The field of GLP-1 receptor agonists has evolved in less than a decade from mono-agonists to multi-agonist molecules designed to activate several incretin receptors simultaneously. This article compares the three most representative compounds in the catalog: semaglutide, tirzepatide and retatrutide.
Structure and molecular design
- Semaglutide — A GLP-1 analog with two critical modifications: substitution of Ala8 by Aib (resistance to DPP-4) and conjugation with a C18 fatty acid chain via a spacer, which allows reversible binding to albumin and prolongs the half-life to ~165 hours.
- Tirzepatide — A 39-amino-acid molecule designed as a dual GLP-1/GIP agonist. It incorporates the same acylation strategy, with a C20 fatty acid, to extend half-life (~117 hours). Its affinity for GIP-R is slightly greater than for GLP-1-R.
- Retatrutide — A triple agonist that adds activity at the glucagon receptor. Structurally it is a 39-residue synthetic peptide with a balanced affinity profile across the three receptors, although with somewhat more activity at glucagon than at GIP.
Mechanism of action compared
Activation of GLP-1-R in pancreatic beta cells stimulates glucose-dependent insulin secretion and suppresses postprandial glucagon. Additional activation of GIP-R (tirzepatide, retatrutide) potentiates this incretin effect and is associated, in preclinical models, with greater insulin sensitivity in adipose tissue. Activation of glucagon-R (retatrutide) introduces a lipolytic and thermogenic component that may explain the differential effects observed on body composition.
Clinical research data
In published trials:
- Semaglutide (2.4 mg weekly) — mean reported weight loss of 14–15% of body weight at 68 weeks in cohorts with obesity.
- Tirzepatide (15 mg weekly) — average loss close to 20–22% at 72 weeks in comparable cohorts.
- Retatrutide (12 mg weekly) — preliminary phase 2 data suggest a 24% loss at 48 weeks, but long-term data are lacking.
The percentages above come from published clinical trials; they cannot be extrapolated to use outside a protocol and do not constitute a therapeutic recommendation. NeoPeptidos products are for research purposes only.
Implications for preclinical research
To design a comparative study in animal models, the points to consider are: molar dose equivalence (not mg), different pharmacokinetic profiles between compounds, and choice of outcomes (HbA1c, fat mass, energy expenditure, liver markers).
Tabla resumen
| Compuesto | Receptores | Vida media aprox. | Dosis máxima en ensayos |
| — | — | — | — |
| Semaglutida | GLP-1 | ~165 h | 2.4 mg/sem |
| Tirzepatida | GLP-1 + GIP | ~117 h | 15 mg/sem |
| Retatrutida | GLP-1 + GIP + glucagón | ~150 h | 12 mg/sem |
Conclusion
The progression from mono- to triple agonists represents one of the most interesting trajectories in recent incretin pharmacology. Each compound has a different role in research: semaglutide as the established reference, tirzepatide as an example of dual potentiation, and retatrutide as the experimental spearhead.
🔬 Updated on January 21, 2026 · Reviewed by the NeoPeptidos team · Content for research purposes (RUO).