COMPARATIVE GUIDE
Research on GLP-1 peptides has evolved rapidly in recent years: from the mono-agonist Semaglutide to the dual-agonist Tirzepatide, and now to the triple-agonist Retatrutide. Each generation targets more metabolic receptors, amplifying the effects on fat loss and metabolic remodeling.
This guide compares the three molecules based on published clinical trial data, to help researchers understand the mechanistic differences and choose the peptide best suited to their protocols.
Comparative table: Retatrutide vs Tirzepatide vs Semaglutide
| Criteria | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Targeted receptors | GLP-1R | GLP-1R + GIPR | GLP-1R + GIPR + GcgR |
| Weight loss (pivotal trial) | ~15% (STEP-1, 68 weeks) | ~22% (SURMOUNT-1, 72 weeks) | ~24% (Phase 2, 48 weeks) |
| Half-life | ~7 days | ~5 days | ~6 days |
| Administration | SC weekly | SC weekly | SC weekly |
| Clinical stage (2026) | Approved (FDA/EMA) | Approved (FDA/EMA) | Phase 3 in progress (NCT06859268) |
| Effect on fat mass | Strong | Very strong | Very strong + hepatic lipolysis |
| Glycemic effect | Strong | Strong | Strong (+ glucagon effect) |
| Availability search | Limit | Limit | ✓ MyPeptide.eu |
Semaglutide: the reference GLP-1 monoagonist
Semaglutide (Ozempic®, Wegovy®) is a selective GLP-1 receptor agonist with a half-life of ~7 days obtained by conjugation to a C18 fatty acid chain. In the STEP-1 trial, it demonstrated an average body weight reduction of 14.9% over 68 weeks in non-diabetic obese patients. (Wilding JPH et al., 2021, PMID 33567185).
Main mechanism: activation of GLP-1R in the hypothalamus (reduction of appetite), pancreatic beta cells (glucose-dependent insulin secretion) and gastric mucosa (slowing of gastric emptying).
Tirzepatide: the GLP-1/GIP dual-agonist
Tirzepatide (Mounjaro®, Zepbound®) simultaneously activates GLP-1R and GIPR receptors. The potentiation of both incretin pathways explains its superiority over Semaglutide: in the SURMOUNT-1 trial (72 weeks), the maximum dose of 15 mg produced a weight reduction of 22.5%. (Jastreboff AM et al., 2022, PMID 35658024).
The GIPR receptor plays a complementary role in the regulation of adipogenesis and directly potentiates the central anorexigenic effect of GLP-1R (Drucker DJ et al., 2023, PMID 36976349).
Retatrutide (LY3437943): the GLP-1/GIP/Glucagon triple agonist
Retatrutide is the first GLP-1R/GIPR/GcgR triple agonist to reach Phase 3 clinical trials. In Phase 2 (48 weeks, n=338), the 12 mg dose produced a mean body weight reduction of 24.2%—the highest ever observed for weekly treatment over this duration. (Jastreboff AM et al., 2023, PMID 37366315).
The addition of glucagon agonist (GcgR) provides three additional effects compared to Tirzepatide:
- Increased energy expenditure basal (thermogenesis)
- Increased hepatic lipolysis — reduction of hepatic steatosis (MASH) (Briand F et al., 2026, PMID 41741376)
- Reduction of de novo lipogenesis
Its molecular mass is approximately 4,720 Da, with a C18 fatty acid chain conferring a half-life of ~6 days (weekly administration). Retatrutide is currently in Phase 3 (TRIUMPH-1 trial, NCT06859268) for the indication of obesity.
Which peptide for your research protocol?
The choice depends on the research question:
- Study of specific GLP-1R mechanisms → Semaglutide (selective agonist)
- GLP-1 + GIP potentiation, incretin comparison → Tirzepatide
- Triple-agonist effect, metabolic remodeling, hepatic steatosis → Retatrutide
Scientific sources
- Triple hormone receptor agonist retatrutide for obesity — Phase 2 trial — Jastreboff AM et al. (2023)
- Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1) — Wilding JPH et al. (2021)
- Tirzepatide vs Semaglutide for Obesity (SURMOUNT-1) — Jastreboff AM et al. (2022)
- The biology of incretin hormones — Drucker DJ et al. (2023)
- Retatrutide improves steatohepatitis in murine MASH models — Briand F et al. (2026)
- Retatrutide Phase 3b — TRIUMPH-1 Weight Loss Maintenance — ClinicalTrials.gov (2024)
Scientific sources
- Retatrutide triple agonist for obesity — phase 2 trial — Jastreboff AM et al. (2023)
- Semaglutide 2.4mg in adults with overweight — STEP 1 — Wilding JPH et al. (2021)
- Tirzepatide vs semaglutide in type 2 diabetes — SURPASS-2 — Frías JP et al. (2021)
- Comparative efficacy of GLP-1/GIP/glucagon agonists — Tan HC et al. (2023)