Retatrutide vs Tirzepatide — research differences
Retatrutide and tirzepatide are both incretin-based research compounds investigated for metabolic dysregulation, but they differ in receptor targeting: tirzepatide (Eli Lilly's Mounjaro / Zepbound) is a dual agonist binding the GLP-1 and GIP receptors; retatrutide (LY-3437943) is a triple agonist that adds glucagon receptor activity to that mix. The added glucagon arm in retatrutide is hypothesised in the published TRIUMPH programme literature to drive larger reductions in body weight and hepatic fat in research subjects, with phase 2 trial reports showing ~24% mean body weight reduction at 48 weeks vs ~15-21% for tirzepatide in comparable trial designs. Tirzepatide is FDA-approved (since 2022); retatrutide is currently in phase 3.
Side-by-side
| Retatrutide 40 mg pen | tirzepatide-30mg-kit | |
|---|---|---|
| Receptor agonism | GLP-1 + GIP + glucagon | GLP-1 + GIP |
| Originator | Eli Lilly | Eli Lilly |
| Approval status | Phase 3 (TRIUMPH) | FDA approved (Mounjaro 2022, Zepbound 2023) |
| Half-life | ~6 days | ~5 days |
| Trial weight loss (48w) | ~24% mean | ~15–21% mean |
| Research dosing range | 0.5 – 12 mg weekly | 2.5 – 15 mg weekly |
| CAS number | 2381089-83-2 | 2023788-19-2 |
What to know
- ·Both compounds are once-weekly subcutaneous in published research protocols.
- ·The triple-agonist mechanism (retatrutide) is the major difference — glucagon receptor activity has been associated in the literature with hepatic fat reduction beyond what dual agonism alone produces.
- ·Tirzepatide has multi-year real-world data; retatrutide has only phase 2 and ongoing phase 3 trial data.
- ·Side-effect profiles are broadly similar in trial reports — gastrointestinal effects (nausea, transient) dominate in both.
- ·Both are research-use only on this catalogue. Neither is sold for human or veterinary administration.
Where the literature diverges
The most-cited literature distinction is the hepatic-fat outcome: in the SURPASS programme (tirzepatide), hepatic fat reductions were significant but secondary to body composition; in retatrutide phase 2 data the magnitude of liver-fat reduction was disproportionately large vs body weight loss, attributed in author commentary to the glucagon-receptor arm increasing hepatic lipid oxidation. This is the key reason retatrutide is being investigated specifically for MASH (metabolic-dysfunction-associated steatohepatitis) in addition to the obesity indication.
FAQ
Which is "stronger"?+
By the most-cited weight-loss endpoint at 48 weeks, retatrutide produces larger reductions in trial settings (~24% vs ~15-21%), though direct head-to-head trials don't yet exist — the comparison is across separate trial cohorts with different baselines and protocols. The added glucagon receptor activity in retatrutide is the mechanistic basis for the difference.
Why is one approved and the other not?+
Tirzepatide began clinical development in 2018; retatrutide is younger. Tirzepatide finished its phase 3 SURPASS programme and got FDA approval in 2022 (T2D) and 2023 (obesity). Retatrutide's TRIUMPH phase 3 programme was initiated in 2023 — completion and regulatory filing are expected 2026-2027.
Can I use them interchangeably?+
Both are research-use-only here. They are different molecules with different receptor profiles — published trial designs do not interchange them. Any cross-comparison protocol would be designed around the receptor-pharmacology differences, not framed as substitution.
This is a research-context comparison of compound mechanism and published trial outcomes. Not medical advice. Both compounds are research-use only when sold by Omega Grade — for in vitro laboratory investigation, not human or veterinary administration.
- ResearchRetatrutide 40 mg pen
Retatrutide is a triple agonist at the GLP-1, GIP, and glucagon receptors. The 40 mg pen is the highest-dose presentation in the Omega Grade catalogue
- ResearchRetatrutide 30 mg kit
Retatrutide 30 mg lyophilised vial kit — the mid-dose research presentation. Includes bacteriostatic water, syringes, and swabs.
- ResearchRetatrutide 10 mg kit
Retatrutide 10 mg lyophilised vial kit — entry-point research presentation. Includes bac water, syringes, swabs.
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