Addition of zolpidem to combination therapy with atomoxetine-oxybutynin increases sleep efficiency and the respiratory arousal threshold in obstructive sleep apnoea: A randomized trial

A muscarinic, GIRK channel-mediated inhibition of inspiratory-related XII nerve motor output emerges in early postnatal development in mice

In neonatal rhythmic medullary slices, muscarinic acetylcholine receptor (mAChR) activation of hypoglossal (XII) motoneurons that innervate the tongue has a net excitatory effect on XII inspiratory motor output. Conversely, during rapid eye movement sleep in adult rodents, XII motoneurons experience a loss of excitability partly due to activation of mAChRs. This may be mediated by activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels. Therefore, this study was designed to evaluate whether muscarinic modulation of XII inspiratory motor output in mouse rhythmic medullary slices includes GIRK channel-mediated inhibition and, if so, when this inhibitory mechanism emerges. Local pressure injection of the mAChR agonist muscarine potentiated inspiratory bursting by 150 ± 28% in postnatal day (P)0-P5 rhythmic medullary slice preparations. In the absence of muscarine, pharmacological GIRK channel block by Tertiapin-Q did not affect inspiratory burst parameters, whereas activation with ML297 decreased inspiratory burst area. Blocking GIRK channels by local preapplication of Tertiapin-Q revealed a developmental change in muscarinic modulation of inspiratory bursting. In P0-P2 rhythmic medullary slices, Tertiapin-Q preapplication had no significant effect on muscarinic potentiation of inspiratory bursting (a negligible 6% decrease). However, preapplication of Tertiapin-Q to P3-P5 rhythmic medullary slices caused a 19% increase in muscarinic potentiation of XII inspiratory burst amplitude. Immunofluorescence experiments revealed expression of GIRK 1 and 2 subunits and M1, M2, M3, and M5 mAChRs from P0 to P5. Overall, these data support that mechanisms underlying muscarinic modulation of inspiratory burst activity change postnatally and that potent GIRK-mediated inhibition described in adults emerges early in postnatal life.NEW & NOTEWORTHY Muscarinic modulation of inspiratory bursting at hypoglossal motoneurons has a net excitatory effect in neonatal rhythmic medullary slice preparations and a net inhibitory effect in adult animals. We demonstrate that muscarinic modulation of inspiratory bursting undergoes maturational changes from postnatal days 0 to 5 that include emergence of an inhibitory component mediated by G-protein-coupled inwardly rectifying potassium channels after postnatal day 3 in neonatal mouse rhythmic medullary slice preparations.

Pharmacological management of co-morbid obstructive sleep apnoea and insomnia

INTRODUCTION

Clinical presentation of both insomnia and obstructive sleep apnea (COMISA) is common. Approximately 30% of clinical cohorts with OSA have insomnia symptoms and vice versa. The underlying pathophysiology of COMISA is multifactorial. This poses a complex clinical challenge. Currently, there are no clinical guidelines or recommendations outside of continuous positive airway pressure (CPAP) therapy and cognitive behavioral therapy for insomnia (CBTi). Clinically translatable precision medicine approaches to characterize individual causes or endotypes may help optimize future pharmacological management of COMISA.

AREAS COVERED

This review article provides an up-to-date account of COMISA and its consequences, the underlying pathophysiology of sleep apnea, insomnia and COMISA, current treatment approaches and limitations, pharmacotherapy targets and future priorities.

EXPERT OPINION

There are multiple promising emerging therapies, but clinical trial data specifically in COMISA populations are lacking. This is a priority for future investigation to inform development of evidence-based guidelines. Pharmacotherapies, particularly for insomnia, do not target the underlying causes of the disorder thus, are indicated for short-term use only and should remain second line. Future multidisciplinary research should be directed toward the multifactorial nature of COMISA and the challenges of adapting COMISA treatment in clinical practice and overcoming the practical barriers that health-care providers and consumers encounter.

Relationship between Symptom Profiles and Endotypes among Patients with Obstructive Sleep Apnea: A Latent Class Analysis

Rationale: Obstructive sleep apnea (OSA) is a heterogeneous syndrome with various endotypic traits and symptoms. A link among symptoms, endotypes, and disease prognosis has been proposed but remains unsupported by empirical data. Objectives: To link symptom profiles and endotypes by clustering endotypic traits estimated using polysomnographic signals. Methods: We recruited 509 patients with moderate to severe OSA from a single sleep center. Polysomnographic data were collected between May 2020 and January 2022. Endotypic traits, namely arousal threshold, upper airway collapsibility, loop gain, and upper airway muscle compensation, were retrieved using polysomnographic signals during non-rapid eye movement periods. We used latent class analysis to group participants into endotype clusters. Demographic and polysomnographic parameter differences were compared between clusters, and associations between endotype clusters and symptom profiles were examined using logistic regression analyses. Results: Three endotype clusters were identified, characterized by high collapsibility/loop gain, low arousal threshold, and low compensation, respectively. Patients in each cluster exhibited similar demographic characteristics, but those in the high collapsibility/loop gain cluster had the highest proportion of obesity and severe oxygen desaturation observed in polysomnographic studies. The low compensation cluster was characterized by fewer sleepy symptoms and exhibited a lower rate of diabetes mellitus. Compared with the excessively sleepy group, disturbed sleep symptoms were associated with the low arousal threshold cluster (odds ratio, 1.89; 95% confidence interval, 1.16-3.10). Excessively sleepy symptoms were associated with the high collapsibility/loop gain cluster (odds ratio, 2.16; 95% confidence interval, 1.39-3.37) compared with the minimally symptomatic group. Conclusions: Three pathological endotype clusters were identified among patients with moderate to severe OSA, each exhibiting distinct polysomnographic characteristics and clinical symptom profiles.

Targets for obstructive sleep apnea pharmacotherapy: principles, approaches, and emerging strategies

INTRODUCTION

Obstructive sleep apnea (OSA) is a common and serious breathing disorder. Several pathophysiological factors predispose individuals to OSA. These factors are quantifiable, and modifiable pharmacologically.

AREAS COVERED

Four key pharmacotherapeutic targets are identified and mapped to the major determinants of OSA pathophysiology. PubMed and Clinicaltrials.gov were searched through April 2023.

EXPERT OPINION

Target #1: Pharyngeal Motor Effectors. Increasing pharyngeal muscle activity and responsivity with noradrenergic-antimuscarinic combination is central to recent breakthrough OSA pharmacotherapy. Assumptions, knowledge gaps, future directions, and other targets are identified. #2: Upper Airway Sensory Afferents. There is translational potential of sensitizing and amplifying reflex pharyngeal dilator muscle responses to negative airway pressure via intranasal delivery of new potassium channel blockers. Rationales, advantages, findings, and potential strategies to enhance effectiveness are identified. #3: Chemosensory Afferents and Ventilatory Control. Strategies to manipulate ventilatory control system sensitivity by carbonic anhydrase inhibitors are supported in theory and initial studies. Intranasal delivery of agents to stimulate central respiratory activity are also introduced. #4: Sleep-Wake Mechanisms. Arousability is the fourth therapeutic target rationalized. Evolving automated tools to measure key pathophysiological factors predisposing to OSA will accelerate pharmacotherapy. Although not currently ready for general clinical settings, the identified targets are of future promise.

Pharmacotherapy for obstructive sleep apnea: targeting specific pathophysiological traits

INTRODUCTION

The pathophysiology of obstructive sleep apnea (OSA) is multi-factorial and complex. Varying OSA's pathophysiological traits have been identified, including pharyngeal collapsibility, upper airway muscle reactivity, arousal threshold, and regulation of the ventilatory drive. Being CPAP of difficult tolerance and other interventions reserved to specific subpopulations new pharmacological treatments for OSA might be resolutive.

AREAS COVERED

Several existing and newly developed pharmacological drugs can impact one or more endotypes and could therefore be proposed as treatment options for sleep disordered breathing. With this review we will explore different pathophysiological traits as new targets for OSA therapy. This review will summarize the most promising pharmacological treatment for OSA accordingly with their mechanisms of action on upper airway collapsibility, muscle responsiveness, arousal threshold, and loop gain.

EXPERT OPINION

Only understanding the pathophysiological traits causing OSA in each patient and placing the disease in the framework of patient comorbidities, we will be able to evolve interventions toward OSA. The development of new drug's combinations will permit different approaches and different choices beside conventional treatments. In the next future, we hope that sleep specialists will select the treatment for a specific patient on the base of its pathophysiology, defining a precision medicine for OSA.

The combination of atomoxetine and dronabinol for the treatment of obstructive sleep apnea: a dose-escalating, open-label trial

STUDY OBJECTIVES

The potential sedative effect of dronabinol and the high expression of cannabinoid receptors on the hypoglossal motor nuclei makes this agent a good candidate for obstructive sleep apnea (OSA) pharmacotherapy to be tested with atomoxetine, a noradrenergic reuptake inhibitor that reduced OSA severity in combination with oxybutynin. Here we tested the effect of atomoxetine 80 mg plus dronabinol (Ato-Dro) at 2 different doses (5 and 10 mg) vs. baseline and atomoxetine alone in a 2-center, open-label, dose-escalating trial. The primary outcome was the effect of Ato-Dro vs. baseline on OSA severity (apnea-hypopnea index, hypopneas associated with 4% oxygen desaturation). Safety of the combination and self-reported outcomes were also assessed.

METHODS

Fifteen patients with OSA received progressively increasing Ato-Dro doses (dose escalation was performed every week, starting from Ato-Dro 40-2.5 mg, then 80-5 mg and finally 80-10 mg). A clinical, in-lab polysomnography was performed at baseline, on Ato-Dro 80-5 and Ato-Dro 80-10 mg.

RESULTS

Ato-Dro 80-10 mg did not significantly reduce apnea-hypopnea index, hypopneas associated with 4% oxygen desaturation, and hypoxic burden and yielded limited clinical benefit vs. baseline and atomoxetine alone. However, Ato-Dro 80-5 mg did improve OSA severity (Δapnea-hypopnea index = 8.3[0.3, 16.3] events/h; mean [confidence interval]; Δhypoxic burden = 37.7[12.5, 62.7] %min/h) and multiple self-reported outcomes vs. baseline and/or atomoxetine alone. Ato-Dro administration was characterized by several potentially harmful side effects and treatment discontinuation in 1/3 of cases.

CONCLUSIONS

Ato-Dro 80-5 mg might be useful to reduce OSA severity and lead to self-reported improvement in those who could tolerate the combination. However, given the numerous side effects and the exploratory nature of this open-label study, our results warrant further validation in larger trials.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Title: Study for Efficacy and Dose Escalation of AD313 + Atomoxetine (SEED) (SEED); URL: https://clinicaltrials.gov/ct2/show/NCT05101122; Identifier: NCT05101122.

CITATION

Messineo L, Norman D, Ojile J. The combination of atomoxetine and dronabinol for the treatment of obstructive sleep apnea: a dose-escalating, open-label trial. J Clin Sleep Med. 2023;19(7):1183-1190.

Effects of atomoxetine plus a hypnotic on obstructive sleep apnea severity in patients with a moderately collapsible pharyngeal airway

STUDY OBJECTIVES

Pharmacotherapy for obstructive sleep apnea (OSA) regained consideration after the discovery that atomoxetine and oxybutynin greatly reduced OSA severity. However, atomoxetine and oxybutynin reduced the arousal threshold and may therefore be poorly tolerated in patients with OSA and disturbed sleep. As a result, we tested the combination of atomoxetine plus 2 hypnotics in patients with OSA. The effects of atomoxetine plus: (1) trazodone (Ato-Trazo) and (2) lemborexant vs placebo on apnea-hypopnea index, hypoxic burden, arousal threshold, and total sleep time were assessed. Drug safety was also ascertained, together with the effect of the combinations on other OSA traits, self-reported sleep quality, and next-day alertness.

METHODS

Following a baseline study, 15 patients with mild-to-severe OSA with moderate upper airway collapsibility were administered Ato-Trazo, atomoxetine and lemborexant, and matching placebo according to a double-blind, randomized, crossover design. Apnea-hypopnea index and other objective outcomes were calculated from 3 clinical, in-laboratory polysomnograms.

RESULTS

Ato-Trazo significantly reduced apnea-hypopnea index from a median [interquartile range] of 18.2 [11.8 to 31.3] on placebo to 7.4 [5.4 to 16.1] events/h, P = .024, and hypoxic burden from 46.3 [25.1 to 88.3] on placebo to 18.7 [14.9 to 43.5], P = .003. This effect was likely driven by an increase in polysomnography-estimated pharyngeal muscle activity during the events (P = .029). Atomoxetine and lemborexant had smaller statistically insignificant effects. Contrary to atomoxetine and oxybutynin, Ato-Trazo and atomoxetine and lemborexant did not reduce the arousal threshold. Both combinations had no effect on total sleep time but worsened self-reported sleep quality.

CONCLUSIONS

Ato-Trazo has the potential to become a useful drug combination, however, longer trials are needed to determine the best dosage and the subgroup of patients who may benefit most from this combination.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Crossover Trial of AD182 and AD504 in Obstructive Sleep Apnea; URL: https://clinicaltrials.gov/ct2/show/NCT04645524; Identifier: NCT04645524.

CITATION

Corser B, Eves E, Warren-McCormick J, Rucosky G. Effects of atomoxetine plus a hypnotic on obstructive sleep apnea severity in patients with a moderately collapsible pharyngeal airway. J Clin Sleep Med. 2023;19(6):1035-1042.

Effects of the combination of atomoxetine and oxybutynin in Japanese patients with obstructive sleep apnoea: A randomized controlled crossover trial

BACKGROUND AND OBJECTIVE

The possibility of combination therapy with atomoxetine (ATO) and oxybutynin (OXY) has been suggested for obstructive sleep apnoea (OSA). However, the effectiveness of this treatment remains uninvestigated in Japanese OSA patients. Therefore, we performed a randomized, crossover, phase II, single-centre prospective trial to examine the effects of ATO-OXY therapy in Japanese OSA patients.

METHODS

In total, 17 OSA patients participated in this study. The effects of one night of 80-mg ATO plus 5-mg OXY administration were compared with those of no medication administered before sleep. The primary and secondary outcomes comprised the apnoea-hypopnoea index (AHI) and nadir SpO₂ , SpO₂ drop time and sleep architecture, respectively. The safety endpoints included drug side effects and adverse events.

RESULTS

The values of AHI, nadir SpO₂ , 3% oxygen desaturation index (ODI), 4% ODI, and SpO₂ drop time of <90% did not significantly differ between patients receiving ATO-OXY administration and no medication. Sleep architecture exhibited a significant change: ATO-OXY increased sleep stage N1 (p < 0.0001) and decreased stage N2 (p = 0.03), rapid eye movement (p < 0.0001) and sleep efficiency (p = 0.02). However, the subanalysis demonstrated an obvious decrease in AHI in five responder patients. Total sleep time and basal sleep efficiency tended to be lower in the responders compared with nonresponders (p = 0.065). No patients experienced severe adverse events or side effects.

CONCLUSION

Overall, ATO-OXY therapy does not reduce AHI in Japanese OSA patients, although AHI was decreased in a proportion of patients. Future studies for identifying treatment response group characteristics are warranted.

The norepinephrine reuptake inhibitor reboxetine alone reduces obstructive sleep apnea severity: a double-blind, placebo-controlled, randomized crossover trial

STUDY OBJECTIVES

Recent findings indicate that noradrenergic and muscarinic processes are crucial for pharyngeal muscle control during sleep. However, to date, reductions in obstructive sleep apnea (OSA) severity have only been detected when noradrenergic agents are combined with an antimuscarinic. Accordingly, this study aimed to determine if reboxetine alone and combined with oxybutynin reduces OSA severity. The pathophysiological mechanisms underpinning the effects of these agents were also investigated via endotyping analysis.

METHODS

Sixteen people (6 women) with OSA completed 3 polysomnograms (∼1-week washout) according to a double-blind, placebo-controlled, three-way crossover design across 2 sites. Single doses of 4 mg reboxetine, placebo, or 4 mg reboxetine + 5 mg oxybutynin were administered before sleep (order randomized).

RESULTS

Reboxetine reduced the apnea-hypopnea index (primary outcome) by 5.4 (95% confidence interval -10.4 to -0.3) events/h, P = .03 (-24 ± 27% in men; -0.7 ± 32% in women). Oxybutynin did not cause additional reductions in apnea-hypopnea index. Reboxetine alone reduced the 4% oxygen desaturation index by (mean ± standard deviation) 5.2 ± 7.2 events/h and reboxetine+oxybutynin by 5.1 ± 10.6 events/h vs placebo, P = .02. Nadir oxygen saturation also increased by 7 ± 11% with reboxetine and 5 ± 9% with reboxetine+oxybutynin vs placebo, P = .01. Mechanistically, reboxetine and reboxetine+oxybutynin improved pharyngeal collapsibility and respiratory control (loop gain). Larger reductions in apnea-hypopnea index with reboxetine in men were associated with higher baseline loop gain.

CONCLUSIONS

These findings show the first evidence that reboxetine alone reduces OSA severity. The data provide novel insight into the role of norepinephrine reuptake inhibitors on upper airway stability during sleep and are important to inform future pharmacotherapy development for OSA.

CLINICAL TRIAL REGISTRATION

Registry: Australian New Zealand Clinical Trials Registry; Name: Reboxetine and Combination Therapy with AD128 in Sleep Apnoea Trial: A Double-Blind, 3-Way Cross-Over Study; URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374614&isReview=true; Identifier: ACTRN12620000662965.

CITATION

Altree TJ, Aishah A, Loffler KA, Grunstein RR, Eckert DJ. The norepinephrine reuptake inhibitor reboxetine alone reduces obstructive sleep apnea severity: a double-blind, placebo-controlled, randomized crossover trial. J Clin Sleep Med. 2023;19(1):85-96.

Effect of Pimavanserin on the Respiratory Arousal Threshold from Sleep: A Randomized Trial

Rationale: A low respiratory arousal threshold is a key endotype responsible for obstructive sleep apnea (OSA) pathogenesis. Pimavanserin is an antiserotoninergic capable of suppressing CO2-mediated arousals without affecting the respiratory motor response in animal models, and thus it holds potential for increasing the arousal threshold in OSA and subsequently reducing OSA severity. Objectives: We measured the effect of pimavanserin on arousal threshold (primary outcome), OSA severity, arousal index, and other OSA endotypes (secondary outcomes). Methods: A total of 18 OSA participants were studied in a randomized, double-blind, crossover study. Patients received a single dose of placebo or pimavanserin 34 mg 4 hours before in-lab polysomnography. Airflow was measured with an oronasal mask attached to a pneumotachograph, and ventilatory drive was recorded with an intraesophageal electromyography catheter. Results are presented as mean or median changes (Δ) and 95% confidence intervals (CIs). Results: Pimavanserin did not increase the arousal threshold, nor did it decrease OSA severity or arousal index. It, however, prolonged total sleep time (Δ[confidence interval (CI)], 39.5 [95%CI, -1.2 to 80.1] min). In an exploratory analysis, a subgroup of seven patients who had a 10% or more increase in arousal threshold on pimavanserin exhibited a decrease in AHI4 (hypopneas associated with 4% desaturation) (Δ[CI], 5.6 [95%CI, 3.6-11.1] events/h) and hypoxic burden (Δ[CI], 22.3 [95%CI, 6.6-32.3] %min/h). Conclusions: A single dose of pimavanserin did not have a significant effect on arousal threshold or OSA severity. However, in a post hoc analysis, a subset of patients who exhibited an increase in arousal threshold on pimavanserin showed a small decrease in OSA severity. Thus, if the arousal threshold could be increased with pimavanserin, perhaps with longer dosing to reach higher drug blood concentrations, then the desired effect on OSA severity might be achievable. Clinical trial registered with ClinicalTrials.gov (NCT04538755).

Atomoxetine and fesoterodine combination improves obstructive sleep apnoea severity in patients with milder upper airway collapsibility

BACKGROUND AND OBJECTIVE

The combination of the noradrenergic atomoxetine plus the anti-muscarinic oxybutynin acutely increased genioglossus activity and reduced obstructive sleep apnoea (OSA) severity. However, oxybutynin has shorter half-life than atomoxetine and side effects that might discourage long-term usage. Accordingly, we aimed to test the combination of atomoxetine and fesoterodine (Ato-Feso), a newer anti-muscarinic with extended release formulation, on OSA severity and endotypes.

METHODS

Twelve subjects with OSA underwent a randomized, double-blind, crossover trial comparing one night of atomoxetine plus fesoterodine (80-4 mg) to placebo. Parameters of OSA severity (e.g., apnoea-hypopnoea index [AHI], nadir oxygen desaturation and hypoxic burden) were calculated from two clinical, in-lab polysomnographic studies. OSA endotypes (including collapsibility per VMIN and arousal threshold) were derived from validated algorithms.

RESULTS

Compared to placebo, Ato-Feso did not reduce the AHI (34.2 ± 19.1 vs. 30.1 ± 28.2 events/h, p = 0.493), but reduced the apnoea index (12.9 [28.8] vs. 1.8 [9.1] events/h, median [interquartile range], p = 0.027) and increased nadir desaturation (76.8 [8.0] vs. 82.2 [8.8] %, p = 0.003); a non-significant trend for improved hypoxic burden was observed (52.4 [50.5] vs. 29.7 [78.9] %min/h, p = 0.093). Ato-Feso lowered collapsibility (raised VMIN ; 43.7 [29.8-55.7] vs. 56.8 [43.8-69.8] %VEUPNOEA , mean [CI], p = 0.002), but reduced the arousal threshold (129.3 [120.1-138.6] vs. 116.7 [107.5-126] %VEUPNOEA , p = 0.038). In post hoc analysis, 6/6 patients with milder collapsibility (VMIN  > 43%) exhibited OSA resolution (drop in AHI > 50% and residual AHI < 10 events/h) and improved hypoxaemia.

CONCLUSION

While inefficacious in unselected patients, Ato-Feso administered for one night suppressed OSA in patients with milder collapsibility. Ato-Feso may hold some promise as an alternative OSA treatment in certain subgroups of individuals.

New pharmacologic agents for obstructive sleep apnoea: what do we know and what can we expect?

PURPOSE OF REVIEW

This review provides a condensed description of pharmacological remedies explored in patients with obstructive sleep apnoea (OSA) as well as projections of what we might expect in terms of clinical performance of these drugs.

RECENT FINDINGS

Conventional drug therapies explored in OSA have generally produced disappointing results and there is a shortage of pharmacological treatment alternatives in this disorder. Recent insights into pathophysiological mechanisms potentially involved in OSA suggest that the condition may be divided into distinct subgroups based on clusters or defined by means of unique functional endotypic criteria. In fact, positive outcomes in clinical trials have now resulted in several drug candidates that show a convincing reduction of sleep disordered breathing in both short and intermediate term. Such drugs may be particularly useful in certain variants of OSA but not in others. These insights have also raised the ambition to create personalized therapies in OSA. Another recent development is the insight that OSA-linked conditions such as obesity, daytime somnolence and various forms of cardiovascular/metabolic disease may provide drug-based targets. For instance, pharmacological obesity therapy may provide not only positive metabolic effects but may also be a way to eliminate the anatomic component in obese OSA patients.

SUMMARY

Recent insights into the pathophysiology of OSA have opened possibilities to develop personalized therapy. Drugs addressing fundamental aspects of the sleep and breathing disorder provide a particularly promising avenue for development of novel forms of treatment in OSA.

Differential pharmacological and sex-specific effects of antimuscarinic agents at the hypoglossal motor nucleus in vivo in rats

Successful cholinergic-noradrenergic pharmacotherapy for obstructive sleep apnea (OSA) is thought to be due to effects at the hypoglossal motor nucleus (HMN). Clinical efficacy varies with muscarinic-receptor (MR) subtype affinities. We hypothesized that oxybutynin (cholinergic agent in successful OSA pharmacotherapy) is an effective MR antagonist at the HMN and characterized its efficacy with other antagonists. We recorded tongue muscle activity of isoflurane anesthetized rats (121 males and 60 females, 7–13 per group across 13 protocols) in response to HMN microperfusion with MR antagonists with and without: (i) eserine-induced increased endogenous acetylcholine at the HMN and (ii) muscarine. Eserine-induced increased acetylcholine decreased tongue motor activity (p < 0.001) with lesser cholinergic suppression in females versus males (p = 0.017). Motor suppression was significantly attenuated by the MR antagonists atropine, oxybutynin, and omadacycline (MR2 antagonist), each p < 0.001, with similar residual activity between agents (p ≥ 0.089) suggesting similar efficacy at the HMN. Sex differences remained with atropine and oxybutynin (p < 0.001 to 0.05) but not omadacycline (p = 0.722). Muscarine at the HMN also decreased motor activity (p < 0.001) but this was not sex-specific (p = 0.849). These findings have translational relevance to antimuscarinic agents in OSA pharmacotherapy and understanding potential sex differences in HMN suppression with increased endogenous acetylcholine related to sparing nicotinic excitation.

Turning Over a New Leaf-Pharmacologic Therapy in Obstructive Sleep Apnea

Despite extensive research, there is currently no approved drug for obstructive sleep apnea (OSA) treatment. OSA is a heterogeneous condition that involves multiple dominating pathophysiological traits. Drug development in this field needs to address both pathophysiological mechanisms and associated comorbid conditions in order to meet requirements for long-term therapy in OSA. Several drug candidates have been proposed and ongoing phase II trials that target various forms of sleep-disordered breathing have been initiated. The field is moving toward tailored therapeutic approaches in patients with OSA.

Obstructive sleep apnea: personalizing CPAP alternative therapies to individual physiology

Introduction The recent continuous positive airway pressure (CPAP) crisis has highlighted the need for alternative obstructive sleep apnea (OSA) therapies. This article serves to review OSA pathophysiology and how sleep apnea mechanisms may be utilized to individualize alternative treatment options.Areas covered: The research highlighted below focuses on 1) mechanisms of OSA pathogenesis and 2) CPAP alternative therapies based on mechanism of disease. We reviewed PubMed from inception to July 2022 for relevant articles pertaining to OSA pathogenesis, sleep apnea surgery, as well as sleep apnea alternative therapies.Expert opinion: Although the field of individualized OSA treatment is still in its infancy, much has been learned about OSA traits and how they may be targeted based on a patient's physiology and preferences. While CPAP remains the gold-standard for OSA management, several novel alternatives are emerging. CPAP is a universal treatment approach for all severities of OSA. We believe that a personalized approach to OSA treatment beyond CPAP lies ahead. Additional research is needed with respect to implementation and combination of therapies longitudinally, but we are enthusiastic about the future of OSA treatment based on the data presented here.

Current and Novel Treatment Options for OSA

Obstructive sleep apnoea is a challenging medical problem due to its prevalence, its impact on quality of life and performance in school and professionally, the implications for risk of accidents, and comorbidities and mortality. Current research has carved out a broad spectrum of clinical phenotypes and defined major pathophysiological components. These findings point to the concept of personalised therapy, oriented on both the distinct clinical presentation and the most relevant pathophysiology in the individual patient. This leads to questions of whether sufficient therapeutic options other than positive airway pressure (PAP) alone are available, for which patients they may be useful, if there are specific indications for single or combined treatment, and whether there is solid scientific evidence for recommendations. This review describes our knowledge on PAP and non-PAP therapies to address upper airway collapsibility, muscle responsiveness, arousability and respiratory drive. The spectrum is broad and heterogeneous, including technical and pharmaceutical options already in clinical use or at an advanced experimental stage. Although there is an obvious need for more research on single or combined therapies, the available data demonstrate the variety of effective options, which should replace the unidirectional focus on PAP therapy.

The analysis of individual pathophysiological composition opens new directions towards personalised treatment of OSA, focusing not only on pharyngeal dilation, but also on technical or pharmaceutical interventions on muscle function or breathing regulationhttps://bit.ly/3sayhkd

Comprehensive Analysis of N6-Methyladenosine Regulators in the Subcluster Classification and Drug Candidates Prediction of Severe Obstructive Sleep Apnea

Background: Obstructive sleep apnea (OSA) is the most common type of sleep apnea that impacts the development or progression of many other disorders. Abnormal expression of N6-methyladenosine (m6A) RNA modification regulators have been found relating to a variety of human diseases. However, it is not yet known if m6A regulators are involved in the occurrence and development of OSA. Herein, we aim to explore the impact of m6A modification in severe OSA.

Methods: We detected the differentially expressed m6A regulators in severe OSA microarray dataset GSE135917. The least absolute shrinkage and selection operator (LASSO) and support vector machines (SVM) were used to identify the severe OSA-related m6A regulators. Receiver operating characteristic (ROC) curves were performed to screen and verify the diagnostic markers. Consensus clustering algorithm was used to identify m6A patterns. And then, we explored the character of immune microenvironment, molecular functionals, protein-protein interaction networks and miRNA-TF coregulatory networks for each subcluster. Finally, the Connectivity Map (CMap) tools were used to tailor customized treatment strategies for different severe OSA subclusters. An independent dataset GSE38792 was used for validation.

Results: We found that HNRNPA2B1, KIAA1429, ALKBH5, YTHDF2, FMR1, IGF2BP1 and IGF2BP3 were dysregulated in severe OSA patients. Among them, IGF2BP3 has a high diagnostic value in both independent datasets. Furthermore, severe OSA patients can be accurately classified into three m6A patterns (subcluster1, subcluster2, subcluster3). The immune response in subcluster3 was more active because it has high M0 Macrophages and M2 Macrophages infiltration and up-regulated human leukocyte antigens (HLAs) expression. Functional analysis showed that representative genes for each subcluster in severe OSA were assigned to histone methyltransferase, ATP synthesis coupled electron transport, virus replication, RNA catabolic, multiple neurodegeneration diseases pathway, et al. Moreover, our finding demonstrated cyclooxygenase inhibitors, several of adrenergic receptor antagonists and histamine receptor antagonists might have a therapeutic effect on severe OSA.

Conclusion: Our study presents an overview of the expression pattern and crucial role of m6A regulators in severe OSA, which may provide critical insights for future research and help guide appropriate prevention and treatment options.

Efficacy of atomoxetine plus oxybutynin in the treatment of obstructive sleep apnea with moderate pharyngeal collapsibility

Purpose

Preliminary studies have shown a significant decrease in severity of obstructive sleep apnea (OSA) with the use of a combination of atomoxetine and oxybutynin, with patients having moderate pharyngeal collapsibility during sleep more likely to respond. This study evaluated the efficacy and safety of AD036 (atomoxetine 80 mg and oxybutynin 5 mg) in the treatment of OSA.

Methods

This trial was a phase 2, randomized, placebo-controlled crossover study comparing AD036, atomoxetine 80 mg alone, and placebo during three home sleep studies, each separated by about 1 week. The trial included patients with OSA and moderate pharyngeal collapsibility as defined by a higher proportion of hypopneas to apneas and mild oxygen desaturation.

Results

Of 62 patients who were randomized, 60 were included in efficacy analyses. The apnea–hypopnea index (AHI) from a median (interquartile range) of 14.2 (5.4 to 22.3) events/h on placebo to 6.2 (2.8 to 13.6) with AD036 and 4.8 (1.4 to 11.6) with atomoxetine alone (p < .0001). Both drugs also decreased the oxygen desaturation index (ODI) and the hypoxic burden (p < .0001). AD036, but not atomoxetine alone, reduced the respiratory arousal index and improved ventilation at the respiratory arousal threshold (greater V_active). There was a trend for total sleep time to be decreased more with atomoxetine alone than with AD036. The most common adverse event was insomnia (12% with AD036, 18% with atomoxetine).

Conclusion

AD036 significantly improved OSA severity in patients with moderate pharyngeal collapsibility. Atomoxetine may account for the majority of improvement in OSA severity, while the addition of oxybutynin may mitigate the disruptive effect of atomoxetine on sleep and further improve ventilation.

Trial registration

Clinical trial registered with www.clinicaltrials.gov (NCT04445688).

The Combination of Betahistine and Oxybutynin Increases Respiratory Control Sensitivity (Loop Gain) in People with Obstructive Sleep Apnea: A Randomized, Placebo-Controlled Trial

RATIONALE

There are widespread histaminergic projections throughout the brain, including hypoglossal nuclei, that modulate pharyngeal muscle tone and respiratory control. Hence, histaminergic stimulation pharmacologically may increase pharyngeal muscle tone and stabilize respiratory control (loop gain) to reduce obstructive sleep apnea (OSA) severity. Antimuscarinics also increase REM pharyngeal muscle tone in rats. Thus, a combination of histaminergic and anti-muscarinic drugs may be a novel target for OSA pharmacotherapy. However, this has not been investigated. Accordingly, we aimed to test the effects of betahistine (Beta), an H3-autoreceptor antagonist which thereby increases histamine levels, in combination with the antimuscarinic oxybutynin (Oxy), on OSA severity, OSA endotypes, polysomnography parameters and next-day sleepiness and alertness.

METHODS

Thirteen adults with OSA received either Beta-Oxy (96-5mg) or placebo according to a randomized, crossover, double-blind design, prior to polysomnography. Participants completed the Karolinska Sleep Scale and Leeds Sleep Evaluation Questionnaire and a driving simulation task to quantify next-day sleepiness and alertness. OSA endotypes were estimated through validated algorithms using polysomnography.

RESULTS

Compared to placebo, Beta-Oxy increased respiratory control sensitivity (loop gain) (0.52[0.24] vs 0.60[0.34], median [IQR], P = 0.021) without systematically changing OSA severity (34.4±17.2 vs 40.3±27.3 events/h, mean±SD, P = 0.124), sleep efficiency, arousal index or markers of hypoxemia. Beta-Oxy was well tolerated and did not worsen next-day sleepiness/alertness.

CONCLUSION

Rather than stabilize breathing during sleep, Beta-Oxy increases loop gain, which is likely to be deleterious for most people with OSA. However, in certain conditions characterized by blunted respiratory control (eg, obesity hypoventilation syndrome), interventions to increase loop gain may be beneficial.