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A phase III trial found that adults with obesity and type 2 diabetes taking retatrutide lost an average of 11.9% to 18.8% of their body weight by week 80, depending on dose, compared with 5.1% on placebo. The investigational drug also lowered HbA1c, but gastrointestinal side effects were common and it has not been approved; Eli Lilly plans to submit data to the FDA in early 2027.
A phase III trial found that adults with obesity and type 2 diabetes taking investigational retatrutide lost an average of 11.9% to 18.8% of their body weight by week 80, compared with 5.1% among participants given placebo. The TRIUMPH-2 results also showed improved blood sugar measures, but retatrutide is not approved for use, and its longer-term risks and benefits remain under study.
TRIUMPH-2 enrolled 1,152 participants across 92 medical and research centers in eight countries. Participants received a once-weekly injection of retatrutide at a 4 mg, 9 mg or 12 mg dose, or placebo, alongside their existing diabetes treatment. In the trial’s treatment-regimen analysis at week 80, average weight loss was 11.9% with 4 mg, 16.8% with 9 mg and 18.8% with 12 mg. The placebo group lost an average of 5.1%.
The report also presented an efficacy analysis that assumes participants took the study drug as intended and accounts differently for events that affect treatment. On that measure, participants taking the highest dose lost 20.8% of their body weight. That figure should not be confused with the 18.8% treatment-regimen result, which reflects a different analysis approach.
Retatrutide was associated with lower HbA1c, a measure of average blood sugar. Mean changes from baseline ranged from a 1.38 to 1.50 percentage-point reduction across the three doses, compared with a 0.45-point reduction on placebo. Up to 40% of participants receiving retatrutide reached normoglycemia, defined in the report as HbA1c below 5.7%. Some measures of waist circumference, triglycerides, non-HDL cholesterol and high-sensitivity C-reactive protein also improved.
The most common adverse events were gastrointestinal symptoms, mainly nausea, diarrhea and constipation. Discontinuation due to those symptoms was reported in 0% to 2% of retatrutide groups and 1% of the placebo group. Overall, 3% to 11% of participants in the retatrutide groups stopped treatment because of adverse events, compared with 5% on placebo. Hypotension and dysesthesia occurred more often in retatrutide groups. Seven participants died during the trial; investigators judged the deaths unrelated to study treatment.
Weight Loss in Diabetes Treatment
The findings address a treatment challenge described by the investigators: people with type 2 diabetes tend to lose less weight than people without diabetes, including with medication or metabolic surgery. In TRIUMPH-2, the highest-dose treatment-regimen result was 18.8% average weight loss, while the separate efficacy analysis reached 20.8%. These results could make retatrutide relevant to future treatment options for people managing both obesity and diabetes, if regulators authorize it.
The trial assessed blood sugar alongside weight, reporting changes in both measures in participants with obesity and type 2 diabetes.
The report said social media attention had helped spur a gray market for unapproved retatrutide. Retatrutide remains investigational.
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How TRIUMPH-2 Was Conducted
TRIUMPH-2 was a double-blind, placebo-controlled phase III trial. Eligible participants had a body mass index of at least 27, an HbA1c between 6.5% and 10.5%, and type 2 diabetes treated with stable background glucose-lowering therapy for at least 90 days before screening. They also had a history of trying to lose weight through diet.
At the start of the study, average BMI was 38.2, average HbA1c was 7.71%, and median diabetes duration was 5.6 years. Participants could be using up to three oral glucose-lowering medicines. Retatrutide activates three hormone receptors—GIP, GLP-1 and glucagon—rather than targeting only one or two. Juan P. Frias, the trial presenter, said engaging these pathways may help explain the weight-loss results, but that explanation is a proposed mechanism, not a separate clinical outcome.
The investigators compared the findings with earlier trials of other medicines, but those were not direct comparisons within TRIUMPH-2. The source report cited average weight losses of 13.2% with high-dose semaglutide and 15.7% with tirzepatide in people with diabetes. It also noted a 28.3% weight loss in TRIUMPH-1, which tested retatrutide in people without diabetes. Different trial populations and designs mean these figures should not be treated as a head-to-head ranking.
“We know that people with type 2 diabetes lose less weight than people without diabetes.”
— Juan P. Frias, MD, of the Los Angeles Institute for Metabolic Research, presenting the TRIUMPH-2 results
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Limits of the Trial Evidence
TRIUMPH-2 did not include an active comparison drug, so it cannot determine whether retatrutide is more effective or better tolerated than another treatment in a direct trial. The investigators also did not collect body-composition data to determine how much weight loss came from fat versus lean mass.
The results cover 80 weeks of treatment. Although seven participants died, the trial investigators judged the deaths unrelated to the study interventions. That assessment does not remove the need for further safety monitoring and evidence.
Retatrutide remains investigational. The report does not provide a final FDA decision, an approved product label, or a confirmed availability date.
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FDA Review Planned for 2027
Eli Lilly said it plans to submit the retatrutide data to the U.S. Food and Drug Administration in early 2027. That is a planned submission, not an approval date; the FDA would need to review the application and supporting evidence before deciding whether the drug can be marketed.
The trial report notes that TRIUMPH-2 had no active comparator and that investigators did not collect body-composition data. The reported results remain evidence from a clinical trial of an unapproved medicine.
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Key Questions
How much weight did participants lose on retatrutide?
At week 80, average weight loss in the treatment-regimen analysis ranged from 11.9% with 4 mg to 18.8% with 12 mg. Participants given placebo lost an average of 5.1%. A separate efficacy analysis reported 20.8% average loss at the highest dose.
Did retatrutide improve blood sugar in the trial?
Yes. Mean HbA1c fell by 1.38 to 1.50 percentage points across the retatrutide doses, compared with a 0.45-point reduction on placebo. Up to 40% of retatrutide-treated participants reached the study’s definition of normoglycemia, HbA1c below 5.7%.
What side effects were reported?
Nausea, diarrhea and constipation were the most frequent adverse events. Hypotension and dysesthesia were also reported more often in retatrutide groups. The study report said treatment discontinuation due to gastrointestinal symptoms was low.
Is retatrutide approved?
No. Retatrutide is investigational and not approved. Eli Lilly said it plans to submit data to the FDA in early 2027; a planned submission does not guarantee approval.
Can the results be compared directly with other weight-loss drugs?
No. TRIUMPH-2 had no active comparator arm. Results from separate studies of semaglutide, tirzepatide or retatrutide in people without diabetes provide context, but differences in trial design and participants mean they are not head-to-head comparisons.
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