Immunological aspects of botulinum toxin therapy

Update on Non-Interchangeability of Botulinum Neurotoxin Products

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

Effectiveness of repeated injections of botulinum toxin A on gait and fatigue in adults with spastic paraparesis secondary to multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is the most common neurologic disease in young adults. Spasticity is one of its most disabling symptoms, with botulinum toxin A type A (BoNT-A) being one of the treatments of choice for this symptom.

OBJECTIVE

We assessed the response to abobotulinumtoxinA in improving walking ability and fatigue in patients with spastic paraparesis caused by MS.

METHODS

We performed a real-world, multicenter, prospective, open-label low-intervention trial in 84 patients with MS and spastic paraparesis of the lower limbs infiltrated with abobotulinumtoxinA (LINITOX study). The response of spasticity, walking ability and fatigue is analyzed in 4 cycles of ultrasound-guided injection in the lower limbs.

RESULTS

The patients improved their walking ability by an average of 11.34% meters measured with 6-Minute Walk Test (6MWT), and decreased the percentage of fatigue by 6.86% (4.66 percentage points less), in the 12-Item Multiple Sclerosis Walking Scale (MSWS-12) 4 weeks after abobotulinumtoxinA injection, both values are statistically significant. This improvement seems to persist over time, throughout the cycles.

CONCLUSION

We found improved walking ability and less fatigue in patients with MS-related spastic paresis of the lower limbs after injection of abobotulinumtoxinA.

Botulinum toxin antibody titres: measurement, interpretation, and practical recommendations

Botulinum toxin (BT) therapy may be blocked by antibodies (BT-AB) resulting in BT-AB induced therapy failure (ABF). BT-AB may be detected by the mouse lethality assay (MLA), the mouse diaphragm assay (MDA) and the sternocleidomastoid test (SCMT). For the first time, we wanted to compare all three BT-AB tests and correlate them to subjective complaint of complete or partial secondary therapy failure in 37 patients with cervical dystonia (25 females, 12 males, age 51.2 ± 11.4 years, disease duration 12.4 ± 6.3 years). Complaint of therapy failure was not correlated with any of the BT-AB tests. MDA and MLA are closely correlated, indicating that the MDA might replace the MLA as the current gold standard for BT-AB measurement. The SCMT is closely correlated with MDA and MLA confirming that BT-AB titres and BT's paretic effect are in a functional balance: low BT-AB titres are reducing BT's paretic effect only marginally, whereas high BT-AB titres may completely block it. When therapy failure is classified as secondary and permanent, BT-AB evaluation is recommended and any BT-AB test may be applied. For MDA > 10 mU/ml, MLA > 3 and SCMT < 25%, ABF is highly likely. MDA < 0.6 mU/ml are therapeutically irrelevant. They are neither correlated with pathologic MLA nor with pathologic SCMT. They should not be the basis for treatment decisions, such as switching dystonia therapy to deep brain stimulation. All other results are intermediate results. Their interactions with therapy efficacy is unpredictable. In these cases, BT-AB tests should be repeated or one or two additional test methods should be applied.

The Immunology of Botulinum Toxin Therapy: A Brief Summary

Like all proteins foreign to the human body, also botulinum toxin (BT) is antigenic and may stimulate an immune response with formulation of antibodies (BT-AB). Affected patients may no longer respond to BT therapy and various degrees of BT-AB related therapy failure (ABF) may result. We want to review the immunological interactions between BT and BT-AB, the prevalence, the time course and the risk factors for BT-AB formation as they are related to the treatment algorithms, the patient's immune system and to exogenic factors. Special emphasis is placed on various features of the BT drugs including the specific biological activity (SBA) as a predictor of their antigenicity. Quantitative detection of BT-AB by the mouse diaphragm assay will be demonstrated. As ABF may have serious consequences for patients affected, careful risk factor analysis is warranted to reduce them wherever possible.

Effectiveness and safety of acupuncture for post-stroke spasticity: A systematic review and meta-analysis

Objective

This systematic review and meta-analysis aimed to comprehensively evaluate the effectiveness and safety of acupuncture for post-stroke spasticity.

Methods

Nine electronic databases were searched from their inception to 6 June 2022, to identify randomized-controlled trials (RCTs) that investigated the effectiveness and safety of acupuncture for post-stroke spasticity. Two reviewers independently screened the studies, extracted the data, assessed the risk of bias. The reporting quality of interventions in controlled trials of acupuncture was evaluated using Revised Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA). The RevMan 5.4 and R 4.2.0 software were used for statistical analysis.

Results

A total of 88 eligible studies were included, involving 6,431 individuals. The pooled data demonstrated that acupuncture combined with conventional rehabilitation (CR) was superior to CR in reducing the Modified Ashworth Scale (MAS) score (standardized mean difference [SMD] = -0.73; 95% CI = -0.83 to -0.63; I 2 = 65%; low certainty of evidence). The favorable results were also observed in comparisons of acupuncture vs. CR (SMD = -0.22, 95% CI = -0.36 to -0.07; I 2 = 49%; moderate certainty of evidence). Subgroup analysis showed that acupuncture treatment with a frequency of once or twice a day was more effective than CR. In addition, the antispasmodic effect of acupuncture treatment increased with more sessions. Four studies explicitly reported slight acupuncture-related adverse events.

Conclusion

Acupuncture could be recommended as adjuvant therapy for spasticity after stroke. However, due to the high risk of bias and heterogeneity of the included studies, the effectiveness of acupuncture for post-stroke spasticity remains to be confirmed.

Extracorporeal Shock Wave Therapy on Spasticity After Upper Motor Neuron Injury: A Systematic Review and Meta-analysis

OBJECTIVE

The aim of the study was to evaluate the effectiveness and safety of extracorporeal shock wave therapy on spasticity after upper motor neuron injury.

DESIGN

Eight electronic databases were searched systematically from their inception to August 3, 2021, to provide robust evidence for the efficacy of extracorporeal shock wave therapy for spasticity and range of motion after upper motor neuron injury. Study screening, data extraction, risk of bias assessment, and evaluation of the certainty of evidence were performed independently by two independent reviewers. Data analysis was conducted using RevMan 5.3.5 and R 3.6.1 software.

RESULTS

Forty-two studies with 1973 patients who met the eligibility criteria were selected from articles published from 2010 to 2021, of which 34 were included in the meta-analysis. A comparison intervention revealed that extracorporeal shock wave therapy significantly decreased the Modified Ashworth Scale score and increased the passive range of motion of a joint. Regarding the safety of extracorporeal shock wave therapy, slightly adverse effects, such as skin injury, bone distortion, muscle numbness, pain, petechiae, and weakness, were reported in five studies.

CONCLUSIONS

Extracorporeal shock wave therapy may be an effective and safe treatment for spasticity after upper motor neuron injury. However, because of poor methodological qualities of the included studies and high heterogeneity, this conclusion warrants further investigation.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME.

CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Determine the impact of extracorporeal shock wave therapy on spasticity after upper motor neuron injury; (2) Describe the factors that affect the efficacy of extracorporeal shock wave therapy on spasticity; and (3) Discuss the mechanism of action of extracorporeal shock wave therapy on spasticity.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Botulinum toxin therapy: past, present and future developments

Although botulinum toxin (BT) is now being used in a large number of different indications in numerous medical specialties, there is still dynamic and rapid development. Treatment algorithms were improved by the introduction of BT short-interval therapy, BT high-dose therapy and improved dosing guidelines. Ultrasound guidance may be helpful in special situations. New indication areas including depression and inflammatory processes are being explored. Drug development projects are mainly focusing on onabotulinumtoxinA analogues, some are addressing liquid preparations and modifications of BT's duration of action. Recombinant BT may simplify production processes. Cell-based assays for potency measurement will soon be required by registration authorities. Treatment algorithms will be further refined and indications will be expanded. New indication areas are still uncertain. BT type A will remain the drug substance of choice. Removal of complexing proteins seems logical. Whether there is a need for BT drugs with modified duration of action and for liquid preparations, is unclear. Bringing BT therapy to those who need it, is the biggest challenge. Current high-price business models need to be changed, either by employing a biosimilar registration approach or by referring to companies from countries where business models are based on different cost structures.

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.

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.

Long-term efficacy and safety of botulinum toxin treatment for cervical dystonia: a critical reappraisal

Introduction: Botulinum toxin (BoNT) injections represent the gold standard treatment for cervical dystonia (CD). Different types of BoNT have been used for the treatment of CD, but only two serotypes, BoNT type A (BoNT-A) and type B (BoNT-B), have been approved by regulatory agencies. Efficacy and safety of BoNT have been well documented by many short-term studies, but the longterm effects have been investigated only relatively recently.Areas covered: In the present review, we aimed to critically reappraise the existing evidence on the long-term efficacy and safety of BoNT treatment in CD. The examined studies mainly explored BoNT-A serotypes. Only a few studies examined the long-term effects of BoNT-B serotypes, and only one head-to-head comparison between BoNT-A and BoNT-B was found. BoNT was consistently reported to be an effective and safe treatment for CD patients, with good outcomes and a few adverse events in the long-term. However about a third of patients still drop out from the treatment during a long-term follow-up.Expert opinion: We conclude that BoNT is safe and effective in the long-term treatment of patients with CD. Additional studies are needed to further explore patients real-life experiences and perspectives to better understand the long-term outcomes and reasons for discontinuation of treatment.

Long-term stable efficacy of botulinum toxin A in facial movement disorders with no need for increasing dose

Botulinum toxin A is considered an effective treatment for involuntary facial movements. We examined whether treatment efficacy maintained or changed over time with two products, Botox and Dysport, in patients with hemifacial spasm, facial synkinesis and benign essential blepharospasm.We retrospectively investigated 87 consecutive patients (51 women, 36 men) who had undergone treatment for ≥6 years. Long-term effects, as well as side effects of Botox or Dysport local injections were evaluated. The first three treatments were considered the titration period and not taken into account when testing for dose changes.Mean treatment duration was 10 years (range 6-11, SD 1.0), 2441 treatments were administered, 1162 with Botox and 1279 with Dysport, the two brands were interchanged as needed. Good to full improvement was seen in 90% of patients both with both brands. Injection doses and treatment responses were consistent during the study with both drugs. No major side effects were reported, and relatively few minor adverse events were reported, with clear reduction from the titration period (6.1%), to the remainder of the study (3.9%).Botulinum toxin (BTX-A) is a satisfactory long-term treatment without need for dose increase over. Both Botox and Dysport were effective when used interchangeably.

Lantox-The Chinese Botulinum Toxin Drug-Complete English Bibliography and Comprehensive Formalised Literature Review

In 1997, lanbotulinumtoxinA (LAN) was introduced in China. It is now available in Asia, Latin America and Eastern Europe under various brand names including Hengli®, Lantox®, Prosigne®, Lanzox®, Redux®, Liftox®, HBTX-A and CBTX-A. The literature on LAN is mostly published in Chinese language, restricting its international accessibility. We, therefore, wanted to generate a complete English bibliography of all LAN publications and then use it for a comprehensive formalised literature review. Altogether, 379 LAN publications (322 in Chinese and 57 in English) were retrieved from PubMed and Science and Technology Paper Citation Database. Indications covered are motor (257), glandular (16), pain (32) and aesthetics (48). Topics are neurological (250), aesthetic (48), paediatric (38), ophthalmological (18), urological (9), methodological (6), gastroenterological (5), ear, nose and throat (4) and surgical (1). Seventy-one publications are randomised controlled trials, forty-one publications are interventional studies and observational studies, fifteen publications are case studies, eighteen publications are reviews, and two publications are guidelines. LAN publications cover all relevant topics of BT therapy throughout a period of more than 20 years. This constitutes a publication basis resembling those of other BT drugs. None of the LAN publications presents data contradictory to those generated with other BT type-A drugs. LAN seems to have a similar efficacy and safety features when compared to onabotulinumtoxinA using a 1:1 LAN- onabotulinumtoxinA conversion ratio. Large controlled multicentre studies will become necessary for LAN's registrations in Europe and North America.

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

Objective

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

Methods

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

Results

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

Conclusions

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

Clinical duration of action of different botulinum toxin types in humans

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

Long-term Effects of Extracorporeal Shock Wave Therapy on Poststroke Spasticity: A Meta-analysis of Randomized Controlled Trials

OBJECTIVE

The purpose of this meta-analysis was to assess the long-term effects of extracorporeal shock wave therapy (ESWT) on post-stroke spasticity.

DATA SOURCES

An electronic search of EMBASE, MEDLINE, and Cochrane Central Register of Controlled Trials (CENTRAL) with hand search of relevant papers were performed on 20 June 2019.

REVIEW METHODS

This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched the literature for randomized controlled trials of ESWT in stroke patients with spasticity. The primary outcome was the Modified Ashworth Scale (MAS) grade, and the second outcomes were the Visual Analogue Scale (VAS), range of motion (ROM) of joint, the Fugl-Meyer assessment (FMA) grade and adverse events. Two authors independently extracted data, assessed trial eligibility and risk of bias. Meta-analyses were performed using RevMan 5.3 software.

RESULTS

We extracted data from 8 randomized controlled trials (301 participants). At long-term follow-up, ESWT significantly reduced MAS (Weighted Mean Difference (WMD) = -.36, 95% confidence interval (CI) = -.53 to -.19, I² = 68%; P < .001) and VAS (WMD = -.94, 95% CI = -1.51 to -.37, I² = 15%; P = .001), enhanced ROM (WMD = 5.97, 95% CI = 2.76 to 9.18, I² = 0%; P < .001) and FMA (WMD = 1.26, 95% CI = .29 to 2.24, I² = 96%; P = .01).

CONCLUSIONS

ESWT showed long-term effects in relieving spasticity, while reducing pain, enhancing ROM and motor function in stroke patients.

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.

Immunogenicity induced by botulinum toxin injections for limb spasticity: A systematic review

BACKGROUND

The imputability of neutralizing antibodies (NABs) in secondary non-response (SnR) to botulinum toxin (BoNT) injections for limb spasticity is still debated.

OBJECTIVE

This systematic literature review aimed to determine the prevalence of NABs after BoNT injections for limb spasticity and analyze their determinants and their causal role in SnR.

METHODS

We searched MEDLINE via PubMed, Cochrane and Embase databases for articles published during 1990-2018. Two independent reviewers extracted the data and assessed the quality of studies with a specific scale (according to PRISMA and STROBE guidelines). Because the techniques used to detect NABs did not influence the results, we calculated the global (all studies) sensitivity and specificity of NAB positivity to reveal SnR.

RESULTS

We included 14 articles published from 2002 to 2018 (including an epublication) describing 5 randomized controlled trials and 5 interventional and 4 observational studies. The quality was satisfactory (mean score 18/28 arbitrary units). NAB detection was the primary criterion in 5 studies and a secondary criterion in 9. In total, 1234 serum samples for 1234 participants (91% with stroke) were tested after injection. NAB prevalence was about 1%, with no significant difference among formulations. NAB positivity seemed favoured by long-duration therapy with high doses and a short interval between injections. The identification of non-response by NAB positivity had poor global sensitivity (56%) but very high specificity (99.6%). No consensual criteria were used to diagnose non-response to BoNT injection.

CONCLUSIONS

NAB prevalence is much lower after BoNT treatment for limb spasticity than cervical dystonia. Consensual criteria must be defined to diagnose non-response to BoNT injection. Because immunogenicity is not the most common cause of non-response to BoNT injection, NABs should be sought in individuals with SnR with no other cause explaining the treatment inefficacy. A test with 100% specificity is recommended. In cases for which immunogenicity is the most likely cause of non-response to BoNT injections, some biological arguments suggest trying another BoNT, but no clinical evidence supports this strategy.

Clinical Pharmacology of Botulinum Toxin Drugs

Botulinum toxin (BT) has changed from a deadly poison to a novel therapeutic principle for a large number of disorders in many medical areas.BT drugs are special in many ways: they are biologicals, their active ingredient BT is not patentable, their spectrum of clinical applications is extremely broad, their dose range is enormous, their mode of action is local and their life cycles are special.This review covers BT's therapeutic mode of action, time course of action, target tissues, pharmacological profile, adverse effects, interactions, potency labelling and antigenicity as well as BT's therapeutic preparations.

In silico mutagenesis: decreasing the immunogenicity of botulinum toxin type A

Botulinum toxin serotype A is a prominent therapeutic enzyme, for both clinical and cosmetic uses. Since this protein is produced by bacteria, it exhibits an allergenic effect when subjected to human therapy. Protein mutagenesis is one method to improve the characteristics of protein. However, in silico study is needed to give suggestion of which amino acid should be mutated. Hence, a lot of money and time can be saved. This study initially screened which residue of the Botulinum toxin serotype A is B-cell epitopes both linearly and conformationally. By overlapping the B-cell epitopes with the excluded conserve sequence, seven residues were allowed to be mutated. There were two proposed muteins showing a reduction in the antigenicity probability: ΔE147, E510F, T1062F, ΔE1080, N1089M and ΔQ1090; and ΔE147, E510F, T1062F, E1080W, N1089M and ΔQ1090. Molecular dynamics simulation of the 3D proposed muteins indicated an increase of flexibility in both muteins compared to that in the native protein. Both muteins have lower antigenicity. In addition, they are similar in structure, stability and functionality compared to the native protein.

Antibody-induced failure of botulinum toxin therapy: re-start with low-antigenicity drugs offers a new treatment opportunity

Botulinum toxin (BT) can stimulate formation of BT antibodies (BTAB) thus producing Antibody-Induced Therapy Failure (ABTF). BTAB titres may drop eventually. When BT therapy is then re-started with conventional BT drugs, BTAB titres re-increase promptly. We wanted to study whether the use of the low-antigenicity BT drug incobotulinumtoxinA (INCO) can prevent this re-increase. 8 patients with cervical dystonia and ABTF with maximal BTAB titres (6 women, 2 men, age 41.4 ± 12.1 years, disease duration 6.6 ± 4.7 years) were studied. ABTF ocurred under onabotulinumtoxinA (ONA) in five patients and under abobotulinumtoxinA (ABO) in 3 after 8.8 ± 3.8 injection series and a treatment time of 962.0 ± 473.2 days. After 3881.5 ± 2468.3 days without BT, all BTAB titres had dropped to insignificant levels before BT therapy was re-started with INCO. Treatment parameters before and after re-start were as follows: single dose 219.2 ± 90.7 MU vs 252.6 ± 109.0 MU (ns), interinjection interval 119.7 ± 18.4 vs 104.5 ± 14.7 days (ns), cumulative dose 1893.8 ± 1161.6 MU vs 5130.4 ± 3602.5 MU (ns), treatment time 962.0 ± 505.9 vs 1895.4 ± 1211.4 days (ns) and number of injection series 8.8 ± 3.8 vs 19.3 ± 11.8 (ns). Repeated BTAB measurements and clinical examinations did not reveal any signs of ABTF after re-start. INCO offers a new and long-term treatment opportunity for ABTF patients when their BTAB titres have dropped. Our observations also confirm lower antigenicity of INCO compared to conventional BT drugs.

Quantifying and Reducing Retained Botulinum Toxin Postinjection

BACKGROUND

Retained botulinum toxin solution may be visible in vials and syringe tips after mixing and presumed complete injections, leaving patients without the full prescribed dose.

OBJECTIVE

To quantify the mean amount of retained toxin within vials, syringes, and needles following spasticity injections (phase 1) and to design/test a targeted intervention for reduced retained toxin (phase 2).

DESIGN

Prospective cohort quality assurance study.

SETTING

Outpatient spasticity program in a rehabilitation facility.

PARTICIPANTS

Nine physicians specializing in physical medicine and rehabilitation, performing successive mixing and injections for spasticity with onabotulinumtoxinA or incobotulinumtoxinA.

METHODS

After initial review (phase 1), recommendations were made (phase 2) including not inverting the vial to withdraw medication unless needed, favoring 2-mL dilutions when possible, and decapping of vials for more complete medication withdrawal.

MAIN OUTCOME MEASUREMENTS

Retained volume of toxin solution that was not injected and estimated retained units of toxin.

RESULTS

A total of 157 vials of botulinum toxin A were tested. Of the 82 initial, phase 1, preintervention vials (8200 units), 5.5% (∼452 units) of toxin solution was retained following mixing and injections. One and 3-mL syringe tips contained a mean of 3.32 and 1.44 units of toxin respectively. Within vials, saline dilutions with 2 mL contained less mean retained toxin (1.89 vs 3.31 units) relative to 1-mL dilution. Awareness of monitoring significantly decreased retained solution in vials (0.035 mL vs 0.069 mL for naïve group, P = .002). Phase 2, postintervention testing of 75 vials demonstrated that withdrawing toxin from the inferior edge from a non-inverted vial reduced the retained toxin by 32.8% (P < .001). Decapping the vial further reduced the mean retained toxin to 0.42 units per vial (81.9% reduction, P < .001).

CONCLUSIONS

A potentially clinically significant amount of botulinum toxin solution is retained following mixing and injections. Implementation of guidelines significantly decreased wasted botulinum toxin.

LEVEL OF EVIDENCE

III.

An update on new and unique uses of botulinum toxin in movement disorders

The therapeutic applications of botulinum toxin (BoNT) have grown manifold since its initial approval in 1989 by the US Food and Drug Administration (FDA) for the treatment of strabismus, blepharospasm, and other facial spasms. Although it is the most potent biologic toxin known to man, long-term studies have established its safety in the treatment of a variety of neurologic and non-neurologic disorders. This review focuses on some novel and uncommon uses of BoNT in the treatment of movement disorders, such as oromandibular dystonia, including bruxism, anterocollis, camptocormia, tremor, tics, tardive and levodopa-induced dyskinesia, and restless legs syndrome. Despite a paucity of randomized controlled trials and lack of FDA approval for these movement disorders, there is growing body of evidence that BoNT provides benefit to patients with these hyperkinetic movement disorders and that BoNT is a safe treatment when used by clinicians skilled in the administration of the drug for these conditions.

Botulinum toxin: State of the art

Botulinun neurotoxin (BoNT) has emerged as one of the most multipurpose therapeutic agents in modern medicine with more clinical applications than any other drug currently on the market. Initially developed in the treatment of strabismus and neurologic movement disorders, the use of botulinun neurotoxin has been expanding during the past 3 decades to include the treatment of a variety of ophthalmologic, gastrointestinal, urologic, orthopedic, dermatologic, dental, secretory, painful, cosmetic, and other conditions. In addition to onabotulinumtoxinA (Botox), abobotulinumtoxinA (Dysport), incobotulinumtoxinA (Xeomin), and RimabotulinumtoxinB (Myobloc or NeuroBloc) there are other novel botulinun neurotoxin products currently in development. With a better understanding of the cellular mechanisms of botulinun neurotoxin and advances in biotechnology, future botulinun neurotoxin products will likely be even more effective and customized to the specific indication and tailored to the needs of the patients. © 2017 International Parkinson and Movement Disorder Society.