Retatrutide: The Triple Agonist in Development

Q: What does the retatrutide trial data actually show?

In TRIUMPH-1, the pivotal Phase 3 trial, participants lost an average of 19.0% (4 mg), 25.9% (9 mg), and 28.3% (12 mg) of body weight at 80 weeks, versus 2.2% on placebo. It is not approved. Lilly has said it plans to file for FDA approval in 2027, so it is not something you can start today. Side effects in TRIUMPH-1 were mostly gastrointestinal and dose-dependent — nausea in 28.6-42.4% across doses versus 14.8% on placebo, with similar patterns for diarrhea and constipation.

The triple agonist targeting GLP-1, GIP, and glucagon — what the TRIUMPH Phase 3 trials showed.

Published August 22, 2026Updated September 10, 20269 min readWritten and fact-checked against the sources below

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Retatrutide is not yet approved. This is educational, not medical advice.

Retatrutide is the next-generation GLP-1 in development — a triple agonist targeting GLP-1, GIP, and glucagon receptors. It's the molecule most people are watching as the potential successor to the current generation.

How does retatrutide work?

Adding a third target — glucagon — is the new element. Glucagon is associated with increased energy expenditure, so a triple agonist is theorized to drive even more weight loss than the dual (tirzepatide) and single (semaglutide) agents.

What does the retatrutide trial data actually show?

In TRIUMPH-1, the pivotal Phase 3 trial, participants lost an average of 19.0% (4 mg), 25.9% (9 mg), and 28.3% (12 mg) of body weight at 80 weeks, versus 2.2% on placebo.
It is not approved. Lilly has said it plans to file for FDA approval in 2027, so it is not something you can start today.
Side effects in TRIUMPH-1 were mostly gastrointestinal and dose-dependent — nausea in 28.6-42.4% across doses versus 14.8% on placebo, with similar patterns for diarrhea and constipation.

Should you wait for retatrutide?

Retatrutide is not available to start. If you're evaluating options today, the current generation (semaglutide, tirzepatide) is what's actually accessible. Keep an eye on it, but don't let 'waiting for the next one' become a reason to defer care you could get now.

Bottom line

Retatrutide is the most promising next-gen GLP-1 on the trial data, but it's not approved or available yet. Today's options are semaglutide and tirzepatide. This is information, not a prescription.

Want this handled for you?

LunaRx — clinician-led GLP-1 care with a plan to come off

LunaRx connects you with a licensed clinician for an online evaluation. Depending on your state that is a live or a store-and-forward visit. If the clinician determines a GLP-1 is appropriate for you, a licensed pharmacy dispenses it — with a plan to come off when you’re ready. The prescribing decision is the clinician’s alone, and approval is not guaranteed.

Start the 2-minute eligibility checkIndependent site · by LunaRx · not medical advice

Sources

Primary sources for the claims in this article. Trial results are reported as published; prescribing information is the authoritative reference for dosing and safety.

1.
TRIUMPH-1: Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial
Eli Lilly and Company (sponsor release) · 2026
At 80 weeks in 2,339 adults: −19.0% (4 mg), −25.9% (9 mg), −28.3% (12 mg) versus −2.2% placebo.
2.
TRIUMPH: Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials
PubMed · 2025
Design and naming of the retatrutide Phase 3 registrational program (TRIUMPH).

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