Intervening in the Premonitory Phase to Prevent Migraine: Prospects for Pharmacotherapy

Migraine is a common brain condition characterised by disabling attacks of headache with sensory sensitivities. Despite increasing understanding of migraine neurobiology and the impacts of this on therapeutic developments, there remains a need for treatment options for patients underserved by currently available therapies. The first specific drugs developed to treat migraine acutely, the serotonin-5-hydroxytryptamine [5-HT1B/1D] receptor agonists (triptans), seem to require headache onset in order to have an effect, while early treatment during mild pain before headache escalation improves short-term and long-term outcomes. Some patients find treating in the early window once headache has started but not escalated difficult, and migraine can arise from sleep or in the early hours of the morning, making prompt treatment after pain onset challenging. Triptans may be deemed unsuitable for use in patients with vascular disease and in those of older age and may not be effective in a proportion of patients. Headache is also increasingly recognised as being just one of the many facets of the migraine attack, and for some patients it is not the most disabling symptom. In many patients, painless symptoms can start prior to headache onset and can reliably warn of impending headache. There is, therefore, a need to identify therapeutic targets and agents that may be used as early as possible in the course of the attack, to prevent headache onset before it starts, and to reduce both headache and non-headache related attack burden. Early small studies using domperidone, naratriptan and dihydroergotamine have suggested that this approach could be useful; these studies were methodologically less rigorous than modern day treatment studies, of small sample size, and have not since been replicated. The emergence of novel targeted migraine treatments more recently, specifically calcitonin gene-related peptide (CGRP) receptor antagonists (gepants), has reignited interest in this strategy, with encouraging results. This review summarises historical and emerging data in this area, supporting use of the premonitory phase as an opportunity to intervene as early as possible in migraine to prevent attack-related morbidity.

Can calcitonin gene-related peptide monoclonal antibodies ameliorate writer's cramp and migraine?

Recently, calcitonin gene-related peptide (CGRP) monoclonal antibodies (mAbs) have become available as a prophylactic treatment for migraine and have shown high efficacy and safety in clinical practice. CGRP mAbs have been reported to be effective not only for migraine but also for other comorbidities, such as psychiatric complications in patients with migraine. However, there are no reports examining the effect of CGRP mAbs on dystonia. We treated a patient with comorbid migraine and focal task-specific dystonia (writer's cramp) with a CGRP mAb (erenumab) because of an increase in monthly migraine days despite the addition of migraine prophylaxis. In this patient, erenumab treatment for 3 months led to improvements in symptoms of both focal dystonia and migraine, suggesting a role for CGRP in the pathophysiology of both conditions.

CGRP-targeted medication in chronic migraine - systematic review

BACKGROUND

Chronic migraine is a highly debilitating condition that is often difficult to manage, particularly in the presence of medication overuse headache. Drugs targeting the calcitonin gene-related peptide (CGRP), or its receptor have shown promising results in treating this disorder.

METHODS

We searched Pubmed and Embase to identify randomized clinical trials and real-world studies reporting on the use of medication targeting the calcitonin gene-related peptide in patients with chronic migraine.

RESULTS

A total of 270 records were identified. Nineteen studies qualified for the qualitative analysis. Most studies reported on monoclonal antibodies targeting CGRP (anti-CGRP mAbs), that overall prove to be effective in decreasing monthly migraine days by half in about 27.6-61.4% of the patients. Conversion from chronic to episodic migraine was seen in 40.88% of the cases, and 29-88% of the patients stopped medication overuse. Obesity seems to be the main negative predictor of response to anti-CGRP mAbs. There is no evidence to suggest the superiority of one anti-CGRP mAb. Despite the lack of strong evidence, the combination of anti-CGRP medication with onabotulinumtoxinA in chronic migraine is likely to bring benefits for resistant cases. Atogepant is the first gepant to demonstrate a significant decrease in monthly migraine days compared to placebo in a recent trial. Further, anti-CGRP mAb and gepants have a good safety profile.

CONCLUSION

There is strong evidence from randomized trials and real-world data to suggest that drugs targeting CGRP are a safe and effective treatment for chronic migraine.

Pathophysiology of Migraine

OBJECTIVE

This article provides an overview of the current understanding of migraine pathophysiology through insights gained from the extended symptom spectrum of migraine, neuroanatomy, migraine neurochemistry, and therapeutics.

LATEST DEVELOPMENTS

Recent advances in human migraine research, including human experimental migraine models and functional neuroimaging, have provided novel insights into migraine attack initiation, neurochemistry, neuroanatomy, and therapeutic substrates. It has become clear that migraine is a neural disorder, in which a wide range of brain areas and neurochemical systems are implicated, producing a heterogeneous clinical phenotype. Many of these neural pathways are monoaminergic and peptidergic, such as those involving calcitonin gene-related peptide and pituitary adenylate cyclase-activating polypeptide. We are currently witnessing an exciting era in which specific drugs targeting these pathways have shown promise in treating migraine, including some studies suggesting efficacy before headache has even started.

ESSENTIAL POINTS

Migraine is a brain disorder involving both headache and altered sensory, limbic, and homeostatic processing. A complex interplay between neurotransmitter systems, physiologic systems, and pain processing likely occurs. Targeting various therapeutic substrates within these networks provides an exciting avenue for future migraine therapeutics.

Anti-CGRP antibody galcanezumab modifies the function of the trigeminovascular nocisensor complex in the rat

BACKGROUND

Monoclonal antibodies directed against the neuropeptide calcitonin gene-related peptide (CGRP) are effective in the prevention of chronic and frequent episodic migraine. Since the antibodies do not cross the blood brain barrier, their antinociceptive effect is attributed to effects in meningeal tissues. We aimed to probe if such an antibody can be visualized within the dura mater and the trigeminal ganglia following its administration to rats and to examine if the activity of the trigeminovascular nocisensor complex is influenced by this treatment.

METHODS

Effects of the anti-CGRP antibody galcanezumab on the trigeminovascular nocisensor complex was examined by measuring release of sensory neuropeptides and histamine from the rat dura mater. Deposits of galcanezumab were visualized by fluorescence microscopy in the trigeminal ganglion and the dura mater.

RESULTS

Fluorophore-labelled galcanezumab was detected in the dura mater and the trigeminal ganglion up to 30 days after treatment affirming the long-lasting modulatory effect of this antibody. In female rats, seven days after systemic treatment with galcanezumab the capsaicin-induced release of CGRP was decreased, while that of substance P (SP) was increased in the dura mater. In control rats, release of the inhibitory neuropeptide somatostatin (SOM) was higher in females than in males. Stimulation with high concentration of KCl did not significantly change the release of SOM in control animals, while in rats treated with galcanezumab SOM release was slightly reduced. Galcanezumab treatment also reduced the amount of histamine released from dural mast cells upon stimulation with CGRP, while the effect of compound 48/80 on histamine release was not changed.

CONCLUSIONS

Galcanezumab treatment is followed by multiple changes in the release of neuropeptides and histamine in the trigeminal nocisensor complex, which may contribute to the migraine preventing effect of anti-CGRP antibodies. These changes affecting the communication between the components of the trigeminal nocisensor complex may reduce pain susceptibility in migraine patients treated with CGRP targeting monoclonal antibodies.

Double-blind, randomized, placebo-controlled study to evaluate erenumab-specific central effects: an fMRI study

OBJECTIVE

Given the findings of central effects of erenumab in the literature, we aimed to conduct a rigorous placebo-controlled, double-blind, randomized study to elucidate whether the observed changes are directly attributable to the drug.

METHODS

We recruited 44 patients with migraine, randomly assigning them to either the erenumab 70 mg or the placebo group. 40 patients underwent fMRI scanning using a trigeminal nociceptive paradigm both, pre- and four weeks post-treatment. Participants kept a headache diary throughout the whole study period of two months in total. A clinical response was defined as a ≥30% reduction in headache frequency at follow-up. Details of this study have been preregistered in the open science framework: https://osf.io/ygf3t .

RESULTS

Seven participants of the verum group (n=33.33%) and 4 of the placebo group (21.05%) experienced improvements in migraine activity, characterized by a minimum of 30% reduction in monthly headache frequency compared to baseline. The imaging data show an interaction between the verum medication and the response. Whilst numbers were too small for individual analyses (Verum vs. Placebo and Responder vs. Non-Responder), the variance-weighted analysis (Verum vs Placebo, scan before vs after weighted for response) revealed specific decrease in thalamic, opercular and putamen activity.

INTERPRETATION

The central effects of erenumab could be reproduced in a placebo randomized design, further confirming its central role in migraine modulation. The mechanism, whether direct or secondary to peripheral mode of action, needs further exploration. It is important to note that the response rate to erenumab 70mg in this study was not as substantial as anticipated in 2019, when this study was planned. This resulted in a too small sample size for a subgroup analysis based on the responder status was associated with both the verum drug and the relative reduction in headache days.

Targeting CGRP pathways and aura: A peripheral site with a central effect

Targeting CGRP-pathways has substantially expanded our options for treating individuals with migraine. Although the efficacy of these drugs on migraine aura is yet to be fully revealed, it seems from existing studies that CGRP antagonism reduces the number of migraine auras. The present perspective summarizes the evidence linking CGRP to the migraine aura and proposes a model by which targeting the CGRP-pathways and, thus, inhibition the interaction between C- and Aδ-trigeminal fibers might reverse a possible high cortical glutamate level leading to a reduced number of migraine auras.

Patterns of anti-CGRP mAbs use and variation of triptan consumption following treatment initiation: A descriptive drug utilization study in the Tuscany region, Italy

OBJECTIVE

To describe the pattern of anti-calcitonin gene-related peptide monoclonal antibodies (anti-CGRP mAbs) utilization in the Tuscany region, Italy, and the variation of triptan consumption after treatment initiation.

BACKGROUND

Given the recent commercialization of anti-CGRP mAbs as migraine preventive medications, real-world evidence on their patterns of utilization and their impact on migraine abortive medication use is still limited.

METHODS

A retrospective, descriptive, cohort study on the real-world utilization of anti-CGRP mAbs was performed using the population-based regional administrative database of Tuscany. Patients with ≥1 anti-CGRP mAb dispensing (namely erenumab, galcanezumab, fremanezumab) between April 1, 2019, and September 30, 2021, were identified. The first dispensing was the cohort entry (CE). New users (NUs) were patients with no anti-CGRP mAb dispensing before CE. Kaplan-Meier (KM) curves were plotted to describe the cumulative probability of remaining with the initial anti-CGRP mAb during a 15-month follow-up period as a measure of treatment persistence. Among NUs with ≥2 triptan dispensings during the 6 months before CE (i.e., baseline), the mean monthly number of triptan dosage units dispensed was measured in five consecutive follow-up time windows (months 1-3, 4-6, 7-9, 10-12, 13-15) and the difference from the baseline was calculated.

RESULTS

A total of 624 NUs (erenumab = 295, galcanezumab = 223, fremanezumab = 106) were identified, of whom 188 (78%) were women. Mean age was 49.2 years (standard deviation [SD] = 12.6). The survival to discontinuation at 6, 12, and 15 months was about 69%, 48%, and 6%, respectively. The survival to switch was about 6% at 15 months. The observed variation of triptan consumption at 3/6/9/12/15 months and the corresponding SD was -4.4 [8.2]/-5.2 [9.0]/-5.5 [9.2]/-5.4 [9.2]/-4.5 [10.0], respectively.

CONCLUSION

Patient demographics reflect the place of these medications in therapy. Overall, findings seem to indicate a favorable tolerability and effectiveness profile. Further studies are warranted to better establish the long-term comparative effectiveness, safety, and cost effectiveness of anti-CGRP mAbs compared to other preventive medications.

Peripherally acting anti-CGRP monoclonal antibodies alter cortical gray matter thickness in migraine patients: A prospective cohort study

Migraine is underpinned by central nervous system neuroplastic alterations thought to be caused by the repetitive peripheral afferent barrage the brain receives during the headache phase (cortical hyperexcitability). Calcitonin gene-related peptide monoclonal antibodies (anti-CGRP-mAbs) are highly effective migraine preventative treatments. Their ability to alter brain morphometry in treatment-responders vs. non-responders is not well understood. Our aim was to determine the effects of the anti-CGRP-mAb galcanezumab on cortical thickness after 3-month treatment of patients with high-frequency episodic or chronic migraine. High-resolution magnetic resonance imaging was performed pre- and post-treatment in 36 migraine patients. In this group, 19 patients were classified responders (≥50 % reduction in monthly migraine days) and 17 were considered non-responders (<50 % reduction in monthly migraine days). Following cross-sectional processing to analyze the baseline differences in cortical thickness, two-stage longitudinal processing and symmetrized percent change were conducted to investigate treatment-related brain changes. At baseline, no significant differences were found between the responders and non-responders. After 3-month treatment, decreased cortical thickness (compared to baseline) was observed in the responders in regions of the somatosensory cortex, anterior cingulate cortex, medial frontal cortex, superior frontal gyrus, and supramarginal gyrus. Non-responders demonstrated decreased cortical thickness in the left dorsomedial cortex and superior frontal gyrus. We interpret the cortical thinning seen in the responder group as suggesting that reduction in head pain could lead to changes in neural swelling and dendritic complexity and that such changes reflect the recovery process from maladaptive neural activity. This conclusion is further supported by our recent study showing that 3 months after treatment initiation, the incidence of premonitory symptoms and prodromes that are followed by headache decreases but not the incidence of the premonitory symptoms or prodromes themselves (that is, cortical thinning relates to reductions in the nociceptive signals in the responders). We speculate that a much longer recovery period is required to allow the brain to return to a more 'normal' functioning state whereby prodromes and premonitory symptoms no longer occur.

Central generators of migraine and autonomic cephalalgias as targets for personalized pain management: Translational links

BACKGROUND AND OBJECTIVE

Migraine oscillates between different states in association with internal homeostatic functions and biological rhythms that become more easily dysregulated in genetically susceptible individuals. Clinical and pre-clinical data on migraine pathophysiology support a primary role of the central nervous system (CNS) through 'dysexcitability' of certain brain networks, and a critical contribution of the peripheral sensory and autonomic signalling from the intracranial meningeal innervation. This review focuses on the most relevant back and forward translational studies devoted to the assessment of CNS dysfunctions involved in primary headaches and discusses the role they play in rendering the brain susceptible to headache states.

METHODS AND RESULTS

We collected a body of scientific literature from human and animal investigations that provide a compelling perspective on the anatomical and functional underpinnings of the CNS in migraine and trigeminal autonomic cephalalgias. We focus on medullary, hypothalamic and corticofugal modulation mechanisms that represent strategic neural substrates for elucidating the links between trigeminovascular maladaptive states, migraine triggering and the temporal phenotype of the disease.

CONCLUSION

It is argued that a better understanding of homeostatic dysfunctional states appears fundamental and may benefit the development of personalized therapeutic approaches for improving clinical outcomes in primary headache disorders.

SIGNIFICANCE

This review focuses on the most relevant back and forward translational studies showing the crucial role of top-down brain modulation in triggering and maintaining primary headache states and how these central dysfunctions may interact with personalized pain management strategies.

Mode and site of action of therapies targeting CGRP signaling

Targeting CGRP has proved to be efficacious, tolerable, and safe to treat migraine; however, many patients with migraine do not benefit from drugs that antagonize the CGRPergic system. Therefore, this review focuses on summarizing the general pharmacology of the different types of treatments currently available, which target directly or indirectly the CGRP receptor or its ligand. Moreover, the latest evidence regarding the selectivity and site of action of CGRP small molecule antagonists (gepants) and monoclonal antibodies is critically discussed. Finally, the reasons behind non-responders to anti-CGRP drugs and rationale for combining and/or switching between these therapies are addressed.

Mitochondrial metabolism related markers GDF-15, FGF-21, and HIF-1α are elevated in pediatric migraine attacks

OBJECTIVE

The purpose of this study was to investigate the serum levels of mitochondrial metabolism/reactive oxygen species (ROS)-related peptides (hypoxia inducible factor-1α [HIF-1α], fibroblast growth factor-21 [FGF-21], growth differentiation factor-15 [GDF-15]) and key migraine-related neuropeptides (calcitonin gene-related peptide [CGRP], pituitary adenylate cyclase-activating peptide-38 [PACAP-38], substance P [SP], and vasoactive intestinal peptide [VIP]) during migraine attacks and to evaluate their diagnostic value in pediatric migraine.

BACKGROUND

There is increasing evidence for the important role of impairment in oxidative mitochondrial metabolism in the pathophysiology of migraine. Potential biomarkers that may reflect the relationship between migraine and mitochondrial dysfunction are unclear.

METHODS

A total of 68 female pediatric migraine patients without aura and 20 female healthy controls aged 8-18 years, admitted to the hospital, were enrolled in this cross-sectional study. Serum concentrations of these molecules were determined by enzyme-linked immunosorbent assays, and clinical features and their possible diagnostic value were analyzed.

RESULTS

Serum levels of HIF-1α (252.4 ± 51.9 [mean ± standard deviation]) pg/mL), GDF-15 (233.7 ± 24.7 pg/mL), FGF-21 (96.1 ± 13.1 pg/mL), CGRP (44.5 ± 11.3), and PACAP-38 (504.7 ± 128.9) were significantly higher in migraine patients compared to healthy controls (199.8 ± 26.8, 192.8 ± 20.7, 79.3 ± 4.1, 34.1 ± 3.5 and 361.2 ± 86.3 pg/mL, respectively). The serum levels of these peptides were also higher in patients with chronic migraine than in patients with episodic migraine, and higher in the ictal period than in the interictal period. A positive correlation was found between attack frequency and both HIF-1α and FGF-21 levels in migraine patients. Serum levels of VIP and SP were not different between the migraine patients and healthy controls.

CONCLUSION

Migraine attacks are accompanied by elevated HIF-1α, FGF-21, GDF-15, CGRP, and PACAP-38 in medication-naive pediatric patients with migraine. Elevated circulating mitochondrial metabolism/ROS-related peptides suggest a mitochondrial stress in pediatric migraine attacks and may have potential diagnostic value in monitoring disease progression and treatment response in children. Novel approaches intervening with mitochondrial metabolism need to be investigated.

Neuroimaging in the pre-ictal or premonitory phase of migraine: a narrative review

BACKGROUND

The premonitory phase, or prodrome, of migraine, provides valuable opportunities to study attack initiation and for treating the attack before headache starts. Much that has been learned about this phase in recent times has come from the outcomes of functional imaging studies. This review will summarise these studies to date and use their results to provide some feasible insights into migraine neurobiology.

MAIN BODY

The ability to scan repeatedly a patient without radiation and with non-invasive imaging modalities, as well as the recognition that human experimental migraine provocation compounds, such as nitroglycerin (NTG) and pituitary adenylate cyclase activating polypeptide (PACAP), can trigger typical premonitory symptoms (PS) and migraine-like headache in patients with migraine, have allowed feasible and reproducible imaging of the premonitory phase using NTG. Some studies have used serial scanning of patients with migraine to image the migraine cycle, including the 'pre-ictal' phase, defined by timing to headache onset rather than symptom phenotype. Direct observation and functional neuroimaging of triggered PS have also revealed compatible neural substrates for PS in the absence of headache. Various imaging methods including resting state functional MRI (rsfMRI), arterial spin labelling (ASL), positron emission tomography (PET) and diffusion tensor imaging (DTI) have been used. The results of imaging the spontaneous and triggered premonitory phase have been largely consistent and support a theory of central migraine attack initiation involving brain areas such as the hypothalamus, midbrain and limbic system. Early dysfunctional pain, sensory, limbic and homeostatic processing via monoaminergic and peptidergic neurotransmission likely manifests in the heterogeneous PS phenotype.

CONCLUSION

Advances in human migraine research, including the use of functional imaging techniques lacking radiation or radio-isotope exposure, have led to an exciting opportunity to study the premonitory phase using repeated measures imaging designs. These studies have provided novel insights into attack initiation, migraine neurochemistry and therapeutic targets. Emerging migraine-specific therapies, such as those targeting calcitonin gene-related peptide (CGRP), are showing promise acutely when taken during premonitory phase to reduce symptoms and prevent subsequent headache. Therapeutic research in this area using PS for headache onset prediction and early treatment is likely to grow in the future.

Management of cluster headache: Treatments and their mechanisms

BACKGROUND

The management of cluster headache is similar to that of other primary headache disorders and can be broadly divided into acute and preventive treatments. Acute treatments for cluster headache are primarily delivered via rapid, non-oral routes (such as inhalation, nasal, or subcutaneous) while preventives include a variety of unrelated treatments such as corticosteroids, verapamil, and galcanezumab. Neuromodulation is becoming an increasingly popular option, both non-invasively such as vagus nerve stimulation when medical treatment is contraindicated or side effects are intolerable, and invasively such as occipital nerve stimulation when medical treatment is ineffective. Clinically, this collection of treatment types provides a range of options for the informed clinician. Scientifically, this collection provides important insights into disease mechanisms.

METHODS

Two authors performed independent narrative reviews of the literature on guideline recommendations, clinical trials, real-world data, and mechanistic studies.

RESULTS

Cluster headache is treated with acute treatments, bridge treatments, and preventive treatments. Common first-line treatments include subcutaneous sumatriptan and high-flow oxygen as acute treatments, corticosteroids (oral or suboccipital injections) as bridge treatments, and verapamil as a preventive treatment. Some newer acute (non-invasive vagus nerve stimulation) and preventive (galcanezumab) treatments have excellent clinical trial data for episodic cluster headache, while other newer treatments (occipital nerve stimulation) have been specifically tested in treatment-refractory chronic cluster headache. Most treatments are suspected to act on the trigeminovascular system, the autonomic system, or the hypothalamus.

CONCLUSIONS

The first-line treatments have not changed in recent years, but new treatments have provided additional options for patients.

Treatment of hemiplegic migraine with anti-calcitonin gene-related peptide monoclonal antibodies: A case series in a tertiary-care headache center

Hemiplegic migraine (HM) is a subtype of migraine with aura that includes motor weakness; such headaches can be excruciating. The presence of not only headache but also aura symptoms of HM increase the burden on patients, and the treatment of HM is sometimes challenging. Monoclonal antibodies (mAbs) targeting the calcitonin gene-related peptide (CGRP) pathway are novel migraine preventive treatments that have shown promising efficacy in patients with migraine; however, there have been no reports regarding their efficacy in HM to date. Six patients with HM were treated with galcanezumab in a tertiary-care headache center. After 3 months of treatment, the number of monthly days with headache of at least moderate severity was reduced in three patients. The number of days each month with weakness was also reduced in four patients. Furthermore, the Patient's Global Impression of Change and change in Migraine Disability Assessment total score, were improved in five of the six patients after the treatment; however, the change from baseline in days with bothersome symptoms did not show any specific trends in our patients. Notably, no adverse events were reported during the treatments. The mechanism underlying the improvement in aura symptoms in our patients is not clear; however, we speculate that a small amount of CGRP mAbs have a direct mode of action in the central nervous system; alternatively, blocking the CGRP pathway in the periphery may secondarily inhibit cortical spreading depression. While prudence must be practiced, galcanezumab was still generally effective in HM and well tolerated. Further prospective clinical studies will more clearly elucidate the effects of CGRP mAbs in patients with HM.

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

Calcitonin gene-related peptide (CGRP) monoclonal antibodies for migraine

The introduction of calcitonin gene-related peptide monoclonal antibodies represents a step forward in preventive migraine treatment as the first agents to target the underlying pathogenesis of migraine. In trials they act more quickly, have better long-term adherence and appear to be better tolerated than other treatments. Major disadvantages are their high cost and unknown safety in pregnancy and in cardiovascular disease. To mitigate these concerns, they should be used according to guidance produced by professional bodies, with defined starting and stopping criteria. We do not yet know whether they are more effective than standard care; many patients may still be better treated by other means, in particular addressing lifestyle factors and medication-overuse headache.

Can calcitonin gene-related peptide monoclonal antibody improve migraine and restless legs syndrome?

BACKGROUND

A significant association between migraine and restless legs syndrome (RLS) has been reported, and their coexistence is not uncommon. We report a patient with concomitant migraine and RLS who showed improvement of both migraine and RLS symptoms after treatment with galcanezumab, a calcitonin gene-related peptide (CGRP) monoclonal antibody.

CASE PRESENTATION

A 47-year-old woman had been treated in our outpatient headache clinic for migraine without aura. She had RLS since childhood and had been treated with dopamine agonists and α2δ ligands. Over the past 2 months, the patient suffered from frequent migraine headaches and worsening RLS symptoms, despite ongoing treatment. Therefore, galcanezumab was started. After 1 month, the number of headache days decreased from 20 to 4, and her score on the International RLS Study Group Rating Scale improved from 38 to 10. Her photo/phono/osmo-phobia were also markedly improved. The efficacy of galcanezumab for both headache and RLS was sustained over 5 months.

CONCLUSION

We report a case of improvement of both migraine and RLS after treatment with CGRP monoclonal antibody. Additional studies are needed to clarify how CGRP antagonism affects RLS symptoms in patients with migraine and RLS comorbidity.

Involvement of the cerebellum in migraine

Migraine is a disabling neurological disease characterized by moderate or severe headaches and accompanied by sensory abnormalities, e.g., photophobia, allodynia, and vertigo. It affects approximately 15% of people worldwide. Despite advancements in current migraine therapeutics, mechanisms underlying migraine remain elusive. Within the central nervous system, studies have hinted that the cerebellum may play an important sensory integrative role in migraine. More specifically, the cerebellum has been proposed to modulate pain processing, and imaging studies have revealed cerebellar alterations in migraine patients. This review aims to summarize the clinical and preclinical studies that link the cerebellum to migraine. We will first discuss cerebellar roles in pain modulation, including cerebellar neuronal connections with pain-related brain regions. Next, we will review cerebellar symptoms and cerebellar imaging data in migraine patients. Lastly, we will highlight the possible roles of the neuropeptide calcitonin gene-related peptide (CGRP) in migraine symptoms, including preclinical cerebellar studies in animal models of migraine.

Calcitonin gene-related peptide (CGRP) is a key molecule released in acute migraine attacks-Successful translation of basic science to clinical practice

Migraine is a highly prevalent neurovascular disorder afflicting more than 15% of the global population. Nearly three times more females are afflicted by migraine in the 18-50 years age group, compared to males. Migraine attacks are most often sporadic, but a subgroup of individuals experience a gradual increase in frequency over time; among these, up to 1%-2% of the global population develop chronic migraine. Although migraine symptoms have been known for centuries, the underlying mechanisms remain largely unknown. Two theories have dominated the current thinking-a neurovascular theory and a central neuronal theory with the origin of the attacks in the hypothalamus. During the last decades, the understanding of migraine has markedly advanced. This is supported by the early seminal demonstration of the trigeminovascular reflex 35 years ago and the insight that calcitonin gene-related peptide (CGRP) is a key molecule released in acute migraine attacks. The more recent findings that gepants, small molecule CGRP receptor blockers, and monoclonal antibodies generated against CGRP, or its canonical receptor are useful for the treatment of migraine, are other important issues. CGRP has been established as a key molecule in the neurobiology of migraine. Moreover, monoclonal antibodies to CGRP or the CGRP receptor represent a breakthrough in the understanding of migraine pathophysiology and have emerged as an efficacious prophylactic treatment for patients with severe migraine with excellent tolerability. This review describes the progression of research to reach the clinical usefulness of a large group of molecules that have in common the interaction with CGRP mechanisms in the trigeminal system to alleviate the burden for individuals afflicted by migraine.

A narrative review of the calcitonin peptide family and associated receptors as migraine targets: Calcitonin gene-related peptide and beyond

OBJECTIVE

To summarize the pharmacology of the calcitonin peptide family of receptors and explore their relationship to migraine and current migraine therapies.

BACKGROUND

Therapeutics that dampen calcitonin gene-related peptide (CGRP) signaling are now in clinical use to prevent or treat migraine. However, CGRP belongs to a broader peptide family, including the peptides amylin and adrenomedullin. Receptors for this family are complex, displaying overlapping pharmacologic profiles. Despite the focus on CGRP and the CGRP receptor in migraine research, recent evidence implicates related peptides and receptors in migraine.

METHODS

This narrative review summarizes literature encompassing the current pharmacologic understanding of the calcitonin peptide family, and the evidence that links specific members of this family to migraine and migraine-like behaviors.

RESULTS

Recent work links amylin and adrenomedullin to migraine-like behavior in rodent models and migraine-like attacks in individuals with migraine. We collate novel information that suggests females may be more sensitive to amylin and CGRP in the context of migraine-like behaviors. We report that drugs designed to antagonize the canonical CGRP receptor also antagonize a second CGRP-responsive receptor and speculate as to whether this influences therapeutic efficacy. We also discuss the specificity of current drugs with regards to CGRP isoforms and how this may influence therapeutic profiles. Lastly, we emphasize that receptors related to, but distinct from, the canonical CGRP receptor may represent underappreciated and novel drug targets.

CONCLUSION

Multiple peptides within the calcitonin family have been linked to migraine. The current focus on CGRP and its canonical receptor may be obscuring pathways to further therapeutics. Drug discovery schemes that take a wider view of the receptor family may lead to the development of new anti-migraine drugs with favorable clinical profiles. We also propose that understanding these related peptides and receptors may improve our interpretation regarding the mechanism of action of current drugs.

Prevention of Migraine

Migraine, a primary headache disorder is a chronic and complex neurological disease that affects millions of people worldwide, impacting their quality of life. It is one of the most common reasons why individuals seek the advice of their physician, and is one of the most common referrals seen in the offices of general neurologists and headache specialists. In the past decade, there has been robust research on not only the pathophysiology of migraine but in the efforts to treat and, importantly, prevent. The introduction of calcitonin gene related peptide antagonists (CGRP-A) have opened new doors for preventive treatment options. OnabotulinumtoxinA (BoNTA) has remained a staple in the treatment of chronic migraine with data emerging with combination therapy. Neurostimulation has offered additional nonpharmacologic approaches to migraine treatment. In addition to lifestyle and behavioral modifications, these have changed the landscape of migraine prevention.

Stimulation of CGRP-expressing neurons in the medial cerebellar nucleus induces light and touch sensitivity in mice

Calcitonin gene-related peptide (CGRP) is considered a major player in migraine pathophysiology. However, the location and mechanisms of CGRP actions in migraine are not clearly elucidated. One important question yet to be answered is: Does central CGRP signaling play a role in migraine? One candidate site is the cerebellum, which serves as a sensory and motor integration center and is activated in migraine patients. The cerebellum has the most CGRP binding sites in the central nervous system and a deep cerebellar nucleus, the medial nucleus (MN), expresses CGRP (MN^CGRP). A previous study demonstrated that CGRP delivery into the cerebellum induced migraine-like behaviors. We hypothesized that stimulation of MN^CGRP neurons might induce migraine-like behaviors. To test the hypothesis, we used an optogenetic strategy using Calca^Cre/+ mice to drive Cre-dependent expression of channelrhodopsin-2 selectively in CGRP neurons in the cerebellar MN. A battery of behavioral tests was done to assess preclinical behaviors that are surrogates of migraine symptoms, including light aversion, cutaneous allodynia, and spontaneous pain when MN^CGRP neurons were optically stimulated. Motor functions were also assessed. Optical stimulation of MN^CGRP neurons decreased the time spent in the light, which was coupled to increased time spent resting in the dark, but not the light. These changes were only significant in female mice. Plantar tactile sensitivity was increased in the ipsilateral paws of both sexes, but contralateral paw data were less clear. There was no significant increase in anxiety-like behavior, spontaneous pain (squint), or changes in gait. These discoveries reveal that MN^CGRP neurons may contribute to migraine-like sensory hypersensitivity to light and touch.

Effectiveness of anti-CGRP monoclonal antibodies on central symptoms of migraine

BACKGROUND

Clinical trials and observational studies with anti-calcitonin gene-related peptide antibodies poorly investigated their impact on migraine prodromal and accompanying symptoms. This information might help deciphering the biologics' pharmacodynamic and provide hints on migraine pathogenesis. Herein, we report the effects of erenumab, fremanezumab and galcanezumab on attack prodromal and accompanying symptoms and on neurological and psychiatric traits. .

METHODS

An explorative, prospective, questionnaire-based study was completed by a cohort (n = 80) of patients with chronic migraine patients presenting a sustained reduction of ≥50% of Migraine Disability Assessment Score and ≥30% of monthly migraine days three months after anti-calcitonin gene-related peptide antibodies treatment.

RESULTS

The majority of patients experienced a complete prevention of migraine symptoms without evidence of initial onset followed by attack abortion. Few patients reported the recurrence of prodromal (from 10% to 12.5%) or accompanying (from 1.3% to 8.8%) symptoms without headache. All patients with migraine with aura reported a decrease of aura incidence. Sleep changes (51.2%), increase in appetite (20.0%) and weight (18.8%) as well as a reduction in stress (45.0%), anxiety (26.3%), and panic attacks (15%) were also reported.

CONCLUSION

Anti-calcitonin gene-related peptide antibodies seems to significantly impact brain functions of migraineurs, preventing not only migraine headache but also its anticipatory and accompanying symptoms.

The monoclonal CGRP-receptor blocking antibody erenumab has different effects on brainstem and cortical sensory-evoked responses

Objectives

It is unclear whether the electrophysiological effects of erenumab, a monoclonal antibody against the calcitonin gene-related peptide receptor, occur only at the periphery of the trigeminal system or centrally and at the cortical level.

Methods

We prospectively enrolled 20 patients with migraine who had failed at least two preventative treatments. We measured the nociceptive blink reflex and non-noxious somatosensory evoked potentials in all participants. The area under the curve and habituation of the second polysynaptic nociceptive blink reflex component (R2) as well as the amplitude and habituation of somatosensory evoked potentials N20-P25 were measured. Electrophysiological data were collected at baseline (T0), 28 days (T1), and 56 days (T2) before each injection of erenumab (70 mg).

Results

Erenumab reduced the patients’ mean monthly headache days, headache intensity, and acute medication intake considerably at T1 and T2 (all p < 0.05). The nociceptive blink reflex area under the curve was considerably lower at T1 and T2 than at baseline without changing the habituation slope. At T2, there was a significant increase in the delayed somatosensory evoked potentials amplitude reduction (habituation) but not in the initial cortical activation.

Conclusion

Our findings showed that erenumab, in addition to its well-known peripheral effects, can induce central effects earlier in the brainstem and later in the cortex. We cannot rule out whether these results are due to a direct effect of erenumab on the central nervous system or an indirect effect secondary to peripheral drug modulation.

Migraine monoclonal antibodies against CGRP change brain activity depending on ligand or receptor target - an fMRI study

Background:

Monoclonal antibodies (mAbs) against calcitonin gene-related peptides (CGRP) are novel treatments for migraine prevention. Based on a previous functional imaging study which investigated the CGRP receptor mAb (erenumab), we hypothesized that (i) the CGRP ligand mAb galcanezumab would alter central trigeminal pain processing; (ii) responders to galcanezumab treatment would show specific hypothalamic modulation in contrast to non-responders; and (iii) the ligand and the receptor antibody differ in brain responses.

Methods:

Using an established trigeminal nociceptive functional magnetic imaging paradigm, 26 migraine patients were subsequently scanned twice: before and 2–3 weeks after administration of galcanezumab.

Results:

We found that galcanezumab decreases hypothalamic activation in all patients and that the reduction was stronger in responders than in non-responders. Contrasting erenumab and galcanezumab showed that both antibodies activate a distinct network. We also found that pre-treatment activity of the spinal trigeminal nucleus (STN) and coupling between the STN and the hypothalamus covariates with the response to galcanezumab.

Conclusions:

These data suggest that despite relative impermeability of the blood-brain barrier for CGRP mAb, mAb treatment induces certain and highly specific brain effects which may be part of the mechanism of their efficacy in migraine treatment.

Funding:

This work was supported by the German Ministry of Education and Research (BMBF) of ERA-Net Neuron under the project code BIOMIGA (01EW2002 to AM) and by the German Research Foundation (SFB936-178316478-A5 to AM). The funding sources did not influence study conduction in any way.

Clinical trial number:

The basic science study was preregistered in the Open Science Framework (https://osf.io/m2rc6).

CGRP Administration Into the Cerebellum Evokes Light Aversion, Tactile Hypersensitivity, and Nociceptive Squint in Mice

The neuropeptide calcitonin gene-related peptide (CGRP) is a major player in migraine pathophysiology. Previous preclinical studies demonstrated that intracerebroventricular administration of CGRP caused migraine-like behaviors in mice, but the sites of action in the brain remain unidentified. The cerebellum has the most CGRP binding sites in the central nervous system and is increasingly recognized as both a sensory and motor integration center. The objective of this study was to test whether the cerebellum, particularly the medial cerebellar nuclei (MN), might be a site of CGRP action. In this study, CGRP was directly injected into the right MN of C57BL/6J mice via a cannula. A battery of tests was done to assess preclinical behaviors that are surrogates of migraine-like symptoms. CGRP caused light aversion measured as decreased time in the light zone even with dim light. The mice also spent more time resting in the dark zone, but not the light, along with decreased rearing and transitions between zones. These behaviors were similar for both sexes. Moreover, significant responses to CGRP were seen in the open field assay, von Frey test, and automated squint assay, indicating anxiety, tactile hypersensitivity, and spontaneous pain, respectively. Interestingly, CGRP injection caused significant anxiety and spontaneous pain responses only in female mice, and a more robust tactile hypersensitivity in female mice. No detectable effect of CGRP on gait was observed in either sex. These results suggest that CGRP injection in the MN causes light aversion accompanied by increased anxiety, tactile hypersensitivity, and spontaneous pain. A caveat is that we cannot exclude contributions from other cerebellar regions in addition to the MN due to diffusion of the injected peptide. These results reveal the cerebellum as a new site of CGRP actions that may contribute to migraine-like hypersensitivity.

Real-world efficacy of galcanezumab for the treatment of migraine in Korean patients

BACKGROUND AND OBJECTIVE

We aimed to provide real-world data on the effectiveness of an anti-calcitonin gene-related peptide monoclonal antibody administered for treating migraine in Korean patients.

METHODS

We prospectively recruited patients with migraine who received galcanezumab treatment at a single university hospital from June 2020 to April 2021. The treatment response was assessed after three consecutive monthly injections. A 50% responder rate was evaluated based on ≥50% reduction in the number of moderate/severe headache days.

RESULTS

Overall, 87 patients were included in the analysis. Most patients were women (83.9%). They had a mean age of 41.7 ± 12.3 years (range 17-72). Sixty-five patients (74.7%) had chronic migraine, 35 patients (40.2%) had a history of medication-overuse headache, and 32 patients (36.8%) were previously unresponsive to or found intolerable five classes of preventive medication. After three months of treatment, mean changes in numbers of monthly headache days, moderate/severe headache days, crystal clear days, and days of acute medication use were -7.2 ± 8.43, -4.3 ± 9.76, 7.3 ± 8.50, and -4.1 ± 7.93, respectively. The 50% responder rates were 58.3%, 44.2%, and 40.6% for patients with unsuccessful previous use of 0-1, 2-4, and 5 preventive medication classes, respectively. Headache Impact Test-6 and Migraine Disability Assessment Test scores also decreased (-4.4 ± 8.09 and -32.9 ± 77.04, respectively).

CONCLUSION

In our cohort, the effectiveness and safety of galcanezumab were comparable with those reported in clinical trials, whereas a higher response rate was observed in the difficult-to-treat patient subset than that reported in trials. We provide real-world evidence of galcanezumab treatment benefits in Asian patients with migraine.

Could the New Anti-CGRP Monoclonal Antibodies Be Effective in Migraine Aura? Case Reports and Literature Review

Recently, monoclonal antibodies (mAbs) directed against calcitonin gene-related peptide (CGRP) (Eptinezumab, Fremanezumab, and Galcanezumab) or its receptor (Erenumab) have been approved for clinical use as prophylactic drugs for high-frequency episodic and chronic migraine. While their therapeutic effects on headache pain is well documented, there is scarce information on the usefulness of these medications in preventing migraine aura, which is believed to be associated with cortical spreading depression (CSD). Because of their large size, mAbs cannot easily cross the blood-brain barrier in high quantities, rendering the peripheral trigeminovascular system to likely be a major site of their action. In this paper, we report two cases of patients suffering from migraine with and without aura, who reported a complete disappearance of aura or reduced aura duration and intensity while taking Galcanezumab or Erenumab, respectively. Then, we present a brief overview of the literature about the controversial relationship between CSD and CGRP and about the potential "additional central" role of these mAbs in the pathophysiology of migraine aura.

Trigeminal sensory modulatory effects of galcanezumab and clinical response prediction

ABSTRACT

Galcanezumab, a monoclonal antibody against calcitonin gene-related peptide, is an emerging migraine preventative. We hypothesized that the preventive effects are conveyed via modulation of somatosensory processing and that certain sensory profiles may hence be associated with different clinical responses. We recruited migraine patients (n=26), who underwent quantitative sensory tests (QST) over the right V1 dermatome and forearm at baseline (T0), 2-3 weeks (T1), and one year (T12) after monthly galcanezumab treatment. The clinical response was defined as a reduction of ≥30% in headache frequency based on the headache diary. Predictors for clinical response were calculated using binary logistical regression models. After galcanezumab (T1 vs. T0), the heat pain threshold (HPT) (°C, 44.9 ± 3.4 vs. 43.0 ± 3.3, p=0.013) and mechanical pain threshold (MPT) (log mN, 1.60 ± 0.31 vs. 1.45 ± 0.26, p=0.042) were increased exclusively in the V1 dermatome, but not the forearm. These changes were immediate, did not differ between responders and non-responders, and did not last in one year of follow-up (T12 vs. T0). However, baseline HPT (OR: 2.13, 95% CI: 1.08-4.19, p = 0.029) on the forearm was a robust predictor for a clinical response three months later. In summary, our data demonstrated that galcanezumab modulates pain thresholds specifically in the V1 dermatome, but this modulation is short-lasting and irrelevant to clinical response. Instead, the clinical response may be determined by individual sensibility even before the administration of medication.

Schwann cell endosome CGRP signals elicit periorbital mechanical allodynia in mice

Efficacy of monoclonal antibodies against calcitonin gene-related peptide (CGRP) or its receptor (calcitonin receptor-like receptor/receptor activity modifying protein-1, CLR/RAMP1) implicates peripherally-released CGRP in migraine pain. However, the site and mechanism of CGRP-evoked peripheral pain remain unclear. By cell-selective RAMP1 gene deletion, we reveal that CGRP released from mouse cutaneous trigeminal fibers targets CLR/RAMP1 on surrounding Schwann cells to evoke periorbital mechanical allodynia. CLR/RAMP1 activation in human and mouse Schwann cells generates long-lasting signals from endosomes that evoke cAMP-dependent formation of NO. NO, by gating Schwann cell transient receptor potential ankyrin 1 (TRPA1), releases ROS, which in a feed-forward manner sustain allodynia via nociceptor TRPA1. When encapsulated into nanoparticles that release cargo in acidified endosomes, a CLR/RAMP1 antagonist provides superior inhibition of CGRP signaling and allodynia in mice. Our data suggest that the CGRP-mediated neuronal/Schwann cell pathway mediates allodynia associated with neurogenic inflammation, contributing to the algesic action of CGRP in mice.

Constipation Caused by Anti-calcitonin Gene-Related Peptide Migraine Therapeutics Explained by Antagonism of Calcitonin Gene-Related Peptide's Motor-Stimulating and Prosecretory Function in the Intestine

The development of small-molecule calcitonin gene-related peptide (CGRP) receptor antagonists (gepants) and of monoclonal antibodies targeting the CGRP system has been a major advance in the management of migraine. In the randomized controlled trials before regulatory approval, the safety of these anti-CGRP migraine therapeutics was considered favorable and to stay within the expected profile. Post-approval real-world surveys reveal, however, constipation to be a major adverse event which may affect more than 50% of patients treated with erenumab (an antibody targeting the CGRP receptor), fremanezumab or galcanezumab (antibodies targeting CGRP). In this review article we address the question whether constipation caused by inhibition of CGRP signaling can be mechanistically deduced from the known pharmacological actions and pathophysiological implications of CGRP in the digestive tract. CGRP in the gut is expressed by two distinct neuronal populations: extrinsic primary afferent nerve fibers and distinct neurons of the intrinsic enteric nervous system. In particular, CGRP is a major messenger of enteric sensory neurons which in response to mucosal stimulation activate both ascending excitatory and descending inhibitory neuronal pathways that enable propulsive (peristaltic) motor activity to take place. In addition, CGRP is able to stimulate ion and water secretion into the intestinal lumen. The motor-stimulating and prosecretory actions of CGRP combine in accelerating intestinal transit, an activity profile that has been confirmed by the ability of CGRP to induce diarrhea in mice, dogs and humans. We therefore conclude that the constipation elicited by antibodies targeting CGRP or its receptor results from interference with the physiological function of CGRP in the small and large intestine in which it contributes to the maintenance of peristaltic motor activity, ion and water secretion and intestinal transit.

The role of TRP ion channels in migraine and headache

Migraine afflicts more than 10% of the general population. Although its mechanism is poorly understood, recent preclinical and clinical evidence has identified calcitonin gene related peptide (CGRP) as a major mediator of migraine pain. CGRP, which is predominantly expressed in a subset of primary sensory neurons, including trigeminal afferents, when released from peripheral terminals of nociceptors, elicits arteriolar vasodilation and mechanical allodynia, a hallmark of migraine attack. Transient receptor potential (TRP) channels include several cationic channels with pleiotropic functions and ubiquitous distribution in various cells and tissues. Some members of the TRP channel family, such as the ankyrin 1 (TRPA1), vanilloid 1 and 4 (TRPV1 and TRPV4, respectively), and TRPM3, are abundantly expressed in primary sensory neurons and are recognized as sensors of chemical-, heat- and mechanical-induced pain, and play a primary role in several models of pain diseases, including inflammatory, neuropathic cancer pain, and migraine pain. In addition, TRP channel stimulation results in CGRP release, which can be activated or sensitized by various endogenous and exogenous stimuli, some of which have been proven to trigger or worsen migraine attacks. Moreover, some antimigraine medications seem to act through TRPA1 antagonism. Here we review the preclinical and clinical evidence that highlights the role of TRP channels, and mainly TRPA1, in migraine pathophysiology and may be proposed as new targets for its treatment.

Hypervigilance, Allostatic Load, and Migraine Prevention: Antibodies to CGRP or Receptor

Migraine involves brain hypersensitivity with episodic dysfunction triggered by behavioral or physiological stressors. During an acute migraine attack the trigeminal nerve is activated (peripheral sensitization). This leads to central sensitization with activation of the central pathways including the trigeminal nucleus caudalis, the trigemino-thalamic tract, and the thalamus. In episodic migraine the sensitization process ends with the individual act, but with chronic migraine central sensitization may continue interictally. Increased allostatic load, the consequence of chronic, repeated exposure to stressors, leads to central sensitization, lowering the threshold for future neuronal activation (hypervigilance). Ostensibly innocuous stressors are then sufficient to trigger an attack. Medications that reduce sensitization may help patients who are hypervigilant and help to balance allostatic load. Acute treatments and drugs for migraine prevention have traditionally been used to reduce attack duration and frequency. However, since many patients do not fully respond, an unmet treatment need remains. Calcitonin gene-related peptide (CGRP) is a vasoactive neuropeptide involved in nociception and in the sensitization of peripheral and central neurons of the trigeminovascular system, which is implicated in migraine pathophysiology. Elevated CGRP levels are associated with dysregulated signaling in the trigeminovascular system, leading to maladaptive responses to behavioral or physiological stressors. CGRP may, therefore, play a key role in the underlying pathophysiology of migraine. Increased understanding of the role of CGRP in migraine led to the development of small-molecule antagonists (gepants) and monoclonal antibodies (mAbs) that target either CGRP or the receptor (CGRP-R) to restore homeostasis, reducing the frequency, duration, and severity of attacks. In clinical trials, US Food and Drug Administration-approved anti-CGRP-R/CGRP mAbs were well tolerated and effective as preventive migraine treatments. Here, we explore the role of CGRP in migraine pathophysiology and the use of gepants or mAbs to suppress CGRP-R signaling via inhibition of the CGRP ligand or receptor.

The impact of CGRPergic monoclonal antibodies on prophylactic antimigraine therapy and potential adverse events

Migraine is a prevalent medical condition and the second most disabling neurological disorder. Regarding its pathophysiology, calcitonin gene-related peptide (CGRP) plays a key role, and, consequently, specific antimigraine pharmacotherapy has been designed to target this system. Hence, apart from the gepants, the recently developed monoclonal antibodies (mAbs) are a novel approach to treat this disorder. In this review we consider the current knowledge on the mechanisms of action, specificity, safety, and efficacy of the above mAbs as prophylactic antimigraine agents, and examine the possible adverse events that these agents may trigger. Antimigraine mAbs act as direct scavengers of CGRP (galcanezumab, fremanezumab, and eptinezumab) or against the CGRP receptor (erenumab). Due to their long half-lives, these molecules have revolutionized the prophylactic treatment of this neurovascular disorder. Moreover, because of their physicochemical properties, these agents are hepato-friendly and do not cross the blood-brain barrier (highlighting the relevance of peripheral mechanisms in migraine). Nevertheless, apart from potential cardiovascular side effects, the interaction with AMY₁ receptors and immunogenicity induced by autoantibodies against mAbs could be a concern for the safety of long-term treatment with these molecules.

The locus of Action of CGRPergic Monoclonal Antibodies Against Migraine: Peripheral Over Central Mechanisms

Migraine is a complex neurovascular disorder characterized by attacks of moderate to severe unilateral headache, accompanied by photophobia among other neurological signs. Although an arsenal of antimigraine agents is currently available in the market, not all patients respond to them. As Calcitonin Gene-Related Peptide (CGRP) plays a key role in the pathophysiology of migraine, CGRP receptor antagonists (gepants) have been developed. Unfortunately, further pharmaceutical development (for olcegepant and telcagepant) was interrupted due to pharmacokinetic issues observed during the Randomized Clinical Trials (RCT). On this basis, the use of monoclonal antibodies (mAbs; immunoglobulins) against CGRP or its receptor has recently emerged as a novel pharmacotherapy to treat migraines. RCT showed that these mAbs are effective against migraines producing fewer adverse events. Presently, the U.S. Food and Drug Administration approved four mAbs, namely: (i) erenumab; (ii) fremanezumab; (iii) galcanezumab; and (iv) eptinezumab. In general, specific antimigraine compounds exert their action in the trigeminovascular system, but the locus of action (peripheral vs. central) of the mAbs remains elusive. Since these mAbs have a molecular weight of ∼150 kDa, some studies rule out the relevance of their central actions as they seem unlikely to cross the Blood-Brain Barrier (BBB). Considering the therapeutic relevance of this new class of antimigraine compounds, the present review has attempted to summarize and discuss the current evidence on the probable sites of action of these mAbs.

Biological and small molecule strategies in migraine therapy with relation to the calcitonin gene-related peptide family of peptides

Migraine is one of the most common of neurological disorders with a global prevalence of up to 15%. One in five migraineurs have frequent episodic or chronic migraine requiring prophylactic treatment. In recent years, specific pharmacological treatments targeting calcitonin gene-related peptide (CGRP) signalling molecules have provided safe and effective treatments, monoclonal antibodies for prophylaxis and gepants for acute therapy. Albeit beneficial, it is important to understand the molecular mechanisms of these new drugs to better understand migraine pathophysiology and improve therapy. Here, we describe current views on the role of the CGRP family of peptides - CGRP, calcitonin, adrenomedullin, amylin - and their receptors in the trigeminovascular system. All these molecules are present within the trigeminovascular system but differ in expression and localization. It is likely that they have different roles, which can be utilized in providing additional drug targets.

CGRP-dependent signalling pathways involved in mouse models of GTN- cilostazol- and levcromakalim-induced migraine

BACKGROUND

Knowledge of exact signalling events during migraine attacks is lacking. Various substances are known to trigger migraine attacks in patients and calcitonin gene-related peptide antagonising drugs are effective against migraine pain. Here, we investigated the signalling pathways involved in three different mouse models of provoked migraine and relate them to calcitonin gene-related peptide and other migraine-relevant targets.

METHODS

In vivo mouse models of glyceryl trinitrate-, cilostazol- and levcromakalim-induced migraine were applied utilising tactile sensitivity to von Frey filaments as measuring readout. Signalling pathways involved in the three models were dissected by use of specific knockout mice and chemical inhibitors. In vivo results were supported by ex vivo wire myograph experiments measuring arterial dilatory responses and ex vivo calcitonin gene-related peptide release from trigeminal ganglion and trigeminal nucleus caudalis from mice.

RESULTS

Glyceryl trinitrate-induced hypersensitivity was dependent on both prostaglandins and transient receptor potential cation channel, subfamily A, member 1, whereas cilostazol- and levcromakalim-induced hypersensitivity were independent of both. All three migraine triggers activated calcitonin gene-related peptide signalling, as both receptor antagonism and antibody neutralisation of calcitonin gene-related peptide were effective inhibitors of hypersensitivity in all three models. Stimulation of trigeminal ganglia and brain stem tissue samples with cilostazol and levcromakalim did not result in release of calcitonin gene-related peptide, and vasodilation following levcromakalim stimulation was independent of CGRP receptor antagonism.

CONCLUSION

The mouse models of glyceryl trinitrate-, cilostazol- and levcromakalim- induced migraine all involve calcitonin gene-related peptide signalling in a complex interplay between different cell/tissue types. These models are useful in the study of migraine mechanisms.

The neurobiology of cluster headache

Cluster headache is a primary headache form occurring in paroxysmal excruciatingly severe unilateral head pain attacks usually grouped in periods lasting 1-2months, the cluster periods. A genetic component is suggested by the familial occurrence of the disease but a genetic linkage is yet to be identified. Contemporary activation of trigeminal and cranial parasympathetic systems-the so-called trigemino-parasympathetic reflex-during the headache attacks seem to cause the pain and accompanying oculo-facial autonomic phenomena respectively. At peripheral level, the increased calcitonin gene related peptide (CGRP) plasma levels suggests trigeminal system activation during cluster headache attacks. The temporal pattern of the disease both in terms of circadian rhythmicity and seasonal recurrence has suggested involvement of the hypothalamic biological clock in the pathophysiology of cluster headache. The posterior hypothalamus was investigate as the cluster generator leading to activation of the trigemino-parasympathetic reflex, but the accumulated experience after 20 years of hypothalamic electrical stimulation to treat the condition indicate that this brain region rather acts as pain modulator. Efficacy of monoclonal antibodies to treat episodic cluster headache points to a key role of CGRP in the pathophysiology of the condition.

Cluster headache pathophysiology - insights from current and emerging treatments

Cluster headache is a debilitating primary headache disorder that affects approximately 0.1% of the population worldwide. Cluster headache attacks involve severe unilateral pain in the trigeminal distribution together with ipsilateral cranial autonomic features and a sense of agitation. Acute treatments are available and are effective in just over half of the patients. Until recently, preventive medications were borrowed from non-headache indications, so management of cluster headache is challenging. However, as our understanding of cluster headache pathophysiology has evolved on the basis of key bench and neuroimaging studies, crucial neuropeptides and brain structures have been identified as emerging treatment targets. In this Review, we provide an overview of what is known about the pathophysiology of cluster headache and discuss the existing treatment options and their mechanisms of action. Existing acute treatments include triptans and high-flow oxygen, interim treatment options include corticosteroids in oral form or for greater occipital nerve block, and preventive treatments include verapamil, lithium, melatonin and topiramate. We also consider emerging treatment options, including calcitonin gene-related peptide antibodies, non-invasive vagus nerve stimulation, sphenopalatine ganglion stimulation and somatostatin receptor agonists, discuss how evidence from trials of these emerging treatments provides insights into the pathophysiology of cluster headache and highlight areas for future research.

Increase in trigeminal ganglion neurons that respond to both calcitonin gene-related peptide and pituitary adenylate cyclase-activating polypeptide in mouse models of chronic migraine and posttraumatic headache

A large body of animal and human studies indicates that blocking peripheral calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) signaling pathways may prevent migraine episodes and reduce headache frequency. To investigate whether recurring migraine episodes alter the strength of CGRP and PACAP signaling in trigeminal ganglion (TG) neurons, we compared the number of TG neurons that respond to CGRP and to PACAP (CGRP-R and PACAP-R, respectively) under normal and chronic migraine-like conditions. In a mouse model of chronic migraine, repeated nitroglycerin (NTG) administration significantly increased the number of CGRP-R and PACAP-R neurons in TG but not dorsal root ganglia. In TG neurons that express endogenous αCGRP, repeated NTG led to a 7-fold increase in the number of neurons that respond to both CGRP and PACAP (CGRP-R&PACAP-R). Most of these neurons were unmyelinated C-fiber nociceptors. This suggests that a larger fraction of CGRP signaling in TG nociceptors may be mediated through the autocrine mechanism, and the release of endogenous αCGRP can be enhanced by both CGRP and PACAP signaling pathways under chronic migraine condition. The number of CGRP-R&PACAP-R TG neurons was also increased in a mouse model of posttraumatic headache (PTH). Interestingly, low-dose interleukin-2 treatment, which completely reverses chronic migraine-related and PTH-related behaviors in mouse models, also blocked the increase in both CGRP-R and PACAP-R TG neurons. Together, these results suggest that inhibition of both CGRP and PACAP signaling in TG neurons may be more effective in treating chronic migraine and PTH than targeting individual signaling pathways.

Double-Binding Botulinum Molecule with Reduced Muscle Paralysis: Evaluation in In Vitro and In Vivo Models of Migraine

With a prevalence of 15%, migraine is the most common neurological disorder and among the most disabling diseases, taking into account years lived with disability. Current oral medications for migraine show variable effects and are frequently associated with intolerable side effects, leading to the dissatisfaction of both patients and doctors. Injectable therapeutics, which include calcitonin gene-related peptide-targeting monoclonal antibodies and botulinum neurotoxin A (BoNT/A), provide a new paradigm for treatment of chronic migraine but are effective only in approximately 50% of subjects. Here, we investigated a novel engineered botulinum molecule with markedly reduced muscle paralyzing properties which could be beneficial for the treatment of migraine. This stapled botulinum molecule with duplicated binding domain-binary toxin-AA (BiTox/AA)-cleaves synaptosomal-associated protein 25 with a similar efficacy to BoNT/A in neurons; however, the paralyzing effect of BiTox/AA was 100 times less when compared to native BoNT/A following muscle injection. The performance of BiTox/AA was evaluated in cellular and animal models of migraine. BiTox/AA inhibited electrical nerve fiber activity in rat meningeal preparations while, in the trigeminovascular model, BiTox/AA raised electrical and mechanical stimulation thresholds in Aδ- and C-fiber nociceptors. In the rat glyceryl trinitrate (GTN) model, BiTox/AA proved effective in inhibiting GTN-induced hyperalgesia in the orofacial formalin test. We conclude that the engineered botulinum molecule provides a useful prototype for designing advanced future therapeutics for an improved efficacy in the treatment of migraine.

Drug profile: galcanezumab for prevention of cluster headache

Introduction: Cluster headache [CH] is a severely disabling trigeminal autonomic cephalalgia [TAC]. Approximately 1 in 1,000 adults are affected by CH. Calcitonin gene-related peptide [CGRP] is an important mediator in the pathophysiology of CH. Galcanezumab is a monoclonal antibody with an affinity for the CGRP peptide, FDA approved for the prevention of episodic CH. Areas covered: Search words queried were 'cluster headache,' 'cluster headache, and CGRP,' 'cluster headache, and galcanezumab.' Over 99 articles in Pubmed and prescribing information for galcanezumab were reviewed. Some of the data pertaining to CH trials with fremanezumab were reviewed using clinical trials.org. Expert opinion: Galcanezumab has shown benefit in decreasing the weekly frequency of CH attacks across week 1 through week 3 in patients with CH; 8.7 attacks in the galcanezumab group, as compared with 5.2 in the placebo group (95% confidence interval, 0.2 to 6.7; P = 0.04). It has a favorable risk-benefit ratio. The prevention of CH with CGRP inhibition represents a novel advance for a condition with a significant unmet need. The negative trial results of galcanezumab for chronic cluster headache [CCH] may be due to the refractory nature and sheds light on the critical need to investigate the underlying biology and therapeutic options.

Spinal neuron-glia-immune interaction in cross-organ sensitization

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), historically considered as regional gastrointestinal disorders with heightened colonic sensitivity, are increasingly recognized to have concurrent dysfunction of other visceral and somatic organs, such as urinary bladder hyperactivity, leg pain, and skin hypersensitivity. The interorgan sensory cross talk is, at large, termed "cross-organ sensitization." These organs, anatomically distant from one another, physiologically interlock through projecting their sensory information into dorsal root ganglia (DRG) and then the spinal cord for integrative processing. The fundamental question of how sensitization of colonic afferent neurons conveys nociceptive information to activate primary afferents that innervate distant organs remains ambiguous. In DRG, primary afferent neurons are surrounded by satellite glial cells (SGCs) and macrophage accumulation in response to signals of injury to form a neuron-glia-macrophage triad. Astrocytes and microglia are major resident nonneuronal cells in the spinal cord to interact, physically and chemically, with sensory synapses. Cumulative evidence gathered so far indicate the indispensable roles of paracrine/autocrine interactions among neurons, glial cells, and immune cells in sensory cross-activation. Dichotomizing afferents, sensory convergency in the spinal cord, spinal nerve comingling, and extensive sprouting of central axons of primary afferents each has significant roles in the process of cross-organ sensitization; however, more results are required to explain their functional contributions. DRG that are located outside the blood-brain barrier and reside upstream in the cascade of sensory flow from one organ to the other in cross-organ sensitization could be safer therapeutic targets to produce less central adverse effects.

Central effects of erenumab in migraine patients

Objective

To determine whether erenumab, a new monoclonal antibody to the calcitonin gene-related peptide (CGRP) receptor, exerts functional central effects in migraineurs by performing functional imaging scans on patients treated with erenumab.

Methods

We conducted an fMRI study on 27 patients with migraine using a well-established trigeminal nociceptive paradigm, examining patients before and 2 weeks after administration of the CGRP receptor antibody erenumab 70 mg.

Results

Comparing both visit days in all patients (n = 27) revealed that erenumab leads to a decrease in activation in the right thalamus (i.e., contralateral to the stimulated side), right middle temporal gyrus, right lingual gyrus, left operculum, and several clusters on both sides of the cerebellum. Furthermore, when responders (n = 9) and nonresponders (n = 8) of the respective same headache state were compared, we found a significant reduction of hypothalamic activation after the administration of erenumab in responders only (t = 4.78; contrast estimate 29.79 [90% confidence interval 19.53–40.05]). This finding of reduced hypothalamic activation was confirmed when absolute headache days was used as a regressor.

Interpretation

These findings suggest that erenumab may not be an exclusively peripheral migraine treatment but has additional central effects. Whether this is due to secondary changes after peripheral modulation of sensory input or indeed represents a direct central mode of action is discussed.

Adverse effects of erenumab on cerebral proliferative angiopathy: A case report

BACKGROUND

Cerebral proliferative angiopathy is a vascular malformation associated with compromised blood-brain barrier and with migraine-like headache. Treating blood-brain barrier-compromised patients with erenumab, an anti-calcitonin gene-related peptide receptor monoclonal antibody, may be risky.

CASE

We describe a case of a 22-year-old chronic migraine patient with cerebral proliferative angiopathy who presented to our hospital in status epilepticus 2 d after his first dose of erenumab. Serial magnetic resonance imaging (MRI) studies demonstrated progressive areas of diffusion restriction including the brain tissue adjacent to the cerebral proliferative angiopathy, bilateral white matter and hippocampi. His 6-month post-presentation magnetic resonance imaging was notable for white matter injury, encephalomalacia surrounding cerebral proliferative angiopathy and bilateral hippocampal sclerosis. He remains clinically affected with residual symptoms, including refractory epilepsy and cognitive deficits.

CONCLUSION

The evidence presented in this case supports further investigation into potential deleterious side effects of erenumab in patients with compromised blood-brain barrier, such as individuals with intracranial vascular malformations.

Vascular actions of peripheral CGRP in migraine-like photophobia in mice

BACKGROUND

Calcitonin gene-related peptide is recognized as a key player in migraine, yet the mechanisms and sites of calcitonin gene-related peptide action remain unknown. The efficacy of calcitonin gene-related peptide-blocking antibodies as preventative migraine drugs supports a peripheral site of action, such as the trigeminovasculature. Given the apparent disconnect between the importance of vasodilatory peptides in migraine and the prevailing opinion that vasodilation is an epiphenomenon, the goal of this study was to test whether vasodilation plays a role in calcitonin gene-related peptide-induced light aversive behavior in mice.

METHODS

Systemic mean arterial pressure and light aversive behavior were measured after intraperitoneal administration of calcitonin gene-related peptide and vasoactive intestinal peptide in wild-type CD1 mice. The functional significance of vasodilation was tested by co-administration of a vasoconstrictor (phenylephrine, endothelin-1, or caffeine) with calcitonin gene-related peptide to normalize blood pressure during the light aversion assay.

RESULTS

Both calcitonin gene-related peptide and vasoactive intestinal peptide induced light aversion that was associated with their effect on mean arterial pressure. Notably, vasoactive intestinal peptide caused relatively transient vasodilation and light aversion. Calcitonin gene-related peptide-induced light aversion was still observed even with normalized blood pressure. However, two of the agents, endothelin-1 and caffeine, did reduce the magnitude of light aversion.

CONCLUSION

We propose that perivascular calcitonin gene-related peptide causes light-aversive behavior in mice by both vasomotor and non-vasomotor mechanisms.

Reducing Episodic Cluster Headaches: Focus on Galcanezumab

The involvement of calcitonin gene-related peptide in migraine and cluster headache has led to the recent development of new therapies. Galcanezumab, a novel monoclonal antibody targeting the calcitonin gene-related peptide, is approved for the migraine prevention and has recently been tested for the prevention of cluster headache. Two clinical trials have been conducted to investigate the efficacy and safety of galcanezumab in episodic cluster headache and chronic cluster headache. While efficacy endpoints were not met in the chronic subtype, galcanezumab reduced the weekly frequency of attacks in patients with episodic cluster headaches. In both studies, the antibody was well tolerated. This review summarizes and critically reviews the available data regarding the rationale behind targeting the calcitonin gene-related peptide with galcanezumab for the prevention of cluster headache.

Galcanezumab for the prevention of cluster headache

INTRODUCTION

Cluster headache (CH) is among the worst painful conditions. The available therapies are scarce and not specific, leaving many patients unsatisfied because of poor efficacy and/or tolerability. Patients not responding to common treatments are offered semi-invasive and invasive procedures with uncertain results. Based on the current understanding of CH pathophysiology, new possible therapeutic approaches come from drugs interfering with Calcitonin Gene Related Peptide (CGRP).

AREAS COVERED

After summarizing the evidence for CGRP involvement in CH pathophysiology, we review the published literature (PubMed) and information (clinicaltrials.gov, EudraCT, EMA and FDA websites) regarding a novel anti-CGRP monoclonal antibody, Galcanezumab, its pharmacological properties, development, and evidence for the treatment of CH. Publications regarding other indications (migraine) are considered for completeness and safety/tolerability profile.

EXPERT OPINION

In one randomized clinical trial, Galcanezumab has proven to be effective and safe as a preventive treatment in episodic CH, with a favorable tolerability profile offering a potential new option in the therapeutic arsenal. Inefficacy of galcanezumab in chronic CH as well as the inefficacy of another monoclonal antibody against CGRP (fremanezumab) in both episodic and chronic CH question the scalability of the drug in CH management. Further, studies comparing galcanezumab to the current standard treatments are highly desirable.

Monoclonal antibodies blocking CGRP transmission: An update on their added value in migraine prevention

The avenue of effective migraine therapies blocking calcitonin gene-related peptide (CGRP) transmission is the successful outcome of 35 years of translational research. Developed after short-acting, the small antagonists of the CGRP receptor (the "gepants"), the monoclonal antibodies blocking CGRP or its receptor (CGRP/rec mAbs) have changed the paradigm in migraine treatment. Contrary to the classical acute medications like triptans or nonsteroidal anti-inflammatory drugs (NSAIDs) with a transient effect, they act for long durations exclusively in the peripheral portion of the trigeminovascular system and can thus be assimilated to a durable attack treatment, unlike the classical preventives that chiefly act upstream on the central facets of migraine pathophysiology. Randomized controlled trials (RCT) of eptinezumab, erenumab, fremanezumab and galcanezumab have included collectively several thousands of patients, making them the most extensively studied class of preventive migraine treatments. Their results clearly indicate that CGRP/rec mAbs are significantly superior to placebo and have been comprehensively reviewed by Dodick [Cephalalgia 2019;39(3):445-458]. In this review we will briefly summarize the placebo-subtracted outcomes and number-needed-to-treat (NNT) of these pivotal RCTs and analyze new and post-hoc studies published afterwards focusing on effect size, effect onset and sustainability, response in subgroups of patients, safety and tolerability, and cost-effectiveness. We will also summarize our limited real-world experience with one of the CGRP/rec mAbs. Although methodological differences and lack of direct comparative trials preclude any reliable comparison, the overall impression is that there are only minor differences in efficacy and tolerability profiles between the four monoclonals: the average placebo-subtracted 50% responder rates for reduction in migraine headaches are 21.4% in episodic migraine (NNTs: 4-5), 17.4% in chronic migraine (NNTs: 4-8). Patients with an improvement exceeding 50% are rare, chronic migraineurs with continuous headache are unlikely to be responders and migraine auras are not improved. The effect starts within the first week after administration and is quasi maximal at one month. It is sustained for long time periods and may last for several months after treatment termination. CGRP/rec mAbs are effective even after prior preventive treatment failures and in patients with medication overuse, but the effect size might be smaller. They significantly reduce disability and health care resource utilization. The adverse effect profile of CGRP/rec mAbs is close to that of placebo with few minor exceptions and despite concerns related to the safeguarding role of CGRP in ischemia, no treatment-related vascular adverse events have been reported to date. Putting the CGRP/rec mAbs in perspective with available preventive migraine drug treatments, their major advantage seems not to be chiefly their superior efficacy but their unprecedented efficacy over adverse event ratio. Regarding cost-effectiveness, preliminary pharmaco-economic analyses of erenumab suggest that it is cost-effective for chronic migraine compared to no treatment or to onabotulinumtoxinA, but likely not for episodic migraine unless attack frequency is high, indirect costs are considered and its price is lowered.