What the 2026 Retatrutide Trial Data Actually Shows

June 6, 2026, brought the busiest single day yet for retatrutide's clinical program. Eli Lilly published the TRANSCEND-T2D-1 phase 3 results in The Lancet. The company presented the same data at the American Diabetes Association's 86th Scientific Sessions in New Orleans. Those retatrutide 2026 trial results also included TRIUMPH-1, an 80-week obesity trial with nested basket trials in knee osteoarthritis and obstructive sleep apnea. One boundary has to stay fixed before any number lands. These are results for retatrutide, an investigational drug candidate in pharmaceutical development. They are not results for any research compound that Longevia supplies. Every figure below names its trial, so the two never blur together. That discipline, naming the trial behind every number, is what separates reporting from marketing.

What is retatrutide, and what is TRANSCEND-T2D-1?

Retatrutide is an investigational triple hormone receptor agonist that activates the GIP, GLP-1, and glucagon receptors [1]. TRANSCEND-T2D-1 is its phase 3 trial in type 2 diabetes, published in The Lancet and presented at ADA 2026 [1].

Eli Lilly and Company is developing the molecule, which carries the development code LY3437943 [1]. Most approved incretin medicines act on one or two of these pathways. Retatrutide is designed to engage all three at once, which is what makes it a triple agonist. In the trials, investigators tested it as a once-weekly injection across several dose levels [1]. For background on how these receptor combinations work, see our overview of triple receptor agonist mechanisms.

The retatrutide TRANSCEND-T2D-1 trial tested the candidate in adults whose type 2 diabetes was not controlled by diet and exercise alone [1]. Forty weeks at 48 sites across the United States, Mexico, and India made up the trial's footprint [1]. It randomized 537 participants to one of three retatrutide doses or to placebo [1]. Results appeared online in The Lancet on June 6, 2026, with presentation the same day at the ADA Scientific Sessions [1]. That publication makes TRANSCEND-T2D-1 the program's first fully peer-reviewed phase 3 readout [1]. And the framing holds here too: this was a trial of a pharmaceutical candidate, entirely separate from any research compound.

Screening ran from April 2024 to April 2025, and 930 people were screened to randomize the final 537 [1]. Entry required an HbA1c between 7.0 and 9.5 percent and a body mass index of at least 23 [1]. Nobody had used another glucose-lowering medicine in the 90 days before screening [1]. That entry filter matters, because it defines exactly who these results describe. The Lancet paper describes TRANSCEND-T2D-1 as the first phase 3 trial of retatrutide in type 2 diabetes [1].

What did TRANSCEND-T2D-1 actually report?

At 40 weeks, retatrutide lowered HbA1c by up to 1.94 percentage points and body weight by 15.3 percent on the highest tested dose [1]. Both results beat placebo by a wide margin, and Lilly noted the weight loss had not yet plateaued at the final visit [2].

The primary endpoint was change in HbA1c from baseline to week 40 [1]. Percentage change in body weight at week 40 served as a key secondary endpoint [1]. Across the three dose arms, HbA1c fell 1.69, 1.86, and 1.94 points, against 0.81 points for placebo [1]. The estimated differences versus placebo were 0.88, 1.04, and 1.12 points, each with a p-value below 0.0001 [1]. Body weight dropped 11.5, 13.9, and 15.3 percent on retatrutide, compared with 2.6 percent on placebo [1]. Lilly's own summary used a different statistical estimand and reported up to 2.0 percent A1C reduction and 16.8 percent weight loss [2]. Up to 46 percent of participants on the highest dose reached an A1C below 5.7 percent, per that summary [2].

Participants averaged 48.8 years old, with a mean HbA1c of 7.9 percent and mean diabetes duration of 2.5 years [1]. Mean body mass index sat at 35.8, and 55 percent of participants were women [1]. Side effects were mostly mild to moderate gastrointestinal events, the familiar pattern for this drug class [1]. Between 2 and 5 percent of retatrutide recipients stopped treatment because of adverse events, versus none on placebo [1]. No severe hypoglycemia occurred, and the two deaths in the trial were judged unrelated to the study drug [1].

Forty weeks is a short window for a chronic disease. The trial enrolled people with early, diet-and-exercise-only diabetes, so the findings do not automatically extend to long-standing or insulin-treated disease [1]. It compared retatrutide against placebo rather than against an approved active medicine [1]. Cardiovascular outcomes were not part of this trial, which leaves the biggest long-term question open. All of this describes the drug candidate's trial, not any research material; the distinction from the opening still applies. The paper calls the population "early type 2 diabetes," which is worth quoting exactly [1].

What is TRIUMPH-1, and why did it study osteoarthritis and sleep apnea?

Eighty weeks, 2,339 participants, and two nested baskets: that is TRIUMPH-1, the phase 3 obesity trial of retatrutide [3]. It tested the drug candidate in knee osteoarthritis and obstructive sleep apnea because both conditions track closely with excess body weight [3].

The retatrutide TRIUMPH-1 program enrolled 2,339 adults with obesity, or overweight plus a weight-related comorbidity, and no type 2 diabetes [2]. Participants were randomized evenly to retatrutide 4 mg, 9 mg, 12 mg, or placebo [3]. The trial is registered on ClinicalTrials.gov as NCT05929066 [3]. Two prespecified subgroups, the basket trials, carried their own primary endpoints on top of the weight-loss core [3]. The osteoarthritis basket measured change in the WOMAC pain subscale from baseline to week 80 [3]. For sleep apnea, the basket tracked change in the apnea-hypopnea index over the same period [3]. A design paper by Giblin and colleagues laid out this structure in Diabetes, Obesity and Metabolism in 2026 [3]. In the master trial itself, Lilly reported weight loss of up to 28.3 percent, or 70.3 pounds, at 80 weeks [2].

Obesity multiplies the load on knee joints and narrows the upper airway during sleep. That shared root is why Lilly built these baskets into an obesity trial rather than running separate programs first [3]. The osteoarthritis basket enrolled 574 participants, and the sleep apnea basket enrolled 243 with moderate-to-severe disease [6]. Both read out at the ADA 2026 Scientific Sessions, alongside the TRANSCEND-T2D-1 publication [2]. A separate dedicated knee-osteoarthritis trial called TRIUMPH-4 reported its own figures, so its numbers should not be mixed with these basket results.

What did the knee osteoarthritis basket trial report?

Lilly reported WOMAC pain scores down up to 4.3 points, or 73.1 percent, from a baseline of 6.0 [2]. The company presented these figures at ADA 2026, and no peer-reviewed journal publication of the basket trial exists yet [2].

The retatrutide osteoarthritis trial enrolled 574 adults with obesity and knee osteoarthritis pain [6]. WOMAC, the Western Ontario and McMaster Universities Osteoarthritis Index, is the standard pain scale in knee-osteoarthritis research [3]. Pain was the basket's primary endpoint, measured as change from baseline to week 80 [3]. A 4.3-point drop from 6.0 leaves little room on the scale, which is why the percentage looks so large. Lilly reported the numbers on the efficacy estimand, a statistical approach that counts participants as if they stayed on treatment [2]. The release did not say whether the figures were adjusted for the placebo group, nor which dose arm produced the maximum [2]. All participants also met the master trial's obesity criteria, so this was an obesity population with knee pain, not a general osteoarthritis population.

Eighty weeks is long for an obesity trial, yet still short against a lifelong joint condition. Everyone in the basket had obesity, so the pain relief cannot be separated from the weight loss on these data alone. Company-reported topline figures deserve more caution than peer-reviewed results, because independent review has not tested them. Independent researchers will want the full peer-reviewed paper before treating these figures as settled. Until then, the honest label for these numbers is company-reported, not confirmed. The design paper set the basket's primary endpoint as change in WOMAC pain from baseline to week 80 [3].

What did the sleep apnea basket trial report?

A drop of up to 36.1 events per hour in the apnea-hypopnea index: that was Lilly's headline number for the sleep apnea basket [2]. That is a 60.6 percent reduction from a baseline of 58.6, reported at ADA 2026 [2]. As with the osteoarthritis figures, these are company-reported ADA 2026 data, not a peer-reviewed publication [2].

The retatrutide sleep apnea trial enrolled 243 adults with obesity and moderate-to-severe obstructive sleep apnea [6]. This index counts how many times breathing pauses or shallows each hour of sleep. A baseline of 58.6 events per hour sits deep in severe territory, so the absolute drop is the striking part. The release again left open whether the reduction was placebo-adjusted and which dose produced the maximum [2]. Weight loss almost certainly contributed, since the basket sat inside an obesity trial, but the data do not split the effect. For context, the same release put the master trial's weight loss at up to 28.3 percent [2]. That frames how much body weight changed underneath these apnea numbers. The basket's moderate-to-severe entry bar means the findings say nothing about mild sleep apnea.

Sleep apnea trials usually track daytime sleepiness and oxygen levels alongside the index. The topline release did not report those secondary measures. Eighty weeks gives a longer view than most apnea drug trials, which is a genuine strength of the design [3]. Still, company-reported numbers call for the same caution as the osteoarthritis basket until peer review lands. Future peer-reviewed publication should also clarify how much of the effect persists independent of weight change.

Here are the three 2026 readouts side by side:

How does this fit into retatrutide's broader development timeline?

The 2026 phase 3 results cap a program that began with two phase 2 trials in 2023. Phase 3 is a step toward possible regulatory review, not the same thing as approval.

Jastreboff and colleagues published the phase 2 obesity trial in the New England Journal of Medicine in August 2023 [4]. Over 48 weeks, the 12 mg dose cut body weight by 24.2 percent, against 2.1 percent for placebo [4]. That result put retatrutide ahead of anything the class had shown at the time. The trial lasted 48 weeks and tested several once-weekly doses against placebo [4].

Rosenstock and colleagues published the phase 2 diabetes trial in The Lancet the same month [5]. The trial compared retatrutide against both placebo and dulaglutide 1.5 mg in 281 participants [5]. On 12 mg, HbA1c fell 2.02 percent at 24 weeks and weight fell 16.9 percent at 36 weeks [5]. The diabetes trial ran in the United States and tested several doses, which was unusual for the stage [5]. Together, the two phase 2 trials set the dose range that phase 3 then carried forward.

The arc is straightforward: strong phase 2 signals, then larger and longer phase 3 trials in 2024 through 2026. Lilly has said it plans to file for regulatory review in the first quarter of 2027 [7]. The planned filing is a biologics license application, covering obesity, sleep apnea, and knee-osteoarthritis pain [7]. A filing starts the review clock; it does not guarantee approval, and retatrutide remains investigational today [7]. That status matters for how every number in this article should be read. The retatrutide phase 3 results therefore rest on a phase 2 base that already showed the dose-response pattern.

What should a researcher take from the retatrutide 2026 trial results, beyond the headlines?

Here is the honest summary: real phase 3 data now exists for several endpoints, with named trials, real numbers, and stated populations. None of it describes Longevia's GLP-3 (Rt) research compound, which is a separate material for laboratory use.

TRANSCEND-T2D-1 is the strongest piece, with a peer-reviewed publication and a placebo-controlled design [1]. The TRIUMPH-1 basket figures are real company-reported data, but they await peer review and lack published placebo-adjusted detail [2]. Headlines that drop the trial name or the estimand are doing the reader no favors. Always check which trial produced a number before quoting it, ideally against the registry record.

Phase 2 history shows the dose-response pattern was visible years before phase 3 confirmed it [4] [5]. That discipline, naming the trial every time, is the whole method of this article. For readers following GLP-3 triple agonist news, the method is simple: check the trial name first.

The next hard data point is the planned regulatory filing in early 2027 [7]. Peer-reviewed publication of the TRIUMPH-1 baskets would settle the open questions about placebo adjustment. Until then, treat the 2026 readouts as promising phase 3 signals with the usual phase 3 caveats. Full stop. Anyone tracking retatrutide latest research should start with the primary sources listed below. Researchers comparing incretin programs can read our research comparison of GLP-3 and tirzepatide for context.

Where does Longevia's GLP-3 (Rt) research material fit into this?

Longevia supplies GLP-3 (Rt) as a research compound related to retatrutide. Every batch is independently tested by HPLC and LC-MS, and lot-specific Certificates of Analysis are published in the COA Library. The COA Library lets researchers verify each lot's test results before ordering. It is a laboratory research material, and nothing more. That documentation is the entire basis on which a research material should be judged. Supply is strictly for laboratory research use. For researchers working with triple-agonist chemistry, our GLP-3 (Rt) research guide covers the compound's research context.