Use of botulinum toxin A in adult neurological disorders: efficacy, tolerability and safety

Pooled Safety Analysis of IncobotulinumtoxinA in the Treatment of Neurological Disorders in Adults

The pooled incidences of treatment-emergent adverse events (TEAEs) were examined by indication using the integrated clinical database of Merz-sponsored, placebo-controlled, or repeat-dose studies of incobotulinumtoxinA in adults with cervical dystonia, blepharospasm, limb spasticity, sialorrhea, or essential tremor of the upper limb. Overall incidences of TEAEs, serious TEAEs, TEAEs leading to discontinuation, fatal TEAEs, TEAEs of special interest (TEAESIs; indicating possible toxin spread), and treatment-related (TR) events were determined for incobotulinumtoxinA and placebo after a single injection and for repeated dose cycles of incobotulinumtoxinA. The most frequent events after a single dose of incobotulinumtoxinA are summarized. After a single cycle, incidences of overall TEAEs were similar between incobotulinumtoxinA and the placebo in most indications, although between-indication differences were observed. Few TEAEs led to incobotulinumtoxinA discontinuation; there were no fatal TEAEs with incobotulinumtoxinA. In general, repeated cycles did not increase the incidence of any event. The most frequent TR-TEAEs were indication-dependent, including dysphagia for indications affecting the head or neck. The TR-TEAESIs across all indications were most commonly muscular weakness, dysphagia and dry mouth. Overall, the results of this pooled analysis support and extend the favorable safety and tolerability profile of incobotulinumtoxinA for the treatment of adult neurological disorders established by individual clinical studies.

A Bayesian Network Meta-Analysis and Systematic Review of Guidance Techniques in Botulinum Toxin Injections and Their Hierarchy in the Treatment of Limb Spasticity

Accurate targeting of overactive muscles is fundamental for successful botulinum neurotoxin (BoNT) injections in the treatment of spasticity. The necessity of instrumented guidance and the superiority of one or more guidance techniques are ambiguous. Here, we sought to investigate if guided BoNT injections lead to a better clinical outcome in adults with limb spasticity compared to non-guided injections. We also aimed to elucidate the hierarchy of common guidance techniques including electromyography, electrostimulation, manual needle placement and ultrasound. To this end, we conducted a Bayesian network meta-analysis and systematic review with 245 patients using the MetaInsight software, R and the Cochrane Review Manager. Our study provided, for the first time, quantitative evidence supporting the superiority of guided BoNT injections over the non-guided ones. The hierarchy comprised ultrasound on the first level, electrostimulation on the second, electromyography on the third and manual needle placement on the last level. The difference between ultrasound and electrostimulation was minor and, thus, appropriate contextualization is essential for decision making. Taken together, guided BoNT injections based on ultrasound and electrostimulation performed by experienced practitioners lead to a better clinical outcome within the first month post-injection in adults with limb spasticity. In the present study, ultrasound performed slightly better, but large-scale trials should shed more light on which modality is superior.

Smell and taste in idiopathic blepharospasm

The pathophysiology of blepharospasm is incompletely understood. Current concepts suggest that blepharospasm is a network disorder, involving basal ganglia, thalamus, cortex, and, possibly, the cerebellum. Tracing, imaging, and clinical studies revealed that these structures are also concerned with olfaction and taste. Because of this anatomical overlap, dysfunction of the chemical senses in blepharospasm is expected. Injections of botulinum toxin into the eyelid muscles are the first-line treatment of blepharospasm. Yet, the effects of botulinum toxin on the chemical senses have not been systematically assessed. To contribute to a better understanding of blepharospasm, olfactory and gustatory abilities were assessed in 17 subjects with blepharospasm and 17 age-/sex-matched healthy controls. Sniffin Sticks were used to assess odor threshold, odor discrimination, and odor identification. Results of these three Sniffin Sticks subtests were added to the composite olfactory score. The Taste Strips were applied to assess taste. In an adjacent study, we assessed the sense of smell and taste in eight subjects with blepharospasm before and 4 weeks after botulinum toxin treatment. Subjects with blepharospasm had significantly lower (= worse) scores for odor threshold and for the composite olfactory score than healthy controls, while odor discrimination, odor identification, and the composite taste score were not different between groups. The adjacent study revealed that botulinum toxin did not impact the chemical senses. In this study, subjects with blepharospasm had a lower (= worse) odor threshold than healthy controls. As olfaction is important in daily life, findings justify further research of olfaction in blepharospasm.

Jitter Evaluation in Distant and Adjacent Muscles after Botulinum Neurotoxin Type A Injection in 78 Cases

To study the jitter parameters in the distant (DM) and the adjacent muscle (AM) after botulinum neurotoxin type A (BoNT/A) injection in 78 patients, jitter was measured by voluntary activation in DM (n = 43), and in AM (n = 35). Patients were receiving BoNT/A injections as a treatment for movement disorders. Mean age 65.1 years (DM) and 61.9 years (AM). The mean jitter was abnormal in 13.9% (maximum 41.4 µs) of DM, and 40% (maximum 43.7 µs) of AM. Impulse blocking was sparse. We found no correlation of the mean jitter to age, BoNT/A most recent injection (days/units), number of muscles injected, total BoNT/A units summated, number of total BoNT/A sessions, beta-blockers/calcium channel blockers use, and cases with local spread symptoms such as eyelid drop/difficulty swallowing. Maximum mean jitter (41.4/43.7 µs) for DM/AM occurred 61 and 131 days since the most recent BoNT/A, respectively. The far abnormal mean jitter (32.6/36.9 µs) occurred 229 and 313 days since the most recent BoNT/A. We suggested that jitter measurement can be done after BoNT/A in a given muscle other than the injected one, after 8 (DM) and 11 (AM) months, with reference >33 µs and >37 µs, respectively.

Botulinum toxin for hereditary spastic paraplegia: effects on motor and non-motor manifestations

Motor and non-motor manifestations are common and disabling features of hereditary spastic paraplegia (HSP). Botulinum toxin type A (Btx-A) is considered effective for spasticity and may improve gait in these patients. Little is known about the effects of Btx-A on non-motor symptoms in HSP patients. Objective To assess the efficacy of Btx-A on motor and non-motor manifestations in HSP patients. Methods Thirty-three adult patients with a clinical and molecular diagnosis of HSP were evaluated before and after Btx-A injections. Results Mean age was 41.7 ± 13.6 years and there were 18 women. Most patients had a pure phenotype and SPG4 was the most frequent genotype. The Btx-A injections resulted in a decrease in spasticity at the adductor muscles, and no other motor measure was significantly modified. In contrast, fatigue scores were significantly reduced after Btx-A injections. Conclusion Btx-A injections resulted in no significant functional motor improvement for HSP, but fatigue improved after treatment.

Botulinum toxin: A lift for chronic migraines

Chronic migraines are a common condition among patients seen in primary care and management often is a challenge. Despite existing therapies to help manage this condition, many patients continue to experience undue stress and diminished quality of life secondary to pain. This article briefly reviews treatments for migraine and introduces the role of onabotulinumtoxin A (Botox A) in improving the management of chronic migraines.

Identification of fibroblast growth factor receptor 3 (FGFR3) as a protein receptor for botulinum neurotoxin serotype A (BoNT/A)

Botulinum neurotoxin serotype A (BoNT/A) causes transient muscle paralysis by entering motor nerve terminals (MNTs) where it cleaves the SNARE protein Synaptosomal-associated protein 25 (SNAP25₂₀₆) to yield SNAP25₁₉₇. Cleavage of SNAP25 results in blockage of synaptic vesicle fusion and inhibition of the release of acetylcholine. The specific uptake of BoNT/A into pre-synaptic nerve terminals is a tightly controlled multistep process, involving a combination of high and low affinity receptors. Interestingly, the C-terminal binding domain region of BoNT/A, H_C/A, is homologous to fibroblast growth factors (FGFs), making it a possible ligand for Fibroblast Growth Factor Receptors (FGFRs). Here we present data supporting the identification of Fibroblast Growth Factor Receptor 3 (FGFR3) as a high affinity receptor for BoNT/A in neuronal cells. H_C/A binds with high affinity to the two extra-cellular loops of FGFR3 and acts similar to an agonist ligand for FGFR3, resulting in phosphorylation of the receptor. Native ligands for FGFR3; FGF1, FGF2, and FGF9 compete for binding to FGFR3 and block BoNT/A cellular uptake. These findings show that FGFR3 plays a pivotal role in the specific uptake of BoNT/A across the cell membrane being part of a larger receptor complex involving ganglioside- and protein-protein interactions.

Botulinum neurotoxin serotype A (BoNT/A) is one of seven neurotoxins (BoNT/A-G), produced by the bacteria Clostridium botulinum that are both poisons and versatile therapeutics. These toxins enter motor neurons where they prevent the release of acetylcholine at the neuromuscular junction. The specific uptake of BoNT/A across the neuronal cell membrane is dependent on specific receptor interactions. Binding to high density ganglioside GT1b mediates the initial binding step and via a low affinity interaction concentrates BoNT/A on the cell surface. Once anchored in the membrane, lateral movements within the plasma membrane facilitate intermolecular interactions of BoNT/A with additional lower density but higher affinity protein receptors. Here we present data supporting the identification of Fibroblast Growth Factor Receptor 3 (FGFR3) as a high affinity receptor for BoNT/A. We show that BoNT/A binds to FGFR3 with high affinity and functions as an agonist ligand for FGFR3. The identification of this novel receptor for BoNT/A represents an important advance in the understanding of the mechanism of action of BoNT/A, especially on the initial steps of neuronal uptake, and can be the basis for the development of new specific countermeasures and new BoNT/A-based therapeutics.

Paclitaxel is an inhibitor and its boron dipyrromethene derivative is a fluorescent recognition agent for botulinum neurotoxin subtype A

We have successfully identified one new inhibitor and one new fluorescent recognition agent for the botulinum neurotoxin subtype A (BoNT/A) using the virtual screening protocol "protein scanning with virtual ligand screening" (PSVLS). Hit selection used an in-house developed holistic binding scoring method. Selected hits were tested experimentally for inhibitory activity using fluorescence resonance energy transfer (FRET) assays against the light chain (catalytic domain) of BoNT/A. Ligand binding was determined against the light and heavy chain BoNT/A complex through either radiolabeled ligand binding assays (nonfluorescent ligands) or fluorescence intensity assays (fluorescent ligands). These experimental assays have confirmed one compound (paclitaxel) to inhibit BoNT/A's proteolytic activity experimentally with an IC50 of 5.2 μM. A fluorescent derivative was also confirmed to bind to the toxin and therefore is a suitable candidate for the rational design of new detection agents and for the development of fluorescence-based multiprobe detection assays.

Botulinum neurotoxin serotype A specific cell-based potency assay to replace the mouse bioassay

Botulinum neurotoxin serotype A (BoNT/A), a potent therapeutic used to treat various disorders, inhibits vesicular neurotransmitter exocytosis by cleaving SNAP25. Development of cell-based potency assays (CBPAs) to assess the biological function of BoNT/A have been challenging because of its potency. CBPAs can evaluate the key steps of BoNT action: receptor binding, internalization-translocation, and catalytic activity; and therefore could replace the current mouse bioassay. Primary neurons possess appropriate sensitivity to develop potential replacement assays but those potency assays are difficult to perform and validate. This report describes a CBPA utilizing differentiated human neuroblastoma SiMa cells and a sandwich ELISA that measures BoNT/A-dependent intracellular increase of cleaved SNAP25. Assay sensitivity is similar to the mouse bioassay and measures neurotoxin biological activity in bulk drug substance and BOTOX® product (onabotulinumtoxinA). Validation of a version of this CBPA in a Quality Control laboratory has led to FDA, Health Canada, and European Union approval for potency testing of BOTOX®, BOTOX® Cosmetic, and Vistabel®. Moreover, we also developed and optimized a BoNT/A CBPA screening assay that can be used for the discovery of novel BoNT/A inhibitors to treat human disease.

Optimal management for people with severe spasticity

Spasticity is characterized by velocity-dependent increase in tonic stretch reflexes and tendon jerks. Many people affected by spasticity receive late treatment, or no treatment, which greatly reduces the potential to regain full motor control and restore function. There is much to consider before determining treatment for people with spasticity. Treatment of pediatric patients increases the complexity, because of the substantial difference between adult and pediatric spasticity. Proper patient evaluation, utilization of scales and measures, and obtaining patient and caregiver history is vital in determining optimal spasticity treatment. Further, taking into consideration the limitations and desires of individuals serve as a guide to best management. We have grouped contributing factors into the IDAHO Criteria to elucidate a multidisciplinary approach, which considers a person's complete field of experience. This model is applied to goal setting, and recognizes the importance of a spasticity management team, comprising the treatment subject, his/her family, the environment, and a supportive, well-informed medical staff. The criteria take into account the complexity associated with diagnosing and treating spasticity, with the ultimate goal of improved function.

Comparative evaluation of the potency and antigenicity of two distinct BoNT/A-derived formulations

IncobotulinumtoxinA (Xeomin®) and onabotulinumtoxinA (BOTOX®) are unique botulinum neurotoxin type A (BoNT/A)-derived drugs. IncobotulinumtoxinA utilizes the naked 150 kDa holotoxin portion of BoNT/A, whereas onabotulinumtoxinA uses the complete native 900 kDa complex as drug substance. On the basis of purportedly similar pharmacological characteristics, these formulations were evaluated for potency by LD₅₀ and mouse Digit Abduction Score (DAS) bioassays. DAS was also used to assess antigenicity. Full-range DAS dose-response profiles were achieved with four lots of each product, with similar observations between lots for a given product. Between products, however, the mean DAS potency of incobotulinumtoxinA (ED₅₀ range 7.0-10.2 U/kg) was significantly lower than that of onabotulinumtoxinA (ED₅₀ range 4.4-6.4 U/kg), consistent with lower measured potencies in the LD₅₀ assay for incobotulinumtoxinA (potency range 62-82 U). In assessments of DAS duration of effect at similar unit doses, the observed lower potency of incobotulinumtoxinA translated into decreased peak efficacy and dose effect over time (i.e. shorter duration). In contrast, at equi-efficacious doses yielding near-maximal DAS responses, both toxin formulations were uniformly inhibited in a statistically significant manner when preincubated with rabbit-derived, onabotulinumtoxinA-neutralizing antibodies, supporting the position that inhibition of 150 kDa holotoxin serves as the common basis for neutralization and, therefore, incobotulinumtoxinA would not be expected to be effective in onabotulinumtoxinA-immunoresistant subjects (and vice versa). Further, with lower lot-to-lot relative potency, incobotulinumtoxinA is not dose-equivalent or interchangeable with onabotulinumtoxinA, suggesting that various aspects of drug product formulation may influence observed pharmacology.

OnabotulinumtoxinA (BOTOX®): a review of its use in the prophylaxis of headaches in adults with chronic migraine

This article reviews the pharmacology, therapeutic efficacy and tolerability profile of intramuscularly injected onabotulinumtoxinA (onaBoNTA; BOTOX®) for headache prophylaxis in adults with chronic migraine, with a focus on UK labelling for the drug. The pharmacological actions of onaBoNTA include a direct antinociceptive (analgesic) effect; while not fully understood, the mechanism of action underlying its headache prophylaxis effect in chronic migraine is presumed to involve inhibition of peripheral and central sensitization in trigeminovascular neurones. Pooled findings from two large phase III studies of virtually identical design (PREEMPT [Phase III REsearch Evaluating Migraine Prophylaxis Therapy] 1 and 2) showed that treatment with up to five cycles of onaBoNTA (155-195 units/cycle) at 12-week intervals was effective in reducing headache symptoms, decreasing headache-related disability, and improving health-related quality of life (HR-QOL) in patients with chronic migraine, approximately two-thirds of whom were overusing acute headache medications at baseline. During the double-blind phase of both trials, significantly more patients treated with onaBoNTA (two cycles) than placebo experienced clinically meaningful improvements in the monthly frequencies of headache days, moderate to severe headache days and migraine days, and in the cumulative hours of headache on headache days/month. OnaBoNTA therapy also resulted in statistically significant and clinically meaningful improvements in functioning and HR-QOL compared with placebo. Notably, improvements in headache symptoms, functioning and HR-QOL favouring onaBoNTA over placebo were seen regardless of whether or not patients were medication overusers and irrespective of whether or not they were naive to (oral) prophylactic therapy. Further improvements relative to baseline in headache symptoms, functioning and HR-QOL were observed during the open-label extension phase of both trials (all patients received three cycles of onaBoNTA). Treatment with up to five cycles of onaBoNTA was generally well tolerated in the PREEMPT trials. Treatment-related adverse events reported by onaBoNTA recipients (e.g. neck pain, facial paresis and eyelid ptosis) were consistent with the well established tolerability profile of the neurotoxin when injected into head and neck muscles; no new safety events were observed. Debate surrounding the PREEMPT studies has centred on the small treatment effect of onaBoNTA relative to placebo, the possibility that blinding was inadequate and the relevance of the evaluated population. Nonetheless, the totality of the data showed that onaBoNTA therapy produced clinically meaningful improvements in headache symptoms, functioning and HR-QOL; on the basis of these trials, it has become the first (and so far only) headache prophylactic therapy to be specifically approved for chronic migraine in the UK and US. Overall, onaBoNTA offers a beneficial, acceptably tolerated and potentially convenient option for the management of this highly disabling condition, for example in patients who are refractory to oral medications used for prophylaxis.

Botulinum toxin A (Dysport®): in dystonias and focal spasticity

Dysport®, a formulation of botulinum toxin A, blocks acetylcholine release at neuromuscular junctions causing denervation and temporary muscle paralysis. It is used to treat several medical conditions, including dystonias and focal spasticity. Subcutaneous Dysport® was effective in improving functional disability in adults with blepharospasm in a placebo-controlled trial with 16 weeks' follow-up, and in adults with hemifacial spasm in case series. Similarly, intramuscular Dysport® was effective in improving symptoms of cervical dystonia in adults, focal spasticity in adults with post-stroke upper limb spasticity and dynamic equinus spasticity in paediatric patients with cerebral palsy in placebo-controlled trials with up to 20 weeks' follow-up. However, in two 12-week, placebo-controlled trials in adults with focal lower limb spasticity (spastic equinovarus deformity after stroke and hip adductor spasticity associated with multiple sclerosis) intramuscular Dysport® had limited efficacy. Available longer-term data indicated that Dysport® treatment was effective over several treatment cycles in patients with cervical dystonia or upper limb spasticity. Dysport® was generally well tolerated in patients with dystonias or focal spasticity. Most adverse events were mild to moderate and transient.

Migraine surgery: a plastic surgery solution for refractory migraine headache

Migraine headache can be a debilitating condition that confers a substantial burden to the affected individual and to society. Despite significant advancements in the medical management of this challenging disorder, clinical data have revealed a proportion of patients who do not adequately respond to pharmacologic intervention and remain symptomatic. Recent insights into the pathogenesis of migraine headache argue against a central vasogenic cause and substantiate a peripheral mechanism involving compressed craniofacial nerves that contribute to the generation of migraine headache. Botulinum toxin injection is a relatively new treatment approach with demonstrated efficacy and supports a peripheral mechanism. Patients who fail optimal medical management and experience amelioration of headache pain after injection at specific anatomical locations can be considered for subsequent surgery to decompress the entrapped peripheral nerves. Migraine surgery is an exciting prospect for appropriately selected patients suffering from migraine headache and will continue to be a burgeoning field that is replete with investigative opportunities.

Capsaicin protects mouse neuromuscular junctions from the neuroparalytic effects of botulinum neurotoxin a

Botulinum neurotoxin A (BoNT/A), the most toxic, naturally occurring protein, cleaves synapse-associated protein of 25 kDa and inhibits acetylcholine release from motor nerve endings (MNEs). This leads to paralysis of skeletal muscles. Our study demonstrates that capsaicin protects mouse neuromuscular junctions from the neuroparalytic effects of BoNT/A. Bilateral injection of BoNT/A near the innervation of the Extensor digitorum longus (EDL) muscle of adult Swiss-Webster mice inhibited the toe spread reflex (TSR). However, when capsaicin was coinjected bilaterally, or injected 4 or 8 h before injecting BoNT/A, the TSR remained normal. In animals that were pretreated with capsazepine, capsaicin failed to protect against the neuroparalytic effects of BoNT/A. In vivo analyses demonstrated that capsaicin protected muscle functions and electromygraphic activity from the incapacitating effects of BoNT/A. The twitch response to nerve stimulation was greater for EDL preparations isolated from mice injected with capsaicin before BoNT/A. Capsaicin pretreatment also prevented the inhibitory effects of BoNT/A on end-plate currents. Furthermore, pretreatment of Neuro 2a cells with capsaicin significantly preserved labeling of synaptic vesicles by FM 1-43. This protective effect of capsaicin was observed only in the presence of extracellular Ca(2+) and was inhibited by capsazepine. Immunohistochemistry demonstrated that MNEs express transient receptor potential protein of the vanilloid subfamily, TRPV1, the capsaicin receptor. Capsaicin pretreatment, in vitro, reduced nerve stimulation or KCl-induced uptake of BoNT/A into motor nerve endings and cholinergic Neuro 2a cells. These data demonstrate that capsaicin interacts with TRPV1 receptors on MNEs to reduce BoNT/A uptake via a Ca(2+)-dependent mechanism.

Idiopathic hemifacial spasm responsive to zonisamide: a case report

AIM

We describe a patient with idiopathic hemifacial spasm (HFS) that was responsive to zonisamide treatment.

METHODS AND RESULTS

A 65-year-old woman presented with a 4-year history of left-sided HFS developing gradually, starting from the upper facial muscles. After several analyses, the diagnosis of idiopathic HFS was made, and the clonazepam treatment (0.5 mg every 8 hours) was started, without a complete remission of symptoms. Therefore, zonisamide (150 mg twice a day for a 6-week period) was added, with a complete resolution. The rechallenge with zonisamide after its dechallenge confirmed its effectiveness. During follow-up, the patient remained symptom-free, with no adverse drug reactions.

CONCLUSIONS

We suggest that zonisamide could represent a useful therapeutic option in the treatment of idiopathic HFS.