Early treatment with sumatriptan prevents PACAP38-induced migraine: A randomised clinical trial

Pituitary adenylate cyclase-activating polypeptide signalling as a therapeutic target in migraine

Migraine is a disabling neurological disorder that affects more than one billion people worldwide. The clinical presentation is characterized by recurrent headache attacks, which are often accompanied by photophobia, phonophobia, nausea and vomiting. Although the pathogenesis of migraine remains incompletely understood, mounting evidence suggests that specific signalling molecules are involved in the initiation and modulation of migraine attacks. These signalling molecules include pituitary adenylate cyclase-activating polypeptide (PACAP), a vasoactive peptide that is known to induce migraine attacks when administered by intravenous infusion to people with migraine. Discoveries linking PACAP to migraine pathogenesis have led to the development of drugs that target PACAP signalling, and a phase II trial has provided evidence that a monoclonal antibody against PACAP is effective for migraine prevention. In this Review, we explore the molecular and cellular mechanisms of PACAP signalling, shedding light on its role in the trigeminovascular system and migraine pathogenesis. We then discuss emerging therapeutic strategies that target PACAP signalling for the treatment of migraine and consider the research needed to translate the current knowledge into a treatment for migraine in the clinic.

Hallmarks of primary headache: part 1 - migraine

BACKGROUND AND AIM

Migraine is a common disabling conditions which, globally, affects 15.2% of the population. It is the second cause of health loss in terms of years lived with disability, the first among women. Despite being so common, it is poorly recognised and too often undertreated. Specialty centres and neurologists with specific expertise on headache disorders have the knowledge to provide specific care: however, those who do not regularly treat patients with migraine will benefit from a synopsis on the most relevant and updated information about this condition. This paper presents a comprehensive view on the hallmarks of migraine, from genetics and diagnostic markers, up to treatments and societal impact, and reports the elements that identify migraine specific features.

MAIN RESULTS

The most relevant hallmark of migraine is that it has common and individual features together. Besides the known clinical manifestations, migraine presentation is heterogeneous with regard to frequency of attacks, presence of aura, response to therapy, associated comorbidities or other symptoms, which likely reflect migraine heterogeneous genetic and molecular basis. The amount of therapies for acute and for prophylactic treatment is really wide, and one of the difficulties is with finding the best treatment for the single patient. In addition to this, patients carry out different daily life activities, and might show lifestyle habits which are not entirely adequate to manage migraine day by day. Education will be more and more important as a strategy of brain health promotion, because this will enable reducing the amount of subjects needing specialty care, thus leaving it to those who require it in reason of refractory condition or presence of comorbidities.

CONCLUSIONS

Recognizing the hallmarks of migraine and the features of single patients enables prescribing specific pharmacological and non-pharmacological treatments. Medical research on headaches today particularly suffers from the syndrome of single-disease approach, but it is important to have a cross-sectional and joint vision with other close specialties, in order to treat our patients with a comprehensive approach that a heterogeneous condition like migraine requires.

VPAC1 and VPAC2 receptors mediate tactile hindpaw hypersensitivity and carotid artery dilatation induced by PACAP38 in a migraine relevant mouse model

BACKGROUND

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide pivotal in migraine pathophysiology and is considered a promising new migraine drug target. Although intravenous PACAP triggers migraine attacks and a recent phase II trial with a PACAP-inhibiting antibody showed efficacy in migraine prevention, targeting the PACAP receptor PAC1 alone has been unsuccessful. The present study investigated the role of three PACAP receptors (PAC1, VPAC1 and VPAC2) in inducing migraine-relevant hypersensitivity in mice.

METHODS

Hindpaw hypersensitivity was induced by repeated PACAP38 injections. Tactile sensitivity responses were quantified using von Frey filaments in three knockout (KO) mouse strains, each lacking one of the PACAP-receptors (Ntotal = 160). Additionally, ex vivo wire myography was used to assess vasoactivity of the carotid artery, and gene expression of PACAP receptors was examined by qPCR.

RESULTS

PACAP38 induced hypersensitivity in WT controls (p < 0.01) that was diminished in VPAC1 and VPAC2 KO mice (p < 0.05). In contrast, PAC1 KO mice showed similar responses to WT controls (p > 0.05). Myograph experiments supported these findings showing diminished vasoactivity in VPAC1 and VPAC2 KO mice. We found no upregulation of the non-modified PACAP receptors in KO mice.

CONCLUSIONS

This study assessed all three PACAP receptors in a migraine mouse model and suggests a significant role of VPAC receptors in migraine pathophysiology. The lack of hypersensitivity reduction in PAC1 KO mice suggests the involvement of other PACAP receptors or compensatory mechanisms. The results indicate that targeting only individual PACAP receptors may not be an effective migraine treatment.

Pituitary cyclase-activating polypeptide targeted treatments for the treatment of primary headache disorders

OBJECTIVE

Migraine is a complex and disabling neurological disorder. Recent years have witnessed the development and emergence of novel treatments for the condition, namely those targeting calcitonin gene-related peptide (CGRP). However, there remains a substantial need for further treatments for those unresponsive to current therapies. Targeting pituitary adenylate cyclase-activating polypeptide (PACAP) as a possible therapeutic strategy in the primary headache disorders has gained interest over recent years.

METHODS

This review will summarize what we know about PACAP to date: its expression, receptors, roles in migraine and cluster headache biology, insights gained from preclinical and clinical models of migraine, and therapeutic scope.

RESULTS

PACAP shares homology with vasoactive intestinal polypeptide (VIP) and is one of several vasoactive neuropeptides along with CGRP and VIP, which has been implicated in migraine neurobiology. PACAP is widely expressed in areas of interest in migraine pathophysiology, such as the thalamus, trigeminal nucleus caudalis, and sphenopalatine ganglion. Preclinical evidence suggests a role for PACAP in trigeminovascular sensitization, while clinical evidence shows ictal release of PACAP in migraine and intravenous infusion of PACAP triggering attacks in susceptible individuals. PACAP leads to dural vasodilatation and secondary central phenomena via its binding to different G-protein-coupled receptors, and intracellular downstream effects through cyclic adenosine monophosphate (cAMP) and phosphokinase C (PKC). Targeting PACAP as a therapeutic strategy in headache has been explored using monoclonal antibodies developed against PACAP and against the PAC1 receptor, with initial positive results.

INTERPRETATION

Future clinical trials hold considerable promise for a new therapeutic approach using PACAP-targeted therapies in both migraine and cluster headache.

Erenumab for Treatment of Persistent Erythema and Flushing in Rosacea: A Nonrandomized Controlled Trial

Importance

Treatment of erythema and flushing in rosacea is challenging. Calcitonin gene-related peptide (CGRP) has been associated with the pathogenesis of rosacea, raising the possibility that inhibition of the CGRP pathway might improve certain features of the disease.

Objective

To examine the effectiveness, tolerability, and safety of erenumab, an anti-CGRP-receptor monoclonal antibody, for the treatment of rosacea-associated erythema and flushing.

Design, Setting, and Participants

This single-center, open-label, single-group, nonrandomized controlled trial was conducted between June 9, 2020, and May 11, 2021. Eligible participants included adults with rosacea with at least 15 days of either moderate to severe erythema and/or moderate to extreme flushing. No concomitant rosacea treatment was allowed throughout the study period. Visits took place at the Danish Headache Center, Copenhagen University Hospital, Rigshospitalet in Copenhagen, Denmark. Participants received 140 mg of erenumab subcutaneously every 4 weeks for 12 weeks. A safety follow-up visit was performed at week 20. Data analysis occurred from January 2023 to January 2024.

Intervention

140 mg of erenumab every 4 weeks for 12 weeks.

Main Outcomes and Measures

The primary outcome was mean change in the number of days with moderate to extreme flushing during weeks 9 through 12, compared with the 4-week run-in period (baseline). The mean change in number of days with moderate to severe erythema was a secondary outcome. Adverse events were recorded for participants who received at least 1 dose of erenumab. Differences in means were calculated with a paired t test.

Results

A total of 30 participants (mean [SD] age, 38.8 [13.1] years; 23 female [77%]; 7 male [23%]) were included, of whom 27 completed the 12-week study. The mean (SD) number of days with moderate to extreme flushing was reduced by -6.9 days (95% CI, -10.4 to -3.4 days; P < .001) from 23.6 (5.8) days at baseline. The mean (SD) number of days with moderate to severe erythema was reduced by -8.1 days (95% CI, -12.5 to -3.7 days; P < .001) from 15.2 (9.1) days at baseline. Adverse events included transient mild to moderate constipation (10 participants [33%]), transient worsening of flushing (4 participants [13%]), bloating (3 participants [10%]), and upper respiratory tract infections (3 participants [10%]), consistent with previous data. One participant discontinued the study due to a serious adverse event (hospital admission due to gallstones deemed unrelated to the study), and 2 participants withdrew consent due to lack of time.

Conclusions and Relevance

These findings suggest that erenumab might be effective in reducing rosacea-associated flushing and chronic erythema (participants generally tolerated the treatment well, which was consistent with previous data), and that CGRP-receptor inhibition holds potential in the treatment of erythema and flushing associated with rosacea. Larger randomized clinical trials are needed to confirm this finding.

Trial Registration

ClinicalTrials.gov Identifier: NCT04419259.

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.

Targeting the PACAP-38 pathway is an emerging therapeutic strategy for migraine prevention

INTRODUCTION

The pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38) has emerged as a key mediator of migraine pathogenesis. PACAP-38 and its receptors are predominantly distributed in arteries, sensory and parasympathetic neurons of the trigeminovascular system. Phase 2 trials have tested human monoclonal antibodies designed to bind and inhibit PACAP-38 and the pituitary adenylate cyclase-activating polypeptide type I (PAC1) receptor for migraine prevention.

AREAS COVERED

This review focuses on the significance of the PACAP-38 pathway as a target in migraine prevention. English peer-reviewed articles were searched in PubMed, Scopus and ClinicalTrials.gov electronic databases.

EXPERT OPINION

A PAC1 receptor monoclonal antibody was not effective for preventing migraine in a proof-of-concept trial, paving the way for alternative strategies to be considered. Lu AG09222 is a humanized monoclonal antibody targeting PACAP-38 that was effective in preventing physiological responses of PACAP38 and reducing monthly migraine days in individuals with migraine. Further studies are necessary to elucidate the clinical utility, long-term safety and cost-effectiveness of therapies targeting the PACAP pathway.

Towards precision medicine in migraine: Recent therapeutic advances and potential biomarkers to understand heterogeneity and treatment response

After 35 years since the introduction of the International Classification of Headache Disorders (ICHD), we are living in the era of the second great revolution in migraine therapies. First, discoveries of triptans provided a breakthrough in acute migraine treatment utilizing bench-to-bedside research results on the role of serotonin in migraine. Next, the discovery of the role of neuropeptides, more specifically calcitonin gene-related peptide (CGRP) in migraine attack led to the development of anti-CGRP therapies that are effective both in acute and preventive treatment, and are also able to reduce migraine-related burden. Here, we reviewed the most recent clinical studies and real-world data on available migraine-specific medications, including triptans, ditants, gepants and anti-CGRP monoclonal antibodies. Novel drug targets, such as PACAP and amylins were also discussed. To address the main challenges of migraine therapy, the high heterogeneity of people with migraine, the prevalent presence of various comorbid disorders, and the insufficient medical care of migraine patients were covered. Promising novel approaches from the fields of omics, blood and saliva biomarker, imaging and provocation studies might bring solutions for these challenges with the potential to identify further drug targets, distinguish more homogeneous patient subgroups, contribute to more optimal drug selection strategies, and detect biomarkers in association with headache features or predicting treatment efficacy. In the future, the combined analysis of data of different biomarker modalities with machine learning algorithms may serve precision medicine in migraine treatment.

The functional heterogeneity of PACAP: Stress, learning, and pathology

Pituitary adenylate cyclase-activating peptide (PACAP) is a highly conserved and widely expressed neuropeptide that has emerged as a key regulator of multiple neural and behavioral processes. PACAP systems, including the various PACAP receptor subtypes, have been implicated in neural circuits of learning and memory, stress, emotion, feeding, and pain. Dysregulation within these PACAP systems may play key roles in the etiology of pathological states associated with these circuits, and PACAP function has been implicated in stress-related psychopathology, feeding and metabolic disorders, and migraine. Accordingly, central PACAP systems may represent important therapeutic targets; however, substantial heterogeneity in PACAP systems related to the distribution of multiple PACAP isoforms across multiple brain regions, as well as multiple receptor subtypes with several isoforms, signaling pathways, and brain distributions, provides both challenges and opportunities for the development of new clinically-relevant strategies to target the PACAP system in health and disease. Here we review the heterogeneity of central PACAP systems, as well as the data implicating PACAP systems in clinically-relevant behavioral processes, with a particular focus on the considerable evidence implicating a role of PACAP in stress responding and learning and memory. We also review data suggesting that there are sex differences in PACAP function and its interactions with sex hormones. Finally, we discuss both the challenges and promise of harnessing the PACAP system in the development of new therapeutic avenues and highlight PACAP systems for their critical role in health and disease.

Migraine Treatment: Towards New Pharmacological Targets

Migraine is a debilitating neurological condition affecting millions of people worldwide. Until a few years ago, preventive migraine treatments were based on molecules with pleiotropic targets, developed for other indications, and discovered by serendipity to be effective in migraine prevention, although often burdened by tolerability issues leading to low adherence. However, the progresses in unravelling the migraine pathophysiology allowed identifying novel putative targets as calcitonin gene-related peptide (CGRP). Nevertheless, despite the revolution brought by CGRP monoclonal antibodies and gepants, a significant percentage of patients still remains burdened by an unsatisfactory response, suggesting that other pathways may play a critical role, with an extent of involvement varying among different migraine patients. Specifically, neuropeptides of the CGRP family, such as adrenomedullin and amylin; molecules of the secretin family, such as pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP); receptors, such as transient receptor potential (TRP) channels; intracellular downstream determinants, such as potassium channels, but also the opioid system and the purinergic pathway, have been suggested to be involved in migraine pathophysiology. The present review provides an overview of these pathways, highlighting, based on preclinical and clinical evidence, as well as provocative studies, their potential role as future targets for migraine preventive treatment.

Molecular Mechanisms of Migraine: Nitric Oxide Synthase and Neuropeptides

Migraine is a common condition with disabling attacks that burdens people in the prime of their working lives. Despite years of research into migraine pathophysiology and therapeutics, much remains to be learned about the mechanisms at play in this complex neurovascular condition. Additionally, there remains a relative paucity of specific and targeted therapies available. Many sufferers remain underserved by currently available broad action preventive strategies, which are also complicated by poor tolerance and adverse effects. The development of preclinical migraine models in the laboratory, and the advances in human experimental migraine provocation, have led to the identification of key molecules likely involved in the molecular circuity of migraine, and have provided novel therapeutic targets. Importantly, the identification that vasoconstriction is neither necessary nor required for headache abortion has changed the landscape of migraine treatment and has broadened the therapy targets for patients with vascular risk factors or vascular disease. These targets include nitric oxide synthase (NOS) and several neuropeptides that are involved in migraine. The ability of NO donors and infusion of some of these peptides into humans to trigger typical migraine-like attacks has supported the development of targeted therapies against these molecules. Some of these, such as those targeting calcitonin gene-related peptide (CGRP), have already reached clinical practice and are displaying a positive outcome in migraineurs for the better by offering targeted efficacy without significant adverse effects. Others, such as those targeting pituitary adenylate cyclase activating polypeptide (PACAP), are showing promise and are likely to enter phase 3 clinical trials in the near future. Understanding these nitrergic and peptidergic mechanisms in migraine and their interactions is likely to lead to further therapeutic strategies for migraine in the future.

Future targets for migraine treatment beyond CGRP

BACKGROUND

Migraine is a disabling and chronic neurovascular headache disorder. Trigeminal vascular activation and release of calcitonin gene-related peptide (CGRP) play a pivotal role in the pathogenesis of migraine. This knowledge has led to the development of CGRP(-receptor) therapies. Yet, a substantial proportion of patients do not respond to these treatments. Therefore, alternative targets for future therapies are warranted. The current narrative review provides a comprehensive overview of the pathophysiological role of these possible non-CGRP targets in migraine.

FINDINGS

We covered targets of the metabotropic receptors (pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), amylin, and adrenomedullin), intracellular targets (nitric oxide (NO), phosphodiesterase-3 (PDE3) and -5 (PDE5)), and ion channels (potassium, calcium, transient receptor potential (TRP), and acid-sensing ion channels (ASIC)). The majority of non-CGRP targets were able to induce migraine-like attacks, except for (i) calcium channels, as it is not yet possible to directly target channels to elucidate their precise involvement in migraine; (ii) TRP channels, activation of which can induce non-migraine headache; and (iii) ASICs, as their potential in inducing migraine attacks has not been investigated thus far. Drugs that target its receptors exist for PACAP, NO, and the potassium, TRP, and ASIC channels. No selective drugs exist for the other targets, however, some existing (migraine) treatments appear to indirectly antagonize responses to amylin, adrenomedullin, and calcium channels. Drugs against PACAP, NO, potassium channels, TRP channels, and only a PAC₁ antibody have been tested for migraine treatment, albeit with ambiguous results.

CONCLUSION

While current research on these non-CGRP drug targets has not yet led to the development of efficacious therapies, human provocation studies using these targets have provided valuable insight into underlying mechanisms of migraine headaches and auras. Further studies are needed on these alternative therapies in non-responders of CGRP(-receptor) targeted therapies with the ultimate aim to pave the way towards a headache-free future for all migraine patients.

The effect of Lu AG09222 on PACAP38- and VIP-induced vasodilation, heart rate increase, and headache in healthy subjects: an interventional, randomized, double-blind, parallel-group, placebo-controlled study

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide (PACAP), structurally related to vasoactive intestinal peptide (VIP), is one of the important mediators in the pathogenesis of migraine and is known to dilate cranial arteries and induce headache and migraine. Our objective was to determine whether Lu AG09222-an investigational humanized monoclonal antibody directed against PACAP ligand-would inhibit the PACAP-signaling cascade by abolishing its vasodilatory and headache-inducing abilities.

METHODS

In a randomized, double-blind, parallel-group, single-dose, placebo-controlled study of Lu AG09222, healthy volunteers aged 18-45 years without history of headache disorders were randomly allocated to three treatment sequences (1:2:2) on two experimental infusion visits with 9 ± 3 days' interval: placebo + saline + saline (n = 5), placebo + PACAP38 + VIP (n = 10), and Lu AG09222 + PACAP38 + VIP (n = 10). The primary outcome measure was area under the curve (AUC) of the change in superficial temporal artery (STA) diameter from 0 to 120 min after start of infusion of PACAP38. The study was conducted at the Danish Headache Center in Copenhagen, Denmark.

RESULTS

In participants who received Lu AG09222 + PACAP38 infusion, there was a significantly lower STA diameter (mean (SE) [95% CI] AUC ‒35.4 (4.32) [‒44.6, ‒26.3] mm × min; P < 0.0001) compared to participants who received placebo + PACAP38 infusion. Secondary and explorative analysis revealed that PACAP38 infusion induced an increase in facial blood flow, heart rate and mild headache, and indicated that these PACAP38-induced responses were inhibited by Lu AG09222.

CONCLUSIONS

This proof-of-mechanism study demonstrated that Lu AG09222 inhibited PACAP38-induced cephalic vasodilation and increases in heart rate, and reduced concomitant headache. Lu AG09222 may be a potential therapy against migraine and other PACAP-mediated diseases.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04976309. Registration date: July 19, 2021.

Shared and independent roles of CGRP and PACAP in migraine pathophysiology

The neuropeptides calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) have emerged as mediators of migraine pathogenesis. Both are vasodilatory peptides that can cause migraine-like attacks when infused into people and migraine-like symptoms when injected into rodents. In this narrative review, we compare the similarities and differences between the peptides in both their clinical and preclinical migraine actions. A notable clinical difference is that PACAP, but not CGRP, causes premonitory-like symptoms in patients. Both peptides are found in distinct, but overlapping areas relevant to migraine, most notably with the prevalence of CGRP in trigeminal ganglia and PACAP in sphenopalatine ganglia. In rodents, the two peptides share activities, including vasodilation, neurogenic inflammation, and nociception. Most strikingly, CGRP and PACAP cause similar migraine-like symptoms in rodents that are manifested as light aversion and tactile allodynia. Yet, the peptides appear to act by independent mechanisms possibly by distinct intracellular signaling pathways. The complexity of these signaling pathways is magnified by the existence of multiple CGRP and PACAP receptors that may contribute to migraine pathogenesis. Based on these differences, we suggest PACAP and its receptors provide a rich set of targets to complement and augment the current CGRP-based migraine therapeutics.

Role of PACAP in migraine: An alternative to CGRP?

Migraine is a widespread and debilitating neurological condition affecting more than a billion people worldwide. Thus, more effective migraine therapies are highly needed. In the last decade, two endogenous neuropeptides, calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating peptide (PACAP), were identified to be implicated in migraine. Recently, introduction of monoclonal antibodies (mAbs) blocking the CGRP is the most important advance in migraine therapy for decades. However, 40% of patients are unresponsive to these new drugs. We believe that PACAP may be involved in these patients. Like CGRP, PACAP is located to sensory nerve fibers, it dilates cranial arteries, it causes migraine when infused into patients and it is a peptide that lends itself to antibody therapy. Also, recent studies suggest that the PACAP pathway is independent of the CGRP pathway. Understanding the signaling pathways of PACAP may therefore lead to identification of novel therapeutic targets of particular interest in patients unresponsive to anti-CGRP therapy. Accordingly, neutralizing mAb to PACAP is currently in clinical phase II development. The aim of the present review is, therefore, to give a thorough account of the existing data on PACAP, its receptors and its relation to migraine.

PACAP signaling is not involved in GTN- and levcromakalim-induced hypersensitivity in mouse models of migraine

BACKGROUND

Calcitonin gene-related peptide (CGRP) antagonizing drugs represents the most important advance in migraine therapy for decades. However, these new drugs are only effective in 50-60% of patients. Recent studies have shown that the pituitary adenylate cyclase-activating peptide (PACAP38) pathway is independent from the CGRP signaling pathway. Here, we investigate PACAP38 signaling pathways in relation to glyceryl trinitrate (GTN), levcromakalim and sumatriptan.

METHODS

In vivo mouse models of PACAP38-, GTN-, and levcromakalim-induced migraine were applied using tactile sensitivity to von Frey filaments as measuring readout. Signaling pathways involved in the three models were dissected using PACAP-inhibiting antibodies (mAbs) and sumatriptan.

RESULTS

We showed that PACAP mAbs block PACAP38 induced hypersensitivity, but not via signaling pathways involved in GTN and levcromakalim. Also, sumatriptan has no effect on PACAP38-induced hypersensitivity relevant to migraine. This is the first study testing the effect of a PACAP-inhibiting drug on GTN- and levcromakalim-induced hypersensitivity.

CONCLUSIONS

Based on the findings in our mouse model of migraine using migraine-inducing compounds and anti-migraine drugs, we suggest that PACAP acts via a distinct pathway. Using PACAP38 antagonism may be a novel therapeutic target of interest in a subgroup of migraine patients who do not respond to existing therapies.

Calcitonin Gene-Related Peptide (CGRP) and Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) in Migraine Pathogenesis

Migraine is a prevalent and debilitating neurologic disorder. Advancements in understanding the underlying pathophysiological mechanisms are spearheading the effort to introduce disease-specific treatment options. In recent years this effort has largely focused on alteration of endogenous neuropeptide signaling, namely the peptides calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Human studies into the pathophysiological underpinnings of CGRP and PACAP in migraine are manifold and here we review the works investigating these neuropeptides in patients suffering from migraine in order to elucidate the background for developing new treatment options for this vastly disabling disorder.

Provoked versus spontaneous migraine attacks: pathophysiological similarities and differences

BACKGROUND

The onset and duration of spontaneous migraine attacks are most often difficult to predict which, in turn, makes it challenging to study the neurobiologic underpinnings of the disease in a controlled experimental setting. To address this challenge, human provocation studies can be used to identify signaling molecules (e.g. calcitonin gene-related peptide, pituitary adenylate cyclase-activating polypeptide) that, upon intravenous or oral administration, induce migraine attacks in people with migraine and mild or no headache in healthy volunteers. This approach has proven to be valid for decades and plays an integral role in mapping signaling pathways underlying migraine pathogenesis and identification of novel drug targets. However, the question arises as to whether the pathogenic mechanisms of provoked and spontaneous migraine attacks differ. In this paper, we provide an opinionated discussion on the similarities and differences between provoked and spontaneous attacks based on the current understanding of migraine pathogenesis.

METHODS

The PubMed database was searched in July 2022 for original research articles on human provocation studies that included participants with migraine. The reference lists of originally identified articles were also searched and we selected those we judged relevant.

DISCUSSION

People with migraine describe that provoked attacks resemble their spontaneous attacks and can be treated with their usual rescue medication. From a neurobiologic standpoint, provoked and spontaneous migraine attacks appear to be similar, except for the source of migraine-inducing substances (exogenous vs. endogenous source). In addition, provoked attacks can likely not be used to study the events that precede the release of migraine-inducing signaling molecules from sensory afferents and/or parasympathetic efferents during spontaneous attacks.

Effect of KATP channel blocker glibenclamide on PACAP38-induced headache and hemodynamic

OBJECTIVE

To determine whether glibenclamide, a non-selective adenosine 5'-triphosphate-sensitive K⁺ (K_ATP) channel blocker, attenuates pituitary adenylate cyclase-activating polypeptide-38 (PACAP38)-induced headache and vascular changes in healthy volunteers.

METHODS

In a double-blind, randomized, placebo controlled and crossover design, 22 healthy volunteers were assigned to receive an intravenous infusion of 10 picomole/kg/min pituitary adenylate cyclase-activating polypeptide-38 over 20 minutes followed by oral administration of 10 mg glibenclamide or placebo. The primary endpoint was the difference in incidence of headache (0-12 hours) between glibenclamide and placebo. The secondary endpoints were a difference in area under the curve for headache intensity scores, middle cerebral artery velocity (V_meanMCA), superficial temporal artery diameter, radial artery diameter, heart rate, mean arterial blood pressure and facial skin blood flow between the two study days.

RESULTS

Twenty participants completed the study. We found no difference in the incidence of pituitary adenylate cyclase-activating polypeptide-38-induced headache after glibenclamide (19/20, 95%) compared to placebo (18/20, 90%) (P = 0.698). The area under the curve for headache intensity, middle cerebral artery velocity, superficial temporal artery diameter, radial artery diameter, facial skin blood flow, heart rate and mean arterial blood pressure did not differ between pituitary adenylate cyclase-activating polypeptide-38-glibenclamide day compared to pituitary adenylate cyclase-activating polypeptide-38-placebo day (P > 0.05).

CONCLUSIONS

Posttreatment with 5'-triphosphate-sensitive K₊ channel inhibitor glibenclamide did not attenuate pituitary adenylate cyclase-activating polypeptide-38-induced headache and hemodynamic changes in healthy volunteers. We suggest that pituitary adenylate cyclase-activating polypeptide-38-triggered signaling pathway could be mediated by specific isoforms of sulfonylurea receptor subunits of 5'-triphosphate-sensitive K₊ channels and other types of potassium channels.

Migraine and light: A narrative review

OBJECTIVE

In this narrative review, we summarize clinical and experimental data on the effect of light in migraine and discuss future prospects.

BACKGROUND

Effective nonpharmacological treatment of hypersensitivity to light in migraine is an unmet clinical need. Current management strategies primarily consist of seeking a dark room and avoiding light exposure. Advances in the past 2 decades have improved our understanding of the underlying pathophysiology of how migraine is influenced by light. This may provide promising avenues for novel approaches in clinical management.

METHODS

We searched MEDLINE for articles published from database inception up to September 1, 2021. We used the search term "migraine" with the search terms "light," "photophobia," "treatment," "trigger," "circadian rhythm," "environment," and/or "pathophysiology."

RESULTS

Light is commonly reported as a trigger factor of migraine attacks, however, early manifestation of photophobia and false attribution is likely the actual cause based on data deriving from retrospective, prospective, and experimental studies. The most common photophobia symptoms in migraine are exacerbation of headache by light and abnormal sensitivity to light with the underlying neural pathways likely being dependent on ongoing activity in the trigeminovascular system. Clinical studies and experimental models have identified mediators of photophobia and uncovered narrow wavebands of the light spectrum that may reduce pain intensity during a migraine attack. Consequently, novel devices have undergone exploratory clinical trials with promising results.

CONCLUSION

False attribution is likely the reason why light is commonly reported as a trigger factor of migraine attacks, and a prospective confirmation is required to prevent unnecessary avoidance. The observation that individuals with migraine are not equally photophobic to all wavebands of the light spectrum opens the potential for innovative pain management strategies. In this context, using human-centric lighting (also called integrative lighting) to mimic the natural daylight cycle and avoid harmful wavebands through modern technology may prove beneficial. Future research should identify direct and indirect consequences of light and other environmental factors in migraine to fill out knowledge gaps and enable evidence-based care strategies within institutions, work environments, and other settings.

Future prophylactic treatments in migraine: Beyond anti-CGRP monoclonal antibodies and gepants

Migraine is ranked as a leading cause of years lived with disability among all neurological disorders. Therapies targeting the calcitonin gene-related peptide (CGRP) signaling pathway, including monoclonal antibodies against the receptor or ligand and small molecule CGRP receptor antagonists (gepants), are today approved for migraine prophylaxis with additional compounds expected to be introduced to the market soon. In this review, we consider other putative prophylactic migraine drugs in development, including compounds targeting G-protein coupled receptors, glutamate, ion channels, and neuromodulatory devices. Emergence of these new interventions could complement our current treatment armamentarium for migraine management.

Infusion of Pituitary Adenylate Cyclase-Activating Polypeptide-38 in Patients with Rosacea Induces Flushing and Facial Edema that Can Be Attenuated by Sumatriptan

BACKGROUND

The pathogenesis of rosacea is incompletely understood. Signaling neuropeptides, including PACAP, a regulator of vasodilation and edema, are upregulated in rosacea skin. Here, we evaluated PACAP38-induced rosacea features and examined whether a 5-HT_1B/1D receptor agonist could reduce these features.

METHODS

A total of 35 patients with erythematotelangiectatic rosacea received an intravenous infusion of 10 pmol/kg/minute of PACAP38 followed by an intravenous infusion of 4 mg sumatriptan or placebo (saline) on two study days in a double-blind, randomized, placebo-controlled, and cross-over trial.

RESULTS

PACAP38 increased facial skin blood flow by 90%, dilated the superficial temporal artery by 56%, and induced prolonged flushing and facial edema. Compared with placebo, sumatriptan reduced PACAP38-induced facial skin blood flow for 50 minutes (P = 0.023), constricted the superficial temporal artery for 80 minutes (P = 0.010), and reduced duration of flushing (P = 0.001) and facial edema (P < 0.001).

CONCLUSIONS

We established a clinical experimental model of rosacea features and showed that sumatriptan was able to attenuate PACAP38-induced rosacea flushing and edema. Findings support a key role of PACAP38 in rosacea flushing pathogenesis. It remains unknown whether PACAP38 inhibition can improve rosacea.

TRIAL REGISTER

The trial was registered at ClinicalTrials.govNCT03878784 in March 2019.