5-HT1F Receptor Research Articles

Human Beta Cells Produce and Release Serotonin to Inhibit Glucagon Secretion from Alpha Cells

In the pancreatic islet, serotonin is an autocrine signal increasing beta cell mass during metabolic challenges such as those associated with pregnancy or high-fat diet. It is still unclear whether serotonin is relevant for regular islet physiology and hormone secretion. Here, we show that human beta cells produce and secrete serotonin when stimulated with increases in glucose concentration. Serotonin secretion from beta cells decreases cyclic AMP (cAMP) levels in neighboring alpha cells via 5-HT1F receptors and inhibits glucagon secretion. Without serotonergic input, alpha cells lose their ability to regulate glucagon secretion in response to changes in glucose concentration, suggesting that diminished serotonergic control of alpha cells can cause glucose blindness and the uncontrolled glucagon secretion associated with diabetes. Supporting this model, pharmacological activation of 5-HT1F receptors reduces glucagon secretion and has hypoglycemic effects in diabetic mice. Thus, modulation of serotonin signaling in the islet represents a drug intervention opportunity.

Distribution of 5-HT1F Receptors in Monkey Vestibular and Trigeminal Ganglion Cells.

Evidence of serotonergic involvement in vestibular pathway contributions to migraine and balance disorders is compelling. Serotonergic 5-HT1B and 5-HT1D receptors are expressed extensively in inner ear ganglia of monkeys and rats. The serotonergic 5-HT1F receptor is also a target of triptans. This study describes its distribution in vestibular and trigeminal ganglia of monkeys. Using primary polyclonal antibodies raised against oligopeptides specific for the human 5-HT1F receptor, neuronal somatic area and intensity of immunoreactive vestibular and trigeminal ganglia were quantified. Virtually all vestibular and considerable trigeminal ganglia showed positive 5-HT1F receptor immunoreactivity. Inferior and superior vestibular ganglia staining appeared confined to distinct cell regions, varying considerably among cells of different sizes: more intense in small, punctate in some medium and regionally polarized in some large cells. Analyses of average somatic vestibular neuronal immunoreactive intensity identified mainly medium sized cells with high standard deviation of intensity corresponding to punctately stained cells. Less variability occurred in somatic intensity staining and cellular distribution among 5-HT1F receptor immunopositive trigeminal ganglia. Most exhibited similar punctate staining patterns, higher mean somatic immunoreactive intensity and larger neuronal somatic size proportions per size distribution subpopulation compared to vestibular ganglia size distribution populations. Centrally directed vestibular ganglion neuronal processes, cochlear inner hair cells, vestibular hair cells and blood vessels in vestibular maculae and cristae were immunoreactive. The 5-HT1F receptor expression in vestibular ganglia shows complex variable staining intensity patterns associated with cell size of immunopositive neurons, not seen in immunopositive trigeminal ganglia and not previously evident with 5-HT1B and 5-HT1D receptor subtype immunoreactivity in vestibular ganglia. These data motivate exploration of 5-HT1 receptor oligomerization and ligand functional selectivity in differential serotonergic involvement in co-morbidity of migraine and balance disorders. Similar findings in cochlear inner hair cell afferents are applicable to migraine-related tinnitus or hypercusis (phonophobia).

Recent advances in migraine therapy.

Migraine is a common and highly disabling neurological disorder associated with a high socioeconomic burden. Effective migraine management depends on adequate patient education: to avoid unrealistic expectations, the condition must be carefully explained to the patient soon as it is diagnosed. The range of available acute treatments has increased over time. At present, abortive migraine therapy can be classed as specific (ergot derivatives and triptans) or non-specific (analgesics and non-steroidal anti-inflammatory drugs). Even though acute symptomatic therapy can be optimised, migraine continues to be a chronic and potentially progressive condition. In addition to the drugs officially approved for migraine prevention by international governmental regulatory agencies, numerous different agents are commonly used for this indication, showing various levels of evidence of efficacy and tolerability. Guidelines published in recent years, based on evidence-based medicine data on migraine prophylaxis, are a useful source of guidance, especially for primary care physicians and neurologists without specific expertise in headache medicine. Although the field of pharmacological migraine prevention has seen few advances in recent years, potential novel approaches are now being developed. This review looks at emerging pharmacological strategies for acute and preventive migraine treatment that are nearing or have already entered the clinical trial phase. Specifically, it discusses preclinical and clinical data on compounds acting on calcitonin gene-related peptide or its receptor, the serotonin 5-HT1F receptor, nitric oxide synthase, and acid-sensing ion channel blockers.

A subpopulation of itch-sensing neurons marked byRet and somatostatin expression.

Itch, the unpleasant sensation that elicits a desire to scratch, is mediated by specific subtypes of cutaneous sensory neuron. Here, we identify a subpopulation of itch-sensing neurons based on their expression of the receptor tyrosine kinase Ret. We apply flow cytometry to isolate Ret-positive neurons from dorsal root ganglia and detected a distinct population marked by low levels of Ret and absence of isolectin B4 binding. We determine the transcriptional profile of these neurons and demonstrate that they express neuropeptides such as somatostatin (Sst), the NGF receptor TrkA, and multiple transcripts associated with itch. We validate the selective expression of Sst using an Sst-Cre driver line and ablated these neurons by generating mice in which the diphtheria toxin receptor is conditionally expressed from the sensory neuron-specific Avil locus. Sst-Cre::Avil(iDTR) mice display normal nociceptive responses to thermal and mechanical stimuli. However, scratching behavior evoked by interleukin-31 (IL-31) or agonist at the 5HT1F receptor is significantly reduced. Our data provide a molecular signature for a subpopulation of neurons activated by multiple pruritogens.

P.1.015 Surface-based clustering of serotonergic and adrenergic receptor mRNA expression in the human cortex

Serotonin (5-hydroxytryptamine, 5-HT) has been shown to play a role in immunoregulation; however, little is known about specific subtypes of 5-HT receptors involved in peripheral immunomodulation. In the present study we used RT-PCR methods to examine the mRNA expression of 5-HT receptors in the cells of lymphoid tissues of the rat. All 13 rat 5-HT receptor genes cloned so far were examined in ex vivo isolated spleen, thymus, and peripheral blood lymphocytes, as well as in mitogen-stimulated spleen cells. Positive signals were obtained for 5-HT1B, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT6, and 5-HT7 receptor mRNAs in all three compartments. Mitogen (ConA and PWM) stimulated cells additionally expressed mRNA corresponding to the 5HT-3 receptor subtype. In contrast, 5-HT1A, 5-HT1D, 5-HT2C, 5-HT4, 5-HT5A, and 5-HT5B mRNAs were not detected in any of the examined cell populations. These results may be useful as a starting point for future functional studies on immunomodulatory effects of 5-HT and may help to understand conflicting serotonergic effects on immune functions as found in the literature.

The role of triptans in the management of migraine

Migraine is one of the most prevalent disorders seen in clinical practice today and also a major cause of disability in the workplace. The prevalence of migraine is highest during the years of peak productivity, ie, between the ages of 25 and 55 years. The triptans are a group of selective 5-hydroxtriptamine (HT)1 serotonin receptor agonists that activate the 5-HT1B/1D receptor and possibly also the 5-HT1A dan 5-HT1F receptors. To date 7 subclasses of serotonin receptors have been identified, namely subclasses 5-HT1 to 5-HT7. Triptan causes cranial vasoconstriction, inhibits peripheral trigeminal activity and the trigeminal afferents. With its triple action, triptans can control acute attacks of migraine. Triptan is contraindicated in patients with previous ischemic or coronary artery disease, cerebral or peripheral vascular disease and other cardiovascular disorders. Triptans should be given immediately after an acute attack of migraine. The triptans are useful in the management of an acute migraine, but are not indicated for preventive therapy of migraine. Several new advances in migraine management have been made in regard to the recognition of the disease, the pathogenesis of migraine, and the phenomenon of central sensitization. More treatment options become available to patients and prescribers, the impact of such therapy on worker productivity will become more important in determining the value of such interventions.

Discovery of selective N-[3-(1-methyl-piperidine-4-carbonyl)-phenyl]-benzamide-based 5-HT₁ F receptor agonists: Evolution from bicyclic to monocyclic cores.

Preclinical experiments and clinical observations suggest the potential effectiveness of selective 5-HT1F receptor agonists in migraine. Identifying compounds with enhanced selectivity is crucial to assess its therapeutic value. Replacement of the indole nucleus in 2 (LY334370) with a monocyclic phenyl ketone moiety generated potent and more selective 5-HT1F receptor agonists. Focused SAR studies around this central phenyl ring demonstrated that the electrostatic and steric interactions of the substituent with both the amide CONH group and the ketone CO group play pivotal roles in affecting the adopted conformation and thus the 5-HT1F receptor selectivity. Computational studies confirmed the observed results and provide a useful tool in the understanding of the conformational requirements for 5-HT1F receptor agonist activity and selectivity. Through this effort, the 2-F-phenyl and N-2-pyridyl series were also identified as potent and selective 5-HT1F receptor agonists.

Emerging treatments for the primary headache disorders.

Migraine and cluster headache are common, episodic, often chronic and disabling disorders of the brain. Although there are many standard treatment techniques, none are ideal. This article reviews various novel pharmacologic and device-related treatments for migraine and cluster headache. Emphasis is given to recent advances in the development of monoclonal antibodies (mAbs) targeting calcitonin gene-related peptide (CGRP) and its receptor, including promising results from phase 2 trials studying the safety and efficacy of LY2951742, ALD403 and TEV-48125, three anti-CGRP mAbs. Other new pharmacologic treatments discussed include the 5-HT1F receptor agonist lasmiditan and glial cell modulator ibudilast. Also reviewed is neuromodulation for migraine and cluster headache, including promising recent results of randomized controlled trials studying sphenopalatine ganglion stimulation, trigeminal nerve stimulation, transcutaneous vagus nerve stimulation, and transcranial magnetic stimulation. Finally, we discuss patch, inhaled, and intranasal methods of triptan and dihydroergotamine delivery.

Serotonin-mediated modulation of hypoxia-induced intracellular calcium responses in glomus cells isolated from rat carotid body

In the present study, we examined serotonin (5-HT)-induced intracellular Ca2+ ([Ca2+]i) responses to hypoxia in glomus cells isolated from carotid body (CB) of the rat. 5-HT did not induce any [Ca2+]i responses in clustered glomus cells during normoxia (21% O2), whereas, the perfusion of hypoxic solution (1% O2) induced repetitive increases in [Ca2+]i in the same specimens. The frequency and magnitude of hypoxia-induced [Ca2+]i changes observed in the glomus cells were enhanced in the presence of 5-HT, and this response was inhibited by the 5-HT2 receptor antagonist, ketanserin. Furthermore, RT-PCR analysis detected the expression of 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT3A, and 5-HT3B receptor mRNAs in extracts of the CB. These results suggest that 5-HT increases hypoxia-induced [Ca2+]i responses in glomus cells. 5-HT may elevate hypoxic responses in glomus cells in order to increase chemosensory activity of the CB.

The pharmacological profile and clinical prospects of the oral 5-HT1F receptor agonist lasmiditan in the acute treatment of migraine.

More than 20 years have passed without the launch of a new substance class for acute migraine therapy. Triptans were the latest class of substances which successfully passed all developmental stages with a significant antimigraine efficacy and a sufficient safety profile. New drugs with a better adverse event profile and at least similar efficacy are needed for migraine subjects who cannot tolerate triptans for attack treatment. Lasmiditan is a novel highly specific 5-HT1F receptor agonist currently in clinical trials for acute migraine therapy and devoid of vasoconstriction in coronary arteries as determined in a surrogate assay. In both phase II randomized, placebo-controlled trials in acute migraine the primary endpoint was met. For the intravenous formulation a clear dose-dependent effect on headaches could be determined. Lasmiditan tablets in doses of 50-400 mg show significant headache relief after 2 hours compared with placebo and improved accompanying symptoms. This substance is chemically clearly different from other antimigraine drugs, which is also reflected by its dose-dependent adverse event profile chiefly including dizziness, vertigo, paresthesia and fatigue. Adverse events are usually linked to the central nervous system. Future phase III clinical trials with an active triptan comparator or in a preferential trial design will allow a better comparison of lasmiditan and triptans. They will also determine whether lasmiditan will become available to the migraine patient.

Serotonin receptor expression is dynamic in the liver during the transition period in Holstein dairy cows

Nonneuronal serotonin (5-HT) participates in glucose metabolism, but little is known regarding the actions of 5-HT in the liver during the transition period in dairy cattle. Here, we explore circulating patterns of 5-HT and characterize the hepatic 5-HT receptor and glucose transporter profiles around calving in multiparous Holstein dairy cows (n = 6, average lactation = 4 ± 1.9). Concentrations of serum 5-HT decreased on day −3 compared with −5 and −7 precalving (167.7 ± 80 vs 1511.1 ± 602 ng/mL). 5-HT nadir was on day −1 precalving and remained low postcalving (481.4 ± 49 ng/mL). Plasma glucose concentrations decreased precalving (P = 0.008) and were positively correlated with 5-HT during the precalving period (r = 0.55, P = 0.043). On day 1, postcalving hepatic messenger RNA expression of 5-HT1D, 2B, 3C, 6, and7 receptors were decreased compared with day −7 (P < 0.048). The 5-HT3A and 5-HT3B decreased on day 7. The 5-HT2A increased on days 1 and 7 compared with −7 (P < 0.05). The 5-HT1F and 5-HT1A receptors were increased 2.5- and 3.8-fold on day 7, respectively, compared with days −7 and 1 (P < 0.046). The 5-HT5A was not detected, and 5-HT4 was detected on days −7 and 1 only. Expression of Glut-2,-5 and SGLT1 were decreased on days 1 and 7 compared with −7 (P < 0.05), whereas Glut-1 was increased on day 7 compared with −7 (P < 0.05). These results indicate that 5-HT could be important for liver glucose homeostasis possibly through receptor mediated signaling at specific times. Additional research is needed to further explore the functional role of these receptors in the liver during the transition from pregnancy to lactation.

New targets for migraine therapy.

The shift in our understanding of migraine as a vascular disorder to a brain disorder has opened new avenues for the development of novel therapeutics with neural targets. The advent of 5-HT1B/1D receptor agonists, the triptans, in the 1990s was a crucial step in the modern evolution of treatment. The use of triptans, like their predecessors, is limited by their vasoconstrictor effects, and new development has been slowed by poor academic research funding to identify new targets. The development of agents without vascular effects, such as calcitonin gene-related peptide receptor antagonists and selective serotonin 5-HT1F receptor agonists, will bring more effective treatments to a population currently without migraine-specific options. In addition, advances in understanding migraine pathophysiology have identified new potential pharmacologic targets such as acid-sensing ion channels, glutamate and orexin receptors, nitric oxide synthase (NOS), and transient receptor potential (TRP) channels. Although previous attempts to block subtypes of glutamate receptors, NOS, and TRP channels have had mixed outcomes, new molecules for the same targets are currently under investigation. Finally, an entirely new approach to migraine treatment with noninvasive neuromodulation via transcutaneous neurostimulation or transcranial magnetic stimulation is just beginning. Hopefully in the coming years we will see a new era of migraine therapy, with multiple classes of better-tolerated, more effective agents targeting diverse yet specific migraine mechanisms.

Agonism of the 5-hydroxytryptamine 1F receptor promotes mitochondrial biogenesis and recovery from acute kidney injury.

Many acute and chronic conditions, such as acute kidney injury, chronic kidney disease, heart failure, and liver disease, involve mitochondrial dysfunction. Although we have provided evidence that drug-induced stimulation of mitochondrial biogenesis (MB) accelerates mitochondrial and cellular repair, leading to recovery of organ function, only a limited number of chemicals have been identified that induce MB. The goal of this study was to assess the role of the 5-hydroxytryptamine 1F (5-HT1F) receptor in MB. Immunoblot and quantitative polymerase chain reaction analyses revealed 5-HT1F receptor expression in renal proximal tubule cells (RPTC). A MB screening assay demonstrated that two selective 5-HT1F receptor agonists, LY334370 (4-fluoro-N-[3-(1-methyl-4-piperidinyl)-1H-indol-5-yl]benzamide) and LY344864 (N-[(3R)-3-(dimethylamino)-2,3,4,9-tetrahydro-1H-carbazol-6-yl]-4-fluorobenzamide; 1-100 nM) increased carbonylcyanide-p-trifluoromethoxyphenylhydrazone-uncoupled oxygen consumption in RPTC, and validation studies confirmed both agonists increased mitochondrial proteins [e.g., ATP synthase β, cytochrome c oxidase 1 (Cox1), and NADH dehydrogenase (ubiquinone) 1β subcomplex subunit 8 (NDUFB8)] in vitro. Small interfering RNA knockdown of the 5-HT1F receptor blocked agonist-induced MB. Furthermore, LY344864 increased peroxisome proliferator-activated receptor coactivator 1-α, Cox1, and NDUFB8 transcript levels and mitochondrial DNA (mtDNA) copy number in murine renal cortex, heart, and liver. Finally, LY344864 accelerated recovery of renal function, as indicated by decreased blood urea nitrogen and kidney injury molecule 1 and increased mtDNA copy number following ischemia/reperfusion-induced acute kidney injury (AKI). In summary, these studies reveal that the 5-HT1F receptor is linked to MB, 5-HT1F receptor agonism promotes MB in vitro and in vivo, and 5-HT1F receptor agonism promotes recovery from AKI injury. Induction of MB through 5-HT1F receptor agonism represents a new target and approach to treat mitochondrial organ dysfunction.

Emerging therapeutic options for acute migraine: focus on the potential of lasmiditan.

The serotonin receptor agonist triptan drugs (5-HT1B/1D receptor agonists) have been in use for over 20 years in the abortive management of migraine. Although clearly effective, their ability to produce vasoconstriction in cerebral and coronary arteries, thought to be mediated by their high affinity for the 5-HT1B receptor, has been a limitation to their use in certain patient populations. Variable potency triptan binding at the 5-HT1F receptor occurs in addition to binding at the 5-HT1B and 5-HT1D receptors. A more selective serotonin agonist without 5-HT1B-mediated vasoconstriction might prove efficacious yet safer. The 5-HT1F receptor has been targeted as a site of action for such a drug. In experimental models, 5-HT1F receptor agonists have been shown to block neurogenic inflammation and c-Fos expression in neural tissue and, as well, show no evidence of vasoconstriction in vascular tissue models in vitro. In clinical trials, efficacy in the abortive management of migraine has been established. Lasmiditan (LY573144), a selective 5-HT1F receptor agonist (K1=2.21 μM), showed efficacy in its primary endpoint, with a 2-hour placebo-subtracted headache response of 28.8%, though with frequent reports of dizziness, paresthesias, and vertigo. Study results support an emerging central neuronal mechanism of migraine pathophysiology. This review traces the history and use of 5-HT1F receptor agonists, now referred to as neurally acting anti-migraine agents in migraine management.

P.2.d.020 The effectiveness of asenapine in clinical practice: the EXPASEN study

The reverse transcriptase polymerase chain reaction (RT-PCR) technique was used to examine the changes of the expression of 5-hydroxytryptamine (5-HT) receptors in the rat lumbar dorsal root ganglion (DRG) following subcutaneous bee venom (BV) injection into the plantar surface of the unilateral hindpaw. In the DRG ipsilateral to the BV injection, significant increase of mRNA levels of 5-HT1A, 5-HT1B, 5-HT2A and 5-HT3 receptor subtypes were observed at 1 and 4 h after the BV injection, while increase of 5-HT2C, 5-HT4, 5-HT6 and 5-HT7 receptor subtype mRNAs was detected at 4 h only. No such changes were observed in the expressions of 5-HT1D, 5-HT1F and 5-HT5A receptor subtype mRNAs. Upregulation of 5-HT1A, 5-HT1B and 5-HT2A receptor subtype mRNAs was also observed in the contralateral DRG at 4 h. The presence of 5-HT1E, 5-HT2B and 5-HT5B receptor subtype mRNAs was not detected in the rat DRG. The present results suggest that different sets of 5-HT receptor subtypes work at different stages of the inflammatory pain induced by subcutaneous BV injection.

The Pipeline in Headache Therapy

Migraine is a common, disabling, neurovascular disorder characterized by episodic attacks of head pain and associated disability plus systemic autonomic and neurologic symptoms. The advent of the triptan class of medication in the 1990s revolutionized the acute treatment of migraine, but many migraineurs do not respond optimally or at all to triptans, have intolerable adverse effects, or have contraindications to their use. Preventive pharmacotherapy has advanced mostly through serendipity, with new drugs being found effective while being used for other indications. There remains a significant need for new medications and devices that can provide effective, rapid, and sustained pain relief without adverse effects or recurrence. Several new acute and preventive therapies for the treatment of migraine and cluster headaches have shown promise and are currently under investigation. This article covers innovative delivery mechanisms, calcitonin gene-related peptide receptor antagonists, antibodies to calcitonin gene-related peptide and its receptor, 5-HT1F receptor agonists, transient receptor potential vanilloid receptor modulators, orexin receptor antagonists, glial cell modulators, and neurostimulation.

What's new in the migraine attack treatment

This short review aims to give a focus on news in the migraine attack treatment and discusses the CGRP receptor antagonists (gepants), the 5-HT1F receptors agonists (ditans), the transcranial magnetic stimulation for the treatment of migraine attack with aura, innovative delivery systems for sumatriptan and the oral inhalation of dihydroergotamine.

Emerging Target-Based Paradigms to Prevent and Treat Migraine

Migraine is a primary brain disorder resulting from altered modulation of normal sensory stimuli and trigeminal nerve dysfunction. The second edition of the International Classification of Headache Disorders (ICHD-2) defines seven subtypes of migraine. Migraine treatment can be acute or preventive. New targeted therapies include 5-HT(1F) receptor agonists, calcitonin gene-related peptide (CGRP) antagonists, nitric oxide synthetase inhibitors, and ion channel antagonists. A recent development is the creation of antibodies to CGRP and its receptor for migraine prevention.

Targeting to 5-HT1F Receptor Subtype for Migraine Treatment: Lessons from the Past, Implications for the Future

The effective anti-migraine drugs triptans, all bind with high affinity to three serotonin (5-HT) subtypes, the 5-HT1B, 5-HT1D and 5-HT1F. 5-HT1B mRNA is densely localized within smooth muscle, and less in the endothelium of cerebral blood vessels. This vascular distribution of 5-HT1B receptor has been shown to mediate the vasoconstrictive properties of the triptans, responsible for potential cardiac adverse events. Activation of 5-HT1D subtype, although effective in animal models of migraine, was not enough efficient to attenuate migraine attacks in clinical trials. The 5-HT1F receptor is located both in vessels and within the trigeminal ganglion (TG) and the trigeminal nucleus caudalis (Sp5C), but with the difference that the 5-HT1F receptor lack vasoconstrictive properties, making it an attractive target for new anti-migraine drugs. Selective activation of 5-HT1F receptor potently inhibited markers associated with electrical stimulation of the TG. Thus 5-HT1F receptor represents an ideal target for anti-migraine drugs. So far two selective 5-HT1F agonists have been tested in human trials for migraine: LY334370 and lasmiditan. Both molecules were efficient in attenuating migraine attacks with efficacy in the same range as oral sumatriptan 100mg, the gold standard for triptans. The LY334370 project withdrew because of toxicity in animals, while lasmiditan is still testing. In this review we present all the available preclinical and clinical data on the 5-HT1F agonists as a potential new class of anti-migraine drugs lacking vascular activity and we discuss related issues on the vascular and neuronal aspects of migraine pathogenesis.

Efficacy and tolerability of lasmiditan, an oral 5-HT1F receptor agonist, for the acute treatment of migraine: a phase 2 randomised, placebo-controlled, parallel-group, dose-ranging study

Lasmiditan (COL-144) is a novel, centrally acting, highly selective 5-HT(1F) receptor agonist without vasoconstrictor activity that seemed effective when given as an intravenous infusion in a proof-of-concept migraine study. We aimed to assess the efficacy and safety of oral lasmiditan for the acute treatment of migraine. In this multicentre, double-blind, parallel-group, dose-ranging study in 43 headache centres in five European countries, patients with migraine with and without aura and who were not using prophylaxis were randomly assigned (1:1:1:1:1) to treat one moderate or severe attack at home with 50 mg, 100 mg, 200 mg, or 400 mg lasmiditan, or placebo. Study drug and placebo were supplied in identical numbered tablet packs. The randomisation code was generated by an independent statistician. Patients and investigators were masked to treatment allocation. The primary endpoint was dose response for headache relief (moderate or severe becoming mild or none) at 2 h. The primary analysis was done in the modified intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT00883051. Between July 8 2009, and Feb 18, 2010, 512 patients were randomly assigned to treatment, 391 of whom received treatment. 86 patients received placebo (81 included in primary analysis) and 305 received lasmiditan (50 mg n=79, 100 mg n=81, 200 mg n=69, and 400 mg n=68 included in primary analysis). There was a linear association between headache response rate at 2 h and lasmiditan dose (Cochran-Armitage test p<0·0001). Every lasmiditan treatment dose significantly improved headache response at 2 h compared with placebo (lasmiditan 50 mg: difference 17·9%, 95% CI 3·9-32·1, p=0·022; 100 mg: 38·2%, 24·1-52·4, p<0·0001; 200 mg: 28·8%, 9·6-39·9, p=0·0018; 400 mg: 38·7%, 23·9-53·6, p<0·0001). The proportion of patients with treatment-emergent adverse events increased with increasing doses (53/82 [65%], 59/82 [72%], 61/71 [86%], and 59/70 [84%] for lasmiditan 50, 100, 200, and 400 mg, respectively vs 19/86 [22%] for placebo). Most adverse events were mild or moderate in intensity, with 16 of 82 (20%), 23 of 82 (28%), 28 of 71 (39%), and 31 of 70 (44%) of patients on lasmiditan 50, 100, 200, and 400 mg, respectively reporting a severe adverse event compared with five of 86 (6%) on placebo. The most common adverse events were CNS related and included dizziness, fatigue, vertigo, paraesthesia, and somnolence. Oral lasmiditan seems to be safe and effective in the acute treatment of migraine. Further assessment in larger placebo-controlled and triptan-controlled trials are needed to assess the potential role of lasmiditan in acute migraine therapy. CoLucid Pharmaceuticals.