The Basics
Retatrutide (developmental code: LY3437943) is an investigational once-weekly injectable drug developed by Eli Lilly and Company. It belongs to a class of drugs called incretin-based therapies, but it takes this concept significantly further than anything currently on the market.
Where drugs like semaglutide (Ozempic, Wegovy) target a single hormone receptor — GLP-1 — and tirzepatide (Mounjaro, Zepbound) targets two (GLP-1 and GIP), retatrutide simultaneously activates three different receptors: GLP-1, GIP, and glucagon. This is why it is described as a triple agonist or triple receptor agonist.
This triple mechanism is believed to produce significantly more powerful metabolic effects than single or dual agonists, explaining why early clinical trial data has shown weight loss outcomes that surpassed expectations.
Key fact: In a Phase 2 trial published in the New England Journal of Medicine, participants taking the highest dose of retatrutide lost an average of 24.2% of their body weight over 48 weeks — a figure that approaches the outcomes typically seen with bariatric surgery.
Who Is It Being Developed For?
Retatrutide is being investigated across several metabolic conditions:
Obesity (BMI ≥ 30, or ≥ 27 with weight-related conditions)
This is the primary indication. The Phase 2 obesity trial demonstrated dramatic weight reduction across all doses tested. Phase 3 trials are now ongoing in a broader population.
Type 2 Diabetes
Separate Phase 2 trials evaluated retatrutide in patients with type 2 diabetes, where it showed strong glycemic control in addition to weight loss benefits.
Non-Alcoholic Fatty Liver Disease (MASH/NAFLD)
The glucagon receptor component of retatrutide is believed to directly target fat accumulation in the liver, making it a promising candidate for metabolic-associated steatohepatitis (MASH) — a condition with limited treatment options.
Obstructive Sleep Apnea
Eli Lilly has also initiated trials examining retatrutide's potential in obesity-related sleep apnea, following similar trial designs to those that led to tirzepatide's approval for this condition.
How Does It Compare to Existing Drugs?
The table below compares retatrutide to the leading approved GLP-1 and dual agonist medications currently on the market:
| Drug | Brand Name | Targets | Avg. Weight Loss | Status |
|---|---|---|---|---|
| Semaglutide | Wegovy / Ozempic | GLP-1 | ~15% | FDA Approved |
| Tirzepatide | Zepbound / Mounjaro | GLP-1, GIP | ~20–22% | FDA Approved |
| Retatrutide | TBD (LY3437943) | GLP-1, GIP, Glucagon | ~24% | Phase 3 Trials |
It is important to note that cross-trial comparisons should be interpreted with caution, as trial designs, populations, and durations differ. However, the directional trend is clear: adding the glucagon receptor to the combination appears to produce additional metabolic benefit.
Is Retatrutide Available?
No. As of 2025, retatrutide is not approved by the FDA or any other regulatory body and is not available to the public. It can only be accessed through participation in Eli Lilly's clinical trial program.
If Phase 3 data is positive and a New Drug Application (NDA) is submitted to the FDA, the earliest realistic timeline for potential approval would be 2026 or 2027. Approval timelines are never guaranteed and depend on regulatory review outcomes.