Immunogenicity of Botulinum Toxin Formulations: Potential Therapeutic Implications

Exploring Nonresponse to Botulinum Toxin in Aesthetics: Narrative Review of Key Trigger Factors and Effective Management Strategies

Background

Nonresponse to botulinum toxin type A (BoNT-A) has been reported in both medical and aesthetic applications. Secondary nonresponse (SNR) occurs when BoNT-A is initially effective before failure commences at a later point. Most reported cases involve SNR in aesthetics. Several aspects of this complication remain elusive or controversial.

Objective

We aimed to address unanswered questions regarding the prevalence and etiology of SNR. Additionally, we investigated the immunogenicity of BoNT-A formulations, mainly focusing on the development of neutralizing antibodies that hinder the toxin's pharmacologic effects. Furthermore, we sought to examine the management strategies for SNR.

Methods

The PubMed and Google Scholar databases were searched from inception for articles on nonresponse to BoNT-A therapy. Articles were evaluated based on their contribution to the field. Expert opinions and panel recommendations regarding management and data gaps were also included in the review.

Results

There are limited data on SNR prevalence in aesthetic applications compared to therapeutic uses. Trigger factors of SNR include improper handling of BoNT-A; incorrect injection practices; and impurities present in the formulation, such as clostridial complexing proteins that may increase immunogenicity. Other contributing factors include infection; patient characteristics; and treatment parameters that encompass an increased frequency of BoNT-A injections (ie, <3 months apart), higher cumulative dosages, elevated treatment dosages, and booster injections (retreatment within 3 weeks of the initial injection). Neutralizing antibodies developed with first-generation formulations, such as onabotulinumtoxinA and abobotulinumtoxinA that contain clostridial proteins, but not with second-generation BoNT-As, such as incobotulinumtoxinA and daxibotulinumtoxinA, which lack these proteins. Among patients who developed SNR after using first-generation BoNT-A for aesthetic purposes, switching to incobotulinumtoxinA therapy did not result in the development of immune responses. Switching to a protein-free BoNT-A formulation such as incobotulinumtoxinA upon development of SNR has been advocated. To effectively manage SNR, it is crucial to minimize the identified trigger factors.

Conclusions

Nonresponse to BoNT-A is gaining importance in aesthetic treatments. Considering the potential for immunogenicity is essential when selecting a BoNT-A formulation. Preventing SNR is crucial, given the lack of solid data on effective treatments.

Integrated metabolomics and proteomics analysis in children with cerebral palsy exposed to botulinum toxin-A

BACKGROUND

We previously examined plasma metabolic changes before and after botulinum toxin-A injections of cerebral palsy (CP) children and showed that the glycine, serine and threonine metabolism may play a key role in neuritogenesis. This study analysed untargeted metabolomics combined with proteomics of plasma to discussed which substances are meaningfully changed, to what extent they affect the effects of action.

METHODS

Blood samples were collected from 91 children with spastic CP at 4 time points: pre-injection (T1), 1 month post-injection (T2), 3 months post-injection (T3) and 6 months post-injection (T4). Differentially changed metabolites and proteins were selected, and co-expression pathways were constructed to explore the key molecular processes.

RESULTS

A total of 674 proteins and 354 metabolites were identified. The differential metabolites were mainly involved in the linoleic acid metabolism, beta-Alanine metabolism, citrate cycle, pyruvate metabolism and glycolysis or gluconeogenesis. Differential proteins were primarily associated with glucose metabolism, lipid metabolism, immune and inflammation responses. Co-expression pathways showed that ECM-receptor interaction, complement and coagulation cascades, glycolysis or gluconeogenesis, pyruvate metabolism, and linoleic acid metabolism were the main pathways.

CONSLUSIONS

Our results indicated the botulinum toxin-A predominantly activated the glucose metabolism, lipid metabolism, and immune and inflammation responses, and energy metabolism changed significantly in this process.

TRIAL REGISTRATION DETAILS

ChiCTR2000033800, Research on the mechanism of botulinum toxin relieving spasticity in children with cerebral palsy. Approval No. 202023041. Registered 13 June 2020, http://www.chictr.org.cn/showproj.html?proj=52267 .

IMPACT STATEMENT

This is the first study that combined dynamic metabolomics and proteomics analysis to investigate the molecular changes in children with spastic cerebral palsy after botulinum toxin-A injections, which might provide a theoretical reference for the further subsequent study for targets to increase the efficacy and prolong the duration of botulinum toxin-A, and would be a valuable resource for the metabolomics and proteomics field in this group.

Computational Immunogenetic Analysis of Botulinum Toxin A Immunogenicity and HLA Gene Haplotypes: New Insights

Botulinum toxin A (BoNT-A) is widely used in both therapeutic and aesthetic settings; however, the formation of neutralizing antibodies (NAbs) remains a critical concern, leading to treatment failure. Immunogenic responses are known to vary between individuals due to HLA polymorphisms. Although some claim that neurotoxin-associated proteins (NAPs) shield BoNT-A from immune detection or are themselves immunogenic, there is limited molecular evidence supporting either view. This study applies computational immunogenetics to explore BoNT-A immunogenicity, focusing on HLA binding and the influence of accessory proteins. Epitope mapping, molecular docking, and HLA binding predictions were used to evaluate interactions between BoNT-A epitopes and selected class II HLA alleles (HLA-DQA1*01:02, HLA-DQA1*03:03, HLA-DQB1*06:04, HLA-DQB1*03:01, and HLA-DRB1*15:01). To assess the potential immunomodulatory role of NAPs, molecular dynamics (MD) simulations, solvent-accessible surface area (SASA) analysis, and electrostatic potential mapping were also conducted. Key epitopes-L11, N25, and C10-showed strong binding affinities to HLA-DQA1*01:02, HLA-DQB1*06:04, and HLA-DQA1*03:03, indicating a potential immunodominant role. NAPs did not obstruct these epitopes but slightly increased their exposure and appeared to stabilize the toxin structure. Electrostatic mapping and binding free energy calculations suggested no significant immunogenic shift in the presence of NAPs. BoNT-A immunogenicity appears to be influenced by HLA allele variability, reinforcing the value of patient-specific genetic profiling. The presumed immunogenic role of NAPs remains unsubstantiated at the molecular level, underscoring the need for evidence-based evaluation over commercial rhetoric. While these findings provide valuable molecular insight, it is important to acknowledge that they are derived entirely from in silico analyses. As such, experimental validation remains essential to confirm the immunological relevance of these predicted interactions. Nonetheless, this computational framework offers a rational basis for guiding future clinical research and the development of HLA-informed BoNT-A therapies.

Protocol and Demographics of the RELY-CD Study: Assessing Long-Term Clinical Response to Botulinum Neurotoxin in Cervical Dystonia

The RELY-CD study investigated the long-term clinical response to botulinum neurotoxin type A in cervical dystonia within a multicenter, real-world setting. This retrospective study focused on patients treated with complex-free (incobotulinumtoxinA) and complex-containing (onabotulinumtoxinA and abobotulinumtoxinA) BoNT/A formulations over an up to 10-year period. The novel dose-effect parameter "DEff" was introduced to quantify the relationship between dose adjustments and clinical outcomes, enabling the identification of partial treatment failures. The primary endpoint was a comparison of a clinically meaningful worsening in DEff in treatment year 7 compared to year 2 between complex-free and complex-containing botulinum neurotoxin type A. The RELY-CD study provides unique insights into long-term treatment patterns, clinical resistance phenomena, and the implications of formulation differences on treatment outcomes, addressing a critical gap in the literature on real-world botulinum neurotoxin type A application. The study methodology, including the definition and calculation of the novel DEff, as well as clinical baseline characteristics, are presented.

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.

Identifying Different Immunoresistance Risk Profiles Among Experienced Aesthetic Botulinum Neurotoxin A Recipients: A Latent Class Analysis

BACKGROUND

Immunoresistance to botulinum neurotoxin A (BoNT-A) due to neutralizing antibodies (NAbs) can lead to partial or complete secondary nonresponse (SNR), potentially limiting individuals' aesthetic and/or medical therapeutic options in the short and/or long term. Understanding factors directly or indirectly influencing BoNT-A immunoresistance risk is crucial.

AIMS

This analysis explored patterns of latent risk factors (biological and behavioral) that may influence the risk of developing BoNT-A immunoresistance among experienced aesthetic BoNT-A recipients.

METHODS

Latent class analysis (LCA) was applied to survey data from 363 experienced BoNT-A recipients from six Asia-Pacific countries to identify distinct subgroups based on their patterns of risk factor or risk proxy variables. The five risk proxy variables used for modeling capture information on BoNT-A treatments (treatment indications/locations as proxies for dose), symptoms of declining efficacy, number of aesthetic treatments over the past 3 years, and clinic and BoNT-A formulation switching behaviors. These represent established risk factors and treatment-seeking behaviors suggested to influence immunoresistance risk.

RESULTS

LCA identified 3 distinct profiles of individuals, which we described based on the observed patterns of risk proxies as: "lower-risk" (55%), "moderate-risk" (39%), and "higher-risk" (6%). Individuals in the "higher-risk" profile reported higher BoNT-A exposure, more symptoms of declining efficacy, and distinct patterns of knowledge and attitudes toward BoNT-A immunoresistance that could account for their treatment-seeking behaviors.

CONCLUSIONS

This study suggests that individual behaviors (the "human factor") have a notable influence on BoNT-A immunoresistance risk. Gaining deeper insights into these factors could support more targeted and effective interventions to mitigate risk.

Phase I Trial to Assess the Safety, Tolerability, and Preliminary Efficacy of OBI-858 for Treatment of Glabellar Lines

INTRODUCTION

OBI-858 is a brand-new botulinum Type A complex toxin with a specific molecular weight of 760 kDa intended for development for both aesthetic and therapeutic applications. This is a phase I, dose-escalation study to evaluate the safety and preliminary efficacy of OBI-858 in subjects with moderate to severe glabellar lines.

METHODS

Each subject received OBI-858 by intramuscular injections with an assigned dose (10 U, 20 U, and 30 U). The safety and preliminary efficacy were evaluated at each of the in-person visits.

RESULTS

A total of 36 subjects (12 subjects per cohort) were enrolled. The response rates (≥ 1 point) for all groups at maximum frown were assessed at week 4 were 100%. The initial improvement for 30 U occurred at day 3. Response rates revealed benefits lasting 4-6 months or longer. Subject satisfaction at week 4 was high in all groups. Adverse effects were mild and infrequent. Among them, one subject had drug-related AE, and one subject had grade ≥ 3 unrelated AE.

CONCLUSIONS

This study demonstrated that OBI-858 is well tolerated and showed preliminary efficacy. Overall, the OBI-858 has a clinically favorable profile of safety and efficacy that warrants proceeding to the next studies.

Temporary Delayed Hypersensitivity Reaction to Botulinum Toxin-A After COVID-19 Vaccination: A Case Series

PURPOSE

The occurrence of a hypersensitivity reaction with the injection of botulinum toxin type A (BTX-A) in cosmetic use is a rare complication. We report the largest case series of temporary delayed hypersensitivity reaction (DHR) with BTX-A following COVID-19 vaccination and the first cases to incobotulinum toxin A (incoBTX-A).

METHODS

A retrospective multicentric case series of patients who developed a DHR to BTX-A after COVID-19 vaccination.

RESULTS

Twelve patients were treated with BTX-A injections for the management of facial rhytids. The age range was between 29 and 45 years. Ten (83.3%) were female. Ten (83.3%) patients received incoBTX-A, and two received onabotulinum toxin A (onaBTX-A). All patients had COVID-19 vaccination (mRNA vaccine) between 1 and 7 months before. Within an average time of 24 h after BTX-A injection, all patients developed progressive facial swelling and erythema that were more prominent at the injection points. Intradermal allergic tests to BTX-A were performed in six (50%) patients, and the results were all negative. Adequate clinical control was achieved with systemic corticosteroids and antihistamines. After 1 year with no further vaccination, a new BTX-A treatment (provocation test) was performed in all patients with no secondary effects.

CONCLUSION

Previous COVID-19 vaccination and the absence of new adverse events with further BTX-A injections suggest a temporary DHR. Clinicians should be aware of the importance of immunization history and its potential post-vaccine immunogenic effects with BTX-A.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Continuous Treatment with IncobotulinumtoxinA Despite Presence of BoNT/A Neutralizing Antibodies: Immunological Hypothesis and a Case Report

Botulinum Neurotoxin A (BoNT/A) is a bacterial protein that has proven to be a valuable pharmaceutical in therapeutic indications and aesthetic medicine. One major concern is the formation of neutralizing antibodies (nAbs) to the core BoNT/A protein. These can interfere with the therapy, resulting in partial or complete antibody (Ab)-mediated secondary non-response (SNR) or immunoresistance. If titers of nAbs reach a level high enough that all injected BoNT/A molecules are neutralized, immunoresistance occurs. Studies have shown that continuation of treatment of neurology patients who had developed Ab-mediated partial SNR against complexing protein-containing (CPC-) BoNT/A was in some cases successful if patients were switched to complexing protein-free (CPF-) incobotulinumtoxinA (INCO). This seems to contradict the layperson's basic immunological understanding that repeated injection with the same antigen BoNT/A should lead to an increase in antigen-specific antibody titers. As such, we strive to explain how immunological memory works in general, and based on this, we propose a working hypothesis for this paradoxical phenomenon observed in some, but not all, neurology patients with immunoresistance. A critical factor is the presence of potentially immune-stimulatory components in CPC-BoNT/A products that can act as immunologic adjuvants and activate not only naïve, but also memory B lymphocyte responses. Furthermore, we propose that continuous injection of a BoN/TA formulation with low immunogenicity, e.g., INCO, may be a viable option for aesthetic patients with existing nAbs. These concepts are supported by a real-world case example of a patient with immunoresistance whose nAb levels declined with corresponding resumption of clinical response despite regular INCO injections.

Immunogenicity of Botulinum Toxin A: Insights

BACKGROUND

Botulinum toxin A (BoNT-A) is widely used in treating dystonia and spasticity to managing chronic migraine and cosmetic applications. However, its immunogenic potential presents challenges, such as the development of neutralizing antibodies that lead to diminished therapeutic efficacy over time, known as secondary nonresponse.

OBJECTIVE

This review aims to bridge the knowledge gap regarding the immunogenic mechanisms of BoNT-A and to explore effective management strategies to mitigate these immune responses.

MATERIALS AND METHODS

The authors conducted a systematic search in databases including PubMed, Embase, and Web of Science, using keywords related to BoNT-A's immunogenicity. The selection process refined 157 initial articles down to 23 relevant studies, which underwent analysis to investigate the underlying mechanisms of immunogenicity and the factors influencing it.

RESULTS

The analysis revealed that both the neurotoxin component and the neurotoxin-associated proteins could elicit an immune response. However, only antibodies against the core toxin influence therapeutic outcomes. Various patient-specific factors such as genetic predispositions and prior immune experiences, along with treatment-related factors such as dosage and frequency, play crucial roles in shaping these responses.

CONCLUSION

Understanding the specific immunogenic triggers and responses to BoNT-A is critical for optimizing treatment protocols and improving patient outcomes.

IncobotulinumtoxinA for Aesthetic Treatments: Review and Recommendations From Latin America

BACKGROUND

As new aesthetic treatment techniques are developed, the understanding of botulinum toxin type A safety and treatment outcomes continues to evolve.

OBJECTIVE

This article was developed to provide a comprehensive up-to-date reference for clinicians using incobotulinumtoxinA (INCO; Xeomin/Bocouture, Merz Pharmaceuticals GmbH, Frankfurt, Germany) for aesthetic treatments.

PATIENTS AND METHODS/MATERIALS

A Latin American panel of 11 physicians was assembled to discuss and develop recommendations on the use of INCO for aesthetic treatment based on the literature review and their private medical practice.

RESULTS

The panel found that INCO is a highly purified botulinum toxin, without other clostridial proteins (hemagglutinins and nonhemagglutinins). IncobotulinumtoxinA has proven its efficacy and duration over time, maintaining response after multiple treatment cycles.

CONCLUSION

This recommendation provides up-to-date information on the use of INCO for aesthetic treatment, focusing on the differential properties of this product regarding its purity, performance, customization, and patient satisfaction.

Real-world Implications of Botulinum Neurotoxin A Immunoresistance for Consumers and Aesthetic Practitioners: Insights from ASCEND Multidisciplinary Panel

Background

As long-term, regular aesthetic botulinum neurotoxin A (BoNT-A) use becomes more commonplace, it is vital to understand real-world risk factors and impact of BoNT-A immunoresistance. The first Aesthetic Council on Ethical Use of Neurotoxin Delivery panel discussed issues relating to BoNT-A immunoresistance from the health care professionals' (HCPs') perspective. Understanding the implications of BoNT-A immunoresistance from the aesthetic patient's viewpoint allows HCPs to better support patients throughout their aesthetic treatment journey.

Methods

A real-world consumer study surveyed 363 experienced aesthetic BoNT-A recipients across six Asia-Pacific territories. The survey mapped participants' BoNT-A aesthetic treatment journey and characterized awareness and attitudes relating to BoNT-A immunoresistance and treatment implications. At the second Aesthetic Council on Ethical use of Neurotoxin Delivery meeting, panelists discussed survey findings and developed consensus statements relating to the impact of BoNT-A immunoresistance on the aesthetic treatment journey.

Results

Aesthetic BoNT-A patients' depth of knowledge about BoNT-A immunoresistance remains low, and risk/benefit communications need to be more lay-friendly. The initial consultation is the most important touchpoint for HCPs to raise awareness of BoNT-A immunoresistance as a potential side effect considering increased risk with repeated high-dose treatments. HCPs should be cognizant of differences across BoNT-A formulations due to the presence of certain excipients and pharmacologically unnecessary components that can increase immunogenicity. Standardized screening for clinical signs of secondary nonresponse and a framework for diagnosing and managing immunoresistance-related secondary nonresponse were proposed.

Conclusion

These insights can help patients and HCPs make informed treatment decisions to achieve desired aesthetic outcomes while preserving future treatment options with BoNT-A.

Mild Allergic Reactions after Botulinum Toxin Injection: A Case Series and Literature Review

Background

Botulinum toxin type A (BTA) is becoming more and more prevalent as an injection agent in cosmetic surgery. However, there is an increasing amount of cases reporting unexpected adverse reactions related to BTA injection. BTA can invoke many kinds of hypersensitive reactions, some of which can be delayed-type or even fatal; hence, it is of crucial importance to pay close attention to atypical and early symptoms that may indicate the presence of BTA allergy in patients.

Methods

In this study, we reported three cases of mild and unexpected BTA-related hypersensitive reaction with a symptom of nonpruritic erythema on the chest that happened after BTA treatment of upper facial wrinkles and proposed several suggestions based on our practical experience and literature review.

Results

Two patients' symptoms were alleviated spontaneously, and one patient's were alleviated after taking oral corticosteroid. According to our literature review, we believe that these incidences indicate a kind of unreported allergic reaction relevant to botulinum toxin.

Conclusions

We suggest clinicians consider warily patients' subsequent BTA injection schedule if any suspicious reaction occurs after treatment. We suggest that patients who experience nonpruritic erythema after botulinum toxin injection should suspend subsequent injection plans for at least 3 months to prevent more severe consequences.

Some Examples of Bacterial Toxins as Tools

Pathogenic bacteria produce diverse protein toxins to disturb the host's defenses. This includes the opening of epithelial barriers to establish bacterial growth in deeper tissues of the host and to modulate immune cell functions. To achieve this, many toxins share the ability to enter mammalian cells, where they catalyze the modification of cellular proteins. The enzymatic activity is diverse and ranges from ribosyl- or glycosyl-transferase activity, the deamidation of proteins, and adenylate-cyclase activity to proteolytic cleavage. Protein toxins are highly active enzymes often with tight specificity for an intracellular protein or a protein family coupled with the intrinsic capability of entering mammalian cells. A broad understanding of their molecular mechanisms established bacterial toxins as powerful tools for cell biology. Both the enzymatic part and the pore-forming/protein transport capacity are currently used as tools engineered to study signaling pathways or to transport cargo like labeled compounds, nucleic acids, peptides, or proteins directly into the cytosol. Using several representative examples, this review is intended to provide a short overview of the state of the art in the use of bacterial toxins or parts thereof as tools.

The Role of Botulinum Toxin Type-A in Spasticity: Research Trends from a Bibliometric Analysis

Botulinum toxin type-A (BoNT-A) has emerged as a key therapeutic agent for the management of spasticity. This paper presents a comprehensive bibliometric and visual analysis of research concerning BoNT-A treatment of spasticity to elucidate current trends and future directions in this research area. A search was conducted in the Web of Science database for articles focused on the use of BoNT-A in spasticity published between 2000 and 2022. We extracted various metrics, including counts of publications and contributions from different countries, institutions, authors, and journals. Analytical methods in CiteSpace were employed for the examination of co-citations, collaborations, and the co-occurrence of keywords. Our search yielded 1489 publications. Analysis revealed a consistent annual increase in research output. The United States, United Kingdom, and Italy were the leading contributors. The top institution in this research was Assistance Publique Hopitaux, Paris. The journal containing the highest number of relevant publications was Toxins. Key frequently occurring keywords were 'stroke', 'cerebral palsy', 'adult spasticity', and 'upper extremity'. This study identified 12 clusters of keywords and 15 clusters of co-cited references, indicating the main focus areas and emerging themes in this field. This study comprehensively analyzed and summarized trends in BoNT-A research in the field of spasticity over the past 22 years.

Recent Developments in Engineering Non-Paralytic Botulinum Molecules for Therapeutic Applications

This review discusses the expanding application of botulinum neurotoxin in treating neurological conditions. The article specifically explores novel approaches to using non-paralytic botulinum molecules. These new molecules, such as BiTox or el-iBoNT, offer an alternative for patients who face limitations in using paralytic forms of botulinum neurotoxin due to concerns about muscle function loss. We highlight the research findings that confirm not only the effectiveness of these molecules but also their reduced paralytic effect. We also discuss a potential cause for the diminished paralytic action of these molecules, specifically changes in the spatial parameters of the new botulinum molecules. In summary, this article reviews the current research that enhances our understanding of the application of new botulinum neurotoxins in the context of common conditions and suggests new avenues for developing more efficient molecules.

Complexing Protein-Free Botulinum Neurotoxin A Formulations: Implications of Excipients for Immunogenicity

The formation of neutralizing antibodies is a growing concern in the use of botulinum neurotoxin A (BoNT/A) as it may result in secondary treatment failure. Differences in the immunogenicity of BoNT/A formulations have been attributed to the presence of pharmacologically unnecessary bacterial components. Reportedly, the rate of antibody-mediated secondary non-response is lowest in complexing protein-free (CF) IncobotulinumtoxinA (INCO). Here, the published data and literature on the composition and properties of the three commercially available CF-BoNT/A formulations, namely, INCO, Coretox® (CORE), and DaxibotulinumtoxinA (DAXI), are reviewed to elucidate the implications for their potential immunogenicity. While all three BoNT/A formulations are free of complexing proteins and contain the core BoNT/A molecule as the active pharmaceutical ingredient, they differ in their production protocols and excipients, which may affect their immunogenicity. INCO contains only two immunologically inconspicuous excipients, namely, human serum albumin and sucrose, and has demonstrated low immunogenicity in daily practice and clinical studies for more than ten years. DAXI contains four excipients, namely, L-histidine, trehalosedihydrate, polysorbate 20, and the highly charged RTP004 peptide, of which the latter two may increase the immunogenicity of BoNT/A by introducing neo-epitopes. In early clinical studies with DAXI, antibodies against BoNT/A and RTP004 were found at low frequencies; however, the follow-up period was critically short, with a maximum of three injections. CORE contains four excipients: L-methionine, sucrose, NaCl, and polysorbate 20. Presently, no data are available on the immunogenicity of CORE in human beings. It remains to be seen whether all three CF BoNT/A formulations demonstrate the same low immunogenicity in patients over a long period of time.

Efficacy and Safety Analysis of Botox Application and Iatrogenic Botulism: Panacea or Peril?

Clostridium botulinum toxin-A (BoNT-A) creates temporary paralysis in the muscles by acting on the muscle-nerve junction. It is injected into the mimic muscles when a decrease in the movements of the mimic muscles is desired. Despite many favorable applications, the use of BoNT-A is not without drawbacks. Although there is no expected serious side effect on health in BoNT-A treatments, various problems can be encountered in patients treated for aesthetic purposes. Botulism is a rare but potentially life-threatening syndrome, which is caused by the toxin produced by the bacterium Clostridium botulinum, which acts on the nervous system, vegetative forms of C. botulinum can only survive in anaerobic conditions, while spore forms are common in nature and can withstand harsh conditions. Botulism can stem from bacterial spores which release toxin in the body; in the form of enteric botulism, and wound botulism. The cases that develop 'iatrogenic botulism' after such procedures are usually those receiving high-dose toxin for therapeutic purposes. The treatment of botulism mainly consists of anti-toxin therapy and, if necessary, intensive care to prevent organ failures, including respiratory support. This article aims to cover all these issues related to botulism and other adverse outcomes related to BoNT-A injection in light of the most recent literature.

The analgesic effects of botulinum neurotoxin by modulating pain-related receptors; A literature review

Botulinum neurotoxins (BoNTs), produced by Clostridium botulinum, have been used for the treatment of various central and peripheral neurological conditions. Recent studies have suggested that BoNTs may also have a beneficial effect on pain conditions. It has been hypothesized that one of the mechanisms underlying BoNTs' analgesic effects is the inhibition of pain-related receptors' transmission to the neuronal cell membrane. BoNT application disrupts the integration of synaptic vesicles with the cellular membrane, which is responsible for transporting various receptors, including pain receptors such as TRP channels, calcium channels, sodium channels, purinergic receptors, neurokinin-1 receptors, and glutamate receptors. BoNT also modulates the opioidergic system and the GABAergic system, both of which are involved in the pain process. Understanding the cellular and molecular mechanisms underlying these effects can provide valuable insights for the development of novel therapeutic approaches for pain management. This review aims to summarize the experimental evidence of the analgesic functions of BoNTs and discuss the cellular and molecular mechanisms by which they can act on pain conditions by inhibiting the transmission of pain-related receptors.

Improvement in Quality-of-Life-Related Outcomes Following Treatment with IncobotulinumtoxinA in Adults with Limb Spasticity: A Pooled Analysis

A strong correlation has been reported between patient-reported quality of life (QoL) and the investigator-rated Disability Assessment Scale (DAS) in patients with spasticity. The current analysis evaluates the effect of incobotulinumtoxinA on QoL-related outcomes (limb position abnormality, as well as dressing- and hygiene-related disability, measured with the DAS) in adults with upper limb spasticity, using pooled data from six studies. Separate analyses for each DAS domain were performed using data from patients with disabilities for that domain (DAS score ≥1). Results showed that a significantly greater proportion of incobotulinumtoxinA-treated compared with placebo-treated patients achieved a ≥1-point reduction from baseline in each of the DAS domains (improvement) 4 weeks after the first injection. The benefits of incobotulinumtoxinA were observed regardless of the baseline severity of DAS impairment and of the time elapsed since stroke. The effects of incobotulinumtoxinA 4 weeks after injection were maintained or enhanced over multiple injection cycles for all three DAS domains, supporting the use of repeated injection cycles to provide sustained QoL benefit. IncobotulinumtoxinA represents an important treatment option to achieve better QoL-related outcomes for patients with upper limb spasticity, irrespective of the duration of their condition.

Consensus Statement on the Use of Botulinum Neurotoxin in the Middle East

Background

Aesthetic minimally invasive procedures have become very popular and culturally acceptable among Middle Eastern populations. Botulinum neurotoxin type A (BoNTA) is a valuable treatment modality for many cosmetic as well as therapeutic indications. The presence of BoNTA in our toolkit has revolutionized the field of aesthetic medicine to the point where it is now one of the most commonly performed cosmetic procedures worldwide. This consensus considers popular on- and off-label BoNTA indications in the Middle East.

Methods

A multinational group of ten key opinion leaders, experts in facial plastic surgery and dermatology, convened the Middle East Aesthetics Consensus Group and reviewed the aesthetic applications of BoNTA. Recommendations and position statements were drafted based on the integration of the panel's clinical experience with published data, targeted to the practices implemented in the Middle Eastern and the global population.

Results

Guidance statements are presented covering Middle Eastern facial characteristics and beauty ideals, BoNTA characteristics, pre-operative counselling, treatment indications and anatomical considerations, off-label and special uses including high-dose recommendations, and post-treatment advice. Throughout, an evidence-based approach to selection of products and injection techniques is provided, supplemented by the experts' advice on injections dosages and placement.

Conclusion

This consensus reflects the knowledge and expertise of physicians practicing in the Middle East. The panel acknowledged the use of on-label indications and variability in the toxin formulations and immunogenicity and agreed upon a wide use of "off-label" indications.

Mechanism and clinical use of botulinum neurotoxin in head and facial region

PURPOSE

Botulinum neurotoxin (BoNT) is a biological toxin produced by Clostridium botulinum. BoNT is a potent toxin extensively used in therapeutic interventions. This review provides an updated overview of the mechanisms of action and clinical applications of BoNT in head and facial region.

STUDY SELECTION

MEDLINE/PubMed searches were conducted using the terms "botulinum neurotoxin" and "dentistry" along with a combination of other related terms. In addition, studies were manually selected from reference lists of the selected articles.

RESULTS

The Food and Drug Administration in the United States initially approved BoNT to treat strabismus, blepharospasm, and hemifacial spasms. The use of BoNT in dermatology and cosmetics has been widely established and has created a revolution in these fields. Over the years, its applications in various medical specialties have expanded widely. Owing to its safety, efficacy, and long duration of action, it is well-accepted by patients. BoNT/A and BoNT/B are widely used in clinical practice. Several off-label uses of BoNT in the dental fraternity have yielded promising results. We have elaborated on the speculated mechanism of action, dosage, effective sites of injection, and adverse effects of each therapeutic application. The various clinical indications for BoNT include bruxism, myofascial pain, temporomandibular joint dislocation, hemifacial pain, orofacial dystonia, facial paralysis, chronic migraine, and trigeminal neuralgia.

CONCLUSIONS

BoNT is a safe treatment that can be used effectively, provided that the clinician has adequate knowledge regarding the mechanism, injection techniques, and local and systemic side effects and that it is administered cautiously and purposefully.

Ideal Injection Points for Botulinum Neurotoxin for Pectoralis Minor Syndrome: A Cadaveric Study

Pectoralis Minor Syndrome (PMS) causes significant discomfort due to the compression of the neurovascular bundle within the retropectoralis minor space. Botulinum neurotoxin (BoNT) injections have emerged as a potential treatment method; however, their effectiveness depends on accurately locating the injection site. In this study, we aimed to identify optimal BoNT injection sites for PMS treatment. We used twenty-nine embalmed and eight non-embalmed human cadavers to determine the origin and intramuscular arborization of the pectoralis minor muscle (Pm) via manual dissection and Sihler's nerve staining techniques. Our findings showed the Pm's origin near an oblique line through the suprasternal notch, with most neural arborization within the proximal three-fourths of the Pm. Blind dye injections validated these results, effectively targeting the primary neural arborized area of the Pm at the oblique line's intersection with the second and third ribs. We propose BoNT injections at the arborized region within the Pm's proximal three-fourths, or the C region, for PMS treatment. These findings guide clinicians towards safer, more effective BoNT injections.

Unusual herpetic reactivation in a young female following botox injection: a case report study

BACKGROUND

Botox injections are commonly used for cosmetic and therapeutic purposes because they temporarily paralyze muscles, reduce wrinkles, and alleviate certain medical conditions. Although generally considered safe and effective, Botox injections may cause potential complications. While herpes reactivation is more commonly associated with immunosuppressive therapies, such as chemotherapy or corticosteroid use, its association with Botox injection is poorly documented.

CASE PRESENTATION

A 33-year-old woman presented with progressive painful rashes and vesicles on her forehead, scalp, and right upper eyelid, accompanied by fever and malaise following a Botox injection to treat wrinkles. A positive Tzanck smear test result confirmed the diagnosis of herpes infection. The patient was treated with antiviral medication, and her symptoms gradually regressed over several days.

CONCLUSIONS

Although herpes reactivation is more commonly associated with immunosuppressive therapies, few cases of herpes zoster and herpes simplex following Botox injection have been reported. The pathogenesis of herpes reactivation following Botox injection is unclear; however, it has been hypothesized that the Botox protein is a potent antigen that may activate the cellular immune system, making it easier for the virus to reactivate. Healthcare providers should be aware of this potential complication and consider it when evaluating patients who present with painful rashes following Botox injections. In addition, individuals who want to receive Botox injections should be informed of this complication. The diagnosis of herpetic infection should be made promptly, and antiviral therapy should be initiated to minimize the risk of complications. Further research is needed to better understand the pathogenesis and risk factors for herpes following Botox injection and to develop strategies for preventing and managing this complication.

SAMCEP Society consensus on the treatment of upper facial lines with botulinum neurotoxin type A: A tailored approach

BACKGROUND

The safety and efficacy of botulinum neurotoxin type A (BoNTA) treatments are well established, but injection techniques, target muscles, and toxin doses continue to evolve, with each refinement producing improvements in treatment outcomes. The recommendations in this consensus move away from standard templates and illustrate how to tailor treatments to individual patterns and strengths of muscle activity, and patient preferences.

METHODS

Seventeen experts in the fields of plastic surgery, dermatology, ophthalmology, otorhinolaryngology, and neurology convened in 2022 to develop consensus-based recommendations for the use of botulinum toxin A for the treatment of horizontal forehead lines, glabellar frown lines, and crow's feet lines that reflect current clinical practice. The focus was on how to tailor injections to individual patients to optimize treatment outcomes.

RESULTS

For each upper face indication, consensus members describe how to perform a dynamic assessment to optimize the dose and injection technique for each patient. A tailored treatment protocol is presented for commonly observed patterns of dynamic lines. Units of Inco are defined and the precise location of injection points, illustrated with the use of anatomical images.

CONCLUSION

This consensus provides up-to-date recommendations on the tailored treatment of upper facial lines based on the latest research and collective clinical experience of the expert injectors. Optimal outcomes require thorough patient evaluation, both at rest and during animation, using both visual and tactile cues; detailed understanding of facial muscular anatomy and how opposing muscles interact; and use of a BoNTA with high precision to target identified zones of excess muscle activity.

Therapeutic Applications of Botulinum Neurotoxins in Veterinary Medicine

Botulinum neurotoxins (BoNTs) are emerging as multipurpose therapeutic compounds for the treatment of several different syndromes involving peripheral and central nervous systems, and muscular and musculoskeletal disorders both in human and veterinary medicine. Therefore, the study of BoNTs is rapidly developing and identifying newly produced BoNT variants. Efforts should be made to clarify the biological and pharmacological characteristics of these novel BoNTs as well as the natural ones. The high potential of BoNTs as a therapeutic compound for medical syndromes lies in its ability to reach a specific cell type while bypassing other cells, thus having mild or no side effects. In this paper the recent developments in BoNTs are reviewed with the aim of analyzing the current knowledge on BoNTs' biological mechanisms of action, immunogenicity, formulations, and therapeutic applications in the veterinary field, highlighting advantages and drawbacks and identifying the gaps to be filled in order to address research priorities.

Bruxism and Botulinum Injection: Challenges and Insights

Botulinum toxin (BTA) is a bacterial-derived extract that can inhibit muscle contraction, acting directly on the absorption of acetylcholine. Thanks to this property, botulinum has been used in aesthetic and general medicine for several years. Nowadays, the use of botulinum toxin is being deepened to address the problem of bruxism. In this scoping review, the results of the studies in the literature of the last 10 years were analyzed. Indeed, 12 reports (found on PubMed, Web of Science, and Scopus, entering the keywords "BRUXISM" and "BOTULINUM TOXIN") were deemed eligible for inclusion in this review. In the studies reviewed, BTA was injected into different muscle groups: masseters, masseter and temporalis or masseter, temporalis, and medial pterygoid. Botulinum toxin injection is a viable therapeutic solution, especially in patients with poor compliance or without improvement in conventional treatment.

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.

Neutralizing Antibody Formation with OnabotulinumtoxinA (BOTOX®) Treatment from Global Registration Studies across Multiple Indications: A Meta-Analysis

Though the formation of neutralizing antibodies (NAbs) during treatment with botulinum neurotoxin is rare, their presence may nonetheless affect the biological activity of botulinum toxin and negatively impact clinical response. The goal of this updated meta-analysis was to evaluate and characterize the rate of NAb formation using an expanded dataset composed of 33 prospective placebo-controlled and open-label clinical trials with nearly 30,000 longitudinal subject records prior to and following onabotulinumtoxinA treatment in 10 therapeutic and aesthetic indications. Total onabotulinumtoxinA doses per treatment ranged from 10 U to 600 U administered in ≤15 treatment cycles. The NAb formation at baseline and post-treatment was tested and examined for impact on clinical safety and efficacy. Overall, 27 of the 5876 evaluable subjects (0.5%) developed NAbs after onabotulinumtoxinA treatment. At study exit, 16 of the 5876 subjects (0.3%) remained NAb positive. Due to the low incidence of NAb formation, no clear relationship was discernable between positive NAb results and gender, indication, dose level, dosing interval, treatment cycles, or the site of injection. Only five subjects who developed NAbs post-treatment were considered secondary nonresponders. Subjects who developed NAbs revealed no other evidence of immunological reactions or clinical disorders. This comprehensive meta-analysis confirms the low NAb formation rate following onabotulinumtoxinA treatment across multiple indications, and its limited clinical impact on treatment safety and efficacy.

Sensory Symptoms Associated with Aesthetic Botulinum Toxin A Treatments

A retrospective review of patients who switched from onabotulinumtoxinA (onaA) and/or abobotulinumtoxinA (aboA) to incobotulinumtoxinA (incoA) found anecdotal reports of differences in "feel," including a "lighter" feel or treatment-associated tightness. We surveyed the frequency of these sensations as an initial proof of concept of toxin proprioception among our patients who switched toxins.

METHODS

Seventy-nine patients who had past facial aesthetic treatments with more than one botulinum toxin A (BoNT/A) formulation completed a questionnaire on their experience of treatment-associated sensations, including stiffness or a frozen feeling.

RESULTS

Treatment-associated sensations of tightness (47.3%), headache (41.8%), heaviness (38.2%), feeling frozen (29.1%), stiffness (20.0%), and weakness (20.0%) were reported by 55 of 79 patients. Furthermore, 78.2% of 55 patients noted an interformulation sensory difference. Of 79 patients surveyed, 68.4% of onaA-treated patients associated sensations with onaA, 39.1% of aboA-treated patients associated sensations with aboA, and 12.2% of incoA-treated patients associated sensations with incoA.

CONCLUSIONS

Some patients reported a different feel between toxins, and the difference in frequency of treatment-associated sensation varies between the different formulations used. Given the fine coordination of facial expressive muscles, we suspect that associated proprioceptive afferents are involved. Our findings confirm that post-toxin treatment-associated sensations can be detected by some patients, and this is likely due to the variations between the formulations. Failing to advise patients of this before switching formulations may cause a misperception that the treatment is not working well or that its effect has worn off prematurely, and some patients may consider switching formulations to reduce these conscious proprioceptive sensations.

Safety Profile and Lack of Immunogenicity of IncobotulinumtoxinA in Pediatric Spasticity and Sialorrhea: A Pooled Analysis

IncobotulinumtoxinA, a pure botulinumtoxinA formulation, is free of accessory proteins. This analysis provides pooled safety data from phase 3 trials of children/adolescents (2-17 years), investigating incobotulinumtoxinA for the treatment of spasticity associated with cerebral palsy (at doses ≤20 U/kg (max. 500 U) per injection cycle (IC) for ≤6 ICs; three trials) or sialorrhea associated with neurologic disorders (at total doses of 20-75 U per IC for ≤4 ICs; one trial) for ≤96 weeks. Safety endpoints included the incidences of different types of treatment-emergent adverse events (TEAEs) and immunogenicity. IncobotulinumtoxinA dose groups were combined. Of 1159 patients (mean age 7.3 years, 60.4% males) treated with incobotulinumtoxinA, 3.9% experienced treatment-related TEAEs, with the most common being injection site reactions (1.3%) (both indications), muscular weakness (0.7%) (spasticity), and dysphagia (0.2%) (sialorrhea). Two patients (0.2%) experienced a treatment-related treatment-emergent serious adverse event, and 0.3% discontinued the study due to treatment-related TEAEs. No botulinumtoxinA-naïve patients developed neutralizing antibodies (NAbs) after incobotulinumtoxinA. All children/adolescents with known pre-treatment status and testing positive for Nabs at final visit (n = 7) were previously treated with a botulinumtoxinA other than incobotulinumtoxinA. IncobotulinumtoxinA was shown to be safe, with very few treatment-related TEAEs in a large, diverse cohort of children/adolescents with chronic conditions requiring long-term treatment and was without new NAb formation in treatment-naïve patients.

Emerging Trends in Botulinum Neurotoxin A Resistance: An International Multidisciplinary Review and Consensus

Botulinum neurotoxin A (BoNT-A) injection is the most widely performed aesthetic procedure and a first-line therapeutic option for various medical conditions. The potential for BoNT-A immunoresistance and secondary nonresponse related to neutralizing antibody (NAb) formation warrants attention as the range of BoNT-A aesthetic applications continues to expand.

Methods

An international multidisciplinary panel reviewed published evidence on BoNT-A immunoresistance in aesthetic and therapeutic applications and discussed best practices integrating clinical, ethical, and aesthetic considerations. Consensus statements relating to awareness, assessment, and management of the risk of NAb-related secondary nonresponse in aesthetic practice were developed.

Results

There was a consensus that, as doses used in aesthetic practice become like those in therapeutics, rates of NAb formation may be expected to increase. However, the true extent of NAb formation in aesthetics is likely underestimated due to limitations of published evidence and variability in treatment patterns of aesthetic patients. Since BoNT-A therapy is often lifelong, practitioners need to recognize immunogenicity as a potential complication that might affect future therapeutic use and strive to minimize modifiable risk factors. The selection and use of a BoNT-A product with the least immunogenic potential from the beginning may thus be advantageous, especially when treatment with high doses is planned.

Conclusions

In view of current trends in BoNT-A aesthetic use, it is essential for practitioners to conduct thorough clinical assessments, inform patients of treatment risks, and develop BoNT-A treatment plans to minimize immunogenicity. This can help preserve the option of continued or future BoNT-A treatment with satisfactory outcomes.

Comparative Pharmacodynamics of Three Different Botulinum Toxin Type A Preparations following Repeated Intramuscular Administration in Mice

Botulinum neurotoxin type A (BoNT/A) causes muscle paralysis by blocking cholinergic signaling at neuromuscular junctions and is widely used to temporarily correct spasticity-related disorders and deformities. The paralytic effects of BoNT/A are time-limited and require repeated injections at regular intervals to achieve long-term therapeutic benefits. Differences in the level and duration of effectivity among various BoNT/A products can be attributed to their unique manufacturing processes, formulation, and noninterchangeable potency units. Herein, we compared the pharmacodynamics of three BoNT/A formulations, i.e., Botox^® (onabotulinumtoxinA), Xeomin^® (incobotulinumtoxinA), and Coretox^®, following repeated intramuscular (IM) injections in mice. Three IM injections of BoNT/A formulations (12 U/kg per dose), 12-weeks apart, were administered at the right gastrocnemius. Local paresis and chemodenervation efficacy were evaluated over 36 weeks using the digit abduction score (DAS) and compound muscle action potential (CMAP), respectively. One week after administration, all three BoNT/A formulations induced peak DAS and maximal reduction of CMAP amplitudes. Among the three BoNT/A formulations, only Coretox^® afforded a significant increase in paretic effects and chemodenervation with a prolonged duration of action after repeated injections. These findings suggest that Coretox^® may offer a better overall therapeutic performance in clinical settings.

[Treatment of Sialorrhea with Botulinum Neurotoxin Type A - Consensus Practice Recommendations for Children and Adults]

Sialorrhea, uncontrolled, excessive drooling, accompanies different, mostly neurological disorders from childhood to adulthood. With incobotulinumtoxinA (Xeomin, IncoBoNT/A, Merz Pharmaceuticals GmbH), an approved medication for the treatment of sialorrhea has been available since 2019. Patient selection, possible therapy goals, treatment and the management of specific treatment situations build the focus of this interdisciplinary expert consensus recommendations with the intent to facilitate access to treatment and to contribute to qualified botulinum toxin therapy.

Immunogenicity Associated with Aesthetic Botulinumtoxin A: A Survey of Asia-Pacific Physicians' Experiences and Recommendations

Background:

Most botulinum toxin A (BoNT/A) products contain unnecessary bacterial components that increase the risk of developing neutralizing antibodies (nAbs). Reports of secondary nonresponse and treatment failures (STF) due to nAbs have accompanied a surge in new BoNT/A products.

Methods:

To formulate recommendations on managing toxin resistance, we reviewed the evidence on BoNT/A-associated immunogenicity and evaluated Asian physicians' current BoNT/A practices, knowledge, and real-world experiences, as provided by survey outcomes conducted with 128 Asian experts (regular botulinum toxin injectors).

Results:

Most doctors believe STF occurs, some patients exhibit partial symptoms, and impurities (eg, complexing proteins) in BoNT/A preparations risk STF. Bioassays that distinguish non-nAbs from nAbs that hinder toxin function remain unavailable to most doctors, though most would perform testing if given the option. Doctors in the Asia-Pacific region have differing strategies for managing STF, depending on the availability of alternatives or tests. They recommended switching to a highly-purified formulation free of complexing proteins and other impurities to lower the risk of immunogenicity, or offering treatment holidays of 2 -2.5 years. They suggested restarting treatment with the same highly purified formulation, especially for repeated treatments, large-dose injections, and younger patients who will accumulate higher lifetime doses, so as to minimize immunogenic risks and preserve long-term treatment outcomes. Importantly, doctors should always initiate patients on pure formulations rather than switching to these only after resistance develops.

Conclusion:

Choosing highly purified BoNT/A products at treatment initiation enhances long-term efficacy and patient satisfaction while minimizing the risk of immune activation and nAb formation.

IncobotulinumtoxinA for Post-stroke Upper Limb Spasticity in Neutralizing Antibody-positive Patients after Botulinum Toxin Therapy: A Report of Two Cases

Background:

Botulinum toxin type A is an effective treatment widely used to address post-stroke spasticity. Long-term repeated treatment with botulinum toxin type A may result in reduced efficacy due to the induction of neutralizing antibodies. Based on data from a phase 3 study of incobotulinumtoxinA for post-stroke upper limb spasticity, we describe the therapeutic response to botulinum toxin type A treatment in two neutralizing antibody-positive patients previously treated with other preparations of botulinum toxin type A.

Case:

Two patients (a 65-year-old woman and a 36-year-old woman) with post-stroke upper limb spasticity were previously treated with onabotulinumtoxinA, and neutralizing antibodies were detected in their sera at baseline using the mouse hemidiaphragm assay. After onabotulinumtoxinA had been discontinued for at least 16 weeks, incobotulinumtoxinA (400 U) was administered in three or four injection cycles. Good therapeutic responses, manifested by a reduction of 1–2 points on the modified Ashworth scale, were noted after each injection. The patients’ sera remained positive for neutralizing antibodies throughout the incobotulinumtoxinA treatment period.

Discussion:

These patients, who were previously treated with onabotulinumtoxinA and were neutralizing antibody positive throughout the clinical study period, showed stable therapeutic responses following incobotulinumtoxinA treatment. IncobotulinumtoxinA could be initiated for patients with neutralizing antibodies induced by onabotulinumtoxinA.

Efficacy and safety of two incobotulinumtoxinA injection intervals in cervical dystonia patients with inadequate benefit from standard injection intervals of botulinum toxin: Phase 4, open-label, randomized, noninferiority study

•

Botulinum toxin treatment benefit for CD can wane before typical reinjection cycle.

•

Shorter injection cycles of incobotulinumtoxinA are effective for treating CD.

•

Shorter injection intervals have no unexpected AEs or loss of treatment effect.

Introduction

Some patients with cervical dystonia (CD) receiving long-term botulinum neurotoxin (BoNT) therapy report early waning of treatment benefit before the typical 12-week reinjection interval.

Methods

This phase 4, open-label, randomized, noninferiority study (CD Flex; NCT01486264) compared 2 incobotulinumtoxinA injection schedules (Short Flex: 8 ± 2 weeks; Long Flex: 14 ± 2 weeks) in CD patients. Previous BoNT-responsive subjects who reported acceptable clinical benefit lasting < 10 weeks were recruited. Efficacy and safety were evaluated after 8 injection cycles. The primary endpoint was change in Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) severity subscale 4 weeks after the eighth injection. Secondary endpoints included TWSTRS total and subscale scores. Immunogenicity was assessed in a subset of patients.

Results

Two hundred eighty-two CD patients were randomized and treated (Short Flex, N = 142; Long Flex, N = 140), and 207 completed the study. Significant improvements in TWSTRS severity from study baseline to 4 weeks after cycle 8 were observed in both the Short Flex (4.1 points; P < 0.0001) and Long Flex (2.4 points; P = 0.002) groups; Short Flex was noninferior to Long Flex (LS mean difference = 1.4 points; 95% CI = [−2.9, 0.1] < Δ = 2.0). Key secondary endpoints favored Short Flex intervals. Adverse events (AEs) were comparable between groups. There was no secondary loss of treatment effect.

Conclusion

Injection cycles < 10 weeks for incobotulinumtoxinA are effective (and noninferior to longer intervals) for treating CD patients with early waning of clinical benefit. Shorter injection intervals did not increase AEs or lead to loss of treatment effect.