Emerging target-based paradigms to prevent and treat migraine

Effectiveness of gastrodin for migraine: A meta-analysis

Background

Gastrodia elata Blume (GEB), a traditional Chinese medicine, has been widely used to treat dizziness, numbness of limbs, and infantile convulsion, among other issues. Gastrodin is the main component of GEB. This meta-analysis aimed to evaluate the efficacy and safety of gastrodin in the treatment of migraine.

Methods

Ten electronic databases, namely the Cochrane Library, Embase, EBSCO, PubMed, Web of Science, CENTRAL, CNKI (China National Knowledge Infrastructure), CBM (Chinese Biomedicine Database), WanFang, and VIP (Chinese Scientific Journals Database), were searched for randomized controlled trials (RCTs) of gastrodin for migraine published before September 2021. The data were analyzed by RevMan 5.3 software and evaluated by GRADEpro.

Results

A total of 1,332 subjects were included in 16 RCTs. The meta-analysis showed that gastrodin was significantly effective in treating migraine (RR = 1.21, 95%CI = [1.17, 1.27]), reducing the pain degree (MD = −1.65, 95% CI = [−2.28, −1.02]), reducing the frequency of migraine attack (SMD = −2.77, 95% CI = [−3.92, −1.62]), shortening the duration of migraine attack (SMD = −1.64, 95% CI = [−2.35, −0.93]), and slowing average arterial cerebral blood flow velocity (SMD = −3.19, 95% CI = [−5.21, −1.17]), as well as being safe.

Conclusions

This systematic review revealed gastrodin is effective and safe in the treatment of migraine.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=197094, identifier: CRD42020197094.

Treatment of resistant chronic migraine with anti-CGRP monoclonal antibodies: a systematic review

Background

Resistant chronic migraine is a highly disabling condition which is very difficult to treat. The majority of the treatments for migraine prophylaxis are nonspecific and present weak safety profiles, leading to low adherence and discontinuation. Currently, monoclonal antibodies (mAb) targeting the trigeminal sensory neuropeptide, calcitonin gene-related peptide (CGRP), are available for migraine prophylaxis being the first drugs developed specifically to target migraine pathogenesis. The main objective of the current work is to carry out a systematic review of randomised controlled trials that specifically analyse the effectivity and safety of anti-CGRP mAb, comparatively to placebo, in patients with resistant chronic migraine and possibly fill the literature gap or be a source of information to health professionals. Additionally the current knowledge on migraine, particularly resistant chronic migraine, was revisited and summarised.

Methods

Literature search was carried out on MEDLINE, Scopus, Science Direct and ClinicalTrials.gov database, from inception to December 2021. Articles were selected according to prespecified criteria of inclusion and exclusion. Efficacy and safety outcomes included were: change from baseline in monthly migraine days (MMD); ≥50% reduction of MMD values from baseline; change from baseline in monthly acute migraine-specific medication days (MAMD); Migraine-specific Quality of Life Questionnaire (MSQ); and registered adverse events. Additionally, we used the Cochrane risk of bias tool (RoB 2) to assess the risk of bias of the included studies.

Results

Four studies were included in this systematic review, involving 2811 resistant chronic migraine patients, 667 in a study using erenumab, 838 in a study using fremanezumab and 1306 in two studies using galcanezumab. When compared to placebo, all investigated anti-CGRP mAb and respective doses demonstrate effectiveness in decreasing MMD, reducing acute medication use and improving the MSQ scores, including, sometimes, reversion of chronic to episodic migraine (efficacy outcomes). Regarding the safety outcomes, the number and type of adverse events did not differ between anti-CGRP mAb-treated and placebo groups.

Conclusions

Anti-CGRP or anti-CGRP receptor monoclonal antibodies are a promising preventive migraine therapy which can be particularly useful for resistant chronic migraine patients.

Atogepant: an emerging treatment for migraine

INTRODUCTION

Until recently, only nonspecific and not always well-tolerated medications were available for migraine prophylaxis. Currently, specific drugs such as calcitonin gene-related peptide (CGRP) monoclonal antibodies and second-generation gepants are marketed for migraine treatment. Atogepant, an orally active small molecule, is a potent, selective antagonist of the CGRP receptor and is the only gepant authorized exclusively for episodic migraine prophylaxis in adults.

AREAS COVERED

Using literature obtained from PubMed, Scopus, Web of Science, Cochrane, and ClinicalTrials.gov (up to February 13^rd, 2022), the authors summarize and evaluate the available data on atogepant for the prophylaxis of episodic migraine.

EXPERT OPINION

From pivotal trials, the efficacy and tolerability of atogepant in episodic migraine prophylaxis seem comparable to those of CGRP monoclonal antibodies, even if comparative studies have not been conducted. To date, limited information is available on atogepant, including the optimal dose and duration of therapy; hence, it is difficult to establish whether it could be a first-line drug for migraine prophylaxis. Furthermore, it is important to evaluate if atogepant use is associated with the risk of cardiovascular and cerebrovascular events, which could result from potent and persistent blockade of vasodilation by CGRP.

Migraine: Calcium Channels and Glia

Migraine is a common neurological disease that affects about 11% of the adult population. The disease is divided into two main clinical subtypes: migraine with aura and migraine without aura. According to the neurovascular theory of migraine, the activation of the trigeminovascular system (TGVS) and the release of numerous neuropeptides, including calcitonin gene-related peptide (CGRP) are involved in headache pathogenesis. TGVS can be activated by cortical spreading depression (CSD), a phenomenon responsible for the aura. The mechanism of CSD, stemming in part from aberrant interactions between neurons and glia have been studied in models of familial hemiplegic migraine (FHM), a rare monogenic form of migraine with aura. The present review focuses on those interactions, especially as seen in FHM type 1, a variant of the disease caused by a mutation in CACNA1A, which encodes the α1A subunit of the P/Q-type voltage-gated calcium channel.

Demographic and clinical characteristics of prevention-eligible patients with migraine in the US: a linked national survey and administrative claims database study

OBJECTIVE

To characterize burden of migraine in prevention-eligible patients compared with prevention non-eligible patients in the United States (US). Receipt of preventive therapy was also examined among prevention-eligible patients.

METHODS

This retrospective study utilized data from the 2017 US National Health and Wellness Survey linked with medical and pharmacy claims. Patients aged ≥18 years who self-reported experiencing migraine and had confirmed evidence of migraine (≥1 medical or pharmacy claim) were included. Prevention eligibility was based on number of headache days in the past 30 days (prevention-eligible: ≥4 and prevention non-eligible: <4). Descriptive statistics summarized study variables; bivariate and multivariable analyses were conducted to examine the association of prevention-eligibility status with outcomes.

RESULTS

Analyses included 450 patients, 291 (65%) prevention-eligible, and of these 56 (19%) received preventive therapy. Overall, patients were 42.98 ± 14.51 years old; 84% were female. Prevention-eligible patients reported significantly more migraine headache days in the past 6 months (29.27 ± 37.96 vs. 8.61 ± 7.88), had lower mental component summary scores (35.80 ± 2.73 vs. 37.90 ± 2.96), and more presenteeism (47.30 ± 2.98% vs. 37.90 ± 2.60%), overall work impairment (46.30 ± 2.87% vs. 37.90 ± 2.55%) and activity days missed due to migraine (8.16 ± 3.05 vs. 3.82 ± 1.58) than prevention non-eligible patients (all p<.001). Prevention-eligible patients receiving preventive therapy reported more migraine headache days during the past month (9.21 ± 7.99 vs. 6.06 ± 7.10; p=.002) and activity days lost due to migraine (18.39 ± 28.08 vs. 10.69 ± 21.43, p=.015) than those not receiving preventive therapy.

CONCLUSIONS

Prevention-eligible patients experience greater burden due to migraine, including more headache days, worse health-related quality-of-life, and greater work and activity impairment than prevention non-eligible patients.

Calcitonin gene-related peptide (CGRP)-targeted therapies as preventive and acute treatments for migraine-The monoclonal antibodies and gepants

Calcitonin Gene-Related Peptide (CGRP) plays a pivotal role in migraine pathophysiology. Two types of CGRP function-blocking modalities, monoclonal antibodies, and small molecules (gepants), have been developed to target the CGRP ligands and CGRP receptors. Four CGRP monoclonal antibodies have received FDA approval for the prevention of migraine: erenumab, fremanezumab, galcanezumab, and eptinezumab. Two gepants have been approved by the FDA for the acute treatment of migraine: ubrogepant and rimegepant. Multiple clinical trials of the CGRP monoclonal antibodies and gepants, and now some open-label long-term extension data, established their efficacy, safety, and tolerability. In this chapter, we summarize the major clinical trials, pharmacokinetic insights, safety and tolerability profiles, and real-world data (if available) of the CGRP monoclonal antibodies and gepants.

Migraine and Ischemic Stroke: Deciphering the Bidirectional Pathway

Migraine and stroke are common, disabling neurological conditions with several theories being proposed to explain this bidirectional relationship. Migraine is considered as a benign neurological disorder, but research has revealed a connection between migraine and stroke, predominantly those having migraine with aura (MA). Among migraineurs, females with MA are more susceptible to ischemic stroke and may have a migrainous infarction. Migrainous infarction mostly occurs in the posterior circulation of young women. Although there are several theories about the potential relationship between MA and stroke, the precise pathological process of migrainous infarction is not clear. It is assumed that cortical spreading depression (CSD) might be one of the essential factors for migrainous infarction. Other factors that may contribute to migrainous infarction may be genetic, hormonal fluctuation, hypercoagulation, and right to left cardiac shunts. Antimigraine drugs, such as ergot alkaloids and triptans, are widely used in migraine care. Still, they have been found to cause severe vasoconstriction, which may result in the development of ischemia. It is reported that patients with stroke develop migraines during the recovery phase. Both experimental and clinical data suggest that cerebral microembolism can act as a potential trigger for MA. Further studies are warranted for the treatment of migraine, which may lead to a decline in migraine-related stroke. In this present article, we have outlined various potential pathways that link migraine and stroke.

Fremanezumab for the preventive treatment of migraine in adults

Introduction: The Calcitonin Gene-Related Peptide (CGRP) has been implicated in migraine pathophysiology due to its role in neurogenic inflammation and transmission of trigeminovascular nociceptive signal. New molecules targeting CGRP and its receptor have been developed as migraine-specific preventative treatments. Fremanezumab (or TEV-48,125, LBR-101), a human monoclonal antibody against CGRP, has been recently approved for clinical use by FDA and EMA. Areas covered: This paper briefly discusses the calcitonin family of neurotransmitters and resultant activation pathways and in-depth the chemical properties, pharmacodynamics, pharmacokinetics, clinical efficacy and safety of Fremanezumab for the prophylactic treatment of migraine. Expert opinion: Fremanezumab, a migraine-specific drug, is effective and safe as a prophylactic treatment of chronic and episodic migraine. As a monoclonal antibody, it was not associated to liver toxicity and is not expected to interact with other drugs. The long half-life might improve patients' compliance. Long-term effects of CGRP block in cardiovascular, grastrointestinal and bone functions should be evaluated in ongoing trials, since CGRP is involved in multiple biological activities in the human body. Nevertheless, targeting CGRP itself allows the receptor binding with other ligands involved in several physiological functions. Thus, the long-term treatment with Fremanezumab is expected to be associated with a lower risk of severe adverse effects.

Synthesis of a CGRP Receptor Antagonist via an Asymmetric Synthesis of 3-Fluoro-4-aminopiperidine

A practical and efficient enantioselective synthesis of the calcitonin gene-related peptide receptor antagonist 1 has been developed. The key structural component of the active pharmaceutical ingredient is a syn-1,2-amino-fluoropiperidine 4. Two approaches were developed to synthesize this important pharmacophore. Initially, Ru-catalyzed asymmetric hydrogenation of fluoride-substituted enamide 8 enabled the synthesis of sufficient quantities of compound 1 to support early preclinical studies. Subsequently, a novel, cost-effective route to this intermediate was developed utilizing a dynamic kinetic asymmetric transamination of ketone 9. This synthesis also features a robust Ullmann coupling to install a bis-aryl ether using a soluble Cu(I) catalyst. Finally, an enzymatic desymmetrization of meso-diester 7 was exploited for the construction of the γ-lactam moiety in 1.

Fremanezumab as a preventive treatment for episodic and chronic migraine

Introduction: The importance of calcitonin gene-related peptide (CGRP) in migraine pathogenesis is well established. Fremanezumab is a humanized IgG2a monoclonal antibody that binds to CGRP. Areas covered: In this paper, we review the development of fremanezumab, from early development into approval. The authors focus on the efficacy and safety of fremanezumab in both migraine stages. The authors highlight studies conducted in special populations and focus on unique aspects of its development, as well as on clinical pearls supported by the data. Expert opinion: Fremanezumab was shown to be effective in episodic and chronic migraine, with a monthly and quarterly dose of administration, as monotherapy and add-on therapy. As with other monoclonal antibodies, the anti-CGRP onset of action was remarkably quick, and the effect seems to be maintained over time. No overt safety concerns emerged from the clinical studies, although long-term surveillance is necessary.

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.

Tonic regulation of middle meningeal artery diameter by ATP-sensitive potassium channels

Activation of ATP-sensitive potassium (KATP) channels in arterial smooth muscle (ASM) contributes to vasodilation evoked by a variety of endogenous and exogenous compounds. Although controversial, activation of KATP channels by neuropeptides such as calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase activating peptide (PACAP) in the trigeminovascular system, including the middle meningeal artery (MMA), has been linked to migraine headache. The objective of the current study was to determine if ongoing KATP channel activity also influences MMA diameter. In the absence of other exogenous compounds, the KATP channel inhibitors glibenclamide and PNU37883A induced constriction of isolated and pressurized MMAs. In contrast, KATP channel inhibition did not alter cerebral artery diameter. Consistent with tonic KATP activity in MMA, glibenclamide also induced ASM membrane potential depolarization and increased cytosolic Ca2+. Inhibitors of cAMP-dependent protein kinase (PKA) abolished basal KATP activation in MMA and caused a marked decrease in sensitivity to the synthetic KATP channel opener, cromakalim. In vivo MMA constriction in response to gibenclamide was observed using two-photon imaging of arterial diameter. Together these results indicate that PKA-mediated tonic KATP channel activity contributes to the regulation of MMA diameter.

From LBR-101 to Fremanezumab for Migraine

Calcitonin gene-related peptide (CGRP) is a neuropeptide of importance in migraine pathogenesis. Its central role in migraine was proven pharmacologically by the development of CGRP receptor antagonists. Monoclonal antibodies targeting CGRP or its receptor are effective in the preventive treatment of episodic and chronic migraine and are considered potential breakthroughs in their treatment. Fremanezumab (previously known as TEV-48125, LBR-101, or RN-307) is a humanized IgG2a monoclonal antibody that binds to CGRP. The development of this antibody validated the role of CGRP in chronic migraine and the drug has been recently approved in the US by the FDA, while it continues to be reviewed by other regulatory agencies. Herein we provide an in-depth review of its development. We start by summarizing its in vitro and in vivo pharmacology, and the phase I studies. We then review the late-stage clinical development, with a focus on its efficacy, safety, similarities, and uniqueness relative to other CGRP antibodies. We close by discussing lessons learned on the mechanisms of migraine and areas for future development and exploration.

Basic Considerations for the Use of Monoclonal Antibodies in Migraine

BACKGROUND

Migraine impacts more than 36 million people in the United States and 1 billion people worldwide. Despite the increasing availability of acute and preventive therapies, there is still tremendous unmet need. Potential treatments in development include monoclonal antibodies (mAbs). Appropriate use of these “biologic” treatments will necessitate an understanding of the aspects that distinguish them from traditional medications.

AIM

Many drug classes are prescribed for migraine treatment, but all have limitations. Recently, calcitonin gene-related peptide (CGRP) activity has shown a significant promise as a target for preventive therapy. In this review, we provide an overview of the potential role of CGRP mAbs in migraine, with a focus on their design, pharmacokinetics, safety, and immunogenicity.

CONCLUSIONS

The CGRP mAbs are an innovative new therapy for migraine and address the need for effective and tolerable preventive options. MAbs, including those that target CGRP or its receptor, bind to a target with high specificity and affinity and lead to few off-target adverse effects, although mechanism-based adverse reactions may occur. Unlike other therapeutic antibodies used to treat neurologic disease, CGRP mAbs do not have a target within the immune system and have been designed to avoid altering the immune system. The safety and efficacy of mAbs against CGRP or its receptors are being investigated in clinical development programs, and the first of these therapies has received regulatory approval in the United States.

Antigens and Antibodies in Disease With Specifics About CGRP Immunology

Growth in knowledge about calcitonin gene-related peptide (CGRP) in the pathophysiology of migraine brought CGRP antagonism to headache medicine. Failures in development of small molecule CGRP receptor antagonists and increasing knowledge and use of monoclonal antibodies (mAbs) in medicine led to the breakthrough development of large molecule anti-CGRP mAbs: eptinezumab, erenumab, fremanezumab, and galcanezumab. This specifics about CGRP immunology aims to outline: (1) knowledge needed for CGRP antagonism and (2) developmental issues of specific CGRP antagonists for provider use. This clinically oriented review documents IgG structure and function; state of the art of monoclonal IgG production and ligand-antigen-antibodies in migraine therapeutics contributing to immunogenic risks and off-target toxicities. Specifics to CGRP ligand, receptor, antagonism, and molecules, small and large, complete this review. Completion will facilitate assessment of the similarities, differences, and application of the forthcoming anti-CGRP receptor and ligand antagonists for patients.

Side effects associated with current and prospective antimigraine pharmacotherapies

INTRODUCTION

Migraine is a neurovascular disorder. Current acute specific antimigraine pharmacotherapies target trigeminovascular 5-HT1B/1D, 5-HT1F and CGRP receptors but, unfortunately, they induce some cardiovascular and central side effects that lead to poor treatment adherence/compliance. Therefore, new antimigraine drugs are being explored. Areas covered: This review considers the adverse (or potential) side effects produced by current and prospective antimigraine drugs, including medication overuse headache (MOH) produced by ergots and triptans, the side effects observed in clinical trials for the new gepants and CGRP antibodies, and a section discussing the potential effects resulting from disruption of the cardiovascular CGRPergic neurotransmission. Expert opinion: The last decades have witnessed remarkable developments in antimigraine therapy, which includes acute (e.g. triptans) and prophylactic (e.g. β-adrenoceptor blockers) antimigraine drugs. Indeed, the triptans represent a considerable advance, but their side effects (including nausea, dizziness and coronary vasoconstriction) preclude some patients from using triptans. This has led to the development of the ditans (5-HT1F receptor agonists), the gepants (CGRP receptor antagonists) and the monoclonal antibodies against CGRP or its receptor. The latter drugs represent a new hope in the antimigraine armamentarium, but as CGRP plays a role in cardiovascular homeostasis, the potential for adverse cardiovascular side effects remains latent.

Current management: migraine headache

Migraine varies in its frequency, severity, and impact; treatment should consider these variations and the patient's needs and goals. Migraine pharmacologic treatment may be acute (abortive) or preventive (prophylactic), and patients often require both. New medication devices are available or in development, including an intracutaneous, microneedle system of zolmitriptan and sumatriptan, and breath-powered powder sumatriptan intranasal treatment. Lasmiditan, a 5-HT1F receptor agonist, is in development for acute treatment, as are small molecule calcitonin gene-related peptide (CGRP) receptor antagonists (Gepants) for acute and preventive treatment. Antibodies to CGRP and its receptor are being developed for migraine prevention. All 4 treatments are effective and have, as of yet, no safety concerns.

The role of calcitonin gene-related peptide in peripheral and central pain mechanisms including migraine

Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide found primarily in the C and Aδ sensory fibers arising from the dorsal root and trigeminal ganglia, as well as the central nervous system. Calcitonin gene-related peptide was found to play important roles in cardiovascular, digestive, and sensory functions. Although the vasodilatory properties of CGRP are well documented, its somatosensory function regarding modulation of neuronal sensitization and of enhanced pain has received considerable attention recently. Growing evidence indicates that CGRP plays a key role in the development of peripheral sensitization and the associated enhanced pain. Calcitonin gene-related peptide is implicated in the development of neurogenic inflammation and it is upregulated in conditions of inflammatory and neuropathic pain. It is most likely that CGRP facilitates nociceptive transmission and contributes to the development and maintenance of a sensitized, hyperresponsive state not only of the primary afferent sensory neurons but also of the second-order pain transmission neurons within the central nervous system, thus contributing to central sensitization as well. The maintenance of a sensitized neuronal condition is believed to be an important factor underlying migraine. Recent successful clinical studies have shown that blocking the function of CGRP can alleviate migraine. However, the mechanisms through which CGRP may contribute to migraine are still not fully understood. We reviewed the role of CGRP in primary afferents, the dorsal root ganglion, and in the trigeminal system as well as its role in peripheral and central sensitization and its potential contribution to pain processing and to migraine.

Anti-CGRP monoclonal antibodies in migraine: current perspectives

Migraine is a highly disabling neurological pain disorder in which management is frequently problematic. Most abortive and preventative treatments employed are classically non-specific, and their efficacy and safety and tolerability are often unsatisfactory. Mechanism-based therapies are, therefore, needed. Calcitonin gene-related peptide (CGRP) is recognized as crucial in the pathophysiology of migraine, and new compounds that target the peptide have been increasingly explored in recent years. First tested were CGRP receptor antagonists; they proved effective in acute migraine treatment in several trials, but were discontinued due to liver toxicity in long-term administration. Monoclonal antibodies against CGRP (LY2951742, ALD-403, and LBR-101/TEV-48125) or its receptor (AMG334) were subsequently developed. As reviewed in this study, numerous phase 1 and 2 trials and preliminary results of phase 3 trials have shown a good safety/tolerability profile and efficacy in migraine prevention, especially in high frequent episodic and chronic forms. Being macromolecules, these mAbs are not suitable for oral administration; however, their intravenous or subcutaneous delivery can be performed at relatively low frequency-every month or even quarterly-which enhances patients' compliance. Although not all migraineurs respond to this treatment, and longer administration periods will be needed to assess long-term effects, the results so far obtained are extraordinarily promising. The future introduction of mAbs on the market will probably represent a turning point for prevention similar to that represented by triptans for abortive treatment in migraine.

Therapeutic antibodies against CGRP or its receptor

CGRP is an extensively studied neuropeptide that has been implicated in the pathophysiology of migraine. While a number of small molecule antagonists against the CGRP receptor have demonstrated that targeting this pathway is a valid and effective way of treating migraine, off-target hepatoxicity and formulation issues have hampered the development for regulatory approval of any therapeutic in this class. The development of monoclonal antibodies to CGRP or its receptor as therapeutic agents has allowed this pathway to be re-investigated. Herein we review why CGRP is an ideal target for the prevention of migraine and describe four monoclonal antibodies against either CGRP or its receptor that are in clinical development for the treatment of both episodic and chronic migraine. We describe what has been publically disclosed about their clinical trials and future clinical development plans.

TEV-48125: a review of a monoclonal CGRP antibody in development for the preventive treatment of migraine

Calcitonin gene-related peptide (CGRP) is a 37-amino-acid neuropeptide whose involvement in migraine pathophysiology is well established. Originally migraine was believed to be a disease of the vasculature, but research has highlighted this to be a disease of the brain with CGRP playing an important role. While targeting CGRP using small molecule antagonists against the receptor has been effective, long-term use of these agents has not been possible due to safety concerns and/or formulation challenges. Recent advances in therapeutic antibodies have opened up new possibilities for treatment of migraine. TEV-48125 is one of four monoclonal antibodies targeting CGRP or its receptors, currently in development for the preventive treatment of migraine. This article discusses the in vitro and in vivo pharmacology of TEV-48125 as well as highlighting its safety profile through the six Phase 1 studies that have been conducted. Finally, the current state of development and future studies for TEV-48125 will be reviewed.

Hypoxia facilitates neurogenic dural plasma protein extravasation in mice: a novel animal model for migraine pathophysiology

Migraine animal models generally mimic the onset of attacks and acute treatment processes. A guinea pig model used the application of meta-chlorophenylpiperazine (mCPP) to trigger immediate dural plasma protein extravasation (PPE) mediated by 5-HT_2B receptors. This model has predictive value for antimigraine drugs but cannot explain the delayed onset of efficacy of 5-HT_2B receptor antagonists when clinically used for migraine prophylaxis. We found that mCPP failed to induce dural PPE in mice. Considering the role 5-HT_2B receptors play in hypoxia-induced pulmonary vessel muscularization, we were encouraged to keep mice under hypoxic conditions and tested whether this treatment will render them susceptible to mCPP-induced dural PPE. Following four-week of hypoxia, PPE, associated with increased transendothelial transport, was induced by mCPP. The effect was blocked by sumatriptan. Chronic application of 5-HT_2B receptor or nitric oxide synthase blockers during hypoxia prevented the development of susceptibility. Here we present a migraine model that distinguishes between a migraine-like state (hypoxic mice) and normal, normoxic mice and mimics processes that are related to chronic activation of 5-HT_2B receptors under hypoxia. It seems striking, that chronic endogenous activation of 5-HT_2B receptors is crucial for the sensitization since 5-HT_2B receptor antagonists have strong, albeit delayed migraine prophylactic efficacy.

Episodic and chronic migraine headache: breaking down barriers to optimal treatment and prevention

Migraine is a common disabling primary headache disorder that affects an estimated 36 million Americans. Migraine headaches often occur over many years or over an individual's lifetime. By definition, episodic migraine is characterized by headaches that occur on fewer than 15 days per month. According to the recent International Classification of Headache Disorders (third revision) beta diagnostic criteria, chronic migraine is defined as "headaches on at least 15 days per month for at least 3 months, with the features of migraine on at least 8 days per month." However, diagnostic criteria distinguishing episodic from chronic migraine continue to evolve. Persons with episodic migraine can remit, not change, or progress to high-frequency episodic or chronic migraine over time. Chronic migraine is associated with a substantially greater personal and societal burden, more frequent comorbidities, and possibly with persistent and progressive brain abnormalities. Many patients are poorly responsive to, or noncompliant with, conventional preventive therapies. The primary goals of migraine treatment include relieving pain, restoring function, and reducing headache frequency; an additional goal may be preventing progression to chronic migraine. Although all migraineurs require abortive treatment, and all patients with chronic migraine require preventive treatment, there are no definitive guidelines delineating which persons with episodic migraine would benefit from preventive therapy. Five US Food and Drug Association strategies are approved for preventing episodic migraine, but only injections with onabotulinumtoxinA are approved for preventing chronic migraine. Identifying persons who require migraine prophylaxis and selecting and initiating the most appropriate treatment strategy may prevent progression from episodic to chronic migraine and alleviate the pain and suffering associated with frequent migraine.

Translational Pharmacodynamics of Calcitonin Gene-Related Peptide Monoclonal Antibody LY2951742 in a Capsaicin-Induced Dermal Blood Flow Model

LY2951742, a monoclonal antibody targeting calcitonin gene-related peptide (CGRP), is being developed for migraine prevention and osteoarthritis pain. To support the clinical development of LY2951742, capsaicin-induced dermal blood flow (DBF) was used as a target engagement biomarker to assess CGRP activity in nonhuman primates and healthy volunteers. Inhibition of capsaicin-induced DBF in nonhuman primates, measured with laser Doppler imaging, was dose dependent and sustained for at least 29 days after a single intravenous injection of the CGRP antibody. This information was used to generate a pharmacokinetic/pharmacodynamic model, which correctly predicted inhibition of capsaicin-induced DBF in humans starting at a single subcutaneous 5-mg dose. As expected, the degree of inhibition in capsaicin-induced DBF increased with higher LY2951742 plasma concentrations. Utilization of this pharmacodynamic biomarker with pharmacokinetic data collected in phase I studies provided the dose-response relationship that assisted in dose selection for the phase II clinical development of LY2951742.

Targeting CGRP: A New Era for Migraine Treatment

Migraine is a highly prevalent headache disease that typically affects patients during their most productive years. Despite significant progress in understanding the underlying pathophysiology of this disorder, its treatment so far continues to depend on drugs that, in their majority, were not specifically designed for this purpose. The neuropeptide calcitonin gene-related peptide (CGRP) has been indicated as playing a critical role in the central and peripheral pathways leading to a migraine attack. It is not surprising that drugs designed to specifically block its action are gaining remarkable attention from researchers in the field with, at least so far, a safe risk profile. In this article, we highlight the evolution from older traditional treatments to the innovative CGRP target drugs that are revolutionizing the way to approach this debilitating neurological disease. We provide a brief introduction on pathophysiology of migraine and details on the characteristic, function, and localization of CGRP to then focus on CGRP receptor antagonists (CGRP-RAs) and CGRP monoclonal antibodies (CGRP mAbs).

The therapeutic potential of novel anti-migraine acute therapies

INTRODUCTION

Migraine is a highly disabling neurovascular disorder. 'The complex and multifactorial properties of migraine pathogenesis provide the opportunity to identify new therapeutic targets from a wide range of receptors.

AREAS COVERED

In this editorial, the authors focus on future pharmacological interventions for acute migraine including: 5-HT receptors and their agonists, calcitonin gene-related peptide receptors and their antagonists, PAC1 receptors and their antagonists, glutamate receptors and some of their antagonists as well as transient receptor potential channels and their antagonists. The authors also discuss preventative treatments for migraine that are currently in development.

EXPERT OPINION

Future pharmaceutical research that looks at the well-known mechanisms involved in the pathophysiology of migraine should aim to overcome the existing limitations of each pharmacological class and their side effects. There has lately been particular interest in the role of glutamate receptors, particularly metabotropic glutamate receptors, in the pathophysiology of migraine. These receptors may be potentially viable drug targets for migraine in the future.

Migraine equivalents as part of migraine syndrome in childhood

BACKGROUND

Migraine equivalents are common clinical conditions without a headache component, occurring as repeated episodes with complete remission between episodes. They include abdominal migraine, cyclical vomiting, benign paroxysmal vertigo, and benign paroxysmal torticollis. Other clinical entities, such as motion sickness and limb pain have been associated with migraine. We aimed to investigate the prevalence of migraine equivalents in a large population of children referred to a pediatric headache center and to analyze the possible relationship between migraine equivalents and headache features.

METHODS

A total of 1134 of children/adolescents (73.2% with migraine and 26.8% with tension-type headache) were included. Patients were divided into two groups according to the episode frequency (high and low). Pain intensity was rated on a three-level graduate scale (mild, moderate, and severe pain).

RESULTS

Migraine equivalents were reported in 70.3% of patients. Abdominal migraine (48.9%), limb pain (43.9%), and motion sickness (40.5%) were the most common migraine equivalents. Although headache type (migraine or tension-type headache) did not correlate with migraine equivalents presence (χ(2) = 33.2; P = 0.27), high frequency of headache episodes correlated with the occurrence of migraine equivalents. Moreover, migraine equivalents indicated a protective role for some accompanying feature of the headache episode.

CONCLUSIONS

Our results suggest that migraine equivalents should not be considered merely as headache precursors, but they as part of the migrainous syndrome. Thus, their inclusion among the diagnostic criteria for pediatric migraine/tension-type headache is useful.

Methodological issues in studying trigger factors and premonitory features of migraine

OBJECTIVE

In this review, we focus on migraine as a chronic disorder with episodic attacks (CDEA). We aim to review methodological approaches to studying trigger factors and premonitory features that often precede a migraine attack.

BACKGROUND

Migraine attacks are sometimes initiated by trigger factors, exposures which increase the probability of an attack. They are heralded by premonitory features, symptoms which warn of an impending attack.

DESIGN/METHODS

We review candidate predictors of migraine attack and discuss the methodological issues and approaches to studying attack prediction and suggest that electronic diaries may be the method of choice.

CONCLUSION

Establishing the relationship between antecedent events and headaches is a formidable challenge. Successfully addressing this challenge should provide insights into disease mechanisms and lead to new strategies for treatment. In the second paper in this series, we review the available literature on trigger factors and premonitory features.

Serotonin and sensory nerves: meeting in the cardiovascular system

Blood pressure regulation by 5-HT has proven to be a complex story to unravel. The work by Cuesta et al., in this issue of Vascular Pharmacology adds another layer of complexity by providing sound in vivo data that 5-HT, through the 5-HT7 receptor, can inhibit the vasodepressor actions of the sensory nervous system and thereby promote blood pressure maintenance. This interaction of 5-HT with the sensory nervous system is inhibitory, whereas 5-HT is understood to be stimulatory in other systems. Moreover, activation of the 5-HT7 receptor has been linked to both reduction and elevation of blood pressure. These interactions are discussed in this mini-review, as are potential steps forward in understanding the interplay of 5-HT, the sensory nervous system and blood pressure.

Evaluation of cardiovascular parameters in cynomolgus monkeys following IV administration of LBR-101, a monoclonal antibody against calcitonin gene-related peptide

Calcitonin gene-related peptide (CGRP) is a well-validated target for migraine therapy and a known potent systemic vasodilator. LBR-101 is a monoclonal antibody against CGRP in clinical development for the preventive treatment of episodic and chronic migraine. Understanding the hemodynamic and cardiovascular consequences of chronic CGRP inhibition is therefore warranted. Given the conservation in CGRP sequence between monkeys and humans, addressing this question in monkeys is ideal as it allows dosing at super-therapeutic levels. To this end, two independent studies were conducted in monkeys: a single dedicated cardiovascular safety study and a repeat-dose, chronic study, both with electrocardiogram and hemodynamic assessments. LBR-101 was very well tolerated in both studies, with no clinically significant changes noted in any hemodynamic parameter, nor any relevant changes noted in any ECG parameter. In cynomolgus monkeys, cardiovascular and hemodynamic parameters do not appear to be affected by long-term inhibition of CGRP with LBR-101.

Monoclonal antibodies for migraine: preventing calcitonin gene-related peptide activity

Calcitonin gene-related peptide (CGRP) is a well-studied neuropeptide of relevance for migraine pathophysiology. Jugular levels of CGRP are increased during migraine attacks, and intravenous CGRP administration induces migraine-like headache in most individuals with migraine. Several CGRP receptor antagonists (CGRP-RAs) were shown to be effective for the acute treatment of migraine, validating the target for the treatment of migraine. However, for a number of reasons, including issues of liver toxicity with chronic use, the development of CGRP-RAs has yet to produce a viable clinical therapeutic. Development of monoclonal antibodies (mAbs) targeting the CGRP pathway is an alternative approach that should avoid many of the issues seen with CGRP-RAs. The exquisite target specificity, prolonged half-lives, and reduced potential for hepatotoxicity and drug-drug interactions make mAbs suitable for the preventive treatment of migraine headaches. This manuscript provides an overview of the role of CGRP in the pathophysiology of migraine, followed by a review of the clinical development of CGRP-RAs. Some basic concepts on antibodies are then discussed along with the publicly disclosed information on the development of mAbs targeting the CGRP pathway.

Cardiovascular and hemodynamic parameters in women following prolonged CGRP inhibition using LBR-101, a monoclonal antibody against CGRP

BACKGROUND

The vascular effects of acute calcitonin gene-related peptide (CGRP) inhibition are well described, but the effects of sustained inhibition warrant further exploration in humans.

OBJECTIVES

The objective of this article is to assess the effects of sustained CGRP inhibition on blood pressure, heart rate, and ECGs in healthy women ≥ 40 years of age.

METHODS

In this double-blind, placebo-controlled study, 31 women (mean age = 56) were randomized to receive placebo or an anti-CGRP monoclonal antibody at doses up to 2000 mg. Participants were confined for seven days and followed for 168 days. Cardiac telemetry was conducted for eight hours after infusion completion. Hemodynamic assessments and ECGs were conducted six times during Day 1 and periodically for three months.

RESULTS

No clinically relevant changes in systolic or diastolic blood pressure, heart rate, or ECG parameters (RR, PR, QRS, or QTcF) were observed when comparing baseline vs. post-dose time-points or in-between groups. No significant changes were seen for adjusted QTcF (baseline subtracted and placebo and baseline subtracted). No significant differences or relevant abnormalities were seen when comparing parameters obtained at Tmax vs. any other time-point.

CONCLUSION

Sustained CGRP inhibition was not associated with hemodynamic or ECG changes in a population at an increased age risk for cardiovascular events.

Emerging targets in migraine

Migraine is a common and highly disabling neurological disorder. Despite the complexity of its pathophysiology, substantial advances have been achieved over the past 20 years in its understanding, as well as the development of pharmacological treatment options. The development of serotonin 5-HT(1B/1D) receptor agonists ("triptans") substantially improved the acute treatment of migraine attacks. However, many migraineurs do not respond satisfactorily to triptans and cardiovascular co-morbidities limit their use in a significant number of patients. As migraine is increasingly considered to be a disorder of the brain, and preclinical and clinical data indicate that the observed vasodilation is merely an epiphenomenon, research has recently focused on the development of neurally acting compounds that lack vasoconstrictor properties. This review highlights the most important pharmacological targets for which compounds have been developed that are highly likely to enter or have already advanced into clinical trials for the acute and preventive treatment of migraine. In this context, preclinical and clinical data on compounds acting on calcitonin gene-related peptide or its receptor, the 5-HT(1F) receptor, nitric oxide synthase, and acid-sensing ion channel blockers are discussed.

Efficacy, safety, and tolerability of telcagepant in the treatment of acute migraine: a meta-analysis

Although triptans are widely used for treating acute migraine, they are contraindicated or not effective in a large proportion of patients. Hence, alternative treatments are needed. Calcitonin gene-related peptide receptor antagonists, such as telcagepant, have been under investigation as a treatment for acute migraine. A meta-analysis of the efficacy of telcagepant vs. placebo and triptans (zolmitriptan or rizatriptan) was performed. Randomized controlled trials were indentified from databases using the following search terms: migraine; calcitonin gene-related peptide; calcitonin gene-related peptide receptor antagonists; efficacy; safety, and telcagepant. The primary outcome measure was pain freedom 2 hours after first treatment. The secondary outcome measure was pain relief 2 hours after first treatment. Eight trials were included in the meta-analysis (telcagepant = 4011 participants). The difference in pain freedom at 2 hours significantly favored telcagepant over placebo (odds ratio = 2.70, 95% confidence interval = 2.27-3.21, P < 0.001) and triptans over telcagepant (odds ratio = 0.68, 95% confidence interval = 0.56-0.83, P < 0.001). The difference in pain relief at 2 hours significantly favored telcagepant over placebo (odds ratio = 2.48, 95% confidence interval = 2.18-2.81, P < 0.001). The difference in pain relief at 2 hours did not significantly favor telcagepant over triptans or vice versa (odds ratio = 0.76, 95% confidence interval = 0.57-1.01, P = 0.061). These findings indicate that telcagepant can be effective for treating acute migraine. Calcitonin gene-related peptide receptor antagonists represent a potentially important alternative means of treating acute migraine.

Safety and tolerability of LBR-101, a humanized monoclonal antibody that blocks the binding of CGRP to its receptor: Results of the Phase 1 program

BACKGROUND

LBR-101 is a fully humanized monoclonal antibody that binds to calcitonin gene-related peptide.

OBJECTIVE

The objective of this article is to characterize the safety and tolerability of LBR-101 when administered intravenously to healthy volunteers, by presenting the pooled results of the Phase 1 program.

METHODS

LBR-101 was administered to 94 subjects, while 45 received placebo. Doses ranged from 0.2 mg to 2000 mg given once (Day 1), as a single IV infusion, or up to 300 mg given twice (Day 1 and Day 14).

RESULTS

Subjects receiving placebo reported an average of 1.3 treatment-emerging adverse events vs 1.4 per subject among those receiving any dose of LBR-101, and 1.6 in those receiving 1000 mg or higher. Treatment-related adverse events occurred in 21.2% of subjects receiving LBR-101, compared to 17.7% in those receiving placebo. LBR-101 was not associated with any clinically relevant patterns of change in vital signs, ECG parameters, or laboratory findings. The only serious adverse event consisted of "thoracic aortic aneurysm" in a participant later found to have an unreported history of Ehlers-Danlos syndrome.

CONCLUSION

Single IV doses of LBR-101 ranging from 0.2 mg up to 2000 mg and multiple IV doses up to 300 mg were well tolerated. Overt safety concerns have not emerged. A maximally tolerated dose has not been identified.

ATP P2X3 receptors and neuronal sensitization

Increasing evidence indicates the importance of extracellular adenosine triphosphate (ATP) in the modulation of neuronal function. In particular, fine control of ATP release and the selective and discrete ATP receptor operation are crucial elements of the crosstalk between neuronal and non-neuronal cells in the peripheral and central nervous systems. In peripheral neurons, ATP signaling gives an important contribution to neuronal sensitization, especially that involved in neuropathic pain. Among other subtypes, P2X3 receptors expressed on sensory neurons are sensitive even to nanomolar concentrations of extracellular ATP, and therefore are important transducers of pain stimuli. P2X3 receptor function is highly sensitive to soluble factors like neuropeptides and neurotrophins, and is controlled by transduction mechanisms, protein-protein interactions and discrete membrane compartmentalization. More recent findings have demonstrated that P2X3 receptors interact with the synaptic scaffold protein calcium/calmodulin-dependent serine protein kinase (CASK) in a state dependent fashion, indicating that CASK plays a crucial role in the modulation of P2X3 receptor stability and efficiency. Activation of P2X3 receptors within CASK/P2X3 complex has important consequences for neuronal plasticity and possibly for the release of neuromodulators and neurotransmitters. Better understanding of the interactome machinery of P2X3 receptors and their integration with other receptors and channels on neuronal surface membranes, is proposed to be essential to unveil the process of neuronal sensitization and related, abnormal pain signaling.

Are GPCRs Still a Source of New Targets?

G-protein–coupled receptors (GPCRs) still offer enormous scope for new therapeutic targets. Currently marketed agents are dominated by those with activity at aminergic receptors and yet they account for only ~10% of the family. Progress up until now with other subfamilies, notably orphans, Family A/peptide, Family A/lipid, Family B, Family C, and Family F, has been, at best, patchy. This may be attributable to the heterogeneous nature of GPCRs, their endogenous ligands, and consequently their binding sites. Our appreciation of receptor similarity has arguably been too simplistic, and screening collections have not necessarily been well suited to identifying leads in new areas. Despite the relative shortage of high-quality tool molecules in a number of cases, there is an emerging, and increasingly substantial, body of evidence associating many as yet “undrugged” receptors with a very wide range of diseases. Significant advances in our understanding of receptor pharmacology and technical advances in screening, protein X-ray crystallography, and ligand design methods are paving the way for new successes in the area. Exploitation of allosteric mechanisms; alternative signaling pathways such as G12/13, Gβγ, and β-arrestin; the discovery of “biased” ligands; and the emergence of GPCR-protein complexes as potential drug targets offer scope for new and much improved drugs.

Prophylactic Treatment of Migraine

Migraine is a common chronic neurological disease characterized by episodic attacks of headache and associated symptoms. The pharmacological treatment of migraine may be acute or prophylactic, and patients with frequent, severe headaches often require both approaches. Prophylactic treatment is used to reduce the frequency, duration, or severity of attacks, to enhance the benefits of acute treatments, and to improve patient's ability to function normally. Prophylactic treatment may also prevent progression from episodic migraine to chronic migraine and may result in reductions in health-care cost. The currently available pharmacological options for migraine prophylaxis include a wide array of medications. The major medication groups for prophylactic treatment include β-blockers, anticonvulsant, drugs such as topiramate and valproate, antidepressant drugs, such as amitriptyline and selective serotonin and selective serotonin-norepinephrine reuptake inhibitors (SNRIs), calcium channel antagonists and neurotoxins. The agent for prophylactic treatment should be chosen based on the efficacy and side-effect profile of the drug, and the patient's coexistent and comorbid conditions.