Retatrutide: Triple Agonist Shows Landmark Weight Loss in Phase 3

What's new with retatrutide?

Since we last covered retatrutide, the pipeline drug has continued to impress. Here's a summary of the latest Phase 3 data from 2025 and 2026.

TRIUMPH-1: The pivotal obesity trial (May 2026)

Lilly announced positive topline results from TRIUMPH-1, a Phase 3 trial evaluating retatrutide in adults with obesity or overweight with at least one weight-related condition, but without diabetes. All three doses tested; 4mg, 9mg and 12mg met the primary and key secondary endpoints at 80 weeks.

The trial involved 2,339 participants in a randomised, double-blind, placebo-controlled study. Retatrutide demonstrated an average weight loss of 28.3% at 80 weeks, rising to 30.3% at 104 weeks figures that rival bariatric surgery outcomes.

TRIUMPH-4: Obesity + knee osteoarthritis (December 2025)

In the TRIUMPH-4 trial, the highest dose of retatrutide led to an average weight loss of 28.7%, alongside substantial improvements in pain and physical function for patients with knee osteoarthritis. The drug also reduced cardiovascular risk markers including non-HDL cholesterol and systolic blood pressure. Average weight loss reached up to 71.2 lbs in this trial.

Type 2 diabetes: TRANSCEND-T2D-1 (March 2026)

Lilly also reported positive topline results from TRANSCEND-T2D-1, evaluating retatrutide in adults with type 2 diabetes with inadequate glycemic control through diet and exercise alone. The drug met the primary and all key secondary endpoints, delivering superior A1C reduction and weight loss at 40 weeks compared to placebo.

What is retatrutide?

Retatrutide is an investigational once-weekly triple hormone receptor agonist, a single molecule that activates the body's receptors for GIP, GLP-1, and glucagon. It is not yet approved and remains available only within clinical trials.

What's next?

Seven additional Phase 3 trials are expected to complete in 2026, covering sleep apnoea, chronic low back pain, cardiovascular outcomes, liver disease and more.

Please note: Retatrutide is not yet licensed or available as a treatment. For laboratory research use only. Not for human or veterinary use.

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