The Role of ICL1 and H8 in Class B1 GPCRs; Implications for Receptor Activlation

The first intracellular loop (ICL1) of G protein-coupled receptors (GPCRs) has received little attention, although there is evidence that, with the 8th helix (H8), it is involved in early conformational changes following receptor activation as well as contacting the G protein β subunit. In class B1 GPCRs, the distal part of ICL1 contains a conserved R12.48KLRCxR2.46b motif that extends into the base of the second transmembrane helix; this is weakly conserved as a [R/H]12.48KL[R/H] motif in class A GPCRs. In the current study, the role of ICL1 and H8 in signaling through cAMP, iCa2+ and ERK1/2 has been examined in two class B1 GPCRs, using mutagenesis and molecular dynamics. Mutations throughout ICL1 can either enhance or disrupt cAMP production by CGRP at the CGRP receptor. Alanine mutagenesis identified subtle differences with regard elevation of iCa2+, with the distal end of the loop being particularly sensitive. ERK1/2 activation displayed little sensitivity to ICL1 mutation. A broadly similar pattern was observed with the glucagon receptor, although there were differences in significance of individual residues. Extending the study revealed that at the CRF1 receptor, an insertion in ICL1 switched signaling bias between iCa2+ and cAMP. Molecular dynamics suggested that changes in ICL1 altered the conformation of ICL2 and the H8/TM7 junction (ICL4). For H8, alanine mutagenesis showed the importance of E3908.49b for all three signal transduction pathways, for the CGRP receptor, but mutations of other residues largely just altered ERK1/2 activation. Thus, ICL1 may modulate GPCR bias via interactions with ICL2, ICL4 and the Gβ subunit.

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.

A Short on Ubrogepant

Migraine is a mysterious disorder characterized by pulsating head ache, which is actually characterized to one side and comes in attacks which will be lasting for about 3-48 hours and can be associated with nausea,vomiting,sensitivity to sound,flashes of light,vertigoand diarrhoea [1]. Most of the drugs which are in current use for actue migraine like triptans, treats the disorder symptomatically. A novel group of drugs has been in research for the migraine which treats the disorder pathologically. Calcitonin gene – related peptide (CGRP) has a major role in the pathophysiology of the disorder and hence CGRP receptor antagonist, known as Gepants are in the research process [2]. Gepants are being studied for the efficacy of treating acute migraine [2]. This article will be a review article about the drug – Ubrogepant, which is approved for treatment of migraine with acute attacks in adults [3].

Native CGRP Neuropeptide and Its Stable Analogue SAX, But Not CGRP Peptide Fragments, Inhibit Mucosal HIV-1 Transmission

BackgroundThe vasodilator neuropeptide calcitonin gene-related peptide (CGRP) plays both detrimental and protective roles in different pathologies. CGRP is also an essential component of the neuro-immune dialogue between nociceptors and mucosal immune cells. We previously discovered that CGRP is endowed with anti-viral activity and strongly inhibits human immunodeficiency virus type 1 (HIV-1) infection, by suppressing Langerhans cells (LCs)-mediated HIV-1 trans-infection in-vitro and mucosal HIV-1 transmission ex-vivo. This inhibition is mediated via activation of the CGRP receptor non-canonical NFκB/STAT4 signaling pathway that induces a variety of cooperative mechanisms. These include CGRP-mediated increase in the expression of the LC-specific pathogen recognition C-type lectin langerin and decrease in LC-T-cell conjugates formation. The clinical utility of CGRP and modalities of CGRP receptor activation, for inhibition of mucosal HIV-1 transmission, remain elusive.MethodsWe tested the capacity of CGRP to inhibit HIV-1 infection in-vivo in humanized mice. We further compared the anti-HIV-1 activities of full-length native CGRP, its metabolically stable analogue SAX, and several CGRP peptide fragments containing its binding C-terminal and activating N-terminal regions. These agonists were evaluated for their capacity to inhibit LCs-mediated HIV-1 trans-infection in-vitro and mucosal HIV-1 transmission in human mucosal tissues ex-vivo.ResultsA single CGRP intravaginal topical treatment of humanized mice, followed by HIV-1 vaginal challenge, transiently restricts the increase in HIV-1 plasma viral loads but maintains long-lasting higher CD4+ T-cell counts. Similarly to CGRP, SAX inhibits LCs-mediated HIV-1 trans-infection in-vitro, but with lower potency. This inhibition is mediated via CGRP receptor activation, leading to increased expression of both langerin and STAT4 in LCs. In contrast, several N-terminal and N+C-terminal bivalent CGRP peptide fragments fail to increase langerin and STAT4, and accordingly lack anti-HIV-1 activities. Finally, like CGRP, treatment of human inner foreskin tissue explants with SAX, followed by polarized inoculation with cell-associated HIV-1, completely blocks formation of LC-T-cell conjugates and HIV-1 infection of T-cells.ConclusionOur results show that CGRP receptor activation by full-length CGRP or SAX is required for efficient inhibition of LCs-mediated mucosal HIV-1 transmission. These findings suggest that formulations containing CGRP, SAX and/or their optimized agonists/analogues could be harnessed for HIV-1 prevention.

Initial experience with novel CGRP-receptor inhibitor therapy in Migraine in the United Arab Emirates: a retrospective observational study

Background Erenumab is a calcitonin gene-related peptide (CGRP)-receptor antibody inhibiting CGRP function. CGRP is prominently involved in the pathophysiology of migraine through nociceptive modulation in the trigeminovascular system. This study aims to explore the treatment effect of erenumab in a real-life setting. Methods In this retrospective observational study, we analyzed the data of 91 patients with migraine receiving at least three consecutive monthly injections of erenumab and followed up for 3–12 months. The primary objective was to describe the reduction in monthly migraine days throughout the follow-up period. To identify patients who responded to treatment, we analyzed the association between different patient characteristics and their treatment outcomes. Results Seventy-three patients (80.2%) responded to erenumab treatment, defined as ≥50% reduction of migraine days per month, across all migraine types. It was noted that ethnicity (p-value = 0.015) and older age (p-value = 0.035) were associated with clinically relevant improvement of symptoms. Middle Eastern ethnicity was related to less improvement of symptoms while Europeans were more likely to benefit from erenumab therapy (odds ratio: 12.788, p = 0.037). Patients aged from 31 to 40 and 41–65 years benefited most from erenumab treatment with a response rate of 77.8 and 89.9%, respectively, also confirmed by logistic regression (p = 0.047). Neither gender nor dose increase of erenumab showed association with the reported clinically relevant improvement of the symptoms. An association between clinically relevant improvement of headaches and the type of migraine was also noted. Around 87.9% of patients with episodic migraine responded to treatment, followed by 84.1% of chronic migraine patients and 50% of medication overuse headache patients. Medication overuse headache showed a lower probability of therapy success with erenumab (odds ratio: 0.126, p = 0.039). An improvement of headaches was eminent in patients who received 140 mg erenumab monthly (2 × 70 mg injections) and patients who had one injection every two weeks. Conclusions Erenumab is a novel preventive treatment for all migraine types. Clinically relevant improvement of headaches and reduction of monthly migraine days were demonstrated in patients that continued the treatment course. In real-life, a substantial number of patients suspended therapy early, reasons for which need further investigation.

Deterioration of headache impact and health-related quality of life in migraine patients after cessation of preventive treatment with CGRP(−receptor) antibodies

Background Migraine preventive treatment with CGRP(−receptor) monoclonal antibodies (mAbs) has a positive effect on patients’ health-related quality of life (HRQoL). The German treatment guidelines recommend discontinuing successful treatment with CGRP(−receptor) mAbs after 6–12 months. We aimed to evaluate headache-specific and generic HRQoL for three months after discontinuation of CGRP(−receptor) mAb treatment. Methods We conducted a prospective, longitudinal cohort study, including patients with migraine after 8–12 months of therapy with a CGRP(−R) mAb and before a planned discontinuation attempt. HRQoL was assessed at the time of the last mAbs injection (V1), eight weeks later (V2), and sixteen weeks later (V3). For headache-specific HRQoL, we used the Headache Impact Test-6 (HIT-6). Generic HRQoL was determined with the EuroQol-5-Dimension-5-Level (ED-5D-5L) form, and the Short-Form 12 (SF-12), which comprises a Physical Component Summary (PCS-12) and a Mental Component Summary (MCS-12). Questionnaires’ total scores were compared across the three observation points using nonparametric procedures. Results The study cohort consisted of n = 61 patients (n = 29 treated with the CGRP-receptor mAb erenumab and n = 32 with the CGRP mAbs galcanezumab or fremanezumab). The HIT-6 sum score was 59.69 ± 6.90 at V1 and increased by 3.69 ± 6.21 at V3 (p < 0.001), indicating a greater headache impact on patients’ lives. The mean total EQ-D5-L5 score declined from 0.85 ± 0.17 at V1 by − 0.07 ± 0.18 at V3 (p = 0.013). Both Mental and Physical Component Scores of the SF-12 worsened significantly during treatment discontinuation: The PCS-12 total score decreased by − 4.04 ± 7.90 from V1 to V3 (p = 0.013) and the MCS-12 score by − 2.73 ± 9.04 (p = 0.003). Changes in all questionnaires’ scores but the MCS-12 were already significant in the first month of the drug holiday (V2). Conclusions Our results show a significant decline in headache impact and generic HRQoL of migraine patients after treatment discontinuation of a CGRP(−R) mAb. The observed deterioration is above the established minimally clinically important differences for each of the questionnaires and can therefore be considered clinically meaningful. Monitoring HRQoL during a discontinuation attempt could facilitate the decision whether or not to resume preventive treatment with CGRP(−R) mAbs.

Treatment of Persistent Post-Traumatic Headache with the Anti-CGRP Receptor Antibody Erenumab: A Case Report

Introduction: Calcitonin gene-related peptide (CGRP) has only recently emerged as a potential target in posttraumatic headache. To our knowledge this is the first description of a patient with persistent posttraumatic headache following severe traumatic head injury who has been treated with the CGRP-receptor-monoclonal antibody erenumab.Case presentation: A 56-year-old man presented with a 30-year history of frequent migraine-like posttraumatic headaches following a high-voltage head injury that he treated with an excessive intake of peripheral analgesics. Although amitriptyline was reasonably effective, it had to be discontinued when the patient developed restless legs syndrome in the second year of treatment. Under therapy with erenumab he achieved a rapid and stable reduction in his symptoms down to only 2–3 headache days per month without adverse events.Conclusions: This case demonstrates that the inhibition of the CGRP-receptor with erenumab could be an effective treatment option in migraine-like post-traumatic headache even decades after the traumatic event.

Effect of antibody switch in non-responders to a CGRP receptor antibody treatment in migraine: A multi-center retrospective cohort study

Background Switching between antibody classes might be a treatment option in migraine patients who have not responded to one class of a CGRP-(receptor) monoclonal antibody (mAb), but there are no efficacy data so far. In this real-world analysis, we assessed the treatment response to a CGRP-mAb in patients that have previously failed the CGRP-receptor-mAb erenumab. Methods We analyzed retrospective headache diary data of 78 patients with migraine who switched between CGRP-mAbs classes at four German headache centers either due to lack of efficacy or intolerable side effects. Among these, we identified 25 patients who did not respond to erenumab after three treatment cycles (defined as <30% reduction of monthly headache days) and had complete headache documentation at least one month before and during both treatments. We assessed the ≥30% responder rate at month three after switching from erenumab to a CGRP-mAb (galcanezumab or fremanezumab) (primary endpoint). Secondary endpoints included ≥50% responder rate, monthly headache days, and monthly days with acute medication use. In an exploratory subgroup analysis patients were stratified for daily and non-daily headache. Results The switch from erenumab to a CGRP-mAb led to a ≥30% response in one-third (32%) of the patients after three treatment cycles. A ≥50% response was achieved in 12% of the patients. Monthly headache days were reduced in month three compared to baseline (20.8 ± 7.1 to 17.8 ± 9.1; p = 0.009). Stratified analysis revealed that no patient with daily headache (n = 9) responded to the treatment switch, while a 30% response was achieved by 50% of patients with non-daily headache (n = 16). Conclusion Our findings demonstrate that a relevant proportion of erenumab non-responders might benefit from a treatment switch to a CGRP-mAb. Switching seems to be a promising treatment option especially in migraine patients with non-daily headache.