The question that has haunted obesity medicine since the GLP‑1 era began is finally getting peer‑reviewed answers. Two Eli Lilly Phase 3 trials presented at the 33rd European Congress on Obesity in Istanbul and published in The Lancet and Nature Medicine tested whether people who hit a weight plateau on injectable GLP‑1 therapy can hold their loss using either a daily oral pill or a lower injectable dose. Both answered yes (Eli Lilly via PR Newswire).
SURMOUNT‑MAINTAIN looked at staying on Zepbound versus dropping to a smaller weekly dose. ATTAIN‑MAINTAIN took people off the needle entirely and put them on a once‑daily pill, Foundayo. In both, the loss largely stuck. After a year on the maintenance protocol, the numbers behaved more like a chronic‑disease control study than the dropout pattern clinicians keep seeing in clinic.
Why this trial pair matters
Patients lose weight on Wegovy or Zepbound. Then they stop, often because of cost, supply, side effects, or simple fatigue. And then a lot of them regain. A 2024 meta‑analysis of 48 GLP‑1 studies put the average one‑year regain after stopping at roughly 60 percent of prior loss (Nasdaq summary). That is the clinical problem these two trials were built to solve, and it is the commercial problem Lilly has been quietly working on for years.
If maintenance can be done with a pill instead of a pen, or a 5 mg shot instead of a 15 mg one, several things change at once. Cost falls. Cold‑chain logistics get easier. Adherence climbs. The obesity drug market starts to look less like an episodic acute treatment and more like statins or antihypertensives — a class taken for the long haul.
SURMOUNT‑MAINTAIN: stay on, step down, or stop
SURMOUNT‑MAINTAIN (NCT06047548) was a 112‑week Phase 3b randomized, double‑blind, placebo‑controlled trial in 441 adults with obesity or overweight and weight‑related comorbidities, without type 2 diabetes (Lilly press release). All participants started with a 60‑week open‑label run‑in on Zepbound at the maximum tolerated dose, defined as 10 mg or 15 mg.
At week 60, anyone who had lost meaningful weight was re‑randomized 3:3:2 to three arms:
- Continue Zepbound at MTD (10 mg or 15 mg)
- Step down to Zepbound 5 mg weekly
- Switch to placebo
The primary endpoint was percent change in body weight at week 112 versus placebo. Both Zepbound arms met it.
What the numbers actually say
Participants who stayed on Zepbound MTD preserved all of their prior weight loss on average over the 52‑week maintenance phase. Step‑down to 5 mg held all but 5.6 kg. The placebo arm regained materially more (Lilly press release).
From baseline, after the full 60‑week initial period plus 52 weeks of maintenance, the MTD continuation group lost 25.2 kg, or 22.4 percent of starting body weight. The 5 mg step‑down group ended at 19.2 kg lost, 17.0 percent of starting weight.
An independent practitioner summary on LinkedIn put the percent‑of‑prior‑loss maintained at 96.5 percent for MTD continuation, 67.9 percent for the 5 mg step‑down, and 42.8 percent for placebo (My Best Weight clinical summary). Rescue therapy — defined as regaining at least half of the prior loss — was triggered in 67 percent of the placebo arm, 25 percent of the 5 mg arm, and 8 percent of the MTD arm.
Safety in maintenance
Adverse events during maintenance were dominated by familiar GLP‑1 gastrointestinal issues but at modest rates. Diarrhea ran 7.2 percent on MTD, 4.9 percent on 5 mg, 1.1 percent on placebo. Vomiting: 6.5, 0.7, and 0 percent. Nausea: 5.8, 4.2, and 2.2 percent. Discontinuation due to adverse events during the maintenance period was essentially zero across all arms (Lilly press release). The pattern is consistent with prior Phase 3 tirzepatide data.
ATTAIN‑MAINTAIN: dropping the needle
ATTAIN‑MAINTAIN (NCT06584916) was structurally different. It enrolled 376 adults who had already finished SURMOUNT‑5, the head‑to‑head trial that compared tirzepatide with semaglutide in obesity. Eligibility required reaching a weight plateau — defined as less than 5 percent body weight change between weeks 60 and 72 of SURMOUNT‑5 — and then opting in for re‑randomization (Lilly press release).
Participants were randomized 3:2 to either daily oral Foundayo or matching placebo, started at 9 mg of Foundayo (or matching placebo), and titrated every four weeks to a maximum tolerated dose of 14.5 mg or 17.2 mg. From week 24 onward, anyone in the placebo arm who regained at least half of their SURMOUNT‑5 weight loss could be moved onto rescue Foundayo. The primary endpoint was percent maintenance of body weight reduction versus placebo at week 52.
It met that endpoint using both the efficacy estimand and the treatment‑regimen estimand.
Foundayo numbers, in plain English
People who had been on full‑dose Wegovy and switched to Foundayo regained, on average, just 0.9 kg over the year. Roughly two pounds. People coming from full‑dose Zepbound regained 5.0 kg. Translated as a percent of prior loss maintained: 82.4 percent for the Wegovy‑to‑Foundayo cohort, 78.0 percent for the Zepbound‑to‑Foundayo cohort (Lilly press release via Trivano).
An Earth.com summary of the Nature Medicine paper added a striking observation: regardless of which injectable came first, both cohorts ended the maintenance year at the same average body weight, roughly 211 pounds. The two paths converged to the same floor (Earth.com report on Nature Medicine paper).
That convergence is unusual and clinically interesting. Tirzepatide produced steeper initial losses in SURMOUNT‑5. After a year of orforglipron maintenance, the steeper trajectory and the gentler trajectory landed in the same neighborhood. It suggests that the long‑run set point on a maintenance‑dose GLP‑1 may be more about the body than about which agent got you there.
ATTAIN‑MAINTAIN safety
Adverse events in ATTAIN‑MAINTAIN tracked prior orforglipron Phase 3 data. Nausea ran around 18.8 percent on Foundayo versus 4.1 percent on placebo; constipation 13.1 vs 4.1 percent; vomiting 8.3 vs 3.4 percent. Discontinuation rates were 4.8 percent in the Foundayo‑from‑Wegovy arm, 7.6 percent in the matching placebo arm, 7.2 percent in the Foundayo‑from‑Zepbound arm, and 6.3 percent in matching placebo. No hepatic safety signal was reported (Lilly December 2025 topline release).
A note on the biology
The body fights weight loss. Leptin falls. Ghrelin rises. Resting metabolic rate drops a little more than basic body‑composition math would predict. Appetite recalibrates upward. Researchers have called this constellation of changes the body’s defended weight, and it is the central reason most lifestyle‑only interventions lose ground after the first year.
GLP‑1 receptor agonists work in part because they push back on those signals. They slow gastric emptying. They shift appetite via central pathways. They reduce the food‑reward signal that drives between‑meal eating. Stopping the medication removes that push. The defended weight reasserts itself.
A maintenance dose — whether a smaller weekly injection or a daily oral GLP‑1 — does not have to do everything the loading dose did. It has to do enough to hold the new equilibrium. SURMOUNT‑MAINTAIN and ATTAIN‑MAINTAIN both suggest the threshold for that holding pattern is lower than the threshold for active weight loss. That is a clinically useful asymmetry. Many patients can be moved to a gentler regimen once they are at their target, instead of staying on the highest tolerated dose forever.
Commercial stakes and the orforglipron context
Foundayo, the brand name Lilly uses for orforglipron, was approved by the FDA on April 1, 2026, under the Commissioner's National Priority Voucher pilot for adults with obesity or overweight with weight‑related medical problems (Prime Therapeutics GLP‑1 pipeline update). Lilly has been pushing it as a strategic complement to Zepbound rather than a replacement: Zepbound to lose, Foundayo to maintain. ATTAIN‑MAINTAIN is the trial that puts evidence behind that positioning.
For Novo Nordisk, the picture is more mixed. The CHMP positive opinion for the Wegovy pill — once‑daily oral semaglutide 25 mg — landed days after the ATTAIN‑MAINTAIN/SURMOUNT‑MAINTAIN readout, giving the company its own oral GLP‑1 narrative in Europe. But ATTAIN‑MAINTAIN deliberately tested Foundayo as the maintenance pill of choice for Wegovy graduates, and the answer it returned — 82.4 percent of prior Wegovy loss preserved with Foundayo — is the kind of data point that travels in payer meetings.
For payers, the calculus shifts. If maintenance can be done on either a step‑down injectable or a daily oral GLP‑1, the per‑member‑per‑year cost of long‑term obesity treatment drops materially. Step‑therapy protocols that today start at lifestyle and graduate to high‑dose injectables can now reasonably end at a lower‑intensity maintenance phase rather than at indefinite full dosing or at discontinuation.
What the trials do not answer
Maintenance studies tell you what happens for a year. They do not tell you what happens for ten. Both SURMOUNT‑MAINTAIN and ATTAIN‑MAINTAIN report 52 weeks of maintenance data. Real obesity management horizons are decades. The next data set, when it lands, will be the one that shows whether the maintenance pattern holds for two and three years.
The trials also enrolled only participants who had already done the work of losing on the loading regimen. People who never tolerated the higher doses, people who quit early, people without payer coverage — they are not in these numbers. Generalizing the maintenance data to those populations needs caution.
And the pool itself is selected. ATTAIN‑MAINTAIN required SURMOUNT‑5 completion plus a documented weight plateau. SURMOUNT‑MAINTAIN required tolerating 60 weeks of Zepbound MTD. Both groups are, by construction, the patients who handle GLP‑1 therapy well. The wider clinical population is broader than that.
Frequently Asked Questions
Is Foundayo a peptide?
No. Foundayo is the brand name for orforglipron, an oral small‑molecule GLP‑1 receptor agonist discovered by Chugai and licensed to Lilly. It binds and activates the same GLP‑1 receptor that the peptide drugs semaglutide and liraglutide hit, but it is not a peptide itself. That distinction is part of why it can be a daily tablet without the absorption workarounds peptide pills like the Wegovy tablet require.
If I am on Zepbound, should I switch to Foundayo for maintenance?
That is a clinical decision between a patient and prescriber and depends on tolerability, payer coverage, side‑effect history, and individual response. What ATTAIN‑MAINTAIN shows is that the switch is a real option that preserved most of the prior loss in a controlled trial. It does not say everyone should switch.
Can I just drop my Zepbound to 5 mg myself?
Self‑titration off a prescribed dose without your prescriber's input is not a good idea. SURMOUNT‑MAINTAIN's 5 mg step‑down was a carefully controlled protocol following 60 weeks of MTD treatment, with rescue therapy available. The trial's results support the concept that a lower maintenance dose works for many people — they do not authorize patients to redesign their own regimens.
What if I stop the GLP‑1 entirely?
The placebo arms in both trials are the answer. In SURMOUNT‑MAINTAIN, two‑thirds of placebo participants triggered rescue therapy by regaining at least half of their prior loss. In ATTAIN‑MAINTAIN, placebo arms preserved 38 to 49 percent of prior loss versus roughly 75 to 80 percent for participants on Foundayo. Most people regain meaningful weight when they stop. That is consistent with the broader meta‑analytic literature on GLP‑1 discontinuation (Nasdaq summary of 48‑study analysis).
Does this affect the compounded semaglutide and tirzepatide market?
Indirectly. The FDA has formally proposed to keep semaglutide, tirzepatide, and liraglutide off the 503B bulks list, with the public comment window closing June 29, 2026 (Frier Levitt FDA analysis). As approved oral and lower‑dose injectable maintenance options proliferate, the clinical argument for compounded substitutes from outsourcing facilities weakens further.
Are side effects worse on maintenance?
No — in fact the maintenance‑period adverse event rates in SURMOUNT‑MAINTAIN were lower than what is typically seen during loading and titration. Nausea, vomiting, and diarrhea rates were in single digits on Zepbound MTD continuation. Maintenance phases also tend to filter out patients who could not tolerate the loading dose, which contributes to the better tolerability profile.
Sources
- Eli Lilly and Company — 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, May 12, 2026.
- Medical News Today — GLP‑1 drugs: Lower dose or oral pill may help sustain weight loss, May 25, 2026.
- Earth.com — New weight‑loss pill may help people keep the pounds off after stopping GLP‑1 injections, May 23, 2026 (covering the Nature Medicine ATTAIN‑MAINTAIN publication).
- Eli Lilly — ATTAIN‑MAINTAIN topline (December 2025 release).
- Frier Levitt — FDA Proposes to Exclude GLP‑1 Receptor Agonists from the 503B Bulks List, May 20, 2026.
- Prime Therapeutics — GLP‑1 Pipeline Update: May 2026.
- Nasdaq — From Zepbound to Foundayo: Lilly's Latest Results Support Oral GLP‑1 Outlook, May 20, 2026.
Sources & References
- FDA PCAC Meeting Announcement (July 23-24, 2026)
- PBS: FDA to Weigh Easing Limits on Peptides Favored by RFK Jr.
- BioPharma Dive: FDA Peptides RFK Advisory Committee Restrictions
- RAPS: FDA Considers Adding a Dozen Peptides to Bulk Drug List
- Ars Technica: RFK Jr. Forces FDA to Reconsider 12 Peptides
- ProPublica: Peptide Safety Investigation
- New York Times: Peptide Ban FDA RFK Jr.
- SSRP Institute: FDA Announces Change in Status of 12 Peptides
- CNBC: RFK Jr. Peptides Hims Hers GLP-1
- USA Today: RFK Jr. FDA Peptides Explainer
