Eli Lilly reported late-stage data showing that patients with obesity were able to maintain long-term weight loss after transitioning from higher-dose injectable incretin therapies to either lower-dose Zepbound or the company’s oral GLP-1 therapy Foundayo.

The results underscore growing industry focus on chronic weight management and treatment persistence.

Where did the results come from?

Results from the Phase IIIb Surmount-Maintain and Attain-Maintain studies were presented at the 33rd European Congress on Obesity and simultaneously published in The Lancet and Nature Medicine, respectively.¹

The findings address one of the central challenges facing obesity treatment: weight regain following therapy interruption or dose changes.

“Weight regain remains one of the biggest challenges in obesity care, and is often the result of treatment interruptions that cause biology to work against patients, undoing the progress they’ve made,” said Louis J. Aronne, MD, founder and chair emeritus of the American Board of Obesity Medicine and a Lilly consultant. “These medicines can be used for long-term maintenance today, and results from Surmount-Maintain and Attain-Maintain provide additional evidence of their potential when switching from higher doses of injectable incretin therapy.”

In Surmount-Maintain, patients who continued on maximum tolerated doses of Zepbound maintained nearly all prior weight loss achieved during the initial 60-week treatment period.¹ Participants who stepped down to a 5 mg maintenance dose retained most of their weight reduction, regaining an average of 5.6 kg by Week 112.

Patients entering the maintenance phase had reduced body weight from roughly 112–113 kg at baseline to approximately 89 kg following initial treatment with higher-dose tirzepatide.¹Those remaining on maximum tolerated doses maintained an average weight of 88.7 kg at Week 112.

Meanwhile, the Attain-Maintain trial evaluated transitions from injectable therapies to Lilly’s oral GLP-1 candidate Foundayo (orforglipron). Patients switching from Wegovy to Foundayo maintained all but 0.9 kg of previously achieved weight loss over 52 weeks, while patients transitioning from Zepbound to Foundayo maintained all but 5.0 kg.

“Obesity is a chronic disease requiring long-term treatment, and patients need more options they can stay on for the long run,” said Kenneth Custer, PhD, executive vice president and president of Lilly Cardiometabolic Health. “We are encouraged by the results of Surmount-Maintain and Attain-Maintain, which showed that both Zepbound and Foundayo, a once-daily oral GLP-1, provided durable weight-loss maintenance.”

Why is the trial data important?

The data further strengthens Lilly’s position in the increasingly competitive obesity market, where manufacturers are racing to differentiate therapies not only on magnitude of weight loss but also on convenience, tolerability, and long-term adherence.² 

Safety findings across both trials were generally consistent with prior studies of GLP-1 and incretin therapies. The most common adverse events included gastrointestinal side effects such as nausea, diarrhea, constipation, and vomiting.¹ Discontinuation rates due to adverse events remained relatively low in both studies.

The studies also reinforce broader industry recognition that obesity management may increasingly resemble chronic disease treatment models used in hypertension or diabetes, requiring ongoing therapy to sustain benefits.² As payers, providers, and regulators continue to debate long-term coverage and access for obesity medicines, maintenance data is becoming increasingly important in demonstrating durability of clinical benefit.

Zepbound, Lilly’s dual GIP and GLP-1 receptor agonist tirzepatide, is already approved in the United States for obesity and obstructive sleep apnea in adults with obesity, while Foundayo represents Lilly’s effort to expand into oral GLP-1 therapies.

Orforglipron is also being studied across multiple cardiometabolic and chronic disease indications, including type 2 diabetes, hypertension, osteoarthritis knee pain, and obstructive sleep apnea.²Top of FormBottom of Form

Sources

1. Lilly's Foundayo and lower-dose Zepbound helped people maintain weight loss after switching from higher doses of injectable incretin therapy in two late-phase trials Eli Lilly and Company May 12, 2026 https://www.prnewswire.com/news-releases/lillys-foundayo-and-lower-dose-zepbound-helped-people-maintain-weight-loss-after-switching-from-higher-doses-of-injectable-incretin-therapy-in-two-late-phase-trials-302769938.html
2. Patients don't regain much weight switching from injections to Lilly's weight-loss pill, study finds Reuters May 12, 2026 https://www.reuters.com/legal/litigation/patients-dont-regain-much-weight-switching-injections-lillys-weight-loss-pill-2026-05-12/