For nearly two years, one of the biggest unanswered questions surrounding retatrutide wasn’t how much weight people would lose. We already had a pretty good idea of that from the Phase 2 data. The bigger question was what would happen once Lilly reached the FDA. Would retatrutide be reviewed as a traditional drug, or would it ultimately be regulated as a biologic? Today, Lilly appears to have answered that question, and notably, it chose to make the answer one of the very first things investors saw.
Before discussing a single efficacy result, Lilly highlighted that it plans to submit a Biologics License Application (BLA) to the FDA in the first quarter of 2027. That may sound like regulatory jargon, but for readers of On the Pen, it represents the latest chapter in a story we’ve been following since the fall of 2024, when Lilly and the FDA found themselves at odds over how retatrutide should be classified. The company ultimately challenged the agency’s position in court, and while the litigation did not definitively settle the issue, it left the industry waiting for the FDA’s next move. Lilly’s decision to publicly announce a BLA filing is the strongest indication yet that the company believes the biologics pathway is now the appropriate regulatory route.
That does not mean the FDA has formally declared retatrutide a biologic. Lilly has not yet submitted its application, the FDA has not yet accepted it for review, and no approval has been granted. However, companies are exceptionally careful about describing future regulatory submissions. Announcing plans to file a Biologics License Application is not language chosen lightly. At a minimum, it suggests Lilly has a high degree of confidence that the agency will accept retatrutide through the biologics pathway, something that was far from certain when we first began covering this story almost two years ago.
The regulatory update came alongside the completion of Lilly’s pivotal Phase 3 program. In TRIUMPH-2, adults living with obesity or overweight and type 2 diabetes lost up to 20.8% of their body weight, an average of 49.6 pounds over 80 weeks, while also lowering A1C by as much as 1.6 percentage points. That population has historically been among the most difficult to treat from a weight loss perspective, making the results particularly noteworthy.
TRIUMPH-3 evaluated adults with severe obesity and established cardiovascular disease, with or without type 2 diabetes. Participants receiving the highest dose of retatrutide lost an average of 22.6% of their body weight, or 55.8 pounds, over 80 weeks. Lilly also reported meaningful improvements across several cardiometabolic risk factors, including triglycerides, systolic blood pressure, waist circumference, non-HDL cholesterol, and high-sensitivity C-reactive protein, reinforcing the broad metabolic effects that have characterized retatrutide throughout development.
One point deserves careful interpretation. Lilly reported fewer major adverse cardiovascular events in the retatrutide group than in the placebo group, but the study was not powered to demonstrate superiority for cardiovascular outcomes, and the confidence intervals crossed one. In other words, while the numerical trend is encouraging, these data cannot be interpreted as evidence that retatrutide reduces cardiovascular events. That question will ultimately be answered by Lilly’s dedicated cardiovascular outcomes trial.
Today’s announcement therefore marks two milestones at once. Scientifically, Lilly has now completed the Phase 3 efficacy package needed to support global regulatory submissions. From a regulatory perspective, the company has publicly committed to pursuing approval through a Biologics License Application, something that appeared far from certain when this dispute first emerged in 2024. The FDA will still have the final say after Lilly submits its application in the first quarter of 2027, but for the first time since this regulatory fight began, it appears that Lilly believes the path forward has finally become clear.
