Effects of PDE-3 inhibition in persistent post-traumatic headache: evidence of cAMP-dependent signaling

BACKGROUND

Phosphodiesterase 3 (PDE-3) inhibition have been implicated in the neurobiologic underpinnings of migraine. Considering the clinical similarities between migraine and persistent post-traumatic headache (PPTH), we aimed to ascertain whether PDE-3 inhibition can elicit migraine-like headache in persons with PPTH.

METHODS

We tested cilostazol, which inhibits PDE-3, in a randomized, double-blind, placebo-controlled, two-way crossover study involving persons with PPTH attributed to mild traumatic brain injury. The randomized participants were allocated to receive oral administration of either 200-mg cilostazol or placebo (calcium tablet) on two separate experiment days. The primary end point was the incidence of migraine-like headache during a 12-hour observation window post-ingestion. The secondary endpoint was the area under the curve (AUC) for reported headache intensity scores during the same observation window.

RESULTS

Twenty-one persons underwent randomization and completed both experiment days. The mean participants' age was 41.4 years, and most (n = 17) were females. During the 12-hour observation window, 14 (67%) of 21 participants developed migraine-like headache post-cilostazol, in contrast to three (14%) participants after placebo (P =.003). The headache intensity scores were higher post-cilostazol than after placebo (P <.001).

CONCLUSIONS

Our results provide novel evidence showing that PDE-3 inhibition can elicit migraine-like headache in persons with PPTH. Given that PDE-3 inhibition increases intracellular cAMP levels, our findings allude to the potential therapeutic value of targeting cAMP-dependent signaling pathways in the management of PPTH. Further investigations are imperative to substantiate these insights and delineate the importance of cAMP-dependent signaling pathways in the neurobiologic mechanisms underlying PPTH.

CLINICALTRIALS

GOV IDENTIFIER

NCT05595993.

Second messenger signalling bypasses CGRP receptor blockade to provoke migraine attacks in humans

There are several endogenous molecules that can trigger migraine attacks when administered to humans. Notably, calcitonin gene-related peptide (CGRP) has been identified as a key player in a signalling cascade involved in migraine attacks, acting through the second messenger cyclic adenosine monophosphate (cAMP) in various cells, including intracranial vascular smooth muscle cells. However, it remains unclear whether intracellular cAMP signalling requires CGRP receptor activation during a migraine attack in humans. To address this question, we conducted a randomized, double-blind, placebo-controlled, parallel trial using a human provocation model involving the administration of CGRP and cilostazol in individuals with migraine pretreated with erenumab or placebo. Our study revealed that migraine attacks can be provoked in patients by cAMP-mediated mechanisms using cilostazol, even when the CGRP receptor is blocked by erenumab. Furthermore, the dilation of cranial arteries induced by cilostazol was not influenced by the CGRP receptor blockade. These findings provide clinical evidence that cAMP-evoked migraine attacks do not require CGRP receptor activation. This discovery opens up new possibilities for the development of mechanism-based drugs for the treatment of migraine.

Future targets for migraine treatment beyond CGRP

BACKGROUND

Migraine is a disabling and chronic neurovascular headache disorder. Trigeminal vascular activation and release of calcitonin gene-related peptide (CGRP) play a pivotal role in the pathogenesis of migraine. This knowledge has led to the development of CGRP(-receptor) therapies. Yet, a substantial proportion of patients do not respond to these treatments. Therefore, alternative targets for future therapies are warranted. The current narrative review provides a comprehensive overview of the pathophysiological role of these possible non-CGRP targets in migraine.

FINDINGS

We covered targets of the metabotropic receptors (pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), amylin, and adrenomedullin), intracellular targets (nitric oxide (NO), phosphodiesterase-3 (PDE3) and -5 (PDE5)), and ion channels (potassium, calcium, transient receptor potential (TRP), and acid-sensing ion channels (ASIC)). The majority of non-CGRP targets were able to induce migraine-like attacks, except for (i) calcium channels, as it is not yet possible to directly target channels to elucidate their precise involvement in migraine; (ii) TRP channels, activation of which can induce non-migraine headache; and (iii) ASICs, as their potential in inducing migraine attacks has not been investigated thus far. Drugs that target its receptors exist for PACAP, NO, and the potassium, TRP, and ASIC channels. No selective drugs exist for the other targets, however, some existing (migraine) treatments appear to indirectly antagonize responses to amylin, adrenomedullin, and calcium channels. Drugs against PACAP, NO, potassium channels, TRP channels, and only a PAC₁ antibody have been tested for migraine treatment, albeit with ambiguous results.

CONCLUSION

While current research on these non-CGRP drug targets has not yet led to the development of efficacious therapies, human provocation studies using these targets have provided valuable insight into underlying mechanisms of migraine headaches and auras. Further studies are needed on these alternative therapies in non-responders of CGRP(-receptor) targeted therapies with the ultimate aim to pave the way towards a headache-free future for all migraine patients.

Future prophylactic treatments in migraine: Beyond anti-CGRP monoclonal antibodies and gepants

Migraine is ranked as a leading cause of years lived with disability among all neurological disorders. Therapies targeting the calcitonin gene-related peptide (CGRP) signaling pathway, including monoclonal antibodies against the receptor or ligand and small molecule CGRP receptor antagonists (gepants), are today approved for migraine prophylaxis with additional compounds expected to be introduced to the market soon. In this review, we consider other putative prophylactic migraine drugs in development, including compounds targeting G-protein coupled receptors, glutamate, ion channels, and neuromodulatory devices. Emergence of these new interventions could complement our current treatment armamentarium for migraine management.

Early treatment with sumatriptan prevents PACAP38-induced migraine: A randomised clinical trial

OBJECTIVE

To determine whether early treatment with sumatriptan can prevent PACAP38-induced migraine attacks.

METHODS

A total of 37 patients with migraine without aura were enrolled between July 2018 to December 2019. All patients received an intravenous infusion of 10 picomole/kg/min of PACAP38 over 20 min followed by an intravenous infusion of 4 mg sumatriptan or placebo over 10 min on two study days in a randomised, double-blind, placebo-controlled, crossover study.

RESULTS

Of 37 patients enrolled, 26 (70.3%) completed the study and were included in analyses. Of the 26 patients, four (15%) developed a PACAP38-induced migraine attack on sumatriptan and 11 patients (42%) on placebo (p = 0.016). There were no differences in area under the curve for headache intensity between sumatriptan (mean AUC 532) and placebo (mean AUC 779) (p = 0.35). Sumatriptan significantly constricted the PACAP38-dilated superficial temporal artery immediately after infusion (T30) compared with infusion of placebo (p < 0.001).Conclusions and relevance: Early treatment with intravenously administered sumatriptan prevented PACAP38-induced migraine. Prevention of migraine attacks was associated with vasoconstriction by sumatriptan in the earliest phases of PACAP provocation. These results suggest that sumatriptan prevents PACAP38-induced migraine by modulation of nociceptive transmission within the trigeminovascular system.Trial Registration: ClinicalTrials.gov (NCT03881644).

Association Between Sumatriptan Treatment During a Migraine Attack and Central 5-HT1B Receptor Binding

Importance

Triptans, the most efficient acute treatment for migraine attacks, are 5-HT1B/1D receptor agonists, but their precise mechanism of action is not completely understood. The extent to which triptans enter the central nervous system and bind to 5-HT1B receptors in the brain is unknown.

Objectives

To determine the occupancy of sumatriptan to central 5-HT1B receptors, and to investigate changes in brain serotonin levels during migraine attacks.

Design, Setting, and Participants

This study of 8 patients in Denmark used a within-participant design and was conducted from April 20, 2015, to December 5, 2016. Participants were otherwise healthy patients with untreated episodic migraine without aura, aged between 18 and 65 years, and recruited from the general community. Data analysis was performed from January 2017 to April 2018.

Interventions

All participants underwent positron emission tomographic scans after injection of [11C]AZ10419369, a specific 5-HT1B receptor radiotracer. All participants were scanned 3 times: (1) during an experimentally induced migraine attack, (2) after a subcutaneous injection of 6-mg subcutaneous sumatriptan, and (3) on a migraine attack-free day. Scans 1 and 2 were conducted on the same study day. Each scan lasted for 90 minutes.

Main Outcome and Measure

The primary outcome was the nondisplaceable binding potential of [11C]AZ10419369 across 7 brain regions involved in pain modulation. The binding potential reflects receptor density, and changes in binding potential reflects displacement of the radiotracer. The occupancy of sumatriptan was estimated from the 2 scans before and after sumatriptan administration.

Results

Eight patients with migraine were included in the study; of these participants, 7 (87%) were women. The mean (SD) age of participants on study day 1 was 29.5 (9.2) years and on study day 2 was 30.0 (8.9) years. Sumatriptan was associated with statistically significantly reduced 5-HT1B receptor binding across pain-modulating regions (mean [SD] binding potential, 1.20 [0.20] vs 1.02 [0.22]; P = .001), corresponding to a mean (SD) drug occupancy rate of 16.0% (5.3%). Furthermore, during migraine attacks, as compared with outside of attacks, 5-HT1B receptor binding was statistically significantly associated with reduced in pain-modulating regions (mean [SD] binding potential, 1.36 [0.22] vs 1.20 [0.20]; P = .02).

Conclusions and Relevance

Treatment with sumatriptan during migraine attacks appeared to be associated with a decrease in 5-HT1B receptor binding, a finding that is most likely associated with the binding of sumatriptan to central 5-HT1B receptors, but the contribution of ongoing cerebral serotonin release to the lower binding cannot be excluded; the migraine attack-associated decrease in binding could indicate that migraine attacks are associated with increases in endogenous serotonin.

Subcutaneous sumatriptan reduces cilostazol induced headache in migraine patients

OBJECTIVES

The authors have previously tried to develop a model for the testing of novel drug candidates for migraine, using the headache and migraine provoking agent cilostazol. Previous studies have used sumatriptan tablets as the validating drug, but they were not sufficiently effective. In this study we test the effect of subcutaneous sumatriptan on cilostazol induced headache in patients with migraine without aura.

METHOD

Thirty patients with migraine without aura received 200 mg cilostazol on two different study days. The induced headache was treated with subcutaneous sumatriptan in a randomized, double-blind cross-over design. The patients filled out a self-reported headache questionnaire until 12 h after cilostazol.

RESULTS

All 30 patients experienced headache (range 3-10) on both study days and the headache fulfilled the criteria for a migraine-like attack in 73% on the sumatriptan day and in 77% on the placebo day. Sumatriptan injection reduced the headache score 2 h after treatment (p = 0.003). The difference between headache intensity on the sumatriptan day and the placebo day was significant at both 2 h (p = 0.01) and 4 h (p = 0.0007) after treatment.

CONCLUSION

Subcutaneous sumatriptan reduces cilostazol induced headache in migraine patients. The cilostazol model may be useful as a tool to test the potential of new anti-migraine drugs.Trial registration: The study is registered on clinicaltrials.gov (NCT03422796).

Progress in the Mechanism and Clinical Application of Cilostazol

Cilostazol is a unique platelet inhibitor that has been used clinically for more than 20 years. As a phosphodiesterase type III inhibitor, cilostazol is capable of reversible inhibition of platelet aggregation and vasodilation, has antiproliferative effects, and is widely used in the treatment of peripheral arterial disease, cerebrovascular disease, percutaneous coronary intervention, etc. This article briefly reviews the pharmacological mechanisms and clinical application of cilostazol.

Therapeutic targeting of 3',5'-cyclic nucleotide phosphodiesterases: inhibition and beyond

Phosphodiesterases (PDEs), enzymes that degrade 3',5'-cyclic nucleotides, are being pursued as therapeutic targets for several diseases, including those affecting the nervous system, the cardiovascular system, fertility, immunity, cancer and metabolism. Clinical development programmes have focused exclusively on catalytic inhibition, which continues to be a strong focus of ongoing drug discovery efforts. However, emerging evidence supports novel strategies to therapeutically target PDE function, including enhancing catalytic activity, normalizing altered compartmentalization and modulating post-translational modifications, as well as the potential use of PDEs as disease biomarkers. Importantly, a more refined appreciation of the intramolecular mechanisms regulating PDE function and trafficking is emerging, making these pioneering drug discovery efforts tractable.

CGRP in Human Models of Migraine

Over the past three decades, calcitonin gene-related peptide (CGRP) has emerged as a key molecule. Provocation experiments have demonstrated that intravenous CGRP infusion induces migraine-like attacks in migraine with and without aura patients. In addition, these studies have revealed a heterogeneous CGRP response, i.e., some migraine patients develop migraine-like attacks after CGRP infusion, while others do not. The role of CGRP in human migraine models has pointed to three potential sites of CGRP-induced migraine: (1) vasodilation via cyclic adenosine monophosphate (cAMP) and possibly cyclic guanosine monophosphate (cGMP); (2) activation of trigeminal sensory afferents, and (3) modulation of deep brain structures. In the future, refined human experimental studies will continue to unveil the role of CGRP in migraine pathogenesis.

Migraine induction with calcitonin gene-related peptide in patients from erenumab trials

BACKGROUND

Migraine prevention with erenumab and migraine induction by calcitonin gene-related peptide (CGRP) both carry notable individual variance. We wanted to explore a possible association between individual efficacy of anti-CGRP treatment and susceptibility to migraine induction by CGRP.

METHODS

Thirteen migraine patients, previously enrolled in erenumab anti-CGRP receptor monoclonal antibody trials, received CGRP in a double-blind, placebo-controlled, randomized cross-over design to investigate their susceptibility to migraine induction. A standardized questionnaire was used to assess the efficacy of previous antibody treatment. The patients were stratified into groups of high responders and poor responders. Primary outcomes were incidence of migraine-like attacks and area under the curve of headache intensity after infusion of CGRP and placebo. All interviews and experiments were performed in laboratories at the Danish Headache Center, Copenhagen, Denmark.

RESULTS

Ten high responders and three poor responders were included. CGRP induced migraine-like attacks in ten (77%) patients, whereof two were poor responders, compared to none after placebo (p = 0.002). The area under the curve for headache intensity was greater after CGRP, compared to placebo, at 0-90 min (p = 0.009), and 2-12 h (p = 0.014). The median peak headache intensity score was 5 (5-9) after CGRP, compared to 2 (0-4) after placebo (p = 0.004).

CONCLUSIONS

Patients with an excellent effect of erenumab are highly susceptible to CGRP provocation. If an association is evident, CGRP provocation could prove a biomarker for predicting antibody treatment efficacy.

TRIAL REGISTRATION

Retrospectively registered at clinicaltrials.gov with identifier: NCT03481400 .

Cilostazol induced migraine does not respond to sumatriptan in a double blind trial

BACKGROUND

Cilostazol is an inhibitor of phosphodiesterase 3 and thus causes accumulation of cAMP. It induces migraine-like attacks in migraine patients. Whether the cilostazol model responds to sumatriptan in migraine patients and therefore is valid for testing of future anti-migraine medications has never been investigated.

METHODS

In a cross-over study, 30 patients received cilostazol (200 mg p.o.) on two separate days each day followed by oral self-administered placebo or sumatriptan 50 mg. We recorded headache characteristics and associated symptoms using a questionnaire. The 30 participants were asked to subsequently treat their spontaneous attacks with sumatriptan (50 mg) or placebo in a double-blind cross-over design and 15 participants did so.

RESULTS

Cilostazol induced headache with some migraine characteristics in all participants; 18 patients on the sumatriptan day and 19 patients on the placebo day fulfilled criteria for a migraine-like attack. The difference in median headache intensity between sumatriptan and placebo at 2 h was not significant (p = 0.09), but it was at 4 h (p = 0.017). During spontaneous attacks, the difference between placebo and sumatriptan was not significant at 2 h (p = 0.26), but it was highly significant at 4 h (p = 0.006).

CONCLUSION

The cilostazol model in migraine patients could not be validated by a sufficient sumatriptan response. The model may perhaps respond to new drugs that act intracellularly or directly on ion channels.

TRIAL REGISTRATION

The study is registered on clinicaltrials.gov ( NCT02486276 ).

Pituitary adenylate cyclase-activating polypeptide receptors in the trigeminovascular system: implications for migraine

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been implicated in a wide range of functions including vasodilatation, neuroprotection, nociception and neurogenic inflammation. PACAP activates three distinct receptors, the PAC₁ receptor, which responds to PACAP, and the VPAC₁ and VPAC₂ receptors, which respond to both PACAP and vasoactive intestinal polypeptide. The trigeminovascular system plays a key role in migraine and contains the trigeminal nerve, which is the major conduit of craniofacial pain. PACAP is expressed throughout the trigeminovascular system and in higher brain regions involved in processing pain. Evidence from human clinical studies suggests that PACAP may act outside the blood-brain barrier in the pathogenesis of migraine. However, the precise mechanisms involved remain unclear. PACAP potentially induces migraine attacks by activating different receptors in different cell types and tissues. This complexity prompted this review of PACAP receptor pharmacology, expression and function in the trigeminovascular system. Current evidence suggests that the PAC₁ receptor is the likely pathophysiological target of PACAP in migraine. However, multiple PACAP receptors are expressed in key parts of the trigeminovascular system and further work is required to determine their contribution to PACAP physiology and the pathology of migraine.

LINKED ARTICLES

This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.