Medications

TRIUMPH-1 decoded: what retatrutide's Phase 3 results actually mean

TRIUMPH-1 found 28.3% mean weight loss at 80 weeks on 12mg retatrutide. Here's what that means — and what it doesn't yet.

4 min read · Updated 2026-06-13

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Key takeaways

TRIUMPH-1 found 28.3% mean weight loss at 80 weeks on 12 mg retatrutide; 45.3% of participants achieved ≥30% weight loss
These are topline corporate press release results — full peer-reviewed publication is pending
Retatrutide is investigational. No NDA has been filed. There is no approved prescribing pathway.
Lower doses: 4 mg →19.0%, 9 mg →25.9%
Retatrutide activates three receptors (GLP-1, GIP, glucagon) — a different mechanism from approved drugs

What retatrutide is

Retatrutide is a once-weekly injectable under investigation by Eli Lilly for treatment. It acts as a — activating the (same target as ), the receptor (also targeted by tirzepatide), and the receptor.

The glucagon receptor component distinguishes retatrutide from all currently approved GLP-1 medications. Glucagon stimulates the liver to release energy and increases calorie burning. Whether this triple mechanism is clinically superior to dual or single agonism at the same price and safety profile is still being studied.

What TRIUMPH-1 found

TRIUMPH-1 enrolled adults with obesity (without ) and randomized them to receive 4 mg, 9 mg, or 12 mg of retatrutide weekly, or , over 80 weeks.

At 80 weeks, mean weight loss:

4 mg: 19.0%
9 mg: 25.9%
12 mg: 28.3% (approximately 70.3 lbs average)

Among participants on the 12 mg dose, 45.3% lost 30% or more of their body weight. Extended follow-up at 104 weeks found 30.3% mean weight loss on the highest dose. The trial met its primary and key secondary endpoints.

These figures are from Lilly's June 2026 press release. The full peer-reviewed paper has not yet been published. Published trial data sometimes differ from corporate topline releases in secondary endpoints, adverse event profiles, and discontinuation rates.

How these results compare to approved medications

For context:

Semaglutide 2.4 mg (Wegovy): approximately 14.9% mean weight loss at 68 weeks in STEP 1
Tirzepatide 15 mg (Zepbound): approximately 20.9% at 72 weeks in SURMOUNT-1

The 28.3% figure is substantially higher. However, direct head-to-head comparisons are not available, trial populations differ, and retatrutide has not completed the regulatory review process.

What the data does not tell us

Safety: Full adverse event profile not yet published. The additional glucagon receptor activity raises questions about effects on heart rate, blood pressure, and liver .

Cardiovascular outcomes: No long-term CVOT has been published. The SELECT trial established a cardiovascular benefit for semaglutide. No equivalent data exists for retatrutide.

Long-term weight maintenance: Post-discontinuation weight regain pattern not yet studied in controlled trials.

Regulatory pathway: Lilly has not announced an NDA filing date.

What remains uncertain

Lilly is running a broader program including type 2 diabetes trials. The peer-reviewed publication of TRIUMPH-1 data will be the next meaningful signal.

Questions to ask your clinician

Is retatrutide currently available by prescription? (No — as of June 2026)
Are there clinical trials enrolling for retatrutide relevant to my situation?
How does the evidence for retatrutide compare to approved options for my health profile?

TRIUMPH-1 is a significant result. But promising Phase 3 data from a corporate press release is a long way from a drug you can get a prescription for. The path — peer-reviewed publication, NDA filing, FDA review, approval, commercial availability — takes years. The drugs your prescriber can actually prescribe today are tirzepatide (Zepbound), semaglutide (Wegovy), and oral orforglipron (Foundayo).

Medical disclaimer: This content is for educational purposes only and is not medical advice. Always consult a licensed healthcare professional before starting, stopping, or changing any treatment.

Sources

Eli Lilly TRIUMPH-1 press release: https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-[retatrutide](/learn/semaglutide-vs-retatrutide-what-we-know)-delivered-powerful-weight-loss
AJMC coverage: ajmc.com
ClinicalTrials.gov NCT05929118: clinicaltrials.gov

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