Timeline · Updated October 28, 2026 · Sources checked October 19–28, 2026

Published May 6, 2026 · Updated October 28, 2026

Retatrutide timeline

Retatrutide is an investigational once-weekly GIP, GLP-1, and glucagon receptor agonist from Eli Lilly. It is not FDA approved. This timeline lists only milestones with a primary source.

June–August 2023: phase 2 results

Phase 2 results in obesity were published in the New England Journal of Medicine, with mean weight loss of 24.2% at 48 weeks on the 12 mg dose versus 2.1% on placebo.[1] A phase 2 trial in type 2 diabetes was published in The Lancet the same summer.[2]

December 11, 2025: first phase 3 obesity result (TRIUMPH-4)

Lilly reported that in 445 adults with obesity and knee osteoarthritis, retatrutide 12 mg produced 28.7% average weight loss at 68 weeks versus 2.1% on placebo, with knee pain scores falling 4.4 points versus 2.4.[5][6]

March 19, 2026: first phase 3 topline in type 2 diabetes

Lilly announced that TRANSCEND-T2D-1 met its primary and key secondary endpoints in adults with type 2 diabetes.[3]

May 21, 2026: TRIUMPH-1 topline

In the main obesity trial (adults without diabetes, 80 weeks), Lilly reported 28.3% average weight loss on 12 mg using its on-drug estimate. Dysesthesia (abnormal skin sensations) was reported in 12.5% on 12 mg versus 0.9% on placebo.[7]

June 2026: TRANSCEND-T2D-1 published; expanded access opens

The full trial appeared in The Lancet: HbA1c reductions of 1.69–1.94 points and weight reductions of 11.5–15.3% at 40 weeks, versus 0.81 points and 2.6% on placebo.[4] On June 5, Lilly listed a single-patient expanded-access program for adults with a BMI of 35 or more and at least two serious obesity-related complications who cannot join a trial.[10]

July 23, 2026: TRIUMPH-2 and TRIUMPH-3 toplines; filing planned for Q1 2027

Lilly reported 20.8% weight loss on 12 mg in people with type 2 diabetes (TRIUMPH-2) and 22.6% in people with severe obesity and heart disease (TRIUMPH-3), both at 80 weeks on its on-drug estimate. TRIUMPH-3 had 27 major heart events on retatrutide and 23 on placebo, too few to show benefit or harm. Lilly said it plans to submit retatrutide to the FDA in the first quarter of 2027.[8]

September 29, 2026: TRIUMPH-1 and TRIUMPH-2 published

Counting everyone randomized, TRIUMPH-1 in the New England Journal of Medicine reported 25.0% weight loss on 12 mg versus 3.9% on placebo among 2,339 adults, and TRIUMPH-2 in The Lancet reported 18.8% versus 5.1% among 1,152 adults with type 2 diabetes.[9][11]

October 2, 2026: FDA restates that retatrutide is a drug, not a biologic

FDA again took the position that retatrutide should be regulated as a drug rather than a biologic, part of an ongoing dispute with Lilly over which kind of application applies. It is not a rejection of the drug.[12]

October 21, 2026: sleep apnea results published

The New England Journal of Medicine published two Lilly-funded phase 3 sleep apnea trials run inside TRIUMPH-1 and TRIUMPH-2. In 243 adults with moderate-to-severe obstructive sleep apnea and no diabetes, breathing pauses and shallow-breathing events (the apnea-hypopnea index) fell by 31.7 to 34.3 an hour at 80 weeks on the two higher doses, the trial’s main comparison, versus 9.9 on placebo, from a starting average of about 59. In 448 adults with type 2 diabetes, they fell by 24.7 to 25.4 an hour, versus 10.3 on placebo, from a starting average of about 56. The paper reports that retatrutide lowered the index significantly more than placebo in both trials and that the most common side effects were gastrointestinal.[13] Neither trial compared retatrutide with Zepbound (tirzepatide), which the FDA approved for sleep apnea in December 2024. Lilly said in July that it has the data to support submissions for obesity, knee osteoarthritis pain and obstructive sleep apnea.[8] Our reading: these results do not change Lilly’s stated Q1 2027 filing plan, and the FDA has not reviewed them.

October 28, 2026: first head-to-head result, vs Ozempic

Lilly announced topline results from TRANSCEND-T2D-2, an open-label phase 3 trial in 1,298 adults with type 2 diabetes. At 80 weeks, retatrutide lowered A1C by 2.2 points on both doses versus 1.8 on Ozempic 2 mg, and weight by 19.5% (9 mg) and 20.9% (12 mg) versus 9.4%. Stopping because of side effects was 4.8% and 7.9% versus 2.7%. These are Lilly’s efficacy-estimand figures from a press release; the company says full results will be presented at a medical meeting and published in a peer-reviewed journal.[14] Lilly’s head-to-head trial against tirzepatide, TRIUMPH-5, is still ongoing. Our reading: this does not change the stated Q1 2027 filing plan. More in our TRANSCEND-T2D-2 teardown.

This page summarizes published research and regulatory documents. It is not medical advice and does not recommend starting, stopping, or changing any medication.