The History of Botulinum Toxins in Medicine: A Thousand Year Journey

Neurobiological mechanisms of botulinum neurotoxin-induced analgesia for neuropathic pain

Botulinum neurotoxins (BoNTs) are a family of neurotoxins produced by Clostridia and other bacteria that induce botulism. BoNTs are internalized into nerve terminals at the site of injection and cleave soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins to inhibit the vesicular release of neurotransmitters. BoNTs have been approved for multiple therapeutic applications, including the treatment of migraines. They have also shown efficacies for treating neuropathic pain, such as diabetic neuropathy, and postherpetic and trigeminal neuralgia. However, the mechanisms underlying BoNT-induced analgesia are not well understood. Peripherally administered BoNT is taken up by the nerve terminals and reduces the release of glutamate, calcitonin gene-related peptide, and substance P, which decreases neurogenic inflammation in the periphery. BoNT is retrogradely transported to sensory ganglia and central terminals in a microtubule-dependent manner. BoNTs decrease the expression of pronociceptive genes (ion channels or cytokines) from sensory ganglia and the release of neurotransmitters and neuropeptides from primary afferent central terminals, which likely leads to decreased central sensitization in the dorsal horn of the spinal cord or trigeminal nucleus. BoNT-induced analgesia is abolished after capsaicin-induced denervation of transient receptor potential vanilloid 1 (TRPV1)-expressing afferents or the knockout of substance P or the neurokinin-1 receptor. Although peripheral administration of BoNT leads to changes in the central nervous system (e.g., decreased phosphorylation of glutamate receptors in second-order neurons, reduced activation of microglia, contralateral localization, and cortical reorganization), whether such changes are secondary to changes in primary afferents or directly mediated by trans-synaptic, transcytotic, or the hematogenous transport of BoNT is controversial. To enhance their therapeutic potential, BoNTs engineered for specific targeting of nociceptive pathways have been developed to treat chronic pain. Further mechanistic studies on BoNT-induced analgesia can enhance the application of native or engineered BoNTs for neuropathic pain treatment with improved safety and efficacy.

Five decades of the use of botulinum toxin in ophthalmology

Botulinum toxin (BoNT) has been known for over 50 years. It has conquered many areas of medicine and has become indispensable in contemporary medicine. Now, BoNT is used to treat at least 26 conditions in six medical specialties. Although the use of BoNT began in strabology, it became the gold standard for many ophthalmologic pathologies. The present review of the literature focuses on the use of BoNT in ophthalmology and treatment of the following conditions: blepharospasm, facial hemispasm, facial palsy, spastic entropion, strabismus, endocrine orbitopathy, convergence spasm, and facial trauma. We conclude that nearly half a century of experience in utilizing BoNT in ophthalmology ensured a satisfactory level of effectiveness and safety for patients with many pathologies. Areas of future research include the application of BoNT in new selected indications, the development of the route of application without injections, and the development of long-acting BoNT forms for patients who require repeated long-term treatment.

A Phase III Clinical Study of the Efficacy and Safety of Botulinum Toxin Type A (MASPORT) with DYSPORT for the Treatment of Glabellar Lines

BACKGROUND

Botulinum toxin type A is a widely used treatment of facial wrinkles. The objective of this study was to compare the efficacy and safety of a new botulinum toxin type A (Masport [abobotulinum toxin A], MasoonDarou Co) with DYSPORT® for the treatment of glabellar lines.

METHODS

262 subjects with moderate-to-severe glabellar lines received either a fixed dose of 50 units of MASPORT® or DYSPORT® (Ipsen Company, England). Subjects were followed up at 14, 30, 60, 90 and 120 days after injection. Efficacy was assessed by investigator at maximum frown and rest and also by Subject Global Assessment of Change (SGA). The responders were defined as persons with +2 grade improvement from baseline for both investigator and patient assessment. The occurrence and duration of adverse effects were recorded up throughout the study.

RESULTS

According to the investigator evaluations, the responder rate at maximum frown were 94.5% for MASPORT and 95.6% for DYSPORT group on day 30 and at rest were 85.45% and 85.68% for MASPORT and DYSPORT group, respectively. According to the subject self-assessment, the proportion of responders in MASPORT group at day 30 was 95.28% versus 97.04% for DYSPORT group. No serious drug related adverse effect was recorded in either study groups, and the rates of adverse effects were similar for both groups.

CONCLUSION

Abobotulinum toxin A [MASPORT] is equally safe and effective as commercial product [DYSPORT] for the treatment of glabellar lines with the dose of 50 units, up to 120 days.

LEVEL OF EVIDENCE I

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Amelioration of trichotillomania with onabotulinumtoxinA for chronic migraine

We report a case of a woman in her 30s who struggled with a life-long history of trichotillomania (TTM; hair-pulling disorder), which was unsuccessfully treated with behavioural therapy and selective serotonin reuptake inhibitors. In addition to TTM, our patient had a history of chronic migraine which brought her to our clinic, and treatment with onabotulinumtoxinA (OBTA) was initiated per the Phase III REsearch Evaluating Migraine Prophylaxis Therapy protocol. After experiencing improvement with migraine symptoms, she began off-label treatment with OBTA for her TTM with 45 units being injected, 5 units per site, in diffuse regions of her scalp, primarily on the affected areas of TTM-induced alopecia. The patient reported marked improvement in her TTM signs and symptoms, which resulted in hair regrowth as early as the first follow-up visit 12 weeks post-treatment initiation. Treatment effects were maintained, and additional hair regrowth was observed at the 1-year post-treatment visit, which equated to four cycles of treatment.

OnabotulinumtoxinA in Migraine: A Review of the Literature and Factors Associated with Efficacy

The efficacy of onabotulinumtoxinA (OnaB-A) as a preventative treatment for chronic migraine, emerging fortuitously from clinical observation is now supported by class one evidence and over two decades of real-world clinical data. There is still limited ability to predict a clinically meaningful response to OnaB-A for individual patients, however. This review summarises briefly the proposed mechanism of OnaB-A in chronic migraine, the literature of predictors of clinical response, and recent developments in the field.

Efficacy of botulinum toxin injection in exotropia treatment

PURPOSE:

Botulinum toxin (Botox) therapy is a well-known option for strabismus management and is often used in managing esotropia. Exotropia is also a common type of strabismus; however, the effectiveness of Botox in improving exotropia is still ambiguous. In this study, we report our experience in using Botox to manage the various types of exotropia.

METHODS:

A retrospective cohort study was conducted at King Khaled Eye Specialist Hospital Riyadh, Saudi Arabia. Medical records of patients with exotropia who received Botox from 2014 to March 2020 were reviewed. The main success indicator was a remaining angle of less than 10 prism diopters (PD).

RESULTS:

A total of 97 cases were reviewed, with 57 (58.8%) males and 40 (41.2%) females. The age ranged from 2 months to 40 years. The most prevalent diagnosis was sensory exotropia. Overall, 28 patients (28.9 %) and 49 patients (50.5%) achieved an angle of deviation within 10 PD and within 20 PD, respectively. Female patients had a better response to Botox than males, with 32.5% of them achieving an angle of deviation within 10 PD and 60% achieving an angle of deviation within 20 PD. We found that the change in the angle of deviation increased as the Botox dose was increased.

CONCLUSION:

Botox represents a possible safe alternative to surgery in the management of some exotropia types. The success rate differs by type, with basic exotropia scoring the highest. The presence of poor vision and amblyopia leads to a significantly lower success rate.

Engineering Botulinum Neurotoxins for Enhanced Therapeutic Applications and Vaccine Development

Botulinum neurotoxins (BoNTs) show increasing therapeutic applications ranging from treatment of locally paralyzed muscles to cosmetic benefits. At first, in the 1970s, BoNT was used for the treatment of strabismus, however, nowadays, BoNT has multiple medical applications including the treatment of muscle hyperactivity such as strabismus, dystonia, movement disorders, hemifacial spasm, essential tremor, tics, cervical dystonia, cerebral palsy, as well as secretory disorders (hyperhidrosis, sialorrhea) and pain syndromes such as chronic migraine. This review summarizes current knowledge related to engineering of botulinum toxins, with particular emphasis on their potential therapeutic applications for pain management and for retargeting to non-neuronal tissues. Advances in molecular biology have resulted in generating modified BoNTs with the potential to act in a variety of disorders, however, in addition to the modifications of well characterized toxinotypes, the diversity of the wild type BoNT toxinotypes or subtypes, provides the basis for innovative BoNT-based therapeutics and research tools. This expanding BoNT superfamily forms the foundation for new toxins candidates in a wider range of therapeutic options.