Antimigraine efficacy of telcagepant based on patient's historical triptan response

Efficacy of rimegepant for the acute treatment of migraine based on triptan treatment experience: Pooled results from three phase 3 randomized clinical trials

BACKGROUND

This post-hoc analysis from three phase 3 treatment trials of rimegepant 75 mg - an oral small molecule calcitonin gene-related peptide receptor antagonist for acute and preventive treatment of migraine - assessed efficacy in adults with migraine based on triptan treatment experience.

METHODS

Participants were assigned to one of four groups based on triptan treatment experience: insufficient response (e.g. lack of efficacy and/or poor tolerability) to 1 triptan, insufficient response to ≥2 triptans, current triptan users, and triptan-naïve participants. The co-primary efficacy endpoints were pain freedom and most bothersome symptom freedom at two hours postdose.

RESULTS

In the three trials (N = 3507; rimegepant n = 1749, placebo n = 1758), 1235 (35.2%) participants had a history of insufficient response to 1 triptan (n = 910 [25.9%]) or ≥2 triptans (n = 325 [9.3%]), and 2272 (64.8%) had no history of insufficient response to triptans (current use = 595 [17.0%], naïve = 1677 [47.8%]). Rimegepant was effective on the co-primary endpoints in all subgroups (p ≤ 0.013), except for freedom from the most bothersome symptom in the triptan-naïve group (p = 0.06). No differences on co-primary endpoints were found in pairwise comparisons of rimegepant-treated participants.

CONCLUSIONS

Rimegepant was effective for the acute treatment of migraine in adults with a history of insufficient response to 1 or ≥2 triptans and in current triptan users. Efficacy on co-primary endpoints did not differ based on the number of insufficient triptan responses.Trial registration: Clinicaltrials.gov: NCT03235479, NCT03237845, NCT03461757.

A systematic review with expert opinion on the role of gepants for the preventive and abortive treatment of migraine

INTRODUCTION

Gepants are small molecules targeting the calcitonin gene-related peptide (CGRP) that have been recently introduced and are under additional clinical development as preventive and abortive treatment options for migraine.

AREAS COVERED

After providing a narrative overview of current preventive and acute treatment options for migraine and summarizing the pathophysiology of migraine attack and the role of CGRP, we performed a systematic review, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations, on trials on gepants in preventive and acute treatment of migraine. Studies and results were reviewed and discussed, and expert opinion was presented. We also collected data on relevant ongoing trials.

EXPERT OPINION

Whether direct targeting CGRP pathways within the central nervous system or indirectly modulating them from the peripheral nervous system is more effective and safer in migraine remains still unclear. The available data on the efficacy and safety of gepants suggest they may represent an abortive, and to some extent, preventive treatment option for migraine, in patients who do not respond or have adverse effects to first/second line treatments or at high risk for medication overuse headache; thus opening new therapeutic horizons.

Efficacy of ubrogepant based on prior exposure and response to triptans: A post hoc analysis

Objective

To determine the potential efficacy of ubrogepant for acute treatment of migraine based on historical experience with triptans.

Background

Although triptans have improved migraine treatment, their efficacy and tolerability may limit their utility in some individuals. Ubrogepant is a small‐molecule, oral calcitonin gene–related peptide receptor antagonist approved by the Food and Drug Administration for acute treatment of migraine in adults.

Methods

This post hoc analysis of pooled data from the pivotal trials ACHIEVE I and II, identically designed, randomized, double‐blind, phase 3, single‐attack trials of ubrogepant in adults with a history of migraine with/without aura, examined the efficacy and tolerability of ubrogepant 50 mg versus placebo based on participants’ historical experience with triptans: triptan responder, triptan‐insufficient responder, and triptan naïve. Co‐primary efficacy endpoints were pain freedom and absence of most bothersome migraine‐associated symptom (MBS) 2 h post initial dose. Adverse events (AEs) within historical triptan experience subgroups were evaluated.

Results

In the pooled analysis population (n = 1799), 682 (placebo, n = 350; ubrogepant 50 mg, n = 332), 451 (placebo, n = 223; ubrogepant, n = 228), and 666 (placebo, n = 339; ubrogepant, n = 327) participants were triptan responders, triptan‐insufficient responders, and triptan‐naïve, respectively. Response rates on co‐primary efficacy endpoints were higher for ubrogepant versus placebo across all groups. Treatment‐by‐subgroup interaction p values based on odds ratios for pain freedom (p = 0.290) and absence of MBS (p = 0.705) indicated no significant impact of historical triptan experience on ubrogepant efficacy. AE incidence for ubrogepant did not differ appreciably across historical triptan experience subgroups.

Conclusions

Ubrogepant efficacy and tolerability did not differ for the acute treatment of migraine in participants classified as triptan responders, triptan‐insufficient responders, and triptan‐naïve based on their historical experience with triptans.

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.

Unmet Needs in Japanese Patients Who Report Insufficient Efficacy with Triptans for Acute Treatment of Migraine: Retrospective Analysis of Real-World Data

INTRODUCTION

Migraine attacks notably impact people's daily lives, health-related quality of life (HRQoL), and ability to work. Triptans are widely used as acute medication for a migraine attack but are ineffective, poorly tolerated, or contraindicated in some patients. HRQoL and work productivity are therefore likely to pose particular problems for patients whose migraine attacks do not respond sufficiently to triptan acute treatment. This real-world study aimed to determine whether migraine-related HRQoL, disability, and work productivity differed between triptan insufficient responders (TIRs) and sufficient responders (TSRs) receiving this acute treatment for migraine in Japan.

METHODS

This was a retrospective analysis of 2017 Adelphi Migraine Disease Specific Programme cross-sectional survey data collected from physicians and their consulting patients with migraine in Japan. Patients had to be receiving a triptan as their sole acute prescribed medication for migraine. TIRs were defined as patients who achieved headache pain freedom within 2 h of taking triptan acute treatment in no more than three of five migraine attacks. Differences in outcomes between TIRs and TSRs were examined in adjusted analyses using a multivariable general linear model.

RESULTS

Of 200 patients receiving a triptan as their sole prescribed acute treatment for migraine, 88 (44.0%) were classed as TIRs. Migraine-Specific Quality of Life Questionnaire scores were significantly lower-indicating poorer HRQoL-among TIRs than TSRs, as were mean EuroQol 5-dimension utility and visual analog scale scores (p < 0.05 for comparisons). TIRs also reported significantly (p ≤ 0.003) greater impairment than TSRs across all Work Productivity and Activity Impairment domains, with the exception of work time missed. Migraine disability was higher among TIRs than TSRs.

CONCLUSION

Migraine attacks had a negative impact on the HRQoL, disability, and work productivity of people with migraine in Japan reporting insufficient efficacy with acute triptan treatment, highlighting the need for more effective acute treatment options.

Evaluation of Patients with Insufficient Efficacy and/or Tolerability to Triptans for the Acute Treatment of Migraine: A Systematic Literature Review

INTRODUCTION

Use of triptans for acute treatment of migraine is associated with insufficient efficacy and/or tolerability in approximately 30-40% of people. We conducted a systematic literature review (SLR) to synthesize definitions, terminology, subsequent treatment outcomes, and characteristics associated with this subpopulation.

METHODS

A comprehensive SLR was conducted to identify studies, published from Jan 1995 to May 2019, which focused on insufficient efficacy and/or tolerability to triptans.

RESULTS

Thirty-five publications were identified, of which 22 described randomized controlled trials and open-label studies, and 13 described observational studies. Across studies, multiple objectives and a high amount of variability in methodologies and outcomes were noted. The most commonly applied measures of efficacy were headache pain freedom and pain relief at 2 h. Ten studies assessed efficacy of switching or optimizing treatment in patients with historical insufficient efficacy or tolerability to previous triptan treatment and demonstrated varying levels of success. Factors associated with increased risk of triptan insufficient efficacy included severe baseline headache severity, photophobia, phonophobia, nausea, and depression.

CONCLUSIONS

Irrespective of the methodology or definition used to identify people with insufficient efficacy and/or tolerability to triptans, study results support the assertion that a high unmet need remains for effective acute treatment of migraine.

Factors associated with insufficient response to acute treatment of migraine in Japan: analysis of real-world data from the Adelphi Migraine Disease Specific Programme

Background

Real-world data on sufficient/insufficient response, and predictors of insufficient response, to acute treatments for migraine are limited in Japan. This study aimed to identify factors associated with insufficient response to acute treatment of migraine by exploring significant differences between people with migraine who sufficiently/insufficiently respond to prescribed acute treatment in Japan.

Methods

This was a retrospective analysis of 2014 Adelphi Migraine Disease Specific Programme cross-sectional survey data collected from physicians and their consulting adult patients with migraine in Japan. Insufficient responders to prescribed acute treatment were patients who achieved headache pain freedom within 2 h of acute treatment in no more than three of their last five migraine attacks. Factors associated with insufficient response to prescribed acute migraine treatment were identified using backward logistic regression.

Results

Overall, 227/538 (42.2%) patients were classified as insufficient responders to prescribed acute migraine treatment. Significantly more insufficient responders than sufficient responders had consulted a neurologist or a migraine/headache specialist, and had chronic migraine or medication-overuse or tension-type headaches (p < 0.05). More insufficient responders than sufficient responders reported taking acute treatment when/after the pain started (77.0 vs. 68.9%) than at first sign of migraine (p < 0.05). Compared with sufficient responders, insufficient responders reported a significantly higher mean ± standard deviation (SD) Migraine Disability Assessment total score (12.7 ± 23.3 vs. 5.8 ± 10.4, p < 0.001) and lower quality of life (EuroQol-5 Dimensions utility score 0.847 ± 0.19 vs. 0.883 ± 0.16, p = 0.024). Factors significantly associated with insufficient response to acute treatment included seeing a neurologist versus an internist (odds ratio [OR] 1.93; 95% confidence interval [CI] 1.29–2.88; p = 0.002), taking acute medication when/after pain started versus at first sign of migraine (OR 1.65; 95% CI 1.05–2.60; p = 0.030), a higher MIDAS total score (OR 1.04; 95% CI 1.02–1.06; p < 0.001), and presence of comorbid cardiovascular disease (OR 0.53; 95% CI 0.28–0.98; p = 0.044).

Conclusions

Many people with migraine in Japan struggle to adequately treat migraine attacks with prescribed acute medication and exhibit high levels of unmet need for acute treatment. Optimized management strategies utilizing existing therapeutic options as well as additional effective therapeutic options for migraine are required to improve symptoms and quality of life.

Novel Medications for the Treatment of Migraine

OBJECTIVE

To describe the new classes of medication for headache management and their roles in clinical practice.

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a key component in the underlying pathophysiology of migraine. Research focused on targeting CGRP for headache treatment has led to the development of entirely new classes of medications - the gepants and the CGRP monoclonal antibodies (mAbs) - for both acute and preventive treatment. A third class, the ditans, is being developed to target the 5-HT1F receptor to provide acute treatment without vasoconstrictive effects.

METHODS

This article reviews the pathophysiology of migraine that has led to these new pharmacologic developments. Available information from randomized controlled trials, abstracts, press releases, and relevant preclinical studies is summarized for each class of medications.

RESULTS

At the time of this writing, one ditan has been submitted to the U.S. Food and Drug Administration (FDA) for approval. One gepant is anticipated to be submitted within the first quarter of 2019, and others are in clinical trials. Three CGRP mAbs have been FDA approved and are now available in clinical practice, and a fourth was submitted in the first quarter of 2019.

CONCLUSIONS

The development of new migraine-specific classes of medications provides more treatment options for both acute and preventive treatment of migraine.

The need for new acutely acting antimigraine drugs: moving safely outside acute medication overuse

Background

The treatment of migraine is impeded by several difficulties, among which insufficient headache relief, side effects, and risk for developing medication overuse headache (MOH). Thus, new acutely acting antimigraine drugs are currently being developed, among which the small molecule CGRP receptor antagonists, gepants, and the 5-HT_1F receptor agonist lasmiditan. Whether treatment with these drugs carries the same risk for developing MOH is currently unknown.

Main body

Pathophysiological studies on MOH in animal models have suggested that decreased 5-hydroxytryptamine (5-HT, serotonin) levels, increased calcitonin-gene related peptide (CGRP) expression and changes in 5-HT receptor expression (lower 5-HT_1B/D and higher 5-HT_2A expression) may be involved in MOH. The decreased 5-HT may increase cortical spreading depression frequency and induce central sensitization in the cerebral cortex and caudal nucleus of the trigeminal tract. Additionally, low concentrations of 5-HT, a feature often observed in MOH patients, could increase CGRP expression. This provides a possible link between the pathways of 5-HT and CGRP, targets of lasmiditan and gepants, respectively. Since lasmiditan is a 5-HT_1F receptor agonist and gepants are CGRP receptor antagonists, they could have different risks for developing MOH because of the different (over) compensation mechanisms following prolonged agonist versus antagonist treatment.

Conclusion

The acute treatment of migraine will certainly improve with the advent of two novel classes of drugs, i.e., the 5-HT_1F receptor agonists (lasmiditan) and the small molecule CGRP receptor antagonists (gepants). Data on the effects of 5-HT_1F receptor agonism in relation to MOH, as well as the effects of chronic CGRP receptor blockade, are awaited with interest.

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.

Migraine, Cyclic Vomiting Syndrome, and Other Gastrointestinal Disorders

PURPOSE OF REVIEW

Cyclic vomiting syndrome (CVS) is a chronic functional gastrointestinal disorder characterized by episodic nausea and vomiting and is diagnosed using Rome IV criteria. CVS is being recognized more frequently in adults with a prevalence of 2%. It is associated with several functional disorders like autonomic dysfunction, anxiety, and depression, but the strongest association is with migraine. We will elucidate the close relationship between migraine and CVS and briefly discuss its association with other gastrointestinal disorders.

RECENT FINDINGS

We highlight similarities in pathophysiology, clinical presentation, and response to medications between CVS and migraine (tricyclic antidepressants, triptans, antiepileptics). We also discuss novel therapies like CGRP inhibitors which are effective in migraine and have potential for adaptation in patients with CVS. Using migraine as a template should enable investigators to elucidate the mechanisms underlying this disorder, develop novel therapies, and direct future research in CVS.

Redox Mechanisms in Migraine: Novel Therapeutics and Dietary Interventions

SIGNIFICANCE

Migraine represents the third most prevalent and the seventh most disabling human disorder. Approximately 30% of migraine patients experience transient, fully reversible, focal neurological symptoms (aura) preceding the attack. Recent Advances: Awareness of the hypothesis that migraine actually embodies a spectrum of illnesses-ranging from episodic to chronic forms-is progressively increasing and poses novel challenges for clarifying the underlying pathophysiological mechanisms of migraine as well as for the development of novel therapeutic interventions. Several theories have evolved to the current concept that a combination of genetic, epigenetic, and environmental factors may play a role in migraine pathogenesis, although their relative importance is still being debated.

CRITICAL ISSUES

One critical issue that deserves a particular attention is the role of oxidative stress in migraine. Indeed, potentially harmful oxidative events occur during the migraine attack and long-lasting or frequent migraine episodes may increase brain exposure to oxidative events that can lead to chronic transformation. Moreover, a wide variety of dietary, environmental, physiological, behavioral, and pharmacological migraine triggers may act through oxidative stress, with clear implications for migraine treatment and prophylaxis. Interestingly, almost all current prophylactic migraine agents exert antioxidant effects.

FUTURE DIRECTIONS

Increasing awareness of the role of oxidative stress and/or decreased antioxidant defenses in migraine pathogenesis and progression to a chronic condition lays the foundations for the design of novel prophylactic approaches, which, by reducing brain oxidative phenomena, could favorably modify the clinical course of migraine. Antioxid. Redox Signal. 28, 1144-1183.

Targeted CGRP Small Molecule Antagonists for Acute Migraine Therapy

Migraine is a highly prevalent, severe, and disabling neurological condition with a significant unmet need for effective acute therapies. Patients (~50%) are dissatisfied with their currently available therapies. Calcitonin gene-related peptide (CGRP) has emerged as a key neuropeptide involved in the pathophysiology of migraines. As reviewed in this manuscript, a number of small molecule antagonists of the CGRP receptor have been developed for migraine therapy. Incredibly, the majority of the clinical trials conducted have proven positive, demonstrating the importance of this signalling pathway in migraine. Unfortunately, a number of these molecules raised liver toxicity concerns when used daily for as little as 7 days resulting in their discontinuation. Despite the clear safety concerns, clinical trial data suggests that their intermittent use remains a viable and safe alternative, with 2 molecules remaining in clinical development (ubrogepant and rimegepant). Further, these proofs of principle studies identifying CGRP as a viable clinical target have led to the development of several CGRP or CGRP receptor-targeted monoclonal antibodies that continue to show good clinical efficacy.

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.

Experimental inflammation following dural application of complete Freund's adjuvant or inflammatory soup does not alter brain and trigeminal microvascular passage

Background

Migraine is a paroxysmal, disabling primary headache that affects 16 % of the adult population. In spite of decades of intense research, the origin and the pathophysiology mechanisms involved are still not fully known. Although triptans and gepants provide effective relief from acute migraine for many patients, their site of action remains unidentified. It has been suggested that during migraine attacks the leakiness of the blood-brain barrier (BBB) is altered, increasing the passage of anti-migraine drugs. This study aimed to investigate the effect of experimental inflammation, following dural application of complete Freund’s adjuvant (CFA) or inflammatory soup (IS) on brain and trigeminal microvascular passage.

Methods

In order to address this issue, we induced local inflammation in male Sprague-Dawley-rats dura mater by the addition of CFA or IS directly on the dural surface. Following 2, 24 or 48 h of inflammation we calculated permeability-surface area product (PS) for [⁵¹Cr]-EDTA in the trigeminal ganglion (TG), spinal trigeminal nucleus, cortex, periaqueductal grey and cerebellum.

Results

We observed that [⁵¹Cr]-EDTA did not pass into the central nervous system (CNS) in a major way. However, [⁵¹Cr]-EDTA readily passed the TG by >30 times compared to the CNS. Application of CFA or IS did not show altered transfer constants.

Conclusions

With these experiments we show that dural IS/CFA triggered TG inflammation, did not increase the BBB passage, and that the TG is readily exposed to circulating molecules. The TG could provide a site of anti-migraine drug interaction with effect on the trigeminal system.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-015-0575-8) contains supplementary material, which is available to authorized users.

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).

New treatments for headache

Migraine and cluster headache are primary headache disorders commonly encountered in clinical practice. Despite the profound disability caused by these primary headache disorders, available acute and preventive treatment options are limited. Recent understanding of headache pathophysiology has led to the development of new drug formulations and novel drug targets that are extremely promising. This article will highlight several of the new treatments that are currently under investigation including novel delivery mechanisms of already existing medications, calcitonin gene-related peptide (CGRP) receptor antagonists, antibodies to CGRP and its receptor, serotonin receptor agonists, transient receptor potential vanilloid receptor modulators, orexin receptor antagonists, glial cell modulators, and neuromodulation. If data is supportive, these therapies will be welcome additions to the headache specialist's armamentarium.

CGRP infusion in unanesthetized rats increases expression of c-Fos in the nucleus tractus solitarius and caudal ventrolateral medulla, but not in the trigeminal nucleus caudalis

BACKGROUND AND AIMS

Calcitonin gene-related peptide (CGRP) and glyceryl trinitrate (GTN) infusion in migraineurs provokes headache resembling spontaneous migraine, and CGRP receptor antagonists are effective in the treatment of acute migraine. We hypothesized that CGRP infusion would increase molecular markers of neuronal activation in migraine-relevant tissues of the rat.

METHODS

CGRP was infused intravenously (i.v.) in freely moving rats to circumvent factors like anesthesia, acute surgery and severe hypotension, the three confounding factors for c-Fos expression. The trigeminal nucleus caudalis (TNC) was isolated at different time points after CGRP infusion. The level of c-Fos mRNA and protein expression in TNC were analyzed by qPCR and immunohistochemistry. c-Fos-stained nuclei were also counted in the nucleus tractus solitarius (NTS) and caudal ventrolateral medulla (CVLM), integrative sites in the brain stem for processing cardiovascular signals. We also investigated Zif268 protein expression (another immediate early gene) in TNC. The protein expression of p-ERK, p-CREB and c-Fos was analyzed in dura mater, trigeminal ganglion (TG) and TNC samples using Western blot.

RESULTS

CGRP infusion caused a significant dose-dependent fall in mean arterial blood pressure. No significant activation of c-Fos in the TNC at mRNA and protein levels was observed after CGRP infusion. A significant increase in c-Fos protein was observed in the NTS and CVLM in the brain stem. Zif268 expression in the TNC was also not changed after CGRP infusion. p-ERK was increased in the dura mater 30 minutes after CGRP infusion.

CONCLUSION

CGRP infusion increased the early expression of p-ERK in the dura mater but did not increase c-Fos and Zif268 expression in the TNC. The rats may, thus, differ from migraine patients, in whom infusion of CGRP caused headache and a delayed migraine attack. The rat CGRP infusion model with c-Fos or Zif268 as neuronal pain markers in TNC is unsuitable for antimigraine drug testing.

Calcitonin gene-related peptide and migraine with aura: A systematic review

Background

Calcitonin gene-related peptide (CGRP) is a key molecule in migraine pathophysiology. Most studies have focused on CGRP in relation to migraine without aura (MO). About one-third of migraine patients have attacks with aura (MA), and this is a systematic review of the current literature on CGRP and MA.

Methods

We performed a systematic literature search on MEDLINE for reports of CGRP and MA, covering basic science, animal and human studies as well as randomized clinical trials.

Results

The literature search identified 594 citations, of which 38 contained relevant, original data. Plasma levels of CGRP in MA patients are comparable to MO, but CGRP levels varied among studies. A number of animal studies, including knock-ins of familial hemiplegic migraine (FHM) genes, have examined the relationship between CGRP and cortical spreading depression. In patients, CGRP does not trigger migraine in FHM, but is a robust trigger of migraine-like headache both in MA and MO patients. The treatment effect of CGRP antagonists are well proven in the treatment of migraine, but no studies have studied the effect specifically in MA patients.

Conclusion

This systematic review indicates that the role of CGRP in MA is less studied than in MO. Further studies of the importance of CGRP for auras and migraine are needed.

The pipeline in headache therapy

Migraine is a common, disabling, neurovascular disorder characterized by episodic attacks of head pain and associated disability plus systemic autonomic and neurologic symptoms. The advent of the triptan class of medication in the 1990s revolutionized the acute treatment of migraine, but many migraineurs do not respond optimally or at all to triptans, have intolerable adverse effects, or have contraindications to their use. Preventive pharmacotherapy has advanced mostly through serendipity, with new drugs being found effective while being used for other indications. There remains a significant need for new medications and devices that can provide effective, rapid, and sustained pain relief without adverse effects or recurrence. Several new acute and preventive therapies for the treatment of migraine and cluster headaches have shown promise and are currently under investigation. This article covers innovative delivery mechanisms, calcitonin gene-related peptide receptor antagonists, antibodies to calcitonin gene-related peptide and its receptor, 5-HT1F receptor agonists, transient receptor potential vanilloid receptor modulators, orexin receptor antagonists, glial cell modulators, and neurostimulation.

What's new in the migraine attack treatment

This short review aims to give a focus on news in the migraine attack treatment and discusses the CGRP receptor antagonists (gepants), the 5-HT1F receptors agonists (ditans), the transcranial magnetic stimulation for the treatment of migraine attack with aura, innovative delivery systems for sumatriptan and the oral inhalation of dihydroergotamine.

NXN-188, a selective nNOS inhibitor and a 5-HT1B/1D receptor agonist, inhibits CGRP release in preclinical migraine models

BACKGROUND

NXN-188 is a combined neuronal nitric oxide synthase (nNOS) inhibitor and 5-hydroxytryptamine 1B/1D (5-HT1B/1D) receptor agonist. Using preclinical models, we evaluated whether these two unique therapeutic principles have a synergistic effect in attenuating stimulated calcitonin gene-related peptide (CGRP) release, a marker of trigeminal activation.

METHODS

We examined the effect of NXN-188 on: (1) KCl-, capsaicin- and resiniferatoxin (RTX)-induced immunoreactive CGRP (iCGRP) release from isolated preparation of rat dura mater, trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC); and (2) capsaicin- and electrical stimulation (ES)-induced middle meningeal artery (MMA) dilation in a rat closed-cranial window.

RESULTS

NXN-188 inhibited: (1) KCl-stimulated iCGRP release from dura mater (% decrease mean ± SEM, lowest effective concentration) (35 ± 6%, 30 µM), TG (24 ± 11%, 10 µM) and TNC (40 ± 8%, 10 µM); (2) capsaicin- and RTX-induced iCGRP release from dura mater; and (3) capsaicin- and ES-induced increase in dural artery diameter (32 ± 5%, 3 mg kg(-1) intravenous (i.v.) and 36 ± 1%, 10 mg kg(-1) i.v.).

CONCLUSIONS

NXN-188 inhibits CGRP release from migraine-relevant cephalic tissues. Its effect is most likely mediated via a combination of nNOS-inhibition and 5-HT1B/1D receptor agonism in dura mater while the mechanisms of action for inhibition of CGRP release from TG and TNC have to be investigated further.

New Agents for Acute Treatment of Migraine: CGRP Receptor Antagonists, iNOS Inhibitors

OPINION STATEMENT

The treatment of migraine was advanced dramatically with the introduction of triptans in the early 1990s. Despite the substantial improvement in the quality of life that triptans have brought to many migraineurs, a substantial cohort of patients remain highly disabled by attacks and need new therapeutic approaches, which ideally should be quick-acting, have no vasoconstrictor activity, and have a longer duration of action and be better tolerated than current therapies. The calcitonin gene-related peptide (CGRP) receptor antagonists (gepants)-olcegepant (BIBN 4096 BS), telcagepant (MK-0974), MK3207, and BI 44370 TA-are effective in treating acute migraine. They have no vasoconstrictive properties, fewer adverse effects, and may act longer than triptans. Their development has been complicated by liver toxicity issues when used as preventives. Results from studies with BI 44370 TA do not support broad concern about a class effect, and further studies are ongoing in this respect. Many experimental studies and clinical trials suggest that nitric oxide may have a role in the pathophysiology of migraine. Therefore, the inhibition of nitric oxide synthase (NOS) for the acute or prophylactic treatment of migraine offered a feasible approach; as inducible NOS (iNOS) is involved in several pain states, such as inflammatory pain, it appeared to be an attractive target. However, despite high selectivity and potency, the iNOS inhibitor GW274150 was not effective for acute treatment or prophylaxis of migraine, suggesting that iNOS is very unlikely to be a promising target.

Management of acute and chronic migraine

PURPOSE OF REVIEW

We highlight the recent clinical trials for the management of acute and chronic migraine.

RECENT FINDINGS

In women with menstrual migraine, triptans seem to be well tolerated irrespective of whether or not patients are taking oestrogen-containing contraceptives or have comorbidities that indicate increased cardiovascular risk. The new acute drug, telcagepant, a calcitonin gene-related peptide (CGRP) antagonist, is safe for long-term use (up to 18 months) in migraine patients with stable coronary artery disease in whom the use of triptans is not advisable. From the pooled analysis of the two Phase III Research Evaluating Migraine Prophylaxis Therapy studies of onabotulinumtoxinA (BOTOX) in chronic migraineurs, it clearly emerged that efficacy increases overtime (up to 56 weeks) and paralleled self-perceived improvement in quality of life. Effectiveness was also observed in patients with severely disabling headaches, who met criteria for triptan abuse and were refractory to several prophylactic treatments. Finally, combination of preventive pharmacological agents with different action mechanisms may be the next frontier in therapeutic advancements for treating migraine.

SUMMARY

Although triptans are safe and well tolerated, CGRP antagonists may be an option for nonresponsive patients or those in whom the use of triptans is not advisable. New drugs and combinations of old therapeutic options may help patients with severe forms of headache.

ACS chemical neuroscience molecule spotlight on Telcagepant (MK-0974)

Telcagepant (MK-0974) is a novel calcitonin gene-related peptide (CGRP) receptor antagonist currently undergoing clinical trials for migraine (http://www.merck.com/research/pipeline/home.html). MK-0974 is currently being studied in phase III clinical trials.

Telcagepant: A New Therapeutic Option for Acute Migraine?

Telcagepant (MK0974) is one of several calcitonin-gene-related peptide antagonists in development as a potential treatment for acute migraine attacks and is the first orally available drug in this class. Preclinical and clinical data are reviewed, which support the efficacy and tolerability of telcagepant for the treatment of migraine, particularly for patients unable to tolerate, or who have cardiovascular contraindications to, triptans.