Effects of the orexin receptor 2 agonist danavorexton on emergence from general anaesthesia and opioid-induced sedation, respiratory depression, and analgesia in rats and monkeys

TAK-925 (Danavorexton), an Orexin Receptor 2 Agonist, Reduces Opioid-induced Respiratory Depression and Sedation without Affecting Analgesia in Healthy Men

BACKGROUND

Orexin neuropeptides help regulate sleep/wake states, respiration, and pain. However, their potential role in regulating breathing, particularly in perioperative settings, is not well understood. TAK-925 (danavorexton), a novel orexin receptor 2-selective agonist, directly activates neurons associated with respiratory control in the brain and improves respiratory parameters in rodents undergoing fentanyl-induced sedation. This study assessed the safety and effect of danavorexton on ventilation in healthy men in an established remifentanil-induced respiratory depression model.

METHODS

This single-center, double-blind, placebo-controlled, two-way crossover, phase 1 trial randomized (1:1) 13 healthy men to danavorexton (11 mg [low-dose], then 19 mg [high-dose]) or placebo, under remifentanil infusion, on two occasions separated by a 36-h or longer washout period. Remifentanil infusion was titrated under isohypercapnic conditions to achieve an approximately 30 to 40% decrease in minute ventilation (from approximately 20 to approximately 14 l/min) before danavorexton/placebo administration. Assessments included safety, ventilation measurements, sedation, and pain tolerance.

RESULTS

A total of four (30.8%) danavorexton-treated participants and one (8.3%) placebo-treated participant experienced treatment-emergent adverse events (all mild in severity). Insomnia, lasting 1 day, occurred in one participant, and was considered related to danavorexton. Compared with placebo, low- and high-dose danavorexton significantly increased ventilation variables (observed mean [95% CI] change, sensitivity analysis model-based P values) including minute volume (8.2 [95% CI, 5.0 to 11.4] and 13.0 [95% CI, 9.4 to 16.5] l/min), tidal volume (312 [95% CI, 180 to 443] and 483 [95% CI, 309 to 657] ml), and respiratory rate (3.8 [95% CI, 1.9 to 5.7] and 5.2 [95% CI, 2.7 to 7.7] breaths/min; all P < 0.001). High-dose danavorexton significantly decreased sedation on a visual analog scale (-29.7 [95% CI, -54.1 to -5.3] mm; P < 0.001) and the Richmond Agitation Sedation Scale (0.4 [95% CI, 0.0 to 0.7]; P < 0.001) compared with placebo. Improvements in respiratory variables continued beyond completion of danavorexton infusion. No significant differences in pain tolerance were observed between danavorexton doses or between danavorexton and placebo (approximately 13% increase from baseline; low dose, P = 0.491; high dose, P = 0.140).

CONCLUSIONS

Danavorexton has effects on respiration and wakefulness in an opioid-induced respiratory depression setting without reversing opioid analgesia.

Integrating Drug Target Information in Deep Learning Models to Predict the Risk of Adverse Events in Patients with Comorbid Post-Traumatic Stress Disorder and Alcohol Use Disorder

Background/Objectives: Comorbid post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) patients are at a significantly higher risk of adverse outcomes, including opioid use disorder, depression, suicidal behaviors, and death, yet limited treatment options exist for this population. This study aimed to build on previous research by incorporating drug target information into a novel deep learning model, T-DeepBiomarker, to predict adverse outcomes and identify potential therapeutic medications. Methods: We utilized electronic medical record (EMR) data from the University of Pittsburgh Medical Center (UPMC), analyzing 5565 PTSD + AUD patients. T-DeepBiomarker was developed by integrating multimodal data, including lab results, drug target information, comorbidities, neighborhood-level social determinants of health (SDoH), and individual-level SDoH (e.g., psychotherapy and veteran status). The model was trained to predict adverse events, including opioid use disorder, suicidal behaviors, depression, and death, within three months following any clinical encounter. Candidate medications targeting significant proteins were identified through literature reviews. Results: T-DeepBiomarker achieved high predictive performance with an AUROC of 0.94 for adverse outcomes in PTSD + AUD patients. Several medications, including OnabotulinumtoxinA, Dronabinol, Acamprosate, Celecoxib, Exenatide, Melatonin, and Semaglutide, were identified as potentially reducing the risk of adverse events by targeting significant proteins. Conclusions: T-DeepBiomarker demonstrates high accuracy in predicting adverse outcomes in PTSD + AUD patients and highlights candidate drugs with potential therapeutic effects. These findings advance pharmacotherapy for this high-risk population and identify medications that warrant further investigation.

Orexinergic projections to substantia innominata mediate arousal and analgesia

Understanding neural circuits involved in anesthesia is crucial for improving its safety and efficacy. Hypothalamic orexin neurons (LHA OX ), projecting broadly, are essential in regulating arousal and pain. However, the precise targets remain unclear. Here we investigated the orexin projections to the substantia innominata (SI). Combining optogenetics, fiber photometry, and EEG/EMG allowed us to manipulate orexin activities, while simultaneously recording local ligand release and global cortical activities during anesthesia. Brain slice electrophysiology revealed the synaptic connections in the SI, while RNAscope was employed to examine the distribution of orexin receptors and downstream neuronal types. Presynaptic vesicles were identified in the orexin terminals in the SI, where 49.16% of cells expressed OX2R and 6.8% expressed OX1R. Orexin release in the SI was reversibly suppressed by isoflurane. Optogenetic activation of the LHA OX →SI circuit significantly increased orexin release and promoted arousal from various anesthesia stages, including reanimation during 0.75% isoflurane (p < 0.0001), prolongation of 3% isoflurane induction (p = 0.0033), and acceleration of emergence from 2% isoflurane (p < 0.0001). Furthermore, activating this circuit induced analgesia to both thermal (p = 0.0074) and inflammatory (p = 0.0127) pain. Patch-clamp recordings revealed that optogenetic activation of orexin terminals in the SI elicited excitatory postsynaptic currents, which were blocked by the OX2R antagonist. SI contains more GABAergic (28.17%) and glutamatergic (11.96%) neurons than cholinergic neurons (4.13%), all of which expressed OX2R. Thus, LHA OX neurons innervate SI neurons to regulate both arousal and pain predominantly through OX2R.

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.

Restoring consciousness with pharmacologic therapy: Mechanisms, targets, and future directions

Severe brain injury impairs consciousness by disrupting a broad spectrum of neurotransmitter systems. Emerging evidence suggests that pharmacologic modulation of specific neurotransmitter systems, such as dopamine, promotes recovery of consciousness. Clinical guidelines now endorse the use of amantadine in individuals with traumatic disorders of consciousness (DoC) based on level 1 evidence, and multiple neurostimulants are used off-label in clinical practice, including methylphenidate, modafinil, bromocriptine, levodopa, and zolpidem. However, the relative contributions of monoaminergic, glutamatergic, cholinergic, GABAergic, and orexinergic neurotransmitter systems to recovery of consciousness after severe brain injury are unknown, and personalized approaches to targeted therapy have yet to be developed. This review summarizes the state-of-the-science in the neurochemistry and neurobiology of neurotransmitter systems involved in conscious behaviors, followed by a discussion of how pharmacologic therapies may be used to modulate these neurotransmitter systems and promote recovery of consciousness. We consider pharmacologic modulation of consciousness at the synapse, circuit, and network levels, with a focus on the mesocircuit model that has been proposed to explain the consciousness-promoting effects of various monoaminergic, glutamatergic, and paradoxically, GABAergic therapies. Though fundamental questions remain about neurotransmitter mechanisms, target engagement and optimal therapy selection for individual patients, we propose that pharmacologic therapies hold great promise to promote recovery and improve quality of life for patients with severe brain injuries.

Orexin receptor 2 agonist activates diaphragm and genioglossus muscle through stimulating inspiratory neurons in the pre-Bötzinger complex, and phrenic and hypoglossal motoneurons in rodents

Orexin-mediated stimulation of orexin receptors 1/2 (OX[1/2]R) may stimulate the diaphragm and genioglossus muscle via activation of inspiratory neurons in the pre-Bötzinger complex, which are critical for the generation of inspiratory rhythm, and phrenic and hypoglossal motoneurons. Herein, we assessed the effects of OX2R-selective agonists TAK-925 (danavorexton) and OX-201 on respiratory function. In in vitro electrophysiologic analyses using rat medullary slices, danavorexton and OX-201 showed tendency and significant effect, respectively, in increasing the frequency of inspiratory synaptic currents of inspiratory neurons in the pre-Bötzinger complex. In rat medullary slices, both danavorexton and OX-201 significantly increased the frequency of inspiratory synaptic currents of hypoglossal motoneurons. Danavorexton and OX-201 also showed significant effect and tendency, respectively, in increasing the frequency of burst activity recorded from the cervical (C3-C5) ventral root, which contains axons of phrenic motoneurons, in in vitro electrophysiologic analyses from rat isolated brainstem-spinal cord preparations. Electromyogram recordings revealed that intravenous administration of OX-201 increased burst frequency of the diaphragm and burst amplitude of the genioglossus muscle in isoflurane- and urethane-anesthetized rats, respectively. In whole-body plethysmography analyses, oral administration of OX-201 increased respiratory activity in free-moving mice. Overall, these results suggest that OX2R-selective agonists enhance respiratory function via activation of the diaphragm and genioglossus muscle through stimulation of inspiratory neurons in the pre-Bötzinger complex, and phrenic and hypoglossal motoneurons. OX2R-selective agonists could be promising drugs for various conditions with respiratory dysfunction.

Danavorexton (TAK-925): an orexin receptor 2 agonist as a new 'arousal' agent

A preclinical study in animals has further characterised a new 'arousal' agent. Danavorexton (TAK-925) is an agonist for orexin receptor 2 where it promotes recovery from inhalational and i.v. anaesthesia and opioid sedation. Although danavorexton reverses opioid sedation, it does not compromise analgesia. This could be a useful addition to the postoperative drug cupboard.