Semaglutide, tirzepatide and retatrutide are frequently discussed as if interchangeable. Mechanistically they are three different tools. Here is the side-by-side.
Receptor coverage is the axis that matters. Every other difference between these compounds — half-life, solubility, analytical method — follows from how many receptor arms the molecule was designed to engage.
| Compound | Receptors | Research half-life | Class |
|---|---|---|---|
| Semaglutide | GLP-1 | ~7 days | Mono agonist |
| Tirzepatide | GIP + GLP-1 | ~5 days | Dual incretin |
| Retatrutide | GIP + GLP-1 + GCG | ~6 days | Triple incretin |
| Cagrilintide | Amylin / calcitonin | ~7 days | Amylin analog |
What the extra receptor arm changes
- Adding GIP-R introduces a second incretin input and shifts nutrient-partitioning readouts.
- Adding GCG-R introduces a hepatic energy-expenditure arm absent from both other classes.
- Amylin analogs sit outside the incretin family entirely and are not a substitute comparator.
Keeping comparative datasets honest
- Fix the counterion form across arms — acetate and TFA salts differ in net peptide mass.
- Match reconstitution diluent and storage temperature across every arm of the comparison.
- Source all comparators from one supplier and one documentation standard.
- Record lot numbers per arm so an anomalous result can be traced to a batch.
Incretin class FAQ
Is a triple agonist automatically the stronger research tool?
No. More receptor arms means more variables. Mono agonists remain the cleaner instrument when a study isolates GLP-1 signalling.
Can these compounds be compared across suppliers?
Not reliably. Counterion content, water content and purity vary between suppliers, so cross-supplier comparisons carry an uncontrolled mass variable.
Research use only. Every Restore Labs article is in-vitro and laboratory reference material for qualified Australian researchers. Nothing here is medical, therapeutic, dosing or performance guidance for human or veterinary use.
