Tirzepatide (brand name Mounjaro®/Zepbound®, Eli Lilly) is a dual GIP/GLP-1 agonist. The peptide simultaneously activates receptors for glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) — a compound class referred to as a “twincretin”.
Mechanism of Action
- GLP-1 agonism: Stimulates insulin release, inhibits glucagon release, delays gastric emptying. Suppresses appetite and regulates blood sugar.
- GIP agonism: Enhances the insulinotropic response, promotes fat oxidation and improves insulin sensitivity in adipose tissue and liver. The GIP component also mitigates unwanted GLP-1 effects such as nausea.
The combination of both pathways produces a synergistic effect beyond that of GLP-1 monotherapy alone.
Clinical Studies
The SURMOUNT-1 programme (Eli Lilly, 2022, published in the New England Journal of Medicine) studied Tirzepatide over 72 weeks in people with obesity. Result: an average body weight reduction of up to 22.5% in the highest dose group (15mg) — significantly more than Semaglutide in comparable trials.
Tirzepatide vs. Semaglutide vs. Retatrutide
| Peptide | Agonism | Avg. reduction (trial) | Status |
|---|---|---|---|
| Semaglutide | GLP-1 | ~15% (STEP-1) | Approved |
| Tirzepatide | GLP-1, GIP | ~22.5% (SURMOUNT-1) | Approved |
| Retatrutide | GLP-1, GIP, Glucagon | ~24% (TRIUMPH) | Phase 2 |
Storage
Tirzepatide is supplied as a lyophilized powder. Storage: dry, protected from light at 2–8°C. After reconstitution with BAC Water keep refrigerated and use within 4 weeks. See our Storage Guide for more.
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