Tirzepatide, retatrutide and semaglutide: how they differ
Three peptides from the same family, at three very different points in their research.
All three belong to the same family —the incretins, peptides that mimic gut hormones— and are easily confused. What really separates them is simple to state: how many receptors each acts on. Semaglutide on one, tirzepatide on two and retatrutide on three. Beneath that sentence are three compounds at very different points in their history.
This page describes published literature. It is not medical information and does not describe a therapeutic use, and what is sold here are reagents for in vitro research, not medicines.
The difference at a glance
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptors | GLP-1 (one) | GIP + GLP-1 (two) | GIP + GLP-1 + glucagon (three) |
| Which came first | GLP-1 analogue | First dual agonist | First triple agonist |
| Regulatory status | Approved as a medicine in the EU | Approved as a medicine in the EU | Not approved in any country |
| Research stage | Trials in tens of thousands | Phase 3 completed, approved | In phase 3, not approved |
Semaglutide: one receptor, the most studied
It is a GLP-1 analogue modified to last and be administered once a week, and the compound in the family with the most clinical literature behind it: its trials are counted in tens of thousands of people, including cardiovascular outcome studies. It is approved as a medicine in the EU.
Tirzepatide: two receptors, the leap to dual agonism
It was the first peptide to activate both the GIP and the GLP-1 receptor at once; its founding question was precisely whether adding GIP contributed anything over a GLP-1 agonist alone. It has phase 3 trials in thousands of people and authorisation as a medicine in the EU.
Retatrutide: three receptors, still in research
It adds a third arm, glucagon, to the previous two. It is the newest of the three and the only one not approved in any country: it is in phase 3, the stage before applying for authorisation, with published phase 2 data. The idea its authors describe is that each receptor does something different and combining them adds effects that limit each other when separate.
Why you won't see «which works best» here
Each compound has been studied in different trials, with different populations, durations and designs, and none has been compared with the others head to head. Lining up their figures as if they were a race would give a conclusion the data do not support. Each one's figures, in context and with their references, are in its sheet; that is where they mean something.
And the distinction that runs through all three sheets: a molecule being approved says nothing about what is in a vial that does not come from a pharmacy. Semaglutide and tirzepatide are approved as medicines; the reagent vial sold here is not that medicine, it does not carry its package leaflet, its batch control or its pharmacovigilance, and it is for in vitro research.
What to check when comparing suppliers of these compounds
In this family there are several analogues of similar molecular weight, so a purity certificate is not enough: identity confirmation by mass spectrometry is needed to know which one it is, as well as HPLC purity of the specific lot and a real cold chain. For retatrutide, with no commercial reference to compare against, identity matters even more.
EuroPeptiva sells material intended exclusively for laboratory research. No product is approved for human, veterinary or diagnostic use.