The role of anti-CGRP antibodies in the pathophysiology of primary headaches

Calcitonin gene-related peptide ameliorates sepsis-induced intestinal injury by suppressing NLRP3 inflammasome activation

Intestinal damage has long been viewed as the primary cause of sepsis-induced multiple organ dysfunction syndrome (MODS). Previous studies have demonstrated that calcitonin gene-related peptide (CGRP) exhibits anti-inflammatory and protective effects in mice exposed to endotoxin. This study investigated whether CGRP protects against sepsis-induced intestinal damage and its underlying mechanisms. Using a murine caecal ligation and puncture (CLP) model, we observed elevated serum and intestinal CGRP levels in septic mice. CGRP knockout (KO) mice showed more severe intestinal barrier damage, excessive NLRP3 inflammasome activation and higher levels of inflammation. In vitro, we used lipopolysaccharide (LPS) and adenosine triphosphate (ATP) to activate the NLRP3 inflammasome in MODE-K murine intestinal epithelial cells. CGRP inhibited NF-κB pathway activation; prevented ASC assembly and ROS accumulation; significantly decreased NLRP3, Caspase-1 p10, and IL-1β levels and LDH release; and increased cell viability. Treatment with an IL-1β inhibitor or CGRP suppressed p38 MAPK and ERK1/2 pathway activation and increased ZO-1 and Occludin protein levels in LPS+ATP-treated MODE-K cells. Finally, we used the CGRP upstream agonist drug rutaecarpine (RUT) to control endogenous CGRP release in mice, and this drug demonstrated good therapeutic effects on septic intestinal injury. In conclusion, our results suggest that CGRP ameliorates sepsis-induced intestinal damage, providing valuable insights for drug development.

Efficacy and safety of calcitonin gene-related peptide antagonists in migraine treatment: A meta-analysis

INTRODUCTION

We systematically reviewed the efficacy and safety of Calcitonin Gene-Related Peptide (CGRP) antagonists for migraine treatment.

METHODS

Various databases including PubMed, Embase, The Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), WanFang Data were electronically searched for randomized controlled trials (RCTs) on CGRP antagonists for migraine treatment since inception to March 2021. The trials were screened for inclusion, after which the methodological quality of the included trials was assessed. Then meta-analysis was performed using the Revman 5.3 software.

RESULTS

A total of 26 RCTs involving 21,736 patients were included. The CGRP antagonists group included 13,635 patients while the control group included 8101 patients. Meta-analysis showed that compared to the control group, CGRP antagonists were associated with various significant effects, including the following outcome indicators: (1) number of patients with ≥50% reduction from baseline in mean monthly migraine days (RR = 1.50, 95% CI [1.39,1.62], p < .00001); (2) number of patients with pain free at 2 h postdose (RR = 1.98, 95% CI [1.77, 2.20], p < .00001), and (3) number of patients with 2-24 h sustained pain free postdose (RR = 2.18, 95% CI [1.93, 2.46], p < .00001). However, the number of patients with any adverse events was significantly high in the antagonists group, relative to the control group (RR = 1.08, 95% CI [1.04, 1.12], p < .0001).

CONCLUSIONS

CGRP antagonists are significantly effective for migraine treatment; however, they are associated with various adverse events. Due to limitations with regards to quantity and quality of the included studies, the above conclusions should be verified by more high quality studies.

Schwann cells and trigeminal neuralgia

Schwann cells are components of the peripheral nerve myelin sheath, which supports and nourishes axons. Upon injury of the trigeminal nerve, Schwann cells are activated and cause trigeminal neuralgia by engulfing the myelin sheath and secreting various neurotrophic factors. Further, Schwann cells can repair the damaged nerve and thus alleviate trigeminal neuralgia. Here, we briefly describe the development and activation of Schwann cells after nerve injury. Moreover, we expound on the occurrence, regulation, and treatment of trigeminal neuralgia; further, we point out the current research deficiencies and future research directions.

Effectiveness of erenumab and onabotulinumtoxinA on acute medication usage and health care resource utilization as migraine prevention in the United States

BACKGROUND: Migraine is a common neurological disease that can have a substantial impact on patients' lives and on society. Erenumab, a fully human monoclonal antibody that targets the calcitonin gene-related peptide receptor, was specifically developed for migraine prevention. The efficacy of erenumab has been established in several clinical trials; however, the real-world comparative effectiveness of erenumab has not been fully investigated. OBJECTIVE: To evaluate the real-world impact of erenumab and onabotulinumtoxinA on acute medication usage and health care resource utilization (HCRU) among patients with migraine in the United States. METHODS: This retrospective US claims analysis (Optum's deidentified Clinformatics Data Mart Database) evaluated patients aged at least 18 years diagnosed with migraine who initiated erenumab or onabotulinumtoxinA between May 1, 2018, and September 30, 2019 (index date: first erenumab/onabotulinumtoxinA claim). Cohorts were matched 1:1 using the propensity score (PS) method (greedy match with caliper = 0.1). Stratification was performed based on gender, chronic migraine without aura diagnosis, onabotulinumtoxinA use, and acute/preventive drug use. The impact of erenumab and onabotulinumtoxinA on acute medication usage and HCRU was assessed in the 6-month post-index period. An exploratory analysis assessed the impact of erenumab and onabotulinumtoxinA on a composite endpoint of: (1) outpatient visit with a migraine diagnosis and associated acute medication claim, (2) hospital admission with a primary migraine diagnosis, or (3) emergency department visit with a primary migraine diagnosis. PS-matched data were used for comparative analyses; logistic regression with covariate adjustment was used for dichotomous variables, and a negative binomial model was used for count variables, with odds ratios or rate ratios (RRs) and 95% CIs calculated. RESULTS: Following stratified PS matching, 1,338 patients were included in both cohorts. At 6 months, the adjusted average number of claims per person for any acute medication was significantly lower in the erenumab cohort (1.13 vs 1.29 in the onabotulinumtoxinA cohort; RR = 0.88; 95% CI = 0.80-0.96; P = 0.0069), although the difference in the number of claims for triptans and barbiturates was statistically nonsignificant. The adjusted average number of all-cause and migraine-specific visits per person to health care providers was generally lower in the erenumab cohort compared with the onabotulinumtoxinA cohort. Patients in the erenumab cohort had a significantly lower number of composite events (0.44 vs 0.69 in the onabotulinumtoxinA cohort; RR = 0.63; 95% CI = 0.56-0.71; P < 0.0001). Similarly, the adjusted proportion of patients with any of the 3 composite events was lower in the erenumab cohort (31.7% vs 44.3% in the onabotulinumtoxinA cohort; OR = 0.59; 95% CI = 0.49-0.70; P < 0.0001). CONCLUSIONS: In this retrospective claims analysis study, erenumab significantly reduced acute medication usage (opioids and nonsteroidal anti-inflammatory drugs; any acute medication when analyzed together) and HCRU to a greater extent than onabotulinumtoxinA. DISCLOSURES: This study was supported by Novartis Pharma AG. Novartis employees contributed to the study design, analysis of the data, and the decision to publish the results. Fang, Abdrabboh, Glassberg, Vo, and Ferraris are employed by Novartis. Zhou and Shen are employed by KMK Consulting, Inc., which received funding from Novartis to conduct the study. Tepper reports grants from Allergan, Amgen, ElectroCore, Eli Lilly, Lundbeck, Neurolief, Novartis, Satsuma, and Zosano, outside the submitted work; personal fees from Dartmouth-Hitchcock Medical Center, American Headache Society, Thomas Jefferson University, Aeon, Align Strategies, Allergan/AbbVie, Alphasights, Amgen, Aperture Venture Partners, Aralez Pharmaceuticals Canada, Axsome Therapeutics, Becker Pharmaceutical Consulting, BioDelivery Sciences International, Biohaven, ClearView Healthcare Partners, CoolTech, CRG, Currax, Decision Resources, DeepBench, DRG, Eli Lilly, Equinox, ExpertConnect, GLG, Guidepoint Global Healthcare Consultancy Group, Health Science Communications, HMP Communications, Impel, InteractiveForums, M3 Global Research, Magellan Rx Management, Medicxi, Navigant Consulting, Neurorelief, Nordic BioTech, Novartis, Pulmatrix, Reckner Healthcare, Relevale, SAI MedPartners, Satsuma, Slingshot Insights, Spherix Global Insights, Sudler and Hennessey, Synapse Medical Communications, System Analytic, Teva, Theranica, Thought Leader Select, Trinity Partners, XOC, Zosano, Krog and Partners, and Lundbeck, outside the submitted work; and CME honoraria from American Academy of Neurology, American Headache Society, Cleveland Clinic Foundation, Diamond Headache Clinic, Elsevier, Forefront Collaborative, Hamilton General Hospital, Ontario, Canada, Headache Cooperative of New England, Henry Ford Hospital, Detroit, Inova, Medical Learning Institute PeerView, Medical Education Speakers Network, Miller Medical Communications, North American Center for CME, Physicians' Education Resource, Rockpointe, ScientiaCME, WebMD/Medscape. The abstract and poster of these results were presented at The Migraine Trust Virtual Symposium (MTIS), October 3-9, 2020.

Calcitonin Gene-Related Peptide (CGRP) and Cluster Headache

Cluster headache (CH) is a severe primary headache with a prevalence of 1/1000 individuals, and a predominance in men. Calcitonin gene-related peptide (CGRP) is a potent vasodilator, originating in trigeminal neurons and has a central role in CH pathophysiology. CGRP and the CGRP receptor complex have recently taken center stage as therapeutic targets for primary headaches, such as migraine. Multiple CGRP and CGRP receptor monoclonal antibodies, as well as small molecule antagonists (gepants) are on their way constituting a new frontier of migraine and possibly CH medication. During a CH attack, there is an activation of the trigeminal-autonomic reflex with the release of CGRP, and inversely if CGRP is administered to a CH patient in an active disease phase, it triggers an attack. Increased levels of CGRP have been found in ipsilateral jugular vein blood during the active phase of CH. This process is hypothesized to have a key role in the intense pain perception and in the associated distinctive vasodilation. So far, clinical tests of CGRP antibodies have been inconclusive in CH patients. This review summarizes the current state of knowledge on the role of CGRP in CH pathology, and as a target for future treatments.

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.

Involvement of CGRP receptor RAMP1 in cluster headache: A Swedish case-control study

Background:

Increased levels of the potent vasodilator calcitonin gene-related peptide (CGRP) have been found in ipsilateral jugular vein blood during the active phase of cluster headache (CH) and this is hypothesized to cause distinctive vasodilation. The receptor activity-modifying protein 1 (RAMP1) is part of the CGRP receptor complex responsible for ligand binding and specificity and therefore constitutes a promising candidate gene for CH. The aim of this study was to investigate the possible genetic association of RAMP1 with CH in Sweden, with focus on two RAMP1 single nucleotide polymorphisms, rs3754701 and rs7590387, and quantify RAMP1 mRNA expression levels in biological tissue from CH patients and controls.

Methods:

rs3754701 and rs7590387 were genotyped by quantitative polymerase chain reaction (qPCR) in 542 CH patients and 585 control subjects. RAMP1 mRNA expression was determined by reverse transcription qPCR in tissue from 12 CH patients and 12 controls.

Results:

We identified a significant difference between the CH patient and control groups for rs3754701 ( p = 0.0088). In addition, RAMP1 mRNA expression was enhanced in primary fibroblasts from CH patients compared to controls ( p = 0.0073).

Conclusion:

The association between rs3754701 and CH and the enhanced RAMP1 mRNA expression in CH patients support the hypothesis that CGRP and its receptor component RAMP1 are involved in CH pathophysiology.

Current and emerging evidence-based treatment options in chronic migraine: a narrative review

Background

Chronic migraine is a disabling condition that is currently underdiagnosed and undertreated. In this narrative review, we discuss the future of chronic migraine management in relation to recent progress in evidence-based pharmacological treatment.

Findings

Patients with chronic migraine require prophylactic therapy to reduce the frequency of migraine attacks, but the only currently available evidence-based prophylactic treatment options for chronic migraine are topiramate and onabotulinumtoxinA. Improved prophylactic therapy is needed to reduce the high burden of chronic migraine in Italy. Monoclonal antibodies that target the calcitonin gene-related peptide (CGRP) pathway of migraine pathogenesis have been specifically developed for the prophylactic treatment of chronic migraine. These anti-CGRP/R monoclonal antibodies have demonstrated good efficacy and excellent tolerability in phase II and III clinical trials, and offer new hope to patients who are currently not taking any prophylactic therapy or not benefitting from their current treatment.

Conclusions

Treatment of chronic migraine is a dynamic and rapidly advancing area of research. New developments in this field have the potential to improve the diagnosis and provide more individualised treatments for this condition. Establishing a culture of prevention is essential for reducing the personal, social and economic burden of chronic migraine.

CGRP and the Trigeminal System in Migraine

OBJECTIVE

The goal of this narrative review is to provide an overview of migraine pathophysiology, with an emphasis on the role of calcitonin gene-related peptide (CGRP) within the context of the trigeminovascular system.

BACKGROUND

Migraine is a prevalent and disabling neurological disease that is characterized in part by intense, throbbing, and unilateral headaches. Despite recent advances in understanding its pathophysiology, migraine still represents an unmet medical need, as it is often underrecognized and undertreated. Although CGRP has been known to play a pivotal role in migraine for the last 2 decades, this has now received more interest spurred by the early clinical successes of drugs that block CGRP signaling in the trigeminovascular system.

DESIGN

This narrative review presents an update on the role of CGRP within the trigeminovascular system. PubMed searches were used to find recent (ie, 2016 to November 2018) published articles presenting new study results. Review articles are also included not as primary references but to bring these to the attention of the reader. Original research is referenced in describing the core of the narrative, and review articles are used to support ancillary points.

RESULTS

The trigeminal ganglion neurons provide the connection between the periphery, stemming from the interface between the primary afferent fibers of the trigeminal ganglion and the meningeal vasculature and the central terminals in the trigeminal nucleus caudalis. The neuropeptide CGRP is abundant in trigeminal ganglion neurons, and is released from the peripheral nerve and central nerve terminals as well as being secreted within the trigeminal ganglion. Release of CGRP from the peripheral terminals initiates a cascade of events that include increased synthesis of nitric oxide and sensitization of the trigeminal nerves. Secreted CGRP in the trigeminal ganglion interacts with adjacent neurons and satellite glial cells to perpetuate peripheral sensitization, and can drive central sensitization of the second-order neurons. A shift in central sensitization from activity-dependent to activity-independent central sensitization may indicate a mechanism driving the progression of episodic migraine to chronic migraine. The pathophysiology of cluster headache is much more obscure than that of migraine, but emerging evidence suggests that it may also involve hypersensitivity of the trigeminovascular system. Ongoing clinical studies with therapies targeted at CGRP will provide additional, valuable insights into the pathophysiology of this disorder.

CONCLUSIONS

CGRP plays an essential role in the pathophysiology of migraine. Treatments that interfere with the functioning of CGRP in the peripheral trigeminal system are effective against migraine. Blocking sensitization of the trigeminal nerve by attenuating CGRP activity in the periphery may be sufficient to block a migraine attack. Additionally, the potential exists that this therapeutic strategy may also alleviate cluster headache as well.

Effect of a calcitonin gene-related peptide-binding L-RNA aptamer on neuronal activity in the rat spinal trigeminal nucleus

Background

Calcitonin gene-related peptide (CGRP) plays a major role in the pathogenesis of migraine and other primary headaches. Spinal trigeminal neurons integrate nociceptive afferent input from trigeminal tissues including intracranial afferents, and their activity is thought to reflect facial pain and headache in man. CGRP receptor inhibitors and anti-CGRP antibodies have been demonstrated to be therapeutically effective in migraine. In parallel, CGRP receptor inhibition has been shown to lower spinal trigeminal neuron activity in animal models of meningeal nociception.

Methods

In a rat model of meningeal nociception, single cell activity of neurons in the spinal trigeminal nucleus with meningeal afferent input was recorded to test a further pharmacological approach, scavenging CGRP with a CGRP-binding l-RNA oligonucleotide, the l-aptamer NOX-C89. Cumulative ascending doses of NOX-C89 were intravenously infused.

Results

Spontaneous activity of spinal trigeminal neurons did not change after 0.05 mg/kg NOX-C89, however, after additional infusion of 0.5 mg/kg and 5 mg/kg NOX-C89, spontaneous activity was dose-dependently reduced. Identical doses of a control l-aptamer had no effect. This pharmacological effect of NOX-C89 was observed 10–25 min after infusion, but no difference was detected in the period 0–5 min. For comparison, the previously investigated CGRP receptor antagonist olcegepant had reduced activity within 5 min after infusion. Alongside the reduced spontaneous activity, after infusion of NOX-C89 the heat-induced neuronal activity was abolished.

Conclusions

Scavenging CGRP by mirror-image RNA aptamers provides further evidence that this approach can be used to control spinal trigeminal activity.

Monoclonal antibodies for chronic pain: a practical review of mechanisms and clinical applications

Context

Monoclonal antibodies are being investigated for chronic pain to overcome the shortcomings of current treatment options.

Objective

To provide a practical overview of monoclonal antibodies in clinical development for use in chronic pain conditions, with a focus on mechanisms of action and relevance to specific classes.

Methods

Qualitative review using a systematic strategy to search for randomized controlled trials, systematic and nonsystematic (narrative) reviews, observational studies, nonclinical studies, and case reports for inclusion. Studies were identified via relevant search terms using an electronic search of MEDLINE via PubMed (1990 to June 2017) in addition to hand-searching reference lists of retrieved systematic and nonsystematic reviews.

Results

Monoclonal antibodies targeting nerve growth factor, calcitonin gene-related peptide pathways, various ion channels, tumor necrosis factor-α, and epidermal growth factor receptor are in different stages of development. Mechanisms of action are dependent on specific signaling pathways, which commonly involve those related to peripheral neurogenic inflammation. In clinical studies, there has been a mixed response to different monoclonal antibodies in several chronic pain conditions, including migraine, neuropathic pain conditions (e.g., diabetic peripheral neuropathy), osteoarthritis, chronic back pain, ankylosing spondylitis, and cancer. Adverse events observed to date have generally been mild, although further studies are needed to ensure safety of monoclonal antibodies in early stages of development, especially where there is an overlap with non-pain-related pathways. High acquisition cost remains another treatment limitation.

Conclusion

Monoclonal antibodies for chronic pain have the potential to overcome the limitations of current treatment options, but strategies to ensure their appropriate use need to be determined.