Retatrutide vs Semaglutide: Phase 3 TRIUMPH-1 Data Compared
Retatrutide is a triple agonist hitting GLP-1, GIP, and glucagon receptors. Semaglutide (Ozempic/Wegovy) is a single agonist hitting only GLP-1. As of August 2026, retatrutide has Phase 3 topline results and semaglutide has an FDA approval with years of post-market data, which is the difference that actually matters for anyone deciding on treatment this year.
Status as of August 2026: Retatrutide is investigational. Topline Phase 3 TRIUMPH-1 results were announced May 21, 2026; TRIUMPH-2 and TRIUMPH-3 have not read out and no FDA submission has been announced. Semaglutide is approved and marketed as Ozempic (type 2 diabetes) and Wegovy (chronic weight management).
Head-to-Head Summary
Every efficacy figure below is a cross-trial comparison. Retatrutide and semaglutide have never been tested against each other in a randomized trial, so treat the gap as an estimate rather than a measured difference.
| Factor | Retatrutide | Semaglutide |
|---|---|---|
| Receptor targets | GLP-1, GIP, glucagon (triple) | GLP-1 only (single) |
| Regulatory status | Investigational, not approved | FDA approved (diabetes 2017; Wegovy for weight loss 2021) |
| Best Phase 3 weight loss | 28.3% at 80 weeks (12 mg, TRIUMPH-1) | Roughly 15% at comparable maintenance timepoints |
| Extended-duration data | 30.3% at 104 weeks (BMI 35+ subgroup, n=532) | Multi-year post-market safety and efficacy data |
| Pivotal trial size | 2,339 (TRIUMPH-1) | Varies by trial; STEP program totals in the thousands |
| Nausea, top dose | 42.4% (12 mg) vs 14.8% placebo | Roughly 40-50% during escalation |
| Discontinuation for AEs, top dose | 11.3% (12 mg) vs 4.9% placebo | Typically single digits |
| Dosing | Once weekly subcutaneous, 2 mg start | Once weekly subcutaneous, 0.25 mg start |
| Can you get it today | No | Yes, with a prescription |
| Manufacturer | Eli Lilly | Novo Nordisk |
For the single-agonist side of this comparison in more depth, see Ozempic vs Wegovy and which GLP-1 is best for weight loss.
What TRIUMPH-1 Actually Showed
TRIUMPH-1 (NCT05929066) was a randomized, double-blind, placebo-controlled Phase 3 trial in 2,339 adults with obesity or overweight plus at least one weight-related comorbidity, excluding people with diabetes. Topline results were announced May 21, 2026.
- 4 mg: 19.0% mean weight loss at 80 weeks
- 9 mg: 25.9% at 80 weeks
- 12 mg: 28.3% at 80 weeks
- Responder rate: 45.3% of the 12 mg group lost 30% or more of body weight
A prespecified blinded extension continued 532 participants with baseline BMI of 35 or higher out to 104 weeks at their maximum tolerated dose. Participants originally randomized to 12 mg reached 30.3% mean loss, the figure most often quoted in headlines. That number comes from a selected subgroup that tolerated two years of treatment, not the full trial population.
Full detail: retatrutide TRIUMPH-1 results. For three years, the number attached to retatrutide was 24.2% at 48 weeks, from the smaller Phase 2 trial (n=338, placebo-controlled, published in the New England Journal of Medicine in 2023). TRIUMPH-1 supersedes that figure with a larger population and a longer treatment window; the two are not directly comparable given the roughly eight-month difference in follow-up.
Triple vs Single Agonism: The Mechanistic Argument
Semaglutide activates one receptor. Retatrutide activates three.
- GLP-1 receptor (shared by both drugs): suppresses appetite, slows gastric emptying, improves glucose-dependent insulin release
- GIP receptor (retatrutide only): improves insulin sensitivity and appears to blunt some of the nausea burden of GLP-1 agonism at matched efficacy
- Glucagon receptor (retatrutide only): raises resting energy expenditure and hepatic fat oxidation
The GLP-1 arm reduces how much you eat. The glucagon arm increases how much you burn. That combination is the mechanistic thesis behind retatrutide, and TRIUMPH-1 is the first large trial to test it at Phase 3 scale. The glucagon arm is also why cardiovascular monitoring gets more attention with retatrutide than with a pure GLP-1 drug like semaglutide, since glucagon agonism can raise heart rate.
Side Effects and Tolerability
TRIUMPH-1 adverse event rates by dose (4 mg, 9 mg, 12 mg) against placebo:
| Adverse event | 4 / 9 / 12 mg | Placebo |
|---|---|---|
| Nausea | 28.6% / 38.4% / 42.4% | 14.8% |
| Diarrhea | 25.2% / 34.1% / 32.0% | 13.5% |
| Constipation | 23.8% / 25.9% / 26.1% | 10.9% |
| Vomiting | 10.6% / 22.8% / 25.3% | 4.8% |
| Discontinued for AEs | 4.1% / 6.9% / 11.3% | 4.9% |
Semaglutide's dose-escalation side effects are the same general class, GI upset concentrated in the first weeks after each dose increase, documented across years of post-market reporting. Both drugs carry FDA warning language for pancreatitis risk and, from animal studies, thyroid C-cell tumor risk; neither should be used by anyone with a personal or family history of medullary thyroid cancer or MEN2.
See also retatrutide side effects and Wegovy side effects.
Approval Status and Access
Semaglutide is FDA-approved as Ozempic for type 2 diabetes and as Wegovy for chronic weight management, and it is widely available from pharmacies nationwide with a prescription, with multiple years of post-approval monitoring.
Retatrutide cannot be prescribed or dispensed as an approved medication anywhere. Lilly has said additional Phase 3 readouts are expected during 2026, including TRIUMPH-2 in adults with obesity and type 2 diabetes and TRIUMPH-3 in adults with established cardiovascular disease. A new drug application would follow those readouts, and FDA review typically takes another 10 to 12 months after submission. There is no announced submission date, so any specific approval month circulating online is speculation.
On the gray market: vials sold online as research-use-only retatrutide sit outside the regulated supply chain with no verified identity, purity, sterility, or dose accuracy. Read retatrutide availability and research peptides before assuming what arrives in the mail matches the label. Track approval status at retatrutide FDA approval.
Cost
Semaglutide list price runs roughly $900-$1,300 per month uninsured for Ozempic or Wegovy, though many insurance plans cover it and manufacturer savings programs can bring the out-of-pocket cost down substantially. Retatrutide has no launch price because it is not approved; compounded research-use vials are sold outside the regulated market at prices that carry no guarantee of accuracy since the product itself is unverified. See Ozempic cost and Wegovy cost for current, date-stamped figures, and retatrutide cost for what is knowable about the gray market today.
Who Should Choose What
Semaglutide is the practical choice for anyone who needs treatment now: FDA approval, broad pharmacy access, insurance coverage in many plans, and years of established safety data. Retatrutide is not a choice available to anyone today. If you've plateaued on semaglutide, the near-term alternative a provider can actually prescribe is tirzepatide (Mounjaro or Zepbound), not retatrutide. See semaglutide vs tirzepatide.
Switching between GLP-1 class drugs should only be done under provider guidance, since the medications differ in potency and titration schedule and switching abruptly can cause appetite rebound or unexpected side effects.
Frequently Asked Questions
On weight loss, the Phase 3 numbers favor retatrutide. Retatrutide 12 mg produced 28.3% mean weight loss at 80 weeks in TRIUMPH-1. Semaglutide (Ozempic/Wegovy) produces roughly 15% at comparable maintenance timepoints in its own trials. The two drugs have never been tested against each other in a randomized trial, so this is a cross-trial comparison, not a head-to-head result. Semaglutide is FDA-approved and available today; retatrutide is investigational and cannot be legally prescribed or dispensed as of August 2026.
In cross-trial terms, roughly 13 percentage points more at comparable timepoints: 28.3% for retatrutide 12 mg at 80 weeks in TRIUMPH-1 versus approximately 15% for semaglutide. That gap should be read as an estimate, not a precise measurement, since the trials differ in duration, population, and titration schedule.
No. There is no completed randomized trial that assigned patients to retatrutide or semaglutide and measured both directly. TRIUMPH-1, the Phase 3 retatrutide trial, was placebo-controlled, as was the earlier Phase 2 trial published in the New England Journal of Medicine in 2023. Every retatrutide-vs-semaglutide number, including the ones on this page, is a cross-trial comparison.
Eli Lilly announced topline TRIUMPH-1 results on May 21, 2026. In 2,339 adults with obesity or overweight plus at least one weight-related comorbidity and no diabetes (NCT05929066), mean weight loss at 80 weeks was 19.0% on 4 mg, 25.9% on 9 mg, and 28.3% on 12 mg. A prespecified 104-week extension in 532 participants with baseline BMI of 35 or higher reached 30.3% mean loss in the 12 mg arm. This superseded the earlier Phase 2 figure of 24.2% at 48 weeks (n=338), which is now outdated and should not be cited as current.
Yes. Semaglutide is approved as Ozempic for type 2 diabetes and as Wegovy for chronic weight management. Retatrutide is investigational, with no FDA submission date announced as of August 2026. Lilly has said additional Phase 3 readouts, including TRIUMPH-2 and TRIUMPH-3, are expected during 2026 before any filing would follow.
Both cause dose-dependent gastrointestinal side effects during titration. In TRIUMPH-1, nausea was 28.6%, 38.4%, and 42.4% at 4/9/12 mg versus 14.8% on placebo, and discontinuation for adverse events was 4.1%, 6.9%, and 11.3% versus 4.9% on placebo. Semaglutide’s side effect profile is well documented after years of post-market use and generally runs somewhat lower than retatrutide’s top-dose rates, though the two have not been compared in the same trial.
There is no legitimate price comparison to make. Semaglutide has an established list price (roughly $900-$1,300 per month uninsured for Ozempic or Wegovy, often much less with insurance or manufacturer savings programs). Retatrutide has no launch price because it is not approved. Compounded research-use vials sold online are outside the regulated market, and any price quoted for them carries no guarantee that the product matches the label.
You cannot switch to retatrutide today because it is not an approved, prescribable medication. If you have plateaued on semaglutide, the option a provider can actually prescribe right now is tirzepatide (Mounjaro or Zepbound), not retatrutide. Any switch between GLP-1 class drugs should be planned with a licensed clinician, since the medications differ in potency and titration schedule.
Informational only, not medical advice. Retatrutide is an investigational drug not approved by the FDA or any other regulator as of August 2026 and cannot be legally prescribed or dispensed. TRIUMPH-1 figures are from Eli Lilly's topline announcement of May 21, 2026; full peer-reviewed results had not published as of this writing and numbers may be revised. Semaglutide comparisons are cross-trial, not head-to-head. Talk to a licensed clinician about treatment decisions.