Psychomotor effects, pharmacokinetics and safety of the orexin receptor antagonist suvorexant administered in combination with alcohol in healthy subjects

Orexin-mediated motivated arousal and reward seeking

The neuromodulator orexin has been identified as a key factor for motivated arousal including recent evidence that sleep deprivation-induced enhancement of reward behavior is modulated by orexin. While orexin is not necessary for either reward or arousal behavior, orexin neurons' broad projections, ability to sense the internal state of the animal, and high plasticity of signaling in response to natural rewards and drugs of abuse may underlie heightened drug seeking, particularly in a subset of highly motivated reward seekers. As such, orexin receptor antagonists have gained deserved attention for putative use in addiction treatments. Ongoing and future clinical trials are expected to identify individuals most likely to benefit from orexin receptor antagonist treatment to promote abstinence, such as those with concurrent sleep disorders or high craving, while attention to methodological considerations will aid interpretation of the numerous preclinical studies investigating disparate aspects of the role of orexin in reward and arousal.

Emerging drugs in phase II and III clinical development for the treatment of alcohol use disorder

INTRODUCTION

Alcohol Use Disorder (AUD) poses an ongoing significant global health burden. AUD is highly prevalent and affects not only the individuals with AUD, but also their communities and society at large. Even though pharmacotherapy is an integral part of AUD treatment, the few available substances show limited efficacy and limited clinical impact. Thus, there is a need for new innovative pharmacotherapeutic approaches.

AREAS COVERED

This paper provides a comprehensive review of drugs approved for the treatment of AUD as well as those currently in phase II and III development. Data from recent clinical trials has been reviewed and supplemented by additional literature based on a systematic search of the PubMed database and clinical trials registries. Compounds discussed include disulfiram, naltrexone, nalmefene, acamprosat, baclofen, sodium oxybate, doxazosin, varenicline, zonisamide, gabapentin, apremilast, ibudilast, ivermectin, tolcapone, mifepristone, suvorexant, ketamine, psilocybin, semaglutide, oxytocin and cannabidiol.

EXPERT OPINION

Even though the majority of the discussed compounds lack sufficient evidence to support their efficacy, multiple promising new treatment options are currently under investigation. Future research has to consider specific phenotypes and subgroups of AUD as well as a possible enhancement of the effects of psychotherapy through combination with pharmacotherapy. Practitioners should be encouraged to use available compounds to support existing therapeutic regimens.

Clinical usefulness of dual orexin receptor antagonism beyond insomnia: Neurological and psychiatric comorbidities

Orexin is a neurotransmitter produced by a small group of hypothalamic neurons. Besides its well-known role in the regulation of the sleep-wake cycle, the orexin system was shown to be relevant in several physiological functions including cognition, mood and emotion modulation, and energy homeostasis. Indeed, the implication of orexin neurotransmission in neurological and psychiatric diseases has been hypothesized via a direct effect exerted by the projections of orexin neurons to several brain areas, and via an indirect effect through orexin-mediated modulation of sleep and wake. Along with the growing evidence concerning the use of dual orexin receptor antagonists (DORAs) in the treatment of insomnia, studies assessing their efficacy in insomnia comorbid with psychiatric and neurological diseases have been set in order to investigate the potential impact of DORAs on both sleep-related symptoms and disease-specific manifestations. This narrative review aimed at summarizing the current evidence on the use of DORAs in neurological and psychiatric conditions comorbid with insomnia, also discussing the possible implication of modulating the orexin system for improving the burden of symptoms and the pathological mechanisms of these disorders. Target searches were performed on PubMed/MEDLINE and Scopus databases and ongoing studies registered on Clinicaltrials.gov were reviewed. Despite some contradictory findings, preclinical studies seemingly support the possible beneficial role of orexin antagonism in the management of the most common neurological and psychiatric diseases with sleep-related comorbidities. However, clinical research is still limited and further studies are needed for corroborating these promising preliminary results.

Alternative use of suvorexant (Belsomra®) for the prevention of alcohol drinking and seeking in rats with a history of alcohol dependence

Alcohol use disorder (AUD) is one of the most treatment-resistant medical conditions globally. The orexin (Orx) system regulates diverse physiological processes, including stress, and is a system of interest for the development of pharmaceuticals to treat substance use disorders, particularly AUD. The present study tested the ability of the dual orexin receptor antagonist suvorexant (SUV), marketed by Merck as Belsomra®, for the treatment of insomnia, to decrease alcohol self-administration and the stress-induced reinstatement of alcohol-seeking behavior in male Wistar rats with a history of alcohol dependence. Rats were trained to orally self-administer 10% alcohol (30 min/day for 3 weeks) and were either made dependent via chronic intermittent alcohol vapor exposure (14 h ON, 10 h OFF) for 6 weeks or exposed to air (non-dependent). Starting on week 7, the effect of SUV (0-20 mg/kg, p.o.) was tested on alcohol self-administration at acute abstinence (8 h after vapor was turned OFF) twice weekly. A separate cohort of rats that were prepared in parallel was removed from alcohol vapor exposure and then subjected to extinction training for 14 sessions. Once extinction was achieved, the rats received SUV (0 and 5 mg/kg, p.o.) and were tested for the footshock stress-induced reinstatement of alcohol-seeking behavior. Suvorexant at 5, 10, and 20 mg/kg selectively decreased alcohol intake in dependent rats. Furthermore, 5 mg/kg SUV prevented the stress-induced reinstatement of alcohol-seeking behavior in dependent rats only. These results underscore the significance of targeting the Orx system for the treatment of substance use disorders generally and suggest that repurposing SUV could be an alternative approach for the treatment of AUD.

Effect of alcohol coadministration on the pharmacodynamics, pharmacokinetics, and safety of lemborexant: A randomized, placebo-controlled crossover study

BACKGROUND

Lemborexant is a dual orexin receptor antagonist approved to treat insomnia in adults in several countries including the USA, Canada, and Japan.

AIMS

This study was conducted to investigate effects of lemborexant and alcohol coadministration on postural stability, cognitive performance, and the pharmacokinetics, safety, and tolerability of lemborexant.

METHODS

This was a Phase 1, double-blind, placebo-controlled, four-period crossover study in 32 healthy adults. Individuals were randomized into one of four treatment sequences to receive single doses of placebo, lemborexant 10 mg (LEM10), alcohol (males, 0.7 g/kg; females, 0.6 g/kg), and LEM10 plus alcohol, each separated by a 14-day washout. Postural stability (body sway) was measured by ataxiameter and a cognitive performance assessment battery evaluated four domains of attention and memory.

RESULTS

Pharmacodynamic outcomes were analyzed for the 18 participants who completed all four treatments. Change from baseline in body sway showed no significant differences between lemborexant plus alcohol versus alcohol alone. Compared with alcohol alone, coadministration of lemborexant with alcohol showed additive negative effects on cognitive performance domains, corresponding approximately with peak plasma lemborexant concentrations (median = 1.5 h). Cognitive performance was also impaired with lemborexant alone at 0.5 and 2 h in this experimental paradigm with morning dosing. Alcohol increased plasma lemborexant exposure by 70% based on area under the curve to 72 h, and increased peak plasma lemborexant concentrations by 35%. The most commonly reported treatment-emergent adverse event was somnolence.

CONCLUSION

Coadministration of lemborexant with alcohol showed additive negative effects on cognitive measures, but not on postural stability, compared with alcohol alone. Lemborexant exposure was increased with alcohol. Lemborexant alone or with alcohol was well tolerated. Patients are advised not to consume alcohol with lemborexant.

Novel Agents for the Pharmacological Treatment of Alcohol Use Disorder

Alcohol use disorder (AUD) is a highly prevalent but severely under-treated disorder, with only three widely-approved pharmacotherapies. Given that AUD is a very heterogeneous disorder, it is unlikely that one single medication will be effective for all individuals with an AUD. As such, there is a need to develop new, more effective, and diverse pharmacological treatment options for AUD with the hopes of increasing utilization and improving care. In this qualitative literature review, we discuss the efficacy, mechanism of action, and tolerability of approved, repurposed, and novel pharmacotherapies for the treatment of AUD with a clinical perspective. Pharmacotherapies discussed include: disulfiram, acamprosate, naltrexone, nalmefene, topiramate, gabapentin, varenicline, baclofen, sodium oxybate, aripiprazole, ondansetron, mifepristone, ibudilast, suvorexant, prazosin, doxazosin, N-acetylcysteine, GET73, ASP8062, ABT-436, PF-5190457, and cannabidiol. Overall, many repurposed and novel agents discussed in this review demonstrate clinical effectiveness and promise for the future of AUD treatment. Importantly, these medications also offer potential improvements towards the advancement of precision medicine and personalized treatment for the heterogeneous AUD population. However, there remains a great need to improve access to treatment, increase the menu of approved pharmacological treatments, and de-stigmatize and increase treatment-seeking for AUD.

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 orexin (hypocretin) neuropeptide system is a target for novel therapeutics to treat cocaine use disorder with alcohol coabuse

An estimated 50-90% of individuals with cocaine use disorder (CUD) also report using alcohol. Cocaine users report coabusing alcohol to 'self-medicate' against the negative emotional side effects of the cocaine 'crash', including the onset of anxiety. Thus, pharmaceutical strategies to treat CUD would ideally reduce the motivational properties of cocaine, alcohol, and their combination, as well as reduce the onset of anxiety during drug withdrawal. The hypothalamic orexin (hypocretin) neuropeptide system offers a promising target, as orexin neurons are critically involved in activating behavioral and physiological states to respond to both positive and negative motivators. Here, we seek to describe studies demonstrating efficacy of orexin receptor antagonists in reducing cocaine, alcohol- and stress-related behaviors, but note that these studies have largely focused on each of these phenomena in isolation. For orexin-based compounds to be viable in the clinical setting, we argue that it is imperative that their efficacy be tested in animal models that account for polysubstance use patterns. To begin to examine this, we present new data showing that rats' preferred level of cocaine intake is significantly increased following chronic homecage access to alcohol. We also report that cocaine intake and motivation are reduced by a selective orexin-1 receptor antagonist when rats have a history of cocaine + alcohol, but not a limited history of cocaine alone. In light of these proof-of-principle data, we outline what we believe to be the key priorities going forward with respect to further examining the orexin system in models of polysubstance use. This article is part of the special issue on Neurocircuitry Modulating Drug and Alcohol Abuse.

Hypnotics with novel modes of action

Insomnia and, more generally, lack of sleep are on the rise. Traditionally treated by classical hypnotics, such as benzodiazepines and Z drugs, which both act on the GABAA receptor, and other modalities, including nondrug therapies, such as cognitive behavioural therapy, there is a range of new hypnotics which are being developed or have recently received market approval. Suvorexant and the like target the orexin/hypocretin system: they should have less side effects in terms of drug-drug interactions with e.g. alcohol, less memory impairment and dependence potential compared to classical hypnotics.

Orexin OX2 Receptor Antagonists as Sleep Aids

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

Novel class of medications, orexin receptor antagonists, in the treatment of insomnia - critical appraisal of suvorexant

Insomnia, a highly prevalent disorder, can be detrimental to patients' overall health and worsen existing comorbidities. Patients may have acute episodes of insomnia related to a traumatic event, but more commonly insomnia occurs chronically. While proper sleep hygiene and behavioral therapy play important roles in the nonpharmacologic management of short-term and chronic insomnia, medications may also be required. Historically, insomnia has been treated with agents such as benzodiazepines, nonbenzodiazepine receptor agonists, and melatonin agonists. Dual orexin receptor antagonists represent a new class of medications for the treatment of insomnia, which block the binding of wakefulness-promoting neuropeptides orexin A and orexin B to their respective receptor sites. Suvorexant (Belsomra) is the first dual orexin receptor antagonist to be approved in the US and Japan and has demonstrated efficacy in decreasing time to sleep onset and increasing total sleep time. Its unique mechanism of action, data to support efficacy and safety over 12 months of use, and relative lack of withdrawal effects when discontinued may represent an alternative for patients with chronic insomnia who cannot tolerate or do not receive benefit from more traditional sleep agents. Suvorexant is effective and well tolerated, but precautions exist for certain patient populations, including females, obese patients, and those with respiratory disease. Suvorexant has only been studied vs placebo, and hence it is unknown how it directly compares with other medications approved by the US Food and Drug Administration for insomnia. Suvorexant is not likely to replace benzodiazepines or nonbenzodiazepine receptor antagonists as a first-line sleep agent but does represent a novel option for the treatment of patients with chronic insomnia.