OnabotulinumtoxinA effects on trigeminal nociceptors.

BACKGROUND: OnabotulinumtoxinA (onabotA) is approved globally for prevention of chronic migraine; however, the classical mechanism of action of onabotA in motor and autonomic neurons cannot fully explain the effectiveness of onabotulinumtoxinA in this sensory neurological disease. We sought to explore the direct effects of onabotulinumtoxinA on mouse trigeminal ganglion sensory neurons using an inflammatory soup-based model of sensitization. METHODS: Primary cultured trigeminal ganglion neurons were pre-treated with inflammatory soup, then treated with onabotulinumtoxinA (2.75 pM). Treated neurons were used to examine transient receptor potential vanilloid subtype 1 and transient receptor potential ankyrin 1 cell-surface expression, calcium influx, and neuropeptide release. RESULTS: We found that onabotulinumtoxinA cleaved synaptosomal-associated protein-25 kDa in cultured trigeminal ganglion neurons; synaptosomal-associated protein-25 kDa cleavage was enhanced by inflammatory soup pre-treatment, suggesting greater uptake of toxin under sensitized conditions. OnabotulinumtoxinA also prevented inflammatory soup-mediated increases in TRPV1 and TRPA1 cell-surface expression, without significantly altering TRPV1 or TRPA1 protein expression in unsensitized conditions. We observed similar inhibitory effects of onabotulinumtoxinA on TRP-mediated calcium influx and TRPV1- and TRPA1-mediated release of calcitonin gene-related peptide and prostaglandin 2 under sensitized, but not unsensitized control, conditions. CONCLUSIONS: Our data deepen the understanding of the sensory mechanism of action of onabotulinumtoxinA and support the notion that, once endocytosed, the cytosolic light chain of onabotulinumtoxinA cleaves synaptosomal-associated protein-25 kDa to prevent soluble N-ethylmaleimide-sensitive factor attachment protein receptor-mediated processes more generally in motor, autonomic, and sensory neurons.

OnabotulinumtoxinA alters inflammatory gene expression and immune cells in chronic headache patients.

Occipital headache, the perception of pain in the back of the head, is commonly described by patients diagnosed with migraine, tension-type headache, and occipital neuralgia. The greater and lesser occipital nerves play central role in the pathophysiology of occipital headache. In the clinical setup, such headaches are often treated with onabotulinumtoxinA, a neurotoxin capable of disrupting ability of nociceptors to get activated and/or release proinflammatory neuropeptides. Attempting to understand better onabotulinumtoxinA mechanism of action in reducing headache frequency, we sought to determine its effects on expression of inflammatory genes in injected occipital tissues. To achieve this goal, we injected 40 units of onabotulinumtoxinA into four muscle groups (occipitalis, splenius capitis, semispinalis capitis, and trapezius muscles-all located on one side of the occiput) of patients with chronic bilateral occipital headache scheduled for occipital nerve decompression surgery 1 month later. At the time of surgery, we collected discarded muscle, fascia and periosteum tissues from respective locations on both sides of the neck and occiput and performed targeted transcriptome analyses to determine expression level of inflammatory genes in onabotulinumtoxinA-injected and onabotulinumA-uninjected tissues. We found that (i) onabotulinumtoxinA alters expression of inflammatory genes largely in periosteum, minimally in muscle and not at all in fascia; (ii) expression of inflammatory genes in uninjected periosteum and muscle is significantly higher in historical onabotulinumA responders than historical non-responders; (iii) in historical responders' periosteum, onabotulinumA decreases expression of nearly all significantly altered genes, gene sets that define well recognized inflammatory pathways (e.g. pathways involved in adaptive/innate immune response, lymphocyte activation, and cytokine, chemokine, NF-kB, TNF and interferon signalling), and abundance of 12 different immune cell classes (e.g. neutrophils, macrophages, cytotoxic T-, NK-, Th1-, B- and dendritic-cells), whereas in historical non-responders it increases gene expression but to a level that is nearly identical to the level observed in the uninjected periosteum and muscle of historical responders; and surprisingly (iv) that the anti-inflammatory effects of onabotulinumA are far less apparent in muscles and absent in fascia. These findings suggest that in historical responders' periosteum-but not muscle or fascia-inflammation contributes to the pathophysiology of occipital headache, and that further consideration should be given to the possibility that onabotulinumA mechanism of action in migraine prevention could also be achieved through its ability to reduce pre-existing inflammation, likely through localized interaction that lead to reduction in abundance of immune cells in the calvarial periosteum.

Design and Rationale of a Phase 2 Study of NeurOtoxin (Botulinum Toxin Type A) for the PreVention of Post-Operative Atrial Fibrillation - The NOVA Study.

BACKGROUND: Post-operative AF (POAF) is the most common complication following cardiac surgery, occurring in 30% to 60% of patients undergoing bypass and/or valve surgery. POAF is associated with longer intensive care unit/hospital stays, increased healthcare utilization, and increased morbidity and mortality. Injection of botulinum toxin type A into the epicardial fat pads resulted in reduction of AF in animal models, and in two clinical studies of cardiac surgery patients, without new safety observations. METHODS: The objective of NOVA is to assess the use of AGN-151607 (botulinum toxin type A) for prevention of POAF in cardiac surgery patients. This randomized, multi-site, placebo-controlled trial will study one-time injections of AGN-151607 125 U (25 U / fat pad) and 250 U (50 U / fat pad) or placebo during cardiac surgery in ∼330 participants. Primary endpoint: % of patients with continuous AF ≥ 30 s. Secondary endpoints include several measures of AF frequency, duration, and burden. Additional endpoints include clinically important tachycardia during AF, time to AF termination, and healthcare utilization. Primary and secondary efficacy endpoints will be assessed using continuous ECG monitoring for 30 days following surgery. All patients will be followed for up to 1 year for safety. CONCLUSIONS: The NOVA Study will test the hypothesis that injections of AGN-151607 will reduce the incidence of POAF and associated resource utilization. If demonstrated to be safe and effective, the availability of a one-time therapy for the prevention of POAF would represent an important treatment option for patients undergoing cardiac surgery.

Atogepant - an orally-administered CGRP antagonist - attenuates activation of meningeal nociceptors by CSD.

BACKGROUND: This study investigated the mechanism of action of atogepant, a small-molecule CGRP receptor antagonist recently approved for the preventive treatment of episodic migraine, by assessing its effect on activation of mechanosensitive C- and Aδ-meningeal nociceptors following cortical spreading depression. METHODS: Single-unit recordings of trigeminal ganglion neurons (32 Aδ and 20 C-fibers) innervating the dura was used to document effects of orally administered atogepant (5 mg/kg) or vehicle on cortical spreading depression-induced activation in anesthetized male rats. RESULTS: Bayesian analysis of time effects found that atogepant did not completely prevent the activation of nociceptors at the tested dose, but it significantly reduced response amplitude and probability of response in both the C- and the Aδ-fibers at different time intervals following cortical spreading depression induction. For C-fibers, the reduction in responses was significant in the early phase (first hour), but not delayed phase of activation, whereas in Aδ-fibers, significant reduction in activation was apparent in the delayed phase (second and third hours) but not early phase of activation. CONCLUSIONS: These findings identify differences between the actions of atogepant, a small molecule CGRP antagonist (partially inhibiting both Aδ and C-fibers) and those found previously for fremanezumab, a CGRP-targeted antibody (inhibiting Aδ fibers only) and onabotulinumtoxinA (inhibiting C-fibers only)- suggesting that these agents differ in their mechanisms for the preventive treatment of migraine.

Preclinical assessment of onabotulinumtoxinA for the treatment of mild traumatic brain injury-related acute and persistent post-traumatic headache.

OBJECTIVE: Investigation of onabotulinumtoxinA in a murine model of acute and persistent post-traumatic headache. METHODS: Mild traumatic brain injury was induced with a weight drop method. Periorbital and hindpaw cutaneous allodynia were measured for 14 days. Mice were then exposed to bright light stress and allodynia was reassessed. OnabotulinumtoxinA (0.5 U) was injected subcutaneously over the cranial sutures at different post-injury time points. RESULTS: After milt traumatic brain injury, mice exhibited periorbital and hindpaw allodynia that lasted for approximately 14 days. Allodynia could be reinstated on days 14-67 by exposure to stress only in previously injured mice. OnabotulinumtoxinA administration at 2 h after mild traumatic brain injury fully blocked both transient acute and stress-induced allodynia up to day 67. When administered 72 h post-mild traumatic brain injury, onabotulinumtoxinA reversed acute allodynia, but only partially prevented stress-induced allodynia. OnabotulinumtoxinA administration at day 12, when initial allodynia was largely resolved, produced incomplete and transient prevention of stress-induced allodynia. The degree of acute allodynia correlated positively with subsequent stress-induced allodynia. CONCLUSION: Mild traumatic brain injury induced transient headache-like pain followed by long lasting sensitization and persistent vulnerability to a normally innocuous stress stimulus, respectively modeling acute and persistent post-traumatic headache.. Administration of onabotulinumtoxinA following the resolution of acute post-traumatic headache diminished persistent post-traumatic headache but the effects were transient, suggesting that underlying persistent mild traumatic brain injury-induced maladaptations were not reversed. In contrast, early onabotulinumtoxinA administration fully blocked both acute post-traumatic headache as well as the transition to persistent post-traumatic headache suggesting prevention of neural adaptations that promote vulnerability to headache-like pain. Additionally, the degree of acute post-traumatic headache was predictive of risk of persistent post-traumatic headache.

Safety, Pharmacodynamic Response, and Treatment Satisfaction With OnabotulinumtoxinA 40 U, 60 U, and 80 U in Subjects With Moderate to Severe Dynamic Glabellar Lines.

BACKGROUND: OnabotulinumtoxinA 20 U reduces glabellar line (GL) severity at maximum frown for approximately 3 to 4 months. Small studies have suggested that >20-U doses may increase the efficacy and duration of response for GLs. OBJECTIVES: The aim of this study was to evaluate safety, pharmacodynamic response, and treatment satisfaction with onabotulinumtoxinA doses ≥20 U for GLs. METHODS: This 48-week, double-blind study compared 40, 60, and 80 U onabotulinumtoxinA vs 20 U and placebo in women with moderate or severe dynamic GLs on the Allergan Facial Wrinkle Scale. The following parameters were evaluated: the percentage of subjects with investigator-assessed ≥1-grade Facial Wrinkle Scale improvement from baseline at maximum frown (responders) at Week 24; the estimated median duration of response; the proportion of mostly/very satisfied responders on the Facial Line Satisfaction Questionnaire follow-up Items 1 to 5; and treatment-emergent adverse events. RESULTS: The modified intent-to-treat population (N = 226) had a mean age of 48.0 years, with similar baseline GL severity between treatment groups. Week 24 responder rates were 0% for placebo and 16.0%, 32.0%, 30.6%, and 38.5% for onabotulinumtoxinA 20, 40, 60, and 80 U, with significant (P < 0.05) differences for 40 and 80 U vs 20 U. Median duration of response was longer with all higher doses vs 20 U (≥24.0 vs 19.7 weeks; P < 0.05 vs 20 U at Week 24). Facial Line Satisfaction Questionnaire results indicated high subject satisfaction. The incidence and severity of treatment-emergent adverse events did not exhibit a dose-response effect. CONCLUSIONS: GL treatment with onabotulinumtoxinA doses >20 U demonstrated longer duration of response and higher patient-reported satisfaction vs the on-label 20-U dose with no apparent impact on safety variables.

Combined onabotulinumtoxinA/atogepant treatment blocks activation/sensitization of high-threshold and wide-dynamic range neurons.

BACKGROUND: OnabotulinumtoxinA and agents that block calcitonin gene‒receptor peptide action have both been found to have anti-migraine effects, but they inhibit different populations of meningeal nociceptors. We therefore tested the effects of combined treatment with onabotulinumtoxinA and the calcitonin gene‒receptor peptide antagonist atogepant on activation/sensitization of trigeminovascular neurons by cortical spreading depression. MATERIAL AND METHODS: Single-unit recordings were obtained of high-threshold and wide-dynamic-range neurons in the spinal trigeminal nucleus, and cortical spreading depression was then induced in anesthetized rats that had received scalp injections of onabotulinumtoxinA 7 days earlier and intravenous atogepant infusion 1 h earlier. The control group received scalp saline injections and intravenous vehicle infusion. RESULTS: OnabotulinumtoxinA/atogepant pretreatment prevented cortical spreading depression-induced activation and sensitization in both populations (control: Activation in 80% of high-threshold and 70% of wide-dynamic-range neurons, sensitization in 80% of high-threshold and 60% of wide-dynamic-range neurons; treatment: activation in 10% of high-threshold and 0% of wide-dynamic-range neurons, sensitization in 0% of high-threshold and 5% of wide-dynamic-range neurons). DISCUSSION: We propose that the robust inhibition of high-threshold and wide-dynamic-range neurons by the combination treatment was achieved through dual blockade of the Aδ and C classes of meningeal nociceptors. Combination therapy that inhibits meningeal C-fibers and prevents calcitonin gene‒receptor peptide from activating its receptors on Aδ-meningeal nociceptors may be more effective than a monotherapy in reducing migraine days per month in patients with chronic migraine.

Novel Native and Engineered Botulinum Neurotoxins.

Botulinum neurotoxins (BoNTs), produced by Clostridia and other bacteria, are the most potent toxins known. Their cleavage of the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins in neurons prevents the release of neurotransmitters, thus resulting in the muscle paralysis that is characteristic of botulism. This mechanism of action has been exploited for a variety of therapeutic and cosmetic applications of BoNTs. This chapter provides an overview of the native BoNTs, including the classical serotypes and their clinical use, mosaic BoNTs, and novel BoNTs that have been recently identified in clostridial and non-clostridial strains. In addition, the modular structure of native BoNTs, which are composed of a light chain and a heavy chain, is amenable to a multitude of novel fusions and mutations using molecular biology techniques. These novel recombinant BoNTs have been used or are being developed to further characterize the biology of toxins, to assist in vaccine production, to serve as delivery vehicles to neurons, and to be utilized as novel therapeutics for both neuronal and non-neuronal cells.

Mechanism of Action of OnabotulinumtoxinA in Chronic Migraine: A Narrative Review.

OBJECTIVE: To review the literature on the mechanism of action of onabotulinumtoxinA in chronic migraine. BACKGROUND: OnabotulinumtoxinA is a chronic migraine preventive treatment that significantly reduces headache frequency. The traditional mechanism described for onabotulinumtoxinA - reducing muscle contractions - is insufficient to explain its efficacy in migraine, which is primarily a sensory neurological disease. METHODS: A narrative literature review on the mechanism of action of onabotulinumtoxinA in chronic migraine. RESULTS: Following injection into tissues, onabotulinumtoxinA inhibits soluble N-ethylmaleimide-sensitive fusion attachment protein receptor (SNARE)-mediated vesicle trafficking by cleaving one of its essential proteins, soluble N-ethylmaleimide-sensitive fusion attachment protein (SNAP-25), which occurs in both motor and sensory nerves. OnabotulinumtoxinA inhibits regulated exocytosis of motor and sensory neurochemicals and proteins, as well as membrane insertion of peripheral receptors that convey pain from the periphery to the brain, because both processes are SNARE dependent. OnabotulinumtoxinA can decrease exocytosis of pro-inflammatory and excitatory neurotransmitters and neuropeptides such as substance P, calcitonin gene-related peptide, and glutamate from primary afferent fibers that transmit nociceptive pain and participate in the development of peripheral and central sensitization. OnabotulinumtoxinA also decreases the insertion of pain-sensitive ion channels such as transient receptor potential cation channel subfamily V member 1 (TRPV1) into the membranes of nociceptive neurons; this is likely enhanced in the sensitized neuron. For chronic migraine prevention, onabotulinumtoxinA is injected into 31-39 sites in 7 muscles of the head and neck. Sensory nerve endings of neurons whose cell bodies are located in trigeminal and cervical ganglia are distributed throughout the injected muscles, and are overactive in people with migraine. Through inhibition of these sensory nerve endings, onabotulinumtoxinA reduces the number of pain signals that reach the brain and consequently prevents activation and sensitization of central neurons postulated to be involved in migraine chronification. CONCLUSION: OnabotulinumtoxinA likely acts via sensory mechanisms to treat chronic migraine.

A Randomized Trial to Evaluate OnabotulinumtoxinA for Prevention of Headaches in Adolescents With Chronic Migraine.

OBJECTIVE: As a post-approval commitment, this dose-ranging study was undertaken to evaluate efficacy and safety of onabotulinumtoxinA in adolescents. BACKGROUND: In adolescents, migraine is often undiagnosed or misdiagnosed and can present unique management challenges. OnabotulinumtoxinA was approved for prevention of chronic migraine (CM) in adults in 2010. METHODS: This multicenter, double-blind, parallel-group, randomized trial assessed a single treatment of onabotulinumtoxinA (155 U or 74 U) vs placebo (intramuscular saline) administered via the recommended fixed-dose fixed site paradigm in adolescents with CM aged 12 to <18 years. The primary efficacy measure was change in frequency of headache days from baseline at week 12; other measures included change in frequency of headache days at weeks 4 and 8 and change in frequency of severe headache days. Safety and tolerability were assessed. RESULTS: Of 125 randomized patients (onabotulinumtoxinA 155 U, n = 45; onabotulinumtoxinA 74 U, n = 43; placebo, n = 37), all were included in the primary efficacy analysis, and 115 (92.0%) completed the study. Lack of efficacy was the primary reason for discontinuing (n = 4; 3.2%); no patients discontinued because of adverse events. All treatments reduced frequency of headache days at week 12, with no significant differences between treatments. The mean (95% confidence interval) changes from baseline in the frequency of headache days during the 28-day period ending at week 12 (primary endpoint) were -6.3 (-8.5, -4.2), -6.4 (-8.8, -4.0), and -6.8 (-9.6, -4.1) days in the onabotulinumtoxinA 155 U, onabotulinumtoxinA 74 U, and placebo groups, respectively (P ≥ .474). All treatments reduced frequency of severe headache days and were well-tolerated; serious adverse events (n = 3) were considered unrelated to treatment and resolved without sequelae. The most commonly reported treatment-emergent adverse events were neck pain (n = 8), upper respiratory tract infection (n = 7), migraine, and nasopharyngitis (n = 5 each). CONCLUSION: Although this study did not meet its efficacy endpoints, onabotulinumtoxinA was well tolerated in this adolescent population. Given previous data demonstrating the benefits of onabotulinumtoxinA in adults with CM, additional studies with design modifications, including adequate statistical power, to assess the efficacy of multiple treatment cycles of onabotulinumtoxinA for CM prevention in adolescents may be informative.

Exploring the effects of extracranial injections of botulinum toxin type A on prolonged intracranial meningeal nociceptors responses to cortical spreading depression in female rats.

BACKGROUND: Botulinum neurotoxin type A, an FDA-approved prophylactic drug for chronic migraine, is thought to achieve its therapeutic effect through blocking activation of unmyelinated meningeal nociceptors and their downstream communications with myelinated nociceptors and potentially the vasculature and immune cells. Prior investigations to determine botulinum neurotoxin type A effects on meningeal nociceptors were carried out in male rats and tested with stimuli that act outside the blood brain barrier. Here, we sought to explore the effects of extracranial injections of botulinum neurotoxin type A on activation of meningeal nociceptors by cortical spreading depression, an event which occurs inside the blood brain barrier, in female rats. MATERIAL AND METHODS: Using single-unit recording, we studied myelinated C- and unmyelinated Aδ-meningeal nociceptors' responses to cortical spreading depression 7-14 days after injection of botulinum neurotoxin type A or saline along calvarial sutures. RESULTS: In female rats, responses to cortical spreading depression were typically more prolonged and, in some cases, began at relatively longer latencies post-cortical spreading depression, than had been observed in previous studies in male rats. Extracranial administration of botulinum neurotoxin type A reduced significantly the prolonged firing of the meningeal nociceptors, in the combined sample of Aδ- and C-fiber, but not their response probability. DISCUSSION: The findings suggest that the mechanism of action by which botulinum neurotoxin type A prevents migraine differ from the one by which calcitonin gene-related peptide monoclonal antibodies prevent migraine and that even when the origin of migraine is central (i.e. in the cortex), a peripherally acting drug can intercept/prevent the headache.

Chronic Migraine: An Update on Physiology, Imaging, and the Mechanism of Action of Two Available Pharmacologic Therapies.

Several lines of research support the hypothesis that migraine is a spectrum of illness, with clinical symptoms that vary along a continuum from episodic migraine to chronic migraine. Physiologic changes may result in episodic migraine evolving into chronic migraine over months to years in susceptible individuals. With chronification, headache frequency increases, becoming more disabling and less responsive to therapy. Neurophysiologic and functional imaging research has reported that chronic migraine may be associated with severity-specific metabolic, functional, and structural abnormalities in the brainstem. Without longitudinal studies, it is unclear whether these changes may represent a continuum of individual progression and/or are reversible. Furthermore, chronic migraine is associated with larger impairments in cortical processing of sensory stimuli when compared with episodic migraine, possibly caused by more pronounced cortical hyperexcitability. Progressive changes in nociceptive thresholds and subsequent central sensitization due to recurrent migraine attacks in vulnerable individuals contribute to the chronic migraine state. This may result in changes to baseline neurologic function between headache attacks, evident in both electrophysiological and functional imaging research. Patients experiencing migraine chronification may report increased non-headache pain, fatigue, psychiatric disorders (eg, depression, anxiety), gastrointestinal complaints, and other somatic conditions associated with their long-term experience with migraine pain. Recent research provides a foundation for differentiating episodic and chronic migraine based on neurophysiologic and neuroimaging tools. In this literature review, we consider these findings in the context of models designed to explain the physiology and progression of episodic migraine into chronic migraine, and consider treatment of chronic migraine in susceptible individuals. Advances in pharmacotherapy provide treatment options for chronic migraine. Of the currently available treatment options, only onabotulinumtoxinA and topiramate have received regulatory approval and have demonstrated efficacy in patients with chronic migraine, although the exact mechanisms of action are not fully elucidated.

Insights into the Functional Anatomy Behind the PREEMPT Injection Paradigm: Guidance on Achieving Optimal Outcomes.

OBJECTIVE: To provide clinically relevant insights on the identification of the muscles and techniques involved in the safe and effective use of onabotulinumtoxinA for chronic migraine prophylaxis. BACKGROUND: Although guidance on the use of onabotulinumtoxinA for chronic migraine is available, based on the Phase III Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical program, clinical experience has shown that insufficient understanding of the anatomy and function of the head and neck muscles may lead to undesirable outcomes and suboptimal efficacy. DESIGN/METHODS: Each muscle involved in the standardized PREEMPT injection paradigm is reviewed with a thorough description of each muscle's anatomy (ie, muscle description and location, innervation, vascular supply) and function. Key insights based on clinical experience are also provided to help improve outcomes. RESULTS: The identification of the muscles in the PREEMPT injection paradigm should be based on each patient's unique anatomy and injections should be administered using the advised techniques. A thorough examination of the patient prior to treatment is also critical to determine if any preexisting conditions may increase the risk for unwanted outcomes and appropriate expectations should be communicated. CONCLUSIONS: Thorough knowledge of the functional anatomy of the muscles involved in the standardized PREEMPT injection paradigm is critical to achieve the efficacy and safety observed in clinical trials. In addition, it is important to assess a patient's baseline condition to anticipate the risk for unwanted outcomes that may result from treatment.

Extracranial injections of botulinum neurotoxin type A inhibit intracranial meningeal nociceptors' responses to stimulation of TRPV1 and TRPA1 channels: Are we getting closer to solving this puzzle?

BACKGROUND: Administration of onabotulinumtoxinA (BoNT-A) to peripheral tissues outside the calvaria reduces the number of days chronic migraine patients experience headache. Because the headache phase of a migraine attack, especially those preceded by aura, is thought to involve activation of meningeal nociceptors by endogenous stimuli such as changes in intracranial pressure (i.e. mechanical) or chemical irritants that appear in the meninges as a result of a yet-to-be-discovered sequence of molecular/cellular events triggered by the aura, we sought to determine whether extracranial injections of BoNT-A alter the chemosensitivity of meningeal nociceptors to stimulation of their intracranial receptive fields. MATERIAL AND METHODS: Using electrophysiological techniques, we identified 161 C- and 135 Aδ-meningeal nociceptors in rats and determined their mechanical response threshold and responsiveness to chemical stimulation of their dural receptive fields with TRPV1 and TRPA1 agonists seven days after BoNT-A administration to different extracranial sites. Two paradigms were compared: distribution of 5 U BoNT-A to the lambdoid and sagittal sutures alone, and 1.25 U to the sutures and 3.75 U to the temporalis and trapezius muscles. RESULTS: Seven days after it was administered to tissues outside the calvaria, BoNT-A inhibited responses of C-type meningeal nociceptors to stimulation of their intracranial dural receptive fields with the TRPV1 agonist capsaicin and the TRPA1 agonist mustard oil. BoNT-A inhibition of responses to capsaicin was more effective when the entire dose was injected along the suture lines than when it was injected into muscles and sutures. As in our previous study, BoNT-A had no effect on non-noxious mechanosensitivity of C-fibers or on responsiveness of Aδ-fibers to mechanical and chemical stimulation. DISCUSSION: This study demonstrates that extracranial administration of BoNT-A suppresses meningeal nociceptors' responses to stimulation of their intracranial dural receptive fields with capsaicin and mustard oil. The findings suggest that surface expression of TRPV1 and TRPA1 channels in dural nerve endings of meningeal nociceptors is reduced seven days after extracranial administration of BoNT-A. In the context of chronic migraine, reduced sensitivity to molecules that activate meningeal nociceptors through the TRPV1 and TRPA1 channels can be important for BoNT-A's ability to act as a prophylactic.

Pregnancy outcomes following exposure to onabotulinumtoxinA.

PURPOSE: To evaluate pregnancy outcomes following onabotulinumtoxinA (US Food and Drug Administration pregnancy category C product) exposure using the Allergan safety database. METHODS: The Allergan Global Safety Database contains reports of onabotulinumtoxinA administration before/during pregnancy, including both prospective (reported before outcome) and retrospective (outcome already known) cases. The database was searched from 1/1/90 to 12/31/13 for eligible cases where treatment occurred during pregnancy or ≤3 months before conception. To minimize reporting bias, prevalence rates were focused on prospective cases. RESULTS: Of 574 pregnancies with maternal onabotulinumtoxinA exposure, 232 were eligible with known outcomes. Patients received onabotulinumtoxinA most frequently for cosmetic indications (50.5%), movement disorders (16.8%), and pain disorders (14.2%). Of the 137 with dose information, 40.1% received <50U, 14.6% 50U to <100U, 27.7% 100U to <200U, and 17.5% ≥200U. Among 146 cases with known maternal age, 47.9% were ≥35 years. Most (96.0%) fetal exposures occurred during/before the first trimester. Of the 137 prospective cases (139 fetuses), 110 (79.1%) were live births; 29 (20.9%; 95% CI, 14.0-30.0%) ended in fetal loss (21 spontaneous, 8 induced abortions). Among live births, 106 (96.4%) were normal, with four abnormal birth outcomes (1 major fetal defect, 2 minor fetal malformations, 1 birth complication), giving a 2.7% (3/110; 95% CI, 0.6-8.0%) prevalence rate for overall fetal defects. CONCLUSIONS: A 24-year retrospective review of the Allergan safety database shows that the prevalence of fetal defects in onabotulinumtoxinA-exposed mothers before/during pregnancy (2.7%) is comparable with background rates in the general population. Pregnancy outcome monitoring in onabotulinumtoxinA-exposed women continues.

Repeated OnabotulinumtoxinA Treatment of Glabellar Lines at Rest Over Three Treatment Cycles.

BACKGROUND: OnabotulinumtoxinA has demonstrated the ability to eliminate mild glabellar lines at rest; however, less is known regarding the effect of repeat treatment on more severe lines at rest. OBJECTIVE: To assess the effect of repeated onabotulinumtoxinA treatment for reduction of glabellar lines at rest. METHODS: Subjects 18 to 75 years old with at least mild glabellar lines at rest, as assessed by the validated Facial Wrinkle Scale (FWS) with photonumeric guide (score ≥ 1), received 3 treatments of 20 U onabotulinumtoxinA 4 months apart (N = 225). "Response" was defined as elimination of glabellar lines at rest (FWS score = 0) at any time point (Days 7, 30, 60, 90, and 120). Effect of treatment cycle on response was analyzed using repeated measures logistic regressions (p < .05). RESULTS: Most subjects were female (85%) and white (88%) (age range: 35-54 years). The likelihood of significant response was as follows: for all subjects combined (odds ratio [OR]: 1.31), for subjects with mild resting lines at baseline (OR: 1.49), and for older women (≥55 years) with mild resting lines at baseline (OR: 2.22). Of all subjects, 76% responded after 1 treatment, and 45% responded in all 3 cycles. CONCLUSION: Subjects repeatedly treated with onabotulinumtoxinA showed progressive improvement in glabellar lines at rest.

Neck Pain and Cervical Dystonia: Treatment Outcomes from CD PROBE (Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy).

BACKGROUND: Pain is a prevailing feature of cervical dystonia (CD), the most common form of focal dystonia. This analysis examined pain relief after onabotulinumtoxinA treatment in CD subjects with moderate/severe pain from the Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE). METHODS: CD PROBE was a prospective, multicenter, observational registry of CD subjects who were naïve to botulinum toxin (BoNT), new to physician, or had not received BoNT within ≥ 16 weeks if in a clinical trial. Subjects were eligible for 3 treatments, with variable session intervals. Descriptive and inferential statistics were utilized to evaluate the change in pain scores in the population with moderate/severe neck pain at baseline (Pain Numeric Rating Scale [PNRS] score 4 to 10). RESULTS: Of 1046 enrolled, 733 (70.7%) had moderate/severe neck pain at baseline. Postinjection pain questionnaire responses 4 to 6 weeks after each of the 3 treatments revealed that a majority of subjects (67.1%, 72.4%, and 76.4%) reported pain relief; mean time to pain relief was 7.1, 7.4, and 7.6 days. All pain scales showed significant improvements from baseline to final visit (all P < 0.0001): PNRS, mean 6.6 to 3.8; CD Impact Profile-58 Pain and Discomfort subscale, mean 78.7 to 56.5; and Toronto Western Spasmodic Torticollis Rating Scale Pain subscale, mean 12.6 to 8.5. Multivariable regression models showed that initial pain score significantly contributed to the final pain score for all scales. CONCLUSION: Results from this real-world clinical registry indicate that a majority of CD subjects with moderate/severe neck pain experience significant relief following onabotulinumtoxinA treatment.

A Prospective, Nonrandomized, Open-Label Study of the Efficacy and Safety of OnabotulinumtoxinA in Adolescents with Primary Axillary Hyperhidrosis.

OBJECTIVE: To evaluate the efficacy and safety of onabotulinumtoxinA in adolescents with primary axillary hyperhidrosis. METHODS: This 52-week, multicenter, nonrandomized, open-label study was conducted in 141 adolescents ages 12 to 17 years with severe primary axillary hyperhidrosis. Patients could receive up to six treatments with onabotulinumtoxinA (50 U per axilla), with re-treatment occurring no sooner than 8 weeks after the prior treatment cycle and no later than 44 weeks after the initial treatment cycle. The primary efficacy measure was treatment response, based on self-assessed hyperhidrosis severity following the first two treatments using the 4-point Hyperhidrosis Disease Severity Scale (HDSS). Other efficacy measures included spontaneous resting sweat production and health outcomes. RESULTS: Fifty-six (38.9%) participants underwent one treatment, 59 (41.0%) underwent two, 20 (13.9%) underwent three, 6 (4.2%) underwent four, and 3 (2.1%) underwent five. OnabotulinumtoxinA significantly improved HDSS scores and decreased sweat production compared with treatment cycle baselines. Seventy-nine patients (54.9%) responded to treatment based on HDSS criteria. From 56.6% to 72.3% of patients experienced a two-grade or more improvement at 4 and 8 weeks after each of the first two treatments. The majority (79.4%-93.2%) had a 75% or greater reduction in sweat production at week 4 (treatments 1-3). The median duration of effect for responders ranged from 134 to 152 days. Using quality of life measures, health outcomes improved markedly. Eight patients (5.6%) had mild or moderate treatment-related adverse events. No unexpected safety signals were observed in this study. Neutralizing antibodies to onabotulinumtoxinA did not develop. CONCLUSION: OnabotulinumtoxinA injections provided beneficial effects in adolescents with primary axillary hyperhidrosis.

Selective inhibition of meningeal nociceptors by botulinum neurotoxin type A: therapeutic implications for migraine and other pains.

BACKGROUND: Meningeal and other trigeminal nociceptors are thought to play important roles in the initiation of migraine headache. Currently, the only approved peripherally administered chronic migraine prophylactic drug is onabotulinumtoxinA. The purpose of this study was to determine how botulinum neurotoxin type A (BoNT-A) affects naïve and sensitized meningeal nociceptors. MATERIAL AND METHODS: Using electrophysiological techniques, we identified 43 C- and 36 Aδ-meningeal nociceptors, and measured their spontaneous and evoked firing before and after BoNT-A administration to intracranial dura and extracranial suture-receptive fields. RESULTS: As a rule, BoNT-A inhibited C- but not Aδ-meningeal nociceptors. When applied to nonsensitized C-units, BoNT-A inhibited responses to mechanical stimulation of the dura with suprathreshold forces. When applied to sensitized units, BoNT-A reversed mechanical hypersensitivity. When applied before sensitization, BoNT-A prevented development of mechanical hypersensitivity. When applied extracranially to suture branches of intracranial meningeal nociceptors, BoNT-A inhibited the mechanical responsiveness of the suture branch but not dural axon. In contrast, BoNT-A did not inhibit C-unit responses to mechanical stimulation of the dura with threshold forces, or their spontaneous activity. DISCUSSION: The study provides evidence for the ability of BoNT-A to inhibit mechanical nociception in peripheral trigeminovascular neurons. These findings suggest that BoNT-A interferes with neuronal surface expression of high-threshold mechanosensitive ion channels linked preferentially to mechanical pain by preventing their fusion into the nerve terminal membrane.