Profile of suvorexant in the management of insomnia

Transitioning insomnia patients from zolpidem to lemborexant: A multicenter, open-label study evaluating a next-dose transition approach to insomnia pharmacotherapy

Objective

Few clinical studies have assessed real-world abrupt transitioning between insomnia medications. This study assessed strategies for directly transitioning patients from zolpidem tartrate (ZOL) immediate/extended release to the dual orexin receptor antagonist, lemborexant (LEM).

Methods

This randomized, open-label, multicenter study (Study 312; E2006-A001-312) enrolled 53 adults age ≥18 years with insomnia disorder and ≥1-month history of intermittent (3-4 nights/week) or frequent (≥5 nights/week) ZOL use. Subjects recorded their ZOL use in a 3-week Pretreatment Phase, followed by a 2-week Treatment Phase (TRT; Titration) during which ZOL was discontinued. Intermittent ZOL users transitioned to LEM 5 mg (LEM5), Cohort 1, and frequent ZOL users were randomized 1:1 to LEM5, Cohort 2A, or LEM 10 mg (LEM10), Cohort 2B. One dose adjustment was permitted during the TRT. Subjects completing the TRT could continue LEM in the 12-week Extension Phase (EXT). The primary outcome was proportion of subjects who successfully transitioned and remained on LEM at the end of the TRT.

Results

Most subjects (43 [81.1 %]) successfully transitioned to LEM (9 [90 %], 17 [81.0 %], and 17 [77.3 %] in Cohorts 1, 2A, and 2B, respectively). By the end of the EXT, 66.7 % in Cohort 1 and 60.0 % in Cohort 2A up-titrated to LEM10, whereas 41.2 % in Cohort 2B down-titrated to LEM5; 61.0 % were receiving LEM10 at study end. At the end of the TRT, more subjects taking LEM reported that it helped them return to sleep after waking, compared with those taking ZOL (71.7 % vs. 49.1 %). There were no important differences between treatments regarding how subjects reported feeling as they fell asleep. Most of the treatment-emergent adverse events with LEM were mild in severity.

Conclusions

Most subjects transitioned successfully to LEM from ZOL (intermittent or frequent use). LEM was well tolerated.

Is schedule IV suvorexant an appropriate reference drug of abuse to use in preclinical abuse liability testing in the rat?

The abuse potential of novel CNS-active drug candidates with low specificity for known receptors involved in abuse might be complex to test preclinically relative to an appropriate reference drug of abuse. Suvorexant, a Schedule IV dual orexin receptor antagonist was investigated for its potential use as a reference drug in Drug Discrimination Learning (DDL) studies. Firstly, toxicokinetic properties of suvorexant were determined in male and female rats after single oral doses of 160 and 325 mg/kg in MC and PEG400. Thereafter the subjective effects of suvorexant at 325 mg/kg versus vehicle were evaluated in a DDL paradigm and plasma exposures were measured. Mean maximum plasma exposures in male rats after a single dose of 325 mg/kg suvorexant were 2.5- (MC) to 10.5-fold (PEG400) the human exposure at supratherapeutic doses of 40 mg q.d. (Cmax:1.1 μM), and 4.9- (MC) to 20.8-fold (PEG400) the approved maximum human efficacious dose (20 mg q.d.; 0.557 μM). Training male rats at 325 mg/kg in the DDL study however did not result in discriminative stimulus generalisation versus respective vehicles. Suvorexant, a Schedule IV dual orexin receptor antagonist failed to serve as a robust reference drug of abuse in the DDL paradigm in rats despite appropriate exposures.

In Vitro and In Vivo Evaluation of Pellotine: A Hypnotic Lophophora Alkaloid

Quality of life is often reduced in patients with sleep-wake disorders. Insomnia is commonly treated with benzodiazepines, despite their well-known side effects. Pellotine (1), a Lophophora alkaloid, has been reported to have short-acting sleep-inducing properties in humans. In this study, we set out to evaluate various in vitro and in vivo properties of 1. We demonstrate that 1 undergoes slow metabolism; e.g. in mouse liver microsomes 65% remained, and in human liver microsomes virtually no metabolism was observed after 4 h. In mouse liver microsomes, two phase I metabolites were identified: 7-desmethylpellotine and pellotine-N-oxide. In mice, the two diastereomers of pellotine-O-glucuronide were additionally identified as phase II metabolites. Furthermore, we demonstrated by DESI-MSI that 1 readily enters the central nervous system of rodents. Furthermore, radioligand-displacement assays showed that 1 is selective for the serotonergic system and in particular the serotonin (5-HT)1D, 5-HT6, and 5-HT7 receptors, where it binds with affinities in the nanomolar range (117, 170, and 394 nM, respectively). Additionally, 1 was functionally characterized at 5-HT6 and 5-HT7, where it was found to be an agonist at the former (EC50 = 94 nM, Emax = 32%) and an inverse agonist at the latter (EC50 = 291 nM, Emax = -98.6). Finally, we demonstrated that 1 dose-dependently decreases locomotion in mice, inhibits REM sleep, and promotes sleep fragmentation. Thus, we suggest that pellotine itself, and not an active metabolite, is responsible for the hypnotic effects and that these effects are possibly mediated through modulation of serotonergic receptors.

Clinical specificity profile for novel rapid acting antidepressant drugs

Mood disorders are recurrent/chronic diseases with variable clinical remission rates. Available antidepressants are not effective in all patients and often show a relevant response latency, with a range of adverse events, including weight gain and sexual dysfunction. Novel rapid agents were developed with the aim of overcoming at least in part these issues. Novel drugs target glutamate, gamma-aminobutyric acid, orexin, and other receptors, providing a broader range of pharmacodynamic mechanisms, that is, expected to increase the possibility of personalizing treatments on the individual clinical profile. These new drugs were developed with the aim of combining a rapid action, a tolerable profile, and higher effectiveness on specific symptoms, which were relatively poorly targeted by standard antidepressants, such as anhedonia and response to reward, suicidal ideation/behaviours, insomnia, cognitive deficits, and irritability. This review discusses the clinical specificity profile of new antidepressants, namely 4-chlorokynurenine (AV-101), dextromethorphan-bupropion, pregn-4-en-20-yn-3-one (PH-10), pimavanserin, PRAX-114, psilocybin, esmethadone (REL-1017/dextromethadone), seltorexant (JNJ-42847922/MIN-202), and zuranolone (SAGE-217). The main aim is to provide an overview of the efficacy/tolerability of these compounds in patients with mood disorders having different symptom/comorbidity patterns, to help clinicians in the optimization of the risk/benefit ratio when prescribing these drugs.

Updates and confounding factors in delayed sleep-wake phase disorder

Delayed sleep-wake phase disorder (DSWPD) is a circadian rhythm sleep disorder characterised by a delay in the main sleep period, with patients experiencing difficulty getting to sleep and waking up at socially appropriate times. This often causes insomnia and compromised sleep, results in impairment to daytime function and is associated with a range of comorbidities. Besides interventions aimed at ameliorating symptoms, there is good evidence supporting successful phase advancement with bright light therapy or melatonin administration. However, no treatment to date addresses the tendency to phase delay, which is a common factor amongst the various contributing causes of DSWPD. Circadian phase markers such as core body temperature and circulating melatonin typically correlate well with sleep timing in healthy patients, but numerous variations exist in DSWPD patients that can make these unpredictable for use in diagnostics. There is also increasing evidence that, on top of problems with the circadian cycle, sleep homeostatic processes actually differ in DSWPD patients compared to controls. This naturally has ramifications for management but also for the current approach to the pathogenesis itself in which DSWPD is considered a purely circadian disorder. This review collates what is known on the causes and treatments of DSWPD, addresses the pitfalls in diagnosis and discusses the implications of current data on modified sleep homeostasis, making clinical recommendations and directing future research.

Different doses of dual orexin receptor antagonists in primary insomnia: a Bayesian network analysis

Background: Systematic comparisons of the doses of the Food and Drug Administration (FDA)-approved dual orexin receptor antagonists (DORAs) for people with insomnia are limited. Methods: PubMed, Embase, Cochrane Library, and Clinicaltrials. gov were systematically searched to identify relevant studies published before 31 October 2022. We assessed the certainty of evidence using the confidence in network meta-analysis (CINeMA) framework. Results: We pooled 7257 participants from 9 randomized controlled trials (RCTs). Moderate to high certainty evidence demonstrated suvorexant (20 and 40 mg) and daridorexant (10 and 50 mg) as the most effective in latency to persistent sleep (LPS) reduction. Lemborexant at 5 and 10 mg was the most effective in subjective sleep onset time (sTSO) reduction. For wake time after sleep onset (WASO), all drugs except daridorexant 5 mg were more effective than placebo. Lemborexant 5 mg was among the best in subjective WASO (sWASO) (moderate to high certainty) and had the highest surface under the curve ranking area (SUCRA) values for sWASO (100%). For total sleep time (TST), suvorexant and daridorexant, except the respective minimum doses, were more effective than placebo, while suvorexant 40 mg and lemborexant 10 mg may have been the most effective for subjective TST (sTST) (low to very low certainty). Suvorexant 40 mg (RR 1.09), suvorexant 80 mg (RR 1.65), and daridorexant 25 mg (RR 1.16) showed a higher safety risk than placebo. Conclusion: Suvorexant 20 mg, lemborexant 5 mg, lemborexant 10 mg, and daridorexant 50 mg represent suitable approaches for insomnia. Clinical Trial Registration: clinicaltrials.gov, PROSPERO (CRD42022362655).

How Would You Manage This Patient With Chronic Insomnia? : Grand Rounds Discussion From Beth Israel Deaconess Medical Center

Insomnia, which is characterized by persistent sleep difficulties in association with daytime dysfunction, is a common concern in clinical practice. Chronic insomnia disorder is defined as symptoms that occur at least 3 times per week and persist for at least 3 months. The American Academy of Sleep Medicine (AASM) published recent guidelines on behavioral and psychological treatment as well as pharmacologic therapy for chronic insomnia disorder. Regarding behavioral and psychological approaches, the only intervention strongly recommended was multicomponent cognitive behavioral therapy for insomnia. Regarding pharmacologic treatment, the AASM, based on weak evidence, suggested a limited number of medications that might be useful and others that probably are not. Here, 2 clinicians with expertise in sleep disorders-one a clinical psychologist and the other a physician-debate the management of a patient with chronic insomnia who has been treated with medications. They discuss the role of behavioral and psychological interventions and pharmacologic therapy for chronic insomnia and how the primary care practitioner should approach such a patient.

Daridorexant for the treatment of insomnia disorder: findings and implications

PURPOSE

The involvement of the orexin system in the physiopathology of insomnia has been rapidly increasing in understanding. In this sense, daridorexant was the third orexin receptor antagonist approved by the FDA in January 2022. This review aims to summarize the chemistry, pharmacodynamics, pharmacokinetics, efficacy, safety, and tolerability profile of daridorexant for the treatment of insomnia disorder.

METHODS

We performed a review of daridorexant for the treatment of insomnia disorder. The search was carried out in Medline via PubMed, Embase, and clinical trials, up to March 2022.

RESULTS

Daridorexant 25 and 50 mg had more significant improvement for the wake after sleep onset (WASO), latency to persistent sleep (LPS), and subjective total sleep time (sTST) than placebo. In addition, daridorexant 50 mg was better for Insomnia Daytime Symptoms and Impacts Questionnaire (IDSIQ) than placebo. The most common adverse events were nasopharyngitis and headache.

CONCLUSION

Daridorexant was efficacious and safe. Studies that evaluate the long-term safety and compare daridorexant with benzodiazepines, benzodiazepine receptor agonists, sedative antidepressants, and other orexin receptor antagonists are required.

Suvorexant in the Treatment of Difficulty Falling and Staying Asleep (Insomnia)

Purpose of Review

Insomnia affects more than 10% of the population and causes significant discomfort and disability. Suvorexant is an orexin receptor antagonist that specifically targets the wake-sleep cycle. This review summarizes recent and seminal evidence in the biological and physiological evidence of insomnia, the mechanism of action of suvorexant in treating insomnia, and clinical evidence regarding its use.

Recent Findings

There is no single clear diagnosis for insomnia, and thus prevalence is not entirely clear, but it is estimated to affect 10%-30% of the adult population. Comorbidities include obesity, diabetes, and various psychiatric conditions, and insomnia likely has a contributing role in these conditions. Insomnia, by definition, impacts sleep quality and also wakefulness, including academic success and work efficiency. Insomnia is likely related to genetic susceptibility and a triggering event, leading to hyper-arousal states and functional brain disturbances. This leads to hyperactivity of the hypothalamic-pituitary-adrenal axis, over-secretion of corticotropin-releasing factor, and aberrancy in neurotransmitter release. Though several pharmacological options exist for the treatment of insomnia, there is equivocal data regarding their efficacy or limits to their use due to side effects and contraindications. Suvorexant is a novel dual orexin receptor antagonist, which is shown to improve sleep by reducing arousals. Unlike classical therapeutics, suvorexant does not alter the sleep profile; it prolongs the time spent in each sleep state. Though it may cause some somnolence, it is milder than reported with other drugs.

Summary

Multiple clinical studies support the use of suvorexant in insomnia. In primary insomnia, suvorexant is effective (over placebo), as measured by polysomnography and reported by patients, in both attaining and maintaining sleep. Similar, albeit to a smaller degree, results were found in secondary insomnia. Suvorexant carries two significant advantages over existing therapies; it has a much better safety profile in approved doses, and it preserves natural sleep architecture, thus promoting more restful sleep and recovery. Unfortunately, data exists mostly for suvorexant versus placebo, and head-to-head trials with common hypnotics are needed to assess the true efficacy of suvorexant over the alternatives. And while tolerance is less likely to develop, close monitoring of post-marketing data is required to evaluate for long term adverse events and efficacy.

Hypocretin/Orexin Receptor Pharmacology and Sleep Phases

The hypocretins/orexins are two excitatory neuropeptides, alternately called HCRT1 or orexin-A and HCRT2 or orexin-B, that are the endogenous ligands for two G-protein-coupled receptors, HCRTR1/OX1R and HCRTR2/OX2R. Shortly after the discovery of this system, degeneration of hypocretin/orexin-producing neurons was implicated in the etiology of the sleep disorder narcolepsy. The involvement of this system in a disorder characterized by the loss of control over arousal state boundaries also suggested its role as a critical component of endogenous sleep-wake regulatory circuitry. The broad projections of the hypocretin/orexin-producing neurons, along with differential expression of the two receptors in the projection fields of these neurons, suggest distinct roles for these receptors. While HCRTR1/OX1R is associated with regulation of motivation, reward, and autonomic functions, HCRTR2/OX2R is strongly linked to sleep-wake control. The association of hypocretin/orexin with these physiological processes has led to intense interest in the therapeutic potential of compounds targeting these receptors. Agonists and antagonists for the hypocretin/orexin receptors have shown potential for the treatment of disorders of excessive daytime somnolence and nocturnal hyperarousal, respectively, with the first antagonists approved by the US Food and Drug Administration (FDA) in 2014 and 2019 for the treatment of insomnia. These and related compounds have also been useful tools to advance hypocretin/orexin neurobiology.

Evaluating lemborexant for the treatment of insomnia

INTRODUCTION

Insomnia is a complex sleep disorder that compromises quality of life and affects approximately 10% of the general population. Insomnia, defined as trouble initiating or maintaining sleep associated with impaired daytime function or distress, is treated using a comprehensive approach comprised of cognitive behavioral therapy and pharmacotherapy. Lemborexant, a dual orexin receptor antagonist, is a new pharmacotherapeutic option recently approved for the treatment of insomnia.

AREAS COVERED

Here, the authors describe lemborexant, assess its efficacy and safety profile in clinical trials, and evaluate its role in the current insomnia treatment landscape.

EXPERT OPINION

Lemborexant may offer an improved treatment option compared with other pharmacotherapies for insomnia because it is effective both over the long term and over a wide range of outcome measures. Importantly, lemborexant improves latency to sleep onset and sleep maintenance and is able to help people who experience early morning awakenings. Safety data reveal that lemborexant has minimal residual effects on morning alertness or next day function, and that patients are able to respond to an external auditory stimulus in the middle of the night. In conclusion, lemborexant represents a new, effective, and well-tolerated medication for patients with insomnia.

Lack of residual morning effects of lemborexant treatment for insomnia: summary of findings across 9 clinical trials

OBJECTIVES

Residual next-day effects of sleep-promoting drugs are common and an important safety issue. Lemborexant is a dual orexin receptor antagonist approved in the United States and Japan for treatment of insomnia in adults. We evaluated the potential of lemborexant for residual morning and next-day effects, including somnolence, based on lemborexant clinical study findings.

METHODS

This paper reports findings from 9 lemborexant clinical studies that incorporated next-day assessments of residual drug effects, based on published findings and data on file. Results are reported for healthy subjects or subjects with insomnia disorder treated with lemborexant 5 mg/day or 10 mg/day, placebo, or active comparator before bedtime. Outcomes assessed included next-morning postural stability (body sway measured by ataxiameter), cognitive performance (Cognitive Performance Assessment Battery), impact on driving (standard deviation of lateral position during highway driving test), subjective sleepiness (sleep diary entries), and adverse events of somnolence.

RESULTS

Change from baseline in postural stability the morning after lemborexant administration did not differ from placebo. Among 4 Cognitive Performance Assessment Battery measures, only power of attention declined significantly more with lemborexant treatment compared with placebo in 1 of 2 studies, whereas zolpidem differed from placebo on multiple measures. On the highway-driving test, lemborexant did not significantly impair driving performance versus placebo, however, zopiclone did differ. In large phase 3 trials, next-morning sleep diary ratings showed significantly greater alertness with lemborexant compared with placebo after up to 6 months of treatment. As expected, somnolence was the most common adverse event reported with lemborexant treatment. Somnolence was typically mild to moderate in severity and rarely caused discontinuation of study drug.

CONCLUSION

Across 9 clinical studies, lemborexant did not substantially impair next-day functioning among healthy subjects and subjects with insomnia.

Pharmacological characterization of a novel potent, selective, and orally active orexin 2 receptor antagonist, SDM-878

Aims

Recently, we identified a novel orexin 2 (OX₂) receptor antagonist, SDM‐878 (2‐(3‐(2‐(1H‐pyrazol‐1‐yl)nicotinoyl)‐3,8‐diazabicyclo[3.2.1]octan‐8‐yl)‐3‐methoxyisonicotinonitrile). The purpose of the present study is to characterize the in vitro and in vivo pharmacological effects of SDM‐878.

Methods

The in vitro potency and selectivity of SDM‐878 were examined in CHO cells that exhibit stable expression of human orexin 1 (OX₁), human orexin 2 (OX₂), rat OX₁, and rat OX₂receptors. Then, the plasma half‐life, oral bioavailability, and brain penetration of SDM‐878 were examined in rats. The in vivo effect of SDM‐878 in rats was tested using electroencephalography (EEG). The target engagement of SDM‐878 in the rat brain was examined using the antagonistic effect against hyperlocomotion caused by the intracerebroventricular administration of the OX₂ receptor agonist, ADL‐OXB ([Ala¹¹, d‐Leu¹⁵]‐orexin B).

Results

SDM‐878 showed potent inhibitory activities for human and rat OX₂ receptors with IC values of 10.6 and 8.8 nM, respectively, and approximately 1000‐fold selectivity against the OX₁receptor. In rat studies, SDM‐878 exhibited a relatively short half‐life in plasma, oral bioavailability, and good brain penetration. These data indicate that SDM‐878 is a potent, selective, orally active, and brain‐penetrable OX₂receptor antagonist. In behavioral studies using rats, SDM‐878 (100 mg/kg) antagonized hyperlocomotion caused by intracerebroventricular administration of ADL‐OXB. SDM‐878 exhibited a potent sleep‐promoting effect at the same dose (100 mg/kg) in a rat EEG study.

Conclusion

Our results suggest that SDM‐878 is likely to be a good pharmacological tool for investigating the role of the OX₂receptor and may have therapeutic potential for the treatment of insomnia.

We identified a novel potent, selective, orally active, and brain‐penetrable orexin 2 receptor antagonist, SDM‐878. SDM‐878 exhibited a potent sleep‐promoting effect in rats and may have therapeutic potential for the treatment of insomnia.

Preclinical in vivo characterization of lemborexant (E2006), a novel dual orexin receptor antagonist for sleep/wake regulation

Study Objectives

To present results from in vivo studies underlying the preclinical development of lemborexant (E2006), a novel dual orexin (hypocretin) receptor antagonist for sleep/wake regulation.

Methods

Rodent (wild-type rats and wild-type and orexin neuron-deficient [orexin/ataxin-3 Tg/+] mice) studies were performed to evaluate the effects of single-dose oral lemborexant (1–300 mg/kg) on orexin-induced increases in plasma adrenocorticotropic hormone (ACTH), locomotor activity, vigilance state measures (wakefulness, nonrapid eye movement [non-REM] sleep, rapid eye movement [REM] sleep), ethanol-induced anesthesia, and motor coordination, and the effects of multiple-dose oral lemborexant (30 mg/kg) on vigilance state measures. Active comparators were almorexant and zolpidem. Pharmacokinetics were assessed after single-dose lemborexant in mice and rats.

Results

Lemborexant prevented the orexin-promoted increase in ACTH in rats, therefore demonstrating inhibition of the orexin signaling pathway. Furthermore, lemborexant promoted sleep in wild-type mice and rats. Lemborexant promoted REM and non-REM sleep at an equal rate (there was no change in the REM sleep ratio). In contrast, zolpidem reduced REM sleep. The sleep-promoting effect of lemborexant was mediated via the orexin-peptide signaling pathway as demonstrated by a lack of sleep promotion in orexin neuron-deficient mice. Chronic dosing was not associated with a change in effect size or sleep architecture immediately postdosing. Lemborexant did not increase the sedative effects of ethanol or impair motor coordination, showing good safety margin in animals. Pharmacokinetic/pharmacodynamic data for mice and rats were well aligned.

Conclusions

These findings supported further clinical evaluation (ongoing at this time) of lemborexant as a potential candidate for treating insomnia and other sleep disorders.

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.

Therapy for Cataplexy

Purpose of the review

Cataplexy, an involuntary loss of muscle activity triggered by strong emotions is the most impressive symptom in narcolepsy. This review gives an overview of the current understanding of cataplexy and its available treatment options.

Recent findings

With the discovery of hypocretin/orexin, the understanding of the pathophysiology of cataplexy advanced in the past decades. In the recent years, with the development of new anticataplectic agents (e.g., Pitolisant) symptomatic treatment of cataplexy has further improved. Abrupt cessation of anticataplectic medication especially antidepressants increase the risk of status cataplecticus, a virtually continuous series of long-lasting cataplectic attacks.

Summary

Cataplexies still remain an under-recognized phenomenon due to missing diagnostic measures. Treatment for cataplexy still remains symptomatic but new agents with better tolerability and usability are continuously developed. New therapeutic actions either targeting the autoimmune mechanisms underlying orexin cell death or substituting orexin action are promising treatments for the near future.

Direct activation of G-protein-gated inward rectifying K+ channels promotes nonrapid eye movement sleep

STUDY OBJECTIVES

A major challenge in treating insomnia is to find effective medicines with fewer side effects. Activation of G-protein-gated inward rectifying K+ channels (GIRKs) by GABAB agonists baclofen or γ-hydroxybutyric acid (GHB) promotes nonrapid eye movement (NREM) sleep and consolidates sleep. However, baclofen has poor brain penetration, GHB possesses abuse liability, and in rodents both drugs cause spike-wave discharges (SWDs), an absence seizure activity. We tested the hypothesis that direct GIRK activation promotes sleep without inducing SWD using ML297, a potent and selective GIRK activator.

METHODS

Whole-cell patch-clamp recordings from hypocretin/orexin or hippocampal neurons in mouse brain slices were made to study neuronal excitability and synaptic activity; spontaneous activity, locomotion, contextual and tone-conditioned memory, and novel object recognition were assessed. Electroencephalogram/electromyogram (EEG/EMG) recordings were used to study GIRK modulation of sleep.

RESULTS

ML297, like baclofen, caused membrane hyperpolarization, decreased input resistance, and blockade of spontaneous action potentials. Unlike baclofen, ML297 (5-10 µM) did not cause significant depression of postsynaptic excitatory and inhibitory currents (EPSCs-IPSCs), indicating preferential postsynaptic inhibition. ML297 (30 mg/kg, i.p.) inhibited wake activity and locomotion, and preferentially increased NREM sleep without altering EEG delta power, REM sleep, inducing SWDs, or impairing conditioned memory and novel object recognition.

CONCLUSIONS

This study finds that direct activation of neuronal GIRK channels modulates postsynaptic membrane excitability and prolongs NREM sleep without changing sleep intensity, inducing SWDs, or impairing memory in rodents. These results suggest that direct GIRK activation with a selective compound may present an innovative approach for the treatment of chronic insomnia.

Effect of Suvorexant on Nocturnal Delirium in Elderly Patients with Alzheimer's Disease: A Case-series Study

Suvorexant, an orexin receptor antagonist used for insomnia, has been shown to have a preventive effect on delirium in a randomized placebo-controlled trial. However, its effectiveness in the management of nocturnal delirium has not yet been determined. Here we report four cases in which elderly patients with moderate to severe Alzheimer’s disease who developed nocturnal delirium were treated with suvorexant. In case 1, 15 mg suvorexant was initiated to manage nocturnal delirium refractory to antipsychotics, antidepressants, and a Japanese herbal medicine, resulting in immediate sleep improvement. However, treatment discontinuation led to recurrence of symptoms, which were reversed by recommencing suvorexant. In case 2, as antipsychotics used for the treatment of nocturnal delirium were ineffective, 15 mg suvorexant was administered. The patient achieved rapid improvement in sleep. In case 3, the use of atypical antipsychotics for the treatment of nocturnal delirium was contraindicated, as the patient had diabetes. Therefore, 15 mg suvorexant was administered following good outcomes in cases 1 and 2, resulting in immediate sleep improvement. Finally, in case 4, 15 mg suvorexant was used as an initial medication for nocturnal delirium, and the patient showed sleep improvement immediately. Elevated orexin levels in the cerebrospinal fluid are reportedly linked to sleep deterioration in patients with moderate to severe Alzheimer’s disease. The immediate and reproducible action and effectiveness of suvorexant observed in our patients suggest that enhanced cerebral orexin activity might be associated with sleep-wake cycle disturbances due to delirium in elderly patients with Alzheimer’s disease.

Neurophysiological and Behavioral Effects of Anti-Orexinergic Treatments in a Mouse Model of Huntington's Disease

Huntington's disease (HD) is associated with sleep and circadian disturbances in addition to hallmark motor and cognitive impairments. Electrophysiological studies on HD mouse models have revealed an aberrant oscillatory activity at the beta frequency, during sleep, that is associated with HD pathology. Moreover, HD animal models display an abnormal sleep-wake cycle and sleep fragmentation. In this study, we investigated a potential involvement of the orexinergic system dysfunctioning in sleep-wake and circadian disturbances and abnormal network (i.e., beta) activity in the R6/1 mouse model. We found that the age at which orexin activity starts to deviate from normal activity pattern coincides with that of sleep disturbances as well as the beta activity. We also found that acute administration of Suvorexant, an orexin 1 and orexin 2 receptor antagonist, was sufficient to decrease the beta power significantly and to improve sleep in R6/1 mice. In addition, a 5-day treatment paradigm alleviated cognitive deficits and induced a gain of body weight in female HD mice. These results suggest that restoring normal activity of the orexinergic system could be an efficient therapeutic solution for sleep and behavioral disturbances in HD.

Improvement of glycemic control by treatment for insomnia with suvorexant in type 2 diabetes mellitus

Introduction

Acute and chronic insomnia can exacerbate type 2 diabetes mellitus (T2DM). We investigated suvorexant (an anti-insomnia drug that targets the orexin system) effects on sleep architecture and glucose metabolism in T2DM patients with insomnia.

Materials and methods

This 7 day open-label, single-arm, intervention trial included 18 subjects with T2DM and insomnia. After 1 day acclimatization, daily glucose levels, sleep architecture, and autonomic nervous function were evaluated by continuous glucose monitoring (CGM), single-channel electroencephalography, and accelerometry, respectively.

Results

Suvorexant treatment for 3 days significantly increased total sleep time and sleep efficiency, with partial suppression of sympathetic nerve activity. CGM-measured 24 h mean glucose level decreased significantly from 157.7 ± 22.9 to 152.3 ± 17.8 mg/dL, especially in the early glucose surge after the midnight nadir (from 28.3 ± 15.0 to 18.2 ± 9.9 mg/dL), and until supper with a significant improvement in homeostasis model assessment of insulin resistance from 4.0 ± 2.8 to 2.9 ± 1.6, respectively.

Conclusions

Suvorexant treatment for insomnia of subjects with T2DM significantly improved CGM-measured daily glycemic control, which was associated with changes in sympathomimetic tone and/or improved insulin sensitivity. The amelioration of insomnia may therefore be a target for improving glycemic control in T2DM patients with insomnia.

Lemborexant, A Dual Orexin Receptor Antagonist (DORA) for the Treatment of Insomnia Disorder: Results From a Bayesian, Adaptive, Randomized, Double-Blind, Placebo-Controlled Study

STUDY OBJECTIVES

To identify dose(s) of lemborexant that maximize insomnia treatment efficacy while minimizing next-morning residual sleepiness and evaluate lemborexant effects on polysomnography (PSG) measures (sleep efficiency [SE], latency to persistent sleep [LPS], and wake after sleep onset [WASO]) at the beginning and end of treatment.

METHODS

Adults and elderly subjects with insomnia disorder per the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition were enrolled in a multicenter, randomized, double-blind, placebo-controlled, Bayesian, adaptive, parallel-group study, receiving lemborexant (1, 2.5, 5, 10, 15, 25 mg) or placebo for 15 nights. Efficacy assessments included a utility function that combined efficacy (SE) and safety (residual morning sleepiness as measured by Karolinska Sleepiness Scale [KSS]), PSG measures, and sleep diary. Safety assessments included KSS, Digit Symbol Substitution Test, computerized reaction time tests, and adverse events (AEs).

RESULTS

A total of 616 subjects were screened; 291 were randomized. Baseline characteristics were similar between lemborexant groups and placebo (∼63% female, median age: 49.0 years). The study was stopped for early success after the fifth interim analysis when the 15-mg dose met utility index/KSS criteria for success; 3 other doses also met the criteria. Compared with placebo, subjects showed significant improvements in SE, subjective SE, LPS, and subjective sleep onset latency at the beginning and end of treatment for lemborexant doses ≥ 5 mg (P < .05). WASO and subjective WASO showed numerically greater improvements for doses > 1 mg. AEs, mostly mild to moderate, included dose-related somnolence.

CONCLUSIONS

Lemborexant doses ranging from 2.5-10 mg provided efficacy for the treatment of insomnia while minimizing next-morning residual sleepiness.

CLINICAL TRIAL REGISTRATION

Title: A Multicenter, Randomized, Double-blind, Placebo-controlled, Parallel-group, Bayesian Adaptive Randomization Design, Dose Response Study of the Efficacy of E2006 in Adults and Elderly Subjects With Chronic Insomnia; URL: https://clinicaltrials.gov/ct2/show/NCT01995838; Identifier: NCT01995838.

Prefrontal Cortical Opioids and Dysregulated Motivation: A Network Hypothesis

Loss of inhibitory control over appetitively motivated behavior occurs in multiple psychiatric disorders, including drug abuse, behavioral addictions, and eating disorders with binge features. In this opinion article, novel actions of μ-opioid peptides in the prefrontal cortex (PFC) that could contribute to inhibitory control deficits will be discussed. Evidence has accrued to suggest that excessive intra-PFC μ-opioid receptor (μ-OR) signaling alters the PFC response to excitatory drive, resulting in supernormal and incoherent recruitment of multiple PFC output pathways. Affected pathways include functionally opposed PFC→hypothalamus 'appetitive driver' and PFC→striatum 'appetitive limiter' projections. This network perturbation engenders disorganized, impulsive appetitive responses. Evidence supporting this hypothesis from human imaging and animal studies will be discussed, and combinatorial drug treatments targeting μ-ORs and specific PFC subcortical targets will be explored.

Suvorexant-Induced Dream Enactment Behavior in Parkinson Disease: A Case Report

ABSTRACT

Suvorexant is a new insomnia drug, and it is generally safe and well tolerated. Here, we report a rare but potentially important adverse effect of suvorexant in a patient with Parkinson disease.

Timed Inhibition of Orexin System by Suvorexant Improved Sleep and Glucose Metabolism in Type 2 Diabetic db/db Mice

Sleep disturbances are associated with type 2 diabetes; therefore, the amelioration of sleep may improve metabolic disorders. To investigate this possibility, we here examined the effects of suvorexant, an antiinsomnia drug targeting the orexin system, on sleep and glucose metabolism in type 2 diabetic mice. Diabetic db/db mice had a longer wakefulness time during the resting period, as compared with nondiabetic db/m+ control mice. The single or 7-day administration of suvorexant at lights-on (ie, the beginning of the resting phase) increased nonrapid eye movement sleep time during the resting phase and, as a consequence, reduced awake time. The daily resting-phase administration of suvorexant for 2-4 weeks improved impaired glucose tolerance in db/db mice without affecting body weight gain, food intake, systemic insulin sensitivity, or serum insulin, and glucagon levels. No changes were detected in the markers of lipid metabolism and inflammation, such as the hepatic triglyceride content and Tnf-α mRNA levels in liver and adipose tissues. The improving effect of suvorexant on glucose tolerance was associated with a reduction in the expression levels of hepatic gluconeogenic factors, including phosphoenolpyruvate carboxykinase and peroxisome proliferator-activated receptor-γ coactivator-1α in the liver in the resting phase. In contrast, the daily awake-phase administration of suvorexant had no beneficial effect on glucose metabolism. These results suggest that the suvorexant-induced increase of sleep time at the resting phase improved hepatic glucose metabolism in db/db mice. Our results provide insight into the development of novel pharmacological interventions for type 2 diabetes that target the orexin-operated sleep/wake regulatory system.