Everything discussed here is supplied strictly as a laboratory research material. None of these compounds is approved, intended or authorised for human consumption or therapeutic use by RS Bio Labs, and the trials and regulatory steps referenced describe other organisations' work. This article summarises publicly reported news for qualified researchers and is not medical or legal advice.
Where retatrutide stands today
Retatrutide is a once-weekly triple agonist acting on the GIP, GLP-1 and glucagon receptors. It is still investigational: no regulator has approved it. Our status explainer covers what that means in practice. What has changed in 2026 is the amount of late-stage data. According to Lilly's 23 July 2026 announcement, the company is completing the manufacturing and controls package needed for a Biologics License Application and plans to submit to the FDA in the first quarter of 2027.
TRIUMPH-1 (reported May 2026)
TRIUMPH-1 was the first of the big obesity readouts. As reported by AJMC, it enrolled roughly 2,300 adults and ran for 80 weeks, with average weight loss of 17.6% on 4 mg, 23.7% on 9 mg and 25.0% on 12 mg, against 3.9% on placebo. Press coverage also cited results of up to about 30% in a severe-obesity subgroup at longer follow-up. As with any headline figure, check which analysis it comes from (efficacy estimand versus treatment-regimen estimand) before comparing it with another trial.
TRIUMPH-2: obesity with type 2 diabetes
Announced on 23 July 2026, TRIUMPH-2 was an 80-week, randomised, double-blind, placebo-controlled trial in 1,152 adults with type 2 diabetes and obesity or overweight (baseline weight about 106 kg, baseline A1C 7.7%). Participants started at 2 mg weekly and stepped up every four weeks to their target dose. Lilly reported (efficacy estimand, 80 weeks):
| Arm | Body-weight change | A1C change |
|---|---|---|
| Retatrutide 4 mg | −12.7% | −1.4% |
| Retatrutide 9 mg | −19.1% | −1.6% |
| Retatrutide 12 mg | −20.8% | −1.5% |
| Placebo | −4.0% | −0.2% |
Lilly notes that the 4 mg weight result was a key secondary endpoint rather than the primary endpoint.
TRIUMPH-3: severe obesity with cardiovascular disease
TRIUMPH-3 enrolled 1,949 adults with Class 2 or 3 obesity and established cardiovascular disease (baseline weight about 111 kg). At 80 weeks, retatrutide produced −21.6% (9 mg) and −22.6% (12 mg) against −3.2% on placebo. Triglycerides fell by 37.0%, systolic blood pressure by 9.3 mmHg and hsCRP by 51.2% at the highest dose.
The cardiovascular event data are worth reading carefully, because they are easy to over-interpret. In the pre-specified in-study analysis of five-component major adverse cardiovascular events (MACE-5), the pooled retatrutide arms had 44 events against 52 on placebo (hazard ratio 0.82, 95% CI 0.55–1.22). The confidence interval crosses 1, so this is not a demonstrated reduction. For the narrower MACE-3 measure the in-study hazard ratio was 1.12 (95% CI 0.64–1.96), also inconclusive. The trial was designed to measure weight, not outcomes; dedicated cardiovascular-outcomes trials are separate.
Tolerability
As with other incretin-based compounds, the common adverse events were gastrointestinal. In TRIUMPH-2, diarrhoea affected 27–34% of retatrutide participants (13% on placebo) and nausea 14–28% (8% on placebo). Dysesthesia (abnormal skin sensations) was reported more often on retatrutide: 4.5–7.3% against 0.7% on placebo in TRIUMPH-2, and 6.4% against 1.3% in TRIUMPH-3. Discontinuation because of adverse events ranged from 3.8–11.6% across TRIUMPH-2 retatrutide arms (4.9% on placebo) and 9.8–13.5% in TRIUMPH-3 (4.8% on placebo). Higher doses were generally less well tolerated, which is one reason the dose-response picture matters as much as the top-line number.
What happens next
Lilly says it has the clinical data to support global submissions for obesity, knee osteoarthritis pain and obstructive sleep apnoea, and that further Phase 3 studies are ongoing in other conditions. Regulatory review will take time after a Q1 2027 filing, so retatrutide remains an investigational compound for the foreseeable future. For researchers, the practical points are the ones the data keep returning to: glucagon-receptor activity adds an energy-expenditure axis on top of GIP/GLP-1, the dose-response is steep, and tolerability and lean-mass questions are still open. See retatrutide vs tirzepatide and muscle preservation in the GLP-1 era for the comparison and the lean-mass angle.
Sources
- Eli Lilly press release, 23 July 2026: retatrutide successful in two additional Phase 3 obesity trials (TRIUMPH-2 and TRIUMPH-3 figures, submission timeline)
- AJMC, May 2026: retatrutide TRIUMPH-1 results
- The Pharmaceutical Journal: Phase III retatrutide study demonstrates 30% weight loss
Figures are as reported by the sponsor and the outlets above at the time of writing. Trial results are population averages from other organisations' studies and say nothing about the use of any product supplied by RS Bio Labs.
