Feasibility of serum CGRP measurement as a biomarker of chronic migraine: a critical reappraisal

OnabotulinumtoxinA injection in the treatment of chronic migraine

The earliest descriptions of botulism were in the early 19th century, and was reported by the German physician Justinus Kerner. The term "botulism" was derived from the Latin word botulus, indicating its original association with sausages. It took another 150 years or so to come into clinical use. The first clinical application was strabismus, and was developed by the American ophthalmologist Alan B. Scott, whose effort led to the pharmaceutical product known as onabotulinumtoxinA today. The therapeutic benefit in migraine was an incidental finding in a report by the American plastic surgeon William J. Binder, which inspired a series of clinical studies in headache disorders. The doses and injection techniques in the earlier reports were variable, so were the results. It was until the Phase III REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) 1 and 2 studies when its efficacy and safety, as well as the indication, i.e., chronic migraine (CM), were ascertained. Even though there were criticisms regarding the heterogeneities in the results between the PREEMPT 1 and 2 studies, the data on efficacy endpoints and safety were generally consistent, which were subsequently confirmed by the open-label extension of the PREEMPT 1 and 2 studies, and three open-label studies, namely the Chronic Migraine OnabotulinuMtoxinA Prolonged Efficacy open Label (COMPEL), the REal-life use of botulinum toxin for the symptomatic treatment of adults with chronic migraine, measuring healthcare resource utilization, and Patient-reported OutcomeS observed in practice (REPOSE) studies, and the CM Post-Authorization Safety Study (CM PASS) studies. On the other hand, the results were challenged by the Chronification and Reversibility of Migraine (CHARM) study, which involved CM patients with medication overuse. It was concluded that the clinical improvement was attributed to early withdrawal of the overused acute medications, rather than onabotulinumtoxinA injections. However, fundamental differences in the patient profile and methodology between the CHARM and PREEMPT studies existed, and cautious should be exercised when interpreting and comparing the results. According to the practical guidelines and reimbursement regulations in many countries, its use is limited to CM patients, and is reserved for those who fail at least 2-3 preventive medications, due to either lack of efficacy or intolerability. Cessation of treatment is recommended in patients who do not respond to 2-3 injection cycles, or in patients whose headache frequency has dropped to <10-15 days a month. Even in the era of calcitonin-gene-related peptide monoclonal antibodies, onabotulinumtoxinA injection remains a treatment option of reasonable cost-effectiveness in carefully selected patients.

Dual Therapy With Anti-CGRP Monoclonal Antibodies and Botulinum Toxin for Migraine Prevention: Is There a Rationale?

OBJECTIVE

To narratively review the pathophysiological rationale of dual therapy with anti-calcitonin gene-related peptide monoclonal antibodies and botulinum toxin type A in treatment-resistant chronic migraine prevention.

BACKGROUND

For the prevention of chronic migraine, several pharmacological therapies are available, including oral medications, botulinum toxin type A, and the newly approved monoclonal antibodies targeting calcitonin gene-related peptide or its receptor. However, monotherapy does not yield benefits in some affected individuals, which raises the question of whether dual therapy with monoclonal antibodies and botulinum toxin type A hold promise in patients with treatment-resistant chronic migraine.

METHOD

We searched MEDLINE for articles published from database inception to December 31st, 2019. Publications were largely selected from the past 10 years but commonly referenced and highly regarded older publications were not excluded.

RESULTS

Preclinical data suggest that anti-calcitonin gene-related peptide monoclonal antibodies and botulinum toxin type A have synergistic effects within the trigeminovascular system. Of note, findings indicate that fremanezumab - an antibody targeting the calcitonin gene-related peptide - mainly prevents the activation of Aδ-fibers, whereas botulinum toxin type A prevents the activation of C-fibers.

CONCLUSION

There is currently only indirect preclinical evidence to support a rationale for dual therapy with anti-calcitonin gene-related peptide monoclonal antibodies and botulinum toxin type A for chronic migraine prevention. Rigorous studies evaluating clinical efficacy, safety, and cost-effectiveness are needed.

From transformation to chronification of migraine: pathophysiological and clinical aspects

Chronic migraine is a neurological disorder characterized by 15 or more headache days per month of which at least 8 days show typical migraine features. The process that describes the development from episodic migraine into chronic migraine is commonly referred to as migraine transformation or chronification. Ample studies have attempted to identify factors associated with migraine transformation from different perspectives. Understanding CM as a pathological brain state with trigeminovascular participation where biological changes occur, we have completed a comprehensive review on the clinical, epidemiological, genetic, molecular, structural, functional, physiological and preclinical evidence available.

Fremanezumab for the preventive treatment of migraine in adults

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

Are antimigraine drugs that influence CGRP levels justified?

Migraine is one of the most common disorders found in everyday clinical practice. Although migraines are not directly life-threatening or permanently disabling, the severity of the pain and symptoms that characterize a migraine attack often prevent normal work and cause difficulties in everyday life. Migraines also affect the patient's family, who often experience stress and depression in response to the patient's condition. Available therapy, used in both acute and chronic treatments, might not provide sufficient improvement. Due to problems like therapy inefficacy, side effects, and intolerance, patients often stop treatments. Recent studies have indicated that drugs that act through calcitonin gene-related peptide (CGRP) can significantly improve migraine therapy. Here, we review results from currently available clinical trials on CGRP receptor antagonists and anti-CGRP monoclonal antibodies.

Calcitonin gene-related peptide levels in tear fluid are elevated in migraine patients compared to healthy controls

BACKGROUND

Calcitonin gene-related peptide (CGRP) released from trigeminal nerve fibres indicates trigeminal activation and has a key role in migraine pathophysiology. The trigeminal nerve directly innervates the eye. Therefore, in this study, we compared Calcitonin gene-related peptide in tear fluid of migraine patients and healthy controls.

METHODS

Calcitonin gene-related peptide concentrations in tear fluid and plasma of 48 episodic and 45 chronic migraine patients and 48 controls were assessed using ELISA.

RESULTS

Calcitonin gene-related peptide levels in tear fluid (0.94 ± 1.11 ng/ml) were ∼140 times higher than plasma concentrations (6.81 ± 4.12 pg/ml). Tear fluid CGRP concentrations were elevated in interictal migraine patients (1.10 ± 1.27 ng/ml, n = 49) compared to controls (0.75 ± 0.80 ng/ml, p = 0.022). There was no difference in tear fluid CGRP levels between interictal episodic and chronic migraine patients (episodic: 1.09 ± 1.47 ng/ml, n = 30 and chronic: 1.10 ± 0.89 ng/ml, n = 19) and no correlation of tear fluid CGRP levels with headache frequency in interictal patients (rho = 0.062, p = 0.674). Unmedicated ictal migraine patients had even more elevated tear fluid CGRP levels than interictal migraine patients (1.92 ± 1.84 ng/ml, n = 13, p = 0.102), while medicated ictal migraine patients had lower levels (0.56 ± 0.47 ng/ml, n = 25, p = 0.011 compared to interictal patients), which were undistinguishable from controls (p = 0.609). In contrast to tear fluid, no significant group differences were found in plasma CGRP levels.

CONCLUSION

To the best of our knowledge, this study shows, for the first time, increased CGRP tear fluid levels in migraine patients compared to healthy subjects. Detection of calcitonin gene-related peptide in tear fluid is non-invasive, and likely allows a more direct access to CGRP released from the trigeminal nerve than plasma sampling.

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.

Potential biomarkers for persistent and neuropathic pain therapy

Persistent, in particular neuropathic pain affects millions of people worldwide. However, the response rate of patients to existing analgesic drugs is less than 50%. There are several possibilities to increase this response rate, such as optimization of the pharmacokinetic and pharmacodynamic properties of analgesics. Another promising approach is to use prognostic biomarkers in patients to determine the optimal pharmacological therapy for each individual. Here, we discuss recent efforts to identify plasma and CSF biomarkers, as well as genetic biomarkers and sensory testing, and how these readouts could be exploited for the prediction of a suitable pharmacological treatment. Collectively, the information on single biomarkers may be stored in knowledge bases and processed by machine-learning and related artificial intelligence techniques, resulting in the optimal pharmacological treatment for individual pain patients. We highlight the potential for biomarker-based individualized pain therapies and discuss biomarker reliability and their utility in clinical practice, as well as limitations of this approach.

CGRP-based Migraine Therapeutics: How Might They Work, Why So Safe, and What Next?

Migraine is a debilitating neurological condition that involves the neuropeptide calcitonin gene-related peptide (CGRP). An exciting development is the recent FDA approval of the first in an emerging class of CGRP-targeted drugs designed to prevent migraine. Yet despite this efficacy, there are some fundamental unanswered questions, such as where and how CGRP works in migraine. Preclinical data suggest that CGRP acts via both peripheral and central mechanisms. The relevance of peripheral sites is highlighted by the clinical efficacy of CGRP-blocking antibodies, even though they do not appreciably cross the blood-brain barrier. The most likely sites of action are within the dura and trigeminal ganglia. Furthermore, it would be foolish to ignore perivascular actions in the dura since CGRP is the most potent vasodilatory peptide. Ultimately, the consequence of blocking CGRP or its receptor is reduced peripheral neural sensitization. Underlying their efficacy is the question of why the antibodies have such an excellent safety profile so far. This may be due to the presence of a second CGRP receptor and vesicular release of a large bolus of peptides. Finally, despite the promise of these drugs, there are unmet gaps because they do not work for all patients; so what next? We can expect advances on several fronts, including CGRP receptor structures that may help development of centrally-acting antagonists, combinatorial treatments that integrate other therapies, and development of drugs that target other neuropeptides. This is truly an exciting time for CGRP and the migraine field with many more discoveries on the horizon.