The Use of Physiology-Based Pharmacokinetic and Pharmacodynamic Modeling in the Discovery of the Dual Orexin Receptor Antagonist ACT-541468

Discovery of IDOR-1117-1680, a dual orexin receptor antagonist with fast onset and short duration of action for the treatment of insomnia

We describe the optimization of 2-acyl-1-biarylmethylpyrazolidines, a novel class of dual orexin receptor antagonists (DORAs) designed for the treatment of sleep disorders requiring a rapid onset (<30 min) and a short duration of action (2-4 h). Building on the previously identified lead compound DORA 4, our optimization program yielded several potent pyrazolidine DORAs with carefully tailored in vitro physicochemical and DMPK (drug, metabolism and pharmacokinetics) properties. In vivo studies in animals, combined with pharmacokinetic-pharmacodynamic (PK-PD) simulations, demonstrated that DORA 31 and DORA (R)-38 effectively induced sleep in dogs and met the in silico predicted requirements for rapid onset and short duration in humans. Further analysis of their covalent binding potential in human hepatocytes prioritized DORA 31 as the preferred molecule for additional safety and biopharmaceutical evaluation. In this report we summarize and present the results of all studies that supported the selection of DORA 31 (IDOR-1117-1680) as a preclinical development candidate.

Effects of daridorexant on rest/wake activity patterns and drinking in adult rats exposed to chronic ethanol vapor in adolescence

Disturbance in sleep and activity rhythms are significant health risks associated with alcohol use during adolescence. Many investigators support the theory of a reciprocal relationship between disrupted circadian rhythms, sleep patterns, and alcohol usage. However, in human studies it is difficult to disentangle other factors (i.e. lifestyle, psychiatric, genetic) when determining what is causal in the relationship between substance use and sleep/activity disruptions. To this end, we used an animal model of adolescent alcohol exposure whereby male and female Wistar rats are exposed to 5 weeks of intermittent alcohol vapor during adolescence (P22-P57). Five days after ethanol vapor rats were allowed to select to drink alcohol or water in a two-bottle choice procedure for a period of 5 h, 4 days a week for 6 weeks. Activity data was collected using a "Fitbit-like" device during vapor exposure, during acute withdrawal, and after 3 weeks of protracted withdrawal. Significant changes in rest/wake activity and circadian measures were seen during 24-h withdrawal and after 3 weeks of withdrawal. Four weeks following withdrawal, the effects of the dual orexin antagonist, Daridorexant, (DAX 30 mg, 100 mg, or vehicle control), on alcohol drinking and rest and activity rhythms were assessed over a 24 h period. Both daridorexant doses led to changes in circadian measures and rest/wake activity patterns. These results showed that daridorexant reduced activity, but it did not improve rest quality as measured by the mean inactive episode duration and inactive fragmentation ratio. Additionally, we did not find a significant difference in drinking behavior in animals treated with the orexin antagonist. Thus, it appears that data from this animal model do not support the use of this drug to improve adolescent alcohol-induced sleep disturbance and/or to decrease alcohol drinking.

Pharmacodynamics of the orexin type 1 (OX1) receptor in colon cancer cell models: A two-sided nature of antagonistic ligands resulting from partial dissociation of Gq

BACKGROUND AND PURPOSE

Orexins have important biological effects on the central and peripheral nervous systems. Their primary ability is to regulate the sleep-wake cycle. Orexins and their antagonists, via OX1 receptor have been shown to have proapoptotic and antitumor effects on various digestive cancers cell models. We investigated, (1) the ability of orexin-A and its antagonists to regulate OX1 receptor expression at the cell surface and (2), how OX1 antagonists induced proapoptotic effect in cancer cells models.

EXPERIMENTAL APPROACH

The OX1 receptor internalisation is determined by imaging flow cytometry in colon cancer cell models and the OX1 receptor coupling to G proteins via bioluminescence resonance energy transfer and molecular dynamic simulation.

KEY RESULTS

Orexin-A induced rapid receptor internalisation within 15 min via β-arrestin 2 recruitment, whereas antagonists had no effect. Furthermore, Gq is critical for receptor internalisation and signalling pathways, and no other G proteins appear to be recruited. Surprisingly, antagonists induced recruitment and conformational changes in Gq protein. Simulated molecular dynamics of agonists/orexin receptor/Gq complexes show that antagonists exhibits a similar binding mode, stable at the binding site and show conformational changes of ECL2, similar to that of the agonists.

CONCLUSION AND IMPLICATIONS

OX1 receptor activation induced orexin/β-arrestin-dependent internalisation, which was independent of the apoptotic pathway induced by orexins and antagonists. In addition, antagonists activate the Gq protein, suggesting its putative partial dissociation. These results suggest that the development of OX1 receptor targeting molecules, including orexin antagonists with antitumor properties, may pave the way for innovative cancer therapies.

Transfer of the Dual Orexin Receptor Antagonist Daridorexant into Breast Milk of Healthy Lactating Women

The novel dual orexin receptor antagonist daridorexant was approved in 2022 for the treatment of adult patients with insomnia. The aim of this post-marketing study was to measure daridorexant and its major metabolites in breast milk and plasma of 10 healthy lactating subjects. This single-center, open-label study evaluated the transfer of the analytes into breast milk. A single dose of 50 mg was orally administered in the morning. Milk and blood samples were collected pre-dose and over a period of 72 h after dosing. The pharmacokinetics of daridorexant in milk and plasma were assessed including the cumulative amount and fraction of dose excreted, daily infant dose, and relative infant dose. Safety and tolerability were also investigated. All subjects completed the study. Daridorexant was rapidly absorbed into and distributed from plasma. Daridorexant and its major metabolites were measurable in breast milk. The cumulative total amount of daridorexant excreted over 72 h was 0.010 mg, which corresponds to 0.02% of the maternal dose. This corresponds to a mean daily infant dose of 0.009 mg/day and a relative infant dose of less than 0.22% over 24 h. The maternal safety profile was similar to that observed in previous studies. Low amounts of daridorexant and its metabolites were detected in the breast milk of healthy lactating women. Since the exposure and potential effects on the breastfed infant are unknown, a risk of somnolence or other depressant effects cannot be excluded.

Discovery, synthesis and SAR of 2-acyl-1-biarylmethyl pyrazolidines, dual orexin receptor antagonists designed as fast and short-acting sleeping drugs

Dual orexin receptor antagonists (DORAs) are approved for the treatment of sleep onset and/or sleep maintenance insomnia. In the present disclosure, we report the discovery of a new class of DORAs designed to treat sleep disorders requiring a fast onset and a short duration of action (<4 h). We used early human pharmacokinetic-pharmacodynamic (PK-PD) predictions and in vivo experiments to identify DORAs eliciting this specific hypnotic profile. A high-throughput screening campaign revealed hits based on a rarely precedented tricyclic pyrazolidine scaffold. After unsuccessful structure-activity-relationship (SAR) studies on this hit series, a scaffold hopping exercise, aimed at reducing the molecular complexity of the tricyclic scaffold, resulted in the discovery of the 2-acyl-1-biarylmethylpyrazolidine series. SAR studies on this achiral series gave rise to the lead compound DORA 42. In vitro and in vivo parameters of DORA 42, and its PK-PD simulation for human use are detailed.

International Union of Basic and Clinical Pharmacology CXIV: Orexin Receptor Function, Nomenclature and Pharmacology

The orexin system consists of the peptide transmitters orexin-A and -B and the G protein-coupled orexin receptors OX1 and OX2 Orexin receptors are capable of coupling to all four families of heterotrimeric G proteins, and there are also other complex features of the orexin receptor signaling. The system was discovered 25 years ago and was immediately identified as a central regulator of sleep and wakefulness; this is exemplified by the symptomatology of the disorder narcolepsy with cataplexy, in which orexinergic neurons degenerate. Subsequent translation of these findings into drug discovery and development has resulted to date in three clinically used orexin receptor antagonists to treat insomnia. In addition to sleep and wakefulness, the orexin system appears to be a central player at least in addiction and reward, and has a role in depression, anxiety and pain gating. Additional antagonists and agonists are in development to treat, for instance, insomnia, narcolepsy with or without cataplexy and other disorders with excessive daytime sleepiness, depression with insomnia, anxiety, schizophrenia, as well as eating and substance use disorders. The orexin system has thus proved an important regulator of numerous neural functions and a valuable drug target. Orexin prepro-peptide and orexin receptors are also expressed outside the central nervous system, but their potential physiological roles there remain unknown. SIGNIFICANCE STATEMENT: The orexin system was discovered 25 years ago and immediately emerged as an essential sleep-wakefulness regulator. This discovery has tremendously increased the understanding of these processes and has thus far resulted in the market approval of three orexin receptor antagonists, which promote more physiological aspects of sleep than previous hypnotics. Further, orexin receptor agonists and antagonists with different pharmacodynamic properties are in development since research has revealed additional potential therapeutic indications. Orexin receptor signaling is complex and may represent novel features.

Interaction modes of human orexin 2 receptor with selective and nonselective antagonists studied by NMR spectroscopy

Orexin neuropeptides have many physiological roles in the sleep-wake cycle, feeding behavior, reward demands, and stress responses by activating cognitive receptors, the orexin receptors (OX1R and OX2R), distributed in the brain. There are only subtle differences between OX1R and OX2R in the orthosteric site, which has hindered the rational development of subtype-selective antagonists. In this study, we utilized solution-state NMR to capture the structural plasticity of OX2R labeled with 13CH3-ε-methionine in complex with antagonists. Mutations in the orthosteric site allosterically affected the intracellular tip of TM6. Ligand exchange experiments with the subtype-selective EMPA and the nonselective suvorexant identified three methionine residues that were substantially perturbed. The NMR spectra suggested that the suvorexant-bound state exhibited more structural plasticity than the EMPA-bound state, which has not been foreseen from the close similarity of their crystal structures, providing insights into dynamic features to be considered in understanding the ligand recognition mode.

Effect of Daridorexant on the Pharmacokinetics of Midazolam, and on the Pharmacokinetics and Pharmacodynamics of Warfarin in Healthy Male Subjects

BACKGROUND AND OBJECTIVES

Daridorexant, a dual orexin receptor antagonist was recently approved for the treatment of insomnia at doses up to 50 mg once per night. This study investigated the effect of single-dose and multiple-dose daridorexant 50 mg at steady state on the pharmacokinetics (PK) of the cytochrome P450 (CYP) 3A4-sensitive substrate midazolam, and the effect of single-dose daridorexant 50 mg on the PK and pharmacodynamics (PD) of the CYP2C9-sensitive substrate warfarin.

METHODS

In this prospective, single-center, open-label, fixed-sequence, phase I, drug-drug interaction study, 18 healthy male subjects sequentially received Treatment A, B, and C in three periods. Treatment A consisted of a single oral concomitant administration of midazolam 2 mg and warfarin 25 mg on day 1 of the first period. Treatment B consisted of one oral administration of daridorexant 50 mg followed 1 h later by a single oral dose of midazolam 2 mg concomitantly with a single oral dose of warfarin 25 mg on day 1 and a once-daily oral administration of daridorexant 50 mg for 6 days of the second period. Treatment C consisted of a single oral administration of daridorexant 50 mg at steady state followed 1 h later by a single oral administration of midazolam 2 mg on day 1 of the third period. Blood samples were assessed for midazolam and S-warfarin PK, and PD (international normalized ratio and factor VII). Noncompartmental  PK parameters and PD variables were evaluated with geometric mean ratios and 90% confidence intervals of Treatment B/A versus C/A for midazolam, and treatment B/A for warfarin. Safety and tolerability of each treatment were also assessed.

RESULTS

Midazolam maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from 0 to 24 h (AUC0-24) were 1.13- and 1.42-fold higher, respectively, after single-dose administration of daridorexant 50 mg compared to administration of midazolam alone, while Cmax and AUC0-24 were 1.12- and 1.35-fold higher, respectively, after administration of daridorexant 50 mg once daily at steady state. Terminal half-life and time to maximum plasma concentration were comparable between treatments. Daridorexant had no influence on the PK and PD of warfarin. All treatments were safe and well tolerated.

CONCLUSIONS

Daridorexant at 50 mg is classified as a weak CYP3A4 inhibitor after single- and multiple-dose administration once daily at steady state. Daridorexant 50 mg did not induce CYP3A4 activity or inhibit CYP2C9 activity.

CLINICAL TRIAL REGISTRATION

This trial (NCT05480488) was registered on 29 July, 2022.

Emerging and upcoming therapies in insomnia

Insomnia, commonly treated with benzodiazepine (BZD) receptor agonists, presents challenges due to associated serious side effects such as abuse and dependence. To address these concerns, many researches have been conducted to develop and advance both pharmacological and non-pharmacological interventions. Dual orexin receptor antagonists (DORAs), which include suvorexant, daridorexant and lemborexant, have recently been approved by United States Food and Drug Administration (US FDA) as a novel pharmacotherapeutic alternative. Unlike BZD receptor agonists that act as positive allosteric modulators of the gamma-aminobutyric acid type A subunit alpha 1 receptor, DORAs function by binding to both orexin receptor types 1 and 2, and inhibiting the action of the wake-promoting orexin neuropeptide. These drugs induce normal sleep without sleep stage change, do not impair attention and memory performance, and facilitate easier awakening. However, more real-world safety information is needed. Selective orexin-2 receptor antagonists (2-SORAs) is under clinical developments. This review provides an overview of the mechanism of action in relation to insomnia, pharmacokinetics, efficacy and safety information of DORAs and SORA. According to insomnia management guidelines, the first-line treatment for chronic insomnia is cognitive behavioral therapy for insomnia (CBT-I). Although it has proven effective in improving sleep-related quality of life, it has several restrictions limitations due to a face-to-face format. Recently, prescription digital therapy such as Somryst® was approved by US FDA. Somryst®, a smartphone app-based CBT-I, demonstrated meaningful responses in patients. However, digital limitations may impact scalability. Overall, these developments offer promising alternatives for insomnia treatment, emphasizing safety, efficacy, and accessibility.

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.

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.

Comparative efficacy of hypnotics in young and middle-aged adults with insomnia: a systematic review and network meta-analysis

OBJECTIVE/BACKGROUND

Insomnia is highly prevalent in modern society. However, the hierarchical selection of hypnotics in young and middle-aged adults with insomnia remains unclear. We aimed to compare the efficacy and daytime drowsiness associated with different hypnotics for treating insomnia in young and middle-aged adults.

METHODS

We searched Embase, PubMed, Cochrane Library, and ProQuest Dissertations and Theses A&I databases from inception until December 15, 2021. We also manually searched reference lists and relevant publications. The literature search, data collection, and risk of bias evaluation were all carried out separately by pairs of reviewers. We included randomized control trials (RCTs) that compared hypnotics approved by the Food and Drug Administration. The R and Stata software were both used to perform the meta-analysis.

RESULTS

In total, 117 RCTs comprising 22,508 participants with the age of 18 to 65 years were included. Assessment of the efficacy of the hypnotics and adverse events (drowsiness) revealed that zolpidem improved all objective sleep parameters (oTST, oSOL, oWASO, and oSE), zopiclone increased oTST and oSE and reduced oSOL, and daridorexant increased oTST and reduced oWASO. Regarding subjective sleep outcomes, zolpidem exhibited beneficial effects on sTST, sSOL, and sWASO. Zaleplon reduced sSOL, and zopiclone was the recommended hypnotic for improving SQ. Zolpidem was associated with drowsiness effect (odds ratio = 1.82; 95% confidence interval = 1.25 to 2.65). The results of sensitivity analysis remained unchanged after the exclusion of studies reporting long-term effects.

CONCLUSION

Zolpidem is recommended for managing sleep-onset insomnia and sleep maintenance insomnia but should be used with caution because of daytime drowsiness effects. Daridorexant is recommended as a promising agent for managing sleep maintenance insomnia.

Targeting orexin receptors: Recent advances in the development of subtype selective or dual ligands for the treatment of neuropsychiatric disorders

Orexin-A and orexin-B, also named hypocretin-1 and hypocretin-2, are two hypothalamic neuropeptides highly conserved across mammalian species. Their effects are mediated by two distinct G protein-coupled receptors, namely orexin receptor type 1 (OX1-R) and type 2 (OX2-R), which share 64% amino acid identity. Given the wide expression of OX-Rs in different central nervous system and peripheral areas and the several pathophysiological functions in which they are involved, including sleep-wake cycle regulation (mainly mediated by OX2-R), emotion, panic-like behaviors, anxiety/stress, food intake, and energy homeostasis (mainly mediated by OX1-R), both subtypes represent targets of interest for many structure-activity relationship (SAR) campaigns carried out by pharmaceutical companies and academies. However, before 2017 the research was predominantly directed towards dual-orexin ligands, and limited chemotypes were investigated. Analytical characterizations, including resolved structures for both OX1-R and OX2-R in complex with agonists and antagonists, have improved the understanding of the molecular basis of receptor recognition and are assets for medicinal chemists in the design of subtype-selective ligands. This review is focused on the medicinal chemistry aspects of small molecules acting as dual or subtype selective OX1-R/OX2-R agonists and antagonists belonging to different chemotypes and developed in the last years, including radiolabeled OX-R ligands for molecular imaging. Moreover, the pharmacological effects of the most studied ligands in different neuropsychiatric diseases, such as sleep, mood, substance use, and eating disorders, as well as pain, have been discussed. Poly-pharmacology applications and multitarget ligands have also been considered.

Daridorexant, an Orexin Receptor Antagonist for the Management of Insomnia

BACKGROUND

Insomnia is a common sleep disorder that is diagnosed primarily by patients' subjective reported symptoms. Daridorexant is a new dual orexin receptor antagonist that was recently approved by Food and Drug Administration for insomnia characterized by difficulty falling asleep and/or maintaining sleep.

MECHANISM OF ACTION, PHARMACODYNAMICS, AND PHARMACOKINETICS

The orexin neuropeptide signaling system plays a role in wakefulness, and blocking the wake-promoting neuropeptides results in diminished wake signaling, thus exerting a sedative effect using an entirely different mechanism of action than the classical sleep promoting agents. The drug has quick onset of action, high volume of distribution, and high protein binding. Pharmacokinetics and pharmacodynamic parameters were similar in patients of different sex and age and were not significantly affected by race, body size, or mild-to-moderate kidney impairment. Dose limitation to 25 mg in moderate liver impairment and no use in severe liver impairment are recommended. The drug undergoes hepatic CYP3A4 metabolism; thus, caution with strong CYP3A4 inhibitors and inducers is warranted.

CLINICAL TRIALS

The drug was approved based on phase 3 trials involving study 1 and study 2. Study 1 noted daridorexant at doses of 25 and 50 mg demonstrated a statistically significant improvement in wake time after sleep onset, latency to persistent sleep, and self-reported total sleep time against placebo at months 1 and 3. Similarly in study 2, compared with placebo, the 25 mg dose demonstrated statistically significant improvement in wake time after sleep onset, latency to persistent sleep, and self-reported total sleep time at months 1 and 3. Treatment-emergent adverse events were similar for daridorexant and placebo, with nasopharyngitis and headache most frequently reported.

THERAPEUTIC ADVANCE

Daridorexant is a novel agent with demonstrated efficacy in sleep onset and maintenance and decrease in daytime sedation. Preliminary results from a 1-year extension study note similar incidences of mild-to-moderate side effects as noted in previous trials. Further studies are needed to establish its place in the pharmacological treatment of insomnia.

Daridorexant, a Recently Approved Dual Orexin Receptor Antagonists (DORA) in Treatment of Insomnia

Insomnia is one of the major challenges in medical science nowadays as it leads to great socio-economic burden by impairing daytime function as well as the development of exhaustion, depression, and memory disturbance in affected individuals. Several important classes of drugs have been tried, including the BZDs and non-BZD hypnotics. Available drugs to combat this disease have the limitations of abuse potential, tolerance, and cognitive impairment. In some instances, withdrawal symptoms have been observed upon the abrupt cessation of those drugs. The Orexin system has been very recently targeted as a therapeutic option to overcome those limitations. Treatment of insomnia with Daridorexant as a Dual Orexin Receptor Antagonist (DORA) has been evaluated in several preclinical and clinical studies. Available information obtained from those studies has shown a promising future for this drug in the management of insomnia. Beyond its effectiveness in insomnia, it has been successfully used in patients suffering from obstructive sleep apnoea, chronic obstructed airway disease (COAD), Alzheimer's disease (AD), hypertension, and cardiovascular disorders. Larger studies need to address the safety issues as well as obtain robust pharmacovigilance information to safeguard the risk-benefit aspect of this drug in insomniac adults.

Daridorexant in Insomnia Disorder: A Profile of Its Use

Daridorexant (Quviviq™) is a useful option for the treatment of insomnia disorder, which has shown efficacy in younger and older adults. It antagonises the orexin receptors, thereby reducing the wake drive. Daridorexant is the first dual orexin receptor antagonist to be approved for the treatment of chronic insomnia in the EU and has been approved for insomnia in the USA. In phase 3 clinical trials, daridorexant dose-dependently improved objective latency to persistent sleep, objective wake time after sleep onset, subjective total sleep time and, at the 50 mg dose, subjective daytime functioning compared with placebo. Daridorexant was generally well tolerated. Adverse events (AEs) commonly associated with insomnia drugs, such as somnolence, fatigue and dizziness, occurred at a similar or slightly greater frequency with daridorexant than with placebo. Falls occurred at a similar or lower frequency with daridorexant than with placebo. Most AEs were mild in severity and the incidence was not dose-dependent. The efficacy of daridorexant was maintained during a 12-month extension trial, with no new safety or tolerability concerns.

The Metabolism of the Dual Orexin Receptor Antagonist Daridorexant

Daridorexant is a dual orexin receptor antagonist developed for the treatment of insomnia disorder and has shown improvement in sleep outcomes and daytime functioning. The present work describes its biotransformation pathways in vitro and in vivo and provides a cross-species comparison between the animal species used in preclinical safety assessments and man.Daridorexant clearance is driven by metabolism along seven distinct pathways. Metabolic profiles were characterized by downstream products while primary metabolic products were of minor importance. The metabolic pattern differed between rodent species, with the rat reflecting the human pattern better than the mouse.In rodents, daridorexant is mostly excreted via the bile after extensive metabolism while urinary excretion was negligible in the rat. Only traces of parent drug were detected in urine, bile or faeces.Daridorexant has three major metabolites which are well covered in these preclinical safety species. All of them retain some residual affinity towards orexin receptors. However, none of these is considered to contribute to the pharmacological effect of daridorexant as their active concentrations in human brain are too low.

Daridorexant for the treatment of insomnia disorder: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Daridorexant is a novel dual orexin receptor antagonist that has shown efficacy as a treatment for insomnia in multiple randomized clinical trials. However, the efficacy and safety of daridorexant for treatment of insomnia disorder has not been characterized comprehensively in the literature. Therefore, we performed a meta-analysis of available studies. We performed a meta-analysis to systematically evaluate the efficacy and safety of daridorexant for treatment of insomnia disorder.

METHODS

MEDLINE, Embase, Cochrane Library, and Clinicaltrials.gov for randomized controlled trials were systematically searched up to February 2022. Relative risk and standard mean difference were used to evaluate clinical outcomes.

RESULTS

We pooled 2271 patients from 4 randomized clinical trials, and evaluated efficacy endpoints. We found that 50 mg of daridorexant was superior to placebo for 4 efficacy outcomes including wake time after sleep onset, latency to persistent sleep, subjective total sleep time, and Insomnia Daytime Symptoms and Impacts Questionnaire domain score (P < .05). In addition, there were no significant differences (P > .05) in adverse events between daridorexant and placebo.

CONCLUSIONS

Different dosages of daridorexant were tested for treatment of insomnia; however, 5 and 10 mg are not available because of issues of suboptimal effectiveness. Daridorexant showed better efficacy and safety for treatment of insomnia disorder at doses of 25 and 50 mg.

Safety and efficacy of daridorexant in the treatment of insomnia: a systematic review and meta-analysis of randomized controlled trials

Daridorexant is a novel dual orexin receptor antagonist used in treating insomnia disorder. Daridorexant improves sleep quality without impairing daytime functioning. We assess the safety and efficacy of this novel drug in the treatment of insomnia. We performed a systematic search for electronic databases in SCOPUS, PubMed, Web of Science and the Cochrane library. Seven randomized controlled trials were included in this review, with 2425 participants enrolled. Daridorexant was superior to placebo in reducing wake time after sleep onset (MD = -13.26; 95% CI, -15.48 to -11.03; P < 0.00001), latency to persistent sleep (MD = -7.23; 95% CI, -9.60 to -4.85; P < 0.00001), with increasing the total sleep time (MD = 14.80; 95% CI, 11.18-18.42; P < 0.00001) and subjective total sleep time (MD = 14.80; 95% CI, 11.18-18.42], P < 0.00001). The 25 mg and 50 mg were the most officious doses. Treatment with daridorexant has resulted in a slightly higher incidence of adverse events [risk ratio (RR) = 1.19; 95% CI, 1.05-1.35;, P = 0.005], specifically somnolence (RR = 1.19; 95% CI, 1.13-3.23; P = 0.005) and fatigue (RR = 2.01; 95% CI, 1.21-3.36; P = 0.007). Daridorexant is superior to placebo in improving sleep quality. However, the drug resulted in a slightly higher incidence of adverse events, including somnolence and fatigue.

Population pharmacokinetic modeling of daridorexant, a novel dual orexin receptor antagonist

The analysis aimed at identifying subject-specific characteristics (covariates) influencing exposure to daridorexant and quantification of covariate effects to determine clinical relevance. Data from 13 phase I, two phase II, and two phase III studies were pooled to develop a population pharmacokinetic model describing daridorexant concentration over time. Covariate effects were quantified based on model predictions. A two-compartment model with dose-dependent bioavailability, absorption lag time, linear absorption, and nonlinear elimination described the data best. Statistically significant covariates were food status on absorption (lag time and rate constant), time of drug administration (morning, bedtime) on absorption rate constant, lean body weight on central volume of distribution and elimination, fat mass on peripheral volume of distribution and intercompartmental drug transfer, and age and alkaline phosphatase on elimination. Age, lean body weight, fat mass, and alkaline phosphatase influence exposure (area under the curve, time of maximum concentration after dose administration, maximum plasma concentration, and next-morning concentration) to a limited extent, that is, less than 20% difference from a typical subject. Morning administration is not relevant for daridorexant use by insomnia patients. The food effect with simultaneous intake of a high-fat, high-calorie food is an extreme-case scenario unlikely to occur in clinical practice. Body composition, alkaline phosphatase, and age showed clinically negligible effects on exposure to daridorexant. Lean body weight and fat mass described the pharmacokinetics of daridorexant better than other body size descriptors (body weight, height, body mass index), suggesting a convenient physiological alternative to reduce the number of covariates in population pharmacokinetic models. The results indicate that differences between subjects do not require dose adjustments.

Orexin Receptor Antagonists and Insomnia

PURPOSE OF REVIEW

We review recent evidence on the use of orexin receptor antagonists (ORAs) for treating insomnia. We evaluate studies on five dual ORAs and one selective ORA.

RECENT FINDINGS

Research on suvorexant in recent years gradually focus on comorbid insomnia, while lemborexant and daridorexant were still being validated in primary insomnia. Almorexant is now mainly used as a commercial specific inhibitor of the orexin system in animal studies due to safety issues. Although filorexant has also shown a certain sleep-promoting effect, there are few clinical or experimental studies on sleep-related aspects of filorexant in recent years. As for selective ORAs, orexin receptor 2 antagonist seltorexant still has not yet reached phase 3. High-quality clinical trials in insomnia populations are needed which directly compare authorized ORAs and investigate non-approved ORAs, the use of ORAs in comorbid insomnia, and the orexin signaling system pathophysiology in insomnia.

A Comprehensive Review of Daridorexant, a Dual-Orexin Receptor Antagonist as New Approach for the Treatment of Insomnia

Insomnia affects 4.4-4.8% of the world's population, but because the effect of hypnotic drugs is limited and may cause harmful side-effects, scientists are turning their attention to developing drugs that act on the orexin system. Daridorexant, a selective dual-orexin receptor antagonist (DORA), has exhibited promising results in both animal and human studies. Its activity was evaluated based on the physiology-based pharmacodynamic and pharmacokinetic model. The use of daridorexant is considered safe, with no clinically significant side-effects including deprivation of next-morning residual effects. In this manuscript we conducted a comprehensive review of daridorexant including pharmacodynamics, animal and human research, pharmacokinetics and safety.

Efficacy and Safety of Daridorexant in Older and Younger Adults with Insomnia Disorder: A Secondary Analysis of a Randomised Placebo-Controlled Trial

Background and Objective

The dual orexin receptor antagonist daridorexant, studied in two phase III trials, dose-dependently improved objective and subjective sleep variables and daytime functioning in adults with insomnia. Because treatment of insomnia in older adults is challenging and has limited options, the purpose of the current analysis was to further analyse the phase III trial studying the higher doses of daridorexant, those that showed efficacy (daridorexant 50 mg, daridorexant 25 mg and placebo, nightly for 3 months), and compare the safety and efficacy of daridorexant in patients aged ≥ 65 (‘older adults’) to those aged < 65 years (‘younger adults’).

Methods

Analyses by age (≥ 65 years, n = 364; < 65 years, n = 566) were performed on data from the randomised, double-blind, placebo-controlled Trial 1 in adult patients with insomnia (NCT03545191). Efficacy endpoints included a change from baseline at month 1 and month 3 in polysomnography-measured wake after sleep onset (WASO) and latency to persistent sleep (LPS), self-reported total sleep time (sTST) and daytime functioning assessed using the validated Insomnia Daytime Symptoms and Impacts Questionnaire (IDSIQ). Safety endpoints included adverse events and the Visual Analog Scale for morning sleepiness.

Results

At baseline, mean [standard deviation] WASO was numerically greater (110 [39] vs 92 [38] min) in older than younger adults, while LPS was comparable (~ 65 min). Mean baseline IDSIQ total and all domain scores were numerically lower (i.e. better) in older adults. Daridorexant caused similar reductions in WASO and LPS, and similar increases in sTST, from baseline, in both age groups; improvements were numerically greater with daridorexant 50 mg than 25 mg. At month 3, daridorexant 50 mg, compared with placebo, decreased WASO by a least-squares mean of 19.6 (95% confidence interval 9.7, 29.5) in older patients versus 17.4 min (10.7, 24.0) in younger patients and decreased LPS by a least-squares mean of 14.9 (7.5, 22.3) in older patients versus 9.7 min (3.7, 15.7) in younger patients. Daridorexant 50 mg increased sTST from baseline to month 3 by a least-squares mean of 59.9 (49.6, 70.3) in older patients versus 57.1 min (48.9, 65.3) in younger patients. Daridorexant 50 mg progressively improved IDSIQ total and domain scores from week 1 onwards similarly in both groups; daridorexant 25 mg improved IDSIQ scores, but only in younger adults. In both age groups, in comparison with placebo, the overall incidence of adverse events was comparable, and there were fewer falls on daridorexant. Daridorexant improved Visual Analog Scale morning sleepiness in both groups; daridorexant 50 mg increased the mean (standard deviation) Visual Analog Scale morning sleepiness score by 15.9 (20.7) in older adults and by 14.9 (18.7) in younger adults from baseline to month 3. In older adults, there was one case of sleep paralysis, and no cases of narcolepsy, cataplexy, or complex sleep behaviour.

Conclusions

In older patients with insomnia, as in younger patients, the efficacy of daridorexant is maximal on night-time and daytime variables at the higher dose of 50 mg. Older patients particularly require this dose to improve daytime functioning. Older patients are not at an increased risk of adverse events or residual effects the next morning after night-time administration of daridorexant, even at 50 mg. The dose of daridorexant does not need to be decreased for older patients.

Clinical Trial Registration

ClinicalTrials.gov (NCT03545191) [first posted: 4 June, 4 2018], https://clinicaltrials.gov/ct2/show/NCT03545191.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40266-022-00977-4.

The burden of chronic insomnia (difficulty in falling/staying asleep or not getting enough sleep) increases with age yet treatment options in older patients are limited. In older patients, because of a risk of side effects, guidelines suggest caution when prescribing sleep medications and, for some drugs, recommend starting at a lower dose. Daridorexant was approved in 2022 for the treatment of insomnia in adults following positive results in two trials that showed daridorexant significantly improved night-time sleep and daytime functioning over 3 months of treatment in adults with insomnia. Approximately 40% of patients taking part in these trials were aged 65 years or older. This current analysis compared the safety and benefits of daridorexant in older adults (aged at least 65 years) and younger adults (aged less than 65 years) in the trial that administered the highest two doses of daridorexant, 25 and 50 mg. The results showed that the benefits of daridorexant were comparable in both age groups over 3 months; compared with placebo, daridorexant improved night-time sleep (reduced time awake during the night, reduced time to fall asleep and increased total sleep time) and daytime functioning—patients had less daytime sleepiness and a better mood and feeling of alertness. In older patients, the benefits, particularly for daytime functioning, were greatest at the higher 50-mg dose, without any increase in side effects. Both doses of daridorexant were equally well tolerated in the two age groups, indicating that treatment with daridorexant at 50 mg can be safely started in older patients.

Daridorexant for the Treatment of Insomnia

Purpose of Review

Insomnia is a complex sleeping disorder that affects the lives of many individuals worldwide. Insomnia often occurs in the presence of coexisting comorbidities making it a complex disorder that requires a multifactorial approach to therapy. First-line therapy is cognitive-behavioral therapy for insomnia (CBT-I). Pharmacotherapy for insomnia falls into four classes based on mechanism of action: benzodiazepine receptor agonists (BZRAs), histamine receptor antagonists, melatonin receptor agonists, and dual orexin receptor antagonists (DORAs).

Recent Findings

Daridorexant is a dual orexin type 1 and types 2 (OX1 and OX2) receptor antagonist that was recently approved by the US FDA for the treatment of adults suffering from insomnia. It was shown to be effective in reducing insomnia symptoms, increasing daytime functioning, and improving the overall quality of sleep. Daridorexant offers patients relief from insomnia while avoiding the severe side effects and dependency issues of traditional treatments like benzodiazepines and sedatives.

Summary

In this article, we review the most recent data on insomnia treatments and summarize the safety and efficacy of daridorexant in treating insomnia.

Hypocretins (orexins): The ultimate translational neuropeptides

The hypocretins (Hcrts), also known as orexins, are two neuropeptides produced exclusively in the lateral hypothalamus. They act on two specific receptors that are widely distributed across the brain and involved in a myriad of neurophysiological functions that include sleep, arousal, feeding, reward, fear, anxiety and cognition. Hcrt cell loss in humans leads to narcolepsy with cataplexy (narcolepsy type 1), a disorder characterized by intrusions of sleep into wakefulness, demonstrating that the Hcrt system is nonredundant and essential for sleep/wake stability. The causal link between Hcrts and arousal/wakefulness stabilisation has led to the development of a new class of drugs, Hcrt receptor antagonists to treat insomnia, based on the assumption that blocking orexin-induced arousal will facilitate sleep. This has been clinically validated: currently, two Hcrt receptor antagonists are approved to treat insomnia (suvorexant and lemborexant), with a New Drug Application recently submitted to the US Food and Drug Administration for a third drug (daridorexant). Other therapeutic applications under investigation include reduction of cravings in substance-use disorders and prevention of neurodegenerative disorders such as Alzheimer's disease, given the apparent bidirectional relationship between poor sleep and worsening of the disease. Circuit neuroscience findings suggest that the Hcrt system is a hub that integrates diverse inputs modulating arousal (e.g., circadian rhythms, metabolic status, positive and negative emotions) and conveys this information to multiple output regions. This neuronal architecture explains the wealth of physiological functions associated with Hcrts and highlights the potential of the Hcrt system as a therapeutic target for a number of disorders. We discuss present and future possible applications of drugs targeting the Hcrt system for the treatment of circuit-related neuropsychiatric and neurodegenerative conditions.

Orexin Signaling: A Complex, Multifaceted Process

The orexin system comprises two G protein-coupled receptors, OX1 and OX2 receptors (OX1R and OX2R, respectively), along with two endogenous agonists cleaved from a common precursor (prepro-orexin), orexin-A (OX-A) and orexin-B (OX-B). For the receptors, a complex array of signaling behaviors has been reported. In particular, it becomes obvious that orexin receptor coupling is very diverse and can be tissue-, cell- and context-dependent. Here, the early signal transduction interactions of the orexin receptors will be discussed in depth, with particular emphasis on the direct G protein interactions of each receptor. In doing so, it is evident that ligands, additional receptor-protein interactions and cellular environment all play important roles in the G protein coupling profiles of the orexin receptors. This has potential implications for our understanding of the orexin system's function in vivo in both central and peripheral environments, as well as the development of novel agonists, antagonists and possibly allosteric modulators targeting the orexin system.

Daridorexant: First Approval

Daridorexant (Quviviq™; Idorsia Pharmaceuticals Ltd.) is an orally administered dual orexin type 1 and type 2 (OX₁ and OX₂) receptor antagonist (DORA) being developed for the treatment of insomnia. It was selected from a pool of drug candidates on the basis of an expected effect duration of ≈ 8 h at a dose of 25 mg, with a half-life intended to minimize residual effects that might impair daytime functioning. Based on the results of two pivotal phase III trials, daridorexant was recently approved in the USA for the treatment of adult patients with insomnia characterized by difficulties with sleep onset and/or sleep maintenance. This article summarizes the milestones in the development of daridorexant leading to this first approval.

Effects of TS-142, a novel dual orexin receptor antagonist, on sleep in patients with insomnia: a randomized, double-blind, placebo-controlled phase 2 study

RATIONALE

Novel compound with potent antagonistic activity against orexin receptors may be new treatment option for patients with insomnia.

OBJECTIVE

The aim was to investigate the efficacy and safety of single oral doses of the dual orexin receptor antagonist TS-142 in patients with insomnia.

METHODS

This multicenter, double-blind, crossover randomized clinical trial included non-elderly patients with insomnia. Patients were randomized to receive single doses of placebo and TS-142 at doses of 5, 10, and 30 mg in one of four different sequences, with a 7-day washout period between treatments. Primary efficacy endpoints were latency to persistent sleep (LPS) and wake time after sleep onset (WASO) measured by polysomnography.

RESULTS

Twenty-four patients were included (mean age 50.3 ± 10.5 years; mean duration of insomnia 5.71 ± 8.68 years). Least-squares mean differences (95% confidence interval) from placebo in LPS with 5, 10, and 30 mg TS-142 were - 42.38 (- 60.13, - 24.63), - 42.10 (- 60.02, - 24.17), and - 44.68 (- 62.41, - 26.95) minutes, respectively (all p < 0.001). Least-squares mean differences (95% confidence interval) from placebo in WASO with 5, 10, and 30 mg TS-142 were - 27.52 (- 46.90, - 8.14), - 35.44 (- 55.02, - 15.87), and - 54.69 (- 74.16, - 35.23) minutes, respectively (all p < 0.01). Self-reported aspects of sleep initiation and sleep quality, determined using the Leeds Sleep Evaluation Questionnaire (LSEQ), were also improved with TS-142 administration versus placebo. TS-142 was well tolerated; all adverse events were mild or moderate and none were serious.

CONCLUSION

Single-dose TS-142 was well tolerated and had clinically relevant effects on objective and subjective sleep parameters in patients with insomnia.

CLINICAL TRIAL REGISTRATION

JapicCTI173570 (www.

CLINICALTRIALS

jp); NCT04573725 (www.

CLINICALTRIALS

gov).

What evidence is there for implicating the brain orexin system in neuropsychiatric symptoms in dementia?

Neuropsychiatric symptoms (NPS) affect people with dementia (PwD) almost universally across all stages of the disease, and regardless of its exact etiology. NPS lead to disability and reduced quality of life of PwD and their caregivers. NPS include hyperactivity (agitation and irritability), affective problems (anxiety and depression), psychosis (delusions and hallucinations), apathy, and sleep disturbances. Preclinical studies have shown that the orexin neuropeptide system modulates arousal and a wide range of behaviors via a network of axons projecting from the hypothalamus throughout almost the entire brain to multiple, even distant, regions. Orexin neurons integrate different types of incoming information (e.g., metabolic, circadian, sensory, emotional) and convert them into the required behavioral output coupled to the necessary arousal status. Here we present an overview of the behavioral domains influenced by the orexin system that may be relevant for the expression of some critical NPS in PwD. We also hypothesize on the potential effects of pharmacological interference with the orexin system in the context of NPS in PwD.

Pharmacokinetic and pharmacodynamic interactions between daridorexant, a dual orexin receptor antagonist, and citalopram in healthy subjects

Daridorexant (ACT-541468) is a new dual orexin receptor antagonist being evaluated for the treatment of insomnia, which is a common comorbidity of depression and anxiety. Therefore, daridorexant is likely to be administered concomitantly with agents (e.g., citalopram) used to treat these disorders. In this single-centre, single-blind, randomized, placebo-controlled, sequential design Phase 1 study with the inclusion of two double-blind crossover parts, the pharmacokinetic (PK; blood sampling at regular intervals) and pharmacodynamic (PD; battery of objective and subjective PD tests performed at regular intervals) interactions between daridorexant (50 mg) and citalopram (20 mg, single dose and at steady state) as well as the safety/tolerability in healthy subjects were investigated. There were no relevant effects of citalopram (single dose/steady state) on daridorexant exposure and vice versa. PD variables measured after morning administration of daridorexant alone showed effects consistent with a sleep-promoting compound. Only co-administration of daridorexant with citalopram at steady state led to relevant changes in objective (unstable tracking) and subjective (visual analogue scale alertness and Karolinska Sleepiness Scale) PD endpoints compared to daridorexant alone. No serious or severe adverse events were reported, while no clinically relevant treatment-emergent effects on ECG parameters, clinical laboratory, or vital signs were observed. In conclusion, the co-administration of daridorexant and citalopram lead to only minor changes in PK parameters, while performance of PD assessments following co-administration were mainly driven by the expected central nervous system effects of daridorexant. Doses up to 50 mg daridorexant can be safely co-administered with citalopram.

Abuse potential assessment of the new dual orexin receptor antagonist daridorexant in recreational sedative drug users as compared to suvorexant and zolpidem

STUDY OBJECTIVES

Abuse potential properties have been reported for the dual orexin receptor antagonists (DORAs) suvorexant and lemborexant. Daridorexant is a new DORA currently in late-stage clinical development. This randomized, double-blind, double-dummy, placebo- and active-controlled 6-period crossover study assessed its abuse potential in healthy recreational sedative drug users (n=63).

METHODS

In each study period, a single, oral, morning dose of either daridorexant (50, 100, 150 mg), placebo, or active control, i.e., suvorexant (150 mg) or zolpidem (30 mg), was administered. Primary pharmacodynamic endpoint was the Emax of the Drug-liking visual analog scale (VAS) assessed over 24 h. Several secondary subjective and objective pharmacodynamic endpoints were also assessed.

RESULTS

Study validity was confirmed based on drug-liking of suvorexant and zolpidem greater than placebo applying a pre-defined 15-point validity margin (p<0.0001). Drug-liking VAS Emax (mean; 95% CI) of daridorexant at 50 mg (73.2; 69.0-77.5) was significantly lower compared to suvorexant (80.7; 77.0-84.5) and zolpidem (79.9; 76.2-83.5) (p<0.001), but similar at 100 mg (79.1; 75.0-83.3) and 150 mg (81.3; 77.7, 84.8). Such dose-related patterns were also observed for most secondary endpoints. At each daridorexant dose, Drug-liking VAS scores were greater than placebo. Both control drugs and daridorexant were safe and the pharmacokinetics of daridorexant was consistent with earlier trials indicating quick absorption and elimination.

CONCLUSIONS

In this large, valid human abuse potential study, daridorexant showed dose-related drug-liking among recreational sedative drug users with lower effects at the highest phase-3 dose, and similar effects at higher doses compared to supratherapeutic doses of suvorexant and zolpidem.

Effect of gastric pH and of a moderate CYP3A4 inducer on the pharmacokinetics of daridorexant, a dual orexin receptor antagonist

AIM

Daridorexant is a dual orexin receptor antagonist developed for the treatment of insomnia. The solubility of daridorexant is pH dependent and daridorexant has been shown to be a sensitive CYP3A4 substrate when co-administered with moderate CYP3A4 inhibitors. The purpose of this study was to assess the effect of an increased gastric pH on daridorexant pharmacokinetics (PK) and the extent of interaction when daridorexant is co-administered with a moderate CYP3A4 inducer.

METHODS

In this prospective, single-centre, randomized, open-label study, 24 male subjects consecutively received four treatments, i.e., daridorexant 50 mg single dose; famotidine 40 mg single dose + daridorexant 50 mg single dose; efavirenz 600 mg once a day (o.d.) during 10 days; and daridorexant 50 mg single dose + efavirenz 600 mg o.d. for 2 days. Plasma PK parameters of daridorexant were derived by noncompartmental analysis. Standard safety and tolerability evaluations were analysed descriptively.

RESULTS

When daridorexant administration was preceded by administration of famotidine, daridorexant C_max decreased by 39%, geometric means ratio (GMR) (90% confidence interval (90% CI)): 0.61 (0.50, 0.73). AUC_0-∞ remained unchanged. In the presence of steady-state efavirenz, daridorexant C_max , AUC_0-∞ , and t_½ decreased by approximately 35% (GMR (90% CI)): 0.65 (0.54, 0.78), 61% (0.39 (0.348, 0.44), and 35% (0.65 (0.58, 0.73), respectively. T_max remained unaffected. All treatments containing daridorexant were well tolerated.

CONCLUSION

Daridorexant 50 mg can be administered concomitantly with gastric pH modifiers or with moderate CYP3A4 inducers without dose adaptation based on efficacy observed at lower doses in Phase 3 studies.

Impact of Daridorexant, a Dual Orexin Receptor Antagonist, on Cardiac Repolarization Following Bedtime Dosing: Results from a Thorough QT Study Using Concentration-QT Analysis

BACKGROUND AND OBJECTIVE

Daridorexant is a new dual orexin receptor antagonist currently in late-stage clinical development for the treatment of insomnia. This randomized, double-blind, placebo-controlled, four-period crossover study investigated the effect of daridorexant at a therapeutic and supratherapeutic dose on QT interval duration.

METHODS

Thirty-six healthy subjects received single oral doses of daridorexant (50 mg; 200 mg), moxifloxacin (400 mg; open label), and placebo. All treatments were administered at bedtime to mimic therapeutic practice. The primary analysis was based on linear mixed-effects concentration-QT modelling. Triplicate ECG data were extracted from Holter recordings at baseline and until 24 h post dosing at time points matching those for pharmacokinetic sampling. Plasma concentrations of daridorexant were determined over 24 h.

RESULTS

Assay sensitivity was demonstrated based on mean baseline- and placebo-corrected QT interval using Fridericia's formula (ΔΔQTcF) > 5 ms following moxifloxacin administration (p < 0.01). Following daridorexant administration, mean (90% confidence interval, CI) ΔΔQTcF was 1.40 ms (0.48; 2.32 ms) and 1.84 ms (-0.12; 3.79 ms) at the C_max of 747 ng/mL (50 mg dose) and 1809 ng/mL (200 mg dose), respectively, i.e., the upper bounds of the CIs were < 10 ms defined as threshold of regulatory concern. Lack of relevant QT prolongation was confirmed by secondary by-time point analysis and absence of relevant findings in the categorical outlier analysis. Daridorexant was safe and well tolerated and its pharmacokinetics were consistent with previous data.

CONCLUSION

Daridorexant does not impair cardiac repolarization evidenced by absence of relevant QT prolongation at therapeutic and supratherapeutic doses. Clinical Trials Registration ID: NCT04250506.

Pharmacokinetics of daridorexant, a dual orexin receptor antagonist, are not affected by renal impairment

The aim of this study was to evaluate the impact of renal impairment on the pharmacokinetics (PKs), safety, and tolerability of daridorexant, a dual orexin receptor antagonist intended for the treatment of insomnia. A single‐center, open‐label study evaluated the PKs of daridorexant in patients with severe renal function impairment (SRFI; determined by creatinine clearance using the Cockcroft‐Gault equation; N = 8) not on dialysis, and in matched control subjects (based on sex, age, and body weight; N = 7). A single oral dose of daridorexant 25 mg was orally administered in the morning. Blood samples were collected up to 72 h postdose for PK assessments of daridorexant. In patients with SRFI, maximum plasma concentrations (C_max; geometric mean ratio [GMR] and 90% confidence interval [CI]: 0.94 [0.60–1.46]), time to reach C_max (T_max; median difference [90% CI] of −0.25 h [−0.75 to 0.25]), and half‐life (GMR [90% CI] of 0.99 [0.66–1.48]), were virtually unchanged. Exposure (area under the plasma concentration‐time profile) to daridorexant was slightly higher in patients with SRFI than in control subjects with the GMR (90% CI) being 1.16 (0.63–2.12). No safety issue of concern was detected as all adverse events were transient and of mild or moderate intensity, and no treatment‐related effects on vital signs, clinical laboratory, or electrocardiogram variables were observed following daridorexant administration in patients with SRFI and control subjects. Based on these observations, PK alterations of daridorexant due to renal function impairment are not considered of clinical relevance and no dose adjustment is necessary in these patients.

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.

Application of physiologically based pharmacokinetic models to promote the development of veterinary drugs with high efficacy and safety

Physiologically based pharmacokinetic (PBPK) models have become important tools for the development of novel human drugs. Food-producing animals and pets comprise an important part of human life, and the development of veterinary drugs (VDs) has greatly impacted human health. Owing to increased affordability of and demand for drug development, VD manufacturing companies should have more PBPK models required to reduce drug production costs. So far, little attention has been paid on applying PBPK models for the development of VDs. This review begins with the development processes of VDs; then summarizes case studies of PBPK models in human or VD development; and analyzes the application, potential, and advantages of PBPK in VD development, including candidate screening, formulation optimization, food effects, target-species safety, and dosing optimization. Then, the challenges of applying the PBPK model to VD development are discussed. Finally, future opportunities of PBPK models in designing dosing regimens for intracellular pathogenic infections and for efficient oral absorption of VDs are further forecasted. This review will be relevant to readers who are interested in using a PBPK model to develop new VDs.

Effect of Liver Cirrhosis on the Pharmacokinetics, Metabolism, and Tolerability of Daridorexant, A Novel Dual Orexin Receptor Antagonist

BACKGROUND AND OBJECTIVE

Daridorexant is a dual orexin receptor antagonist in clinical development for insomnia. As daridorexant is cleared mainly via cytochrome P450 (CYP) 3A4, the effect of hepatic impairment on the pharmacokinetics (PK), metabolism, and tolerability of daridorexant was evaluated. Sleep disorders are common in patients with liver cirrhosis and, therefore, sleep-promoting drugs with a better tolerability than currently available would be preferable, a premise that dual orexin receptor antagonists may fulfill.

METHODS

This was a single-dose, open-label, phase I study. Subjects with mild (Child-Pugh A, N = 8) or moderate (Child-Pugh B, N = 8) liver cirrhosis and matched healthy control subjects (N = 8) received 25 mg of daridorexant orally. Blood samples were collected for 72 h post-dose for PK assessments of daridorexant and three major metabolites.

RESULTS

Compared with healthy subjects, patients showed a decrease in total daridorexant area under the plasma concentration-time curve from zero to infinity (AUC_0-inf) and maximum plasma concentration with a geometric mean ratio (GMR, 90% confidence interval [CI]) of 0.51 (0.28-0.92) and 0.50 (0.35-0.72) in Child-Pugh A and 0.74 (0.39-1.41) and 0.42 (0.29-0.60) in Child-Pugh B patients, respectively. Furthermore, the median time to reach maximum plasma concentration was slightly delayed (1.0 h [90% CI 0.0-2.0] in Child-Pugh A patients and 0.5 h [90% CI 0.0-1.5] in Child-Pugh B patients), while for Child-Pugh B patients, a doubling in half-life was observed (GMR [90% CI]: 2.09 [1.32-3.30]). Considering the high plasma protein binding (> 99%) and a 1.9-fold to 2.3-fold increase in the unbound fraction in patients, the PK of unbound daridorexant was also assessed. Compared with healthy subjects, Child-Pugh B patients had a higher AUC_0-inf (GMR [90% CI] 1.60 [0.93-2.73]), a lower apparent plasma clearance (GMR [90% CI] 0.63 [0.37-1.07]), and the same doubling in the half-life observed for total daridorexant, whereas maximum plasma concentration and apparent volume of distribution were not different. Unbound daridorexant PK in Child-Pugh A patients did not differ from healthy subjects. In addition, the metabolic ratios (parent to metabolite), i.e., a marker of CYP 3A4 activity, of the two most abundant daridorexant metabolites were higher in patients with liver cirrhosis compared with healthy subjects. All treatment-emergent adverse events were transient and of mild or moderate intensity and no other treatment-related effects were apparent.

CONCLUSIONS

No safety issue of concern was detected following administration of 25 mg of daridorexant in the study population. Moderate liver cirrhosis causes impaired hepatic clearance of unbound daridorexant, which prolongs the half-life. A 25-mg dose of daridorexant should, therefore, not be exceeded in Child-Pugh B patients. A dose adjustment is not required in Child-Pugh A patients, while avoidance of daridorexant in patients with Child-Pugh C cirrhosis is recommended.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03713242.

Nonclinical pharmacology of daridorexant: a new dual orexin receptor antagonist for the treatment of insomnia

Dual orexin receptor antagonists (DORAs) represent a novel type of sleep medication that provide an alternative to the traditionally used positive allosteric gamma-aminobutyric acid (GABA)-A receptor modulators. Daridorexant is a new DORA that exhibited in phase 3 trials in insomnia not only a beneficial effect on sleep variables, measured objectively and assessed subjectively, but also an improvement in daytime functioning. Daridorexant was discovered through a tailored research program aimed at identifying an optimized sleep-promoting molecule with pharmacokinetic properties appropriate for covering the whole night while avoiding next-morning residual activity at efficacious doses. By specific binding to both orexin receptors, daridorexant inhibits the actions of the wake-promoting orexin (also called hypocretin) neuropeptides. This mechanism avoids a more widespread inhibition of neuronal pathways and associated side effects that are intrinsic to positive allosteric GABA-A receptor modulators. Here, we review the general pharmacology of daridorexant, based on nonclinical pharmacology studies of daridorexant, unpublished or already described, or based on work with other DORAs. Some unique features of daridorexant will be highlighted, such as the promotion of natural and surmountable sleep, the preservation of memory and cognition, the absence of tolerance development or risk of physical dependence, and how it can benefit daytime functioning.

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).

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.

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.

Structure-based development of a subtype-selective orexin 1 receptor antagonist

Orexins are neuropeptides that activate the rhodopsin-like G protein-coupled receptors OX1R and OX2R. The orexin system plays an important role in the regulation of the sleep-wake cycle and the regulation of feeding and emotions. The nonselective orexin receptor antagonist suvorexant has been the first drug on the market targeting the orexin system and is prescribed for the treatment of insomnia. Subtype-selective OX1R antagonists are valuable tools to further investigate the functions and physiological role of the OX1R in vivo and promising lead compounds for the treatment of drug addiction, anxiety, pain or obesity. Starting from the OX1R and OX2R crystal structures bound to suvorexant, we exploited a single amino acid difference in the orthosteric binding site by using molecular docking and structure-based drug design to optimize ligand interactions with the OX1R while introducing repulsive interactions with the OX2R. A newly established enantiospecific synthesis provided ligands showing up to 75-fold selectivity for the OX1R over the OX2R subtype. The structure of a new OX1R antagonist with subnanomolar affinity (JH112) was determined by crystallography in complex with the OX1R and corresponded closely to the docking-predicted geometry. JH112 exhibits high selectivity over a panel of different GPCRs, is able to cross the blood-brain barrier and acts as slowly diffusing and insurmountable antagonist for G_q protein activation and in particular β-arrestin-2 recruitment at OX1R. This study demonstrates the potential of structure-based drug design to develop more subtype-selective GPCR ligands with potentially reduced side effects and provides an attractive probe molecule and lead compound.

Daridorexant, a new dual orexin receptor antagonist, in elderly subjects with insomnia disorder

Objective

To assess the dose-response of daridorexant, a new dual orexin receptor antagonist, on wake after sleep onset (WASO).

Methods

Elderly (≥65 years) participants (n = 58) with insomnia were randomly allocated (Latin square design) to receive 5 treatments (5, 10, 25, and 50 mg daridorexant and placebo) during 5 treatment periods, each consisting of 2 treatment nights followed by a 5- to 12-day washout period. Main efficacy endpoints were the absolute change from baseline in WASO (primary) and latency to persistent sleep (LPS; secondary) to days 1 and 2 (mean of 2 treatment nights assessed by polysomnography) in each period. Safety and tolerability were also assessed.

Results

Of 58 participants included, 67% were female, and the median age was 69 years (range 65–85 years). WASO and LPS were dose-dependently reduced from baseline to days 1 and 2 after daridorexant administration (multiple comparison procedure modeling, p < 0.0001 and p = 0.004, respectively); reductions were statistically significant for doses ≥10 mg compared with placebo (WASO: −32.0, −45.1, −61.4 minutes; LPS: −44.9, −43.8, −45.4 minutes for 10, 25, and 50 mg, respectively, p ≤ 0.025). Treatment-emergent adverse events were similar for daridorexant and placebo; the most frequent were fatigue, nasopharyngitis, gait disturbance, and headache (≤7% in any group).

Conclusions

Daridorexant was well tolerated. Dose-dependent improvements in WASO and LPS were statistically significant (dose range 10–50 mg) in elderly people with insomnia disorder.

ClinicalTrials.gov identifier:

NCT02841709.

Classification of evidence

This study provides Class I evidence that, for elderly people with insomnia, daridorexant reduced WASO.

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.

Comparison of Orexin 1 and Orexin 2 Ligand Binding Modes Using X-ray Crystallography and Computational Analysis

The orexin system, which consists of the two G protein-coupled receptors OX1 and OX2, activated by the neuropeptides OX-A and OX-B, is firmly established as a key regulator of behavioral arousal, sleep, and wakefulness and has been an area of intense research effort over the past two decades. X-ray structures of the receptors in complex with 10 new antagonist ligands from diverse chemotypes are presented, which complement the existing structural information for the system and highlight the critical importance of lipophilic hotspots and water molecules for these peptidergic GPCR targets. Learnings from the structural information regarding the utility of pharmacophore models and how selectivity between OX1 and OX2 can be achieved are discussed.