Altered ventilatory responses to hypercapnia-hypoxia challenges in a preclinical SUDEP model involve orexin neurons.

Failure to recover from repeated hypercapnia and hypoxemia (HH) challenges caused by severe GCS and postictal apneas may contribute to sudden unexpected death in epilepsy (SUDEP). Our previous studies found orexinergic dysfunction contributes to respiratory abnormalities in a preclinical model of SUDEP, Kcna1-/- mice. Here, we developed two gas challenges consisting of repeated HH exposures and used whole body plethysmography to determine whether Kcna1-/- mice have detrimental ventilatory responses. Kcna1-/- mice exhibited an elevated ventilatory response to a mild repeated hypercapnia-hypoxia (HH) challenge compared to WT. Moreover, 71% of Kcna1-/- mice failed to survive a severe repeated HH challenge, whereas all WT mice recovered. We next determined whether orexin was involved in these differences. Pretreating Kcna1-/- mice with a dual orexin receptor antagonist rescued the ventilatory response during the mild challenge and all subjects survived the severe challenge. In ex vivo extracellular recordings in the lateral hypothalamus of coronal brain slices, we found reducing pH either inhibits or stimulates putative orexin neurons similar to other chemosensitive neurons; however, a significantly greater percentage of putative orexin neurons from Kcna1-/-mice were stimulated and the magnitude of stimulation was increased resulting in augmentation of the calculated chemosensitivity index relative to WT. Collectively, our data suggest that increased chemosensitive activity of orexin neurons may be pathologic in the Kcna1-/- mouse model of SUDEP, and contribute to elevated ventilatory responses. Our preclinical data suggest that those at high risk for SUDEP may be more sensitive to HH challenges, whether induced by seizures or other means; and the depth and length of the HH exposure could dictate the probability of survival.

Early experience with the new DORA daridorexant in patients with insomnia disorder and comorbid mental disturbances: Results of a naturalistic study with 3 months follow-up.

Insomnia disorder may affect mental health, increasing suicidal risk. Targeting insomnia is crucial in the clinical practice. Sixty-six consecutive patients with insomnia disorder according with the DSM-5-TR criteria were treated with the dual orexin receptor antagonist, daridorexant 50 mg. Baseline (T0), 1 month (T1) and 3 month (T2) evaluations were performed. Insomnia severity (Insomnia Severity Index), mood, anxiety symptoms and suicidal risk (Beck Depression Inventory-II, Young Mania Rating Scale, Self-Reported Anxiety Scale, Suicidal Ideation Scale), dysfunctional insomnia-cognitive factors and pre-sleep arousal (Dysfunctional Beliefs About Sleep, Pre-Sleep Arousal Scale) were evaluated. The final sample included 66 patients (n = 36, 54% females, mean age 60 ± 13.6 years). Most of them, 64%, suffered from insomnia disorder comorbid with unipolar/bipolar depression, anxiety disorders and substance use disorders. Repeated ANOVA analyses showed that Insomnia Severity Index, Dysfunctional Beliefs About Sleep and Pre-Sleep Arousal Scale total score decreased across time (F = 68.818, p < 0.001; F = 47.561, p < 0.001; F = 28.142, p < 0.001, respectively). Similarly, Beck Depression Inventory-II, Self-Reported Anxiety Scale, Young Mania Rating Scale, and Suicidal Ideation Scale significantly decreased over time (p < 0.001). Predictors of insomnia remission (Insomnia Severity Index < 8) at T1 were improvement of Insomnia Severity Index at T1 (F = 60.205, p < 0.001), and improvement of Dysfunctional Beliefs About Sleep at T1 (F = 4.432, p = 0.041). Insomnia remission at T2 was best predicted by improvement of Dysfunctional Beliefs About Sleep at T2 (F = 3.993, p = 0.023). Multiple-regression models showed that clinical improvement of Beck Depression Inventory-II was best predicted by improvement in Dysfunctional Beliefs About Sleep at T1 and T2, manic symptoms by Insomnia Severity Index at T2, anxiety symptoms by Dysfunctional Beliefs About Sleep, Insomnia Severity Index and somatic Pre-Sleep Arousal Scale at T1 and T2. With the caution of a naturalistic design, early experience with daridorexant showed that by targeting insomnia it may be possible to improve not only insomnia symptoms but also comorbid symptoms.

Daridorexant treatment for chronic insomnia: a real-world retrospective single-center study.

INTRODUCTION: Chronic insomnia disorder (CID) significantly impacts well-being and daily functioning. Daridorexant, a double orexin receptor blocker, has shown efficacy in randomized clinical trials and has been recently approved for the treatment of CID in adult patients. This retrospective observational study aimed to describe real-world data on daridorexant effectiveness and safety in adult patients with CID. METHODS: Consecutive patients initiating on-label daridorexant at the Sleep Medicine Centre, University Hospital of Rome Tor Vergata were enrolled. Baseline and 30-day follow-up (FU) evaluations included patients' and CID characteristics, comorbidities, and clinicians' and patients' subjective ratings of changes with the Clinical and Patient Global Impression-Improvement scores (CGI-Is and PGI-Is), as well as Insomnia Severity Index (ISI) scores in a subgroup of patients. RESULTS: Sixty-nine patients initiated 50-mg daily dosage. At FU, 58% of both patients and clinicians rated CID as improved on CGI-Is and PGI-Is, with no differences based on comorbidities, sex, or number of previous medications. No significant predictors of CGI-Is and PGI-Is improvement were identified. At FU, ISI scores (n = 24) significantly decreased from 18.25 ± 3.21 to 12.08 ± 6.12 (Z = 8.000; p < 0.001). Of these, eight patients (33.3%) had absence of insomnia symptoms, and no patients reported a worsening in ISI score categories. CONCLUSIONS: This study suggests daridorexant to be effective and safe in real-world CID treatment whether used as a first-ever treatment, switch, or add-on, as reflected by subjective and objective measures and the absence of serious treatment-related adverse events. Future research on larger cohorts should explore daridorexant potential across diverse patient characteristics.

Role of the orexin system in the bidirectional relation between sleep and epilepsy: New chances for patients with epilepsy by the antagonism to orexin receptors?

Epilepsy is a common neurological disorder, affecting patients of all ages, reducing the quality of life, and associated with several comorbidities. Sleep impairment is a frequent condition in patients with epilepsy (PWE), and the relation between sleep and epilepsy has been considered bidirectional, as one can significantly influence the other, and vice versa. The orexin system was described more than 20 years ago and is implicated in several neurobiological functions other than in controlling the sleep-wake cycle. Considering the relation between epilepsy and sleep, and the significant contribution of the orexin system in regulating the sleep-wake cycle, it is conceivable that the orexin system may be affected in PWE. Preclinical studies investigated the impact of the orexin system on epileptogenesis and the effect of orexin antagonism on seizures in animal models. Conversely, clinical studies are few and propose heterogeneous results also considering the different methodological approaches to orexin levels quantification (cerebrospinal-fluid or blood samples). Because orexin system activity can be modulated by sleep, and considering the sleep impairment documented in PWE, the recently approved dual orexin receptor antagonists (DORAs) have been suggested for treating sleep impairment and insomnia in PWE. Accordingly, sleep improvement can be a therapeutic strategy for reducing seizures and better managing epilepsy. The present review analyzes the preclinical and clinical evidence linking the orexin system to epilepsy, and hypothesizes a model in which the antagonism to the orexin system by DORAs can improve epilepsy by both a direct and a sleep-mediated (indirect) effect.

Comparative efficacy and safety of lemborexant 5 mg versus 10 mg for the treatment of insomnia: a systematic review.

INTRODUCTION: Insomnia is a common condition that may be caused by or coexist with other medical or psychological illnesses. Nearly a quarter of a billion people across the globe suffer from insomnia frequently. Lemborexant, a dual orexin receptor antagonist, is a recently authorized hypnotic-based medication for insomnia. The purpose of this systematic review is to further investigate its efficacy and safety profile, with the primary goal of comparing the effects of two FDA-approved doses of lemborexant, 5 mg and 10 mg (LEM5 and LEM10, respectively). MATERIALS AND METHODS: PubMed, Google Scholar, ClinicalTrials.gov, and Cochrane Central were searched for relevant literature, and studies were considered if they compared the efficacy and safety of lemborexant 5 mg to lemborexant 10 mg. This study comprised clinical trials. RESULTS: A total of 6 studies were evaluated for efficacy and safety of lemborexant therapy. They reported a significant betterment in values pertaining to sleep efficacy, sleep onset latency, wake after sleep onset, total sleep time, sleep quality, ISI score, and morning alertness. The results presented a dose-dependent pattern and showed slight variation with the different dosages. The most prevalent side effects noted were somnolence, headaches, and dizziness, with infections like UTIs and upper respiratory tract infections also being commonly reported. The incidence is rather ambiguous and not sincerely dose-dependent. The differences between results for LEM5 and LEM10 do not exhibit a wide variation, although slight dose-dependent alterations are noted. CONCLUSION: Lemborexant is well integrated with the amelioration of sleep disturbances in insomniac patients, as shown by a decrease in eSOL and sWASO and a rise in sSE, sTST, quality of sleep, and morning alertness. Effects last 12 months after therapy.

Dual orexin receptor antagonist (DORA-12) treatment affects the overall levels of Net/maoA mRNA expression in the hippocampus.

The orexinergic system plays a significant role in regulating proper sleep/wake maintenance. Dual orexin receptor antagonist (DORA) is widely prescribed for insomnia symptoms. The antagonist acts on orexin 1 and 2 receptors located in certain brain areas, including the locus coeruleus and dorsal raphe. Nevertheless, its effects on monoamine-related gene expression remain unclear. Here, we measured the expression levels of monoamine-related genes in DORA-treated mice. DORA treatment significantly affected overall levels of noradrenalin transporter/monoamine oxidases A mRNA expression in the hippocampus. Our findings suggest that DORA contributes to noradrenalin-related gene expression regulation in the central nervous system.

Discovery of ORN0829, a potent dual orexin 1/2 receptor antagonist for the treatment of insomnia.

Here, we present the design, synthesis, and SAR of dual orexin 1 and 2 receptor antagonists, which were optimized by balancing the antagonistic activity for orexin receptors and lipophilicity. Based on the prototype compound 1, ring construction and the insertion of an additional heteroatom into the resulting ring led to the discovery of orexin 1 and 2 receptor antagonists, which were 3-benzoyl-1,3-oxazinane derivatives. Within these derivatives, (-)-3h enabled a high dual orexin receptor antagonistic activity and a low lipophilicity. Compound (-)-3h exhibited potent sleep-promoting effects at a po dose of 1 mg/kg in a rat polysomnogram study, and optimal PK properties with a rapid Tmax and short half-lives in rats and dogs were observed, indicating a predicted human half-life of 0.9-2.0 h. Thus, (-)-3h (ORN0829; investigation code name, TS-142) was selected as a viable candidate and is currently in clinical development for the treatment of insomnia.

The dual orexin receptor antagonist daridorexant does not affect the pharmacokinetics of the BCRP substrate rosuvastatin.

Daridorexant is a dual orexin receptor antagonist in clinical development for the treatment of insomnia. Breast-cancer resistant protein (BCRP) is an efflux pump expressed in intestinal epithelium and hepatocytes, contributing to the absorption, distribution, and elimination of drugs and endogenous compounds. In vitro, daridorexant inhibits BCRP with an IC50 of 3.0 µmol/L. The BCRP substrate rosuvastatin is a cholesterol-lowering drug, recommended for clinical drug-drug interaction (DDI) studies. In order to exclude an inhibitory effect of daridorexant on BCRP, this single-centre, open-label, two-treatment Phase 1 study investigated the effect of daridorexant at steady state on the pharmacokinetics (PK) of single-dose rosuvastatin in 20 healthy male subjects. In addition, safety and tolerability were assessed. A single oral dose of 10 mg rosuvastatin on Day 1 was followed by 96 hours observation. Thereafter, 25 mg daridorexant was administered once daily (o.d.) on Days 5-8 and in combination with 10 mg rosuvastatin on Day 8. On Days 9-12, subjects received 25 mg daridorexant alone. PK sampling was performed up to 120 hours after treatment administration. The results showed that concomitant administration of 25 mg daridorexant o.d. at steady state did not affect the exposure parameters of rosuvastatin in a relevant way, as indicated by the ratios of geometric means (GMRs) ([rosuvastatin + daridorexant]/[rosuvastatin alone]) of 0.93 for both Cmax and AUC0-∞ . Administration of a single dose of 10 mg rosuvastatin, multiple doses of 25 mg daridorexant alone or in combination were well tolerated. Taken together, daridorexant and BCRP substrates can be safely co-administered.

Identification of highly selective and potent orexin receptor 1 antagonists derived from a dual orexin receptor 1/2 antagonist based on the structural framework of pyrazoylethylbenzamide.

The design, synthesis, and structure activity relationships of the novel class of pyrazolylethylbenzamide orexin receptor 1-selective antagonists are described. Further derivatization of the prototype dual orexin receptor 1/2 antagonist lead (1) by installing a (S)-methyl group into the ethyl linker moiety between the pyrazole ring and benzamide resulted in an increase of the antagonist potency against orexin receptor 1/2 receptors. Optimization of the benzamide and pyrazole parts of compounds 2 and 9b led to the identification of N-ethyl-5-fluoro-N-{(2S)-1-[5-(4-fluorophenyl)-2H-tetrazol-2-yl]propan-2-yl}-2-(pyrimidin-2-yl)benzamide (24), which exhibited excellent antagonistic activity against orexin receptor 1 with an IC50 of 2.01nM and a 265-fold selectivity for orexin receptor 1 over orexin receptor 2.

Discovery of highly potent and selective orexin 1 receptor antagonists (1-SORAs) suitable for in vivo interrogation of orexin 1 receptor pharmacology.

While a correlation between blockade of the orexin 2 receptor (OX2R) with either a dual orexin receptor antagonist (DORA) or a selective orexin 2 receptor antagonist (2-SORA) and a decrease of wakefulness is well established, less is known about selective blockade of the orexin 1 receptor (OX1R). Therefore, a highly selective orexin 1 antagonist (1-SORA) with suitable properties to allow in vivo interrogation of OX1R specific pharmacology in preclinical species remains an attractive target. Herein, we describe the discovery of an optimized 1-SORA series in the piperidine ether class. Notably, a 4,4-difluoropiperidine core coupled with a 2-quinoline ether linkage provides OX1R selective compounds. The combination with an azabenzimidazole or imidazopyridine amide substituent leads to analogs 47 and 51 with >625-fold functional selectivity for OX1R over OX2R in rat. Compounds 47 and 51 possess clean off-target profiles and the required pharmacokinetic and physical properties to be useful as 1-SORA tool compounds.

Discovery of piperidine ethers as selective orexin receptor antagonists (SORAs) inspired by filorexant.

Highly selective orexin receptor antagonists (SORAs) of the orexin 2 receptor (OX2R) have become attractive targets both as potential therapeutics for insomnia as well as biological tools to help further elucidate the underlying pharmacology of the orexin signaling pathway. Herein, we describe the discovery of a novel piperidine ether 2-SORA class identified by systematic lead optimization beginning with filorexant, a dual orexin receptor antagonist (DORA) that recently completed Phase 2 clinical trials. Changes to the ether linkage and pendant heterocycle of filorexant were found to impart significant selectivity for OX2R, culminating in lead compound PE-6. PE-6 displays sub-nanomolar binding affinity and functional potency on OX2R while maintaining >1600-fold binding selectivity and >200-fold functional selectivity versus the orexin 1 receptor (OX1R). PE-6 bears a clean off-target profile, a good overall preclinical pharmacokinetic (PK) profile, and reduces wakefulness with increased NREM and REM sleep when evaluated in vivo in a rat sleep study. Importantly, subtle structural changes to the piperidine ether class impart dramatic changes in receptor selectivity. To this end, our laboratories have identified multiple piperidine ether 2-SORAs, 1-SORAs, and DORAs, providing access to a number of important biological tool compounds from a single structural class.

Discovery and in vitro and in vivo profiles of N-ethyl-N-[2-[3-(5-fluoro-2-pyridinyl)-1H-pyrazol-1-yl]ethyl]-2-(2H-1,2,3-triazol-2-yl)-benzamide as a novel class of dual orexin receptor antagonist.

Orexins play an important role in sleep/wake regulation, and orexin receptor antagonists are a focus of novel therapy for the treatment of insomnia. We identified 27e (TASP0428980) as a potent dual orexin receptor antagonist through the systematic modification of our original designed lead A. We demonstrated the potent sleep-promoting effects of 27e at ip dose of 3mg/kg in a rat polysomnogram study. 27e exhibited relatively short half-life profiles in rats and dogs. Furthermore, accumulating evidence regarding ADME profiles indicates that the predicted human half-life of 27e should be 1.2-1.4h. These data indicated that 27e has a short-acting hypnotic property, suggesting that 27e might be useful for treating primary insomnia while exhibiting a low risk of next-day residual somnolence. Thus, 27e and its related compounds should be further evaluated to enable advancement to clinical trials.

A randomized, double-blind, placebo-controlled, crossover study of respiratory safety of lemborexant in moderate to severe obstructive sleep apnea.

STUDY OBJECTIVES: To evaluate the respiratory safety of lemborexant among adults and older adults with moderate to severe obstructive sleep apnea (OSA). METHODS: E2006-A001-113 (Study 113; NCT04647383) was a double-blind, two-period crossover, placebo-controlled study in adults (ages ≥ 45 to ≤ 90 years, n = 33) with moderate (apnea-hypopnea index [AHI] score ≥ 15 to < 30 events/h, n = 13) or severe (AHI ≥ 30 events/h, n = 20) OSA. Participants were randomized to lemborexant 10 mg (LEM10) or placebo (PBO) for two treatment periods of 8 nights with a ≥ 14-day washout period. AHI and peripheral oxygen saturation were evaluated after treatment on Day 1 (after a single dose) and Day 8 (after multiple doses). RESULTS: No significant differences in AHI were observed after single and multiple doses of LEM10 compared with PBO in participants with moderate to severe OSA (least-squares mean: single-dose LEM10, 41.7; PBO, 44.8; multiple-dose LEM10, 44.9; PBO, 45.7). In addition, there were no significant differences between treatments in peripheral oxygen saturation (least-squares mean: single-dose LEM10, 93.0; PBO, 93.1; multiple-dose LEM10, 93.1; PBO, 93.4). Further, there were no significant differences between treatments in percentage of total sleep time with peripheral oxygen saturation < 90%, < 85%, or < 80%. No significant differences were observed between treatments when AHI and peripheral oxygen saturation outcomes were analyzed by OSA severity. Altogether, 6/33 (18.2%) participants receiving LEM10, vs 3/33 (9.1%) PBO, reported treatment-emergent adverse events, mostly mild in severity. CONCLUSIONS: LEM10 demonstrated respiratory safety and was well tolerated with single-dose and multiple-dose administration in participants with moderate to severe OSA. This suggests that LEM may be a treatment option for patients with OSA and comorbid insomnia. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Name: A Study to Evaluate the Respiratory Safety of Lemborexant in Adult and Elderly Participants With Moderate to Severe Obstructive Sleep Apnea and in Adult and Elderly Participants With Moderate to Severe Chronic Obstructive Pulmonary Disease; URL: https://clinicaltrials.gov/ct2/show/NCT04647383; Identifier: NCT04647383. CITATION: Cheng JY, Lorch D, Lowe AD, et al. A randomized, double-blind, placebo-controlled, crossover study of respiratory safety of lemborexant in moderate to severe obstructive sleep apnea. J Clin Sleep Med. 2024;20(1):57-65.

Incorporation of suvorexant and lemborexant into hair and their distributions after a single intake.

PURPOSE: This study examined the applicability of hair analysis as an approach to identify suvorexant (SUV) and lemborexant (LEM) intake by analyzing black hair specimens collected from study participants after a single oral administration. METHODS: Hair specimens were collected form participants who took a single dose of 10 mg SUV or 5 mg LEM. Identification of the dual orexin receptor antagonists (DORAs) and their metabolites was performed by liquid chromatography-tandem mass spectrometry. Reference standards of S-M9 and L-M4, the metabolites of SUV and LEM, respectively, were synthesized in our laboratory. Sectional analysis of 1-mm segments of the single-hair strands was also performed to investigate the incorporation behavior of the drugs into hair. RESULTS: Unchanged SUV and LEM, and their metabolites S-M9 and L-M4 were detected even in the single-hair specimens. Results of the segmental hair analysis showed predominant incorporation of the drugs into hair through the hair bulb region rather than through the upper dermis zone of the hair root. The drug concentrations in the hair specimens, collected about 1 month after intake, were 0.033-0.037 pg/hair strand (0.17-0.19 pg/mg) for SUV and 0.054-0.28 pg/hair strand (0.28-1.5 pg/mg) for LEM. The calculated distribution ratios of the DORAs into hair to the oral doses were much lower than those of benzodiazepines and zolpidem reported in a previous study. CONCLUSIONS: This is the first report of the detection of the DORAs in hair. The incorporation behavior of the DORAs into hair revealed herein are crucial for proper interpretation of hair test results.

Dual orexin receptor antagonist ameliorates sleep deprivation-induced learning and memory impairment in APP/PS1 mice.

Sleep is considered closely related to cognitive function, and cognitive impairment is the main clinical manifestation of Alzheimer's disease (AD). Sleep disturbance in AD patients is more severe than that in healthy elderly individuals. Additionally, sleep deprivation reportedly increases the activity of the hypothalamic orexin system and the risk of AD. To investigate whether intervention with the orexin system can improve sleep disturbance in AD and its impact on AD pathology. In this study, six-month-old amyloid precursor protein/presenilin 1 mice were subjected to six weeks of chronic sleep deprivation and injected intraperitoneally with almorexant, a dual orexin receptor antagonist (DORA), to investigate the effects and mechanisms of sleep deprivation and almorexant intervention on learning and memory in mice with AD. We found that sleep deprivation aggravated learning and memory impairment and increased brain ß-amyloid (Aß) deposition in mice with AD. The application of almorexant can increase the total sleep time of sleep-deprived mice and reduce cognitive impairment and Aß deposition, which is related to the improvement in Aquaporin-4 polarity. Thus, DORA may be an effective strategy for delaying the progression of AD patients by improving the sleep disturbances.

Resting phase-administration of lemborexant ameliorates sleep and glucose tolerance in type 2 diabetic mice.

Sleep disorders are associated with increased risk of obesity and type 2 diabetes. Lemborexant, a dual orexin receptor antagonist (DORA), is clinically used to treat insomnia. However, the influence of lemborexant on sleep and glucose metabolism in type 2 diabetic state has remained unknown. In the present study, we investigated the effect of lemborexant in type 2 diabetic db/db mice exhibiting both sleep disruption and glucose intolerance. Single administration of lemborexant at the beginning of the light phase (i.e., resting phase) acutely increased total time spent in non-rapid eye movement (NREM) and REM sleep in db/db mice. Durations of NREM sleep-, REM sleep-, and wake-episodes were also increased by this administration. Daily resting-phase administration of lemborexant for 3-6 weeks improved glucose tolerance without changing body weight and glucose-stimulated insulin secretion in db/db mice. Similar improvement of glucose tolerance was caused by daily resting-phase administration of lemborexant in obese C57BL/6J mice fed high fat diet, whereas no such effect was observed in non-diabetic db/m+ mice. Diabetic db/db mice treated daily with lemborexant exhibited increased locomotor activity in the dark phase (i.e., awake phase), although they did not show any behavioral abnormality in the Y-maze, elevated plus maze, and forced swim tests. These results suggest that timely promotion of sleep by lemborexant improved the quality of wakefulness in association with increased physical activity during the awake phase, and these changes may underlie the amelioration of glucose metabolism under type 2 diabetic conditions.

Daridorexant as a novel pharmacotherapeutic approach in insomnia: a systematic review and meta-analysis.

BACKGROUND: Insomnia is a multi-factorial disorder with conventional treatment options that are not satisfactory for many patients. This metaanalysis analyzed the safety and efficacy of daridorexant. METHODS: An electronic database search for RCTs was conducted on Medline via PubMed, Cochrane, and Clinicaltrials.gov using the terms 'Daridorexant,' 'RCT,' 'Insomnia' trials evaluating the efficacy and/or safety of daridorexant for insomnia were included. The data were synthesized using Cochrane review manager version 5.4.1. Cochrane risk of bias 2.0 tool and GRADEpro-GDT were used to assess the methodological and evidence quality, respectively. RESULTS: Of 109 searched studies, four trials were included. The risk of treatment-emergent adverse events with 25 mg daridorexant [risk ratio (RR) = 1.12 (0.88, 1.43), p = 0.36; I2 = 0%] and 50 mg daridorexant [RR = 1.25 (0.88, 1.79), p = 0.22; I2 = 28%] and serious adverse events with 25 mg [RR = 0.86 (0.23, 3.19), p = 0.82, I2 = 56%] and 50 mg [RR = 1.32 (0.29, 6.08), p = 0.72, I2 = 52%] was comparable to placebo [Moderate quality evidence]. Risk of nasopharyngitis was also comparable to placebo. The efficacy parameters like wake after sleep onset, latency to persistent sleep, and subjective total sleep time showed significant improvement with daridorexant. The risk of bias is low for three studies and some concern for one. CONCLUSION: Daridorexant is a safer and efficacious agent for induction and maintenance of sleep for chronic insomnia. PROSPERO: The registration number is CRD42022335233. CLINICAL TRIAL REGISTRATION: www.clinicaltrials.gov identifiers are NCT03575104, NCT03545191, NCT03679884, and NCT02839200).

Failure of the dual orexin receptor antagonist suvorexant to engender drug discrimination in rats.

For abuse potential assessment, U.S. Food and Drug Administration (FDA) requests that new, brain-penetrating drugs are ideally compared with approved drugs that share the mechanism of action and are judged to have abuse liability by the Drug Enforcement Agency. For development of the dual orexin receptor antagonist (DORA) daridorexant, the FDA recommended conducting a rat drug discrimination paradigm against the approved, schedule IV, DORA suvorexant. Surprisingly, at suvorexant plasma levels up to three-fold the maximum concentration at the highest approved human dose, rats did not learn to discriminate the suvorexant stimulus from vehicle.

Blockade of orexin receptors in the infralimbic cortex prevents stress-induced reinstatement of alcohol-seeking behaviour in alcohol-dependent rats.

BACKGROUND AND PURPOSE: A major problem managing alcohol use disorder is the high vulnerability to relapse, even after long periods of abstinence. Chronic alcohol use dysregulates stress responsivity, rendering this system hyporesponsive and making individuals vulnerable to relapse. Orexin (hypocretin) plays a role in diverse physiological processes, including stress. Orexin neurons in the hypothalamus, project to the infralimbic cortex. This study asked does infralimbic cortex orexin transmission play a significant role in stress-induced reinstatement of alcohol-seeking behaviour in alcohol-dependent rats. EXPERIMENTAL APPROACH: Male and female rats were trained to self-administer 10% alcohol (3 weeks) and then made dependent via chronic intermittent alcohol vapour exposure. Following extinction (5 days·week-1 at 8 h abstinence for 10 sessions), rats received an intra- infralimbic cortex microinfusion of the OX1/2 antagonist TCS 1102 (15 µg/0.5 µl per side) and then tested for footshock stress-induced reinstatement of alcohol seeking. In a separate cohort, orexin regulation of infralimbic cortex neuronal activity at the time of reinstatement was investigated using ex vivo electrophysiology. KEY RESULTS: TCS 1102 prevented reinstatement in dependent animals only. Moreover, Hcrtr mRNA expression in the hypothalamus and Hcrtr1/2 in the infralimbic cortex increased in alcohol-dependent animals at the time of testing. Dependence dampened basal orexin/OX receptor influence over infralimbic cortex GABAergic synapses (using TCS 1102) allow for greater stimulated orexin effects. CONCLUSION AND IMPLICATIONS: Infralimbic cortex transmission is implicate in stress-induced reinstatement of alcohol-seeking behaviour in subjects with a history of alcohol dependence and show maladaptive recruitment of infralimbic cortex transmission by alcohol dependence.

Abuse potential assessment of the dual orexin receptor antagonist daridorexant in rats.

BACKGROUND: Drugs that act on the central nervous system (CNS) and have sedative effects can lead to abuse in humans. New CNS-active drugs often require evaluation of their abuse potential in dedicated animal models before marketing approval. Daridorexant is a new dual orexin receptor antagonist (DORA) with sleep-promoting properties in animals and humans. It was approved in 2022 in the United States and Europe for the treatment of insomnia disorder. AIMS: Nonclinical evaluation of abuse potential of daridorexant using three specific rat models assessing reinforcement, interoception, and withdrawal. METHODS: Reinforcing effects of daridorexant were assessed in an operant rat model of intravenous drug self-administration. Similarity of interoceptive effects to those of the commonly used sleep medication zolpidem was tested in an operant drug discrimination task. Withdrawal signs indicative of physical dependence were evaluated upon sudden termination of chronic daridorexant treatment. Rat experiments were conducted at a dose range resulting in daridorexant plasma concentrations equaling or exceeding those achieved at the clinically recommended dose of 50 mg in humans. RESULTS: Daridorexant had no reinforcing effects, was dissimilar to zolpidem in the drug discrimination task, and did not induce any withdrawal-related signs upon treatment discontinuation that would be indicative of physical dependence. OUTCOMES: Daridorexant showed no signs of abuse or dependence potential in rats. Our data indicate that daridorexant, like other DORAs, has a low potential for abuse in humans.