Nearly every emerging obstructive sleep apnea (OSA) treatment now in development works by either mechanically propping the airway open, like CPAP, or altering muscle tone through drugs that act on the central nervous system, like the oral pill AD109 moving through FDA review. Mosanna Therapeutics announced results on September 29, 2026, from a Phase 1 trial of a drug that takes a different route entirely: a nightly nasal spray aimed at restoring a reflex the airway already has, but loses during sleep.
What the Trial Found
The Phase 1 MOSAIC study was a randomized, double-blind, placebo-controlled trial with a combined single-ascending-dose and multiple-ascending-dose design, enrolling 32 healthy adult volunteers across four sequential dose cohorts. According to the company, MOS118 was safe and well tolerated at every dose tested, with no serious adverse events reported. Mosanna says the results support moving the drug into a next-stage trial that will test seven consecutive nights of dosing in people who actually have OSA, rather than healthy volunteers.
Because this was a Phase 1 safety and tolerability study in healthy participants, it does not yet show whether MOS118 reduces apnea events or improves oxygen levels in patients — that evidence will have to come from the OSA-patient trial Mosanna says is next.
How It's Supposed to Work
MOS118 targets a specific physiological mechanism: pressure-sensing nerve endings in the nasal and upper airway that normally detect the negative pressure created during inhalation and signal the upper-airway dilator muscles to tighten and keep the passage open. In people with OSA, this protective reflex becomes less responsive during sleep, letting the airway collapse repeatedly through the night. Rather than bypassing that reflex with mechanical pressure or acting broadly on muscle tone, MOS118 is designed to sensitize those nerve endings so the airway's own defense system reactivates on its own.
That mechanism sets it apart from the current wave of OSA drug candidates. AD109, furthest along in FDA review among oral options, combines a norepinephrine reuptake inhibitor with an antimuscarinic to increase upper-airway muscle activity systemically. GLP-1 drugs like tirzepatide reduce apnea severity indirectly, through weight loss. MOS118 is instead a locally acting nasal spray intended to work directly at the site of airway collapse, which the company argues could mean a more targeted side-effect profile than drugs that act throughout the body.
Why a Local, Reflex-Based Approach Could Matter
CPAP remains the gold-standard OSA treatment, but long-term adherence is a persistent problem — some studies have found roughly half of patients struggle to stick with it in the first 90 days. The flurry of pills, implants, and now nasal sprays entering trials all share a common goal: giving patients and physicians treatment options for the large share of OSA patients who cannot or will not tolerate a CPAP mask every night. A drug that works locally in the nose, rather than systemically or mechanically, could in principle offer a lower-burden option — no mask, no overnight machine, and potentially fewer of the systemic side effects associated with drugs that act on receptors throughout the body. Mosanna has previously raised venture funding specifically to advance this nasal-spray approach through clinical development.
What This Means for Patients
For patients, MOS118 is not an imminent treatment option — this is an early safety trial in healthy volunteers, and the drug has not yet been tested in anyone with sleep apnea, let alone shown to reduce apnea-hypopnea events or improve outcomes. Years of further trials, including efficacy studies in OSA patients and likely a Phase 3 program, stand between this result and any FDA filing.
What it does signal is that the pipeline of non-CPAP sleep apnea treatments is diversifying beyond pills and surgical implants into entirely new drug classes and delivery methods. Patients who have struggled with CPAP adherence or found existing alternatives unsuitable should know that upper-airway nerve reflexes are now an active target of drug development, alongside oral medications and neurostimulation implants already further along in testing — and should keep an eye on results from Mosanna's next trial, which will be the first real test of whether this approach helps people who actually have the disease.
