Post-triptan era for the treatment of acute migraine

Blocking the CGRP Pathway for Acute and Preventive Treatment of Migraine: The Evolution of Success

The pivotal role of calcitonin gene-related peptide (CGRP) in migraine pathophysiology was identified over 30 years ago, but the successful clinical development of targeted therapies has only recently been realized. This Perspective traces the decades long evolution of medicinal chemistry required to advance small molecule CGRP receptor antagonists, also called gepants, including the current clinical agents rimegepant, vazegepant, ubrogepant, and atogepant. Providing clinically effective blockade of CGRP signaling required surmounting multiple challenging hurdles, including defeating a sizable ligand with subnanomolar affinity for its receptor, designing antagonists with an extended confirmation and multiple pharmacophores while retaining solubility and oral bioavailability, and achieving circulating free plasma levels that provided near maximal CGRP receptor coverage. The clinical efficacy of oral and intranasal gepants and the injectable CGRP monoclonal antibodies (mAbs) are described, as are recent synthetic developments that have benefited from new structural biology data. The first oral gepant was recently approved and heralds a new era in the treatment of migraine.

Migraine: A disorder of metabolism?

The treatment and prevention of migraine within the last decade has become largely pharmacological. While there is little doubt that the advent of drugs (e.g. triptans) has helped many migraine sufferers to lead a normal life, there is still little knowledge with respect to the factors responsible for precipitating a migraine attack. Evidence from biochemical and behavioural studies from a number of disciplines is integrated to put forward the proposal that migraine is part of a cascade of events, which together act to protect the organism when confronted by a metabolic challenge.

Expression of calcitonin gene-related peptide, adenosine A2a receptor and adenosine A1 receptor in experiment rat migraine models

A migraine is a disabling neurovascular disorder characterized by a unilateral throbbing headache that lasts from 4 to 72 h. The headache is often accompanied by nausea, vomiting, phonophobia and photophobia, and may be worsened by physical exercise. The trigeminovascular system (TVS) is speculated to have an important role in migraines, although the pathophysiology of this disorder remains to be elucidated. Trigeminal ganglion (TG) and spinal trigeminal nucleus caudalis (TNC) are important components of the TVS. Several clinical cases have provided evidence for the involvement of the brainstem in migraine initiation. Electrical stimulation of the trigeminal ganglion (ESTG) in rats can activate TVS during a migraine attack. Calcitonin gene-related peptide (CGRP) is an important vasoactive compound produced following TVS activation. Numerous studies have revealed that adenosine and its receptors have an important role in pain transmission and regulation process. However, only a few studies have examined whether adenosine A2a receptor (A2aR) and adenosine A1 receptor (A1R) are involved in migraine and nociceptive pathways. In the present study, CGRP, A2aR and A1R expression levels were detected in the TG and TNC of ESTG models through reverse transcription-quantitative polymerase chain reaction and western blot analysis. Tianshu capsule (TSC), a type of Chinese medicine, was also used in the ESTG rat models to examine its influence on the three proteins. Results demonstrated that CGRP, A2aR and A1R mediated pain transmission and the regulation process during migraine and the expression of the three proteins was regulated by TSC.

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.

The TRPV1 receptor and nociception

The capsaicin receptor TRPV1 is an emerging target for the treatment of pain with a unique expression profile in peripheral nociceptors and the ability to show polymodal activation, TRPV1 is an important integrator of responses to inflammatory mediators. Sensitization of TRPV1 during chronic pain is believed to contribute to the transduction of noxious signaling for normally innocuous stimuli and consequently the search for novel TRPV1 therapeutics is intense. The current understanding of the physiological role the receptor, as well as the potential therapeutic utility and emerging liabilities of TRPV1 modulators are discussed.

Prophylaxis of migraine

Migraine is a common primary headache disorder often associated with significant disability. While many individuals are able to limit therapy to acute treatment of attacks, others need medication to reduce the attack frequency and/or severity. Evidence-based guidelines exist regarding indications and goals for migraine preventive treatment. The specific prophylactic approach needs to be individualized taking into account multiple variables. Medications used in this task vary widely in proven efficacy and presumed mechanisms of action. This review's goal is to discuss the issues that guide the decision-making process in migraine preventive treatment.

Migraine: new treatment options from molecular biology

Migraine is a common, disabling, multifactorial, episodic neurovascular disorder of largely unknown etiology. The disease is typically characterized by recurrent attacks of headaches and associated autonomic and neurologic symptoms. Current acute and prophylactic treatment options are far from optimal and in many cases, empirically chosen. Clearly, improved treatment is desperately needed. New drug targets may emerge from molecular research as the unravelling of the molecular basis of migraine should improve our understanding of the disease, notably why patients experience attacks so frequently. The first two migraine genes discovered in families with hemiplegic migraine encode ion transporters, emphasising that dysfunction of ion transport may be an important factor in migraine. Therefore, ion transporters can be considered as novel targets for the development of future antimigraine drugs. Molecular biologic research will increasingly become important in understanding the pathophysiology of migraine and in identifying potential molecular targets for novel treatments.

Can we Develop Neurally Acting Drugs for the Treatment of Migraine?

Serotonin (5-HT)(1B/1D) receptor agonists, which are also known as triptans, represent the most important advance in migraine therapeutics in the four millennia that the condition has been recognized. The vasoconstrictive activity of triptans produced a small clinical penalty in terms of coronary vasoconstriction but also raised an enormous intellectual question: to what extent is migraine a vascular problem? Functional neuroimaging and neurophysiological studies have consistently developed the theme of migraine as a brain disorder and, therefore, demanded that the search for neurally acting antimigraine drugs should be undertaken. The prospect of non-vasoconstrictor acute migraine therapies, potential targets for which are discussed here, offers a real opportunity to patients and provides a therapeutic rationale that places migraine firmly in the brain as a neurological problem, where it undoubtedly belongs.

Traitement des céphalées trigémino-vasculaires : nouveautés et perspectives

Remarkable therapeutic improvements have come forward recently for trigemino-autonomic cephalalgias. Attack treatment in cluster headache is based on sumatriptan and oxygen. Non-vasoconstrictive treatments are opening a new post-triptan era but are not yet applicable. Prophylactic treatment of cluster headache is based on verapamil and lithium. The efficacy of anti-epileptic drugs in cluster headache remains to be demonstrated. Surgical treatment aimed at the parasympathetic pathways and at the trigeminal nerve demonstrates a high rate of recurrence and adverse events and questions about the relevance of a "peripheral" target in cluster headache. The efficacy of continuous hypothalamic stimulation in patients with intractable headache constitutes a breakthrough, but must be demonstrated at a larger scale and the benefice/risk ratio must be carefully evaluated. Indomethacin still remains the gold standard in paroxysmal hemicrania treatment. Until recently SUNCT was considered an intractable condition. However there are some reports of complete relief with lamotrigine, topiramate and gabapentin.

New targets in the acute treatment of headache

PURPOSE OF REVIEW

The aim of this article is to review recently identified targets for the acute treatment of primary headache disorders.

RECENT FINDINGS

Calcitonin gene-related peptide (CGRP) receptor blockade has been shown to be an effective acute anti-migraine strategy and is a non-vasoconstrictor in terms of the mechanism of action. It is likely that direct blockade of CGRP release by inhibition of trigeminal nerves would be similarly effective in both migraine and cluster headache. Options for acute treatment based on preclinical work and initial clinical studies include: serotonin 5HT1F and 5HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Proof of principle studies with octreotide, a somatostatin receptor agonist, demonstrated it to be better than placebo in the acute treatment of cluster headache but not in the acute management of migraine.

SUMMARY

The prospect of a non-vasoconstrictor acute migraine therapy offers a real opportunity to patients, and perhaps more importantly, provides a therapeutic rationale to plant migraine and cluster headache firmly in the brain as neurological problems.

Migraine headache: Options for acute treatment

The optimal acute treatment of migraine requires recognition of the multitude of migraine presentations, the frequency of total attacks, and number of days of headache disability. These initial diagnostic steps are initiated in the waiting room, but phase-specific and stratified treatment selection requires having mutual understanding, trust, and belief through extensive discussion. The imperative acute treatment goal must be to treat early, but not too often, a fact represented by a 75% or better occurrence of pain freedom at 2 hours with two or fewer drug doses averaging 2 or fewer days a week. Migraine-specific therapy best wins the race against time and allodynia. Employing this formulary, multiple triptan formulations and phase and stratified patient-centered therapy creates success.