Retatrutide’s 18.8% Diabetes Loss Tests Lilly’s Dual Shot

Eli Lilly’s retatrutide cut body weight by 18.8% at its top dose in adults with type 2 diabetes and obesity. The 80-week TRIUMPH-2 trial, published Sept. 29, 2026, in The Lancet and presented at the European Association for the Study of Diabetes meeting in Milan, also lowered blood sugar and an inflammation marker.

The shot is not approved anywhere. It hits three gut-hormone receptors at once, including glucagon, the extra lever Lilly does not use in Zepbound. That third target is why people still call it the Godzilla of weight-loss drugs. The nickname does not match this diabetes population as cleanly as the company’s own table from people who did not have diabetes.

Retatrutide’s Diabetes Data Land in Milan

Investigators randomly assigned 1,152 adults to a weekly placebo shot or retatrutide at 4 mg, 9 mg, or 12 mg, on top of diet advice and activity guidance. The 18.8% mean weight loss at 12 mg is the journal’s treatment-regimen figure, which counts everyone who started, including people who later stopped. Placebo lost 5.1%. The 4 mg and 9 mg groups lost 11.9% and 16.8%.

Gaps versus placebo were 6.9, 11.8, and 13.8 percentage points, each with p under 0.0001. Lilly, which funded the trial, presented a second analysis that asks what would have happened if every volunteer had stayed on the assigned shot for the full 80 weeks. That on-treatment table is the one that produces the rounder “Godzilla” headlines.

THE TWO WAYS TRIUMPH-2 COUNTED WEIGHT

On that on-treatment read, the 12 mg group lost an average of 49.6 lbs, or 20.8%, on 12 mg from a starting weight of 234.6 lb (106.4 kg). People who began at a BMI of 35 or higher lost 60.8 lb, or 23.4%. By week 80, 59.5% of the 12 mg group no longer met the BMI cutoff for obesity. Those are the figures that travel as 50-pound headlines. They are not the figures the journal used as its primary weight result.

A Separate Trial Posted the 25% Loss

The same day, the New England Journal of Medicine published TRIUMPH-1, a larger phase 3 study in adults with obesity and no diabetes. In 2,339 people, the 12 mg dose produced a 25.0% loss without diabetes on the intention-to-treat analysis, against 3.9% on placebo. The 9 mg and 4 mg groups lost 23.7% and 17.6%.

That 25.0% result, not the diabetes paper, is the number that sits next to bariatric-surgery talk. A 2023 phase 2 trial led by Ania Jastreboff had already put 24.2% on the table at 48 weeks in people without diabetes, which is where the monster nickname took hold. People with type 2 diabetes usually lose less on this class of medicines. TRIUMPH-2 is the harder test, and 18.8% still beat the dual-agonist pattern in similar patients, but it is not the 25.0% figure.

Knee pain and sleep-apnea breathing pauses also improved in TRIUMPH-1 subgroups. Those extra labels are part of why Lilly says it has a package for obesity, knee osteoarthritis pain, and obstructive sleep apnea, not only for glucose.

What TRIUMPH-2 Enrolled and Measured

Screening ran from July 11, 2023, to Nov. 1, 2024, across 92 centres in eight countries: Argentina, Australia, Brazil, India, Mexico, Romania, Spain, and the United States. Of 2,047 people screened, 1,152 were randomized: 292 to 4 mg, 284 to 9 mg, 287 to 12 mg, and 289 to placebo. Mean age was 55.1. Women made up 48% of the group (554), men 52% (598), and 58% were White (672).

WHO WALKED INTO THE TRIAL

• Starting size: Mean BMI was 38.2 and mean weight was 234.6 lb, with a median 21 years of obesity.
• Diabetes history: Mean A1C was 7.71%, median diabetes duration was 5.6 years, and 92% already took at least one oral glucose-lowering drug.
• How the shot was started: Everyone on retatrutide began at 2 mg weekly and stepped up every four weeks to 4 mg, 9 mg, or 12 mg.
• Who finished: 84% completed the study drug (965 of 1,152). The TRIUMPH-2 trial registry record lists the study as completed on June 16, 2026.

Adults had to have a BMI of 27 or higher, A1C between 6.5% and 10.5%, stable diabetes treatment for at least 90 days, and at least one failed diet attempt. Shots were self-injected once a week. A nested sleep-apnea basket is still due at a later meeting.

The vast majority of people with type 2 diabetes are also living with obesity, and treating the two together has always been a challenge. In TRIUMPH-2, retatrutide reduced both weight and blood sugar substantially, with more than half of participants no longer qualifying as having obesity and up to 40% reaching an A1C in the normal range.

Juan P. Frías, M.D., Medical Director and Principal Investigator, Los Angeles Institute for Metabolic Research, in Lilly’s Sept. 29, 2026 statement

Frías is citing the on-treatment read: 59.5% of the 12 mg group left the obesity BMI range, and 40.0% of the 9 mg group reached an A1C under 5.7%.

The Extra Hormone Leaves a Skin Sensation

Retatrutide is a single weekly molecule that turns on receptors for GLP-1, GIP, and glucagon. Wegovy’s semaglutide mainly hits GLP-1. Tirzepatide, sold by Lilly as Mounjaro for diabetes and Zepbound for weight, hits GLP-1 and GIP. Glucagon is the add-on meant to raise energy use, not only cut appetite. TRIUMPH-2 did not publish a new resting-heart-rate table in the material released with the paper. It did log two problems that show up more with this molecule than with placebo: low blood pressure and dysesthesia, an abnormal skin feeling such as tingling or burning.

SIDE EFFECTS AT 80 WEEKS

• Diarrhea: 27% on 4 mg, 34% on 9 mg, and 34% on 12 mg, versus 13% on placebo.
• Nausea: 14%, 21%, and 28% versus 8%.
• Dysesthesia: 4%, 6%, and 7% versus 1% (Lilly’s on-treatment rates were 4.5%, 5.6%, and 7.3% versus 0.7%).
• Low blood pressure: 1%, 5%, and 6% versus under 1%.
• Stopping for side effects: Lilly counted 3.8%, 11.6%, and 7.7% versus 4.9% on placebo. The 9 mg arm, not 12 mg, had the highest stop rate.

Lilly also listed constipation (up to 16.8%), vomiting (up to 15.7%), and reduced appetite (up to 17.1%). Most gut events were mild or moderate and eased during treatment. Seven deaths occurred, two on 4 mg, three on 9 mg, one on 12 mg, and one on placebo. Investigators judged none related to the shot.

Dysesthesia is the signal people who track this pipeline keep circling, because tirzepatide trials did not put it on the map in the same way. It was dose-linked and still uncommon at 12 mg, but it is not a standard GLP-1 complaint. If Lilly wants a premium over Zepbound, this is one of the extras a reviewer, a payer, or a patient will ask about.

Zepbound Stays Lilly’s Shot of Today

Lilly already sells tirzepatide and, per the same statement, orforglipron as Foundayo, a daily pill. Retatrutide would be a third branded option in the same franchise, a weekly injection that has to justify itself against a dual agonist the company is still scaling. There is no published head-to-head of retatrutide versus tirzepatide. A TRIUMPH-5 comparison is still outstanding, so every cross-trial chart is an indirect one.

Kenneth Custer, president of Lilly Cardiometabolic Health, said TRIUMPH-2 shows “substantial weight loss, A1C reduction and improvements across other critical cardiovascular risk factors,” and that the company believes retatrutide “could become an important option for people living with type 2 diabetes and obesity.” Lilly plans a biologics license application to the U.S. Food and Drug Administration in the first quarter of 2027. The delay is manufacturing and quality data, not a missing efficacy trial. Until then the medicine cannot be legally sold or marketed.

That calendar is the practical point for clinics. Patients who want a weekly shot in 2026 still get semaglutide or tirzepatide. Retatrutide’s extra pounds in diabetes are real on both analyses, and they still sit behind a filing that has not been submitted. A dual agonist already in the bag is easier to prescribe than a triple that exists as a Lancet paper and a 2027 slot.

A1C Dropped Most on the 9 mg Dose

Weight kept climbing with dose. Blood sugar did not. From a 7.7% starting A1C on Lilly’s table, 9 mg lowered A1C by 1.6 percentage points, 12 mg by 1.5, and 4 mg by 1.4, versus 0.2 on placebo. Shares reaching 6.5% or lower were 73.1%, 79.2%, and 79.0% versus 26.3% on placebo. Shares reaching a normal A1C under 5.7% were 28.4%, 40.0%, and 39.3% versus 4.4%.

The middle dose was the glucose peak. That matters if the marketing story is “more receptors, more of everything.” On glucose, 12 mg did not beat 9 mg. On weight it did. Clinicians who care first about A1C may not need the top rung, which also brought more nausea (28%) and more dysesthesia (7%).

TWELVE MG HEART AND FAT MARKERS

• Triglycerides: down 39.5% at the highest dose.
• Non-HDL cholesterol: down 19.6%.
• Systolic blood pressure: down 10.8 mmHg.
• Waist and inflammation: waist down 6.7 in (16.9 cm); high-sensitivity C-reactive protein down 58.3%.

Those are risk markers, not heart-attack counts. Lilly has a longer outcomes study still running. TRIUMPH-2 was built to measure weight and glucose, and it did both. It does not settle whether glucagon’s extra burn is a net win for arteries over a decade.

How Retatrutide Compares With Shots Already Sold

Indirect comparisons are messy because trials differ in length, diet support, and who got in. The pattern still holds: people without diabetes lose more than people with it, and each added receptor has so far tracked with a higher average loss in separate studies. Semaglutide’s obesity-with-diabetes trials clustered near 10%. Tirzepatide’s similar studies clustered higher, still below retatrutide’s 18.8% ITT and 20.8% on-treatment at 12 mg. No regulator has said the triple is better than the dual in the same patient at the same time.

THE RETATRUTIDE CLOCK SO FAR

1. 2023: Phase 2 in people without diabetes reports 24.2% mean loss at 48 weeks on 12 mg, the result that stuck the Godzilla label to the molecule.
2. July 11, 2023: TRIUMPH-2 screening opens. The wider TRIUMPH program later enrolls more than 5,800 people.
3. July 23, 2026: Lilly releases TRIUMPH-2 and TRIUMPH-3 toplines, including the 20.8% on-treatment diabetes figure, and points to a first-quarter 2027 U.S. filing.
4. Sept. 29, 2026: The Lancet publishes the diabetes paper’s 18.8% ITT result; NEJM publishes the 25.0% no-diabetes result; both land at the Milan diabetes meeting.

Among people who stay close to this pipeline, the diabetes paper did not rewrite the rank order the way TRIUMPH-1 did. The 25.0% no-diabetes figure still carries the nickname. TRIUMPH-2 is the test that matters for the millions of adults who have both obesity and type 2 diabetes, and its primary number is 18.8%, with a gut-side-effect load and a skin signal Zepbound did not make famous.

Lilly now has a peer-reviewed diabetes file, a same-day obesity file at 25.0%, and a 2027 appointment with the FDA. The dual shot that already sits in its bag is still the one a patient can pick up this year.

Frequently Asked Questions

How Is Retatrutide Taken in the Trials?

It is a once-weekly shot that volunteers injected themselves. In TRIUMPH-2 everyone on the drug started at 2 mg and increased every four weeks, with a 2 mg step to reach 4 mg, extra 4 mg and 6 mg steps to reach 9 mg, and a further 9 mg step to reach 12 mg. The treatment period was 80 weeks, then four weeks of follow-up off the assigned shot.

Is Retatrutide Approved by the FDA?

No. Lilly says it cannot be legally sold or marketed for human use. The company plans to submit a biologics license application in the first quarter of 2027, after it finishes the manufacturing package, and no regulator has cleared it for obesity or diabetes.

How Does TRIUMPH-1 Differ From TRIUMPH-2?

TRIUMPH-1 enrolled 2,339 adults with obesity and no diabetes and reported 25.0% mean weight loss at 12 mg over 80 weeks, plus less knee pain and fewer sleep-apnea events in predefined subgroups. TRIUMPH-2 enrolled 1,152 adults who already had type 2 diabetes and obesity or overweight, and its primary published weight result at the same dose was 18.8%.

What Is Dysesthesia on Retatrutide?

Dysesthesia means an odd skin sensation, such as tingling, burning, or pain to light touch. In TRIUMPH-2 it occurred in 4%, 6%, and 7% of the 4 mg, 9 mg, and 12 mg groups versus 1% on placebo, and Lilly described most cases as mild to moderate and often resolving on treatment. It is the adverse event that most clearly separates this triple agonist from dual GIP/GLP-1 shots in the public data set.

Did the Milan Meeting Also Look at Pregnancy?

A separate review in The Lancet Obstetrics, Gynaecology & Women’s Health, also tied to the Milan meeting, pooled prior studies of GLP-1 receptor agonists in women with diabetes and did not find a clear rise in several adverse pregnancy outcomes. The authors still said large evidence gaps remain, backed pre-pregnancy metabolic treatment, and stressed stopping these drugs before a planned pregnancy. Retatrutide itself was not the subject of that review.

Disclaimer: This article is news reporting on clinical trial results and company statements. It is for information only and is not medical advice, a treatment recommendation, or an instruction to start, stop, or switch any medicine. Retatrutide is investigational and is not approved for weight loss or diabetes. Readers should talk with a licensed physician or endocrinologist before changing diabetes or weight-loss treatment. Trial figures, side-effect rates, and Lilly’s filing plan reflect the Lancet paper, the NEJM companion trial, the trial registry, and Lilly’s Sept. 29, 2026 statement, and those facts can change as regulators review the file.