Modulation of botulinum toxin-induced changes in neuromuscular function with antibodies directed against recombinant polypeptides or fragments

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.

Botulinum Toxin Type A Immunogenicity across Multiple Indications: An Overview Systematic Review

BACKGROUND

Botulinum toxin type A has been used to treat a wide array of neurologic, medical, and aesthetic indications. Several factors contribute to the formation of neutralizing antibodies, such as shorter intervals of treatment, higher dosage, amounts of antigenic proteins, serotypes, and storage of formulations.

METHOD

This overview followed the Cochrane guideline for overview reviews. The AMSTAR-2 (revised version of A Measurement Tool to Assess Systematic Reviews) tool was used for the critical appraisal of the selected systematic reviews.

RESULTS

Five systematic reviews consisting of 203 studies (17,815 patients) were included, and their AMSTAR-2 scores were low to critically poor. There was high heterogeneity between the studies. Across the clinical indications, neutralizing antibody prevalence was significantly higher in dystonia, spasticity, and urologic conditions, and nil to insignificant in hyperhidrosis and aesthetic indications. The overall rate for the neutralizing antibody formation across three different formulations, abobotulinumtoxinA, incobotulinumtoxinA, and onabotulinumtoxinA, was 1 to 2.1 percent, with no significant difference between them.

RESULTS

Although there is debate on the prevalence rate across the different botulinum toxin type A formulations in individual systematic reviews, the overall frequency of the development of neutralizing antibodies and the immunogenicity of abobotulinumtoxinA, incobotulinumtoxinA, and onabotulinumtoxinA remain low to insignificant.

CONCLUSIONS

Properly designed comparative trials are required to explore the difference in the prevalence of neutralizing antibodies across the commercially available botulinum toxin type A products. Such studies should also examine the relevance of neutralizing antibody titer to clinical responsiveness and nonresponse.

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.

Pharmacological differences and clinical implications of various botulinum toxin preparations: a critical appraisal

Three different type A botulinum neurotoxins (BoNTAs) - onabotulinumtoxinA, abobotulinumtoxinA and incobotulinumtoxinA) - are currently marketed in Europe to treat several conditions. Differences between BoNTA preparations, which depend on their specific biotypes and manufacturing processes, lead to clinically relevant pharmacotherapeutic dissimilarities. All three available products are separately recognized and reviewed in American Academy of Neurology guidelines. The neurotoxin load/100U is likewise different among the different BoNTAs, with the result that the specific potency of the 150kD BoNTA neurotoxin is calculated as 137 units/ng for onabotulinumtoxinA, 154 units/ng for abobotulinumtoxinA, and 227 units/ng for incobotulinumtoxinA. It is important for clinicians to have all three BoNTAs available in order to choose the most suitable preparation for the specific indication in the single patient. Commercially available BoNTAs must be recognized as different from one another, and therefore as non-interchangeable. The essential experience of the clinician is of the utmost importance in choosing the most appropriate treatment.

Comparison of botulinum neurotoxin type A formulations in Asia

Results

All protein-based therapeutics, such as botulinum neurotoxin type A (BoNT/A), are potentially immunogenic and can lead to anaphylaxis, autoimmunity, or diminished or complete absence of therapeutic efficacy, especially if administered repeatedly. Therefore, the protein quantity in BoNT/A products is an important consideration when selecting products for treatment. However, essential formulation data are not always publicly accessible.

Materials and methods

The neurotoxin protein content of products newly introduced in Asia, such as (listed alphabetically) Botulax^®, Meditoxin^®, Nabota^®, and Relatox^®, was measured by sandwich enzyme-linked immunosorbent assay with antisera directed against BoNT/A compared to Xeomin^®.

Results

Compared to Xeomin with no inactive neurotoxin, although Botulax and Nabota contained 844 and 754 pg of neurotoxin protein, respectively, the percentage of inactive neurotoxin was calculated to be 103 and 81, respectively, while the potency per pg of neurotoxin was 0.118 and 0.133 U, respectively. Meditoxin and Relatox had 575 and 578 pg of neurotoxins, respectively, marginally higher than that of Xeomin, while the percentage of inactive neurotoxins was 38 and 33, respectively, and the potency per pg of neurotoxin was 0.174 and 0.173 U, respectively. However, Xeomin, which has 416 pg/vial of purified neurotoxin and 0.240 U of efficacy per pg of neurotoxin, has the lowest neurotoxin protein content and consequently the highest specific potency compared to the four Asian BoNT/A preparations in this study.

Conclusion

Although Botulax and Nabota had more neurotoxin than Xeomin in an equivalent volume, they contained greater amounts of inactive neurotoxin. In addition, although Meditoxin and Relatox had slightly more neurotoxin than Xeomin, both contained greater amounts of inactive neurotoxin.

Monoclonal antibodies from a patient with anti-NMDA receptor encephalitis

Objective

Anti‐NMDA receptor encephalitis (ANRE) is a potentially lethal encephalitis attributed to autoantibodies against the N‐methyl‐D‐aspartate receptor (NMDAR). We sought to clone and characterize monoclonal antibodies (mAbs) from an ANRE patient.

Methods

We used a hybridoma method to clone two IgG mAbs from a female patient with ANRE without teratoma, and characterized their binding activities on NMDAR‐transfected cell lines, cultured primary rat neurons, and mouse hippocampus. We also assessed their effects on voluntary locomotor activity in mice and binding to NMDAR in vivo.

Results

The mAbs are structurally distinct and arose from distinct B‐cell lineages. They recognize different epitopes on the GluN1 amino terminal domain (ATD), yet both require amino acids important for post‐translational modification. Both mAbs bind subsets of GluN1 on cultured rat hippocampal neurons. The 5F5 mAb binds mouse brain hippocampal tissues, and the GluN1 recognized on cultured rat neurons was substantially extra‐synaptic. Antibody binding to primary hippocampal neurons induced receptor internalization. The NMDAR inhibitor MK‐801 inhibited internalization without preventing mAb binding; AP5 inhibited both mAb binding and internalization. Exposure of mice to the mAbs following permeabilization of the blood brain barrier increased voluntary wheel running activity, similar to low doses of the NMDAR inhibitor, MK‐801.

Interpretation

These mAbs recapitulate features demonstrated in previous studies of ANRE patient CSF, and exert effects on NMDAR in vitro and in vivo consistent with modulation of NMDAR activity.

Botulinum toxin therapy for cervical dystonia: the science of dosing

The first-line treatment for cervical dystonia (CD) is botulinum toxin type A (BoNT-A), which has been established as a highly effective and well-tolerated therapy. However, this treatment is also complex and challenging to apply in clinical practice. Approximately 20% of patients discontinue therapy due to treatment failure, adverse effects, and other reasons. In addition, expert consensus recommendations are lacking to guide physicians in the optimal use of BoNT-A for CD. Among the issues still to be clarified is the optimal dosing frequency. The generally accepted standard for intervals between BoNT-A injections is ≥12 weeks; however, this standard is based primarily on the methodology of pivotal trials for the BoNT-A products, rather than on evidence that it is optimal in comparison to other intervals. While some retrospective, observational studies of BoNT-A used in clinical practice appear to support the use of ≥12-week dosing intervals, it is often unclear in these studies how the need for reinjection was determined. In contrast, a prospective dose-ranging trial in which patients were allowed to request reinjection as early as 8 weeks showed that about half of patients receiving abobotulinumtoxinA, at the currently recommended initial dose of 500 U, requested reinjection at 8 weeks. Moreover, results from an open-label, 68-week extension phase of the pivotal trial of incobotulinumtoxinA showed that 47.1% of patients had received reinjection at ≤12 weeks. Ongoing studies, such as the Cervical Dystonia Patient Registry for Observation of BOTOX® Efficacy (CD PROBE), may help clarify this question of optimal dosing intervals for BoNT-A in CD.

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.

Purification and characterization of neurotoxin complex from a dual toxin gene containing Clostridium Botulinum Strain PS-5

Botulinum neurotoxins are produced as a toxin complex (TC) which consists of neurotoxin (NT) and neurotoxin associated proteins. The characterization of NT in its native state is an essential step for developing diagnostics and therapeutic countermeasures against botulism. The presence of NT genes was validated by PCR amplification of toxin specific fragments from genomic DNA of Clostridium botulinum strain PS-5 which indicated the presence of both serotype A and B genes on PS-5 genome. Further, TC was purified and characterized by Western blotting, Digoxin-enzyme linked immunosorbent assay, endopeptidase activity assay, and Liquid chromatography-Mass spectrometry. The data showed the presence of serotype A specific neurotoxin. Based on the analysis of neurotoxin genes and characterization of TC, PS-5 strain appears as a serotype A (B) strain of C. botulinum which produces only serotype A specific TC in the cell culture medium.

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.

Analysis of the mechanisms that underlie absorption of botulinum toxin by the inhalation route

Botulinum toxin is a highly potent oral and inhalation poison, which means that the toxin must have an efficient mechanism for penetration of epithelial barriers. To date, three models for toxin passage across epithelial barriers have been proposed: (i) the toxin itself undergoes binding and transcytosis; (ii) an auxiliary protein, HA35, transports toxin from the apical to the basal side of epithelial cells; and (iii) an auxiliary protein, HA35, acts on the basal side of epithelial cells to disrupt tight junctions, and this permits paracellular flux of toxin. These models were evaluated by studying toxin absorption following inhalation exposure in mice. Three types of experiments were conducted. In the first, the potency of pure neurotoxin was compared with that of progenitor toxin complex, which contains HA35. The results showed that the rate and extent of toxin absorption, as well as the potency of absorbed toxin, did not depend upon, nor were they enhanced by, the presence of HA35. In the second type of experiment, the potencies of pure neurotoxin and progenitor toxin complex were compared in the absence or presence of antibodies on the apical side of epithelial cells. Antibodies directed against the neurotoxin protected against challenge, but antibodies against HA35 did not. In the final type of experiment, the potency of pure neurotoxin and toxin complex was compared in animals pretreated to deliver antibodies to the basal side of epithelial cells. Once again, antibodies directed against the neurotoxin provided resistance to challenge, but antibodies directed against HA35 did not. Taken collectively, the data indicate that the toxin by itself is capable of crossing epithelial barriers. The data do not support any hypothesis in which HA35 is essential for toxin penetration of epithelial barriers.