Retatrutide vs Semaglutide: First Head-to-Head Phase 3 Data

Clinical Trial Tracker · Reviewed by Thomas Okafor, PhD · Published October 31, 2026

Semaglutide, the active ingredient in Ozempic and Wegovy, has been the benchmark every newer metabolic drug gets measured against. Retatrutide vs semaglutide had only been compared across separate trials until now. TRANSCEND-T2D-2 put them in the same study, with people randomized to one or the other [1][2].

The trial at a glance

What Lilly reported

The primary goal was to show the higher retatrutide dose was at least as good as semaglutide at lowering A1C, a three-month average of blood sugar. Lilly reported it was superior [1][2]:

• A1C: about 2.2 points lower with both retatrutide doses, against 1.8 points with semaglutide.
• Weight: 19.5% and 20.9% average loss with the two retatrutide doses, against 9.4% with semaglutide.
• Other markers: Lilly described greater improvements in non-HDL cholesterol, triglycerides and systolic blood pressure, without giving figures.
• Side effects: mostly gastrointestinal. Diarrhea occurred in about 28% and 33% of the retatrutide groups, against 26% with semaglutide.

Reading the topline carefully

Three caveats shape what these numbers can show. The figures come from a company press release; peer-reviewed publication, with full safety tables, is still to come. The design was open-label, so participants and investigators knew which drug was given. And this trial enrolled people with type 2 diabetes, who typically lose less weight on these drugs than people without diabetes.

Even so, a doubling of weight loss against the current benchmark, in a direct comparison, is the clearest signal yet of where retatrutide stands in the field. An FDA filing for retatrutide is planned for the first quarter of 2027, according to Lilly. Our report on retatrutide’s sleep apnea trials covers the rest of the program, and our semaglutide guide covers the comparator.

Why the trial drug and online “retatrutide” differ

The same week, a CBS News investigation showed what can be sold under the name. A correspondent bought two “retatrutide” products online and one from a corner store in Brooklyn, and University of Iowa researcher Jason Galpin analyzed them [3]. The online samples were consistent with a basic reference standard Galpin made for retatrutide, which isn’t the same as the drug used in Lilly’s trials. Of the corner-store vial, Galpin said, “It does not look anything like a peptide” [3].

The trial figures describe Lilly’s manufactured drug under trial conditions. They say nothing about products sold outside approved channels, which we covered in our report on unapproved retatrutide sold online.

We cover company trial data here to inform readers; it shouldn’t stand in for a clinician’s advice. Retatrutide remains an investigational drug.