CGRP and its receptors

Evidence-based review and frontiers of migraine therapy

BACKGROUND

Cyclic vomiting syndrome (CVS) is identified as one of the "episodic syndromes that may be associated with migraine," along with benign paroxysmal torticollis, benign paroxysmal vertigo, and abdominal migraine. It has been proposed that CVS and migraine may share pathophysiologic mechanisms of hypothalamic activation and altered dopaminergic signaling, and impaired sensorimotor intrinsic connectivity. The past decade has brought groundbreaking advances in the treatment of migraine and other headache disorders. While many of these therapies have yet to be studied in episodic syndromes associated with migraine including CVS and abdominal migraine, the potential shared pathophysiology among these conditions suggests that use of migraine-specific treatments may have a beneficial role even in those for whom headache is not the primary symptom.

PURPOSE

This manuscript highlights newer therapies in migraine. Calcitonin gene-related peptide (CGRP) and its relation to migraine pathophysiology and the therapies that target the CGRP pathway, as well as a 5HT1F receptor agonist and neuromodulation devices used to treat migraine are briefly discussed as they may potentially prove to be useful in the future treatment of CVS.

Identification of novel signal of Raynaud's phenomenon with Calcitonin Gene-Related Peptide(CGRP) antagonists using data mining algorithms and network pharmacological approaches

BACKGROUND

Calcitonin gene-related peptide (CGRP) antagonists are recently approved for the treatment of migraine.

AIM

The main aim of the current study was to find out the association of CGRP antagonists with RP using data mining algorithms integrated with network pharmacological approaches.

RESEARCH DESIGN AND METHODS

The individual case safety reports were extracted using OpenVigil2.1-MedDRA-V17 (2004Q1-2022Q3), the United States Adverse Event Reporting System (US FAERS). The data mining algorithms i.e. reporting odds ratio (ROR) with 95% confidence and proportionality reporting ratio (PRR) with associated chi-square value were calculated along with a minimum of three ICSRs to identify the signal. Further, the network was constructed using Cytoscape 3.7.2. Finally, molecular docking was performed using Glide, Schrodinger Inc.

RESULTS

The PRR ≥2 with a linked chi-square value ≥4, add up of co-occurrence ≥3, and a lower limit of 95% confidence interval of ROR exceeding 2 indicates a positive signal of RP. Further, the network pharmacological and molecular docking results have shown the involvement of insulin-like growth factor 1-receptor (IGF1R) pathways.

CONCLUSION

The RP is recognized as a novel signal with all CGRP antagonists.

Effect of anti-CGRP-targeted therapy on migraine aura: Results of an observational case series study

INTRODUCTION

Limited clinical evidence is available regarding the potential effectiveness of anti-CGRP monoclonal antibodies for the preventive treatment of migraine with aura.

AIM OF THE STUDY

This observational study involved a series of migraine patients affected by either migraine with or without aura, who were investigated for any changes in their frequencies and their migraine aura attack characteristics observed during treatment with anti-CGRP Mabs over a 1-year period.

PATIENTS AND METHODS

Twelve migraine patients were included, seven of whom were treated with erenumab, 2 with fremanezumab, and 3 with galcanezumab. Clinical data were collected at baseline, which were defined as 3 months prior to the initiation of treatment, and thereafter at each trimester, over the 1-year treatment period. The parameters included the number of headache and migraine days/month, the frequency of aura episodes, the number of days with acute drug intakes/month, and the scores from the migraine disability status scale (MIDAS), and the Headache Impact Test 6 (HIT-6).

RESULTS

Anti-CGRP Mbs antibodies induced significant decreases in mean headache and migraine without aura days per month, the number of days with medication intake, as well as MIDAS and HIT-6 scores (p < 0.0001). In contrast, the anti-CGRP Mab treatment did not appear to impact the frequency of migraine with aura attacks but seemed to reduce both the intensity and the duration of headache phases of migraine aura. Furthermore, some migraine patients referred to having aura attacks without headache over the course of the treatment period.

CONCLUSIONS

Based on the above findings, we hypothesize that anti-CGRP Mabs did not influence neuronal and vascular events related to cortical spreading depression (CSD) which is considered the pathophysiological substrate of aura. Conversely, these antibodies are able to counteract, via their peripheral mechanisms of action, the sensitization of the trigemino-vascular pathway which is triggered by CSD. This aforementioned might explain why in our patients, migraine aura attacks remained unchanged in their frequencies, but the headache phases were either reduced or absent.

Novel FDA-approved zavegepant drug for treating migraine

Migraine is a complex neurological disorder characterized by recurring episodes of severe headaches. The pathophysiology of migraine involves abnormalities in neuronal networks, cortical spreading depression, and sensitization of trigeminovascular pathways. The global prevalence of migraine has increased substantially, warranting advancements in treatment strategies. A significant trigger in migraine pathophysiology is calcitonin gene-related peptide (CGRP). Several drugs, such as gepants and monoclonal antibodies (MABs) targeting CGRP or its receptor, have been developed to antagonize CGRP signaling. Zavegepant (Zavzpret), a novel CGRP receptor antagonist, has recently been approved by the FDA for the acute treatment of migraine. Clinical trials have demonstrated its efficacy in providing headache and symptom relief, with a statistically significant percentage of patients achieving freedom from headaches and most bothersome symptoms. Despite mild adverse effects, such as taste disorders and nausea, Zavzpret's overall safety profile remains acceptable.

Characteristics associated with response to subcutaneously administered anti-CGRP monoclonal antibody medications in a real-world community cohort of persons living with migraine: A retrospective clinical and genetic study

OBJECTIVE

To evaluate response to anti-calcitonin gene-related peptide (CGRP) migraine preventives in a real-world community cohort of persons living with migraine and to identify clinical and genetic characteristics associated with efficacious response.

BACKGROUND

Erenumab-aooeb, fremanezumab-vrfm, and galcanezumab-gnlm target CGRP or its receptor; however, many patients are non-responsive.

METHODS

In this retrospective clinical and genetic study, we identified 1077 adult patients who satisfied the International Classification of Headache Disorders, 3rd edition, criteria for migraine without aura, migraine with aura, or chronic migraine and who were prescribed an anti-CGRP migraine preventive between May 2018 and May 2021. Screening of 558 patients identified 289 with data at baseline and first follow-up visits; data were available for 161 patients at a second follow-up visit. The primary outcome was migraine days per month (MDM). In 198 genotyped patients, we evaluated associations between responders (i.e., patients with ≥50% reduction in MDM at follow-up) and genes involved in CGRP signaling or pharmacological response, and genetic and polygenic risk scores.

RESULTS

The median time to first follow-up was 4.4 (0.9-22) months after preventive start. At the second follow-up, 5.7 (0.9-13) months later, 145 patients had continued on the same preventive. Preventives had strong, persistent effects in reducing MDM in responders (follow-up 1: η2  = 0.26, follow-up 2: η2  = 0.22). At the first but not second follow-up: galcanezumab had a larger effect than erenumab, while no difference was seen at either follow-up between galcanezumab and fremanezumab or fremanezumab and erenumab. The decrease in MDM at follow-up was generally proportional to baseline MDM, larger in females, and increased with months on medication. At the first follow-up only, patients with prior hospitalization for migraine or who had not responded to more preventive regimens had a smaller decrease in MDM. Reasons for stopping or switching a preventive varied between medications and were often related to cost and insurance coverage. At both follow-ups, patient tolerance (1: 92.2% [262/284]; 2: 95.2% [141/145]) and continued use (1: 77.5% [224/289]; 2: 80.6% [116/145]) were high and similar across preventives. Response consistency (always non-responders: 31.7% [46/145]; always responders: 56.5% [82/145], and one-time only responders: 11.7% [17/145]) was also similar across preventives. Non-responder status had nominally significant associations with rs12615320-G in RAMP1 (odds ratio [95% confidence interval]: 4.7 [1.5, 14.7]), and rs4680-A in COMT (0.6[0.4, 0.9]). Non-responders had a lower mean genetic risk score than responders (1.0 vs. 1.1; t(df) = -1.75(174.84), p = 0.041), and the fraction of responders increased with genetic and polygenic risk score percentile.

CONCLUSIONS

In this real-world setting, anti-CGRP preventives reduced MDM persistently and had similar and large effect sizes on MDM reduction; however, clinical and genetic factors influenced response.

The Anti-Calcitonin Gene-Related Peptide (Anti-CGRP) Antibody Fremanezumab Reduces Trigeminal Neurons Immunoreactive to CGRP and CGRP Receptor Components in Rats

Treatment with the anti-CGRP antibody fremanezumab is successful in the prevention of chronic and frequent episodic migraine. In preclinical rat experiments, fremanezumab has been shown to reduce calcitonin gene-related peptide (CGRP) release from trigeminal tissues and aversive behaviour to noxious facial stimuli, which are characteristic pathophysiological changes accompanying severe primary headaches. To further decipher the effects of fremanezumab that underlie these antinociceptive effects in rats, immunohistochemistry and ELISA techniques were used to analyse the content and concentration of CGRP in the trigeminal ganglion, as well as the ratio of trigeminal ganglion neurons which are immunoreactive to CGRP and CGRP receptor components, 1-10 days after subcutaneous injection of fremanezumab (30 mg/kg) compared to an isotype control antibody. After fremanezumab treatment, the fraction of trigeminal ganglion neurons which were immunoreactive to CGRP and the CGRP receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) was significantly lowered compared to the control. The content and concentration of CGRP in trigeminal ganglia were not significantly changed. A long-lasting reduction in CGRP receptors expressed in trigeminal afferents may contribute to the attenuation of CGRP signalling and antinociceptive effects of monoclonal anti-CGRP antibodies in rats.

Calcitonin gene-related peptide and its receptor plays important role in nociceptive regulation in the arcuate nucleus of hypothalamus of rats with inflammatory pain

The present study has explored the role of calcitonin gene-related peptide (CGRP) and its receptor in inflammatory pain modulation in arcuate nucleus of hypothalamus (ARC). Our study demonstrated that intra-ARC injection of CGRP induced antinociceptive effects to naïve rats and rats with inflammatory pain, the effect could be inhibited by the selective CGRP receptor antagonist CGRP8-37. Interestingly, the CGRP-induced antinociception effect was decreased in rats with inflammatory pain compared to naïve rats. Similarly, we found that calcitonin receptor like receptor (CLR), a main component of CGRP receptor, had a low decreased expression levels in the ARC regions of rats with inflammatory pain. The CGRP-induced antinociceptive effect was significantly impaired after reducing CLR expression by intra-ARC administration of CLR targeted siRNA. These findings demonstrated that CGRP might play a crucial role in nociceptive modulation in the ARC during inflammatory pain, which was mediated by CGRP receptor in the ARC. This study shed light upon CGRP and its receptor interaction might be valuable strategies for the alleviation of inflammatory pain.

Migraine drugs

According to recent studies, migraine affects more than 1 billion people worldwide, making it one of the world’s most prevalent diseases. Although this highly debilitating illness has been known since ancient times, the first therapeutic drugs to treat migraine, ergotamine (Gynergen) and dihydroergotamine (Dihydergot), did not appear on the market until 1921 and 1946, respectively. Both drugs originated from Sandoz, the world’s leading pharmaceutical company in ergot alkaloid research at the time. Historically, ergot alkaloids had been primarily used in obstetrics, but with methysergide (1-methyl-lysergic acid 1′-hydroxy-butyl-(2S)-amide), it became apparent that they also held some potential in migraine treatment. Methysergide was the first effective prophylactic drug developed specifically to prevent migraine attacks in 1959. On the basis of significantly improved knowledge of migraine pathophysiology and the discovery of serotonin and its receptors, Glaxo was able to launch sumatriptan in 1992. It was the first member from the class of triptans, which are selective 5-HT1B/1D receptor agonists. Recent innovations in acute and preventive migraine therapy include lasmiditan, a selective 5-HT1F receptor agonist from Eli Lilly, the gepants, which are calcitonin gene-related peptide (CGRP) receptor antagonists discovered at Merck & Co and BMS, and anti-CGRP/receptor monoclonal antibodies from Amgen, Pfizer, Eli Lilly, and others.

Graphical abstract

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.

Nutrition and Calcitonin Gene Related Peptide (CGRP) in Migraine

Targeting calcitonin gene-related peptide (CGRP) and its receptor by antibodies and antagonists was a breakthrough in migraine prevention and treatment. However, not all migraine patients respond to CGRP-based therapy and a fraction of those who respond complain of aliments mainly in the gastrointestinal tract. In addition, CGRP and migraine are associated with obesity and metabolic diseases, including diabetes. Therefore, CGRP may play an important role in the functioning of the gut-brain-microflora axis. CGRP secretion may be modulated by dietary compounds associated with the disruption of calcium signaling and upregulation of mitogen-activated kinase phosphatases 1 and 3. CGRP may display anorexigenic properties through induction of anorexigenic neuropeptides, such as cholecystokinin and/or inhibit orexigenic neuropeptides, such as neuropeptide Y and melanin-concentrating hormone CH, resulting in the suppression of food intake, functionally coupled to the activation of the hypothalamic 3',5'-cyclic adenosine monophosphate. The anorexigenic action of CGRP observed in animal studies may reflect its general potential to control appetite/satiety or general food intake. Therefore, dietary nutrients may modulate CGRP, and CGRP may modulate their intake. Therefore, anti-CGRP therapy should consider this mutual dependence to increase the efficacy of the therapy and reduce its unwanted side effects. This narrative review presents information on molecular aspects of the interaction between dietary nutrients and CGRP and their reported and prospective use to improve anti-CGRP therapy in migraine.

Involvement of the calcitonin gene-related peptide system in the modulation of inflamed uterus contractile function in pigs

This study analyzed severe acute endometritis action on myometrial density and distribution of protein gene product (PGP)9.5- and calcitonin gene-related peptide (CGRP)-like immunoreactive nerve fibers and calcitonin receptor-like receptor (CLR) expression, and on CGRP receptor (CGRPR) participation in uterine contractility in pigs. E. coli suspension (E. coli group) or saline (SAL group) were injected into the uteri, or only laparotomy was performed (CON group). In the E. coli group myometrium, a lack of significant changes in PGP9.5 and CGRP innervation patterns and increased CLR protein level were revealed. In all groups, compared to the pretreatment period, human αCGRP increased amplitude in the myometrium, while reducing it in endometrium/myometrium. In the E. coli group endometrium/myometrium, human αCGRP lowered amplitude vs other groups. Human αCGRP reduced frequency in CON and SAL groups and enhanced it in the E. coli group endometrium/myometrium. The frequency in E. coli group increased vs other groups. CGRPR antagonist, human αCGRP8-37, reversed (CON, SAL groups) and eliminated (E. coli group) the rise in human αCGRP-induced myometrial amplitude. In endometrium/myometrium, human αCGRP8-37 abolished (CON group) and reversed (SAL group) a decrease in frequency, and reduced the rise in frequency (E. coli group) caused by human αCGRP. Collectively, in the myometrium, endometritis did not change PGP9.5 and CGRP innervation patterns and enhanced CLR protein level. CGRPR also mediated in CGRP action on inflamed uterus contractility.

Evolution of calcitonin/calcitonin gene-related peptide family in chordates: Identification of CT/CGRP family peptides in cartilaginous fish genome

The calcitonin (CT)/CT gene-related peptide (CGRP) family is a peptide gene family that is widely found in bilaterians. CT, CGRP, adrenomedullin (AM), amylin (AMY), and CT receptor-stimulating peptide (CRSP) are members of the CT/CGRP family. In mammals, CT is involved in calcium homeostasis, while CGRP and AM primarily function in vasodilation. AMY and CRSP are associated with anorectic effects. Diversification of the molecular features and physiological functions of the CT/CGRP family in vertebrate lineages have been extensively reported. However, the origin and diversification mechanisms of the vertebrate CT/CGRP family of peptides remain unclear. In this review, the molecular characteristics of CT/CGRP family peptides and their receptors, along with their major physiological functions in mammals and teleosts, are introduced. Furthermore, novel candidates of the CT/CGRP family in cartilaginous fish are presented based on genomic information. The CT/CGRP family peptides and receptors in urochordates and cephalochordates, which are closely related to vertebrates, are also described. Finally, a putative evolutionary scenario of the CT/CGRP family peptides and receptors in chordates is discussed.

Virtual drug repurposing study for the CGRPR identifies pentagastrin and leuprorelin as putative candidates

Calcitonin gene-related peptide receptor (CGRPR) is a heterodimer consisting of CLR and RAMP1 proteins. Activation of the CGRPR with the endogenous peptide CGRP is known to play a crucial role in migraine pathophysiology. CGRP occupies two regions in the CGRPR upon binding, namely ectodomain and transmembrane sites (sites 1 and 2, respectively). The disruption of the CGRPR heterodimer interface is one of the main strategies to prevent CGRPR activation and its resulting effects. So far, FDA approved monoclonal antibodies and small molecule gepant inhibitors are considered for the treatment of acute or chronic migraine symptoms. However, most of these gepants have severe side effects. Thus, in this study, a virtual drug repurposing approach is applied to CGRPR to find alternative or better molecules that would have a potential to inhibit or block the CLR - RAMP1 interface compared to known gepant molecules. A small molecule library of FDA-approved molecules was screened in these two different binding sites, further simulations were performed and analyzed. The objectives of this study are (i) to repurpose an FDA-approved drug having more potent features for CGRPR inhibition compared to gepants, and (ii) to examine whether the transmembrane binding site (site 2) accepts small molecules or small peptide analogues for binding. As a result of this extensive in silico analysis, two molecules were identified, namely pentagastrin and leuprorelin. It is shown that FDA approved compound rimegepant and the identified pentagastrin molecules form and maintain the interactions through CLR W72 and RAMP1 W74, which are the residues revealed to have an important role in CGRPR antagonism at binding site 1. At binding site 2, the interactions needed to be formed for CGRP binding are not captured by rimegepant nor leuprorelin, yet leuprorelin forms more interactions throughout the simulations, meaning that small molecules are also capable of binding to site 2. Moreover, it is found that the crucial interactions for receptor signaling and heterodimerization occurred between CLR and RAMP1 interface are disrupted more with the ligands bound to ectodomain site, rather than the transmembrane domain. These findings of pentagastrin and leuprorelin molecules are recommended to be considered in further de novo drug development and/or experimental studies related to CGRPR signaling blockade and antagonism.

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.

CGRP and Migraine: What Have We Learned From Measuring CGRP in Migraine Patients So Far?

The multi-functional neuropeptide calcitonin gene-related peptide (CGRP) plays a major role in the pathophysiology of migraine. The detection of elevated CGRP levels during acute migraine headache was the first evidence of the importance of the peptide. Since then, elevated CGRP levels have been detected not only during spontaneous and experimentally induced migraine attacks but also interictally. However, the detection of CGRP in peripheral blood shows conflicting results. In this respect, alternative detection methods are needed and have been already proposed. This article summarizes what we have learned from studies investigating CGRP in jugular and peripheral blood and reviews the latest state of research concerning the detection of CGRP in saliva and tear fluid as well as their contribution to our understanding of migraine pathophysiology.

Characterization of transit rates in the large intestine of mice following treatment with a CGRP antibody, CGRP receptor antibody, and small molecule CGRP receptor antagonists

Objective

To characterize the effects of blocking calcitonin gene‐related peptide (CGRP) activity in a mouse model of gastrointestinal transport.

Background

Migraine management using CGRP modulating therapies can cause constipation of varying frequency and severity. This variation might be due to the different mechanisms through which therapies block CGRP activity (e.g., blocking CGRP, or the CGRP receptor) with antibodies or receptor antagonists. The charcoal meal gastrointestinal transit assay was used to characterize constipation produced by these modes of therapy in transgenic mice expressing the human receptor activity–modifying protein 1 (hRAMP1) subunit of the CGRP receptor complex.

Methods

Male and female hRAMP1 mice were dosed with compound or vehicle and challenged with a charcoal meal suspension via oral gavage. The mice were then humanely euthanized and the proportion of the length of the large intestine that the charcoal meal had traveled indicated gastrointestinal transit.

Results

Antibody to the CGRP receptor produced % distance traveled (mean ± standard deviation) of 31.8 ± 8.2 (4 mg/kg; p = 0.001) and 33.2 ± 6.0 (30 mg/kg; p < 0.001) compared to 49.7 ± 8.3 (control) in female mice (n = 6–8), and 35.6 ± 13.5 (30 mg/kg, p = 0.019) compared to 50.2 ± 14.0 (control) in male mice (n = 10). Telcagepant (5 mg/kg, n = 8) resulted in % travel of 30.6 ± 14.7 versus 41.2 ± 8.3 (vehicle; p = 0.013) in male mice. Atogepant (3 mg/kg, n = 9) resulted in % travel of 30.6 ± 12.0, versus 41.2 ± 3.7 (control; p = 0.030) in female mice. The CGRP antibody galcanezumab (n = 7–10; p = 0.958 and p = 0.929) did not have a statistically significant effect.

Conclusions

These results are consistent with reported clinical data. Selectively blocking the CGRP receptor may have a greater impact on gastrointestinal transit than attenuating the activity of the ligand CGRP. This differential effect may be related to physiologically opposing mechanisms between the CGRP and AMY1 receptors, as the CGRP ligand antibody could inhibit the effects of CGRP at both the CGRP and AMY1 receptors.

Recent advances in targeting calcitonin gene-related peptide for the treatment of menstrual migraine: A narrative review

Menstrual migraine (MM) has a longer duration and higher drug resistance than non-perimenstrual migraine. Calcitonin gene-related peptide (CGRP) and CGRP receptors are expressed in the peripheral and central nervous systems throughout the trigeminovascular system. The CGRP/CGRP receptor axis plays an important role in sensory physiology and pharmacology. CGRP receptor antagonists and anti-CGRP monoclonal antibodies (mAbs) have shown consistent efficacy and tolerability in the prevention of chronic or episodic migraine and are now approved for clinical use. However, few studies have reported the use of these drugs in MM, and no specific treatment for MM has been approved. This review aimed to shed light on the recent advances in targeting calcitonin gene-related peptides for the treatment of menstrual migraines in PubMed. In this review, we first discuss the axis of the CGRP/CGRP receptor. We then discuss the role of CGRP receptor antagonists and anti-CGRP mAbs in MM treatment. Finally, we discuss the role of the combination of anti-CGRP mAbs and CGRP receptor antagonists in migraine treatment and the drugs that inhibit CGRP release. Altogether, the anti-CGRP mAbs or CGRP receptor antagonists showed good efficacy and safety in the treatment of MM.

Is calcitonin gene-related peptide a reliable biochemical marker of migraine?

PURPOSE OF REVIEW

The aim of this study was to provide an overview of clinical studies on calcitonin gene-related peptide (CGRP) measurements in body fluids of migraine patients and to discuss the validity of CGRP measurement as a clinical biomarker of migraine.

RECENT FINDINGS

Several studies have reported increased CGRP levels in venous blood, saliva and tear fluid of migraine patients compared with healthy controls and in migraine patients during attacks compared with the interictal state, suggesting that CGRP may be a feasible biomarker of migraine. However, the findings of studies investigating CGRP levels in migraine patients are generally conflicting and measurements of CGRP levels are challenged by several methodological issues. Reported differences in CGRP levels between patients with chronic migraine relative to episodic migraine have also been inconsistent. There is also a well documented involvement of CGRP in several nonmigraine pain disorders, including cluster headache and common pain conditions such as osteoarthritis.

SUMMARY

Current evidence does not justify the usage of CGRP levels as a biomarker for diagnosing migraine or for determining the severity of the disease in individual patients. However, CGRP measurements could prove useful in the future as clinically relevant biomarkers for predicting the response to therapy, including anti-CGRP migraine drugs.

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.

Alpha-Calcitonin Gene Related Peptide: New Therapeutic Strategies for the Treatment and Prevention of Cardiovascular Disease and Migraine

Alpha-calcitonin gene-related peptide (α-CGRP) is a vasodilator neuropeptide of the calcitonin gene family. Pharmacological and gene knock-out studies have established a significant role of α-CGRP in normal and pathophysiological states, particularly in cardiovascular disease and migraines. α-CGRP knock-out mice with transverse aortic constriction (TAC)-induced pressure-overload heart failure have higher mortality rates and exhibit higher levels of cardiac fibrosis, inflammation, oxidative stress, and cell death compared to the wild-type TAC-mice. However, administration of α-CGRP, either in its native- or modified-form, improves cardiac function at the pathophysiological level, and significantly protects the heart from the adverse effects of heart failure and hypertension. Similar cardioprotective effects of the peptide were demonstrated in pressure-overload heart failure mice when α-CGRP was delivered using an alginate microcapsules-based drug delivery system. In contrast to cardiovascular disease, an elevated level of α-CGRP causes migraine-related headaches, thus the use of α-CGRP antagonists that block the interaction of the peptide to its receptor are beneficial in reducing chronic and episodic migraine headaches. Currently, several α-CGRP antagonists are being used as migraine treatments or in clinical trials for migraine pain management. Overall, agonists and antagonists of α-CGRP are clinically relevant to treat and prevent cardiovascular disease and migraine pain, respectively. This review focuses on the pharmacological and therapeutic significance of α-CGRP-agonists and -antagonists in various diseases, particularly in cardiac diseases and migraine pain.

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.

Molecular simulations reveal the impact of RAMP1 on ligand binding and dynamics of calcitonin gene-related peptide receptor (CGRPR) heterodimer

Calcitonin gene-related peptide receptor (CGRPR) is a heterodimer protein complex consisting of a class-B G protein-coupled receptor (GPCR) named calcitonin receptor-like receptor (CLR) and an accessory protein, receptor activity modifying protein type 1 (RAMP1). Here in this study, with several molecular modeling approaches and molecular dynamics (MD) simulations, the structural and dynamical effects of RAMP1 on the binding of small molecule CGRPR inhibitors (namely rimegepant and telcagepant) to the CGRPR extracellular ectodomain complex site (site 1) and transmembrane binding site (site 2) are investigated. Results showed that although these molecules stay stable at site 1, they can also bind to site 2, which may be interpreted as non-specificity of the ligands, however, most of these interactions at transmembrane binding site are not sustainable or are weak. Furthermore, to examine the site 2 for gepant binding, different in silico experiments (i.e., alanine scanning mutagenesis, SiteMap, ligand decomposition binding free energy analyses) are also conducted and the results confirmed the putative binding pocket (site 2) of the gepants at the CGRPRs.

Sexual dimorphism in functional pain syndromes

Injury-free pain conditions, defined as functional pain syndromes, are more prevalent and more disabling in women. Mechanisms of sexual dimorphism in functional pain are now emerging from preclinical studies, suggesting an opportunity to advance the development of sex-specific therapies that may improve treatment of pain in women.

Understanding the link between obesity and headache- with focus on migraine and idiopathic intracranial hypertension

BACKGROUND

Obesity confers adverse effects to every system in the body including the central nervous system. Obesity is associated with both migraine and idiopathic intracranial hypertension (IIH). The mechanisms underlying the association between obesity and these headache diseases remain unclear.

METHODS

We conducted a narrative review of the evidence in both humans and rodents, for the putative mechanisms underlying the link between obesity, migraine and IIH.

RESULTS

Truncal adiposity, a key feature of obesity, is associated with increased migraine morbidity and disability through increased headache severity, frequency and more severe cutaneous allodynia. Obesity may also increase intracranial pressure and could contribute to headache morbidity in migraine and be causative in IIH headache. Weight loss can improve both migraine and IIH headache. Preclinical research highlights that obesity increases the sensitivity of the trigeminovascular system to noxious stimuli including inflammatory stimuli, but the underlying molecular mechanisms remain unelucidated.

CONCLUSIONS

This review highlights that at the epidemiological and clinical level, obesity increases morbidity in migraine and IIH headache, where weight loss can improve headache morbidity. However, further research is required to understand the molecular underpinnings of obesity related headache in order to generate novel treatments.

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.

A critical review of the neurovascular nature of migraine and the main mechanisms of action of prophylactic antimigraine medications

INTRODUCTION

Migraine involves neurovascular, functional, and anatomical alterations. Migraineurs experience an intense unilateral and pulsatile headache frequently accompanied with vomiting, nausea, photophobia, etc. Although there is no ideal preventive medication, frequency in migraine days may be partially decreased by some prophylactics, including antihypertensives, antidepressants, antiepileptics, and CGRPergic inhibitors. However, the mechanisms of action involved in antimigraine prophylaxis remain elusive.

AREAS COVERED

This review recaps some of the main neurovascular phenomena related to migraine and currently available preventive medications. Moreover, it discusses the major mechanisms of action of the recommended prophylactic medications.

EXPERT OPINION

In the last three years, migraine prophylaxis has evolved from nonspecific to specific antimigraine treatments. Overall, nonspecific treatments  mainly involve neural actions, whereas specific pharmacotherapy (represented by CGRP receptor antagonists and CGRPergic monoclonal antibodies) is predominantly mediated by neurovascular mechanisms that may include, among others: (i) reduction in the cortical spreading depression (CSD)-associated events; (ii) inhibition of pain sensitization; (iii) blockade of neurogenic inflammation; and/or (iv) increase in cranial vascular tone. Accordingly, the novel antimigraine prophylaxis promises to be more effective, devoid of significant adverse effects (unlike nonspecific treatments), and more beneficial for the quality of life of migraineurs.

To Probe the Binding Interactions between Two FDA Approved Migraine Drugs (Ubrogepant and Rimegepant) and Calcitonin-Gene Related Peptide Receptor (CGRPR) Using Molecular Dynamics Simulations

Recently, the FDA approved ubrogepant and rimegepant as oral drugs to treat migraines by targeting the calcitonin-gene related peptide receptor (CGRPR). Unfortunately, there is no high-resolution complex structure with these two drugs; thus the detailed interaction between drugs and the receptor remains elusive. This study uses molecular docking and molecular dynamics simulation to model the drug-receptor complex and analyze their binding interactions at a molecular level. The complex crystal structure (3N7R) of the gepant drugs' predecessor, olcegepant, was used for our molecular docking of the two drugs and served as a control system. The three systems, with ubrogepant, rimegepant, and crystal olcegepant, were subject to 3 × 1000 ns molecular dynamics simulations and followed by the simulation interaction diagram (SID), structural clustering, and MM-GBSA binding energy analyses. Our MD data revealed that olcegepant binds most strongly to the CGRPR, followed by ubrogepant and then rimegepant, largely due to changes in hydrophobic and electrostatic interactions. The order of our MM-GBSA binding energies of these three compounds is consistent with their experimental IC₅₀ values. SID analysis revealed the pharmacophore of the gepant class to be the dihydroquinazolinone group derivative. Subtle differences in interaction profile have been noted, including interactions with the W74 and W72 residues. The ubrogepant and rimegepant both contact A70 and M42 of the receptor, while olcegepant does not. The results of this study elucidate the interactions in the binding pocket of CGRP receptor and can assist in further development for orally available antagonists of the CGRP receptor.

Updated review on the link between cortical spreading depression and headache disorders

INTRODUCTION

Experimental animal studies have revealed mechanisms that link cortical spreading depression (CSD) to the trigeminal activation mediating lateralized headache. However, conventional CSD as seen in lissencephalic brain is insufficient to explain some clinical features of aura and migraine headache.

AREAS COVERED

The importance of CSD in headache development including dysfunction of the thalamocortical network, neuroinflammation, calcitonin gene-related peptide, transgenic models, and the role of CSD in migraine triggers, treatment options, neuromodulation and future directions are reviewed.

EXPERT OPINION

The conventional understanding of CSD marching across the hemisphere is invalid in gyrencephalic brains. Thalamocortical dysfunction and interruption of functional cortical network systems by CSD, may provide alternative explanations for clinical manifestations of migraine phases including aura. Not all drugs showing CSD blocking properties in lissencephalic brains, have efficacy in migraine headache and monoclonal antibodies against CGRP ligand/receptors which are effective in migraine treatment, have no impact on aura in humans or CSD properties in rodents. Functional networks and molecular mechanisms mediating and amplifying the effects of limited CSD in migraine brain remain to be investigated to define new targets.

Development and validation of a reporter gene assay for bioactivity determination of Anti-CGRP monoclonal antibodies

Calcitonin gene-related peptide (CGRP) is critical for the pathophysiology of migraine, and four therapeutic antibodies targeting CGRP and its corresponding receptors have been approved by the Food and Drug Administration (FDA), while many others are in the different stages of clinical trials. Bioactivity determination is essential for the quality control and clinical application of therapeutic monoclonal antibodies (mAbs). However, no bioassay has been reported to date. In this study, we developed a reporter gene assay (RGA) based on SK-N-MC cells stably expressing firefly luciferase driven by cAMP response element (CRE). The key assay parameters were optimized according to signal-to-noise (SNR), the response value, and the fitted dose-response curve. Validation of the RGA in accordance with ICH-Q2 guidelines showed that the method had good specificity, accuracy, linearity, and precision. The established RGA can be utilized as a reference method for release testing and stability studies of relevant antibodies.

CGRP receptor antagonists for migraine. Are they also AMY1 receptor antagonists?

The development of several drugs that target the calcitonin gene-related peptide (CGRP) system has been a major breakthrough in the pharmacological management of migraine. These are divided into two major classes, antibodies which bind to the CGRP peptide, preventing it from activating CGRP receptors and receptor antagonists. Within the receptor antagonist class, there are two mechanisms of action, small molecule receptor antagonists and an antibody antagonist. This mini-review considers the pharmacology of these receptor targeted antagonist drugs at the CGRP receptor and closely related AMY₁ receptor, at which CGRP may also act. The antagonists are most potent at the CGRP receptor but can also show antagonism of the AMY₁ receptor. However, important data are missing and selectivity parameters cannot be provided for all antagonists. The clinical implications of AMY₁ receptor antagonism are unknown, but we urge consideration of this receptor as a potential contributing factor to CGRP and antagonist drug actions.

Excitatory Effects of Calcitonin Gene-Related Peptide (CGRP) on Superficial Sp5C Neurons in Mouse Medullary Slices

The neuromodulator calcitonin gene-related peptide (CGRP) is known to facilitate nociceptive transmission in the superficial laminae of the spinal trigeminal nucleus caudalis (Sp5C). The central effects of CGRP in the Sp5C are very likely to contribute to the activation of central nociceptive pathways leading to attacks of severe headaches like migraine. To examine the potential impacts of CGRP on laminae I/II neurons at cellular and synaptic levels, we performed whole-cell patch-clamp recordings in juvenile mouse brainstem slices. First, we tested the effect of CGRP on cell excitability, focusing on neurons with tonically firing action potentials upon depolarizing current injection. CGRP (100 nM) enhanced tonic discharges together with membrane depolarization, an excitatory effect that was significantly reduced when the fast synaptic transmissions were pharmacologically blocked. However, CGRP at 500 nM was capable of exciting the functionally isolated cells, in a nifedipine-sensitive manner, indicating its direct effect on membrane intrinsic properties. In voltage-clamped cells, 100 nM CGRP effectively increased the frequency of excitatory synaptic inputs, suggesting its preferential presynaptic effect. Both CGRP-induced changes in cell excitability and synaptic drives were prevented by the CGRP receptor inhibitor BIBN 4096BS. Our data provide evidence that CGRP increases neuronal activity in Sp5C superficial laminae by dose-dependently promoting excitatory synaptic drive and directly enhancing cell intrinsic properties. We propose that the combination of such pre- and postsynaptic actions of CGRP might underlie its facilitation in nociceptive transmission in situations like migraine with elevated CGRP levels.

A link between gastrointestinal disorders and migraine: Insights into the gut-brain connection

Background

Migraine is a complex, multifaceted, and disabling headache disease that is often complicated by gastrointestinal (GI) conditions, such as gastroparesis, functional dyspepsia, and cyclic vomiting syndrome (CVS). Functional dyspepsia and CVS are part of a spectrum of disorders newly classified as disorders of gut–brain interaction (DGBI). Gastroparesis and functional dyspepsia are both associated with delayed gastric emptying, while nausea and vomiting are prominent in CVS, which are also symptoms that commonly occur with migraine attacks. Furthermore, these gastric disorders are comorbidities frequently reported by patients with migraine. While very few studies assessing GI disorders in patients with migraine have been performed, they do demonstrate a physiological link between these conditions.

Objective

To summarize the available studies supporting a link between GI comorbidities and migraine, including historical and current scientific evidence, as well as provide evidence that symptoms of GI disorders are also observed outside of migraine attacks during the interictal period. Additionally, the importance of route of administration and formulation of migraine therapies for patients with GI symptoms will be discussed.

Methods

A literature search of PubMed for articles relating to the relationship between the gut and the brain with no restriction on the publication year was performed. Studies providing scientific support for associations of gastroparesis, functional dyspepsia, and CVS with migraine and the impact these associations may have on migraine treatment were the primary focus. This is a narrative review of identified studies.

Results

Although the association between migraine and GI disorders has received very little attention in the literature, the existing evidence suggests that they may share a common etiology. In particular, the relationship between migraine, gastric motility, and vomiting has important clinical implications in the treatment of migraine, as delayed gastric emptying and vomiting may affect oral dosing compliance, and thus, the absorption and efficacy of oral migraine treatments.

Conclusions

There is evidence of a link between migraine and GI comorbidities, including those under the DGBI classification. Many patients do not find adequate relief with oral migraine therapies, which further necessitates increased recognition of GI disorders in patients with migraine by the headache community.

Migraine therapeutics differentially modulate the CGRP pathway

Background

The clinical efficacy of migraine therapeutic agents directed towards the calcitonin-gene related peptide (CGRP) pathway has confirmed the key role of this axis in migraine pathogenesis. Three antibodies against CGRP – fremanezumab, galcanezumab and eptinezumab – and one antibody against the CGRP receptor, erenumab, are clinically approved therapeutics for the prevention of migraine. In addition, two small molecule CGRP receptor antagonists, ubrogepant and rimegepant, are approved for acute migraine treatment. Targeting either the CGRP ligand or receptor is efficacious for migraine treatment; however, a comparison of the mechanism of action of these therapeutic agents is lacking in the literature.

Methods

To gain insights into the potential differences between these CGRP pathway therapeutics, we compared the effect of a CGRP ligand antibody (fremanezumab), a CGRP receptor antibody (erenumab) and a CGRP receptor small molecule antagonist (telcagepant) using a combination of binding, functional and imaging assays.

Results

Erenumab and telcagepant antagonized CGRP, adrenomedullin and intermedin cAMP signaling at the canonical human CGRP receptor. In contrast, fremanezumab only antagonized CGRP-induced cAMP signaling at the human CGRP receptor. In addition, erenumab, but not fremanezumab, bound and internalized at the canonical human CGRP receptor. Interestingly, erenumab also bound and internalized at the human AMY₁ receptor, a CGRP receptor family member. Both erenumab and telcagepant antagonized amylin-induced cAMP signaling at the AMY₁ receptor while fremanezumab did not affect amylin responses.

Conclusion

The therapeutic effect of agents targeting the CGRP ligand versus receptor for migraine prevention (antibodies) or acute treatment (gepants) may involve distinct mechanisms of action. These findings suggest that differing mechanisms could affect efficacy, safety, and/or tolerability in migraine patients.

Cellular iron storage and trafficking are affected by GTN stimulation in primary glial and meningeal cell culture

A well-balanced intracellular iron trafficking in glial cells plays a role in homeostatic processes. Elevated intracellular iron triggers oxidative stress and cell damage in many neurological disorders, including migraine. This study aimed to investigate the effects of glyceryl trinitrate (GTN), on cellular iron homeostasis, matrixmetalloproteinase (MMP)-9, and calcitonin gene related peptide (CGRP) receptor (CRLR/CGRPR1) production in microglia, astrocyte, and meningeal cell cultures. Primary glial and meningeal cells in culture were exposed to GTN for 24 h. Messenger RNA expression was assessed using qPCR. Iron accumulation was visualized via modified Perl's histochemistry. MMP-9 levels in cell culture supernatants were measured using ELISA. Ferritin and CRLR/CGRPR1 proteins were visualized via immunofluorescence staining. Nitric oxide production increased significantly with GTN in meningeal and glial cells. GTN significantly increased the expression of the storage protein ferritin for all three cell types, but ferritin-L for meningeal cells and microglia. Iron trafficking associated with the efflux protein ferroportin and influx protein divalent metal transporter (DMT)1 was affected differently in all three cell types. MMP-9 expression was increased in astrocytes. GTN stimulation increased both CRLR/CGRPR1 expression, and immunostaining was apparent in microglia and meningeal cells. This study showed for the first time that GTN modulates intracellular iron trafficking regulated by storage and transport proteins expressed in meningeal cells and glia. CRLR/CGRPR1 expression might be related to altered iron homeostasis and they both may stimulate nociceptive pathways activated in migraine. These molecules expressed differently in glial and meningeal cells in response to GTN may bring not only new targets forward in treatment but also prevention in migraine.

Neurotransmitter and neuropeptide regulation of mast cell function: a systematic review

The existence of the neural control of mast cell functions has long been proposed. Mast cells (MCs) are localized in association with the peripheral nervous system (PNS) and the brain, where they are closely aligned, anatomically and functionally, with neurons and neuronal processes throughout the body. They express receptors for and are regulated by various neurotransmitters, neuropeptides, and other neuromodulators. Consequently, modulation provided by these neurotransmitters and neuromodulators allows neural control of MC functions and involvement in the pathogenesis of mast cell–related disease states. Recently, the roles of individual neurotransmitters and neuropeptides in regulating mast cell actions have been investigated extensively. This review offers a systematic review of recent advances in our understanding of the contributions of neurotransmitters and neuropeptides to mast cell activation and the pathological implications of this regulation on mast cell–related disease states, though the full extent to which such control influences health and disease is still unclear, and a complete understanding of the mechanisms underlying the control is lacking. Future validation of animal and in vitro models also is needed, which incorporates the integration of microenvironment-specific influences and the complex, multifaceted cross-talk between mast cells and various neural signals. Moreover, new biological agents directed against neurotransmitter receptors on mast cells that can be used for therapeutic intervention need to be more specific, which will reduce their ability to support inflammatory responses and enhance their potential roles in protecting against mast cell–related pathogenesis.

Optimal treatment strategy of fremanezumab in migraine prevention: a systematic review with network meta-analysis of randomized clinical trials

Identifying the optimal fremanezumab treatment strategy is crucial in treating patients with migraines. The optimal strategy was investigated by assessing the cumulative 50% reduction rate (50%CRR), cumulative 75% reduction rate (75%CRR), reduction in the number of migraine days, treatment-related adverse events, and serious adverse events in patients treated with fremanezumab 225 mg monthly (225 mg), 675 mg monthly (675 mg), 900 mg monthly (900 mg), a single high dose of 675 mg (S675mg), 675 mg at baseline with 225 mg monthly (675/225 mg), and placebo. Biomedical databases were searched for randomized controlled trials on this topic, and data were individually extracted. Risk ratios and mean differences were used to present the pooled results. The surface under the cumulative ranking curve (SUCRA) was used to determine the effects of the medication strategies of fremanezumab. Five trials (n = 3404) were used to form a six-node network meta-analysis. All fremanezumab medication strategies displayed significantly higher cumulative 50% reduction rates than the placebo. The SUCRA revealed that treatment with 675 mg yielded the highest 50%CRR value (mean rank = 2.5). S675 mg was the only treatment with significantly higher 75%CRR reduction rate than placebo, whereas the SUCRA for 225 mg displayed the highest mean rank (2.2). Moreover, 225 mg (mean rank = 2.2) and S675 mg (mean rank = 2.2) presented lower probabilities of serious adverse events. Collectively, S675mg and 225 mg exhibited the optimal balance between efficacy and safety within three months. Long-term efficacy and safety remain unclear, and future studies should further evaluate the long-term outcomes.

A new era for migraine: The role of calcitonin gene-related peptide in the trigeminovascular system

There is a huge improvement in our understanding of migraine pathophysiology in the past decades. The activation of the trigeminovascular system has been proved to play a key role in migraine. Calcitonin gene-related peptide (CGRP) and CGRP receptors are widely distributed in the trigeminovascular system. The CGRP is expressed on the C-fibers, and the CGRP receptors are distributed on the A-δ fibers of the trigeminal ganglion and nerves. Further studies found elevated serum CGRP level during migraine attacks, and infusion of CGRP can trigger migraine-like attacks, provide more direct evidence of the link between CGRP and migraine attack. Based on these findings, several treatment options have been designed for migraine treatment, including CGRP receptor antagonists (gepants) and monoclonal antibodies targeting CGRP or CGRP receptors. The clinical trials show both gepants and monoclonal antibodies are effective for migraine treatment. In this section, we describe the roles of the trigeminovascular system in migraine, the discovery of CGRP, and the CGRP signaling pathway.

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.

The role of erenumab in the treatment of migraine

Calcitonin gene related peptide (CGRP) monoclonal antibodies (mAbs) have been the first class of specifically developed preventive treatments for migraine. Clinical trials data suggest superiority of the CGRP mAbs to placebo in terms of prevention of migraine symptoms, migraine-specific quality of life and headache related disability. Treatment-related side effects overall did not differ significantly from placebo and discontinuation rate due to side effects has been low across the clinical trials, perhaps in view of their peripheral mode of action. Along with their route and frequency of administration, these novel class of drugs may constitute an improvement compared with the established arsenal of migraine treatments. Erenumab is a fully human antibody and the only mAb acting on the CGRP pathway by blocking its receptor. It is the first of the CGRP mAb class approved by the US Food and Drug Administration (May 2018) and the European Medicines Agency (July 2018). Erenumab exists in two different doses (70 mg and 140 mg) and it is administered with monthly subcutaneous injections. This review summarises erenumab pharmacological characteristics, clinical trials data, focusing on the potential role of this treatment in clinical practice.

Synthesis of isotopically labelled αCGRP8-37 and its lipidated analogue

α-Calcitonin gene related peptide (αCGRP) inhibitors are important medicinal targets due to their ability to produce antimigraine effects, thus, the discovery of long-acting αCGRP inhibitors is of significant interest. Herein we report the synthesis of an isotopically labelled version of the well-known CGRP receptor antagonist, αCGRP8-37 , as well as lipidated αCGRP8-37 with comparable antagonistic activity. These isotopically labelled peptides can be employed in assays to determine the metabolic stability of the lipidated αCGRP8-37 and compare this with the stability of known αCGRP8-37 .

Dimethyl fumarate alleviates the nitroglycerin (NTG)-induced migraine in mice

Background

Oxidative stress and inflammatory pathways are involved in migraine and endogenous antioxidant defense system has a role in the prevention of hyperalgesia in migraine. In this study, we aimed to evaluate the role of the most pharmacologically effective molecules among the fumaric acid esters (FAEs), dimethyl fumarate, nuclear factor E2-related factor 2/antioxidant response element (Nrf-2/ARE) pathway-mediated, in regulating the hypersensitivity in a mouse model of nitroglycerine (NTG)-induced migraine.

Methods

Mice were orally administered with DMF at the doses of 10, 30, and 100 mg/kg, 5 min after NTG intraperitoneal injections. We performed histological and molecular analysis on the whole brain and behavioral tests after 4 h by NTG-migraine induction. The expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-кB) subunit p65, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (IκBα), inducible nitrite oxide synthase (iNOS), cyclooxygenase 2 (COX-2), Nrf-2, manganese superoxide dismutase (Mn-SOD), and heme-oxygenase-1 (HO-1) were detected by Western blot. Tail flick, hot plate, orofacial formalin, and photophobia tests were used to evaluate migraine-like pain and migraine-related light sensitivity.

Moreover, we evaluate Nrf-2-dependent mechanism by the in vitro stimulation of cells extracted by trigeminal ganglia with diethylenetriamine/nitric oxide (DETA/NO), a nitric oxide (NO) donor. The cells were pre-treated with DMF and an antagonist of Nrf-2, trigonelline (TR) 2 h before DETA/NO stimulation.

Results

DMF treatment notably reduced histological damage as showed by cresyl violet staining; also, regulating both NF-κB and Nrf-2 pathway, DMF treatment decreased the severity of inflammation and increased the protective antioxidant action. Moreover, the headache was significantly reduced. The protective effect of DMF treatment, via Nrf-2, was confirmed in in vitro studies, through inhibition of Nrf-2 by trigonelline. Cytotoxicity, iNOS, and MnSOD expression were evaluated.

Conclusion

These results provided the evidence that DMF, by Nrf-2 modulation, has a protective effect on central sensitization induced by NTG, suggesting a new insight into the potential application of DMF as novel candidates in drug development for migraine.

Calcitonin gene-related peptide (CGRP): role in migraine pathophysiology and therapeutic targeting

Introduction: The neuropeptide calcitonin gene-related peptide (CGRP) is recognized as a critical player in migraine pathophysiology. Excitement has grown regarding CGRP because of the development and clinical testing of drugs targeting CGRP or its receptor. While these drugs alleviate migraine symptoms in half of the patients, the remaining unresponsive half of this population creates an impetus to address unanswered questions that exist in this field.Areas covered: We describe the role of CGRP in migraine pathophysiology and CGRP-targeted therapeutics currently under development and in use. We also discuss how a second CGRP receptor may provide a new therapeutic target.Expert opinion: CGRP-targeting drugs have shown a remarkable safety profile. We speculate that this may reflect the redundancy of peptides within the CGRP family and a second CGRP receptor that may compensate for reduced CGRP activity. Furthermore, we propose that an inherent safety feature of peptide-blocking antibodies is attributed to the fundamental nature of peptide release, which occurs as a large bolus in short bursts of volume transmission. These facts support the development of more refined CGRP therapeutic drugs, as well as drugs that target other neuropeptides. We believe that the future of migraine research is bright with exciting advances on the horizon.

Aberrant expression of calcitonin gene-related peptide and its correlation with prognosis in severe childhood pneumonia

OBJECTIVES

The purpose of this study was to evaluate the relationship between the serum levels of calcitonin gene-related peptide (CGRP) and the prognosis of pediatric patients with severe pneumonia.

METHODS

Children diagnosed with severe pneumonia (n=76) were stratified into the survival (n=58) and non-survival groups (n=18) according to their 28-day survival status and into the non-risk (n=51), risk (n=17) and high-risk (n=8) categories based on the pediatric critical illness score (PCIS). Demographic data and laboratory results were collected. Serum CGRP levels were determined by enzyme-linked immunosorbent assay (ELISA). A receiver operating characteristic (ROC) curve was generated to determine the cutoff score for high CGRP levels.

RESULTS

Serum CGRP levels were significantly higher in the survival group than in the non-survival group and were significantly higher in the non-risk group than in the risk and high-risk groups. The ROC curve for the prognostic potential of CGRP yielded a significant area under the curve (AUC) value with considerable sensitivity and specificity.

CONCLUSION

Our findings show that CGRP downregulation might be a diagnostic marker that predicts the prognosis and survival of children with severe pneumonia.

Circulating Biomarkers in Migraine: New Opportunities for Precision Medicine

Background:

Migraine is the most common neurological disorder and the second most disabling human condition, whose pathogenesis is favored by a combination of genetic, epigenetic, and environmental factors. In recent years, several efforts have been made to identify reliable biomarker(s) useful to monitor disease activity and/or ascertain the response to a specific treatment.

Objective:

To review the current evidence on the potential biological markers associated with migraine.

Methods:

A structured search of peer-reviewed research literature was performed by searching major publications databases up to December 2017.

Results:

Several circulating biomarkers have been proposed as diagnostic or therapeutic tools in migraine, mostly related to migraine’s inflammatory pathophysiological aspects. Nonetheless, their detection is still a challenge for the scientific community, reflecting, at least in part, disease complexity and clinical diagnostic limitations. At the present time, calcitonin generelated peptide (CGRP) represents probably the most promising candidate as a diagnostic and/or therapeutic biomarker, as its plasma levels are elevated during migraine attack and decrease during successful treatment. Other molecules (including some neuropeptides, cytokines, adipokines, or vascular activation markers) despite promising, do not possess the sufficient prerequisites to be considered as migraine biomarkers.

Conclusion:

The characterization of migraine-specific biomarkers would be fundamental in a perspective of precision medicine, enabling risk assessment and tailored treatments. However, speculating on the clinical validity of migraine biomarkers may be premature and controlled clinical trials are presently needed to investigate both the diagnostic and therapeutic value of these biomarkers in migraine.

Discovery of the Migraine Prevention Therapeutic Aimovig (Erenumab), the First FDA-Approved Antibody against a G-Protein-Coupled Receptor

In 2018, the United States Food and Drug Administration (FDA) approved Aimovig (erenumab) for the prevention of migraine. Erenumab is the first FDA approved antibody therapeutic against a G-protein-coupled receptor, the canonical receptor of calcitonin gene related peptide (CGRP-R). A novel, epitope-focused antigen was created to reconstruct the extracellular domains of the CGRP-R in a stable conformation. Successful inoculation of XenoMouse animals and careful screening yielded multiple candidate molecules for high potency and exquisite selectivity toward the CGRP-R over related receptors. These efforts led to the discovery of erenumab which has demonstrated the desired efficacy and safety profiles in multiple clinical studies for the prevention of migraine. The innovation developed in the discovery of erenumab furthers the ability to target G-coupled protein receptors using antibody approaches.

Endogenous Neuropeptide Nocistatin Is a Direct Agonist of Acid-Sensing Ion Channels (ASIC1, ASIC2 and ASIC3)

Acid-sensing ion channel (ASIC) channels belong to the family of ligand-gated ion channels known as acid-sensing (proton-gated) ion channels. Only a few activators of ASICs are known. These are exogenous and endogenous molecules that cause a persistent, slowly desensitized current, different from an acid-induced current. Here we describe a novel endogenous agonist of ASICs-peptide nocistatin produced by neuronal cells and neutrophils as a part of prepronociceptin precursor protein. The rat nocistatin evoked currents in X. laevis oocytes expressing rat ASIC1a, ASIC1b, ASIC2a, and ASIC3 that were very similar in kinetic parameters to the proton-gated response. Detailed characterization of nocistatin action on rASIC1a revealed a proton-like dose-dependence of activation, which was accompanied by a dose-dependent decrease in the sensitivity of the channel to the protons. The toxin mambalgin-2, antagonist of ASIC1a, inhibited nocistatin-induced current, therefore the close similarity of mechanisms for ASIC1a activation by peptide and protons could be suggested. Thus, nocistatin is the first endogenous direct agonist of ASICs. This data could give a key to understanding ASICs activation regulation in the nervous system and also could be used to develop new drugs to treat pathological processes associated with ASICs activation, such as neurodegeneration, inflammation, and pain.