Randomized controlled trial of an oral CGRP receptor antagonist, MK-0974, in acute treatment of migraine

Migraine and neuropeptides

Migraine is a common disabling neurovascular primary headache disorder. The pathomechanism is not clear, but extensive preclinical and clinical studies are ongoing. The structural basis of the leading hypothesis is the trigeminovascular system, which includes the trigeminal ganglion, the meningeal vasculature, and the distinct nuclei of the brainstem, the thalamus and the somatosensory cortex. This review covers the effects of sensory (calcitonin gene-related peptide, pituitary adenylate cyclase-activating polypeptide and substance P), sympathetic (neuropeptide Y) and parasympathetic (vasoactive intestinal peptide) migraine-related neuropeptides and the functions of somatostatin, nociceptin and the orexins in the trigeminovascular system. These neuropeptides may take part in neurogenic inflammation (plasma protein extravasation and vasodilatation) of the intracranial vasculature and peripheral and central sensitization of the trigeminal system. The results of human clinical studies are discussed with regard to the alterations in these neuropeptides in the plasma, saliva and cerebrospinal fluid during or between migraine attacks, and the therapeutic possibilities involving migraine-related neuropeptides in the acute and prophylactic treatment of migraine headache are surveyed.

Novel oxazolidinone calcitonin gene-related peptide (CGRP) receptor antagonists for the acute treatment of migraine

In our efforts to develop CGRP receptor antagonists as backups to MK-3207, 2, we employed a scaffold hopping approach to identify a series of novel oxazolidinone-based compounds. The development of a structurally diverse, potent (20, cAMP+HS IC50=0.67 nM), and selective compound (hERG IC50=19 μM) with favorable rodent pharmacokinetics (F=100%, t1/2=7h) is described. Key to this development was identification of a 3-substituted spirotetrahydropyran ring that afforded a substantial gain in potency (10 to 35-fold).

Hydrogen sulfide determines HNO-induced stimulation of trigeminal afferents

Endogenous NO and hydrogen sulfide form HNO, which causes CGRP release via TRPA1 channel activation in sensory nerves. In the present study, stimulation of intact trigeminal afferent neuron preparations with NO donors, Na2S or both was analyzed by measuring CGRP release as an index of mass activation. Combined stimulation was able to activate all parts of the trigeminal system and acted synergistic compared to stimulation with both substances alone. To investigate the contribution of both substances, we varied their ratio and tracked intracellular calcium in isolated neurons. Our results demonstrate that hydrogen sulfide is the rate-limiting factor for HNO formation. CGRP has a key role in migraine pathophysiology and HNO formation at all sites of the trigeminal system should be considered for this novel means of activation.

Review of dose-response curves for acute antimigraine drugs: triptans, 5-HT1F agonists and CGRP antagonists

INTRODUCTION

Dose-response curves for efficacy and tolerability are the important determinants for the choice of doses of acute migraine drugs.

AREAS COVERED

Dose-response curves for the efficacy of seven triptans (5-HT1B/1D receptor agonists), a 5-HT1F receptor agonist (lasmiditan) and four oral calcitonin-gene related peptide receptor antagonists (telcagepant, MK-3207, BI 44370 TA and BMS-927711) in placebo-controlled trials were reviewed. In addition, dose-response curves for adverse events (AEs) were reviewed.

EXPERT OPINION

For most triptans, the dose-response curve for efficacy is flat, whereas AEs often increase with increasing doses. The two other groups of drugs also have flat dose-response curves for efficacy. Overall, the triptans still have the most favorable efficacy-tolerability profile. Current acute antimigraine drugs do not fulfill the expectations of the patients, and thus, there are many unmet needs. Although upcoming drugs may not be superior to triptans, migraine patients will potentially benefit greatly from these, especially patients who are triptan non-responders and patients with cardiovascular disease.

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).

A potent and selective calcitonin gene-related peptide (CGRP) receptor antagonist, MK-8825, inhibits responses to nociceptive trigeminal activation: Role of CGRP in orofacial pain

Temporomandibular disorders (TMDs) are orofacial pains within the trigeminal distribution, which involve the masticatory musculature, the temporomandibular joint or both. Their pathophysiology remains unclear, as inflammatory mediators are thought to be involved, and clinically TMD presents pain and sometimes limitation of function, but often appears without gross indications of local inflammation, such as visible edema, redness and increase in temperature. Calcitonin gene-related peptide (CGRP) has been implicated in other pain disorders with trigeminal distribution, such as migraine, of which TMD shares a significant co-morbidity. CGRP causes activation and sensitization of trigeminal primary afferent neurons, independent of any inflammatory mechanisms, and thus may also be involved in TMD. Here we used a small molecule, selective CGRP receptor antagonist, MK-8825, to dissect the role of CGRP in inducing spontaneous nociceptive facial grooming behaviors, neuronal activation in the trigeminal nucleus, and systemic release of pro-inflammatory cytokines, in a mouse model of acute orofacial masseteric muscle pain that we have developed, as a surrogate of acute TMD. We show that CFA masseteric injection causes significant spontaneous orofacial pain behaviors, neuronal activation in the trigeminal nucleus, and release of interleukin-6 (IL-6). In mice pre-treated with MK-8825 there is a significant reduction in these spontaneous orofacial pain behaviors. Also, at 2 and 24h after CFA injection the level of Fos immunoreactivity in the trigeminal nucleus, used as a marker of neuronal activation, was much lower on both ipsilateral and contralateral sides after pre-treatment with MK-8825. There was no effect of MK-8825 on the release of IL-6. These data suggest that CGRP may be involved in TMD pathophysiology, but not via inflammatory mechanisms, at least in the acute stage. Furthermore, CGRP receptor antagonists may have therapeutic efficacy in the treatment of TMD, as they do with migraine.

Randomized controlled trial of the CGRP receptor antagonist telcagepant for prevention of headache in women with perimenstrual migraine

Aim

The aim of this article is to evaluate the safety and efficacy of perimenstrual telcagepant, a CGRP receptor antagonist, for headache prophylaxis.

Methods

We conducted a randomized, double-blind, placebo-controlled, six-month trial in women with migraine for ≥3 months who experienced perimenstrual headaches. Women were randomized to telcagepant 140 mg or placebo (2:1 ratio) for seven consecutive days perimenstrually. Safety was assessed by adverse events and laboratory tests. The primary efficacy endpoint was mean monthly headache days in the subset of women reporting perimenstrual migraine (−2 days to +3 days of menses onset) and ≥5 moderate or severe migraines per month prior to entering the trial.

Results

Telcagepant was generally well tolerated: 66/2660 (2.5%) on telcagepant and 36/1326 (2.7%) on placebo discontinued because of a clinical adverse event. The percentages of patients with clinical adverse events, laboratory adverse events, or discontinuation because of a laboratory adverse event were also similar between treatments. Alanine aminotransferase elevations ≥3× normal occurred in 0.6% of women on telcagepant and 0.4% on placebo. Three women on telcagepant vs none on placebo had alanine aminotransferase elevations ≥8× normal. In the efficacy subset there was no significant effect of telcagepant ( n = 887) vs placebo ( n = 447) in mean monthly headache days (treatment difference −0.5 day (95% CI: −1.1, 0.1)). However, telcagepant was associated with a reduction in on-drug headache days (treatment difference −0.4 day (95% CI: –0.5, –0.2), nominal p < 0.001).

Conclusions

Telcagepant 140 mg taken perimenstrually for seven days was generally well tolerated, but was associated with transaminase elevations . Telcagepant did not reduce monthly headache frequency, but did reduce perimenstrual headaches.

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.

Efficient direct 2,2,2-trifluoroethylation of indoles via C–H functionalization

Metal free direct trifluoroethylation of unprotected indoles at position 3 via C–H functionalization is presented: straightforward synthesis and DFT studies.

Targeting TRP channels for novel migraine therapeutics

Migraine is increasingly understood to be a disorder of the brain. In susceptible individuals, a variety of “triggers” may influence altered central excitability, resulting in the activation and sensitization of trigeminal nociceptive afferents surrounding blood vessels (i.e., the trigeminovascular system), leading to migraine pain. Transient receptor potential (TRP) channels are expressed in a subset of dural afferents, including those containing calcitonin gene related peptide (CGRP). Activation of TRP channels promotes excitation of nociceptive afferent fibers and potentially lead to pain. In addition to pain, allodynia to mechanical and cold stimuli can result from sensitization of both peripheral afferents and of central pain pathways. TRP channels respond to a variety of endogenous conditions including chemical mediators and low pH. These channels can be activated by exogenous stimuli including a wide range of chemical and environmental irritants, some of which have been demonstrated to trigger migraine in humans. Activation of TRP channels can elicit CGRP release, and blocking the effects of CGRP through receptor antagonism or antibody strategies has been demonstrated to be effective in the treatment of migraine. Identification of approaches that can prevent activation of TRP channels provides an additional novel strategy for discovery of migraine therapeutics.

A randomized, double-blind, placebo-controlled study of breath powered nasal delivery of sumatriptan powder (AVP-825) in the treatment of acute migraine (The TARGET Study)

Objective

To evaluate the efficacy and safety of AVP-825, a drug–device combination of low-dose sumatriptan powder (22 mg loaded dose) delivered intranasally through a targeted Breath Powered device vs an identical device containing lactose powder (placebo device) in the treatment of migraine headache.

Background

Early treatment of migraine headaches is associated with improved outcome, but medication absorption after oral delivery may be delayed in migraineurs because of reduced gastric motility. Sumatriptan powder administered with an innovative, closed-palate, Bi-Directional, Breath Powered intranasal delivery mechanism is efficiently absorbed across the nasal mucosa and produces fast absorption into the circulation. Results from a previously conducted placebo-controlled study of AVP-825 showed a high degree of headache relief with an early onset of action (eg, 74% AVP-825 vs 38% placebo device at 1 hour, P < .01).

Methods

In this double-blind, placebo-controlled, parallel-group study in adults with a history of migraine with or without aura, participants were randomized via computer-generated lists to AVP-825 or placebo device to treat a single migraine headache of moderate or severe intensity. The primary endpoint was headache relief (defined as reduction of headache pain intensity from severe or moderate migraine headache to mild or none) at 2 hours post-dose.

Results

Two hundred and thirty patients (116 AVP-825 and 114 placebo device) were randomized, of whom 223 (112 and 111, respectively) experienced a qualifying migraine headache (their next migraine headache that reached moderate or severe intensity). A significantly greater proportion of AVP-825 patients reported headache relief at 2 hours post-dose compared with those using the placebo device (68% vs 45%, P = .002, odds ratio 2.53, 95% confidence interval [1.45, 4.42]). Between-group differences in headache relief were evident as early as 15 minutes, reached statistical significance at 30 minutes post-dose (42% vs 27%, P = .03), and were sustained at 24 hours (44% vs 24%, P = .002) and 48 hours (34% vs 20%, P = .01). Thirty-four percent of patients treated with AVP-825 were pain-free at 2 hours compared with 17% using the placebo device (P = .008). More AVP-825 patients reported meaningful pain relief (patient interpretation) of migraine within 2 hours of treatment vs placebo device (70% vs 45%, P < .001), and fewer required rescue medication (37% vs 52%, P = .02). Total migraine freedom (patients with no headache, nausea, phonophobia, photophobia, or vomiting) reached significance following treatment with AVP-825 at 1 hour (19% vs 9%; P = .04). There were no serious adverse events (AEs), and no systemic AEs occurred in more than one patient. Chest pain or pressure was not reported, and only one patient taking AVP-825 reported mild paresthesia. No other triptan sensations were reported.

Conclusions

Targeted delivery of a low-dose of sumatriptan powder via a novel, closed-palate, Breath Powered, intranasal device (AVP-825) provided fast relief of moderate or severe migraine headache in adults that reached statistical significance over placebo by 30 minutes. The treatment was well tolerated with a low incidence of systemic AEs.

Calcitonin gene-related peptide (CGRP): a new target for migraine

Migraine is a neurological disorder that manifests as a debilitating headache associated with altered sensory perception. The neuropeptide calcitonin gene-related peptide (CGRP) is now firmly established as a key player in migraine. Clinical trials carried out during the past decade have proved that CGRP receptor antagonists are effective for treating migraine, and antibodies to the receptor and CGRP are currently under investigation. Despite this progress in the clinical arena, the mechanisms by which CGRP triggers migraine remain uncertain. This review discusses mechanisms whereby CGRP enhances sensitivity to sensory input at multiple levels in both the periphery and central nervous system. Future studies on epistatic and epigenetic regulators of CGRP actions are expected to shed further light on CGRP actions in migraine. In conclusion, targeting CGRP represents an approachable therapeutic strategy for migraine.

Pregabalin alleviates the nitroglycerin-induced hyperalgesia in rats

The association between the clinical use of nitroglycerin (NTG) and migraine suggests NTG as an animal model trigger for migraine. NTG-induced hyperalgesia in rats has been extensively used as a migraine model for pre-clinical research. Pregabalin is an anti-epileptic drug and may play a role in the preventive treatment of migraine; however, the mechanism of this action remains to be clarified. Herein, we performed the present study to investigate the effect of pregabalin on the NTG-induced hyperalgesia in rats. Sixty male Sprague-Dawley rats were divided equally into six groups. Thirty minutes before NTG injection, the rats were pretreated with pregabalin. von Frey hair testing was employed to evaluate tactile sensitivity. Enzyme-linked immunosorbent assay was used to analyze plasma calcitonin gene-related peptide (CGRP) levels in the jugular vein. Immunohistochemistry was applied to detect c-Fos-immunoreactive neurons and western blot was performed to detect c-Fos protein expression in trigeminal nucleus caudalis (TNC). We found that pregabalin pretreatment alleviated the NTG-induced hyperalgesia. Moreover, pregabalin suppressed peripheral CGRP release, c-Fos-immunoreactive neurons and the protein expression of c-Fos in TNC as well. These data suggest that pregabalin could alleviate the NTG-induced hyperalgesia. Further studies are required to determine the mechanisms of action for this effect.

Therapeutic effects and safety of olcegepant and telcagepant for migraine: A meta-analysis

OBJECTIVE:

To evaluate the therapeutic effects and adverse reactions of olcegepant and telcagepant for the treatment of migraine.

DATA RETRIEVAL:

We identified studies using Medline (1966-01/2012-06), PubMed (1966-01/2012-06), Scopus (1980-01/2012-06), Cochrane Central Register of Controlled Trials (1980-01/2012-06) and China National Knowledge Infrastructure (1980-01/2012-06).

SELECTION CRITERIA:

The included studies were double-blind, randomized and placebo-controlled trials of olcegepant or telcagepant for the treatment of single acute migraine in patients with or without aura. Adverse reaction data were also included. Two independent investigators performed quality evaluation and data extraction using Jadad scoring. Meta-analyses were undertaken using RevMan 5.0.25 software.

MAIN OUTCOME MEASURES:

Pain relief rate, pain-free rate, and incidence of adverse reactions were measured in patients 2 and 24 hours after injection of olcegepant and oral telcagepant.

RESULTS:

Six randomized, controlled trials were included. Meta-analysis demonstrated that compared with placebo, the pain relief rate (odds ratio, OR = 5.21, 95% confidence interval, CI: 1.91–14.2, P < 0.01) and pain-free rate (OR = 31.11, 95% CI: 3.80–254.98, P < 0.01) significantly increased 2 hours after 2.5 mg/d olcegepant treatment. Pain relief rate and pain-free rate 2 and 24 hours after treatment with telcagepant 150 mg/d and 300 mg/d were superior to placebo (P < 0.01). Moreover, the remission rate of unrelenting headache was higher after 24 hours of 300 mg/d telcagepant treatment compared with 150 mg/d (OR = 0.78, 95% CI: 0.62–0.97, P < 0.05). The incidence of adverse reactions with olcegepant was not significantly greater than placebo (P = 0.28), but within 48 hours of administration of telcagepant 300 mg/d, the incidence of adverse reactions was higher than placebo (OR = 1.21, 95% CI: 1.04–1.42, P < 0.01). Few studies have compared the therapeutic effects of olcegepant and telcagepant.

CONCLUSION:

The calcitonin-gene-related peptide receptor antagonists olcegepant and telcagepant have shown good therapeutic effects in the treatment of migraine. Moreover, the incidence of adverse reactions compares favorably with placebo, although liver transaminases may become elevated after long-term use.

Pathophysiology of autism spectrum disorders: Revisiting gastrointestinal involvement and immune imbalance

Autism spectrum disorders (ASD) comprise a group of neurodevelopmental abnormalities that begin in early childhood and are characterized by impairment of social communication and behavioral problems including restricted interests and repetitive behaviors. Several genes have been implicated in the pathogenesis of ASD, most of them are involved in neuronal synaptogenesis. A number of environmental factors and associated conditions such as gastrointestinal (GI) abnormalities and immune imbalance have been linked to the pathophysiology of ASD. According to the March 2012 report released by United States Centers for Disease Control and Prevention, the prevalence of ASD has sharply increased during the recent years and one out of 88 children suffers now from ASD symptoms. Although there is a strong genetic base for the disease, several associated factors could have a direct link to the pathogenesis of ASD or act as modifiers of the genes thus aggravating the initial problem. Many children suffering from ASD have GI problems such as abdominal pain, chronic diarrhea, constipation, vomiting, gastroesophageal reflux, and intestinal infections. A number of studies focusing on the intestinal mucosa, its permeability, abnormal gut development, leaky gut, and other GI problem raised many questions but studies were somehow inconclusive and an expert panel of American Academy of Pediatrics has strongly recommended further investigation in these areas. GI tract has a direct connection with the immune system and an imbalanced immune response is usually seen in ASD children. Maternal infection or autoimmune diseases have been suspected. Activation of the immune system during early development may have deleterious effect on various organs including the nervous system. In this review we revisited briefly the GI and immune system abnormalities and neuropeptide imbalance and their role in the pathophysiology of ASD and discussed some future research directions.

Intraganglionic signaling as a novel nasal-meningeal pathway for TRPA1-dependent trigeminovascular activation by inhaled environmental irritants

Headache is the most common symptom associated with air pollution, but little is understood about the underlying mechanism. Nasal administration of environmental irritants activates the trigeminovascular system by a TRPA1-dependent process. This report addresses questions about the anatomical pathway involved and the function of TRP channels in this pathway. TRPV1 and TRPA1 are frequently co-localized and interact to modulate function in sensory neurons. We demonstrate here that resiniferatoxin ablation of TRPV1 expressing neurons significantly reduces meningeal blood flow responses to nasal administration of both TRPV1 and TRPA1 agonists. Accordingly resiniferatoxin also significantly reduces TRPV1 and CGRP immunostaining and TRPV1 and TRPA1 message levels in trigeminal ganglia. Sensory neurons of the trigeminal ganglia innervate the nasal epithelium and the meninges, but the mechanism and anatomical route by which nasal administration evokes meningeal vasodilatation is unclear. Double retrograde labeling from the nose and meninges reveals no co-localization of fluorescent label, however nasal and meningeal labeled cells are located in close proximity to each other within the trigeminal ganglion. Our data demonstrate that TRPV1 expressing neurons are important for TRPA1 responses in the nasal-meningeal pathway. Our data also suggest that the nasal-meningeal pathway is not primarily by axon reflex, but may instead result from intraganglionic transmission.

Correlation between algogenic effects of calcitonin-gene-related peptide (CGRP) and activation of trigeminal vascular system, in an in vivo experimental model of nitroglycerin-induced sensitization

The neural mechanism(s) underlying migraine remain poorly defined at present; preclinical and clinical studies show an involvement of CGRP in this disorder. However current evidence pointed out that CGRP does not exert an algogenic action per se, but it is able to mediate migraine pain only if the trigeminal-vascular system is sensitized. The present study was addressed to investigate CGRP-evoked behavior in nitric oxide (NO) sensitized rats, using an experimental model of nitroglycerin induced sensitization of trigeminal system, looking at neuropeptide release from different cerebral areas after the intra-peritoneal (i.p.) administration of NO-donors. CGRP injected into the rat whisker pad did not induce significant changes in face rubbing behavior compared to controls. On the contrary, CGRP injected in animals pre-treated with 10mg/kg nitroglycerin significantly increased the time spent in face rubbing. Nitroglycerin pre-treated animals did not show any rubbing behavior after locally injected saline. Furthermore, the i.p. treatment with nitroglycerin produced an increase of CGRP levels in brainstem and trigeminal ganglia, but not in the hypothalamus and hippocampus. The absolute amounts of CGRP produced in the brainstem were lower compared to those in the trigeminal ganglion; however, after nitroglycerin stimulation the percentage increase was higher in the brainstem. In conclusion, findings presented in this study suggest that CGRP induces a painful behavior in rats only after sensitization of trigeminal system; thus supporting the concept that a genetic as well as acquired predisposition to trigemino- vascular activation represents the neurobiological basis of CGRP nociceptive effects in migraineurs.

Calcitonin gene-related peptide receptor antagonists: beyond migraine pain--a possible analgesic strategy for osteoarthritis?

Osteoarthritis (OA) pain is poorly understood and managed, as current analgesics have only limited efficacy and unwanted side effect profiles. A broader understanding of the pathological mechanisms driving OA joint pain is vital for the development of improved analgesics. Both clinical and preclinical data suggest an association between joint levels of the sensory neuropeptide calcitonin gene-related peptide (CGRP) and pain during OA. Whether a direct causative link exists remains an important unanswered question. Given the recent development of small molecule CGRP receptor antagonists with clinical efficacy against migraine pain, the interrogation of the role of CGRP in OA pain mechanisms is extremely timely. In this article, we provide the background to the importance of CGRP in pain mechanisms and review the emerging clinical and preclinical evidence implicating a role for CGRP in OA pain. We suggest that the CGRP receptor antagonists developed for migraine pain warrant further investigation in OA.

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.

The TRPA1 channel in migraine mechanism and treatment

Migraine remains an elusive and poorly understood disease. The uncertainty is reflected by the currently unsatisfactory acute and prophylactic treatments for this disease. Genetic and pharmacological information points to the involvement of some transient receptor potential (TRP) channels in pain mechanisms. In particular, the TRP vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1) channels seem to play a major role in different models of pain diseases. Recent findings have underscored the possibility that TRP channels expressed in the nerve terminals of peptidergic nociceptors contribute to the migraine mechanism. Among this channel subset, TRPA1, a sensor of oxidative, nitrative and electrophilic stress, is activated by an unprecedented series of irritant and pain-provoking exogenous and endogenous agents, which release the pro-migraine peptide, calcitonin gene-related peptide, through this neuronal pathway. Some of the recently identified TRPA1 activators have long been known as migraine triggers. Furthermore, specific analgesic and antimigraine medicines have been shown to inhibit or desensitize TRPA1 channels. Thus, TRPA1 is emerging as a major contributing pathway in migraine and as a novel target for the development of drugs for pain and migraine treatment.

Development of a novel antibody to calcitonin gene-related peptide for the treatment of osteoarthritis-related pain

OBJECTIVE

Investigate a role for calcitonin gene-related peptide (CGRP) in osteoarthritis (OA)-related pain.

DESIGN

Neutralizing antibodies to CGRP were generated de novo. One of these antibodies, LY2951742, was characterized in vitro and tested in pre-clinical in vivo models of OA pain.

RESULTS

LY2951742 exhibited high affinity to both human and rat CGRP (KD of 31 and 246 pM, respectively). The antibody neutralized CGRP-mediated induction of cAMP in SK-N-MC cells in vitro and capsaicin-induced dermal blood flow in the rat. Neutralization of CGRP significantly reduced pain behavior as measured by weight bearing differential in the rat monoiodoacetate model of OA pain in a dose-dependent manner. Moreover, pain reduction with neutralization of CGRP occurred independently of prostaglandins, since LY2951742 and NSAIDs worked additively in the NSAID-responsive version of the model and CGRP neutralization remained effective in the NSAID non-responsive version of the model. Neutralization of CGRP also provided dose-dependent and prolonged (>60 days) pain reduction in the rat meniscal tear model of OA after only a single injection of LY2951742.

CONCLUSIONS

LY2951742 is a high affinity, neutralizing antibody to CGRP. Neutralization of CGRP is efficacious in several OA pain models and works independently of NSAID mechanisms of action. LY2951742 holds promise for the treatment of pain in OA patients.

PACAP-38 but not VIP induces release of CGRP from trigeminal nucleus caudalis via a receptor distinct from the PAC1 receptor

OBJECTIVE

To investigate if PACAP and VIP have an effect on CGRP release or NOS activity in the trigeminal ganglion and trigeminal nucleus caudalis and if there can be a difference in effect between PACAP and VIP on these two systems. Furthermore, we investigate if PACAP co-localize with CGRP and/or nNOS in the two tissues.

BACKGROUND

The structurally related neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide-38 (PACAP-38) partially share receptors and are both potent vasodilators. However, PACAP-38 but not VIP is an efficient inducer of migraine attacks in migraineurs. Calcitonin gene-related peptide (CGRP) and nitric oxide (NO) are two signaling molecules known to be involved in migraine.

METHODS

Rat tissue was used for all experiments. Release of CGRP induced by VIP and PACAP in dura mater, trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC) was quantified by EIA. Regulation of NOS-enzymes caused by VIP and PACAP was investigated in dura mater, TG and TNC by measuring the conversion of L-[3H]arginine to L-[3H]citrulline. Co-expression of PACAP, neuronal nitric oxide synthase (nNOS) and CGRP was explored by immunohistochemistry in TG and TNC. mRNA expression studies of VPAC1, VPAC2 and PAC1-receptors were performed by qRT-PCR.

RESULTS

PACAP-38 administered in increasing concentrations caused a concentration-dependent CGRP-release in the TNC, but not in TG. VIP was without effect in both tissues examined. The PAC1 receptor agonist maxadilan had no effect on CGRP release and the PAC1 antagonist M65 did not inhibit PACAP-38 induced CGRP release. PACAP-38 or VIP did not affect NOS activity in homogenates of TG and TNC. Quantitative PCR demonstrated the presence of VPAC1, VPAC2 and PAC1 receptors in TG and TNC. Immunohistochemistry of PACAP and CGRP showed co-expression in TG and TNC. PACAP and nNOS were co-localized in TG, but not in TNC. PACAP was found to co-localize with glutamine synthetase in TG satellite glial cells.

CONCLUSION

PACAP-38 cause release of CGRP from TNC but not from TG. We suggest that the release is not caused via activation of PAC1, VPAC1 or VPAC2 receptors. PACAP has no effect on NOS activity in TG or TNC. In TG PACAP was found in neuronal cells and in satellite glial cells. It co-localized with CGRP and nNOS in the neuronal cells. In TNC PACAP was co-localized with CGRP but not with nNOS.

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.

Update on future headache treatments

Headache disorders are common and heterogenous neurologic entities. The complexities of management are further encumbered by the relatively few effective choices for acute and preventive therapies available to the headache specialist to treat these diverse disorders. As advances have been made in uncovering headache pathophysiology, new therapies have surfaced and others are forthcoming. This article will highlight new lines of care in development. There are several novel delivery mechanisms of familiar medications which bypass the limitations of current delivery systems, including the sumatriptan iontophoretic patch Zecuity, the intranasal sumatriptan OptiNose system, the zolmitriptan Rapidfilm orally dissolvable film and the orally inhaled dihydroergotamine Levadex system. New lines of care based upon recently discovered therapeutic targets will also be discussed including calcitonin gene-related peptide (CGRP) receptor antagonists, serotonin receptor agonists, and sphenopalatine ganglion (SPG) intermittent stimulation. Finally, emerging targets for future therapeutics will be explored including transient receptor potential vanilloid (TRPV1) receptor modulators, nitric oxide (NO) antagonists, gap junction modulators, glutamate receptor antagonists, orexin receptor antagonists and prostanoid receptor antagonists. Therapies developing over the next several years will be welcome additions to the headache specialist's armamentarium.

Pearls and pitfalls in experimental in vivo models of migraine: dural trigeminovascular nociception

BACKGROUND

Migraine is a disorder of the brain and is thought to involve activation of the trigeminovascular system, which includes the peripheral afferent projection to the nociceptive specific dura mater, as well as the central afferent projection to the trigeminal nucleus caudalis. Stimulation of the blood vessels of the dura mater produces pain in patients that is referred to the head similar to headache. HEADACHE MECHANISMS: The likely reason for the pain is because the vascular structures of the dura mater, including the superior sagittal sinus and middle meningeal artery, are richly innervated by a plexus of largely unmyelinated sensory nerve fibers from the ophthalmic division of the trigeminal ganglion.

METHODOLOGY

Stimulation of these nociceptive specific nerve fibers is painful and produces neuronal activation in the trigeminal nucleus caudalis. Preclinical models of headache have taken advantage of this primarily nociceptive pathway, and various animal models use dural trigeminovascular nociception to assay aspects of head pain. These assays measure responses at the level of the dural vasculature and the central trigeminal nucleus caudalis as a correlate of trigeminovascular activation thought to be involved in headache.

SUMMARY

This review will summarize the history of the development of models of dural trigeminovascular nociception, including intravital microscopy and laser Doppler flowmetry at the level of the vasculature, and electrophysiology and Fos techniques used to observe neuronal activation at the trigeminal nucleus caudalis. It will also describe some of pitfalls of these assays and developments for the future.

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.

CGRP and migraine: could PACAP play a role too?

Migraine is a debilitating neurological disorder that affects about 12% of the population. In the past decade, the role of the neuropeptide calcitonin gene-related peptide (CGRP) in migraine has been firmly established by clinical studies. CGRP administration can trigger migraines, and CGRP receptor antagonists ameliorate migraine. In this review, we will describe multifunctional activities of CGRP that could potentially contribute to migraine. These include roles in light aversion, neurogenic inflammation, peripheral and central sensitization of nociceptive pathways, cortical spreading depression, and regulation of nitric oxide production. Yet clearly there will be many other contributing genes that could act in concert with CGRP. One candidate is pituitary adenylate cyclase-activating peptide (PACAP), which shares some of the same actions as CGRP, including the ability to induce migraine in migraineurs and light aversive behavior in rodents. Interestingly, both CGRP and PACAP act on receptors that share an accessory subunit called receptor activity modifying protein-1 (RAMP1). Thus, comparisons between the actions of these two migraine-inducing neuropeptides, CGRP and PACAP, may provide new insights into migraine pathophysiology.

(E)-Alkenes as replacements of amide bonds: development of novel and potent acyclic CGRP receptor antagonists

A new class of CGRP receptor antagonists was identified by replacing the central amide of a previously identified anilide lead structure with ethylene, ethane, or ethyne linkers. (E)-Alkenes as well as alkynes were found to preserve the proper bioactive conformation of the amides, necessary for efficient receptor binding. Further exploration resulted in several potent compounds against CGRP-R with low susceptibility to P-gp mediated efflux.

The calcitonin gene-related peptide receptor antagonist MK-8825 decreases spinal trigeminal activity during nitroglycerin infusion

Background

Calcitonin gene-related peptide (CGRP) and nitric oxide (NO) are regarded as key mediators in migraine and other primary headaches. Migraineurs respond to infusion of nitroglycerin with delayed headaches, and inhibition of CGRP receptors has been shown to be effective in migraine therapy. In animal experiments nitrovasodilators like nitroglycerin induced increases in spinal trigeminal activity, which were reversed after inhibition of CGRP receptors. In the present study we asked if CGRP receptor inhibition can also prevent spinal trigeminal activity induced by nitroglycerin.

Methods

In isoflurane anaesthetised rats extracellular recordings were made from neurons in the spinal trigeminal nucleus with meningeal afferent input. The non-peptide CGRP receptor inhibitor MK-8825 (5 mg/kg) dissolved in acidic saline (pH 3.3) was slowly infused into rats one hour prior to prolonged glyceryl trinitrate (nitroglycerin) infusion (250 μg/kg/h for two hours).

Results

After infusion of MK-8825 the activity of spinal trigeminal neurons with meningeal afferent input did not increase under continuous nitroglycerin infusion but decreased two hours later below baseline. In contrast, vehicle infusion followed by nitroglycerin was accompanied by a transient increase in activity.

Conclusions

CGRP receptors may be important in an early phase of nitroglycerin-induced central trigeminal activity. This finding may be relevant for nitroglycerin-induced headaches.

Pediatric migraine: abortive management in the emergency department

Studies suggest that headache accounts for approximately 1% of pediatric emergency department (ED) visits. ED physicians must distinguish between primary headaches, such as a tension or migraine, and secondary headaches caused by systemic disease including neoplasm, infection, or intracranial hemorrhage. A recent study found that 40% of children presenting to the ED with headache were diagnosed with a primary headache, and 75% of these were migraine. Once the diagnosis of migraine has been made, the ED physician is faced with the challenge of determining appropriate abortive treatment. This review summarizes the most recent literature on pediatric migraine with an emphasis on diagnosis and abortive treatment in the ED.

Capturing the aversive state of cephalic pain preclinically

OBJECTIVE

Preclinical evaluation of headache by behavioral assessment of reward from pain relief.

METHODS

Inflammatory mediators (IMs) or control solution were applied to the rat dura mater to elicit a presumed state of cephalic pain. Hind paw incision was used in separate groups of animals to model noncephalic postsurgical pain. Drugs were given systemically or microinjected within the rostral ventromedial medulla (RVM), nucleus accumbens (NAc), or rostral anterior cingulate cortex (rACC). Peripheral nerve block was produced at the level of the popliteal fossa, and behavior was assessed using evoked sensory stimuli or conditioned place preference (CPP). Immunohistochemistry and brain microdialysis measurements were performed.

RESULTS

Dural IMs produced long-lasting generalized cutaneous allodynia. RVM lidocaine produced CPP, increased NAc c-Fos, and dopamine release selectively in rats receiving dural IMs; CPP was blocked by intra-NAc α-flupenthixol, a dopaminergic antagonist. Intravenous α-calcitonin gene-related peptide (αCGRP)(8-37) produced CPP and elicited NAc dopamine release selectively in rats treated with dural IMs. Prior lesion of the rACC or treatment with systemic sumatriptan or αCGRP(8-37) abolished RVM lidocaine-induced CPP in IM-treated rats. Sumatriptan treatment blocked NAc dopamine release in IM-treated rats receiving RVM lidocaine. Systemic sumatriptan did not alter pain relief-induced CPP in rats with incisional injury.

INTERPRETATION

Cephalic pain was unmasked in rats by assessment of motivated behavior to seek relief. Relief of pain activates the dopaminergic reward pathway to elicit negative reinforcement of behavior. Medications clinically effective for migraine headache selectively elicit relief of ongoing cephalic, but not postsurgical, noncephalic pain. These studies provide a platform for exploring migraine pathophysiology and for the discovery of new headache therapies.

Changes in calcitonin gene-related peptide (CGRP) receptor component and nitric oxide receptor (sGC) immunoreactivity in rat trigeminal ganglion following glyceroltrinitrate pretreatment

BACKGROUND

Nitric oxide (NO) is thought to play an important role in the pathophysiology of migraine. Infusion of the nitrovasodilator glyceroltrinitrate (nitroglycerin, GTN), which mobilizes NO in the organism, is an approved migraine model in humans. Calcitonin gene-related peptide (CGRP) is regarded as another key mediator in migraine. Increased plasma levels of CGRP have been found during spontaneous as well as nitrovasodilator-induced migraine attacks. The nociceptive processes and interactions underlying the NO and CGRP mediated headache are poorly known but can be examined in animal experiments. In the present study we examined changes in immunofluorescence of CGRP receptor components (CLR and RAMP1) and soluble guanylyl cyclase (sGC), the intracellular receptor for NO, in rat trigeminal ganglia after pretreatment with GTN.

METHODS

Isoflurane anaesthetised rats were intravenously infused with GTN (1 mg/kg) or saline for four hours and two hours later the trigeminal ganglia were processed for immunohistochemistry. Different primary antibodies recognizing CLR, RAMP1, CGRP and sGC coupled to fluorescent secondary antibodies were used to examine immunoreactive cells in serial sections of trigeminal ganglia with epifluorescence and confocal laser scanning microscopy. Several staining protocols were examined to yield optimized immunolabeling.

RESULTS

In vehicle-treated animals, 42% of the trigeminal ganglion neurons were immunopositive for RAMP1 and 41% for CLR. After GTN pretreatment CLR-immunopositivity was unchanged, while there was an increase in RAMP1-immunopositive neurons to 46%. RAMP1 and CLR immunoreactivity was also detected in satellite cells. Neurons immunoreactive for sGC were on average smaller than sGC-immunonegative neurons. The percentage of sGC-immunopositive neurons (51% after vehicle) was decreased after GTN infusion (48%).

CONCLUSIONS

Prolonged infusion of GTN caused increased fractions of RAMP1- and decreased fractions of sGC-immunopositive neurons in the trigeminal ganglion. The observed alterations are likely immunophenotypic correlates of the pathophysiological processes underlying nitrovasodilator-induced migraine attacks and indicate that signalling via CGRP receptors but not sGC-mediated mechanisms may be enhanced through endogenous NO production.

Nitric oxide synthase, calcitonin gene-related peptide and NK-1 receptor mechanisms are involved in GTN-induced neuronal activation

BACKGROUND AND AIM

Infusion of glyceryltrinitrate (GTN), a nitric oxide (NO) donor, in awake, freely moving rats closely mimics a universally accepted human model of migraine and responds to sumatriptan treatment. Here we analyse the effect of nitric oxide synthase (NOS) and calcitonin gene-related peptide (CGRP) systems on the GTN-induced neuronal activation in this model.

MATERIALS AND METHODS

The femoral vein was catheterised in rats and GTN was infused (4 µg/kg/min, for 20 minutes, intravenously). Immunohistochemistry was performed to analyse Fos, nNOS and CGRP and Western blot for measuring nNOS protein expression. The effect of olcegepant, L-nitro-arginine methyl ester (L-NAME) and neurokinin (NK)-1 receptor antagonist L-733060 were analysed on Fos activation.

RESULTS

GTN-treated rats showed a significant increase of nNOS and CGRP in dura mater and CGRP in the trigeminal nucleus caudalis (TNC). Upregulation of Fos was observed in TNC four hours after the infusion. This activation was inhibited by pre-treatment with olcegepant. Pre-treatment with L-NAME and L-733060 also significantly inhibited GTN induced Fos expression.

CONCLUSION

The present study indicates that blockers of CGRP, NOS and NK-1 receptors all inhibit GTN induced Fos activation. These findings also predict that pre-treatment with olcegepant may be a better option than post-treatment to study its inhibitory effect in GTN migraine models.

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.

BMS-927711 for the acute treatment of migraine: a double-blind, randomized, placebo controlled, dose-ranging trial

BACKGROUND

BMS-927711 is a potent, selective, competitive human calcitonin gene-related peptide (CGRP) receptor antagonist that has shown in vivo efficacy without vasoconstrictor effect. The objective of the current study was to determine an effective and tolerable dose range of BMS-927711 for the acute treatment of migraine.

METHODS

In this randomized, double-blind, placebo controlled, dose-ranging study, 885 patients were randomized using an adaptive design to one of the following dose groups: BMS-927711 (10, 25, 75, 150, 300, or 600 mg); sumatriptan 100 mg (active comparator); and placebo. Patients were treated for a single migraine attack. The primary endpoint was pain freedom at two hours post-dose.

RESULTS

Of patients who took the study drug, 799 had one post-randomization efficacy evaluation. Significantly more patients in the BMS-927711 75 mg (31.4%, P = 0.002), 150 mg (32.9%, P < 0.001), and 300 mg (29.7%, P = 0.002) groups and the sumatriptan group (35%, P < 0.001) had pain freedom at two hours post-dose versus placebo (15.3%). For the secondary endpoint of sustained pain freedom from two to 24 hours post-dose, BMS-927711 doses (25-600 mg) were also statistically significant compared with placebo. No deaths or treatment-related serious adverse events (AEs) were reported, and no patients discontinued because of AEs.

CONCLUSIONS

BMS-927711 is superior to placebo at several different doses (75 mg, 150 mg, and 300 mg) and has an excellent tolerability profile.

Analysis of the proteolysis of bioactive peptides using a peptidomics approach

Identifying the peptidases that inactivate bioactive peptides (e.g., peptide hormones and neuropeptides) in mammals is an important unmet challenge. This protocol describes a recent approach that uses liquid chromatography-mass spectrometry (LC-MS) peptidomics to identify endogenous cleavage sites of a bioactive peptide; it also addresses the subsequent biochemical purification of a candidate peptidase on the basis of these cleavage sites and the validation of the candidate peptidase's role in the physiological regulation of the bioactive peptide by examining a peptidase-knockout mouse. We highlight the successful application of this protocol in the discovery that insulin-degrading enzyme (IDE) regulates physiological calcitonin gene-related peptide (CGRP) levels, and we detail the key stages and steps in this approach. This protocol requires 7 d of work; however, the total time for this protocol is highly variable because of its dependence on the availability of biological reagents such as purified enzymes and knockout mice. The protocol is valuable because it expedites the characterization of mammalian peptidases, such as IDE, which in certain instances can be used to develop novel therapeutics.

Migraine genes and the relation to gender

Migraine is an episodic brain disorder that is characterized by recurrent attacks of severe unilateral headache that are accompanied by various neurological symptoms. In addition, many patients have what is called an aura with visual and sensory disturbances. The majority of patients are female, suggesting that female hormones play an important role in the pathophysiology of the disorder. The molecular mechanisms, however, underlying this female preponderance are not well understood. It can be expected that the field of genetics that aims at identifying genetic factors that cause migraine by lowering the threshold for attacks will unravel some of these mechanisms. The 3 best known migraine genes encode ion transporters and were identified in families with familial hemiplegic migraine (FHM), a rare subtype of migraine with aura. FHM gene mutations cause alterations in mechanisms that control and modulate the neurotransmitter balance in the brain. Transgenic mice knock-in with human pathogenic mutations that were shown to exhibit some migraine-relevant features were very helpful in dissecting molecular mechanisms of migraine and pointed to a central role for cortical glutamate. In addition, transgenic mice that overexpress human RAMP1 exist and exhibit an increased sensitivity to calcitonin gene-related peptide. Findings from genetic and animal experiments on gender differences in migraine are discussed. Recently, a role for glutamate also came forward from a genome-wide association study in common migraine. By deciphering genetic and pathogenic migraine pathways, it can be expected that in the near future we will better understand mechanisms behind the female preponderance in migraine.

Effect of telcagepant on spontaneous ischemia in cardiovascular patients in a randomized study

OBJECTIVE

The primary purpose of the study was to explore the safety and tolerability of telcagepant in patients with stable coronary artery disease.

BACKGROUND

Triptans are effective acute anti-migraine drugs whose vasoconstrictive effects limit their use in patients at risk for adverse cardiovascular events. Telcagepant, a calcitonin gene-related peptide receptor antagonist, is being developed for the acute treatment of migraine. Antagonism of calcitonin gene-related peptide, which does not appear to cause vasoconstriction, may allow for treatment of migraine in patients with coronary artery disease.

METHODS

In this randomized, double-blind, placebo-controlled, crossover study, patients with documented stable coronary artery disease were assigned to 1 of 2 treatment sequences: telcagepant then placebo, or placebo then telcagepant. In each treatment period, patients received 2 doses of telcagepant 300-mg or placebo 2 hours apart. They remained in the research center for 24 hours after receiving the first dose of each period, during which time continuous 12-lead ambulatory electrocardiographic (Holter) monitoring was performed.

RESULTS

Twenty-eight patients were enrolled; all patients completed the study and were included in all analyses. Telcagepant was generally well tolerated. No laboratory or serious adverse experiences were reported, and no patient discontinued due to an adverse experience. There were no consistent treatment-related changes in laboratory, vital signs or electrocardiogram safety parameters. Three patients (2 after receiving placebo and 1 after receiving telcagepant) experienced ST segment depression during the study; none of these patients reported chest pain.

CONCLUSIONS

Two doses of 300-mg telcagepant, administered 2 hours apart, did not appear to exacerbate spontaneous ischemia and were generally well tolerated in a small cohort of patients with stable coronary artery disease. Results of this study support further evaluation of telcagepant in patients with stable coronary artery disease.