The first two phase 3 trials of retatrutide were published in peer-reviewed journals on September 29, 2026: TRIUMPH-1 in the New England Journal of Medicine and TRIUMPH-2 in The Lancet.
What changed. Until now, phase 3 results existed only as Lilly press releases. TRIUMPH-1 randomized 2,339 adults with obesity and no diabetes. Over 80 weeks, average weight change was -17.6%, -23.7% and -25.0% on 4, 9 and 12 mg, versus -3.9% on placebo, counting everyone randomized whether or not they stayed on the drug. TRIUMPH-2 randomized 1,152 adults with obesity and type 2 diabetes: -11.9%, -16.8% and -18.8%, versus -5.1%. TRIUMPH-1 also met its goals for knee osteoarthritis pain and sleep apnea in subgroups.
What it means. These conservative numbers are now in the peer-reviewed record, and they are a few points lower than the headline figures in Lilly’s releases, which assumed everyone stayed on treatment. The Lancet paper adds safety detail: low blood pressure in up to 6% and dysesthesia, a skin-sensation side effect, in up to 7% on retatrutide, against 1% or less on placebo.
If you take this or are considering it. If you are comparing retatrutide with what you take now, use the numbers in this item. They count everyone randomized, including people who stopped, which sits closer to real use than a figure assuming everyone stayed on the drug. Comparing across separate trials is still unreliable, because the people and the lengths differ. With type 2 diabetes, 18.8% is the figure that applies to you. If you take blood pressure medicine, the low blood pressure finding is one to raise once a label exists. Today there is no prescription to ask for: access runs through trials and a narrow Lilly early-access program that physicians must request.
What has not changed. Retatrutide is still investigational, and Lilly plans to file in Q1 2027. The retatrutide side effects page has the trial-by-trial tables.