CGRP receptor antagonists: an expanding drug class for acute migraine?

Preparation of imidazoles as potent calcitonin gene-related peptide (CGRP) antagonists

Several new potent CGRP receptor antagonists have been prepared in which the amide bond of lead compound 1 has been replaced by bioisosteric imidazole moieties. Substitution at N-1 of the imidazole was optimized to afford compounds with comparable potency to that of lead 1. Conformational restraint of the imidazole to form tetrahydroimidazo[1,5-a]pyrazine 43 gave substantially improved permeability.

Steroids for preventing recurrence of acute severe migraine headaches: a meta-analysis

BACKGROUND AND PURPOSE

Recurrence of migraine headaches after treatment is common. The evidence regarding steroids for preventing migraine headache recurrence is controversial. This meta-analysis examined the effectiveness of steroids for prevention of recurrent headaches.

METHODS

Databases (PubMed, Embase and the Cochrane Library) and conference proceedings were searched for randomized controlled trials comparing steroids and placebo in the treatment of migraine headaches. Two independent reviewers assessed studies and extracted data. Relative risks (RRs) of headache recurrence and adverse events were calculated and reported with 95% confidence intervals (95% CIs).

RESULTS

Eight studies with 905 patients were included. Pooled analysis showed that when steroids were added to standard abortive therapy they reduced the rate of moderate or severe headache recurrence after 24-72 h of follow-up evaluation (RR = 0.71; 95% CI = 0.59-0.86). There was no significant benefit of steroids compared with placebo in the proportion of totally resolved migraines (RR = 1.11; 95% CI = 0.94-1.32). The side effects of steroids are mild and not significant except for dizziness. Subgroup meta-analysis showed that parenteral dexamethasone tends to be more effective in reducing moderate or severe recurrent headaches (RR = 0.68; 95% CI = 0.55-0.84). However, no significant differences were found between oral administration and parenteral administration of steroids (P = 0.37).

CONCLUSION

When steroids are added to standard abortive therapy for migraine headaches, they are effective and safe for preventing moderate or severe headache recurrence.

Cortical spreading depression as a target for anti-migraine agents

Spreading depression (SD) is a slowly propagating wave of neuronal and glial depolarization lasting a few minutes, that can develop within the cerebral cortex or other brain areas after electrical, mechanical or chemical depolarizing stimulations. Cortical SD (CSD) is considered the neurophysiological correlate of migraine aura. It is characterized by massive increases in both extracellular K⁺ and glutamate, as well as rises in intracellular Na⁺ and Ca²⁺. These ionic shifts produce slow direct current (DC) potential shifts that can be recorded extracellularly. Moreover, CSD is associated with changes in cortical parenchymal blood flow. CSD has been shown to be a common therapeutic target for currently prescribed migraine prophylactic drugs. Yet, no effects have been observed for the antiepileptic drugs carbamazepine and oxcarbazepine, consistent with their lack of efficacy on migraine. Some molecules of interest for migraine have been tested for their effect on CSD. Specifically, blocking CSD may play an enabling role for novel benzopyran derivative tonabersat in preventing migraine with aura. Additionally, calcitonin gene-related peptide (CGRP) antagonists have been recently reported to inhibit CSD, suggesting the contribution of CGRP receptor activation to the initiation and maintenance of CSD not only at the classic vascular sites, but also at a central neuronal level. Understanding what may be lying behind this contribution, would add further insights into the mechanisms of actions for "gepants", which may be pivotal for the effectiveness of these drugs as anti-migraine agents. CSD models are useful tools for testing current and novel prophylactic drugs, providing knowledge on mechanisms of action relevant for migraine.