In-vivo comparison of the neurotoxic potencies of incobotulinumtoxinA, onabotulinumtoxinA, and abobotulinumtoxinA

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.

Neuromuscular recovery from botulism involves multiple forms of compensatory plasticity

Introduction

Botulinum neurotoxin (BoNT) causes neuroparalytic disease and death by blocking neuromuscular transmission. There are no specific therapies for clinical botulism and the only treatment option is supportive care until neuromuscular function spontaneously recovers, which can take weeks or months after exposure. The highly specialized neuromuscular junction (NMJ) between phrenic motor neurons and diaphragm muscle fibers is the main clinical target of BoNT. Due to the difficulty in eliciting respiratory paralysis without a high mortality rate, few studies have characterized the neurophysiological mechanisms involved in diaphragm recovery from intoxication. Here, we develop a mouse model of botulism that involves partial paralysis of respiratory muscles with low mortality rates, allowing for longitudinal analysis of recovery.

Methods and results

Mice challenged by systemic administration of 0.7 LD50 BoNT/A developed physiological signs of botulism, such as respiratory depression and reduced voluntary running activity, that persisted for an average of 8-12 d. Studies in isolated hemidiaphragm preparations from intoxicated mice revealed profound reductions in nerve-elicited, tetanic and twitch muscle contraction strengths that recovered to baseline 21 d after intoxication. Despite apparent functional recovery, neurophysiological parameters remained depressed for 28 d, including end plate potential (EPP) amplitude, EPP success rate, quantal content (QC), and miniature EPP (mEPP) frequency. However, QC recovered more quickly than mEPP frequency, which could explain the discrepancy between muscle function studies and neurophysiological recordings. Hypothesizing that differential modulation of voltage-gated calcium channels (VGCC) contributed to the uncoupling of QC from mEPP frequency, pharmacological inhibition studies were used to study the contributions of different VGCCs to neurophysiological function. We found that N-type VGCC and P/Q-type VGCC partially restored QC but not mEPP frequency during recovery from paralysis, potentially explaining the accelerated recovery of evoked release versus spontaneous release. We identified additional changes that presumably compensate for reduced acetylcholine release during recovery, including increased depolarization of muscle fiber resting membrane potential and increased quantal size.

Discussion

In addition to identifying multiple forms of compensatory plasticity that occur in response to reduced NMJ function, it is expected that insights into the molecular mechanisms involved in recovery from neuromuscular paralysis will support new host-targeted treatments for multiple neuromuscular diseases.

Botulinum neurotoxin: A therapeutic powerhouse with broad clinical implications

ABSTRACT

Clostridium botulinum is a Gram-positive bacterium that produces one of the most deadly chemodenervating toxins in the world. To date, six distinct neurotoxins are available for prescription use in the United States. Decades of data across aesthetic therapeutic areas and therapeutic disease states support the safety and efficacy of C. botulinum, providing good symptom management and improved quality of life in appropriately chosen patients. Unfortunately, many clinicians are slow to progress patients to toxin therapy from more conservative measures, and others wrongly interchange the products despite characteristics unique to each. Commensurate with an improved understanding of the complex pharmacology and clinical implications of botulinum neurotoxins is the importance for clinicians to appropriately identify, educate, refer, and/or treat candidate patients. This article provides an overview of the history, mechanism of action, differentiation, indications, and uses for botulinum neurotoxins.

Efficacy and safety of two different botulinum toxin type A dilutions in chronic migraineurs

Botulinum toxin type A is an effective preventive therapy for chronic migraine. Although the guidelines suggest a 50U/ml dilution of OnabotulinumtoxinA (BoNT/A), many clinicians use more concentrated solutions. However, there are no studies regarding the effect and safety of 100U/ml BoNT/A dilution with the saline solution following the PREEMPT paradigm. Our primary goal was to evaluate the efficacy, in reducing migraine frequency, and safety of two different BoNT/A dilutions (100U/ml vs 50U/ml) in the treatment of Chronic migraine. Our secondary goal was to determine the predictors of BoNT/A response. We retrospectively collected data from 113 chronic migraine patients treated with 3 rounds of BoNT/A according to the PREEMPT protocol as a preventive therapy. Patients were divided into two groups, based on BoNT/A dilution: 50U/ml (49 patients) vs. 100U/ml (64 patients) of sodium chloride 0.9%. We compared the migraine days/month, intensity, and intake of symptomatic medications at the baseline with the data obtained after the treatment; moreover, we evaluated the occurrence of adverse effects observed in the two groups. There was no difference regarding efficacy and safety between the two groups except for eyelid ptosis, which was more common in the 50U/ml BoNT/A group (p 0.018). Unilateral localization of migraine was associated with a more favorable outcome (OR 5.593, C.I. 2.358-13.268; p < 0.001) while Major Depressive Disorder predicted a less favorable response (OR 0.213, C.I. 0.087-0.523; p < 0.001). In our study, BoNT/A dilution did not influence the response to the therapy, but 100U/ml dilution could reduce the risk of eyelid ptosis. Unilateral localization of migraine pain might predict a more favorable response to the therapy, while the presence of a Major Depressive Disorder might predict a less favorable response.

A Preclinical Study Comparing the Activity and Potency of OnabotulinumtoxinA and PrabotulinumtoxinA

Objective

The goal of this study was to compare the unit-to-unit biological activity of the vacuum-dried formulation of prabotulinumtoxinA (prabotA) and onabotulinumtoxinA (onabotA) in preclinical assays.

Methods

Reconstituted 100 U vials of prabotA and onabotA were tested in 3 distinct assays: plate-capture light chain activity (PC-LCA), measuringlight chain enzymatic activity after recovery of toxin from reconstituted product using a proprietary toxin capture step; cell-based potency assay (CBPA), measuring the intoxication steps of binding, translocation, and light chain activity (synaptosomal-associated protein 25 [SNAP25] cleavage); and mouse Digit Abduction Score (DAS), evaluating muscle paresis. Each assay tested 3 separate prabotA and onabotA lots on several independent test dates.

Results

Multiple orthogonal assays established that when assessed on a unit-to-unit basis, the biological activity of prabotA is lower than that of onabotA. In the PC-LCA and CBPA assays, onabotA displayed 1.51 ± 0.14-fold higher (mean ± SD) and 1.33 ± 0.07-fold higher (mean of pooled lots ± SEM) activity than prabotA, respectively. Similarly, the mouse DAS data showed that onabotA had 1.4 ± 0.1-fold higher (mean ± SEM) potency than prabotA. Results of all 3 assays demonstrated differences in potency, efficacy, and duration of action between onabotA and prabotA on a unit-to-unit basis.

Conclusion

Preclinical assays established differences in the biological activity of onabotA and prabotA, supporting that the units of biological activity are not interchangeable.

Subcutaneous BoNT/A Injection for Intractable Pain and Disability in Complex Regional Pain Syndrome: A Case Report

We treated a 51-year-old woman with refractory Complex Regional Pain Syndrome type I (CRPS-I) involving her left hand and forearm with subcutaneous injections of BoNT/A. The injections were performed every 3 months, with a total of six treatments. Each treatment was able to effectively improve pain and motor impairment; however, the duration of the effect was limited to only a few months. BoNT/A could improve patients’ quality of life with CRPS; however, extensive clinical studies are needed to determine its role in clinical practice.

Intramuscular tetanus neurotoxin reverses muscle atrophy: a randomized controlled trial in dogs with spinal cord injury

BACKGROUND

Motor symptoms of spinal cord injury (SCI) considerably impair quality of life and are associated with a high risk of secondary diseases. So far, no pharmacological treatment is available for these symptoms. Therefore, we conducted a randomized, double-blinded, placebo-controlled study in dogs with spontaneous SCI due to disc herniation to test whether a reduction of spinal inhibitory activity by intramuscular injections of tetanus neurotoxin (TeNT) alleviates motor symptoms such as muscle atrophy or gait function.

METHODS

To this end, 25 dogs were treated with injections of either TeNT or placebo into their paretic hindlimb muscles. Effects of TeNT on muscle thickness were assessed by ultrasound, while effects on gait function were measured using the modified functional scoring system in dogs.

RESULTS

Four weeks after the TeNT injections, muscle thickness of the gluteus medius muscle (before median 1.56 cm [inter-quartile range {IQR} 1.34-1.71 cm] and after median 1.56 cm [IQR 1.37-1.85 cm], P-value 0.0133) as well as of the rectus femoris muscle (before median 0.76 cm [IQR 0.60-0.98 cm] and after median 0.93 cm [IQR 0.65-1.05 cm], P-value 0.0033) significantly increased in the TeNT group. However, there was no difference in gait function between the TeNT and placebo groups. The treatment was well tolerated by all dogs without any signs of generalized tetanus symptoms or any spreading of effects beyond the lumbar level of the injected hindlimbs.

CONCLUSIONS

With regard to the beneficial effects on muscle thickness, intramuscular injections of TeNT represent the first pharmacological approach that focally reverses muscle atrophy in SCI. Moreover, the study data support the safety of this treatment when TeNT is used at low dose.

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.

A Novel Running Wheel Mouse Model for Botulism and Its Use for the Evaluation of Postsymptom Antitoxin Efficacy

Antitoxin is currently the only approved therapy for botulinum intoxications. The efficacy of antitoxin preparations is evaluated in animals. However, while in practice antitoxin is administered to patients only after symptom onset, in most animal studies, it is tested in relation to time postintoxication. This may be attributed to difficulties in quantitating early botulism symptoms in animals. In the current study, a novel system based on high-resolution monitoring of mouse activity on a running wheel was developed to allow evaluation of postsymptom antitoxin efficacy. The system enables automatic and remote monitoring of 48 mice simultaneously. Based on the nocturnal activity patterns of individual naive mice, two criteria were defined as the onset of symptoms. Postsymptom treatment with a human-normalized dose of antitoxin was fully protective in mice exposed to 4 50% lethal doses (LD₅₀s) of botulinum neurotoxin serotype A (BoNT/A) and BoNT/B. Moreover, for the first time, a high protection rate was obtained in mice treated postsymptomatically, following a challenge with BoNT/E, the fastest-acting BoNT. The running wheel system was further modified to develop a mouse model for the evaluation of next-generation therapeutics for progressive botulism at time points where antitoxin is not effective. Exposure of mice to 0.3 LD₅₀ of BoNT/A resulted in long-lasting paralysis and a reduction in running activity for 16 to 18 days. Antitoxin treatment was no longer effective when administered 72 h postintoxication, defining the time window to evaluate next-generation therapeutics. Altogether, the running wheel systems presented herein offer quantitative means to evaluate the efficacy of current and future antibotulinum drugs.

Real-World Dosing of OnabotulinumtoxinA and IncobotulinumtoxinA for Cervical Dystonia and Blepharospasm: Results from TRUDOSE and TRUDOSE II

The real-world use of onabotulinumtoxinA and incobotulinumtoxinA for cervical dystonia and blepharospasm treatment was assessed in two separate retrospective studies using identical protocols (TRUDOSE and TRUDOSE II). The studies were conducted in Mexico, Norway, and United Kingdom and designed to evaluate dose utilization of the two botulinum toxins in clinical practice. Eighty-three patients treated with both onabotulinumtoxinA and incobotulinumtoxinA for ≥2 years for each botulinum toxin were included, (52, cervical dystonia; 31, blepharospasm). All patients switched from onabotulinumtoxinA to incobotulinumtoxinA for administrative/financial reasons. A range of dose ratios (incobotulinumtoxinA to onabotulinumtoxinA) was reported; with the majority of dose ratios being >1. The mean dose ratio was >1 regardless of the study site or underlying clinical condition. The inter-injection interval was significantly longer for onabotulinumtoxinA versus incobotulinumtoxinA when assessed for all patients (15.5 vs. 14.3 weeks; p = 0.006), resulting in fewer onabotulinumtoxinA treatments over the study time period. Consistent with product labeling, no single fixed-dose ratio exists between incobotulinumtoxinA and onabotulinumtoxinA. The dosage of each should be individualized based on patient needs and used as per product labeling. These real-world utilization data may have pharmacoeconomic implications.

Botulinum Toxin Type A to Improve Facial Symmetry in Facial Palsy: A Practical Guideline and Clinical Experience

Unilateral peripheral facial nerve palsy jeopardizes quality of life, rendering psychological consequences such as low self-esteem, social isolation, anxiety, and depression. Among therapeutical approaches, use of Botulinum toxin type A (BoNT-A) on the nonparalyzed side has shown promising results and improvement of quality of life. Nevertheless, the correct technique is paramount, since over-injection of the muscles can result in lack of function, leading to a "paralyzed" appearance, and even worse, functional incompetence, which may cause greater distress to patients. Therefore, the objective of this article is to provide a practical guideline for botulinum toxin use in facial palsy. To this aim, adequate patient assessment, BoNT-A choice, injection plan and dosage, and injection techniques are covered.

Comparative Pharmacodynamics Study of 3 Different Botulinum Toxin Type A Preparations in Mice

A new complexing protein-free botulinum toxin Type A (CBoNT) with the same mechanism of action as the botulinum toxin complex onabotulinumtoxinA (OBoNT) and complexing protein-free incobotulinumtoxinA (IBoNT) was recently developed.

Duration of Symptom Relief Between Injections for AbobotulinumtoxinA (Dysport®) in Spastic Paresis and Cervical Dystonia: Comparison of Evidence From Clinical Studies

Background: Botulinum toxin-A is a well-established treatment for adult and pediatric spastic paresis and cervical dystonia. While guidelines and approved labels indicate that treatment should not occur more frequently than every 12 weeks, studies and real-world evidence show that the timing of symptom recurrence between treatments may vary. Methods: We report retreatment criteria and response duration (retreatment intervals) from four pivotal, double-blind, placebo-controlled studies with open-label extensions involving patients treated with abobotulinumtoxinA (aboBoNTA) for upper limb (NCT01313299) or lower limb (NCT01249404) spastic paresis in adults, lower limb spastic paresis in children (NCT01249417), and cervical dystonia in adults (NCT00257660). We review results in light of recently available preclinical data. Results: In spastic paresis, 24.0-36.9% of upper limb patients treated with aboBoNTA and 20.1-32.0% of lower limb patients did not require retreatment before 16 weeks. Moreover, 72.8-93.8% of aboBoNTA-treated pediatric patients with lower limb spastic paresis did not require retreatment before 16 weeks (17.7-54.0% did not require retreatment before 28 weeks). In aboBoNTA-treated patients with cervical dystonia, 72.6-81.5% did not require retreatment before 16 weeks. Conclusion: AboBoNTA, when dosed as recommended, offers symptom relief beyond 12 weeks to many patients with spastic paresis and cervical dystonia. From recently available preclinical research, the amount of active neurotoxin administered with aboBoNTA might be a factor in explaining this long duration of response.

The use of the dynamic weight bearing test to assess the effects of acute, intramuscularly administered botulinum neurotoxin type A1 in rats

Assessing the efficacy of botulinum neurotoxin (BoNT) in vivo is essential given the growing number of BoNT products used in the clinic. Here, we evaluated the dynamic weight bearing (DWB) test for sensitivity to paralytic effects of BoNT-A following intramuscular administration. The toxin was administered into the gastrocnemius lateralis as a single bolus or into the gastrocnemius lateralis and medialis as two boluses. The effects of BoNT-A in DWB were compared to those in the compound muscle action potential (CMAP) and the Digit Abduction Score (DAS) tests. Female Sprague-Dawley rats received an acute, intramuscular (i.m.) injection of BoNT-A1 (0.1, 1, 10 pg/rat) into the right gastrocnemius muscle, while the left received vehicle. The DWB and CMAP tests were performed one-two days after the injection in order to detect the onset of sub-maximal BoNT-A activity. Both tests were preceded by the DAS test. BoNT-A produced dose-related reductions in both the weight-bearing and surface-bearing outcomes of up to 60% while showing moderate activity in the DAS. BoNT-A effects in the DWB test were well-aligned with those in the CMAP test, which showed dose-dependent reductions in CMAP amplitude and the area under the curve (AUC; up to 100%) as well as increases in latency (up to 130%). The efficacy of BoNT-A in DWB and CMAP was more pronounced with two boluses. Thus, the DWB test can be used to assess the properties of BoNTs following i.m. administration. It can be used to assess the candidate therapies and is more ethical than the mouse lethality assay.

OnabotulinumtoxinA Displays Greater Biological Activity Compared to IncobotulinumtoxinA, Demonstrating Non-Interchangeability in Both In Vitro and In Vivo Assays

Differences in botulinum neurotoxin manufacturing, formulation, and potency evaluation can impact dose and biological activity, which ultimately affect duration of action. The potency of different labeled vials of incobotulinumtoxinA (Xeomin^®; 50 U, 100 U, or 200 U vials; incobotA) versus onabotulinumtoxinA (BOTOX^®; 100 U vial; onabotA) were compared on a unit-to-unit basis to assess biological activity using in vitro (light-chain activity high-performance liquid chromatography (LCA-HPLC) and cell-based potency assay (CBPA)) and in vivo (rat compound muscle action potential (CMAP) and mouse digit abduction score (DAS)) assays. Using LCA-HPLC, incobotA units displayed approximately 54% of the protease activity of label-stated equivalent onabotA units. Lower potency, reflected by higher EC₅₀, ID₅₀, and ED₅₀ values (pooled mean ± SEM), was displayed by incobotA compared to onabotA in the CBPA (EC₅₀: incobotA 7.6 ± 0.7 U/mL; onabotA 5.9 ± 0.5 U/mL), CMAP (ID₅₀: incobotA 0.078 ± 0.005 U/rat; onabotA 0.053 ± 0.004 U/rat), and DAS (ED₅₀: incobotA 14.2 ± 0.5 U/kg; onabotA 8.7 ± 0.3 U/kg) assays. Lastly, in the DAS assay, onabotA had a longer duration of action compared to incobotA when dosed at label-stated equivalent units. In summary, onabotA consistently displayed greater biological activity than incobotA in two in vitro and two in vivo assays. Differences in the assay results do not support dose interchangeability between the two products.

Critical Analysis of Neuronal Cell and the Mouse Bioassay for Detection of Botulinum Neurotoxins

Botulinum Neurotoxins (BoNTs) are a large protein family that includes the most potent neurotoxins known to humankind. BoNTs delivered locally in humans at low doses are widely used pharmaceuticals. Reliable and quantitative detection of BoNTs is of paramount importance for the clinical diagnosis of botulism, basic research, drug development, potency determination, and detection in clinical, environmental, and food samples. Ideally, a definitive assay for BoNT should reflect the activity of each of the four steps in nerve intoxication. The in vivo mouse bioassay (MBA) is the ‘gold standard’ for the detection of BoNTs. The MBA is sensitive, robust, semi-quantitative, and reliable within its sensitivity limits. Potential drawbacks with the MBA include assay-to-assay potency variations, especially between laboratories, and false positives or negatives. These limitations can be largely avoided by careful planning and performance. Another detection method that has gained importance in recent years for research and potency determination of pharmaceutical BoNTs is cell-based assays, as these assays can be highly sensitive, quantitative, human-specific, and detect fully functional holotoxins at physiologically relevant concentrations. A myriad of other in vitro BoNT detection methods exist. This review focuses on critical factors and assay limitations of the mouse bioassay and cell-based assays for BoNT detection.

Botulinum toxin: Pharmacology and injectable administration for the treatment of primary hyperhidrosis

Hyperhidrosis is a dermatological condition defined by excessive sweating beyond thermoregulatory needs with significant effects on patients' quality of life. Hyperhidrosis is categorized as primary or secondary: primary hyperhidrosis is mostly focal and idiopathic, whereas secondary hyperhidrosis is commonly generalized and caused by an underlying medical condition or use of medications. Various surgical and nonsurgical therapies exist for primary hyperhidrosis. Although botulinum toxin is one of the deadliest toxins known, when used in small doses, it is one of the most effective therapies for primary hyperhidrosis. Botulinum toxin injections are widely used as a second-line primary hyperhidrosis treatment option once topical treatment strategies have failed. This article provides an overview of the commercially available botulinum toxin formulations and their applications in the treatment of primary hyperhidrosis.

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.

The Treatment of Hypersalivation in Rett Syndrome with Botulinum Toxin: Efficacy and Clinical Implications

INTRODUCTION

Subjects with Rett syndrome (RS) develop invariably severe motor deterioration resulting in swallowing difficulties that may produce excessive drooling. Hypersalivation can cause discomfort due to hygienic problems and may complicate with oral and respiratory dysfunctions. The aim of this study is to evaluate the response to treatment with botulinum toxin (BTX) for hypersalivation and to identify possible benefits of saliva reduction on oral motor and respiratory disorders of patients with RS.

METHODS

Five consecutive patients with RS and hypersalivation were treated with incobotulinumtoxin A injected in salivary glands with ultrasound guidance. Severity of excessive drooling was assessed with the Thomas-Stonell and Greenberg Scale (TGSC) and the clinical impact of the treatment was evaluated using three selected items of RS Assessment Rating Scale (R.A.R.S.): eating habits, dyspnoea and bruxism. Scale rating was performed before BTX injection (T0), 4 (T1) and 12 (T2) weeks after.

RESULTS

Scores of TGSC and R.A.R.S. (for eating and bruxism) were reduced significantly after therapy at T1.

CONCLUSIONS

BTX treatment for sialorrhea in RS is effective in reducing saliva production and may also improve oral motor functions.

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.

Botulinum toxin injection and tear production

PURPOSE OF REVIEW

In 1980, botulinum toxin type A (BTX-A) was introduced for the treatment of strabismus and benign essential blepharospasm. Since then, a number of additional indications have been introduced, which continue to expand, providing less invasive solutions in managing different ophthalmic conditions.

RECENT FINDINGS

Successful trials of BTX-A injection into the lacrimal gland have been reported for the treatment of epiphora caused by primary lacrimal gland hyperlacrimation, functional tearing, gustatory tearing, and lacrimal outflow obstruction. This is achieved through blockage of the cholinergic receptors by BTX-A at the glandular level. Interestingly, BTX-A has also been found to be useful in treating patients with dry eyes by compromising the tear drainage from the eye through injection of BTX-A in the medial part of the lower eyelid. BTX-A may help provide effective relief for patients who have two different ophthalmic comorbidities such as benign essential blepharospasm and dry eye.

SUMMARY

Better understanding of the mechanism of BTX-A action in the treatment of the growing applications in ophthalmology helps provide relatively noninvasive solutions for patients. Full awareness of possible side effects of BTX-A and the optimal way to manage them is vital for the success of this treatment option.

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.

Botulinum Neurotoxins: Biology, Pharmacology, and Toxicology

The study of botulinum neurotoxins (BoNT) is rapidly progressing in many aspects. Novel BoNTs are being discovered owing to next generation sequencing, but their biologic and pharmacological properties remain largely unknown. The molecular structure of the large protein complexes that the toxin forms with accessory proteins, which are included in some BoNT type A1 and B1 pharmacological preparations, have been determined. By far the largest effort has been dedicated to the testing and validation of BoNTs as therapeutic agents in an ever increasing number of applications, including pain therapy. BoNT type A1 has been also exploited in a variety of cosmetic treatments, alone or in combination with other agents, and this specific market has reached the size of the one dedicated to the treatment of medical syndromes. The pharmacological properties and mode of action of BoNTs have shed light on general principles of neuronal transport and protein-protein interactions and are stimulating basic science studies. Moreover, the wide array of BoNTs discovered and to be discovered and the production of recombinant BoNTs endowed with specific properties suggest novel uses in therapeutics with increasing disease/symptom specifity. These recent developments are reviewed here to provide an updated picture of the biologic mechanism of action of BoNTs, of their increasing use in pharmacology and in cosmetics, and of their toxicology.

BoNT/AB hybrid maintains similar duration of paresis as BoNT/A wild-type in murine running wheel assay

The highly potent Botulinum neurotoxins (BoNT) are successful drugs to treat neuromuscular disorders. Efforts are being made to further reduce the injected BoNT dose and to lengthen the interval between treatments. Detailed knowledge of the BoNT structure-activity relationship (SAR) allows combining the best features of the different BoNT serotypes. Of all seven BoNT serotypes A-G, BoNT/A displays the highest potency despite low neuronal binding affinity, while BoNT/B exhibits much higher affinity. Recently, a new BoNT/AB hybrid (AABB) was constructed comprising the catalytic and translocation domain of BoNT/A and the 50kDa cell binding domain of BoNT/B. Here, we compared BoNT/A wild-type (AAAA) and AABB with regard to ex vivo potency and in vivo potency, efficacy and duration of action using the mouse phrenic nerve hemidiaphragm assay and the murine running wheel assay, respectively. The ex vivo potency of AABB was found to be 8.4-fold higher than that of AAAA. For the latter, two and 5 pg each of AAAA and AABB, respectively, were bilaterally injected into the calf muscles and mouse running wheel performance was automatically monitored during the following weeks to determine potency, efficacy and duration. Mice displayed a dose-dependent impairment of running performance. AABB showed potency, efficacy and duration equal to AAAA demonstrating successful exchange of the cell binding domain. AABB might combine the higher potency and longer duration of BoNT/A with the target specificity for the autonomic nervous system of BoNT/B. AABB might therefore constitute an improved treatment option for acetylcholine-mediated autonomic disorders such as hypersalivation or hyperhidrosis.