The Pharmacokinetics, Safety, and Tolerability of Rimegepant 75 mg Are Similar in Elderly and Nonelderly Adults: A Phase 1, Open-Label, Parallel-Group, Single-Dose Study

Rimegepant is a small-molecule calcitonin gene-related peptide receptor antagonist approved for the acute treatment of migraine ± aura and preventive treatment of migraine in adults. The pharmacokinetics of rimegepant in elderly and nonelderly subjects were evaluated. In an open-label Phase 1 study, 14 elderly (aged 65 years or older) and 14 nonelderly (aged 18 to less than 45 years) subjects each received a single oral dose of rimegepant 75 mg. Blood samples were collected before dosing and through 96 hours after dosing. The pharmacokinetic parameters of rimegepant after a single dose were similar in both age groups. Geometric least-squares mean ratios (elderly/nonelderly) of the natural log-transformed maximum observed plasma concentration and natural log-transformed area under the plasma concentration-time curve from time 0 extrapolated to infinity were 96.6 and 104.6, respectively. Eight (28.6%) subjects (4 elderly, 4 nonelderly) experienced 1 or more adverse events (AEs); all AEs were mild in intensity, and no serious AEs or AEs leading to discontinuation were reported. Following a single 75-mg dose of oral rimegepant, pharmacokinetic parameters were similar in elderly and nonelderly adults; no dose adjustment is warranted in elderly subjects.

Calcitonin Gene-Related Peptide (CGRP)-Targeted Monoclonal Antibodies and Antagonists in Migraine: Current Evidence and Rationale

Calcitonin gene-related peptide (CGRP), a 37 amino-acid neuropeptide found mostly in peptidergic sensory C-fibers, has been suggested to be implicated in the pathogenesis of migraine, which is one of the most common neurological disorders seen in medical practice, affecting almost 16% of the US population. While previously thought to be a vascular condition, migraine attacks are the result of neurogenic inflammation and peripheral/central sensitization through dysfunctional activation of the trigeminovascular system. To date, two classes of therapeutic agents have been developed to interrupt the function of CGRP: CGRP-targeted monoclonal antibodies (mAbs) and small-molecule antagonists (gepants). There are currently four CGRP-targeted mAbs and three gepants that are US Food and Drug Administration (FDA) approved for the treatment of migraine. Multiple phase II and III studies have established the efficacies and tolerability of these treatments. Previously, we reviewed the fundamental role of CGRP in migraine pathogenesis. Here, we discuss in depth the clinical evidence (randomized controlled trials and real-world studies), safety, and tolerability of CGRP-targeted mAbs and gepants for treating migraine.

Use of a Bile Salt Export Pump Knockdown Rat Susceptibility Model to Interrogate Mechanism of Drug-Induced Liver Toxicity

Inhibition of the bile salt export pump (BSEP) may be associated with clinical drug-induced liver injury, but is poorly predicted by preclinical animal models. Here we present the development of a novel rat model using siRNA knockdown (KD) of Bsep that displayed differentially enhanced hepatotoxicity to 8 Bsep inhibitors and not to 3 Bsep noninhibitors when administered at maximally tolerated doses for 7 days. Bsep KD alone resulted in 3- and 4.5-fold increases in liver and plasma levels, respectively, of the sum of the 3 most prevalent taurine conjugated bile acids (T3-BA), approximately 90% decrease in plasma and liver glycocholic acid, and a distinct bile acid regulating gene expression pattern, without resulting in hepatotoxicity. Among the Bsep inhibitors, only asunaprevir and TAK-875 resulted in serum transaminase and total bilirubin increases associated with increases in plasma T3-BA that were enhanced by Bsep KD. Benzbromarone, lopinavir, and simeprevir caused smaller increases in plasma T3-BA, but did not result in hepatotoxicity in Bsep KD rats. Bosentan, cyclosporine A, and ritonavir, however, showed no enhancement of T3-BA in plasma in Bsep KD rats, as well as Bsep noninhibitors acetaminophen, MK-0974, or clarithromycin. T3-BA findings were further strengthened through monitoring TCA-d4 converted from cholic acid-d4 overcoming interanimal variability in endogenous bile acids. Bsep KD also altered liver and/or plasma levels of asunaprevir, TAK-875, TAK-875 acyl-glucuronide, benzbromarone, and bosentan. The Bsep KD rat model has revealed differences in the effects on bile acid homeostasis among Bsep inhibitors that can best be monitored using measures of T3-BA and TCA-d4 in plasma. However, the phenotype caused by Bsep inhibition is complex due to the involvement of several compensatory mechanisms.

Blocking the CGRP Pathway for Acute and Preventive Treatment of Migraine: The Evolution of Success

The pivotal role of calcitonin gene-related peptide (CGRP) in migraine pathophysiology was identified over 30 years ago, but the successful clinical development of targeted therapies has only recently been realized. This Perspective traces the decades long evolution of medicinal chemistry required to advance small molecule CGRP receptor antagonists, also called gepants, including the current clinical agents rimegepant, vazegepant, ubrogepant, and atogepant. Providing clinically effective blockade of CGRP signaling required surmounting multiple challenging hurdles, including defeating a sizable ligand with subnanomolar affinity for its receptor, designing antagonists with an extended confirmation and multiple pharmacophores while retaining solubility and oral bioavailability, and achieving circulating free plasma levels that provided near maximal CGRP receptor coverage. The clinical efficacy of oral and intranasal gepants and the injectable CGRP monoclonal antibodies (mAbs) are described, as are recent synthetic developments that have benefited from new structural biology data. The first oral gepant was recently approved and heralds a new era in the treatment of migraine.

Nonclinical safety evaluation of erenumab, a CGRP receptor inhibitor for the prevention of migraine

Calcitonin gene-related peptide (CGRP) and its receptor have been implicated as a key mediator in the pathophysiology of migraine. Thus, erenumab, a monoclonal antibody antagonist of the CGRP receptor, administered as a once monthly dose of 70 or 140 mg has been approved for the preventive treatment of migraine in adults. Due to the species specificity of erenumab, the cynomolgus monkey was used in the pharmacology, pharmacokinetics, and toxicology studies to support the clinical program. There were no effects of erenumab on platelets in vitro (by binding, activation or phagocytosis assays). Specific staining of human tissues with erenumab did not indicated any off-target binding. There were no erenumab-related findings in a cardiovascular safety pharmacology study in cynomolgus monkeys or in vitro in human isolated coronary arteries. Repeat-dose toxicology studies conducted in cynomolgus monkeys at dose levels up to 225 mg/kg (1 month) or up to 150 mg/kg (up to 6 months) with twice weekly subcutaneous (SC) doses showed no evidence of erenumab-mediated adverse toxicity. There were no effects on pregnancy, embryo-fetal or postnatal growth and development in an enhanced pre-postnatal development study in the cynomolgus monkey. There was evidence of placental transfer of erenumab based on measurable serum concentrations in the infants up to 3 months post birth. The maternal and developmental no-observed-effect level (NOEL) was the highest dose tested (50 mg/kg SC Q2W). These nonclinical data in total indicate no safety signal of concern to date and provide adequate margins of exposure between the observed safe doses in animals and clinical dose levels.

The effect and safety of monoclonal antibodies to calcitonin gene-related peptide and its receptor on migraine: a systematic review and meta-analysis

BACKGROUND

Migraine has been recognized as one of the leading causes of disability in the 2013 Global Burden of Disease Study and seriously affects the quality of patients' life, current treatment options are not ideal. Monoclonal antibodies to calcitonin gene-related peptide and its receptor (CGRP-mAbs) appear more promising for migraine because of considerably better effect and safety profiles. The objective of this study is to systematically assess the clinical efficacy and safety of CGRP-mAbs for migraine therapy.

METHODS

A systematic literature search in PubMed, Cochrane Library and Baidu Scholar was performed to identify randomized controlled trials (RCTs), which compared the effect and safety of CGRP-mAbs with placebo on migraine. Regarding the efficacy, the reduction of monthly migraine days from baseline to weeks 1-4, 5-8, and 9-12; responder rates were extracted as the outcome measures of the effects of CGRP-mAbs. Regarding the safety, total adverse events, the main adverse events, and other adverse events were evaluated.

RESULTS

We found significant reduction of monthly migraine days in CGRP-mAbs vs. placebo (weeks 1-4: SMD -0.49, 95% CI -0.61 to -0.36; weeks 5-8: SMD -0.43, 95% CI -0.56 to -0.30; weeks 9-12: SMD -0.37, 95% CI -0.49 to -0.24). 50% and 75% responder rates (OR 2.59, 95% CI 1.99 to 3.37; and OR 2.91, 95% CI 2.06 to 4.10) were significantly increased compared with placebo. There was no significant difference in total adverse events (OR 1.17, 95% CI 0.91 to 1.51), and the main adverse events including upper respiratory tract infection (OR 1.44, 95% CI 0.82 to 2.55), nasopharyngitis (OR 0.59, 95% CI 0.30 to 1.16), nausea (OR 0.61, 95% CI 0.29 to 1.32), injection-site pain (OR 1.73, 95% CI 0.95 to 3.16) and back pain (OR 0.97, 95% CI 0.49 to 1.90) were not obviously changed compared with placebo control, but the results showed significant increase of dizziness in CGRP-mAbs vs. placebo (OR 3.22, 95% CI 1.09 to 9.45).

CONCLUSIONS

This meta-analysis suggests that CGRP-mAbs are effective in anti-migraine therapy with few adverse reactions, but more and larger sample-size RCTs are required to verify the current findings.

Analysis of the variability of the pharmacokinetics of multiple drugs in young adult and elderly subjects and its implications for acceptable daily exposures and cleaning validation limits

The elderly constitute a significant, potentially sensitive, subpopulation within the general population, which must be taken into account when performing risk assessments including determining an acceptable daily exposure (ADE) for the purpose of a cleaning validation. Known differences in the pharmacokinetics of drugs between young adults (who are typically the subjects recruited into clinical trials) and the elderly are potential contributors affecting the interindividual uncertainty factor (UF_H) component of the ADE calculation. The UF_H values were calculated for 206 drugs for young adult and elderly groups separately and combined (with the elderly assumed to be a sensitive subpopulation) from published studies where the pharmacokinetics of the young adult and elderly groups were directly compared. Based on the analysis presented here, it is recommended to use a default UF_H value of 10 for worker populations (which are assumed to be approximately equivalent to the young adult groups) where no supporting pharmacokinetic data exist, while it is recommended to use a default UF_H value of 15 for the general population, to take the elderly into consideration when calculating ADE values. The underlying reasons for the large differences between the exposures in the young adult and elderly subjects for the 10 compounds which show the greatest separation are different in almost every case, involving the OCT2 transporter, glucuronidation, hydrolysis, CYP1A2, CYP2A6, CYP2C19, CYP2D6, CYP3A4 or CYP3A5. Therefore, there is no consistent underlying mechanism which appears responsible for the largest differences in pharmacokinetic parameters between young adult and elderly subjects.

Migraine in the era of precision medicine

Migraine is a common neurovascular disorder in the neurologic clinics whose mechanisms have been explored for several years. The aura has been considered to be attributed to cortical spreading depression (CSD) and dysfunction of the trigeminovascular system is the key factor that has been considered in the pathogenesis of migraine pain. Moreover, three genes (CACNA1A, ATP1A2, and SCN1A) have come from studies performed in individuals with familial hemiplegic migraine (FHM), a monogenic form of migraine with aura. Therapies targeting on the neuropeptids and genes may be helpful in the precision medicine of migraineurs. 5-hydroxytryptamine (5-HT) receptor agonists and calcitonin gene-related peptide (CGRP) receptor antagonists have demonstrated efficacy in the acute specific treatment of migraine attacks. Therefore, ongoing and future efforts to find new vulnerabilities of migraine, unravel the complexity of drug therapy, and perform biomarker-driven clinical trials are necessary to improve outcomes for patients with migraine.

CGRP mechanism antagonists and migraine management

Migraine is a complex disorder of the brain that is common and highly disabling. As understanding of the neural pathways has advanced, and it has become clear that the vascular hypothesis does not explain the disorder, new therapeutic avenues have arisen. One such target is calcitonin gene-related peptide (CGRP)-based mechanisms. CGRP is found within the trigeminovascular nociceptive system widely from the trigeminal ganglion to second-order and third-order neurons and in regulatory areas in the brainstem. Studies have shown CGRP is released during severe migraine attacks and the reversal of the attack with effective triptan treatment normalizes those levels. CGRP administration triggers migraine in patients, and CGRP receptor antagonists have been shown to abort migraine. Here, we review the current state of CGRP mechanism antagonist therapy as its research and development is increasing in migraine therapeutics. We discuss several recent trials, highlighting the evidence base behind these novel drugs, and their potential future contribution to migraine management.

New treatments for headache

Migraine and cluster headache are primary headache disorders commonly encountered in clinical practice. Despite the profound disability caused by these primary headache disorders, available acute and preventive treatment options are limited. Recent understanding of headache pathophysiology has led to the development of new drug formulations and novel drug targets that are extremely promising. This article will highlight several of the new treatments that are currently under investigation including novel delivery mechanisms of already existing medications, calcitonin gene-related peptide (CGRP) receptor antagonists, antibodies to CGRP and its receptor, serotonin receptor agonists, transient receptor potential vanilloid receptor modulators, orexin receptor antagonists, glial cell modulators, and neuromodulation. If data is supportive, these therapies will be welcome additions to the headache specialist's armamentarium.

Novel strategies for the treatment of migraine attacks via the CGRP, serotonin, dopamine, PAC1, and NMDA receptors

INTRODUCTION

Migraine is a common, paroxysmal, and disabling primary headache with a high personal and socioeconomic impact. It involves ∼ 16% of the general population. During the years, a number of hypotheses have been put forward concerning the exact pathomechanism, but the final solution is still undiscovered.

AREAS COVERED

Although the origin is enigmatic, parallel therapeutic efforts have been developed. Current attack therapy does not meet the expectations of the patients or the doctors. This article, based on a PubMed search, reviews the novel pharmacological possibilities that influence the peripheral and central sensitization involved in the disease.

EXPERT OPINION

In order to overcome the therapeutic insufficiency, a calcitonin gene-related peptide receptor antagonist without the side-effect of liver transaminase elevation is required. Another therapeutic option is to develop a neurally acting antimigraine agent, such as a serotonin-1F receptor agonist, with low adverse central nervous system events. Development of a potent dopamine receptor antagonist is necessary to diminish the premonitory symptoms of migraine. A further option is to decrease the headache intensity with a pituitary adenylate cyclase-activating polypeptide type 1 receptor blocker which can cross the blood-brain barrier. Finally, synthetic kynurenine analogues are required to block the pain transmission in the activated trigeminal system.

[Current state of knowledge and developments in the prophylaxis and acute treatment of migraine]

For the acute treatment of the headache phase of a migraine attack, a variety of different pharmacotherapeutic treatment options exist. These range from nonspecifically acting non-opioid analgesics (e.g., paracetamol) and nonsteroidal anti-inflammatory substances (e.g., acetylsalicylic acid, ibuprofen, naproxen, diclofenac) to agents specifically interfering with the serotonin system (ergot alkaloids such as ergotamine and its derivatives, triptans). In patients with significant emesis co-occurring during an attack, additional antiemetics such as metoclopramide or domperidone may be administered. In migraine prophylaxis, largely divergent agents, e.g., β-adrenoceptor antagonists, Ca-antagonists, or anticonvulsants, are commonly used. The diversity of these compounds may help the treating physician to tailor prophylactic treatment to the patient's individual needs. The treatment success of the individual patient is difficult to predict both in acute and prophylactic migraine treatment. Apart from contraindications or associated side effects of a particular substance, the individual patient's response to treatment is therefore a major determinant in selecting the suitable medication.

The TRPA1 channel in migraine mechanism and treatment

Migraine remains an elusive and poorly understood disease. The uncertainty is reflected by the currently unsatisfactory acute and prophylactic treatments for this disease. Genetic and pharmacological information points to the involvement of some transient receptor potential (TRP) channels in pain mechanisms. In particular, the TRP vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1) channels seem to play a major role in different models of pain diseases. Recent findings have underscored the possibility that TRP channels expressed in the nerve terminals of peptidergic nociceptors contribute to the migraine mechanism. Among this channel subset, TRPA1, a sensor of oxidative, nitrative and electrophilic stress, is activated by an unprecedented series of irritant and pain-provoking exogenous and endogenous agents, which release the pro-migraine peptide, calcitonin gene-related peptide, through this neuronal pathway. Some of the recently identified TRPA1 activators have long been known as migraine triggers. Furthermore, specific analgesic and antimigraine medicines have been shown to inhibit or desensitize TRPA1 channels. Thus, TRPA1 is emerging as a major contributing pathway in migraine and as a novel target for the development of drugs for pain and migraine treatment.

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.

New Agents for Acute Treatment of Migraine: CGRP Receptor Antagonists, iNOS Inhibitors

OPINION STATEMENT

The treatment of migraine was advanced dramatically with the introduction of triptans in the early 1990s. Despite the substantial improvement in the quality of life that triptans have brought to many migraineurs, a substantial cohort of patients remain highly disabled by attacks and need new therapeutic approaches, which ideally should be quick-acting, have no vasoconstrictor activity, and have a longer duration of action and be better tolerated than current therapies. The calcitonin gene-related peptide (CGRP) receptor antagonists (gepants)-olcegepant (BIBN 4096 BS), telcagepant (MK-0974), MK3207, and BI 44370 TA-are effective in treating acute migraine. They have no vasoconstrictive properties, fewer adverse effects, and may act longer than triptans. Their development has been complicated by liver toxicity issues when used as preventives. Results from studies with BI 44370 TA do not support broad concern about a class effect, and further studies are ongoing in this respect. Many experimental studies and clinical trials suggest that nitric oxide may have a role in the pathophysiology of migraine. Therefore, the inhibition of nitric oxide synthase (NOS) for the acute or prophylactic treatment of migraine offered a feasible approach; as inducible NOS (iNOS) is involved in several pain states, such as inflammatory pain, it appeared to be an attractive target. However, despite high selectivity and potency, the iNOS inhibitor GW274150 was not effective for acute treatment or prophylaxis of migraine, suggesting that iNOS is very unlikely to be a promising target.

A randomized, placebo-controlled study of the effects of telcagepant on exercise time in patients with stable angina

Telcagepant is a calcitonin gene-related peptide (CGRP) receptor antagonist being evaluated for acute migraine treatment. CGRP is a potent vasodilator that is elevated after myocardial infarction, and it delays ischemia during treadmill exercise. We tested the hypothesis that CGRP receptor antagonism does not reduce treadmill exercise time (TET). The effects of supratherapeutic doses of telcagepant on TET were assessed in a double-blind, randomized, placebo-controlled, two-period, crossover study in patients with stable angina and reproducible exercise-induced angina. Patients received telcagepant (600 mg, n = 46; and 900 mg, n = 14) or placebo and performed treadmill exercise at T(max) (2.5 h after the dose). The hypothesis that telcagepant does not reduce TET was supported if the lower bound of the two-sided 90% confidence interval (CI) for the mean treatment difference (telcagepant-placebo) in TET was more than -60 s. There were no significant between-treatment differences in TET (mean treatment difference: -6.90 (90% CI: -17.66, 3.86) seconds), maximum exercise heart rate, or time to 1-mm ST-segment depression using pooled data or with stratification for dose.

Telcagepant: A New Therapeutic Option for Acute Migraine?

Telcagepant (MK0974) is one of several calcitonin-gene-related peptide antagonists in development as a potential treatment for acute migraine attacks and is the first orally available drug in this class. Preclinical and clinical data are reviewed, which support the efficacy and tolerability of telcagepant for the treatment of migraine, particularly for patients unable to tolerate, or who have cardiovascular contraindications to, triptans.

The Dose Proportionality of Telcagepant after Administration of Single Oral and Intravenous Doses in Healthy Adult Subjects

INTRODUCTION: Telcagepant (MK-0974) is a novel, orally active and selective CGRP receptor antagonist being investigated for acute treatment of migraine. Early clinical data suggested greater than dose proportional increases in exposure following oral administration. The aim of the present studies was to definitively characterize the oral and IV dose proportionality of telcagepant. METHODS: Healthy adult subjects were enrolled in two separate open-label randomized dose proportionality studies: 1) single oral dose crossover from 50 to 600 mg (N = 19); 2) single IV dose parallel group from 5 to 250 mg (N = 10 per dose). Blood samples were collected at time points from 0 to 48 hours postdose. RESULTS: Telcagepant was rapidly absorbed with a T(max) of approximately 1 to 2 hours after oral administration. The terminal half-life was approximately 8 to 9 hours after IV dosing and approximately 4 to 7 hours after oral dosing. Oral administration of telcagepant resulted in greater than dose proportional increases in exposure, while IV administration resulted in approximately dose proportional increases in exposure. CONCLUSIONS: Telcagepant was generally well tolerated. Oral telcagepant exhibits non-linear pharmacokinetics.

New drugs in migraine treatment and prophylaxis: telcagepant and topiramate

Although the triptan drugs provide effective relief from migraine for many patients, a substantial number of affected individuals are unresponsive to these compounds, and such therapy can also lead to a range of adverse effects. Telcagepant represents a new class of antimigraine drug-the calcitonin gene-related peptide receptor blockers. This compound exerts its effects by blocking receptors for the calcitonin-gene-related peptide at several sites in the trigeminal and central nervous systems, resulting in pain relief. Telcagepant does not cause vasoconstriction, a major limitation in the use of triptans. Comparisons with triptans in clinical trials for acute treatment of migraine attacks revealed clinical effects similar to those of triptans but better than those of placebo. Telcagepant might provide hope for those who have a poor response to, or are unable to use, older drugs. In patients who need prophylaxis because of frequent attacks of migraine, topiramate is a first-line drug for migraine prevention in many countries; it is generally safe and reasonably well tolerated. Data suggest that topiramate could aid reversion of chronic migraine to episodic migraine.

CGRP receptor antagonism and migraine

Calcitonin gene-related peptide (CGRP) is expressed throughout the central and peripheral nervous systems, consistent with control of vasodilatation, nociception, motor function, secretion, and olfaction. alphaCGRP is prominently localized in primary spinal afferent C and ADelta fibers of sensory ganglia, and betaCGRP is the main isoform in the enteric nervous system. In the CNS there is a wide distribution of CGRP-containing neurons, with the highest levels occurring in striatum, amygdala, colliculi, and cerebellum. The peripheral projections are involved in neurogenic vasodilatation and inflammation, and central release induces hyperalgesia. CGRP is released from trigeminal nerves in migraine. Trigeminal nerve activation results in antidromic release of CGRP to cause non-endothelium-mediated vasodilatation. At the central synapses in the trigeminal nucleus caudalis, CGRP acts postjunctionally on second-order neurons to transmit pain signals centrally via the brainstem and midbrain to the thalamus and higher cortical pain regions. Recently developed CGRP receptor antagonists are effective at aborting acute migraine attacks. They may act both centrally and peripherally to attenuate signaling within the trigeminovascular pathway.