONCLUSION

Type B toxin has demonstrated its safety and efficacy in treating facial rhytids, cervical dystonia, sialorrhea and hyperhidrosis, with potential for novel applications under investigation. Regardless of injection location and clinical applications, dry mouth and dysphagia remained the most common side effects. Across all indications, type B toxin appeared to have a faster onset of action, a dose-dependent clinical duration, and a dose-dependent adverse effect profile.

Duration of botulinum toxin efficacy in cervical dystonia clinical trials: A scoping review

INTRODUCTION

Botulinum toxin (BoNT) is first-line treatment for cervical dystonia (CD). Treatment of CD with BoNT usually requires injections every 3-4 months for as long as symptoms persist, which can be for the lifetime of the individual. Duration of BoNT effect can impact quality of life since it is important that efficacy is maintained throughout an injection cycle to avoid fluctuations of effect after each injection. There is currently no consensus on how to assess duration of BoNT effect in patients with CD.

METHODS

A scoping review was conducted to summarize the available evidence from phase 3 clinical trials of BoNT in CD and on the interpretation of the reported duration of effect. The available evidence was analyzed in the context of clinical experience and real-world treatment practices of CD.

RESULTS

Methods for estimating duration of effect varied across publications; most were based on artificial constructs developed for clinical trials (time until a pre-specified efficacy endpoint was reached) and are not appropriate to apply in clinical practice. Clinical trial outcomes in CD were not objectively evaluated, and did not prioritize patients' needs or focus on factors that impact patients' daily living activities and quality of life.

CONCLUSION

Better evidence and consistency of reporting for duration of effect for BoNT in CD is needed to help guide clinicians on when reinjection is likely to be required. The goal should be to keep patients as symptom-free as possible with flexible reinjection intervals tailored to individual needs.

Current use of neurotoxins for alleviating symptoms of cervical dystonia

INTRODUCTION

Cervical dystonia (CD) causes involuntary movements and postures of the head, neck, and shoulders, as well as nonmotor symptoms including pain, mood, and sleep dysfunction, and impacts quality of life. The first-line treatment for CD is botulinum neurotoxin (BoNT) injections.

AREAS COVERED

The clinical presentation and diagnosis of CD, as well as where BoNT resides in the treatment landscape, is reviewed first. Next, the mechanism of action and the pharmacological differences in the available preparations of BoNT products are explained. The evidence base for motor and nonmotor efficacy and safety of the available BoNT formulations is reviewed, with attention to duration of benefit as a driver of patient satisfaction. Practical determinants of BoNT efficacy are reviewed including muscle selection, accurate muscle injection, factors related to poor or deteriorating response, and immunogenicity.

EXPERT OPINION

BoNT represents a significant advancement in the treatment of CD. More accurate diagnosis, muscle selection and targeting, and dosing can improve outcomes with existing BoNT formulations. Further refinement of BoNT potency, duration of action, safety, and immunogenicity will help reduce unmet needs in the magnitude and duration of benefit. Additional validation of DBS and MRI-guided focused ultrasound may expand options for patients with toxin nonresponse.

Update on Non-Interchangeability of Botulinum Neurotoxin Products

The growing use of botulinum neurotoxins (BoNTs) for medical and aesthetic purposes has led to the development and marketing of an increasing number of BoNT products. Given that BoNTs are biological medications, their characteristics are heavily influenced by their manufacturing methods, leading to unique products with distinct clinical characteristics. The manufacturing and formulation processes for each BoNT are proprietary, including the potency determination of reference standards and other features of the assays used to measure unit potency. As a result of these differences, units of BoNT products are not interchangeable or convertible using dose ratios. The intrinsic, product-level differences among BoNTs are compounded by differences in the injected tissues, which are innervated by different nerve fiber types (e.g., motor, sensory, and/or autonomic nerves) and require unique dosing and injection sites that are particularly evident when treating complex therapeutic and aesthetic conditions. It is also difficult to compare across studies due to inherent differences in patient populations and trial methods, necessitating attention to study details underlying each outcome reported. Ultimately, each BoNT possesses a unique clinical profile for which unit doses and injection paradigms must be determined individually for each indication. This practice will help minimize unexpected adverse events and maximize efficacy, duration, and patient satisfaction. With this approach, BoNT is poised to continue as a unique tool for achieving individual goals for an increasing number of medical and aesthetic indications.

Myofascial pain - A major player in musculoskeletal pain

Myofascial pain is a soft tissue pain syndrome with local and referred musculoskeletal pain arising from trigger points. Myofascial pain and myofascial pain syndromes are among some of the most common acute and chronic pain conditions. Myofascial pain can exist independently of other pain generators or can coexist with or is secondary to other acute and chronic painful musculoskeletal conditions. Myofascial pain is most effectively treated with a multimodal treatment plan including injection therapy (known as trigger point injections, physical therapy, postural or ergonomic correction, and treatment of underlying musculoskeletal pain generators. The objectives of this review are to outline the prevalence of myofascial pain, describe the known pathophysiology of myofascial pain and trigger points, discuss the clinical presentation of myofascial pain, and present evidence-based best practices for pharmacologic, non-pharmacologic, and interventional treatments for myofascial pain.

Therapeutic Benefit of Sensory Trick in Cervical Dystonia

Background

Sensory tricks (STs) are voluntary maneuvers that dampen the abnormal movement in cervical dystonia (CD).

Objectives

To investigate the effect of ST on CD severity and treatment.

Methods

Data on 1039 individuals with a modified Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score were extracted from the CD Patient Registry for Observation of OnabotulinumtoxinA (onabotA) Efficacy study. Univariate and multivariate models evaluated the direct and indirect impact of ST on CD severity and treatment, while controlling for confounds.

Results

Complete ST was associated with a 10% lower mean onabotA dose. Absence of complete ST was associated with a higher onabotA dose after controlling for dystonia severity (OR = 1.37, P = 0.04). ST moderated the relationship between dystonia severity and toxin dose (β = -0.16, P = 0.02).

Conclusions

ST is related to lower CD severity and toxin dose. It may have a direct effect on lowering toxin dose, independent of CD severity.

A look at the future-new BoNTs and delivery systems in development: What it could mean in the clinic

Despite the expanding clinical utility of botulinum neurotoxins, there remain problems to be solved for attaining the best outcome. The efficacy and safety need to be reconsidered for commercially available preparations all derived from subtype A1 or B1. Emerging new toxins include A2 or A6 subtypes or engineered toxins with less spread, more potency, longer durations of action, less antigenicity and better safety profile than currently used preparations. Non-toxic BoNTs with a few amino acid replacements of the light chain (LC) may have a role as a drug-delivery system if the toxicity is abolished entirely. At present, efficacy of these BoNTs in animal botulism was demonstrated.

Immunogenicity of DaxibotulinumtoxinA for Injection in Glabellar Lines

DaxibotulinumtoxinA-lanm for injection (DAXI), a novel botulinum toxin type A formulation, contains a purified 150-kD core neurotoxin (daxibotulinumtoxinA) and proprietary stabilizing peptide (RTP004), and is approved for glabellar line treatment. As with any biologic product, DAXI may potentially be immunogenic and elicit unwanted antibody formation, possibly resulting in partial or complete treatment failure. The immunogenicity of DAXI was assessed in 2 double-blind, placebo-controlled, single-dose studies and an open-label safety study of up to 3 repeat treatments. Of the 2737 evaluable patients, none developed neutralizing antibodies to daxibotulinumtoxinA and 0.8% developed treatment-related nonneutralizing anti-daxibotulinumtoxinA-binding antibodies. Of evaluable patients exposed to RTP004 with either DAXI or placebo, 1.3% developed treatment-related anti-RTP004-binding antibodies, which were mostly transient. No patient developed binding antibodies to both daxibotulinumtoxinA and RTP004. All patients with treatment-related binding antibodies to daxibotulinumtoxinA or RTP004 achieved a clinical response (none or mild glabellar line severity) at Week 4 following each DAXI treatment cycle. The duration of clinical response was not different between treatment cycles when antibodies were detected vs when they were absent. Although the analysis population was small compared to the number of patients likely to receive repeated treatment in clinical practice, these results suggest that DAXI administration at the approved glabellar lines dose has low immunogenic potential and that nonneutralizing antibodies to daxibotulinumtoxinA or RTP004 occur infrequently and often transiently, and have no impact on clinical efficacy, safety, or duration of action. Real-world data encompassing larger numbers of patients is needed to substantiate these results.

LEVEL OF EVIDENCE: 3

Treatment of neurogenic detrusor overactivity and overactive bladder with Botox (onabotulinumtoxinA): Development, insights, and impact

Neurogenic detrusor overactivity (NDO) is a complication of multiple sclerosis, spinal cord injury (SCI), stroke, head injury, and other conditions characterized by damage to the upper motor neuronal system. NDO often leads to high bladder pressure that may cause upper urinary tract damage and urinary incontinence (UI). Prior to the use of onabotulinumtoxinA, oral anticholinergics and surgical augmentation cystoplasty were the treatment options. Overactive bladder (OAB) is non-neurogenic and affects a much larger population than NDO. Both NDO and OAB negatively impact patients' quality of life (QOL) and confer high health care utilization burdens. Early positive results from pioneering investigators who injected onabotulinumtoxinA into the detrusor of patients with SCI caught the interest of Allergan, which then initiated collaborative clinical trials that resulted in FDA approval of onabotulinumtoxinA 200U in 2011 for NDO and 100U in 2013 for patients with OAB who inadequately respond to or are intolerant of an anticholinergic. These randomized, double-blind, placebo-controlled trials for NDO showed significant improvements in UI episodes, urodynamic parameters, and QOL; the most frequent adverse events were urinary tract infection (UTI) and urinary retention. Similarly, randomized, double-blind, placebo-controlled trials of onabotulinumtoxinA 100U for OAB found significant improvements in UI episodes, treatment benefit, and QOL; UTI and dysuria were the most common adverse events. Long-term studies in NDO and OAB showed sustained effectiveness and safety with repeat injections of onabotulinumtoxinA, the use of which has profoundly improved the QOL of patients failing anticholinergic therapy and has expanded the utilization of onabotulinumtoxinA into smooth muscle.

A technology evaluation of the atypical use of a CPP-containing peptide in the formulation and performance of a clinical botulinum toxin product

INTRODUCTION

Cell-penetrating peptides (CPPs), are small peptides that facilitate cytosolic access and, thus, transport of therapeutic macromolecules to intracellular sites when conjugated to cargo proteins. As with all new delivery platforms, clinical development of CPP-containing therapeutics has faced considerable challenges.

AREAS COVERED

RTP004 is a novel, 35-amino acid, bi-CPP-containing excipient that binds noncovalently with its cargo (botulinum toxin type A) rather than conjugated as a fusion protein. An RTP004-containing neurotoxin formulation, daxibotulinumtoxinA-lanm for injection (DAXI), has recently been approved by the FDA. The formulation and pharmacological characteristics of RTP004 and the efficacy and safety of the RTP004-neurotoxin formulation are discussed.

EXPERT OPINION

RTP004 is a highly positively charged lysine- and arginine-rich structure that provides formulation stability, preventing self-aggregation of the cargo protein and adsorption to container surfaces. The presence of RTP004 in the formulation also appears to increase presynaptic binding of the neurotoxin, reduces post-injection diffusion, and thus facilitates an increase in the cleavage of the intracellular substrate for the botulinum toxin, likely through enhanced cellular uptake. The RTP004-neurotoxin formulation is the first CPP-containing product approved for clinical use. The potential for RTP004 to facilitate other therapeutic cargo molecules requires further research.

Botulinum neurotoxins: Future innovations

Botulinum neurotoxins (BoNTs) are multi-domain proteins whose potent and selective actions on nerve endings have led to innovations in both basic and clinical science. The various BoNT domains are responsible for binding to gangliosides and proteins associated with nerve cell membranes, internalization into the cell, and cleavage of one or more SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) proteins necessary for vesicle docking and fusion. Novel modifications to BoNT molecules, such as the creation of chimeras, helped identify the protein domains responsible for various aspects of BoNT action, such as localized effects. Other molecular modifications have been introduced in attempts to increase the specificity of BoNTs for autonomic or sensory neurons, with the ultimate goal of optimizing therapeutic selectivity. This research, in turn, has led to the development of BoNT-based proteins that can target non-SNARE substrates such as phosphatase and tensin homolog (PTEN). Still others are developing different BoNT serotypes, subtypes, or variants that are longer- or shorter-acting or have faster onset for various clinical purposes. New formulations of BoNTs that provide convenience for both patients and physicians are under investigation. Novel clinical uses are being evaluated for onabotulinumtoxinA, including in the prevention of post-operative atrial fibrillation. All these innovations capitalize on the unique properties of BoNTs, which continue to intrigue scientists and clinicians across numerous fields of study.

Clinical Immunogenicity of DaxibotulinumtoxinA for Injection in Glabellar Lines: Pooled Data from the SAKURA Phase 3 Trials

DaxibotulinumtoxinA for Injection (DAXI) is a novel botulinum toxin type A product containing daxibotulinumtoxinA with a stabilizing excipient peptide (RTP004). DAXI immunogenicity was assessed in three phase 3 glabellar line studies (two placebo-controlled, single-dose studies and an open-label repeat-dose safety study). Binding antibodies to daxibotulinumtoxinA and RTP004 were detected by validated ELISAs. Samples positive for daxibotulinumtoxinA-binding antibodies were evaluated further for titer and neutralizing antibodies by mouse protection assay. Overall, 2786 subjects received DAXI and 2823 subjects were exposed to RTP004 as DAXI (n = 2786) or placebo (n = 37). Treatment-related anti-daxibotulinumtoxinA binding antibodies were detected in 21 of 2737 evaluable subjects (0.8%). No subject developed neutralizing antibodies. Treatment-related anti-RTP004 binding antibodies were detected in 35 (1.3%) of 2772 evaluable subjects. Binding antibodies were generally transient, of low titer (<1:200), and no subject had binding antibodies to both daxibotulinumtoxinA and RTP004. All subjects with treatment-induced binding antibodies to daxibotulinumtoxinA or RTP004 achieved none or mild glabellar line severity at Week 4 following each DAXI cycle, indicating no impact on DAXI efficacy. No subjects with binding antibodies to daxibotulinumtoxinA or RTP004 reported immune-related adverse events. This evaluation of anti-drug antibody formation with DAXI shows low rates of antibody formation to both daxibotulinumtoxinA and RTP004.

Botulinum toxin for motor disorders

Botulinum neurotoxins are a group of biological toxins produced by the gram-negative bacteria Clostridium botulinum. After intramuscular injection, they produce dose-related muscle relaxation, which has proven useful in the treatment of a large number of motor and movement disorders. In this chapter, we discuss the utility of botulinum toxin treatment in three major and common medical conditions related to the dysfunction of the motor system, namely dystonia, tremor, and spasticity. A summary of the existing literature is provided along with different techniques of injection including those recommended by the authors.

Long-term efficacy with deep brain stimulation of the globus pallidus internus in cervical dystonia: a retrospective monocentric study

BACKGROUND

Cervical dystonia (CD) is characterized by involuntary contractions of the cervical muscles. Data on long-term effectiveness of deep brain stimulation (DBS) are rare. The aim of this study was to evaluate the longitudinal ten years treatment efficacy of DBS in the globus pallidus internus (GPI).

METHODS

A retrospective single-center data analysis was performed on patients with idiopathic CD, who were treated with GPI DBS for at least 10 years. TWSTR severity score and individual sub-items were compared between pre and post DBS surgery (n = 15) over time.

RESULTS

There was a significant and persistent positive effect regarding the severity of TWSTRS between the conditions immediately before and 1, 5, and 10 years after establishment of GPI DBS (mean difference: 6.6-7 ± 1.6). Patients with increasing CD complexity showed a poorer response to established treatment forms, such as injection of botulinum toxin and were thus DBS candidates. Especially a predominant torticollis was significantly improved by DBS.

CONCLUSION

GPI DBS is an effective procedure especially in severely affected patients with a positive 10-year outcome. It should be considered in more complex CD-forms or predominant torticollis.

OnabotulinumtoxinA Dosing, Disease Severity, and Treatment Benefit in Patients With Cervical Dystonia: A Cohort Analysis From CD PROBE

Introduction

The Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE) study (ClinicalTrials.gov identifier: NCT00836017), a multicenter, prospective, observational registry, was designed to identify real-world practices and outcomes for patients with cervical dystonia (CD) treated with onabotulinumtoxinA (onabotA). This secondary analysis from CD PROBE aims to determine the impact of presentation subtype on onabotA utilization and CD severity.

Materials and Methods

The study cohort includes those who completed all 3 treatments, 4 office visits, and had data recorded for all assessments. Patient outcomes were assessed with the Cervical Dystonia Impact Profile (CDIP-58), Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), and determination of CD severity. Treatment interval, dose, and adverse events (AEs) were also recorded. Data were stratified according to prior exposure to botulinum toxins (BoNTs) and analyzed with descriptive statistics.

Results

Torticollis was the most common presentation subtype in the study cohort (N = 350); the proportion of patients with torticollis was highest in those with severe disease. At each treatment, between 40.7 and 65.2% of those categorized as severe shifted to moderate or mild severity after treatment. Sustained improvements in CDIP-58 and TWSTRS were observed regardless of prior exposure to BoNTs. Dosing of onabotA generally increased from injection 1 to injection 3 and tended to be lower for patients naïve to BoNT. Median time interval between injections for the study cohort was 94.0 to 97.5 days. The most common AEs (dysphagia, muscular weakness) and injection intervals were similar between naïve vs. non-naïve patients; there were no serious treatment-related AEs.

Conclusions

This secondary cohort analysis from CD PROBE demonstrates that three repeat treatments with onabotA at intervals consistent with labeling attenuated disease severity and neck pain, resulting in sustained improvements in physician- and patient-reported outcomes. No new safety signals were identified.

Cell-Penetrating Botulinum Neurotoxin Type A With Improved Cellular Uptake and Therapeutic Index

Botulinum neurotoxin serotype A (BoNTA) is widely used for treating neuromuscular disorders. Despite of the various marketed products, BoNTA is known to have small therapeutic index ranging from 5 to 15. In the present study, we designed and characterized engineered BoNTA proteins with fusion of cell-penetrating peptides (CPPs). We have shown that CPPs, particularly a recently reported zinc finger protein could improve the cellular uptake and intramuscular therapeutic index of BoNTA. Our study has shed the light on developing next-generation neuromuscular modulators using CPP fusion.

Efficacy of botulinum toxin type B (rimabotulinumtoxinB) in patients with cervical dystonia previously treated with botulinum toxin type A: A post-marketing observational study in Japan

To date, efficacy data on botulinum toxin type B (rimabotulinumtoxinB) in patients with cervical dystonia (CD) previously treated with botulinum toxin type A in a large population are lacking; thus, we aimed to evaluate type B efficacy in this patient population. In a post-marketing observational cohort study, 150 patients previously treated with botulinum toxin type A were enrolled, of whom 138 were followed up for 1 year after the initial type B injection. Final observation data were available for 122 patients. Efficacy was evaluated using the Toronto Western Spasmodic Torticollis Rating Scale. Total score improved from 39.9 at baseline to 34.3 at 4 weeks after the first injection, and pain score improved from 8.9 to 7.9. Improvements were maintained through six further injections in two subpopulations: patients who showed resistance to botulinum toxin type A and patients who were not type A resistant but switched to type B. For a number of patients, even low doses (<5000 units) of botulinum toxin type B demonstrated efficacy. These findings support the efficacy of botulinum toxin type B in clinical settings for the management of CD symptoms, including pain, even at low doses, regardless of the patient's botulinum toxin type A resistance status.

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Botulinum toxin type B improved cervical dystonia symptoms and pain after 4 weeks.

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Botulinum toxin type B was effective even at low doses (<5000 units).

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The efficacy of toxin type B is not affected by toxin type A resistance status.

Overview of DaxibotulinumtoxinA for Injection: A Novel Formulation of Botulinum Toxin Type A

Botulinum toxin type A (BoNTA) products are widely used for therapeutic and aesthetic indications, but there is a need for longer-lasting treatments that maintain symptom relief between injections and reduce the frequency of re-treatment. DaxibotulinumtoxinA for Injection (DAXI) is a novel BoNTA product containing highly purified 150-kDa core neurotoxin and is the first to be formulated with a proprietary stabilizing excipient peptide (RTP004) instead of human serum albumin. The positively charged RTP004 has been shown to enhance binding of the neurotoxin to neuronal surfaces, which may enhance the likelihood of neurotoxin internalization. DAXI produces robust, extended efficacy across both aesthetic and therapeutic indications. In an extensive glabellar lines clinical program, DAXI showed a high degree of efficacy, a consistent median time to loss of none or mild glabellar line severity of 24 weeks, and median time until return to baseline of up to 28 weeks. In adults with cervical dystonia, DAXI at 125 U and 250 U significantly improved Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total scores, with a median duration of efficacy of 24 and 20 weeks, respectively, which compares favorably with the 12–14 weeks’ duration reported for approved BoNTA products. Overall, DAXI was well tolerated, and the consistent extended duration of effect suggests that DAXI has the potential to improve the management of both aesthetic and therapeutic conditions.

Botulinum toxin is used to block the nerve signals that cause muscles to contract. Products containing botulinum toxin are commonly given by injection to treat muscle spasms (such as cervical dystonia, a painful condition where the neck muscles contract involuntarily) and for cosmetic treatment of frown lines. However, the effects of the currently approved botulinum toxin products typically wear off about 3–4 months after injection and so the injections must be repeated regularly. A new product called DAXI (DaxibotulinumtoxinA for Injection) has been developed. In this product, the botulinum toxin is formulated with a unique protein (called RTP004) that has been designed to help deliver the botulinum toxin to the nerve cells. Research suggests that the RTP004 protein in DAXI adheres the botulinum toxin to the nerves close to the injection site, potentially making its effect last longer. To date, DAXI has been studied in over 3800 patients. The studies have shown that DAXI is effective for treating neck spasms (cervical dystonia) and for reducing the appearance of frown lines. Importantly, the effects of DAXI lasted up to 6 months, which is longer than seen with other botulinum toxin products. The side effects seen with DAXI are consistent in nature and frequency with those seen with other botulinum toxin products. These findings suggest that DAXI can improve both medical and cosmetic treatments due to its longer-lasting effect.

A consensus statement on the use of botulinum toxin in pediatric patients

Botulinum toxin has been used in medicine for the past 30 years. However, there continues to be controversy about the appropriate uses and dosing, especially in the pediatric population. A panel of nine pediatric physiatrists from different regions and previous training programs in the United States were nominated based on institutional reputation and botulinum toxin (BoNT) experience. Based on a review of the current literature, the goal was to provide the rationale for recommendations on the administration of BoNT in the pediatric population. The goal was not only to review safety, dosing, and injection techniques but also to develop a consensus on the appropriate uses in the pediatric population. In addition to upper and lower limb spasticity, the consensus also provides recommendations for congenital muscular torticollis, cervical dystonia, sialorrhea, and brachial plexus palsies.

Botulinum Toxin in Movement Disorders: An Update

Since its initial approval in 1989 by the US Food and Drug Administration for the treatment of blepharospasm and other facial spasms, botulinum toxin (BoNT) has evolved into a therapeutic modality for a variety of neurological and non-neurological disorders. With respect to neurologic movement disorders, BoNT has been reported to be effective for the treatment of dystonia, bruxism, tremors, tics, myoclonus, restless legs syndrome, tardive dyskinesia, and a variety of symptoms associated with Parkinson's disease. More recently, research with BoNT has expanded beyond its use as a powerful muscle relaxant and a peripherally active drug to its potential central nervous system applications in the treatment of neurodegenerative disorders. Although BoNT is the most potent biologic toxin, when it is administered by knowledgeable and experienced clinicians, it is one of the safest therapeutic agents in clinical use. The primary aim of this article is to provide an update on recent advances in BoNT research with a focus on novel applications in the treatment of movement disorders. This comprehensive review of the literature provides a critical review of evidence-based clinical trials and highlights recent innovative pilot studies.

Transient Improvement after Switch to Low Doses of RimabotulinumtoxinB in Patients Resistant to AbobotulinumtoxinA

Botulinum toxin type B (BoNT/B) has been recommended as an alternative for patients who have become resistant to botulinum toxin type A (BoNT/A). This study aimed to compare the clinical effect, within a patient, of four injections with low doses of rimabotulinumtoxinB with the effect of the preceding abobotulinumtoxinA (aboBoNT/A) injections. In 17 patients with cervical dystonia (CD) who had become resistant to aboBoNT/A, the clinical effect of the first four rimabotulinumtoxinB (rimaBoNT/B) injections was compared to the effect of the first four aboBoNT/A injections using a global assessment scale and the TSUI score. After the first two BoNT/B injections, all 17 patients responded well and to a similar extent as to the first two BoNT/A injections, but with more side effects such as dry mouth and constipation. After the next BoNT/B injection, the improvement started to decline. The response to the fourth BoNT/B injection was significant (p < 0.048) lower than the fourth BoNT/A injection. Only three patients developed a complete secondary treatment failure (CSTF) and five patients a partial secondary treatment failure (PSTF) after four BoNT/B injections. In nine patients, the usual response persisted. With the use of low rimaBoNT/B doses, the induction of CSTF and PSTF to BoNT/B could not be avoided but was delayed in comparison to the use of higher doses. In contrast to aboBoNT/A injections, PSTF and CSTF occurred much earlier, although low doses of rimaBoNT/B had been applied.

Safety and Efficacy of RimabotulinumtoxinB for Treatment of Sialorrhea in Adults: A Randomized Clinical Trial

Question

Are rimabotulinumtoxinB injections safe and effective for management of sialorrhea in adults?

Findings

In this randomized clinical trial of 187 adults with sialorrhea, rimabotulinumtoxinB injections (2500 U and 3500 U) appeared to statistically significantly reduce sialorrhea vs placebo (treatment effect, −0.30 for both doses vs placebo, P < .001). Therapeutic benefits were seen as early as 1 week after injection and persisted for 11 to 15 weeks.

Meaning

RimabotulinumtoxinB is a safe, effective, and well-tolerated treatment for sialorrhea in adults.

Importance

RimabotulinumtoxinB (RIMA) may be preferable as an anti-sialorrhea treatment compared with current oral anticholinergic drugs in people with neurological disorders.

Objective

To assess the safety, efficacy, and tolerability of RIMA injections for the treatment of sialorrhea in adults.

Design, Setting, and Participants

This randomized, parallel, double-blind, placebo-controlled clinical trial of RIMA 2500 U and 3500 U was conducted from November 14, 2013, to January 23, 2017. A total of 249 adult patients with troublesome sialorrhea secondary to any disorder or cause were screened. Of them, 13 refused further participation in the study or were lost to follow-up and 49 did not fulfill the criteria for participation; 187 were ultimately enrolled. Patients had to have a minimum unstimulated salivary flow rate (USFR) of 0.2 g/min and a minimum Drooling Frequency and Severity Scale score of 4.

Exposures

Patients were randomized 1:1:1 to RIMA, 2500 U (n = 63); RIMA, 3500 U (n = 64); or placebo (n = 60).

Main Outcomes and Measures

Primary outcomes were the change in USFR from baseline to week 4 and the Clinical Global Impression of Change (CGI-C) at week 4. The CGI-C scores were recorded on a 7-point scale ranging from very much improved to very much worse. Adverse events were recorded throughout the trial period.

Results

Of 187 patients enrolled (147 men [78.6%]; mean [SD] age, 63.9 [13.3] years), 122 patients had Parkinson disease (65.2%), 13 (7.0%) were stroke survivors, 12 had amyotrophic lateral sclerosis (6.4%), 6 had medication-induced sialorrhea (3.2%), 4 had adult cerebral palsy (2.1%), and 30 had sialorrhea owing to other causes (16.0%). A total of 176 completed the study. Treatment with both doses of RIMA significantly reduced USFR at week 4 vs placebo (mean treatment difference, −0.30 g/min [95% CI, −0.39 to −0.21] for both doses vs placebo, P < .001). The CGI-C scores were statistically significantly improved at week 4 for both treatment groups vs placebo (−1.21 [95% CI, −1.56 to −0.87] for 2500 U, −1.14 [95% CI, −1.49 to −0.80] for 3500 U, both P < .001). Treatment benefits were seen as early as 1 week after injection and were maintained over the treatment cycle of approximately 13 weeks. The RIMA injections were well tolerated compared with placebo. The most common adverse events were self-limited mild to moderate dry mouth, dysphagia, and dental caries.

Conclusions and Relevance

Treatment with RIMA (2500 U and 3500 U) in adults was well tolerated and reduced sialorrhea, with the onset of the effect at 1 week after the injection. These data support the clinical use of RIMA in the management of sialorrhea in adults.

Trial Registration

ClinicalTrials.gov Identifier: NCT01994109

Frequency and risk factors of antibody-induced secondary failure of botulinum neurotoxin therapy

Objective

To investigate the risk factors of neutralizing antibody (NAB)–induced complete secondary treatment failure (cSTF) during long-term botulinum neurotoxin (BoNT) treatment in various neurologic indications.

Methods

This monocenter retrospective cohort study analyzed the data of 471 patients started on BoNT therapy between 1995 and 2015. Blood samples of 173 patients were investigated for NABs using the mouse hemidiaphragm test (93 with suspected therapy failure, 80 prospective study participants). The frequency of NAB-cSTF was assessed for various indications: hemifacial spasm, blepharospasm, cervical dystonia, other dystonia, and spasticity. A priori defined potential risk factors for NAB-cSTF were evaluated, and a stepwise binary logistic regression analysis was performed to identify independent risk factors.

Results

Treatment duration was 9.8 ± 6.2 years (range, 0.5–30 years; adherence, 70.6%) and number of treatment cycles 31.2 ± 22.5 (3–112). Twenty-eight of 471 patients (5.9%) had NAB-cSTF at earliest after 3 and at latest after 103 treatment cycles. None of the 49 patients treated exclusively with incobotulinumtoxinA over 8.4 ± 4.2 (1–14) years developed NAB-cSTF. Independent risk factors for NAB-cSTF were high BoNT dose per treatment, switching between onabotulinumtoxinA and other BoNT formulations (except for switching to incobotulinumtoxinA), and treatment of neck muscles.

Conclusions

We present a follow-up study with the longest duration to date on the incidence of NAB-cSTF in patients treated with various BoNT formulations, including incobotulinumtoxinA. Whereas the overall risk of NAB-cSTF is low across indications and BoNT formulations, our findings underpin the recommendations to use the lowest possible dose particularly in cervical dystonia, and to avoid unnecessary switching between different formulations.

Sore throat as a side effect of abobotulinum toxin A injection for upper limb spasticity after stroke: A case report

Despite sore throat exists in the product characteristics of abobotulinum toxin A as one of the side effects, no available reports of sore throat after abobotulinum toxin A injection for adult upper limb spasticity could be found in the literature to guide physicians for the management. Herein, we report a case of poststroke spasticity who develop sore throat immediately after abobotulinum toxin A (Dysport®) injection of forearm muscles which completely resolved after observation for eight hours. This case report highlights a rare side effect of abobotulinum toxin A and provides information regarding the follow-up process of side effects which would guide physicians for the management.

Characterization of a membrane binding loop leads to engineering botulinum neurotoxin B with improved therapeutic efficacy

Botulinum neurotoxins (BoNTs) are a family of bacterial toxins with seven major serotypes (BoNT/A–G). The ability of these toxins to target and bind to motor nerve terminals is a key factor determining their potency and efficacy. Among these toxins, BoNT/B is one of the two types approved for medical and cosmetic uses. Besides binding to well-established receptors, an extended loop in the C-terminal receptor-binding domain (H_C) of BoNT/B (H_C/B) has been proposed to also contribute to toxin binding to neurons by interacting with lipid membranes (termed lipid-binding loop [LBL]). Analogous loops exist in the H_Cs of BoNT/C, D, G, and a chimeric toxin DC. However, it has been challenging to detect and characterize binding of LBLs to lipid membranes. Here, using the nanodisc system and biolayer interferometry assays, we find that H_C/DC, C, and G, but not H_C/B and H_C/D, are capable of binding to receptor-free lipids directly, with H_C/DC having the highest level of binding. Mutagenesis studies demonstrate the critical role of consecutive aromatic residues at the tip of the LBL for binding of H_C/DC to lipid membranes. Taking advantage of this insight, we then create a “gain-of-function” mutant H_C/B by replacing two nonaromatic residues at the tip of its LBL with tryptophan. Cocrystallization studies confirm that these two tryptophan residues do not alter the structure of H_C/B or the interactions with its receptors. Such a mutated H_C/B gains the ability to bind receptor-free lipid membranes and shows enhanced binding to cultured neurons. Finally, full-length BoNT/B containing two tryptophan mutations in its LBL, together with two additional mutations (E1191M/S1199Y) that increase binding to human receptors, is produced and evaluated in mice in vivo using Digit Abduction Score assays. This mutant toxin shows enhanced efficacy in paralyzing local muscles at the injection site and lower systemic diffusion, thus extending both safety range and duration of paralysis compared with the control BoNT/B. These findings establish a mechanistic understanding of LBL–lipid interactions and create a modified BoNT/B with improved therapeutic efficacy.

Botulinum neurotoxins are a family of bacterial toxins, some of which are approved for medical and cosmetic uses. This study shows that introducing aromatic residues to a lipid binding loop improved therapeutic efficacy of botulinum neurotoxin B by enhancing its ability to bind to lipid membranes at motor nerve terminals.

Clinical duration of action of different botulinum toxin types in humans

The Botulinum NeuroToxin (BoNT) comprises several serotypes with distinct properties, mechanisms of action, sensitivity and duration of effect in different species. The serotype A (BoNT/A) is the prevalent neurotoxin applied in human's disease. In this paper we present an overview of the current knowledge regarding the duration of effect and the neuromuscular sprouting of different BoNT serotypes in humans. Then, we report the original results of a study in healthy subjects treated with BoNT/A, B, C and F using different neurophysiological techniques. Twelve healthy volunteers (7 men, 5 women) are treated with BoNT/A, B, C and F or placebo in Abductor digiti minimi (ADM) muscle of the hand. Before and after injections, an extensive neurophysiological study is performed with the CMAP amplitude variation, Multi-Motor Unit Action Potentials (MUAPs) analysis, the Turns/Amplitude ratio of interference pattern (IP) and determination of jitter and Fiber Density (FD) at single-fiber electromyography (SFEMG), at week 2 (w2), 4 (w4), 6 (w6) and 8 (w8). A maximal neuromuscular block is obtained at w2 for all the serotypes. Afterwards, the CMAP trend appear similar for BoNT/A, B, and C while, BoNT/F shows a faster recover. Multi-MUAPs analysis and IP detect mild changes at w2 for all serotypes, except for BoNT/F that shows a greater change since w4. SFEMG have minimal changes in FD while, Jitter increase at w2 with a slower decrease over the time for all BoNTs. In conclusion, BoNT/F has earlier sprouting and complete recovery at w8. Other serotypes present a slower and similar profile. The EMG appear useful to study the functional recovery in humans, and these results should provide new evidence for assessing different serotypes. These findings improve our knowledge regarding the methods to evaluate duration of effects and dose equivalents in different serotypes, that in the future could change the clinicians strategy for disease-tailored BoNT therapies.

Novel Native and Engineered Botulinum Neurotoxins

Botulinum neurotoxins (BoNTs), produced by Clostridia and other bacteria, are the most potent toxins known. Their cleavage of the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins in neurons prevents the release of neurotransmitters, thus resulting in the muscle paralysis that is characteristic of botulism. This mechanism of action has been exploited for a variety of therapeutic and cosmetic applications of BoNTs. This chapter provides an overview of the native BoNTs, including the classical serotypes and their clinical use, mosaic BoNTs, and novel BoNTs that have been recently identified in clostridial and non-clostridial strains. In addition, the modular structure of native BoNTs, which are composed of a light chain and a heavy chain, is amenable to a multitude of novel fusions and mutations using molecular biology techniques. These novel recombinant BoNTs have been used or are being developed to further characterize the biology of toxins, to assist in vaccine production, to serve as delivery vehicles to neurons, and to be utilized as novel therapeutics for both neuronal and non-neuronal cells.

Injection into the Longus Colli Muscle via the Thyroid Gland

Background

Anterior forms of cervical dystonia are considered to be the most difficult to treat because of the deep cervical muscles that can be involved.

Case Report

We report the case of a woman with cervical dystonia who presented with anterior sagittal shift, which required injections through the longus colli muscle to obtain a satisfactory outcome. The approach via the thyroid gland was chosen.

Discussion

The longus colli muscle can be injected under electromyography (EMG), computed tomography (CT), ultrasonography (US), or endoscopy guidance. We recommend using both ultrasonography and electromyography guidance as excellent complementary techniques for injection at the C5-C6 level.

Immunogenicity Associated with Botulinum Toxin Treatment

Botulinum toxin (BoNT) has been used for the treatment of a variety of neurologic, medical and cosmetic conditions. Two serotypes, type A (BoNT-A) and type B (BoNT-B), are currently in clinical use. While considered safe and effective, their use has been rarely complicated by the development of antibodies that reduce or negate their therapeutic effect. The presence of antibodies has been attributed to shorter dosing intervals (and booster injections), higher doses per injection cycle, and higher amounts of antigenic protein. Other factors contributing to the immunogenicity of BoNT include properties of each serotype, such as formulation, manufacturing, and storage of the toxin. Some newer formulations with purified core neurotoxin devoid of accessory proteins may have lower overall immunogenicity. Several assays are available for the detection of antibodies, including both structural assays such as ELISA and mouse-based bioassays, but there is no consistent correlation between these antibodies and clinical response. Prevention and treatment of antibody-associated non-responsiveness is challenging and primarily involves the use of less immunogenic formulations of BoNT, waiting for the spontaneous disappearance of the neutralizing antibody, and switching to an immunologically alternate type of BoNT.

Minimal clinically important change in patients with cervical dystonia: Results from the CD PROBE study

OBJECTIVE

To determine the minimal clinically important change (MCIC) on Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) scores using data from Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE), which captured real-world practices and outcomes.

METHODS

Changes in the baseline TWSTRS scores (point and percentage changes) were compared to changes in the Patient and Clinician Global Impression of Change (PGIC and CGIC) ratings. Using logistic regression, the discrimination of the model was determined.

RESULTS

Among the 479 patients who completed all TWSTRS assessments, the mean TWSTRS Total score significantly decreased from baseline (39.2) to the final visit (27.1) (P < .0001). TWSTRS Total score point changes that compared with PGIC assessments "very much improved," "much improved" or better, and "minimally improved" or better were -11, -9, and -8, respectively, and were similar to previously published changes (ie, a decrease of ≥10 points). TWSTRS Total score data met indicators of good cutoffs for discrimination of the model including ≥70% percentage of outcomes correctly classified when compared with PGIC ratings. The TWSTRS Total score mapped to PGIC and CGIC ratings better than any TWSTRS subscale score.

CONCLUSIONS

The MCIC for improvement was ≥8 points based on mean TWSTRS Total scores in patients with cervical dystonia when compared against the patient-based evaluation of benefit (PGIC).

Pain in cervical dystonia and the antinociceptive effects of botulinum toxin: what is currently known?

Pain is the most common and disabling non-motor symptom in cervical dystonia (CD). Up to 88.9% of patients report pain at some point in the course of the disease. It is still a matter of debate whether CD-related pain originates only from prolonged muscle contraction. Recent data suggest that the alterations of transmission and processing of nociceptive stimuli play a crucial role in pain development. Botulinum toxin (BT) is the first-line therapy for CD. Despite fully elucidated muscle relaxant action, the antinociceptive effect of BT remains unclear and probably exceeds a simple decompression of the nerve fibers due to the reduction in muscle tone. The proposed mechanisms of the antinociceptive action of BT include inhibition of pain mediator release, inhibition of membrane sodium channels, retrograde axonal transport and impact on the other pain pathways. This article summarizes the current knowledge about the antinociceptive properties of BT and the clinical analgesic efficacy in the treatment of CD patients.

Botulinum neurotoxin serotype D - A potential treatment alternative for BoNT/A and B non-responding patients

OBJECTIVES

Botulinum neurotoxin serotypes A and B (BoNT/A & B) are highly effective medicines to treat hyperactive cholinergic neurons. Due to neutralizing antibody formation, some patients may become non-responders. In these cases, the serotypes BoNT/C-G might become treatment alternatives. BoNT/D is genetically least related to BoNT/A & B and thereby circumventing neutralisation in A/B non-responders. We produced BoNT/D and compared its pharmacology with BoNT/A ex vivo in mice tissue and in vivo in human volunteers.

METHODS

BoNT/D was expressed recombinantly in E. coli, isolated by chromatography and its ex vivo potency was determined at mouse phrenic nerve hemidiaphragm preparations. Different doses of BoNT/D or incobotulinumtoxinA were injected into the extensor digitorum brevis (EDB) muscles (n = 30) of human volunteers. Their compound muscle action potentials were measured 11 times by electroneurography within 220 days.

RESULTS

Despite a 3.7-fold lower ex vivo potency in mice, a 110-fold higher dosage of BoNT/D achieved the same clinical effect as incobotulinumtoxinA while showing a 50% shortened duration of action.

CONCLUSIONS

BoNT/D blocks dose-dependently acetylcholine release in human motoneurons upon intramuscular administration, but its potency and duration of action is inferior to approved BoNT/A based drugs.

SIGNIFICANCE

BoNT/D constitutes a potential treatment alternative for BoNT/A & B non-responders.

Pallidal neurostimulation versus botulinum toxin injections in the treatment of cervical dystonia: protocol of a randomized, sham-controlled trial (StimTox-CD)

Background

Selective peripheral denervation via botulinum neurotoxin injections into dystonic muscles is the first-line treatment for cervical dystonia. Pallidal neurostimulation is a potent alternative, but currently restricted to patients failing on neurotoxin therapy. As botulinum neurotoxin is partially effective but often unsatisfactory in a relevant proportion of patients, earlier neurostimulation might be advantageous in providing stable symptom control and preventing disability. This trial intends to demonstrate, that pallidal neurostimulation is superior to neurotoxin injections in best clinical practice for controlling the symptoms of cervical dystonia and that it is safe in patients with a partial therapy response to peripheral denervation. We hypothesize a better outcome in everyday functioning and health-related quality of life of neurostimulated patients.

Methods

We aim to recruit 66 cervical dystonia patients into a double-blind comparison of pallidal neurostimulation versus botulinum neurotoxin type A. Eligible patients need ≥25% motor symptom reduction 4 weeks after a neurotoxin test injection, but are willing to undergo DBS surgery due to unsatisfactory symptom control. All participants will be implanted with a DBS system, and randomized into 2 groups: First group will receive effective neurostimulation and saline injections into dystonic muscles. Second group is treated with regular neurotoxin injections and undergoes a sham-stimulation. Primary outcome is the change in TWSTRS total score between baseline and 6 months of therapy. Secondary outcome parameters are corresponding changes in TWSTRS motor score, Tsui score, CDQ-24 and SF-36. Safety will be assessed by frequency and severity of reported adverse events. Statistical analysis includes intention-to-treat and per protocol populations, analysis based on imputation of missing values and analysis adjusting for differences in baseline TWSTRS. After 6 months of blinded treatment all patients will receive open-label neurostimulation and neurotoxin treatment as needed, and are followed up 48 weeks after randomization.

Perspective

We will assess if pallidal neurostimulation is a safe and effective alternative to selective peripheral denervation by botulinum toxin injections in cervical dystonia, which may be offered earlier in the course of disease based on patient preference. A positive study outcome would influence future treatment guidelines of cervical dystonia.

Trial registration

EudraCT registration number: 2016-001378-13.

Meaningful Assessment in Patients with Acquired Brain Injuries

There are several key components to the meaningful and comprehensive assessment of patients with acquired brain injuries with respect to management of the upper motor neuron syndrome. Type of brain injury, trajectory of recovery, relevant concomitant complications, development of appropriate goals, and an understanding of resources available for patients are all factors to assess when developing a treatment plan. Using appropriate outcome measures will help monitor the efficacy of interventions and guide ongoing management of spasticity.

Engineered botulinum neurotoxin B with improved binding to human receptors has enhanced efficacy in preclinical models

Although botulinum neurotoxin serotype A (BoNT/A) products are common treatments for various disorders, there is only one commercial BoNT/B product, whose low potency, likely stemming from low affinity toward its human receptor synaptotagmin 2 (hSyt2), has limited its therapeutic usefulness. We express and characterize two full-length recombinant BoNT/B1 proteins containing designed mutations E1191M/S1199Y (rBoNT/B1MY) and E1191Q/S1199W (rBoNT/B1QW) that enhance binding to hSyt2. In preclinical models including human-induced pluripotent stem cell neurons and a humanized transgenic mouse, this increased hSyt2 affinity results in high potency, comparable to that of BoNT/A. Last, we solve the cocrystal structure of rBoNT/B1MY in complex with peptides of hSyt2 and its homolog hSyt1. We demonstrate that neuronal surface receptor binding limits the clinical efficacy of unmodified BoNT/B and that modified BoNT/B proteins have promising clinical potential.

The Use of Botulinum Toxin for Treatment of the Dystonias

Dystonias are characterized by involuntary muscle contractions, twisting movements, abnormal postures, and often tremor in various body regions. However, in the last decade several studies have demonstrated that dystonias are also characterized by sensory abnormalities. While botulinum toxin is the gold standard therapy for focal dystonia, exactly how it improves this disorder is not entirely understood. Neurophysiological studies in animals and humans have clearly demonstrated that botulinum toxin improves dystonic motor manifestations by inducing chemodenervation, therefore weakening the injected muscles. In addition, neurophysiological and neuroimaging evidence also suggests that botulinum toxin modulates the activity of various neural structures in the CNS distant from the injected site, particularly cortical motor and sensory areas. Concordantly, recent studies have shown that in patients with focal dystonias botulinum toxin ameliorates sensory disturbances, including reduced spatial discrimination acuity and pain. Overall, these observations suggest that in these patients botulinum toxin-induced effects encompass complex mechanisms beyond chemodenervation of the injected muscles.

Lumbar Sympathetic Block with Botulinum Toxin Type A and Type B for the Complex Regional Pain Syndrome

A lumbar sympathetic ganglion block (LSB) is a therapeutic method for complex regional pain syndrome (CRPS) affecting the lower limbs. Recently, LSB with botulinum toxin type A and B was introduced as a novel method to achieve longer duration of analgesia. In this study, we compared the botulinum toxin type A (BTA) with botulinum toxin type B (BTB) in performing LSB on patients with CRPS. LSB was performed with either BTA or BTB on patients with CRPS in their lower extremities. The length of time taken for patients to return to the pre-LSB pain score and the adverse effect of LSB with BTA/BTB were investigated. The median length of time taken for the patients to return to the pre-LSB pain score was 15 days for the BTA group and 69 days for the BTB group (P = 0.002). Scores on a visual analogue scale decreased in the patients of both groups, and no significant adverse effects were experienced. In conclusion, the administration of either BTA or BTB for LSB is a safe method to prolong the sympathetic blocking effect in patients with CRPS. BTB is more effective than BTA to prolong the sympathetic blocking effect in CRPS patients.

Botulinum Toxin Treatment of Movement Disorders

Botulinum neurotoxins (BoNTs) are now among the most widely used therapeutic agents in clinical medicine with indications applied to the fields of movement disorders, pain disorders, and autonomic dysfunction. In this literature review, the efficacy and utility of BoNTs in the field of movement disorders are assessed using the criteria of the Guideline Development Subcommittee of the American Academy of Neurology. The literature supports a level A efficacy (established) for BoNT therapy in cervical dystonia and a level B efficacy (probably effective) for blepharospasm, hemifacial spasm, laryngeal dystonia (spasmodic dysphonia), task-specific dystonias, essential tremor, and Parkinson rest tremor. It is the view of movement disorder experts, however, that despite the level B efficacy, BoNTs should be considered treatment of first choice for blepharospasm, hemifacial spasm, laryngeal, and task-specific dystonias. The emerging data on motor and vocal tics of Tourette syndrome and oromandibular dystonias are encouraging but the current level of efficacy is U (undetermined) due to lack of published high-quality studies.

When movement disorders hurt: Addressing pain in hyperkinetic disorders

Pain is an important nonmotor symptom in movement disorders. Dystonia is a hyperkinetic movement disorder characterized by involuntary, sustained or intermittent muscle contractions causing abnormal movements, postures or both. Contrary to common views the nonmotor symptoms are present in dystonia patients. Pain is a prevailing feature of cervical dystonia (CD), the most common form of focal dystonia. The mechanism of pain in CD remains mostly unknown, but there are growing evidence that it could not be only the consequence of muscle hyperactivity. We have shown that botulinum toxin (BoNT) produced pain relief before muscle relaxation and that effect on pain relief lasted longer than the effect on motor improvement. More and more data suggest that pain relief could be attributed to the direct effect of BoNT type A on central nervous system. Pain, depression, and anxiety have been shown to be significant determinants of QoL in focal dystonia patients. Routine clinical examination in patients with dystonia should include evaluation of motor as well as non-motor symptoms. Selective rating assessment should be used in clinical practice to quantify pain. Specific assessment of pain is important to determine the effect of BoNT as the most effective treatment in focal dystonia.

Engineered botulinum neurotoxin B with improved efficacy for targeting human receptors

Botulinum neurotoxin B is a Food and Drug Administration-approved therapeutic toxin. However, it has lower binding affinity toward the human version of its major receptor, synaptotagmin II (h-Syt II), compared to mouse Syt II, because of a residue difference. Increasing the binding affinity to h-Syt II may improve botulinum neurotoxin B’s therapeutic efficacy and reduce adverse effects. Here we utilized the bacterial adenylate cyclase two-hybrid method and carried out a saturation mutagenesis screen in the Syt II-binding pocket of botulinum neurotoxin B. The screen identifies E1191 as a key residue: replacing it with M/C/V/Q enhances botulinum neurotoxin B binding to human synaptotagmin II. Adding S1199Y/W or W1178Q as a secondary mutation further increases binding affinity. Mutant botulinum neurotoxin B containing E1191M/S1199Y exhibits ~11-fold higher efficacy in blocking neurotransmission than wild-type botulinum neurotoxin B in neurons expressing human synaptotagmin II, demonstrating that enhancing receptor binding increases the overall efficacy at functional levels. The engineered botulinum neurotoxin B provides a platform to develop therapeutic toxins with improved efficacy.

Humans are less sensitive to the therapeutic effects of botulinum neurotoxin B (BoNT/B) than the animal models it is tested on due to differences between the human and the mouse receptors. Here, the authors engineer BoNT/B to improve its affinity to human receptors and enhance its therapeutic efficacy.