Alternative Clinical Indications of Botulinum Toxin

Industrial Production and Therapeutic Application of Botulinum Neurotoxin: The Role of C. botulinum Type A

Botulinum neurotoxin has remarkably transitioned from a food safety hazard and biological warfare to an effective therapeutic drug. Currently, botulinum neurotoxins have seven serotypes (BoNT/A-G) in the form of protein complexes produced by Clostridium, a gram-positive and sporeforming bacteria. The conversion of toxins into useful drug substances of choice using the biotechnological process is tremendously increasing. Recent studies have shown that Botulinum neurotoxin-A (BoNT/A) has different biological activities and potencies in experimental and clinical conditions. They also indicate that the manufacturing process influences the potency and efficacy of BoNT/A drugs. Thus, this review focuses on the following criteria: detailed Fed-batch operation that includes the upstream and downstream processing of BoNT/A, the underlying mechanism behind the neurotoxic effect, and commercially available FDA-approved BoNT/A products and their therapeutic uses. Still, some research gaps exist in the mechanism for the treatment of psychiatric disorders.

Use of LetibotulinumtoxinA for Aesthetic Treatment of Asians: A Consensus

Treatment of wrinkles and dynamic lines with botulinum toxin has been a routine practice for years in aesthetic clinical settings. The effective treatment of wrinkles requires a comprehensive understanding of facial expression muscles and their interactions, the mechanism of action of botulinum toxin, and individual patient preferences. The dose adjustment practice and injection technique of physicians are affected by cultural differences; most Asian patients prefer natural-looking results. This article aims to present an expert consensus on the injection sites, doses, and levels of botulinum toxin for various indications in Asians, with the hope of providing guidance to some clinicians. This consensus paper reviews LetibotulinumtoxinA for patient evaluation, dosage, and delivery techniques in Asians from the time LetibotulinumtoxinA was approved up to December 2022. Panelists proposed individualized treatment plans for botulinum toxin type A (BTxA) treatments in 3 areas-wrinkle removal, contour adjustment, and face lifting-for Asians based on their extensive experience and knowledge of facial anatomy. When using a different BTxA, clinicians should start with a conservative dose and carefully individualize the treatment for each patient, and adjust it according to feedback to obtain a higher satisfaction level.

LEVEL OF EVIDENCE: 5

A large travel-associated outbreak of iatrogenic botulism in four European countries following intragastric botulinum neurotoxin injections for weight reduction, Türkiye, February to March 2023

In March 2023, 34 associated cases of iatrogenic botulism were detected in Germany (30 cases), Switzerland (two cases), Austria (one case), and France (one case). An alert was rapidly disseminated via European Union networks and communication platforms (Food- and Waterborne Diseases and Zoonoses Network, EpiPulse, Early Warning and Response System) and the International Health Regulation mechanism; the outbreak was investigated in a European collaboration. We traced sources of the botulism outbreak to treatment of weight loss in Türkiye, involving intragastric injections of botulinum neurotoxin. Cases were traced using a list of patients who had received this treatment. Laboratory investigations of the first 12 German cases confirmed nine cases. The application of innovative and highly sensitive endopeptidase assays was necessary to detect minute traces of botulinum neurotoxin in patient sera. The botulism notification requirement for physicians was essential to detect this outbreak in Germany. The surveillance case definition of botulism should be revisited and inclusion of cases of iatrogenic botulism should be considered as these cases might lack standard laboratory confirmation yet warrant public health action. Any potential risks associated with the use of botulinum neurotoxins in medical procedures need to be carefully balanced with the expected benefits of the procedure.

Cosmetic Treatment Using Botulinum Toxin in the Oral and Maxillofacial Area: A Narrative Review of Esthetic Techniques

Botulinum toxin (BoNT) is an anaerobic rod-shaped-neurotoxin produced by Clostridium botulinum, that has both therapeutic and lethal applications. BoNT injection is the most popular cosmetic procedure worldwide with various applications. Patients with dynamic wrinkles in areas such as the glabella, forehead, peri-orbital lines, nasal rhytides, and perioral rhytides are indicated. Excessive contraction of muscles or hyperactivity of specific muscles such as bulky masseters, cobble stone chins, gummy smiles, asymmetric smiles, and depressed mouth corners can achieve esthetic results by targeting the precise muscles. Patients with hypertrophic submandibular glands and parotid glands can also benefit esthetically. There are several FDA-approved BoNTs (obabotuli-numtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, letibotulinumtoxinA, prabotulinumtox-inA, daxibotulinumtoxinA, rimbotulinumtoxinB) and novel BoNTs on the market. This paper is a narrative review of the consensus statements of expert practitioners and various literature on the injection points and techniques, highlighting both the Asian and Caucasian population separately. This paper can serve as a practical illustrative guide and reference for optimal, safe injection areas and effective doses for application of BoNT in the face and oral and maxillofacial area. The history of BoNT indications, contraindications, and complications, and the merits of ultrasonography (US)-assisted injections are also discussed.

Concentration-Dependent Inhibition of Hypertrophic Scar Formation by Botulinum Toxin Type A in a Rabbit Ear Model

BACKGROUND

Hypertrophic scar (HS), as a disappointing result of wound healing, adversely affects the patient, both physically and psychologically. Botulinum toxin type A (BTXA) has been revealed to prevent and improve HS. We conducted this study to assess the effect of different BTXA concentrations on inhibiting HS in a rabbit ear model.

METHODS

Eight healthy New Zealand long-eared rabbits were included in the experiment for modeling. Four wounds of 1 cm in diameter were created on both ears, which separately received an injection of a given BTXA concentration immediately after surgery. On postoperative days 40, scar tissue was obtained and subjected to hematoxylin and eosin (HE) staining for the hypertrophic index (HI) and immunohistochemical staining for CD31, Ki67, and transforming growth factor-beta 1 (TGF-β1) expression. The HI was assessed for scar proliferation, and CD31 and Ki67 expression were used to assess the effect of BTXA on angiogenesis and fibroblast proliferation, respectively.

RESULTS

All rabbits healed well without infection or mortality. From the HE staining, the HI showed a significant decrease with increasing BTXA concentration (p < 0.05). BTXA also inhibited angiogenesis and TGF-β1 expression in a concentration-dependent manner, with significant differences between the groups (p < 0.05). BTXA inhibited fibroblast proliferation with increasing BTXA concentration. However, there was no significant difference between the 0.5 U/0.1 ml and 0 U/0.1 ml groups (p > 0.05).

CONCLUSION

Immediate postoperative BTXA injection inhibited angiogenesis, fibroblast proliferation, and TGF-β1 expression in a concentration-dependent manner, thus suppressing HS formation in rabbit ears.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/journal/00266 .

How Does Botulinum Toxin Inhibit Itch?

Two decades after reports of the anti-pruritic effects of botulinum neurotoxins (BoNTs), there is still no approved product for the anti-itch indication of BoNTs, and most clinical case reports still focus on the off-label use of BoNTs for various itchy conditions. Few randomized clinical trials have been conducted with controversial results, and the beneficial effects of BoNTs against itch are mainly based on case studies and case series. These studies are valuable in presenting the potential application of BoNTs in chronic pruritic conditions, but due to the nature of these studies, they are categorized as providing lower levels of evidence or lower grades of recommendation. To obtain approval for the anti-pruritic indication of BoNTs, higher levels of evidence are required, which can be achieved through conducting large-scale and well-designed studies with proper control groups and established careful and reliable primary and secondary outcomes. In addition to clinical evidence, presenting the mechanism-based antipruritic action of BoNTs can potentially strengthen, accelerate, and facilitate the current efforts towards further investments in accelerating the field towards the potential approval of BoNTs for itchy conditions. This review, therefore, aimed to provide the state-of-the-art mechanisms underlying the anti-itch effect of BoNTs from basic studies that resemble various clinical conditions with itch as a hallmark. Evidence of the neuronal, glial, and immune modulatory actions of BoNTs in reducing the transmission of itch are presented, and future potential directions are outlined.

Botulinum Toxin Type A for the Treatment of Skin Ulcers: A Review Article

The normal biological wound healing process consists of three precisely and highly programmed phases that require optimal conditions including internal and external factors. Any negative factors that disrupt the sequence or time frame of the healing mechanism can result in a non-healing wound or chronic ulcers. Botulinum neurotoxin A (BoNT-A) which is generally known as anti-contraction of muscles has been reported as a successful treatment in various types of chronic ulcers. The aim of this study is to review the outcome of treatment with BoNT-A for chronic skin ulcers. The results demonstrated some positive effects of BoNT-A on chronic ulcers. Ischemic ulcers secondary to Raynaud’s phenomenon seem to be the most promising type of ulcers that have benefited from BoNT-A. The rationale behind using BoNT-A to fasten the wound healing process is also discussed. Further clinical trial studies should be conducted to affirm the efficacy of wound healing using BoNT-A administration.

Dynamic muscle paralytic effects of a novel botulinum toxin A free of neurotoxin-associated proteins

Structurally, botulinum toxin type A (BTX‐A) is composed of neurotoxin and nontoxic complexing proteins (CPs), and the neurotoxin has the function of blocking acetylcholine release from the neuromuscular junction and therefore paralyzing muscles. Nowadays, a novel botulinum toxin A free of CPs (chinbotulinumtoxin A, A/Chin) is produced, and the present study comprehensively evaluated the dynamic paralytic effect of A/Chin on the gastrocnemius muscle of rats. Different doses (0.01, 0.1, 0.5, 1, 2, and 4 U) of A/Chin and other BTX‐As with and without CPs were administered to the gastrocnemius muscles of rats and muscle strength was measured and compared at different postinjection timepoints (from day 0 to 84). With the dose increased, time‐to‐peak paralytic effect of other BTX‐As varied from day 3 to day 14, while A/Chin groups showed rapid and steady time to peak on day 3. At the lowest dose of 0.01 U, A/Chin showed significantly better peak paralytic effect than the others on day 3. When the dose increased to 0.5 U and more, A/Chin group also showed significant paralytic effect when the paralytic effect of other BTX‐As was worn off. Moreover, the paralytic effect of A/Chin was confirmed as muscle atrophy while hematoxylin–eosin staining was performed. In conclusion, compared with other BTX‐As, A/Chin showed rapid and steady time‐to‐peak paralytic effect and long‐term paralytic efficacy at the same dose level. And it might lay a solid foundation for further wide application of A/Chin in both clinical and cosmetic areas.

Botulinum Toxin Versus Placebo: A Meta-Analysis of Treatment and Quality-of-life Outcomes for Hyperhidrosis

AIMS

This study aims at assessing the treatment effect, disease severity and quality-of-life outcomes of botulinum toxin (BTX) injections for focal hyperhidrosis.

METHODS

We included randomized controlled trials of BTX injections compared with placebo for patients with primary or secondary focal hyperhidrosis. PubMed, Embase and the Cochrane Library were searched to August 2020. Gravimetric sweat rate reduction, disease severity measured by Hyperhidrosis Disease Severity Scale and quality-of-life assessment measured by Dermatology Life Quality Index were the outcomes of interest. Cochrane risk-of-bias tools were employed for quality assessment of given randomized controlled trials.

RESULTS

Eight studies met our inclusion criteria (n=937). Overall, risk bias was mixed and mostly moderate. BTX injections showed reduced risk in comparison with placebo for the gravimetric quantitative sweat reduction of > 50 % from baseline (risk difference: 0.63, 95% CI 0.51 to 0.74). Additionally, improvements were seen for disease severity and quality-of-life assessments evaluated by Hyperhidrosis Disease Severity Score reduction of ≥ 2 points (risk difference: 0.56, 95% CI 0.42 to 0.69) and mean change in Dermatology Life Quality Index (mean difference: - 5.55, 95% CI - 7.11 to - 3.98). The acquired data were insufficient to assess for long-term outcomes and limited to an eight-week follow-up period.

CONCLUSIONS

In focal axillary hyperhidrosis, BTX significantly reduces sweat production and yields superior outcomes in assessments of disease severity and quality-of-life. However, the quality-of-evidence is overall moderate and included studies account for short-term trial periods only. Further studies assessing BTX in comparison with first-line treatments for hyperhidrosis are warranted.

LEVEL OF EVIDENCE III

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

Use of Botulinum Toxin in Treating Rosacea: A Systematic Review

Background

Rosacea is a chronic skin disorder characterized by erythema, flushing, telangiectasia, papules and pustules, phymatous changes, and ocular involvement. The aim of this study was to examine all published research articles in which botulinum toxin was used to treat rosacea and to evaluate the efficacy and safety of this treatment.

Methods

PubMed, Embase, Cochrane Library, and Web of Science database were used to identify articles eligible for systematic review on March 26, 2021. Prospective or retrospective studies which directly used botulinum toxin to treat rosacea were included and reviewed.

Results

Nine studies were included in this systematic review. Two were randomized controlled trials, graded as Level 2 for the quality of evidence. The total number of participants was 130, and the number of participants in each study ranged from 1 to 25. The improvement was observed in all studies in signs and symptoms compared with baseline. Adverse events were transitory and self-limited.

Conclusion

Botulinum toxin could have overall satisfying efficacy and safety in the treatment of rosacea, though limited by small sample size, imperfect study design, and short follow-up visits.