Current status of calcitonin gene-related peptide-based therapies in migraine: a scoping review

A significant proportion of patients exhibit sub-optimal response to the standard treatment of acute migraine such as triptans and NSAIDs. Even the conventional preventive therapies (e.g. beta-blockers) indicated for patients with frequent migraine attacks have varying responses. Moreover, evidence from animal studies elucidated the role of calcitonin gene-related peptide (CGRP) in the pathophysiology of migraine. Currently two classes are drug, the small molecule CGRP receptor antagonist or the ‘gepants’ (Ubrogepant, Rimegepant, Atogepant, Zavegepant) and CGRP monoclonal antibodies (Erenumab, Galcanezumab, Fremanezumab, Eptinezumab) have been found efficacious and safe in various clinical trials for the treatment and prevention of migraine. While the small molecule CGRP receptor antagonists are given orally, the monoclonal antibodies are injectable drugs. Ubrogepant and Rimegepant are the second-generation gepants approved for treatment of migraine. Zavegepant is a third generation gepant which has proven efficacy for acute treatment of migraine in a phase III trial. Atogepant has been approved for prevention of migraine. Rimegepant has also proven to be efficacious for preventing migraine attacks but has not yet been approved for this indication. Erenumab is the only monoclonal antibody which neutralizes the CGRP receptor. The latter three monoclonal antibodies target the CGRP peptide. The monoclonal antibodies have been approved for the prevention of migraine as a subcutaneously or intravenous infusion (Eptinezumab) given once a month or quarterly. Both the classes of drugs were well-tolerated in the clinical trials. Nausea was the most common adverse effect with gepants while injection-site pain was commonly reported with the antibodies.

Constipation Caused by Anti-calcitonin Gene-Related Peptide Migraine Therapeutics Explained by Antagonism of Calcitonin Gene-Related Peptide’s Motor-Stimulating and Prosecretory Function in the Intestine

The development of small-molecule calcitonin gene-related peptide (CGRP) receptor antagonists (gepants) and of monoclonal antibodies targeting the CGRP system has been a major advance in the management of migraine. In the randomized controlled trials before regulatory approval, the safety of these anti-CGRP migraine therapeutics was considered favorable and to stay within the expected profile. Post-approval real-world surveys reveal, however, constipation to be a major adverse event which may affect more than 50% of patients treated with erenumab (an antibody targeting the CGRP receptor), fremanezumab or galcanezumab (antibodies targeting CGRP). In this review article we address the question whether constipation caused by inhibition of CGRP signaling can be mechanistically deduced from the known pharmacological actions and pathophysiological implications of CGRP in the digestive tract. CGRP in the gut is expressed by two distinct neuronal populations: extrinsic primary afferent nerve fibers and distinct neurons of the intrinsic enteric nervous system. In particular, CGRP is a major messenger of enteric sensory neurons which in response to mucosal stimulation activate both ascending excitatory and descending inhibitory neuronal pathways that enable propulsive (peristaltic) motor activity to take place. In addition, CGRP is able to stimulate ion and water secretion into the intestinal lumen. The motor-stimulating and prosecretory actions of CGRP combine in accelerating intestinal transit, an activity profile that has been confirmed by the ability of CGRP to induce diarrhea in mice, dogs and humans. We therefore conclude that the constipation elicited by antibodies targeting CGRP or its receptor results from interference with the physiological function of CGRP in the small and large intestine in which it contributes to the maintenance of peristaltic motor activity, ion and water secretion and intestinal transit.

Low Serum Calcitonin Gene-Related Peptide Level is Associated with Severity of Coronary Stenosis

Purpose: To evaluate the relationship between the serum calcitonin gene-related peptide (CGRP) level and severity of coronary stenosis. Methods: A total of 233 eligible patients who underwent coronary angiography were divided into two groups: a control and a coronary heart disease (CHD) group. The angiographic severity of coronary stenosis was evaluated by SYNTAX and Gensini scores. The incidence of major adverse cardiovascular events within two years was collected. Results: A negative correlation between serum CGRP levels and Gensini scores was observed in all patients (r=-0.352, p<0.001), the control group (r=-0.422, p<0.001) and the CHD group (r=-0.393, p<0.001). Serum CGRP levels were negatively associated with SYNTAX scores in the CHD group (r=-0.522, p<0.001). The area under the curve of CGRP for identifying high SYNTAX scores (>22) was 0.772 [95% confidence interval (CI): 0.673-0.870, p<0.001], and for identifying high Gensini scores was 0.744 (95% CI: 0.646-0.842, p<0.001). A CGRP concentration of 25.05 pg/ml was selected as the cutoff point. A low CGRP level (<25.05 pg/ml) was an independent predictor of severe coronary stenosis, a SYNTAX score >22 [odds ratio (OR) =5.819, 95% CI: 2.240-15.116; p<0.001] and a high Gensini score (>64) (OR=4.943, 95% CI: 2.020-12.095; p<0.001). The low CGRP group had a higher incidence of major adverse cardiovascular events within two years (11.1 vs. 3.1%, p=0.031). Conclusion: In coronary atherosclerosis patients without acute myocardial injury, serum CGRP levels were negatively associated with the severity of coronary stenosis.