A drug originally developed for obesity and diabetes has posted some of the largest reductions in sleep apnea severity seen in a randomized trial. Full results from two phase 3 studies of retatrutide, published in the New England Journal of Medicine and presented at the European Sleep Research Society's SleepEurope 2026 congress, show that Eli Lilly's experimental triple-hormone receptor agonist substantially improved breathing during sleep in adults with obstructive sleep apnea (OSA) and excess weight — regardless of whether they also had type 2 diabetes.
Two Trials, One Consistent Signal
The TRIUMPH-1-OSA and TRIUMPH-2-OSA trials, led by researcher Ronald R. Grunstein and colleagues, together enrolled 691 adults with moderate-to-severe obstructive sleep apnea and a body mass index of at least 27. TRIUMPH-1-OSA studied participants with obesity or overweight but without type 2 diabetes; TRIUMPH-2-OSA enrolled a parallel group that also had type 2 diabetes. Both were randomized, double-blind, placebo-controlled trials that assigned participants to once-weekly injections of retatrutide at 4 mg, 9 mg, or 12 mg doses, or to placebo.
Retatrutide is a triple agonist, meaning it activates receptors for three separate hormones — GLP-1, GIP, and glucagon — rather than the single or dual mechanisms used by earlier weight-loss drugs such as semaglutide or tirzepatide. That broader mechanism is thought to drive both its weight-loss potency and its downstream effect on the upper airway.
How Much the Apnea-Hypopnea Index Fell
Across both trials, the higher retatrutide doses produced significantly larger reductions in the apnea-hypopnea index (AHI) — the standard measure of how many times per hour breathing is disrupted during sleep — than placebo. In TRIUMPH-1-OSA, participants with a baseline AHI of 58.6 events per hour saw reductions of up to 36.1 events per hour on the highest dose, a drop of roughly 60.6%. Placebo groups in both trials showed far smaller changes.
The weight loss driving much of that improvement was substantial: participants on the 9 mg and 12 mg doses lost a mean of 17.9% to 22.2% of their body weight over the trial period, compared with 4.8% to 5.6% among those on placebo — figures in line with retatrutide's performance in earlier obesity-focused trials.
Why Diabetes Status Didn't Blunt the Effect
A key question going into TRIUMPH-2-OSA was whether type 2 diabetes — which independently affects metabolism, fat distribution, and sometimes autonomic nerve function in the upper airway — would dampen the drug's effect on apnea. It did not. Researchers reported meaningful AHI reductions in the diabetic cohort as well, reinforcing that the benefit tracks with weight loss and metabolic improvement rather than being limited to a specific subgroup.
This matters clinically because type 2 diabetes and obstructive sleep apnea frequently co-occur, and patients with both conditions often face compounded cardiovascular risk. A therapy shown to improve both the metabolic and respiratory sides of that overlap in the same trial program is unusual.
Where This Fits Among Weight-Loss Drugs for Apnea
Retatrutide is not the first incretin-based drug tested against OSA. Tirzepatide (Zepbound) became the first FDA-approved medication for obesity-related obstructive sleep apnea in December 2024, after the SURMOUNT-OSA trial found AHI reductions of 25 to 29 events per hour. The TRIUMPH results suggest retatrutide's triple-receptor mechanism may push those reductions even further, though cross-trial comparisons are not definitive, since the two drugs were tested in different patient populations using different protocols.
Retatrutide has not yet been submitted to the FDA for an OSA indication, and Lilly's broader retatrutide development program for obesity and diabetes is still working through regulatory review. Longer-term data on durability and safety beyond the trial period are not yet available.
What This Means for Patients
For the large population of people with obesity-related obstructive sleep apnea — many of whom struggle to tolerate CPAP long-term — these results add to a growing body of evidence that treating the metabolic root cause can meaningfully improve breathing during sleep, not just body weight. That said, retatrutide remains investigational for this indication, and patients with moderate-to-severe OSA should not view it as a near-term replacement for CPAP, oral appliances, or other established therapies. The presence of type 2 diabetes does not appear to limit the drug's apnea benefit, which may eventually make it a candidate for patients navigating both conditions at once — but that will depend on FDA review, long-term safety data, and how insurers eventually decide to cover it.
