The core difference: how many receptors each targets
All three belong to the same general family of incretin-pathway compounds, but they're engineered to hit a different number of receptor targets:
- Semaglutide — a single-target GLP-1 receptor agonist.
- Tirzepatide — a dual-target agonist, engaging both the GLP-1 and GIP receptors.
- Retatrutide — a triple-target agonist, adding glucagon receptor (GCGR) activity on top of GLP-1 and GIP.
That third target — the glucagon receptor — is the structural feature that distinguishes Retatrutide from the other two, and it's the reason it gets described in the literature as a "triple G" agonist.
Side-by-side comparison
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptor targets | GLP-1 | GLP-1GIP | GLP-1GIPGCGR |
| Peptide length | 31 amino acids | 39 amino acids | 39 amino acids |
| Approx. molecular weight | ~4,113 g/mol | ~4,813 g/mol | ~4,731 g/mol |
| Regulatory status | FDA-approved (Ozempic, Wegovy) | FDA-approved (Mounjaro, Zepbound) | Investigational — Phase 3 trials (TRIUMPH program) |
| Developer | Novo Nordisk | Eli Lilly | Eli Lilly |
| Available from Half Life Bio | No | No | Yes — 10mg & 30mg |
Why the added receptor targets matter to researchers
Each additional receptor represents a separate signaling pathway under study:
- GLP-1 receptor — associated with appetite regulation, slowed gastric emptying, and glucose-dependent insulin secretion.
- GIP receptor — studied for its role in insulin release and beta-cell function.
- Glucagon receptor (GCGR) — the target unique to Retatrutide among these three — studied for effects on energy expenditure, hepatic glycogen metabolism, and lipolysis.
Researchers studying Retatrutide specifically are typically interested in what combined activation of all three pathways looks like in a single molecule — an angle that isn't observable when studying single- or dual-target compounds in isolation.
How we test our Retatrutide
Every batch we sell is independently tested by a third-party laboratory for purity and content before listing. Full reports for both the 10mg and 30mg formats are published in our COA library.