Orexin Receptor Antagonism, a New Sleep-Promoting Paradigm: An Ascending Single-Dose Study With Almorexant

Central nervous system effects of TAK-653, an investigational alpha-amino-3-hydroxy-5-methyl-4-isoxazole receptor (AMPAR) positive allosteric modulator in healthy volunteers

TAK-653 is a novel AMPA receptor positive allosteric modulator in clinical development for the treatment of major depressive disorder (MDD). This study aimed to measure the functional pharmacodynamic central nervous system (CNS) effects of TAK-653. A randomised, double-blind, placebo-controlled, three-way crossover (placebo, TAK-653 0.5 mg and 6 mg) study with 24 healthy volunteers was performed. NeuroCart tests consisting of body sway (BS), saccadic peak velocity (SPV), smooth pursuit eye movements (SP), adaptive tracking (AT), Bowdle and Bond and Lader Visual Analogue Scales (B-VAS and BL-VAS) and Stroop test were performed pre-dose and 3.5 and 4 h post-dose. Data were analysed using a mixed model analysis of covariance with baseline as covariate. It was found that TAK-653 did not affect BS and subjective drug effects as measured by B-VAS and BL-VAS at either dose level. TAK-653 0.5 mg increased SPV (degrees/second) (19.49 [5.98, 32.99], P = 0.02) and affected Stroop difference in reaction time between correct congruent and correct incongruent answers and number of correct responses in incongruent trials (22.0 [4.0, 40.0], P = 0.05 and -0.3 [-0.5, -0.1], P = 0.02, respectively). TAK-653 6 mg improved AT (%) (1.68 [0.51, 2.84], P = 0.02) and increased SPV (degrees/s) (15.40 [1.91, 28.90], P = 0.06) and SP (%) (2.32 [0.37, 4.27], P = 0.05). Based on these findings it can be concluded that TAK-653 demonstrated a psychostimulant-like pharmacodynamic profile on the NeuroCart consistent with previously reported increase of cortical excitability following Transcranial Magnetic Stimulation (TMS) of the human motor cortex.

Identification of Highly Selective Orexin 1 Receptor Antagonists Driven by Structure-Based Design

OX1 receptor antagonists are of interest to treat, for example, substance abuse disorders, personality disorders, eating disorders, or anxiety-related disorders. However, known dual OX1/OX2 receptor antagonists are not suitable due to their sleep-inducing effects; therefore, we were interested in identifying a highly OX1 selective antagonist with a sufficient window to OX2-mediated effects. Herein, we describe the design of highly selective OX1 receptor antagonists driven by the X-ray structure of OX1 with suvorexant, a dual OX1/OX2 receptor antagonist. Moderately selective OX1 antagonists comprising a [2.2.1]-bicyclic scaffold served as our starting point. Based on our binding mode hypothesis, we postulated which part of the scaffold points toward one of the regions where the two binding pockets differ. Structural changes in this part resulted in a modified core with higher inherent selectivity compared to the [2.2.1]-bicyclic template. The structure-based design, synthesis, and hit-to-lead evaluation of this novel OX1 receptor-selective scaffold are discussed herein.

Pharmacokinetics and Pharmacodynamics of the Dual Orexin Receptor Antagonist Daridorexant in Japanese and Caucasian Subjects

PURPOSE/BACKGROUND

Daridorexant is a dual orexin receptor antagonist in development for the treatment of sleep disorders. Thus far, it has not yet been studied in Japanese subjects. Study objectives were to evaluate the pharmacokinetics (PK), pharmacodynamics (PD), and safety of single- and multiple-dose administration of daridorexant in healthy Caucasian and Japanese subjects.

METHODS/PROCEDURES

This was a double-blind, placebo-controlled, randomized study. Subjects received once-daily doses of daridorexant (25 or 50 mg) or placebo for 5 days. Pharmacokinetics and safety were investigated using standard assessments. To assess PD effects, a battery of tests (saccadic peak velocity, body sway, adaptive tracking performance, and visual analog scales for alertness, mood, and calmness), known to be sensitive to sleep-promoting drugs was used.

FINDINGS/RESULTS

On day 1, PK variables were similar between Caucasian and Japanese subjects. On day 5, slight accumulation occurred in Japanese but not in Caucasian subjects, resulting in a higher maximum concentration (1403 vs 1006 ng/mL) and area under the curve (8256 vs 6306 ng·h/mL) at a dose of 50 mg, whereas values for time to maximum concentration and half-life were similar. Daridorexant dose-dependently reduced vigilance, attention, visuomotor coordination, and postural stability. Pharmacokinetic effects were detectable within 1 hour after drug administration and returned to baseline 4 to 8 hours postdose. Overall, Japanese showed slightly larger PD effects and reported more adverse events than Caucasians. The most frequently reported were somnolence, fatigue, and headache. Changes in other safety assessments were unremarkable.

IMPLICATIONS/CONCLUSIONS

The PK, PD, and safety profile of daridorexant were similar in Japanese and Caucasian subjects.

Pharmacological Interactions between the Dual Orexin Receptor Antagonist Daridorexant and Ethanol in a Double-Blind, Randomized, Placebo-Controlled, Double-Dummy, Four-Way Crossover Phase I Study in Healthy Subjects

BACKGROUND

Daridorexant (ACT-541468) is a potent dual orexin receptor antagonist under development for the treatment of sleep disorders. Concomitant intake of ethanol and hypnotics has been shown to result in additive/supra-additive depression of the central nervous system, resulting in pronounced sedation.

OBJECTIVE

The aim of this study was to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) interactions between ethanol and daridorexant.

METHOD

This was a single-center, double-blind, placebo-controlled, randomized, four-way crossover study conducted in 19 healthy male/female subjects. Subjects received the following four treatments: ethanol with daridorexant, daridorexant alone, ethanol alone, and placebo. Daridorexant 50 mg and the matching placebo were administered as single oral tablets. Ethanol was infused intravenously and clamped at a level of 0.6 g/L for 5 h. The PK of ethanol and daridorexant were assessed and a battery of PD tests performed.

RESULTS

Concomitant administration of ethanol prolonged the time to reach maximum plasma concentrations (t_max) of daridorexant (median difference 1.25 h). No other relevant PK interactions were observed. Coadministration with ethanol produced a numerically greater impairment on saccadic peak velocity, body sway, visual analog scale (VAS) alertness, VAS alcohol intoxication, smooth pursuit, and adaptive tracking compared with daridorexant alone. All treatments were generally well tolerated without serious adverse events (AEs). The most commonly reported treatment-emergent AEs following coadministration of daridorexant and ethanol included somnolence, headache, fatigue, sudden onset of sleep, and dizziness.

CONCLUSIONS

Apart from a shift in t_max, no relevant changes in PK parameters were observed following coadministration of daridorexant and ethanol. The coadministration led to reinforced drug actions that were, at most, indicative of infra-additive effects on certain PD markers. Patients will be advised not to consume ethanol with daridorexant.

CLINICAL TRIALS REGISTRATION NUMBER

NCT03609775 (ClinicalTrials.gov Identifier).

Investigation of the effect of the dual orexin receptor antagonist almorexant on ophthalmological, spermatogenic, and hormonal variables in healthy male subjects

BACKGROUND/AIMS

The aim of this single-center, double-blind study was to investigate the effect of a 4-week once daily administration of 200 mg almorexant on tear film break-up time, spermatogenesis, hormone levels, and pancreatic elastase in stool in healthy male subjects.

METHODS

Almorexant 200 mg or matching placebo was administered in the evening for 4 weeks once daily to 56 healthy male subjects. Changes in ophthalmological variables, sperm composition, hormone levels, and pancreatic elastase levels in stool were evaluated periodically up to 8 weeks after discontinuation of drug administration. Blood samples for pharmacokinetic measurements were taken after 4 weeks to confirm compliance to study drug intake.

RESULTS

The results of this study revealed no treatment effects of almorexant, neither on tear film break-up time nor on other ophthalmological variables investigated during this study. Furthermore, spermatogenesis, hormones of the hypothalamic-pituitary-adrenal and -gonadal axes, and endocrine pancreatic secretion were shown to be not affected by a 4-week once daily administration of almorexant.

CONCLUSION

Almorexant was well tolerated and had no effect on the spectrum of pharmacodynamic variables assessed. Ophthalmology and testicular findings detected in preclinical studies were not observed in this clinical study. Therefore, these preclinical findings appear not to be relevant for humans and do not prevent from conducting larger clinical trials with either healthy subjects or patients.

The Quest for the Best Dual Orexin Receptor Antagonist (Daridorexant) for the Treatment of Insomnia Disorders

Since its discovery in 1998, the orexin system has been of interest to the research community as a potential therapeutic target for the treatment of sleep/wake disorders, stress and anxiety disorders, addiction or eating disorders. It consists of two G protein-coupled receptors, the orexin 1 and orexin 2 receptors, and two neuropeptides with agonistic effects, the orexin A and orexin B peptides. Herein we describe our efforts leading to the identification of a promising set of dual orexin receptor antagonists (DORAs) which subsequently went through physiology-based pharmacokinetic and pharmacodynamic modelling>^[1] and finally led to the selection of daridorexant, currently in phase 3 clinical trials for the treatment of insomnia disorders.

Acute cognitive effects of the hypocretin receptor antagonist almorexant relative to zolpidem and placebo: a randomized clinical trial

STUDY OBJECTIVES

Hypnotic medications can adversely affect behavior during unanticipated awakenings during the night. Animals treated with the hypocretin (Hcrt) receptor antagonist almorexant (ALM) have less acute cognitive impairment compared to the GABAA receptor modulator zolpidem (ZOL). This study aimed to determine whether ALM produces less acute cognitive impairment than ZOL in human subjects.

METHODS

Healthy, young adult, unmedicated male and female subjects participated in a controlled trial of a single dose of ALM 100 mg (N = 48), ALM 200 mg (N = 53), ZOL 10 mg (N = 49), and placebo (PBO, N = 52).

RESULTS

ZOL and both doses of ALM produced similar levels of subjective sleepiness and impaired the ability of subjects to remain awake in a dark, low-stimulus setting relative to PBO. For most cognitive measures, performance under ZOL was significantly worse than ALM or PBO. For tasks involving verbal memory or visual-motor coordination, ZOL impaired performance, whereas the two doses of ALM were no different than PBO. For tasks involving higher-order executive function, ZOL produced impairment in processing speed and inhibitory control, whereas the two doses of ALM were no different than PBO. Performance decrements for ALM were less than ZOL but greater than PBO for some reaction time measures.

CONCLUSIONS

The data provide support for the hypothesis that Hcrt receptor antagonists produce less functional impairment than a benzodiazepine receptor agonist (BzRA). These observations are particularly relevant to patients treated with sedative-hypnotics who are at elevated risk for falls and other untoward events during the intended hours for sleep.

Synthesis and biological activity evaluation of azacycloheptane sulfonamide derivatives as potential orexin receptor antagonists

As the orexin signaling system is crucial for the regulation of the sleep/wake cycle, inhibitors of orexin-1 and orexin-2 receptors are of significant interest in the treatment of insomnia. Herein, a series of novel azacycloheptane sulfonamide derivatives were designed and synthesized, and all the compounds were evaluated as potential orexin receptor inhibitors by FLIPR Tetra calcium assay. A majority of the tested azacycloheptane sulfonamide derivatives showed OX1R and OX2R inhibitory activity. Chloro-substituted derivatives functionalized at the C5 or C6 position of the benzoxazole group exhibited better inhibitory activity for OX1R and OX2R than unsubstituted derivatives functionalized at C5 or C6. In addition, phenyl group modification had positive effects on the inhibitory activities, and an electron-withdrawing fluorine group at the ortho or meta position of the phenyl ring improved the OX2R inhibitory activity of the derivatives. This suggests that azacycloheptane sulfonamide derivatives are promising scaffolds for the development of OX1R and OX2R antagonists.

Azacycloheptane sulfonamide derivatives are promising scaffolds for the development of OX1R and OX2R antagonists.

Dual orexin receptor antagonists increase sleep and cataplexy in wild type mice

Orexin receptor antagonists are clinically useful for treating insomnia, but thorough blockade of orexin signaling could cause narcolepsy-like symptoms. Specifically, while sleepiness is a desirable effect, an orexin antagonist could also produce cataplexy, sudden episodes of muscle weakness often triggered by strong, positive emotions. In this study, we examined the effects of dual orexin receptor antagonists (DORAs), lemborexant (E2006) and almorexant, on sleep-wake behavior and cataplexy during the dark period in wild-type (WT) mice and prepro-orexin knockout (OXKO) mice. In WT mice, lemborexant at 10 and 30 mg/kg quickly induced NREM sleep in a dose-dependent fashion. In contrast, lemborexant did not alter sleep-wake behavior in OXKO mice. Under the baseline condition, cataplexy was rare in lemborexant-treated WT mice, but when mice were given chocolate as a rewarding stimulus, lemborexant dose-dependently increased cataplexy. Almorexant produced similar results. Collectively, these results demonstrate that DORAs potently increase NREM and REM sleep in mice via blockade of orexin signaling, and higher doses can cause cataplexy when co-administered with a likely rewarding stimulus.

Orexin Receptor Antagonists as Emerging Treatments for Psychiatric Disorders

Orexins comprise two neuropeptides produced by orexin neurons in the lateral hypothalamus and are released by extensive projections of these neurons throughout the central nervous system. Orexins bind and activate their associated G protein-coupled orexin type 1 receptors (OX1Rs) and OX2Rs and act on numerous physiological processes, such as sleep-wake regulation, feeding, reward, emotion, and motivation. Research on the development of orexin receptor antagonists has dramatically increased with the approval of suvorexant for the treatment of primary insomnia. In the present review, we discuss recent findings on the involvement of the orexin system in the pathophysiology of psychiatric disorders, including sleep disorders, depression, anxiety, and drug addiction. We discuss the actions of orexin receptor antagonists, including selective OX1R antagonists (SORA1s), selective OX2R antagonists (SORA2s), and dual OX1/2R antagonists (DORAs), in the treatment of these disorders based on both preclinical and clinical evidence. SORA2s and DORAs have more pronounced efficacy in the treatment of sleep disorders, whereas SORA1s may be promising for the treatment of anxiety and drug addiction. We also discuss potential challenges and opportunities for the application of orexin receptor antagonists to clinical interventions.

First-in-human study with ACT-539313, a novel selective orexin-1 receptor antagonist

AIMS

The orexin system is involved in anxiety behaviour and corresponding physiological reactions and constitutes a target for treatment of anxiety disorders. ACT-539313 is a potent, selective orexin-1 receptor antagonist being developed for the treatment of anxiety disorders. This first-in-human study investigated its single-dose pharmacokinetics (PK) including food effect, pharmacodynamics (PD), safety and tolerability.

METHODS

This double-blind, placebo-controlled, randomized study included 40 healthy male subjects. Ascending oral doses of 10-400 mg ACT-539313 were investigated in 5 dose groups of 8 subjects (of whom 2 received placebo per dose group). At 100 mg, subjects received ACT-539313 in fasted and fed conditions in a fixed sequential design. PK, PD (objective and subjective measures of sedation and effects on central nervous system), safety and tolerability were assessed.

RESULTS

In fasted conditions, ACT-539313 was rapidly absorbed (median time to maximum plasma concentration [C_max ] 0.7-3.5 h) and cleared from plasma with a mean terminal half-life of 3.3-5.7 h across dose levels. A 1.63-fold (90% confidence interval: 1.26-2.11) increase in C_max and no change in area under the concentration-time curve extrapolated to infinity was observed under fed compared to fasted conditions. No relevant PD signals were detected except for a trend of reduced saccadic peak velocity around time to C_max . The most commonly reported adverse events were somnolence and headache. All adverse events were transient and of mild or moderate intensity. No treatment-related effects on vital signs, clinical laboratory or 12-lead electrocardiogram were observed.

CONCLUSIONS

ACT-539313 exhibits good safety and tolerability at single doses of up to and including 400 mg that warrant further investigations.

Multiple-Ascending Dose Study in Healthy Subjects to Assess the Pharmacokinetics, Tolerability, and CYP3A4 Interaction Potential of the T-Type Calcium Channel Blocker ACT-709478, A Potential New Antiepileptic Drug

BACKGROUND

ACT-709478 is a selective, orally available T-type calcium channel blocker being studied as a potential new treatment in epilepsy. ACT-709478 had previously been investigated in a single-ascending dose study up to a dose of 400 mg.

OBJECTIVES

The aim of this study was to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple doses of ACT-709478. In addition, the drug-drug interaction potential of multiple doses of ACT-709478 with the cytochrome P450 3A4 substrate midazolam was investigated.

METHODS

This double-blind, placebo-controlled, randomized study included 46 healthy male and female subjects. Ascending multiple oral doses of ACT-709478 were administered to 10 (cohorts 1-2) or 12 (cohorts 3-4) subjects (two taking placebo per cohort). In cohorts 1-2, 30 or 10 mg ACT-709478 was administered once daily for 12 days. An up-titration regimen was used in cohorts 3-4 with administration of 10, 30, and 60 mg for 7 days each in both cohorts and an additional dose level of 100 mg ACT-709478 once daily for 8 days in cohort 4. Single doses of midazolam were administered at baseline and concomitantly to 60 mg and 100 mg ACT-709478 in cohort 4. Blood sampling for pharmacokinetic evaluations and safety assessments (clinical laboratory, vital signs, adverse events, and electrocardiogram) were performed regularly. Holter electrocardiograms were recorded at baseline and for 24 h at steady state and central nervous system effects were assessed with pharmacodynamic tests at baseline and steady state.

RESULTS

ACT-709478 was absorbed with a time to reach the maximum plasma concentration of 3.5-4.0 h and eliminated with a half-life of 45-53 h. Steady state was reached after 5-7 days of dosing and exposure increased dose-proportionally. An accumulation index of approximately three fold was observed in cohorts 1 and 2. Exposure to midazolam was lower upon concomitant administration of 60 and 100 mg ACT-709478 compared to midazolam alone while the half-life and time to reach the maximum plasma concentration of midazolam remained unchanged, suggesting a weak induction at the gastrointestinal but not hepatic level. Pharmacokinetic parameters of 1-hydroxymidazolam were not affected by ACT-709478 administration. The most frequent adverse events were dizziness, somnolence, and headache. A tolerability signal was detected in cohort 1 (30 mg once daily); therefore, the dose was decreased to 10 mg once daily in cohort 2. The subsequently established up-titration regimen, starting with 10 mg once daily, considerably improved tolerability. Multiple doses up to 100 mg once daily were well tolerated. No treatment-related effects were detected on vital signs, clinical laboratory tests, Holter electrocardiogram variables, or in the pharmacodynamic tests.

CONCLUSIONS

ACT-709478 exhibits good tolerability up to 100 mg once daily using an up-titration regimen and pharmacokinetic properties that support further clinical investigations. A weak induction of gastrointestinal cytochrome P450 3A4 activity was observed, unlikely to be of clinical relevance. CLINICALTRIALS.

GOV IDENTIFIER

NCT03165097.

Clinical pharmacology of the dual orexin receptor antagonist ACT-541468 in elderly subjects: Exploration of pharmacokinetics, pharmacodynamics and tolerability following single-dose morning and repeated-dose evening administration

BACKGROUND

The dual orexin receptor antagonist ACT-541468 showed sedative pharmacodynamic effects during initial clinical testing in adult subjects. The present study explored pharmacokinetics, pharmacodynamics and tolerability in healthy elderly subjects.

METHODS

Double-blind, placebo-controlled, randomised, single-ascending dose study in 24 male/female elderly (65-80 years, 5, 15 and 25 mg in the morning, 6/2 active/placebo per group). Additionally, 10 subjects (8/2 active/placebo) received 25 mg for 7 days in the evening. Pharmacokinetics, pharmacodynamics (saccadic peak velocity, adaptive tracking, body sway, visual analogue scales according to Bowdle and Bond and Lader, Karolinska Sleepiness Scale) and tolerability were assessed. In particular, pharmacodynamics results are to be interpreted exploratorily.

RESULTS

Absorption was quick with a median time to maximum concentration of ∼ 1.0 h. The mean elimination half-life was 8.5-9.8 h, the area under the curve and the maximum plasma concentration increased proportionally with dose. Following repeated evening administration of 25 mg, minimal accumulation was observed. There were no pharmacodynamic effects at 5 mg. At 15 mg, saccadic peak velocity (degree/s; SD) was reduced (69; 38), while other variables showed no effects. At 25 mg, effects on all objective pharmacodynamic parameters were observed. At 8-12 h post-dose, there were no differences to placebo and no next-day effects on pharmacodynamic variables after evening administration. Elderly subjects reported fewer adverse events compared to adults in previous studies.

CONCLUSION

ACT-541468 in elderly subjects was well tolerated and pharmacokinetics and pharmacodynamics are compatible with a drug for the treatment of insomnia. Clinicaltrials.gov: NCT02571855.

The Pictet-Spengler Reaction Updates Its Habits

The Pictet-Spengler reaction (P-S) is one of the most direct, efficient, and variable synthetic method for the construction of privileged pharmacophores such as tetrahydro-isoquinolines (THIQs), tetrahydro-β-carbolines (THBCs), and polyheterocyclic frameworks. In the lustro (five-year period) following its centenary birthday, the P-S reaction did not exit the stage but it came up again on limelight with new features. This review focuses on the interesting results achieved in this period (2011-2015), analyzing the versatility of this reaction. Classic P-S was reported in the total synthesis of complex alkaloids, in combination with chiral catalysts as well as for the generation of libraries of compounds in medicinal chemistry. The P-S has been used also in tandem reactions, with the sequences including ring closing metathesis, isomerization, Michael addition, and Gold- or Brønsted acid-catalyzed N-acyliminium cyclization. Moreover, the combination of P-S reaction with Ugi multicomponent reaction has been exploited for the construction of highly complex polycyclic architectures in few steps and high yields. The P-S reaction has also been successfully employed in solid-phase synthesis, affording products with different structures, including peptidomimetics, synthetic heterocycles, and natural compounds. Finally, the enzymatic version of P-S has been reported for biosynthesis, biotransformations, and bioconjugations.

Multiple-dose clinical pharmacology of ACT-541468, a novel dual orexin receptor antagonist, following repeated-dose morning and evening administration

ACT-541468 is a dual orexin receptor antagonist with sleep-promoting effects in humans. Following entry-into-humans, its pharmacokinetics (PK) including dose-proportionality and accumulation, pharmacodynamics (PD), safety, and tolerability following multiple-ascending oral dose (MAD) administration in the morning, and next-day residual effects after repeated evening administration were investigated in a double-blind, placebo-controlled, randomized study. 31 healthy male and female subjects in 3 dose-groups (10, 25, and 75 mg) received study drug in the morning for 5 days (MAD part), and 20 healthy subjects received 25 mg in the evening for 1 week (evening part). PK, PD (saccadic peak velocity (SPV), adaptive tracking, body sway, Bond and Lader visual analogue scales (VAS), Karolinska Sleepiness Scale (KSS), VAS Bowdle for assessment of psychedelic effects), Digit Symbol Substitution Test (DSST), and Simple Reaction Time Test (SRTT), safety, and tolerability were assessed. ACT-541468 was absorbed with a median t_max of 1.0-2.0 h across the 3 dose groups. The geometric mean elimination half-life (t_½) on Day 5 was between 5.6 and 8.5 h, and the exposure (area under the curve (AUC)) showed dose proportionality. No accumulation and no influence of sex on the multiple-dose PK parameters of ACT-541468 was observed. No effects were observed at 10 mg. Administration of 25 and 75 mg during the day showed clear dose-dependent effects on the PD parameters, while next-day effects were absent after evening administration of 25 mg. The drug was safe and well tolerated. In conclusion, multiple-dose PK/PD of ACT-541468 were compatible with a drug designated to treat insomnia.

Metabolism of the Dual Orexin Receptor Antagonist ACT-541468, Based on Microtracer/ Accelerator Mass Spectrometry

Background:

As part of an integrated and innovative approach to accelerate the clinical development of the dual receptor antagonist ACT-541468, 6 healthy subjects in one cohort in a first-in-humans (FIH) study received an oral dose of 50 mg non-labeled ACT-541468 together with a microtracer amount of 250 nCi of 14C-labeled ACT- 541468 to investigate its absorption, distribution, metabolism, and excretion (ADME).

Methods:

Using accelerator mass spectrometry (AMS), radiochromatograms were constructed for fractionated plasma, urine, and feces samples. Subsequently, the structures of the metabolites were elucidated using high performance liquid chromatography (HPLC) coupled with high resolution mass spectrometry.

Results:

In total 77 metabolites have been identified of which 30, 28, and 60 were present in plasma, urine, and feces, respectively. In plasma, the major metabolites were the mono-oxidized benzylic alcohol M3, the ACT-541468 aldehyde M1, formed by further oxidation of M3 in the benzylic position, and the doubly oxidized M10, formed by (1) benzylic oxidation of M3 (loss of one molecule of water and one molecule of ammonia) and (2) additional loss of water from the oxidized pyrrolidine ring of M5. Transformation of the pyrrolidine to a 6-membered ring was detected. Metabolites that accounted for more than 5% of total radioactivity in excreta were M2, which is also formed by oxidation at the benzylic position, M4, formed by demethylation of the methoxy-group, M7 and A6, both formed by oxidation of M4, and M10, the only major metabolite detected in urine.

Conclusion:

In conclusion, ACT-541468 is extensively metabolized predominantly by oxidative transformations.

The selective orexin-2 receptor antagonist seltorexant improves sleep: An exploratory double-blind, placebo controlled, crossover study in antidepressant-treated major depressive disorder patients with persistent insomnia

BACKGROUND

Insomnia is common in patients with major depressive disorder. Although antidepressants improve mood, insomnia often persists as a result of physiological hyperarousal. The orexin-2 receptor is increasingly being recognized as a new target for the treatment of persistent insomnia in major depressive disorder .

AIM

This exploratory study investigated the effects of seltorexant on objective sleep parameters and subjective depressive symptoms in antidepressant treated major depressive disorder patients with persistent insomnia.

METHODS

Twenty male and female patients received a single dose of 10, 20, 40 mg seltorexant and placebo with a washout period of seven days in a double-blind four-way crossover study. Effects on latency to persistent sleep, total sleep time and sleep efficiency were assessed with polysomnography. Subjective changes in mood were explored by the Quick Inventory of Depressive Symptomatology Self-Report. Safety was recorded and suicidal ideation and behavior were assessed with the Columbia Suicide Severity Rating Scale.

RESULTS

Latency to persistent sleep was significantly shorter for all doses of seltorexant compared to placebo. Placebo least square mean was 61.05 min with least square mean ratios treatment/placebo (80% confidence interval) of 0.32 (0.24-0.44), 0.15 (0.11-0.2) and 0.17 (0.12-0.23) 19.69, 9.2, 10.15 for 10, 20 and 40 mg seltorexant respectively, (all p<0.001). Total sleep time was significantly longer for all doses of seltorexant compared to placebo. Sleep efficiency was significantly improved. The Quick Inventory of Depressive Symptomatology Self-Report demonstrated a trend to mood-improvement for the 40 mg group.

CONCLUSIONS

Seltorexant showed a statistically significant, dose-dependent decrease in latency to persistent sleep, and increase in total sleep time and sleep efficiency combined with a tendency toward subjectively improved mood.

Impact of pharmacokinetic-pharmacodynamic modelling in early clinical drug development

Early clinical pharmacology studies in healthy subjects are often dissociated from patient studies. In this review we encourage the use of modelling and simulation techniques to generate valuable information at an early stage of clinical development. We illustrate these principles by presenting 5 different case studies from a spectrum of therapeutic drug classes. Their application leads to a better understanding of drug characteristics early on, thereby facilitating the design of dose-finding studies in the target patient population and saving resources.

Dual Orexin Receptor Antagonist, Almorexant, in Elderly Patients With Primary Insomnia: A Randomized, Controlled Study

Objective

Sleep laboratory study to determine the dose-related efficacy and safety of almorexant in elderly patients with primary chronic insomnia.

Methods

Patients aged ≥65 years with primary insomnia were enrolled into a prospective, randomized, double-blind, placebo-controlled, multicenter dose-finding study with a five-period, five-way Latin square cross-over design. Patients were randomized to one of 10 unique sequences of two-night treatment with oral almorexant 25, 50, 100, or 200 mg capsules, or matching placebo. The primary efficacy endpoint was polysomnography (PSG)-determined mean wake time after sleep onset (WASO). Secondary and exploratory efficacy endpoints were also assessed.

Results

112 patients were randomized (mean [SD] age 72.1 [5.0] years; 69.9% female). Significant, dose-related improvements (reductions) in mean WASO were observed with almorexant. Least-squares mean (95% CI) treatment effects in the almorexant 200, 100, 50, and 25 mg dose groups versus placebo were -46.5 minutes (-53.0, -39.9; p < .0001), -31.4 minutes (-38.0, -24.9; p < .0001), -19.2 minutes (-25.7, -12.6; p < .0001), and -10.4 minutes (-17.0, -3.9; p = .0018), respectively. Mean total sleep time was significantly increased with each almorexant dose (mean increases versus placebo ranged 55.1-14.3 minutes; p < .0001 for each dose). Latency to persistent sleep was statistically significantly reduced only with almorexant 200 mg versus placebo (mean [95% CI] treatment effect -10.2 minutes, [-15.4, -5.0]; p = .0001). No unexpected safety concerns were identified. Adverse events were similar between all almorexant dose groups and placebo.

Conclusions

Two-night oral administration of almorexant was effective and well tolerated in treating primary insomnia in elderly patients.

Orexin OX2 Receptor Antagonists as Sleep Aids

The discovery of the orexin system represents the single major progress in the sleep field of the last three to four decades. The two orexin peptides and their two receptors play a major role in arousal and sleep/wake cycles. Defects in the orexin system lead to narcolepsy with cataplexy in humans and dogs and can be experimentally reproduced in rodents. At least six orexin receptor antagonists have reached Phase II or Phase III clinical trials in insomnia, five of which are dual orexin receptor antagonists (DORAs) that target both OX1 and OX2 receptors (OX2Rs). All clinically tested DORAs induce and maintain sleep: suvorexant, recently registered in the USA and Japan for insomnia, represents the first hypnotic principle that acts in a completely different manner from the current standard medications. It is clear, however, that in the clinic, all DORAs promote sleep primarily by increasing rapid eye movement (REM) and are almost devoid of effects on slow-wave (SWS) sleep. At present, there is no consensus on whether the sole promotion of REM sleep has a negative impact in patients suffering from insomnia. However, sleep onset REM (SOREM), which has been documented with DORAs, is clearly an undesirable effect, especially for narcoleptic patients and also in fragile populations (e.g. elderly patients) where REM-associated loss of muscle tone may promote an elevated risk of falls. Debate thus remains as to the ideal orexin agent to achieve a balanced increase in REM and non-rapid eye movement (NREM) sleep. Here, we review the evidence that an OX2R antagonist should be at least equivalent, or perhaps superior, to a DORA for the treatment of insomnia. An OX2R antagonist may produce more balanced sleep than a DORA. Rodent sleep experiments show that the OX2R is the primary target of orexin receptor antagonists in sleep modulation. Furthermore, an OX2R antagonist should, in theory, have a lower narcoleptic/cataplexic potential. In the clinic, the situation remains equivocal, since OX2R antagonists are in early stages: MK-1064 has completed Phase I, and MIN202 is currently in clinical Phase II/III trials. However, data from insomnia patients have not yet been released. Promotional material suggests that balanced sleep is indeed induced by MIN-202, whereas in volunteers MK-1064 has been reported to act similarly to DORAs.

Efficacy and safety of almorexant in adult chronic insomnia: a randomized placebo-controlled trial with an active reference

BACKGROUND AND OBJECTIVES

The orally active dual OX₁R and OX₂R antagonist, almorexant, targets the orexin system for the treatment of primary insomnia. This clinical trial assessed the effect of almorexant on sleep maintenance and other sleep endpoints, and its safety and tolerability in adults.

PATIENTS AND METHODS

Prospective, randomized, double-blind, placebo-controlled, active referenced trial in male and female adults aged 18-64 years with chronic, primary insomnia. Patients were randomized 1:1:1:1 to receive placebo, almorexant 100 mg, almorexant 200 mg, or zolpidem 10 mg (active reference) for 16 days. Primary efficacy assessments were objective (polysomnography-measured) and subjective (patient-recorded) wake time after sleep onset (WASO). Further sleep variables were also evaluated.

RESULTS

From 709 randomized patients, 707 (mean age 45.4 years; 61.7% female) received treatment and 663 (93.8%) completed the study. A significant decrease versus placebo in median objective WASO was observed with almorexant 200 mg at the start and end of randomized treatment (-26.8 min and -19.5 min, respectively; both p < 0.0001); subjective WASO also decreased over the two-week treatment period (p = 0.0006). Objective and subjective total sleep time (TST) were increased with almorexant 200 mg (p < 0.0001). Almorexant 200 mg significantly reduced objective and subjective latency to persistent sleep and latency to sleep onset at initiation of therapy, and provided longer duration of sleep stages with no suppression of slow-wave sleep. No impaired next-day performance, rebound insomnia, or withdrawal effects were observed. Adverse events were similar with almorexant and placebo.

CONCLUSION

Almorexant reduced time to sleep onset and maintained sleep without residual effects on next-day performance or safety concerns. This study provides further support for the role of the endogenous orexin system in insomnia disorder. CLINICALTRIALS.

GOV REGISTRATION

NCT00608985.

Effects of a single, oral 60 mg caffeine dose on attention in healthy adult subjects

Caffeine induces positive effects on sustained attention, although studies assessing the acute effects of low caffeine dose (<75 mg) on sustained attention are limited and use short-term tests. Therefore, we investigated the acute effects of a 60 mg dose of caffeine on sustained attention in tests lasting up to 45 minutes using 82 low or non-caffeine-consuming healthy male ( n=41) and female ( n=41) adults aged between 40 and 60 years. Vigilance was measured using Mackworth Clock test, Rapid Visual Information Processing Test, adaptive tracking test, saccadic eye movement and attention switch test. Effects on mood and fatigue were analysed using Bond and Lader and Caffeine Research visual analogue scales, and Samn-Perelli questionnaire. Saliva sampling was performed for both compliance and caffeine pharmacokinetic analysis. Administration of a 60 mg caffeine dose resulted in a significant improvement in sustained attention compared with the placebo. Also a significantly improved peak saccadic velocity and reaction time performance was found, and decreased error rate. Significantly increased feelings of alertness, contentment and overall mood after caffeine treatment compared with placebo were observed. This study demonstrated that in healthy adult subjects oral administration of a single 60 mg caffeine dose elicited a clear enhancement of sustained attention and alertness, measured both in multiple objective performances and in subjective scales.

Orexin-1 receptor signalling in the prelimbic cortex and ventral tegmental area regulates cue-induced reinstatement of ethanol-seeking in iP rats

Orexins (hypocretins) are hypothalamic neuropeptides that innervate the entire neuraxis, including the prelimbic cortex and ventral tegmental area and have been implicated in ethanol-seeking behaviour. The present study aimed to use the orexin-1 (OX1 ) receptor antagonist SB-334867 to examine the role of prelimbic cortex and ventral tegmental area OX1 receptors in cue-induced reinstatement of ethanol-seeking. Ethanol-preferring rats (iP) rats were trained to self-administer ethanol (10 percent v/v, FR3) or sucrose (0.2-1 percent w/v, FR3) in the presence of reward-associated cues before being implanted with indwelling guide cannulae. Rats then underwent extinction training for 11 days. On test days, rats were given a microinjection of vehicle or SB-334867 (3 μg/side) and presented with reward-associated cues to precipitate reinstatement. Results show SB-334867 infused into the prelimbic cortex attenuated cue-induced reinstatement of ethanol-seeking, but not sucrose-seeking. OX1 antagonism in the ventral tegmental area also attenuated cue-induced reinstatement of ethanol-seeking. These findings suggest that OX1 receptors located in the prelimbic cortex and ventral tegmental area are part of a circuit driving cue-mediated ethanol-seeking behaviour.

The Dual Hypocretin Receptor Antagonist Almorexant is Permissive for Activation of Wake-Promoting Systems

The dual hypocretin receptor (HcrtR) antagonist almorexant (ALM) may promote sleep through selective disfacilitation of wake-promoting systems, whereas benzodiazepine receptor agonists (BzRAs) such as zolpidem (ZOL) induce sleep through general inhibition of neural activity. Previous studies have indicated that HcrtR antagonists cause less-functional impairment than BzRAs. To gain insight into the mechanisms underlying these differential profiles, we compared the effects of ALM and ZOL on functional activation of wake-promoting systems at doses equipotent for sleep induction. Sprague-Dawley rats, implanted for EEG/EMG recording, were orally administered vehicle (VEH), 100 mg/kg ALM, or 100 mg/kg ZOL during their active phase and either left undisturbed or kept awake for 90 min after which their brains were collected. ZOL-treated rats required more stimulation to maintain wakefulness than VEH- or ALM-treated rats. We measured Fos co-expression with markers for wake-promoting cell groups in the lateral hypothalamus (Hcrt), tuberomammillary nuclei (histamine; HA), basal forebrain (acetylcholine; ACh), dorsal raphe (serotonin; 5HT), and singly labeled Fos(+) cells in the locus coeruleus (LC). Following SD, Fos co-expression in Hcrt, HA, and ACh neurons (but not in 5HT neurons) was consistently elevated in VEH- and ALM-treated rats, whereas Fos expression in these neuronal groups was unaffected by SD in ZOL-treated rats. Surprisingly, Fos expression in the LC was elevated in ZOL- but not in VEH- or ALM-treated SD animals. These results indicate that Hcrt signaling is unnecessary for the activation of Hcrt, HA, or ACh wake-active neurons, which may underlie the milder cognitive impairment produced by HcrtR antagonists compared to ZOL.

Therapeutic implications of the choroid plexus-cerebrospinal fluid interface in neuropsychiatric disorders

The choroid plexus (CP) comprises an epithelial monolayer that forms an important physical, enzymatic and immunologic barrier, called the blood-cerebrospinal fluid barrier (BCSFB). It is a highly vascularized organ located in the brain ventricles that is key in maintaining brain homeostasis as it produces cerebrospinal fluid (CSF) and has other important secretory functions. Furthermore, the CP-CSF interface plays a putative role in neurogenesis and has been implicated in neuropsychiatric diseases such as the neurodevelopmental disorders schizophrenia and autism. A role for this CNS border was also implicated in sleep disturbances and chronic and/or severe stress, which are risk factors for the development of neuropsychiatric conditions. Understanding the mechanisms by which disturbance of the homeostasis at the CP-CSF interface is involved in these different chronic low-grade inflammatory diseases can give new insights into therapeutic strategies. Hence, this review discusses the different roles that have been suggested so far for the CP in these neuropsychiatric disorders, with special attention to potential therapeutic applications.

Orexin Receptor Antagonists: New Therapeutic Agents for the Treatment of Insomnia

Since its discovery in 1998, the orexin system, composed of two G-protein coupled receptors, orexins 1 and 2, and two neuropeptide agonists, orexins A and B, has captured the attention of the scientific community as a potential therapeutic target for the treatment of obesity, anxiety, and sleep/wake disorders. Genetic evidence in rodents, dogs, and humans was revealed between 1999 and 2000, demonstrating a causal link between dysfunction or deletion of the orexin system and narcolepsy, a disorder characterized by hypersomnolence during normal wakefulness. These findings encouraged efforts to discover agonists to treat narcolepsy and, alternatively, antagonists to treat insomnia. This perspective will focus on the discovery and development of structurally diverse orexin antagonists suitable for preclinical pharmacology studies and human clinical trials. The work described herein culminated in the 2014 FDA approval of suvorexant as a first-in-class dual orexin receptor antagonist for the treatment of insomnia.

Neurobiology and sleep disorders in cluster headache

Cluster headache is characterized by unilateral attacks of severe pain accompanied by cranial autonomic features. Apart from these there are also sleep-related complaints and strong chronobiological features. The interaction between sleep and headache is complex at any level and evidence suggests that it may be of critical importance in our understanding of primary headache disorders. In cluster headache several interactions between sleep and the severe pain attacks have already been proposed. Supported by endocrinological and radiological findings as well as the chronobiological features, predominant theories revolve around central pathology of the hypothalamus. We aimed to investigate the clinical presentation of chronobiological features, the presence of concurrent sleep disorders and the relationship with particular sleep phases or phenomena, the possible role of hypocretin as well as the possible involvement of cardiac autonomic control. We conducted a questionnaire survey on 275 cluster headache patients and 145 controls as well an in-patient sleep study including 40 CH-patients and 25 healthy controls. The findings include: A distinct circannual connection between cluster occurrence and the amount of daylight, substantially poorer sleep quality in patients compared to controls which was present not only inside the clusters but also outside, affected REM-sleep in patients without a particular temporal connection to nocturnal attacks, equal prevalence of sleep apnea in both patient and control groups, reduced levels of hypocretin-1 in the cerebrospinal fluid of patients and finally a blunted response to the change from supine to tilted position in the head-up tilt table test indicating a weakened sympathoexcitatory or stronger parasympathetic drive. Overall, these findings support a theory of involvement of dysregulation in hypothalamic and brainstem nuclei in cluster headache pathology. Further, it is made plausible that the headache attacks are but one aspect of a more complex syndrome of central dysregulation manifesting as sleep-related complaints, sub-clinical autonomic dysregulation and of course the severe attacks of unilateral headache. Future endeavors should focus on pathological changes which persist in the attack-free periods but also heed the possibility of long-lived, cluster-induced pathology.

Suvorexant for the treatment of insomnia

Suvorexant (Belsorma(®)) is the first orexin receptor antagonist approved by the US FDA (August 2014) for insomnia treatment. Following comprehensive Phase II/III studies, with up to 12 months of treatment in adult and elderly patients, there is little doubt that suvorexant induces and maintains sleep. However, the FDA and sponsor disagreed about effective versus safe doses (November 2012). The FDA considered that 5-15 mg were efficient and probably safe, whereas the sponsors had proposed 15-40 mg. The final approved doses are 5, 10, 15 and 20 mg. The major issues are next-morning somnolence and safety as seen in driving tests, with possible signs of muscle weakness, weird dreams, sleep walking, other nighttime behaviors and suicidal ideation. Despite its limitations, suvorexant's market entry offers a truly novel treatment for insomnia, paving the way for follow-up compounds and opening therapeutic avenues in other disorders for orexin receptor modulating compounds.

Discovery of (1R,2S)-2-{[(2,4-Dimethylpyrimidin-5-yl)oxy]methyl}-2-(3-fluorophenyl)-N-(5-fluoropyridin-2-yl)cyclopropanecarboxamide (E2006): A Potent and Efficacious Oral Orexin Receptor Antagonist

The orexin/hypocretin receptors are a family of G protein-coupled receptors and consist of orexin-1 (OX1) and orexin-2 (OX2) receptor subtypes. Orexin receptors are expressed throughout the central nervous system and are involved in the regulation of the sleep/wake cycle. Because modulation of these receptors constitutes a promising target for novel treatments of disorders associated with the control of sleep and wakefulness, such as insomnia, the development of orexin receptor antagonists has emerged as an important focus in drug discovery research. Here, we report the design, synthesis, characterization, and structure-activity relationships (SARs) of novel orexin receptor antagonists. Various modifications made to the core structure of a previously developed compound (-)-5, the lead molecule, resulted in compounds with improved chemical and pharmacological profiles. The investigation afforded a potential therapeutic agent, (1R,2S)-2-{[(2,4-dimethylpyrimidin-5-yl)oxy]methyl}-2-(3-fluorophenyl)-N-(5-fluoropyridin-2-yl)cyclopropanecarboxamide (E2006), an orally active, potent orexin antagonist. The efficacy was demonstrated in mice in an in vivo study by using sleep parameter measurements.

Current Phase II investigational therapies for insomnia

INTRODUCTION

Insomnia is typified by a difficulty in sleep initiation, maintenance and/or quality (non-restorative sleep) resulting in significant daytime distress.

AREAS COVERED

This review summarizes the available efficacy and safety data for drugs currently in the pipeline for treating insomnia. Specifically, the authors performed MEDLINE and internet searches using the keywords 'Phase II' and 'insomnia'. The drugs covered target GABAA (zaleplon-CR, lorediplon, EVT-201), orexin (filorexant, MIN-202), histamine-H1 (LY2624803), serotonin 5-HT2A (ITI-007), melatonin/serotonin5-HT1A (piromelatine) and melatonin (indication expansions of prolonged-release melatonin and tasimelteon for pediatric sleep and circadian rhythm disorders) receptors.

EXPERT OPINION

Low-priced generic environments and high development costs limit the further development of drugs that treat insomnia. However, the bidirectional link between sleep and certain comorbidities may encourage development of specific drugs for comorbid insomnia. New insomnia therapies will most likely move away from GABAAR receptors' modulation to more subtle neurological pathways that regulate the sleep-wake cycle.

Absence of pharmacokinetic and pharmacodynamic interactions between almorexant and warfarin in healthy subjects

Background and Objective

Almorexant is the first representative of the new class of orexin receptor antagonists, which could become a new treatment option for insomnia. The present study investigated the potential interaction between almorexant and warfarin.

Methods

In this open-label, two-way crossover, drug–drug interaction study, healthy male subjects received, in a randomized fashion, almorexant 200 mg once daily for 10 days and a single dose of 25 mg warfarin co-administered on day 5 (treatment A) and a single dose of 25 mg warfarin on day 1 (treatment B). Serial blood samples for warfarin pharmacokinetics and pharmacodynamics were drawn during both treatments.

Results

Of the 14 enrolled subjects, one withdrew due to an adverse event and 13 completed the study. Almorexant had no effect on the pharmacokinetics of warfarin. The geometric mean ratios (90 % confidence interval) for the area under the plasma concentration–time curve to infinity (AUC_0–∞) of S- and R-warfarin were 0.99 (0.89, 1.09) and 1.05 (0.95, 1.16), respectively, and for the maximum plasma concentration (C_max) were 0.99 (0.86, 1.14) and 1.00 (0.88, 1.13), respectively. The main pharmacodynamic variable was the AUC for the international normalized ratio (AUC_INR). Almorexant had no effect on this variable as demonstrated by a geometric mean ratio of 0.99 (0.82, 1.19). Secondary pharmacodynamic variables including maximum effect (E_max), the time to the maximum INR, and factor VII plasma concentrations were also not affected by almorexant.

Conclusion

No dose adjustment of warfarin is necessary when concomitantly administered with almorexant.

Design, synthesis, and structure-activity relationships of a series of novel N-aryl-2-phenylcyclopropanecarboxamide that are potent and orally active orexin receptor antagonists

Herein we describe the design, synthesis, and structure-activity relationships (SARs) of a novel phenylcyclopropane series represented by 7 and 33 b as antagonists of orexin 1 and orexin 2 receptors. With 4 serving as the initial lead for the development of orexin antagonists, exploration of SAR resulted in improved binding affinity for orexin 1 and orexin 2 receptors. Among the synthesized compounds, 33 b ((-)-N-(5-cyanopyridin-2-yl)-2-[(3,4-dimethoxyphenyl)oxymethyl]-2-phenylcyclopropanecarboxamide) exhibited potent in vitro activity and oral efficacy in animal sleep measurement experiments. The results of our study suggest that compound 33 b may serve as a valuable template for the development of new orexin receptor antagonists.

Randomized controlled trial of the orexin receptor antagonist filorexant for migraine prophylaxis

BACKGROUND

This study explored whether antagonism of orexin receptors might be an effective mechanism for migraine prevention.

METHODS

We conducted a randomized, double-blind, placebo-controlled, pilot trial. Patients experiencing four to 14 days with migraine during a one-month baseline period were randomized to the orexin receptor antagonist filorexant 10 mg nightly or placebo for three months. Efficacy was assessed by mean monthly migraine days (headache plus at least one associated migraine symptom) and headache days. Safety and tolerability were assessed by adverse event reports and laboratory tests.

RESULTS

Of 120 patients treated with filorexant and 115 treated with placebo, 97 (81%) and 101 (88%), respectively, completed the trial. There was no statistically significant difference between treatments for change from baseline in mean monthly migraine days (filorexant = -1.7, placebo = -1.3, difference = -0.4 (95% CI: -1.3, 0.4)) or headache days (filorexant = -1.7, placebo = -1.2, difference = -0.5 (95% CI: -1.4, 0.4)). Filorexant was generally well tolerated but was associated with a higher proportion of patients who reported adverse events than placebo (47% vs 37%), particularly somnolence (13% vs 4%).

CONCLUSIONS

These data fail to provide evidence that antagonism of orexin receptors with filorexant, when administered at night, is effective for migraine prophylaxis.

Pharmacokinetic and pharmacodynamic interactions between almorexant, a dual orexin receptor antagonist, and desipramine

Almorexant is a dual orexin receptor antagonist (DORA) with sleep-enabling effects in humans. Insomnia is often associated with mental health problems, including depression. Hence, potential interactions with antidepressants deserve attention. Desipramine was selected as a model drug because it is mainly metabolized by CYP2D6, which is inhibited by almorexant in vitro. A single-center, randomized, placebo-controlled, two-way crossover study in 20 healthy male subjects was conducted to evaluate the pharmacokinetic and pharmacodynamic interactions between almorexant and desipramine. Almorexant 200mg or matching placebo (double-blind) was administered orally once daily in the morning for 10 days, and a single oral dose of 50mg desipramine (open-label) was administered on Day 5. Almorexant increased the exposure to desipramine 3.7-fold, suggesting that almorexant is a moderate inhibitor of desipramine metabolism through inhibition of CYP2D6. Conversely, desipramine showed no relevant effects on the pharmacokinetics of almorexant. Pharmacodynamic evaluations indicated that almorexant alone reduced visuomotor coordination, postural stability, and alertness, and slightly increased calmness. Desipramine induced a reduction in subjective alertness and an increase in pupil/iris ratio. Despite the increase in exposure to desipramine, almorexant and desipramine in combination showed the same pharmacodynamic profile as almorexant alone, except for prolonging reduced alertness and preventing the miotic effect of almorexant. Co-administration also prolonged the mydriatic effect of desipramine. Overall, repeated administration of almorexant alone or with single-dose desipramine was well tolerated. The lack of a relevant interaction with antidepressants, if confirmed for other DORAs, would be a key feature for a safer class of hypnotics.

Orexin/hypocretin based pharmacotherapies for the treatment of addiction: DORA or SORA?

Addiction is a chronic relapsing disorder which presents a significant global health burden and unmet medical need. The orexin/hypocretin system is an attractive potential therapeutic target as demonstrated by the successful clinical trials of antagonist medications like Suvorexant for insomnia. It is composed of two neuropeptides, orexin-A and orexin-B and two excitatory and promiscuous G-protein coupled receptors, OX1 and OX2. Orexins are known to have a variety of functions, most notably in regulating arousal, appetite and reward. The orexins have been shown to have a role in mediating the effects of several drugs of abuse, such as cocaine, morphine and alcohol via projections to key brain regions such as the ventral tegmental area, nucleus accumbens and prefrontal cortex. However, it has not yet been demonstrated whether the dual orexin receptor antagonists (DORAs) under development for insomnia are ideal drugs for the treatment of addiction. The question of whether to use a DORA or single orexin receptor antagonist (SORA) for the treatment of addiction is a key question that will need to be answered in order to maximize the clinical utility of orexin receptor antagonists. This review will examine the role of the orexin/hypocretin system in addiction, orexin-based pharmacotherapies under development and factors affecting the selection of one or both orexin receptors as drug targets for the treatment of addiction.

Advances in the management of insomnia

Insomnia is highly prevalent and associated with considerable morbidity. Several very efficacious treatments, both pharmacologic and non-pharmacologic, exist for the management of insomnia. New modes of delivery and new formulations of existing sedative-hypnotic medications have been introduced. Novel agents are still being developed and tested to arrive at a hypnotic that has limited side effects while still being efficacious. Innovations with respect to behavioral interventions, which are drastically under-utilized, have focused mainly on making these interventions more widely available through dissemination efforts, briefer formats and more accessible platforms.

Formulation development for the orexin receptor antagonist almorexant: assessment in two clinical studies

Almorexant, a dual orexin receptor antagonist, was investigated for the treatment of insomnia. The following observations initiated further formulation development: the active pharmaceutical ingredient (API) was sticking to the apparatus used during tablet compression; almorexant has an absolute bioavailability of 11.2%; and almorexant modestly decreased the latency to persistent sleep by 10.4 minutes in patients. Two randomized crossover studies were performed to investigate the pharmacokinetics of several new formulations in healthy subjects. In study I, the old "sticky" tablet was compared to two new formulations developed to prevent sticking: a qualitatively similar tablet but with a larger API crystal size and a tablet with 30% more excipients as well as a larger API crystal size. This latter formulation was available in two strengths. The geometric mean ratios and 90% confidence interval of the area under the curve (AUC) were within the bioequivalence range of 0.80-1.25 for the different comparisons between formulations. In study II, 100 mg of the reference tablet was compared to 25 and 50 mg of a liquid-filled hard gelatin capsule developed to increase the bioavailability of almorexant. The geometric mean ratios of the maximum concentration and AUC comparing the new 25 and 50 mg capsule formulations to the reference tablet did not exceed 0.25 and 0.50, respectively, indicating that the new capsule formulation did not increase the maximum concentration of or the total exposure to almorexant. In conclusion, a new tablet was developed but formulation development aimed at increasing the bioavailability of almorexant failed.

Assessment of the abuse liability of a dual orexin receptor antagonist: a crossover study of almorexant and zolpidem in recreational drug users

BACKGROUND

Dual orexin receptor antagonists (DORAs) enable initiation and maintenance of sleep in patients with primary insomnia. Blockade of the orexin system has shown reduction of drug-seeking behavior in animal studies, supporting the role of orexin antagonism as a novel approach for treating substance abuse. Since hypnotics are traditionally associated with misuse, a lack of abuse liability of DORAs would offer significant benefits over current therapies for sleep disorders.

METHODS

In this randomized, crossover, proof-of-concept study, single oral doses of the DORA almorexant (200, 400, and 1,000 mg) were administered to healthy subjects with previous non-therapeutic experience with central nervous system depressants and were compared with placebo and single oral doses of zolpidem (20 and 40 mg), a benzodiazepine-like drug. Subjective measures of abuse potential (visual analog scales [VAS], Addiction Research Center Inventory, and Subjective Drug Value) and objective measures (divided attention [DA]) were evaluated over 24 h post-dose in 33 evaluable subjects.

RESULTS

Drug Liking VAS peak effect (E max; primary endpoint) was significantly higher for all doses of almorexant and zolpidem compared with placebo (p<0.001). Almorexant 200 mg showed significantly less 'Drug Liking' than both zolpidem doses (p<0.01), and almorexant 400 mg had smaller effects than zolpidem 20 mg (p<0.05), while almorexant 1,000 mg was not different from either zolpidem dose. Results were similar for other subjective measures, although almorexant generally showed smaller negative and perceptual effects compared with zolpidem. Almorexant also showed less cognitive impairment compared with zolpidem on most DA endpoints.

CONCLUSION

This study in humans investigating single doses of almorexant is the first to explore and show abuse liability of a DORA, a class of compounds that is not only promising for the treatment of sleep disorders, but also of addiction.

Pharmacokinetic interactions between the orexin receptor antagonist almorexant and the CYP3A4 inhibitors ketoconazole and diltiazem

Almorexant, a tetrahydroisoquinoline orexin receptor antagonist and first representative of a new class of compounds for the treatment of insomnia, is a substrate of the cytochrome P450 3A4 isoenzyme (CYP3A4). Two randomized two-way crossover studies were performed in healthy subjects investigating the pharmacokinetic interaction between almorexant and the CYP3A4 inhibitors ketoconazole and diltiazem. When administered as a single dose of 100 mg almorexant during steady state of ketoconazole (400 mg once daily for 14 days) or diltiazem treatment (300 mg once daily for 11 days), the exposure to almorexant was 10.5- and 3.5-fold, respectively, greater when compared with almorexant alone. Exposure to the phenol metabolites M3 and M8 increased in the presence of the CYP3A4 inhibitors, whereas that to M6 (dealkylated metabolite) decreased. Concomitant ketoconazole decreased formation of the dehydrogenated metabolite M5 and diltiazem increased concentrations of this metabolite. Higher almorexant exposure was associated with an increased incidence of typical almorexant-related adverse events such as fatigue (both studies) and somnolence (ketoconazole study only). The present results indicate that dose adaptation must be considered when almorexant would be coadministered with inhibitors of CYP3A4.