Retatrutide: where the phase 3 program stands

The short answer: retatrutide has now reported positive topline results from five phase 3 trials, and one of those trials is published in a peer-reviewed journal. It is still not approved by FDA, it cannot be compounded, and the only lawful way to receive it is inside a clinical trial. [7]

This explainer tracks evidence and legal status. It does not cover dosing.

What retatrutide is

Retatrutide is a once-weekly injection that activates three hormone receptors: GIP, GLP-1, and glucagon. Tirzepatide activates the first two, and semaglutide only GLP-1. The glucagon arm is the new part. [2]

The phase 2 obesity trial set expectations. Among 338 adults, mean weight change at 48 weeks was minus 24.2% on the 12 mg dose versus minus 2.1% on placebo. [1]

The phase 3 program

The obesity program, called TRIUMPH, has four registrational trials with more than 5,800 participants. TRIUMPH-1 and TRIUMPH-2 are weight management trials with nested sub-studies for sleep apnea and knee osteoarthritis, TRIUMPH-3 enrolls people with cardiovascular disease, and TRIUMPH-4 is a standalone knee osteoarthritis trial. [2] A separate TRANSCEND program covers type 2 diabetes. [3]

Here is every readout so far, in date order.

December 2025: TRIUMPH-4 (obesity with knee osteoarthritis). At 68 weeks, weight change was minus 28.7% on 12 mg and minus 26.4% on 9 mg versus minus 2.1% on placebo, with large reductions in knee pain scores. [5]

March 2026: TRANSCEND-T2D-1 (type 2 diabetes). This is the one published in full, in June 2026. In 537 adults with type 2 diabetes managed with diet and exercise alone, HbA1c fell by 1.69 to 1.94 percentage points at 40 weeks versus 0.81 on placebo, and body weight fell by 11.5% to 15.3% versus 2.6%. Discontinuations for adverse events were 2% to 5% with retatrutide and 0% with placebo. [3]

May 2026: TRIUMPH-1 (obesity without diabetes). 2,339 participants over 80 weeks. Weight change was minus 19.0%, minus 25.9%, and minus 28.3% on 4, 9, and 12 mg versus minus 2.2% on placebo (efficacy estimand), or minus 17.6% to minus 25.0% versus minus 3.9% counting everyone regardless of adherence. [6]

July 2026: TRIUMPH-2 and TRIUMPH-3. In adults with obesity and type 2 diabetes, weight change reached minus 20.8% on 12 mg versus minus 4.0% on placebo. In adults with severe obesity and established cardiovascular disease, it reached minus 22.6% on 12 mg versus minus 3.2%. [7]

The manufacturer says it now has the clinical data package to support submissions for obesity, knee osteoarthritis pain, and obstructive sleep apnea. [7] A submission is not an approval, and we do not predict review timelines.

What the safety data show so far

The side effect profile looks like the rest of the class, with one new signal. In TRIUMPH-1, the most common adverse events on 12 mg were nausea (42.4% versus 14.8% on placebo), diarrhea, constipation, and vomiting. Dysesthesia, an abnormal skin sensation, occurred in 12.5% on 12 mg versus 0.9% on placebo, and was mostly mild to moderate. Discontinuation for adverse events was 11.3% on 12 mg versus 4.9% on placebo. [6] In TRIUMPH-3, discontinuation reached 13.5% on 12 mg versus 4.8%. [7]

Those higher discontinuation rates at the top dose will matter to regulators and prescribers. So will the outcome data still to come: a cardio-kidney outcome trial, TRIUMPH-Outcomes, is ongoing, and a mechanistic kidney trial is under way. [4]

What is still missing

• Peer review for most results. Four of the five phase 3 readouts are company press releases. Full papers let outside readers check the methods, the dropouts, and the safety tables.
• Cardiovascular outcomes. TRIUMPH-3 was designed around weight, not heart events, and its cardiovascular analyses had wide confidence intervals that crossed no effect. [7]
• Head-to-head data. No published trial compares retatrutide directly with tirzepatide or semaglutide. Our tirzepatide vs retatrutide and semaglutide vs retatrutide comparisons use separate trials and say so.

When will retatrutide be available?

There is no approval date, and we do not predict one. What can be said is what has to happen first. The manufacturer says it has the phase 3 data to support submissions for obesity, knee osteoarthritis pain, and obstructive sleep apnea. [7]

The steps after that are set by FDA's review process:

• Submission and filing. The manufacturer files a new drug application with the full trial data, and FDA's review clock runs from a 60 day filing date after the application arrives.
• Review. For a new molecular entity, FDA's goal is to act on 90% of standard applications within 10 months of the filing date, and 90% of priority applications within 6 months. [11] These are targets, not promises: FDA can ask for more data, and an action can be a rejection.
• Label. If approved, retatrutide would be a prescription drug limited to the uses on its label, with a dose schedule and warnings written from the trials.

Until an approval, the only lawful way to receive retatrutide is inside a clinical trial. The manufacturer describes it as legally available only to participants in its trials. [6] Our guide to how to get retatrutide covers trial enrollment and expanded access, and the retatrutide cost page explains why it has no lawful price yet.

Why no one can lawfully sell it today

Retatrutide is not approved anywhere. It is not a component of an approved drug and does not appear on FDA's 503A bulk substance lists, so pharmacies have no lawful basis to compound it. [9] FDA has issued warning letters to telehealth companies for marketing retatrutide to consumers, to ingredient distributors for selling it to compounders, and to outsourcing facilities for repackaging it. [8] Products sold online as "research" retatrutide have no verified identity or dose.

For athletes, it is prohibited at all times under section S0 of the WADA list, which covers substances with no government approval for human use. [10]

Where it fits

If retatrutide is approved, it would join a crowded class. The retatrutide vs survodutide comparison covers the other glucagon-containing candidate. Every date and filing is logged on the retatrutide regulatory tracker, and the GLP-1 hub shows where each drug in the class stands today.