Immunological characterization of the subunits of type A botulinum neurotoxin and different components of its associated proteins

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.

"Pseudo"-Secondary Treatment Failure Explained via Disease Progression and Effective Botulinum Toxin Therapy: A Pilot Simulation Study

BACKGROUND

The objective of this study was to provide evidence from a simple simulation. In patients with focal dystonia, an initial good response to botulinum neurotoxin (BoNT) injections followed by a secondary worsening does not necessarily arise from an antibody-induced secondary treatment failure (NAB-STF), but may stem from a "pseudo"-secondary treatment failure (PSEUDO-STF).

METHODS

The simulation of the outcome after BoNT long-term treatment was performed in four steps: 1. The effect of the first single BoNT injection (SI curve) was displayed as a 12-point graph, corresponding to the mean improvement from weeks 1 to 12. 2. The remaining severity of the dystonia during the nth injection cycle was calculated by subtracting the SI curve (weighted by the outcome after n - 1 cycles) from the outcome after week 12 of the (n - 1)th cycle. 3. A graph was chosen (the PRO curve), which represents the progression of the severity of the underlying disease during BoNT therapy. 4. The interaction between the outcome during the nth BoNT cycle and the PRO curve was determined.

RESULTS

When the long-term outcome after n cycles of BoNT injections (applied every 3 months) was simulated as an interactive process, subtracting the effect of the first cycle (weighted by the outcome after n - 1 cycles) and adding the progression of the disease, an initial good improvement followed by secondary worsening results. This long-term outcome depends on the steepness of the progression and the duration of action of the first injection cycle. We termed this response behavior a "pseudo"-secondary treatment failure, as it can be compensated via a dose increase.

CONCLUSION

A secondary worsening following an initial good response in BoNT therapy of focal dystonia might not necessarily indicate neutralizing antibody induction but could stem from a "PSEUDO"-STF (a combination of good response behavior and progression of the underlying disease). Thus, an adequate dose adaptation must be conducted before diagnosing a secondary treatment failure in the strict sense.

Microtoxin for Improving Pore Size, Skin Laxity, Sebum Control, and Scars: A Roundtable on Integrating Intradermal Botulinum Toxin Type A Microdoses Into Clinical Practice

BACKGROUND

In aesthetic clinical practice, botulinum toxin type A (BoNT-A) is best known for its use as a neuromodulator for the treatment of dynamic facial lines; however, when injected intradermally as microdroplets, BoNT-A can improve skin quality and overall skin appearance.

OBJECTIVES

To discuss key aspects of microtoxin use in clinical practice and provide expert guidance on utilization.

METHODS

As part of a continuing medical education lecture series and roundtable, the authors discussed key aspects of microtoxin patient selection, injection technique, and safety.

RESULTS

The experiences of expert faculty are shared here. Clinical experience is consistent with reported data. Microtoxin can be used to reduce pore size, sebum production, rosacea, acne, and fine lines, and to improve jawline and neck definition. Intradermal injection can also be employed for the improvement of transverse neck lines as well as for the safe prevention and management of scars and keloids.

CONCLUSIONS

Expanding the use of BoNT-A, a predictable, minimally invasive, and affordable treatment to address commonly encountered complaints is appealing. The authors have found that making patients aware of microtoxin as a treatment option results in an increased interest in and utilization of BoNT-A, and high satisfaction among appropriately selected patients.

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.

No Secondary Treatment Failure during Incobotulinumtoxin-A Long-Term Treatment Demonstrated by the Drawing of Disease Severity

The aim of this study was to detect clinical hints regarding the development of secondary treatment failure (STF) in patients with focal dystonia who were exclusively treated with incobotulinumtoxin/A (incoBoNT/A). In total, 33 outpatients (26 with idiopathic cervical dystonia, 4 with Meige syndrome and 3 with other cranial dystonia) who were treated with repeated injections of incoBoNT/A for a mean period of 6.4 years without interruptions were recruited to draw the course of their disease severity (CoD) from the onset of symptoms to the onset of BoNT therapy (CoDB graph) and from the onset of BoNT therapy to recruitment (CoDA graph). At the time of recruitment, the patients assessed the change in severity as a percentage of the severity at the onset of BoNT therapy. Blood samples were taken to test the presence of neutralizing antibodies (NABs) using the mouse hemidiaphragm assay (MHDA). Patients reported an improvement of about 70% with respect to the mean. None of the patients tested positive for MHDA. Three different types of CoDB and three different types of CoDA graphs could be distinguished. The patients with different CoDB graphs reported different long-term outcomes, but there was no significant difference in long-term outcomes between patients with different CoDA graphs. None of the patients produced a CoDA graph with an initial improvement and a secondary worsening as a hint for the development of STF. A primary non-response was not observed in any of the patients. During long-term treatment with BoNT/A, NABs and/or STF may develop. However, in the present study on patients with incoBoNT/A long-term monotherapy, no hints for the development of NABs or STF could be detected, underlining the low antigenicity of incoBoNT/A.

Improving the Efficacy of Botulinum Toxin for Cervical Dystonia: A Scoping Review

Cervical dstonia (CD) is a chronic disorder with a significant detrimental impact on quality of life, requiring long-term treatment. Intramuscular injections of botulinum neurotoxin (BoNT) every 12 to 16 weeks have become the first-line option for CD. Despite the remarkable efficacy of BoNT as a treatment for CD, a significantly high proportion of patients report poor outcomes and discontinue the treatment. The reasons that drive sub-optimal response or treatment failure in a proportion of patients include but are not limited to inappropriate muscle targets and/or BoNT dosing, improper method of injections, subjective feeling of inefficacy, and the formation of neutralizing antibodies against the neurotoxin. The current review aims to complement published research focusing on the identification of the factors that might explain the failure of BoNT treatment in CD, highlighting possible solutions to improve its outcomes. Thus, the use of the new phenomenological classification of cervical dystonia known as COL-CAP might improve the identification of the muscle targets, but more sensitive information might come from the use of kinematic or scintigraphic techniques and the use of electromyographic or ultrasound guidance might ensure the accuracy of the injections. Suggestions are made for the development of a patient-centered model for the management of cervical dystonia and to emphasize that unmet needs in the field are to increase awareness about the non-motor spectrum of CD, which might influence the perception of the efficacy from BoNT injections, and the development of dedicated rehabilitation programs for CD that might enhance its effectiveness.

Immunogenicity of botulinum toxin

Botulinum toxin treatment is the most common non-surgical cosmetic treatment. Although there are many available treatments using botulinum toxin, their effects are temporary and repeated injections are required. These frequent injections can trigger an immunological response. In addition, botulinum toxin acts as an antigen in the body; thus, its effect disappears progressively due to this immunological reaction, which may cause treatment failure. Active botulinum toxin consists of a core neurotoxin and complexing proteins, the exact effects of which remain unclear. However, the complexing proteins are closely related to the immune response and the formation of neutralizing antibodies. Since neutralizing antibodies can lead to treatment failure, their formation should be prevented. Furthermore, various methods of detecting neutralizing antibodies have been used to predict treatment failure.

Immunogenicity of Botulinum Toxin Formulations: Potential Therapeutic Implications

Botulinum neurotoxins (BoNTs) are proteins produced by bacteria of the Clostridium family. Upon oral ingestion, BoNT causes the neuroparalytic syndrome botulism. There are seven serotypes of BoNT (serotypes A-G); BoNT-A and BoNT-B are the botulinum toxin serotypes utilized for therapeutic applications. Treatment with BoNT injections is used to manage chronic medical conditions across multiple indications. As with other biologic drugs, immunogenicity after long-term treatment with BoNT formulations may occur, and repeated use can elicit antibody formation leading to clinical nonresponsiveness. Thus, approaching BoNT treatment of chronic conditions with therapeutic formulations that minimize stimulating the host immune response while balancing patient responsiveness to therapy is ideal. Immunogenicity is a clinical limitation in many settings that use biologic drugs for treatment, and clinically relevant immunogenicity reduction has been achieved through engineering smaller protein constructs and reducing unnecessary formulation components. A similar approach has influenced the evolution of BoNT formulations. Three BoNT-A products and one BoNT-B product have been approved by the Food and Drug Administration (FDA) for therapeutic use: onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB; a fourth BoNT-A product, daxibotulinumtoxinA, is currently under regulatory review. Additionally, prabotulinumtoxinA is a BoNT-A product that has been approved for aesthetic indications but not therapeutic use. Here, we discuss the preclinical and clinical immunogenicity data that exist within the scientific literature and provide a perspective for considering immunogenicity as a key factor in choice of BoNT formulation.

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.

Clinical Improvement After Treatment With IncobotulinumtoxinA (XEOMIN®) in Patients With Cervical Dystonia Resistant to Botulinum Toxin Preparations Containing Complexing Proteins

This study investigated the clinical long-term effect of incobotulinumtoxinA (incoBoNT/A) in 33 cervical dystonia (CD) patients who had developed partial secondary therapy failure (PSTF) under previous long-term botulinum toxin (BoNT) treatment. Patients were treated four times every 12 weeks with incoBoNT/A injections. Physicians assessed treatment efficacy using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) at the baseline visit, week 12 and 48. Patients rated quality of life of CD with the Craniocervical Dystonia Questionnaire (CDQ-24). Titres of neutralizing antibodies(NAB) were determined at start of the study and after 48 weeks. All patients had experienced significant and progressive worsening of symptoms in the last 6 months of previous BoNT treatment. Repeated incoBoNT/A injections resulted in a significant reduction in mean TWSTRS at week 12 and 48. Patients' rating of quality of life was highly correlated with TWSTRS but did not change significantly over 48 weeks. During the 48 weeks -period of incoBoNT/A treatment NAB titres decreased in 32.2%, did not change in 45.2%, and only increased in 22.6% of the patients. Thus, repeated treatment with the low dose of 200 MU incoBoNT/A over 48 weeks provided a beneficial clinical long-term effect in PSTF and did not booster titres of NAB.

Neurotoxin Impurities: A Review of Threats to Efficacy

Recently launched esthetic botulinum toxin serotype A (BoNT/A) products include Nabota/Jeuveau, Meditoxin/Neuronox, and Botulax, which contain nontoxic accessory proteins and excipients. Clinical evidence supporting these formulations, including their purity and potential immunogenicity or their link to treatment failures, is limited. Any nonhuman protein, including nontoxin accessory proteins, can initiate immune reactions, especially if administered repeatedly, yet the issue of BoNT/A-induced immunogenicity is widely contested. However, there have been multiple reports of treatment failures and observations of BoNT/A-induced neutralizing antibodies. Compared with the purified formulation in Xeomin, these recently launched toxins contain higher total neurotoxin quantities, much of which is inactive and exposes patients to potentially immunogenic nontoxin proteins or inactive neurotoxins that increase their risk of developing treatment failure. Well-established products [especially abobotulinumtoxinA (Dysport), onabotulinumtoxinA (Botox) and Xeomin] are accompanied by comprehensive and long-ranging clinical evidence on safety and efficacy in esthetic facial indications, which still remains undisclosed for many of the recently introduced toxins. Clinicians need this information as patients will require repeated BoNT treatments and may be unnecessarily but cumulatively exposed to potential immunogens. To underscore the need for caution and further evidence, we review some of the issues surrounding BoNT/A-induced immunogenicity and antibody-induced treatment failures and argue that using highly purified toxins that do not negatively impact patient outcomes is a prudent clinical decision.

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.

The role of human serum albumin and neurotoxin associated proteins in the formulation of BoNT/A products

Botulinum neurotoxin (BoNT) is synthesized as a progenitor toxin complex (PTC) by Clostridium botulinum. This PTC comprises, in addition to the neurotoxin itself, neurotoxin associated proteins (NAPs) which are composed of three hemagglutinins and one non-toxic, non-hemagglutinin protein. After oral ingestion, these NAPs protect the neurotoxin from the low pH and proteases in the gastrointestinal tract and play a role in the entry via the intestinal barrier. Two of the three therapeutically used botulinum neurotoxin serotype A (BoNT/A) products (onabotulinumtoxinA and abobotulinumtoxinA) contain different amounts of NAPs, while incobotulinumtoxinA, lacks these proteins. In addition, human serum albumin (HSA) that is supposed to stabilize BoNT/A is added at different concentrations. Up to now, the function of the NAPs and HSA after parenteral therapeutic application is not completely understood. To investigate the influence of NAPs and HSA on potency of BoNT/A, we used the ex vivo mouse phrenic nerve hemidiaphragm assay. Increasing doses of HSA resulted dose-dependently in a more pronounced effect of BoNT/A. Though, a plateau was reached with concentrations of 0.8 mg/ml HSA and higher, the accessory addition of NAPs in a relevant amount (4 ng/ml) did not further enhance the effect of BoNT/A. In conclusion, in our ex vivo assay an adequate concentration of HSA prevented BoNT/A from loss of effect and supplementary NAPs did not alter this effect. A confirmation of these data in an in vivo assay is still lacking. However, it might be supposed that even in clinically applied BoNT/A products an increase of HSA accompanied by the avoidance of NAPs could potentially reduce the injected dose and, thus, the risk of unwanted side effects, the treatment costs as well as the risk of a secondary therapy failure due to BoNT/A neutralizing antibodies.

IncobotulinumtoxinA Efficacy and Safety in Adults with Upper-Limb Spasticity Following Stroke: Results from the Open-Label Extension Period of a Phase 3 Study

Introduction

The objective of the study was to investigate the efficacy and safety of repeated incobotulinumtoxinA injections for the treatment of upper-limb post-stroke spasticity in adults.

Methods

Adults 18–80 years of age with post-stroke upper-limb spasticity who completed the 12-week randomized, double-blind, placebo-controlled main period (MP) of a phase 3 trial (NCT01392300) were eligible to enrol in the 36-week open-label extension period (OLEX). The OLEX included three treatment cycles at fixed 12-week injection intervals; subjects were injected with 400 U incobotulinumtoxinA into the affected upper limb. Efficacy assessments included evaluation of muscle tone using the Ashworth Scale (AS) and the Global Impression of Change Scale (GICS) assessed by the investigator, subject, and caregiver. The incidence of adverse events (AEs) was monitored throughout the OLEX.

Results

A total of 296 of 299 subjects (99.0%) who completed the MP received incobotulinumtoxinA in the OLEX, and 248 subjects completed the 36-week OLEX. The proportion of subjects with at least a 1-point improvement in AS score from each incobotulinumtoxinA treatment to the respective 4-week post-injection visit ranged by cycle from 52.3% to 59.2% for wrist flexors, 49.1% to 52.3% for elbow flexors, 59.8% to 64.5% for finger flexors, 35.5% to 41.2% for thumb flexors, and 37.4% to 39.9% for forearm pronators (P < 0.0001 for all). Over 90% of subjects were assessed by the investigator to be at least minimally improved (4 weeks post-injection) on the GICS during each injection cycle; 61.0% in the 1st cycle, 58.2% in the 2nd cycle, and 57.4% in the 3rd cycle were considered much improved or very much improved on the GICS. Three percent of subjects (9/296) reported treatment-related AEs; the most frequently reported were pain in the extremity (n = 2, 0.7%) and constipation (n = 2, 0.7%). Serious AEs were reported by 22 subjects (7.4%); however, none were considered treatment-related.

Conclusions

Repeated injections of incobotulinumtoxinA for the treatment of post-stroke upper-limb spasticity led to significant improvements in muscle tone and investigator’s global impression of change. Treatment was well tolerated, with no serious treatment-related AEs.

Funding

Merz Pharmaceuticals GmbH.

Natural Compounds and Their Analogues as Potent Antidotes against the Most Poisonous Bacterial Toxin

Botulinum neurotoxins (BoNTs), the most poisonous proteins known to humankind, are a family of seven (serotype A to G) immunologically distinct proteins synthesized primarily by different strains of the anaerobic bacterium Clostridium botulinum Being the causative agents of botulism, the toxins block neurotransmitter release by specifically cleaving one of the three soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, thereby inducing flaccid paralysis. The development of countermeasures and therapeutics against BoNTs is a high-priority research area for public health because of their extreme toxicity and potential for use as biowarfare agents. Extensive research has focused on designing antagonists that block the catalytic activity of BoNTs. In this study, we screened 300 small natural compounds and their analogues extracted from Indian plants for their activity against BoNT serotype A (BoNT/A) as well as its light chain (LCA) using biochemical and cellular assays. One natural compound, a nitrophenyl psoralen (NPP), was identified to be a specific inhibitor of LCA with an in vitro 50% inhibitory concentration (IC₅₀) value of 4.74 ± 0.03 µM. NPP was able to rescue endogenous synaptosome-associated protein 25 (SNAP-25) from cleavage by BoNT/A in human neuroblastoma cells with an IC₅₀ of 12.2 ± 1.7 µM, as well as to prolong the time to the blocking of neutrally elicited twitch tensions in isolated mouse phrenic nerve-hemidiaphragm preparations.IMPORTANCE The long-lasting endopeptidase activity of BoNT is a critical biological activity inside the nerve cell, as it prompts proteolysis of the SNARE proteins, involved in the exocytosis of the neurotransmitter acetylcholine. Thus, the BoNT endopeptidase activity is an appropriate clinical target for designing new small-molecule antidotes against BoNT with the potential to reverse the paralysis syndrome of botulism. In principle, small-molecule inhibitors (SMIs) can gain entry into BoNT-intoxicated cells if they have a suitable octanol-water partition coefficient (log P) value and other favorable characteristics (P. Leeson, Nature 481:455-456, 2012, https://doi.org/10.1038/481455a). Several efforts have been made in the past to develop SMIs, but inhibitors effective under in vitro conditions have not in general been effective in vivo or in cellular models (L. M. Eubanks, M. S. Hixon, W. Jin, S. Hong, et al., Proc Natl Acad Sci U S A 104:2602-2607, 2007, https://doi.org/10.1073/pnas.0611213104). The difference between the in vitro and cellular efficacy presumably results from difficulties experienced by the compounds in crossing the cell membrane, in conjunction with poor bioavailability and high cytotoxicity. The screened nitrophenyl psoralen (NPP) effectively antagonized BoNT/A in both in vitro and ex vivo assays. Importantly, NPP inhibited the BoNT/A light chain but not other general zinc endopeptidases, such as thermolysin, suggesting high selectivity for its target. Small-molecule (nonpeptidic) inhibitors have better oral bioavailability, better stability, and better tissue and cell permeation than antitoxins or peptide inhibitors.

Comparison of neurotoxic potency between a novel chinbotulinumtoxinA with onabotulinumtoxinA, incobotulinumtoxinA and lanbotulinumtoxinA in rats

Four botulinumtoxin type A (BoNT/A) products, onabotulinumtoxinA (A/Ona), incobotulinumtoxinA (A/Inco), lanbotulinumtoxinA (A/Lan) and chinbotulinumtoxinA (A/Chin), are applied in the present study, among which A/Chin is newly produced. We aimed to compare the neurotoxic potency of these toxins by the gauge of muscle strength reduction. Furthermore, potential molecular and cellular mechanisms were also explored. According to our data, muscle strengths in the four toxin groups were all significantly decreased after injection for 1 week. A/Chin achieved the most obvious reduction in muscle strength as compared to the other three products at the dose of 0.5 U. However, there was no difference between the four toxins when increased to 2 U. As the toxins wore off, muscle strength recovered to basal level 12 weeks postinjection. We further measured the expression levels of key factors involved in neuromuscular junction stabilization and muscle genesis. Our results showed that nicotinic acetylcholine receptor, myogenic regulatory factors and muscle-specific receptor tyrosine kinase were all significantly upregulated upon BoNT/A treatment. Consistent with the result of muscle strength, A/Chin had the most obvious induction of gene expression. Moreover, we also found local inflammation response following BoNT/A injection. Owing to lack of complexing proteins, both A/Inco and A/Chin stimulated relatively lighter inflammation compared to that of A/Ona and A/Lan groups. In conclusion, our study provided evidence for the efficacy of the novel A/Chin and its similar functional mode to that of A/Ona, A/Inco and A/Lan. In addition, A/Chin has superiority in inducing muscle paralysis and inflammation stimulation, which may indicate faster onset and longer duration of this novel A/Chin.

Characterization of Hemagglutinin Negative Botulinum Progenitor Toxins

Botulism is a disease involving intoxication with botulinum neurotoxins (BoNTs), toxic proteins produced by Clostridium botulinum and other clostridia. The 150 kDa neurotoxin is produced in conjunction with other proteins to form the botulinum progenitor toxin complex (PTC), alternating in size from 300 kDa to 500 kDa. These progenitor complexes can be classified into hemagglutinin positive or hemagglutinin negative, depending on the ability of some of the neurotoxin-associated proteins (NAPs) to cause hemagglutination. The hemagglutinin positive progenitor toxin complex consists of BoNT, nontoxic non-hemagglutinin (NTNH), and three hemagglutinin proteins; HA-70, HA-33, and HA-17. Hemagglutinin negative progenitor toxin complexes contain BoNT and NTNH as the minimally functional PTC (M-PTC), but not the three hemagglutinin proteins. Interestingly, the genome of hemagglutinin negative progenitor toxin complexes comprises open reading frames (orfs) which encode for three proteins, but the existence of these proteins has not yet been extensively demonstrated. In this work, we demonstrate that these three proteins exist and form part of the PTC for hemagglutinin negative complexes. Several hemagglutinin negative strains producing BoNT/A, /E, and /F were found to contain the three open reading frame proteins. Additionally, several BoNT/A-containing bivalent strains were examined, and NAPs from both genes, including the open reading frame proteins, were associated with BoNT/A. The open reading frame encoded proteins are more easily removed from the botulinum complex than the hemagglutinin proteins, but are present in several BoNT/A and /F toxin preparations. These are not easily removed from the BoNT/E complex, however, and are present even in commercially-available purified BoNT/E complex.

[Cutaneous granulomatous reactions at botulinum neurotoxin A injection sites: First manifestation of systemic sarcoidosis]

CASE REPORT

We report a case of granulomatous skin reaction after injection of an unknown botulinum neurotoxin (BoNT) A preparation. Four years after occurrence of skin lesions, systemic sarcoidosis became manifest.

CONCLUSION

In addition to injection trauma, the BoNT A preparation may have acted as an immunogenic stimulus leading to cutaneous manifestation of sarcoidosis.

Conversion Ratio between Botox®, Dysport®, and Xeomin® in Clinical Practice

Botulinum neurotoxin has revolutionized the treatment of spasticity and is now administered worldwide. There are currently three leading botulinum neurotoxin type A products available in the Western Hemisphere: onabotulinum toxin-A (ONA) Botox(®), abobotulinum toxin-A (ABO), Dysport(®), and incobotulinum toxin A (INCO, Xeomin(®)). Although the efficacies are similar, there is an intense debate regarding the comparability of various preparations. Here we will address the clinical issues of potency and conversion ratios, as well as safety issues such as toxin spread and immunogenicity, to provide guidance for BoNT-A use in clinical practice. INCO was shown to be as effective as ONA with a comparable adverse event profile when a clinical conversion ratio of 1:1 was used. The available clinical and preclinical data suggest that a conversion ratio ABO:ONA of 3:1-or even lower-could be appropriate for treating spasticity, cervical dystonia, and blepharospasm or hemifacial spasm. A higher conversion ratio may lead to an overdosing of ABO. While uncommon, distant spread may occur; however, several factors other than the pharmaceutical preparation are thought to affect spread. Finally, whereas the three products have similar efficacy when properly dosed, ABO has a better cost-efficacy profile.

Pharmaceutical, biological, and clinical properties of botulinum neurotoxin type A products

Botulinum neurotoxin injections are a valuable treatment modality for many therapeutic indications and have revolutionized the field of aesthetic medicine so that they are the leading cosmetic procedure performed worldwide. Studies show that onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA are comparable in terms of clinical efficacy. Differences between the products relate to the botulinum neurotoxin complexes, specific biological potency, and their immunogenicity. Protein complex size and molecular weight have no effect on biological activity, stability, distribution, or side effect profile. Complexing proteins and inactive toxin (toxoid) content increase the risk of neutralizing antibody formation, which can cause secondary treatment failure, particularly in chronic disorders that require frequent injections and long-term treatment. These attributes could lead to differences in therapeutic outcomes, and, given the widespread aesthetic use of these three neurotoxin products, physicians should be aware of how they differ to ensure their safe and effective use.

Botulinum toxin type A products are not interchangeable: a review of the evidence

Botulinum toxin type A (BoNTA) products are injectable biologic medications derived from Clostridium botulinum bacteria. Several different BoNTA products are marketed in various countries, and they are not interchangeable. Differences between products include manufacturing processes, formulations, and the assay methods used to determine units of biological activity. These differences result in a specific set of interactions between each BoNTA product and the tissue injected. Consequently, the products show differences in their in vivo profiles, including preclinical dose response curves and clinical dosing, efficacy, duration, and safety/adverse events. Most, but not all, published studies document these differences, suggesting that individual BoNTA products act differently depending on experimental and clinical conditions, and these differences may not always be predictable. Differentiation through regulatory approvals provides a measure of confidence in safety and efficacy at the specified doses for each approved indication. Moreover, the products differ in the amount of study to which they have been subjected, as evidenced by the number of publications in the peer-reviewed literature and the quantity and quality of clinical studies. Given that BoNTAs are potent biological products that meet important clinical needs, it is critical to recognize that their dosing and product performance are not interchangeable and each product should be used according to manufacturer guidelines.

Type A botulinum neurotoxin complex proteins differentially modulate host response of neuronal cells

Type A Botulinum neurotoxin (BoNT/A), the most potent poison known to mankind, is produced by Clostridium botulinum type A as a complex with neurotoxin-associated proteins (NAPs). Currently BoNT/A in purified and complex forms are both available in therapeutic and cosmetic applications to treat neuromuscular disorders. Whereas Xeomin(®) (incobotulinumtoxin A, Merz Pharmaceuticals, Germany) is free from complexing proteins, Botox(®) (onabotulinumtoxin A, Allergan, USA) contains NAPs, which by themselves have no known role in the intracellular biochemical process involved in the blockade of neurotransmitter release. Since the fate and possible interactions of NAPs with patient tissues after intramuscular injection are not known, it was the aim of this study to evaluate the binding of BoNT/A and/or the respective NAPs to cells derived from neuronal and non-neuronal human tissues, and to further explore neuronal cell responses to different components of BoNT/A. BoNT/A alone, the complete BoNT/A complex, and the NAPs alone, all bind to neuronal SH-SY5Y cells. The BoNT/A complex and NAPs additionally bind to RMS13 skeletal muscle cells, TIB-152 lymphoblasts, Detroit 551 fibroblasts besides the SH-SY5Y cells. However, no binding to these non-neuronal cells was observed with pure BoNT/A. Although BoNT/A, both in its purified and complex forms, bind to SH-SY5Y, the intracellular responses of the SH-SY5Y cells to these BoNT/A components are not clearly understood. Examination of inflammatory cytokine released from SH-SY5Y cells revealed that BoNT/A did not increase the release of inflammatory cytokines, whereas exposure to NAPs significantly increased release of IL-6, and MCP-1, and exposure to BoNT/A complex significantly increased release of IL-6, MCP-1, IL-8, TNF-α, and RANTES vs. control, suggesting that different components of BoNT/A complex induce significantly differential host response in human neuronal cells. Results suggest that host response to different compositions of BoNT/A based therapeutics may play important role in local and systemic symptoms in patients.

Expression and purification of neurotoxin-associated protein HA-33/A from Clostridium botulinum and evaluation of its antigenicity

BACKGROUND

Botulinum neurotoxin (BoNT) complexes consist of neurotoxin and neurotoxin-associated proteins. Hemagglutinin-33 (HA-33) is a member of BoNT type A (BoNT/A) complex. Considering the protective role of HA-33 in preservation of BoNT/A in gastrointestinal harsh conditions and also its adjuvant role, recombinant production of this protein is favorable. Thus in this study, HA-33 was expressed and purified, and subsequently its antigenicity in mice was studied.

METHODS

Initially, ha-33 gene sequence of Clostridium botulinum serotype A was adopted from GenBank. The gene sequence was optimized and synthesized in pET28a (+) vector. E. coli BL21 (DE3) strain was transformed by the recombinant vector and the expression of HA-33 was optimized at 37°C and 5 h induction time.

RESULTS

The recombinant protein was purified by nickel nitrilotriacetic acid agarose affinity chromatography and confirmed by immunoblotting. Enzyme Linked Immunoassay showed a high titer antibody production in mice.

CONCLUSION

The results indicated a highly expressed and purified recombinant protein, which is able to evoke high antibody titers in mice.

Molecular composition and extinction coefficient of native botulinum neurotoxin complex produced by Clostridium botulinum hall A strain

Seven distinct strains of Clostridium botulinum (type A to G) each produce a stable complex of botulinum neurotoxin (BoNT) along with neurotoxin-associated proteins (NAPs). Type A botulinum neurotoxin (BoNT/A) is produced with a group of NAPs and is commercially available for the treatment of numerous neuromuscular disorders and cosmetic purposes. Previous studies have indicated that BoNT/A complex composition is specific to the strain, the method of growth and the method of purification; consequently, any variation in composition of NAPs could have significant implications to the effectiveness of BoNT based therapeutics. In this study, a standard analytical technique using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and densitometry analysis was developed to accurately analyze BoNT/A complex from C. botulinum type A Hall strain. Using 3 batches of BoNT/A complex the molar ratio was determined as neurotoxin binding protein (NBP, 124 kDa), heavy chain (HC, 90 kDa), light chain (LC, 53 kDa), NAP-53 (50 kDa), NAP-33 (36 kDa), NAP-22 (24 kDa), NAP-17 (17 kDa) 1:1:1:2:3:2:2. With Bradford, Lowry, bicinchoninic acid (BCA) and spectroscopic protein estimation methods, the extinction coefficient of BoNT/A complex was determined as 1.54 ± 0.26 (mg/mL)(-1)cm(-1). These findings of a reproducible BoNT/A complex composition will aid in understanding the molecular structure and function of BoNT/A and NAPs.

Comparative immunochemical characteristics of botulinum neurotoxin type A and its associated proteins

Clostridium botulinum strains secrete their neurotoxins (BoNT) along with a group of neurotoxin-associated proteins (NAPs) that enhance the oral toxicity and provide protection to the neurotoxin against acidity, temperature and proteases in the G.I. tract. A major component of NAPs is Hn-33, a 33 kDa protein, which is also protease resistant and strongly protects BoNT. The complex form of BoNT/A is used as a commercial therapeutic formulation against many neuromuscular disorders and for cosmetic purposes. Immune response against this formulation could hinder its long-term use; therefore, it is important to characterize the immunological properties of the associated proteins. This study aims to understand the immunological reactivity of BoNT/A complex, BoNT, NAPs, and Hn-33 through a series of competitive enzyme-linked immunosorbent assays (ELISA). The results indicated that BoNT/A complex competed 6 times more with complex antibodies compared to the neurotoxin confirming that the higher immunogenicity of BoNT/A complex was indeed a result of the associated proteins with the neurotoxin complex. While the nearly identical immuno-reactivity of BoNT/A complex and Hn-33 with Hn-33 antibodies indicated that the reactivity was due to the higher immunogenicity not the abundance of Hn-33 in the complex. Both the ELISA and immuno-blot results implied that Hn-33 is primarily responsible for eliciting the antibody response in BoNT/A complex.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Clinical relevance of botulinum toxin immunogenicity

Botulinum toxin type A is a 150 kD protein produced by Clostridium botulinum, which exists in a complex with up to six additional proteins. The ability of botulinum toxin to inhibit acetylcholine release at the neuromuscular junction has been exploited for use in medical conditions characterized by muscle hyperactivity. As such, botulinum toxin is widely recommended by international treatment guidelines for movement disorders and it has a plethora of other clinical and cosmetic indications. The chronic nature of these conditions requires repeated injections of botulinum toxin, usually every few months. Multiple injections can lead to secondary treatment failure in some patients that may be associated with the production of neutralizing antibodies directed specifically against the neurotoxin. However, the presence of such antibodies does not always render patients non-responsive. The reported prevalence of immunoresistance varies greatly, depending on factors such as study design and treated indication. This review presents what is currently known about the immunogenicity of botulinum toxin and how this impacts upon patient non-response to treatment. The complexing proteins may act as adjuvants and stimulate the immune response. Their role and that of neutralizing and non-neutralizing antibodies in the response to botulinum toxin is discussed, together with an assessment of current neutralizing antibody measurement techniques. Botulinum toxin preparations with different compositions and excipients have been developed. The major commercially available preparations of botulinum toxin are Botox® (onabotulinumtoxinA; Allergan, Inc., Ireland), Dysport® (abobotulinumtoxinA; Ipsen Ltd, UK), and Xeomin® (incobotulinumtoxinA; botulinum toxin type A [150 kD], free from complexing proteins; NT 201; Merz Pharmaceuticals GmbH, Germany). The new preparations of botulinum toxin aim to minimize the risk of immunoresistance in patients being treated for chronic clinical conditions.

A new treatment for focal dystonias: incobotulinumtoxinA (Xeomin®), a botulinum neurotoxin type A free from complexing proteins

Dystonia is a movement disorder of uncertain pathogenesis that is characterized by involuntary and inappropriate muscle contractions which cause sustained abnormal postures and movements of multiple or single (focal) body regions. The most common focal dystonias are cervical dystonia (CD) and blepharospasm (BSP). The first-line recommended treatment for CD and BSP is injection with botulinum toxin (BoNT), of which two serotypes are available: BoNT type A (BoNT/A) and BoNT type B (BoNT/B). Conventional BoNT formulations include inactive complexing proteins, which may increase the risk for antigenicity, possibly leading to treatment failure. IncobotulinumtoxinA (Xeomin(®); Merz Pharmaceuticals GmbH, Frankfurt, Germany) is a BoNT/A agent that has been recently Food and Drug Administration-approved for the treatment of adults with CD and adults with BSP previously treated with onabotulinumtoxinA (Botox(®); Allergen, Inc, Irvine, CA) - a conventional BoNT/A. IncobotulinumtoxinA is the only BoNT product that is free of complexing proteins. The necessity of complexing proteins for the effectiveness of botulinum toxin treatment has been challenged by preclinical and clinical studies with incobotulinumtoxinA. These studies have also suggested that incobotulinumtoxinA is associated with a lower risk for stimulating antibody formation than onabotulinumtoxinA. In phase 3 noninferiority trials, incobotulinumtoxinA demonstrated significant improvements in CD and BSP symptoms in both primary and secondary measures, compared with baseline, and met criteria for noninferiority versus onabotulinumtoxinA. In placebo-controlled trials, incobotulinumtoxinA also significantly improved the symptoms of CD and BSP, with robust outcomes in both primary and secondary measures. The use of incobotulinumtoxinA has been well tolerated in all trials, with an adverse event profile similar to that of onabotulinumtoxinA. Based on these data, incobotulinumtoxinA is a safe and effective BoNT/A for the treatment of CD and BSP, and may pose a lower risk for immunogenicity leading to treatment failure compared with other available BoNT agents. This paper reviews the treatment of focal dystonias with BoNTs, in particular, incobotulinumtoxinA. Controlled trials from the existing incobotulinumtoxinA literature are summarized.

Efficacy and safety of incobotulinumtoxinA (NT 201, Xeomin) in the treatment of blepharospasm-a randomized trial

IncobotulinumtoxinA (NT 201, Xeomin) is a highly purified botulinum neurotoxin type A formulation, free from complexing proteins. A randomized, placebo-controlled, double-blind trial of efficacy and safety compared incobotulinumtoxinA (up to 50 U per eye) to placebo administered in a single treatment session to patients with blepharospasm. All patients had documented satisfactory response to 2 previous treatments with botulinum neurotoxin type A other than incobotulinumtoxinA and had Jankovic Rating Scale severity subscores ≥ 2. Patients (n = 109) were randomized in a 2:1 ratio to incobotulinumtoxinA or placebo and followed up to 20 weeks; 94% completed the study. A significant difference was observed in the primary efficacy variable (change in Jankovic Rating Scale severity subscore rated by an independent rater 6 weeks following treatment), favoring incobotulinumtoxinA by 1.0 point (95% CI [0.5-1.4]; P < .001). Functional impairment, as measured by the Blepharospasm Disability Index, improved by 0.5 points (95% CI [0.2-0.7]; P = .002) compared with placebo. There was a strong correlation between the 2 scale scores. In addition, all secondary outcome measures favored incobotulinumtoxinA. Patients rated the mean therapeutic effect of incobotulinumtoxinA significantly better than placebo (P < .001). Adverse events were reported in 70.3% of incobotulinumtoxinA patients and 58.8% of placebo patients. Eyelid ptosis (18.9% vs 5.9%), dry eye (18.9% vs 11.8%), and dry mouth (14.9% vs 2.9%) occurred most frequently. Tolerability was rated good/very good by 91.9% of incobotulinumtoxinA versus in 85.2% of placebo patients. In conclusion, incobotulinumtoxinA was well tolerated and was associated with statistically significant and clinically relevant reductions in blepharospasm severity and functional impairment.

Efficacy of a potential trivalent vaccine based on Hc fragments of botulinum toxins A, B, and E produced in a cell-free expression system

Botulinum toxins produced by the anaerobic bacterium Clostridium botulinum are the most potent biological toxins in nature. Traditionally, people at risk are immunized with a formaldehyde-inactivated toxin complex. Second generation vaccines are based on the recombinant carboxy-terminal heavy-chain (Hc) fragment of the neurotoxin. However, the materialization of this approach is challenging, mainly due to the high AT content of clostridial genes. Herein, we present an alternative strategy in which the native genes encoding Hc proteins of botulinum toxins A, B, and E were used to express the recombinant Hc fragments in a cell-free expression system. We used the unique property of this open system to introduce different combinations of chaperone systems, protein disulfide isomerase (PDI), and reducing/oxidizing environments directly to the expression reaction. Optimized expression conditions led to increased production of soluble Hc protein, which was successfully scaled up using a continuous exchange (CE) cell-free system. Hc proteins were produced at a concentration of more than 1 mg/ml and purified by one-step Ni(+) affinity chromatography. Mice immunized with three injections containing 5 microg of any of the in vitro-expressed, alum-absorbed, Hc vaccines generated a serum enzyme-linked immunosorbent assay (ELISA) titer of 10(5) against the native toxin complex, which enabled protection against a high-dose toxin challenge (10(3) to 10(6) mouse 50% lethal dose [MsLD(50)]). Finally, immunization with a trivalent HcA, HcB, and HcE vaccine protected mice against the corresponding trivalent 10(5) MsLD(50) toxin challenge. Our results together with the latest developments in scalability of the in vitro protein expression systems offer alternative routes for the preparation of botulinum vaccine.

Xeomin in the treatment of cervical dystonia

BACKGROUND AND PURPOSE

Botulinum toxin type A (BoNT/A) is a highly effective and well-tolerated treatment for focal dystonias. The BoNT/A in Botox and Dysport is part of a high-molecular-weight complex that contains hemagglutinins and other non-toxic proteins, whilst Xeomin is a highly purified BoNT/A free of such complexing proteins. In the largest controlled study of BoNT/A published to date (Neurology 2005; 64: 1949), it was demonstrated that Xeomin is non-inferior to Botox and has 1:1 efficacy in the treatment of cervical dystonia. A possible limitation of continued BoNT/A treatment is antibody development. Based on its physiochemical properties and toxicological evidence, Xeomin is expected to have a reduced incidence of non-responders after long-term treatment compared with other marketed BoNT/A products.

METHODS AND RESULTS

In our ongoing open-label study, 100 patients suffering from cervical dystonia are continuously treated with Xeomin; 50 patients were treated de novo, the remaining patients had been previously treated with Botox, Dysport or NeuroBloc/Myobloc. All patients showed negative results in antibody testing at the beginning of Xeomin treatment. During continuous treatment with Xeomin up to 2 years, patients continued to respond well to Xeomin treatment.

CONCLUSION

The treatment was well tolerated and no patient has developed neutralizing antibodies as measured using the sensitive mouse hemidiaphragma assay within these first 2 years.