Effects of alniditan on neurogenic oedema in the rat dura mater and on contraction of rat basilar artery

Vasoconstrictor 5-HT receptors in the smooth muscle of the rat middle cerebral artery

Serotonin (5-HT) can constrict cerebral arteries via activation of 5-HT(1B) and 5-HT(2A) receptors. Our goal was to reveal the importance and relative contribution of the two 5-HT receptor subtypes to the serotonin-induced vasoconstriction in the rat middle cerebral artery. The vasoconstrictor effects of 5-carboxamidotryptamine, sumatriptan and 5-HT were measured without and with pre-treatment with SB 216641 (5-HT(1B) antagonist), or ritanserin, (5-HT(2A) antagonist), in endothelium-denuded arteries, in vitro. All agonists caused vasoconstrictions. The order of potency (EC(50)) of the compounds was: 5-carboxamidotryptamine (14±3 nM)>5-HT (270±30 nM)>sumatriptan (5.8±1.9 μM). The concentration-response curve of 5-carboxamidotryptamine resembled the sum of two sigmoid curves (EC(50) 14±3 nM and 15±7 μM), and SB 216641 and ritanserin antagonized its low and high concentration components, respectively. Vasoconstrictions evoked by 5-HT at low and high concentrations were also fully antagonized by SB 216641 and ritanserin, respectively. Sumatriptan constricted the middle cerebral artery exclusively via 5-HT(1B) receptors. The efficacy of 5-carboxamidotryptamine and sumatriptan was low in comparison to the maximum contractile force elicited by 120 mmol/l KCl, reaching only 18-23% for 5-HT(1B) and 14% for 5-HT(2A) receptor activation. In conclusion, 5-HT produced small vasoconstrictions in the rat middle cerebral artery that were mediated by 5-HT(1B) receptors with high potency and by 5-HT(2A) receptors with low potency. Thus, 5-HT may have a minor physiological role in blood flow regulation via 5-HT(1B) receptor activation while 5-HT(2A) receptors seem to have a pathophysiological role in this vessel.

The efficacy and safety of sc alniditan vs. sc sumatriptan in the acute treatment of migraine: a randomized, double-blind, placebo-controlled trial

This double-blind, placebo-controlled, parallel-group, multicentre, multinational, phase-III trial was designed to assess the efficacy and safety of a single subcutaneous injection of placebo, 2 doses of alniditan (1.4 mg and 1.8 mg) and 6 mg of sumatriptan in subjects with acute migraine. A total of 114 investigators from 13 different countries screened 2021 subjects. In total 924 patients were treated with placebo (157), alniditan 1.4 mg (309), alniditan 1.8 mg (141) and sumatriptan 6 mg (317). The lower number of subjects in the alniditan 1.8 mg group is due to the termination of this trial arm after the incidence of a serious adverse event and a subsequent protocol amendment. The number of subjects who were pain free at 2 h (primary endpoint) was: 22 (14.1%) with placebo, 174 (56.3%) with alniditan 1.4 mg, 87 (61.7%) with alnditan 1.8 mg and 209 (65.9%) with sumatriptan 6 mg. Alniditan 1.4 mg was significantly better (P < 0.001) than placebo and sumatriptan was significantly better (P = 0.015) than alniditan 1.4 mg. The number of responders (reduction of headache severity from moderate or severe headache before treatment to mild or absent at 2 h), was 59 (37.8%) on placebo, 250 (80.9%) on alniditan 1.4 mg, 120 (85.1%) on alniditan 1.8 mg, and 276 (87.1%) on sumatriptan. Response was significantly higher (P < 0.001) with alniditan 1.4 mg than with placebo, and significantly lower (P = 0.036) with alniditan 1.4 mg than with sumatriptan. Recurrence rates were: 22 (37.3%) with placebo, 87 (34.8%) with alniditan 1.4 mg, 35 (29.2%) with alniditan 1.8 mg and 108 (39.1%) with sumatriptan. Adverse events occurred in 577/924 (62.4%) subjects, i.e. in 62/157 (39.5%) with placebo, 214/309 (69.3%) with alniditan 1.4 mg, 91/141 (64.5%) with alniditan 1.8 mg and 210/317 (66.2%) with sumatriptan 6 mg. Sumatriptan was significantly better than alniditan 1.4 mg for pain free at 2 h. The difference, however, was small and clinically not important. For alniditan, a dose-dependent adverse event relationship was seen. The safety profile of alniditan 1.4 mg was similar to that of sumatriptan.

Pharmacological opportunities and pitfalls in the therapy of migraine

The mild vasoconstrictor effects of modern antimigraine drugs, such as serotonin (5-HT; 5-hydroxytryptamine)1B/D agonists, have led to a search for nonvasoconstrictor approaches to therapy. Such approaches have included substance P (neurokinin I) antagonists, endothelin antagonists and highly specific 5HT1D agonists. All of these substances are effective in animal models and have no significant vasoconstrictive effects. However, all of them failed to demonstrate any antimigraine effects. Current clinical and experimental evidence therefore supports the view that isolated peripheral trigeminal nerve inhibition is insufficient to relieve acute migraine.

An in vivo rat model to study calcitonin gene related peptide release following activation of the trigeminal vascular system

Calcitonin gene related peptide (CGRP) released from the C-fibers projecting from the trigeminal ganglion to the meninges has been suggested to play a crucial role in the pathophysiology of headache, particularly migraine. In humans it has been shown that CGRP is released during migraine-attacks, and this is attenuated by the administration of typical anti-migraine drugs such as dihydroergotamine or sumatriptan. We describe a new rat model which allows the study of CGRP release from the meninges into venous blood following activation of the trigeminal vascular system. The effects of classical and new anti-migraine drugs such as acetylsalicylic acid (ASA), sumatriptan and the new high efficacy 5-HT1B/1D agonist donitriptan (4-[4-[2-(2-aminoethyl)-1H-indol-5-yloxyl]acetyl]piperazinyl-1-yl]benzonitrile) were evaluated in comparison with the established model of neurogenic inflammation in the meninges. Sumatriptan and donitriptan inhibited CGRP release as well as neurogenic inflammation. ASA, however, attenuated neurogenic inflammation, but not CGRP release, confirming the concept of prejunctional inhibition of CGRP release by 5-HT1B/1D receptors. This new model allows the further study of prejunctional pharmacology and mechanisms of neuropeptide release in the trigeminal vascular system, which might be crucial for the further development of potent, more effective anti-migraine drugs.

Treatment of migraine attacks with intranasal alniditan: an open study

In this open phase-II clinical tolerability trial 17 neurologists enrolled a total of 112 patients and instructed them to administer a maximum of two doses of intranasal alniditan, a 5-HT1B/D receptor agonist, for the treatment of three consecutive migraine attacks of moderate to severe intensity. A second dose of the trial medication was allowed within 1-24 h after the first administration. At 1 h after intranasal administration, 70/103 (68%) patients had responded to treatment (reduction from severe or moderate headache before treatment to mild or no headache) after their first migraine attack, 65/94 (69%) after their second and 52/75 (71%) after their third. In 187/270 (69%) of all attacks, patients were considered responders at 1 h. The median time to onset of effect was 30 min. The migraine headache recurred in 44% (attack 1), 55% (attack 2) and 44% (attack 3) after 4-5 h. Sixty-eight per cent of the patients reported nasal irritation, 19% taste disturbance and 44% throat irritation. Alniditan 2 mg, administered via the intranasal route, was effective in relieving migraine headaches in over two-thirds of the patients at 1 h.

Acute treatments: some blind alleys

The introduction of sumatriptan, a selective 5-HT(1B/1D) agonist, for the treatment of migraine sparked a new era of drug research in this field. Many novel targets have since been developed, and tested in the clinic. The promise of these approaches is to deliver an anti-migraine compound with the optimal efficacy and safety profile. In this chapter, blind alleys in anti-migraine development are discussed. The failing soldiers have included the NK-1 antagonists, some second-generation 5-HT(1B/1D) agonists, CP-122,288, 4991W93, the neurosteroid ganaxolone, selective 5-HT(1F) (LY334370) and 5-HT(1D) agonists (PNU-142,633), and the endothelin-1 antagonist bosentan. Some of these promising targets failed to demonstrate clinical efficacy, while others were stopped for preclinical toxicity.