Severe Nervous System Complications After Botulinum Type A Therapy: Three Case Reports With Reviews of FDA-Reported Nervous System Adverse Effects

Tirbanibulin (KX2-391) analog KX2-361 inhibits botulinum neurotoxin serotype A mediated SNAP-25 cleavage in pre- and post-intoxication models in cells

Botulinum neurotoxins (BoNT) inhibit neuroexocytosis, leading to the potentially lethal disease botulism. BoNT serotype A is responsible for most human botulism cases, and there are no approved therapeutics to treat already intoxicated patients. A growing body of research has demonstrated that BoNT/A can escape into the central nervous system, and therefore, identification of BoNT/A inhibitors that can penetrate BBB and neutralize the toxin within intoxicated neurons would be important. We previously identified an FDA-approved, orally bioavailable compound, KX2-391 (Tirbanibulin) that inhibits BoNT/A in motor neuron assays. Recently, a structural analog of KX2-391, KX2-361, has been shown to exhibit good oral bioavailability and cross BBB with high efficiency in mouse experiments. Therefore, in this work, we evaluated the inhibitory effects of KX2-361 against BoNT/A. Toward this goal, we first evaluated the compound for its effects on cell viability in PC12 cells, via MTT assay, and in mouse embryonic stem cell (mESC)-derived motor neurons, with imaging-based assays. Following, we tested KX2-361 in mESC-derived motor neurons intoxicated with BoNT/A holotoxin, and the compound exhibited activity against the toxin in both pre- and post-intoxication conditions. Excitingly, KX2-361 also inhibited BoNT/A enzymatic component (light chain; LC) in PC12 cells transfected with BoNT/A LC. Furthermore, our molecular docking analyses suggested that KX2-361 can directly bind to BoNT/A LC. Medicinal chemistry approaches to develop structural analogs of KX2-361 to increase its efficacy against BoNT/A may provide a critical lead compound with BBB penetration capacity for drug development efforts against BoNT/A intoxication.

Transient Worsening of Dysphagia and Dysarthria after Treatment with Botulinum Toxin in Patients with Acquired Brain Injury

Although botulinum toxin is widely considered an effective and safe treatment for a variety of neurological conditions (such as disabling spasticity), local or systemic adverse effects have often been reported. This study describes three cases of patients with severe acquired brain injury who were receiving speech therapy for recovering dysphagia and dysarthria but showed worsening of these symptoms after receiving BoNT treatment for motor spasticity. To increase clinicians' knowledge of these adverse effects, we present our cases and explore their significance to avoid major complications such as aspiration pneumonia.

Botulinum Toxin Type A injections for pediatric spasticity: Keeping our patients informed and practices safe

Serious adverse events (serious AEs) following the therapeutic use of Botulinum Toxin Type A (BoNT-A) are infrequent. Children with pediatric spasticity often have comorbidities that can cloud causation around an adverse event (AE). If a serious AE occurs, clear documentation of information sharing and informed consent as well as the provider-patient relationship are critical to minimizing litigation risks. Reviewing the litigation that has occurred following BoNT-A for pediatric spasticity can offer insight into how providers' perspectives regarding this intervention may differ from those of the public who might serve as jurists. This article offers suggestions for content sharing during the consent process to optimize patient understanding about potential adverse events.

The whole truth about botulinum toxin - a review

Treatment with botulinum toxin is widely viewed as safe, effective and largely devoid of serious side effects. There are two classes of Botox-related adverse events – transient and benign events, and potentially serious events. The aim of this study was to provide an overview of Botox-related side effects and advise potential management and preventive strategies. Benign side effects are well-localized, reversible and self-limited complications which develop within a few days of the injection, and they usually disappear without any treatment. The aesthetic and functional adverse effects are associated with different muscle responses to botulinum toxin or with misplacement of botulinum toxin. The serious events are sequelae due to the systemic spread of toxin leading to botulism.

Diffusion, spread, and migration of botulinum toxin

Botulinum toxin (BoNT) is an acetylcholine release inhibitor and a neuromuscular blocking agent used for the treatment of a variety of neurologic and medical conditions. The efficacy and safety of BoNT depends on accurate selection and identification of intended targets but also may be determined by other factors, including physical spread of the molecule from the injection site, passive diffusion, and migration to distal sites via axonal or hematogenous transport. The passive kinetic dispersion of the toxin away from the injection site in a gradient-dependent manner may also play a role in toxin spread. In addition to unique properties of the various BoNT products, volume and dilution may also influence local and systemic distribution of BoNT. Most of the local and remote complications of BoNT injections are thought to be due to unwanted spread or diffusion of the toxin's biologic activity into adjacent and distal muscles. Despite widespread therapeutic and cosmetic use of BoNT over more than three decades, there is a remarkable paucity of published data on the mechanisms of distribution and its effects on clinical outcomes. The primary aim of this article is to critically review the available experimental and clinical literature and place it in the practical context.