News · Publication · November 4, 2025
Extension data from the Phase 2 obesity trial, presented at ObesityWeek 2025
A presentation at ObesityWeek 2025 included extended follow-up data from retatrutide's Phase 2 obesity trial, with weight-loss curves continuing to trend downward in extension cohorts beyond the original study period.
What was presented
The ObesityWeek presentation extended the follow-up of the Phase 2 obesity trial originally published in the New England Journal of Medicine in June 2023. In that trial — 338 adults with obesity, treated for 48 weeks — the 12 mg dose produced an average 24.2% weight loss, the largest magnitude reported for a pharmacologic agent in a published obesity trial at the time.
The new data cover extension cohorts that remained on treatment past the original endpoint. The headline observation: weight-loss curves continued to trend downward in the extension period, rather than flattening.
Why the plateau question matters
Most weight-loss drugs reach a plateau between 60 and 72 weeks. The original Phase 2 curves were still trending down at the 48-week trial end, which left an open question: how much further does retatrutide go, and where does it level off?
The extension data push that observation window further out and are directionally consistent with the original curves — weight loss continued accumulating rather than plateauing at week 48. That supports the case that retatrutide's full effect was not captured by the original 48-week endpoint.
The definitive answer comes from Phase 3: TRIUMPH-1 runs 76 weeks, which will be the first opportunity to characterize where retatrutide plateaus and at what magnitude. See weight-loss results in detail for the full Phase 2 breakdown by dose and timepoint.
Caveats worth keeping
- Extension cohorts are subsets. Participants who remain in an extension phase are typically those tolerating and responding to treatment, which can bias extended curves upward relative to the full randomized population.
- Conference data precede peer review. ObesityWeek presentations are not peer-reviewed publications; numbers and analyses can be refined before journal publication.
- Phase 2 scale is limited. The original trial enrolled 338 participants. The ~2,300-participant TRIUMPH-1 trial is the dataset that will set expectations.
Retatrutide remains investigational; no regulator has approved it, and extension data from a completed Phase 2 trial do not change that status.