Orforglipron for sleep apnea: ATTAIN-OSA

A Phase 3 trial called ATTAIN-OSA is testing whether orforglipron, an oral once-daily GLP-1 receptor agonist developed by Eli Lilly, can reduce the severity of moderate-to-severe obstructive sleep apnea (OSA) in adults with obesity or overweight. The trial design and baseline characteristics were published in June 2026 in Contemporary Clinical Trials Communications^[1].

This article explains what the protocol involves, who is enrolled, what the trial is trying to measure, and how this fits into the broader picture of GLP-1 drugs and sleep apnea.

What is orforglipron?

Orforglipron (also called LY3502970) is a non-peptide, small-molecule GLP-1 receptor agonist taken orally once daily. Unlike injectable GLP-1 drugs such as semaglutide or tirzepatide, it does not require a subcutaneous injection, and it carries no food or fluid restrictions before dosing. A Phase 2 obesity trial published in the New England Journal of Medicine in 2023 reported weight reductions of 9.4% to 14.7% at 36 weeks across the active dose arms, versus 2.3% on placebo^[2].

A Phase 3 obesity trial called ATTAIN-1, also published in the New England Journal of Medicine in 2025, enrolled 3,127 adults and tested orforglipron at 6, 12, and 36 mg over 72 weeks. The highest dose (36 mg) produced a mean weight reduction of 11.2% versus 2.1% on placebo at 72 weeks. Approximately 54.6% of participants on 36 mg lost at least 10% of their body weight^[3]. None of these trials included patients with OSA as a primary population, which is what ATTAIN-OSA addresses.

Why test an oral GLP-1 drug in sleep apnea?

Obstructive sleep apnea is closely linked to obesity. Excess adipose tissue around the neck and upper airway narrows the breathing passage during sleep, causing the repeated pauses in breathing that characterise the condition. The gold-standard treatment is positive airway pressure (PAP) therapy, delivered through a mask worn during sleep. PAP is effective when used correctly, but adherence is notoriously poor. The ATTAIN-OSA protocol paper notes that poor adherence to PAP and the barriers to using injectable therapies were part of the rationale for evaluating an oral once-daily option^[1].

Eli Lilly's injectable tirzepatide had already established proof of concept in this space. The SURMOUNT-OSA Phase 3 trial, whose design was published in Contemporary Clinical Trials in 2024, enrolled 469 adults with moderate-to-severe OSA and obesity across two sub-studies (PAP-naive patients and PAP users who completed a washout) and used the same primary endpoint as ATTAIN-OSA: change in the apnea-hypopnea index (AHI) at 52 weeks^[4]. The FDA approved tirzepatide for OSA in adults with obesity in December 2024 under the brand name Zepbound, based in part on those results.

ATTAIN-OSA: what the protocol says

ATTAIN-OSA (NCT06649045) is a Phase 3 master protocol comprising two randomised, double-blind, placebo-controlled sub-studies running for 52 weeks^[1].

Study 1 enrolls adults who have not started PAP therapy (PAP-naive participants). Study 2 enrolls PAP users who complete a washout period before randomisation. In both sub-studies, participants receive either placebo or one of three orforglipron doses (12, 24, or 36 mg daily). Total enrollment across both sub-studies is 712 participants^[1].

All participants have moderate-to-severe OSA, defined in the protocol as an apnea-hypopnea index of at least 15 events per hour, alongside obesity or overweight. That mirrors the eligibility criteria used in SURMOUNT-OSA.

What the trial is measuring

The primary endpoint is change in the apnea-hypopnea index at week 52, measured by polysomnography^[1]. The AHI counts apnea and hypopnea events per hour of sleep. Reducing it is the standard regulatory measure of OSA treatment efficacy.

Key secondary endpoints include hypoxic burden (a measure of oxygen desaturation during sleep), sleep-related impairment scores using validated patient-reported outcome instruments, C-reactive protein levels as a systemic inflammation marker, and body weight changes^[1]. The inclusion of inflammatory markers and patient-reported outcomes alongside the AHI suggests the trial is designed to capture whether any benefit extends beyond the breathing metric alone.

How ATTAIN-OSA compares to SURMOUNT-OSA

The structural similarity between the two trials is intentional. Both use a master protocol with PAP-naive and PAP-user sub-studies, both run for 52 weeks, and both use AHI change as the primary endpoint. Both enrolled patients with moderate-to-severe OSA plus obesity. The SURMOUNT-OSA design has already been reviewed on the tirzepatide page.

The key differences are the drug and the delivery route. SURMOUNT-OSA studied tirzepatide given as a subcutaneous injection once a week^[4]. ATTAIN-OSA studies orforglipron given as an oral tablet once daily. The ATTAIN-OSA protocol enrolled 712 participants versus 469 in SURMOUNT-OSA, giving the newer trial a larger sample. ATTAIN-OSA also tests three dose levels (12, 24, and 36 mg), whereas SURMOUNT-OSA used a tirzepatide dose-escalation approach to a maximum approved dose.

Whether the oral route matters for real-world OSA outcomes is a question the trial may be able to address, since the ATTAIN-OSA paper specifically cites adherence barriers with PAP and injection-based therapies as part of the design rationale.

What this trial does not tell us yet

ATTAIN-OSA is a design and baseline characteristics paper, not a results paper. The 712 participants have been randomised, but the 52-week efficacy and safety data are not yet available^[1]. The trial cannot yet answer whether orforglipron reduces AHI, by how much, or whether any effect is durable beyond the trial period.

Cross-trial comparisons with SURMOUNT-OSA are not reliable at this stage. Differences in patient populations, dose-escalation schedules, and the drug itself make it difficult to predict how ATTAIN-OSA results will compare. For context on the drug's weight-loss record, see the semaglutide and tirzepatide pages, which track the approved GLP-1 drugs in this class.

Orforglipron is currently investigational for the OSA indication. It is not approved by any regulatory agency for sleep apnea. The FDA approved tirzepatide (Zepbound) for this indication in December 2024; orforglipron does not yet have that approval.

This article is for informational and educational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before making any treatment decisions.