Both are once-weekly incretin agonists approved for type 2 diabetes and obesity — but different receptor targets, trial outcomes, and synthesis profiles distinguish them. This page covers what the research actually shows.
Research reference only. Not medical advice, prescribing guidance, or a product recommendation.
| Dimension | Semaglutide | Tirzepatide |
|---|---|---|
| Generic name | Semaglutide | Tirzepatide |
| Brand names | Ozempic · Wegovy · Rybelsus | Mounjaro · Zepbound |
| Developer | Novo Nordisk | Eli Lilly |
| Receptor targets | GLP-1R only | GIP-R + GLP-1R |
| Agonism class | Mono-agonist | Dual-agonist ("twincretin") |
| Chain length | 31 amino acids | 39 amino acids |
| Half-life | ~168 h (once-weekly) | ~120 h (once-weekly) |
| Approved: T2D | Yes (2017, Ozempic) | Yes (2022, Mounjaro) |
| Approved: obesity | Yes (2021, Wegovy) | Yes (2023, Zepbound) |
| Peak weight ↓ (pivotal) | ~15% (STEP-1, 2.4 mg) | ~22% (SURMOUNT-1, 15 mg) |
| Head-to-head weight ↓ | ~13% (SURMOUNT-5) | ~21% (SURMOUNT-5) |
| CV outcome trial | SELECT (MACE reduction confirmed) | SURPASS-CVOT (non-inferior vs sema) |
−14.9% vs −2.4% (placebo)
Mean body-weight change · n=1961 · 68 wk — Pivotal obesity trial for Wegovy
−22.5% vs −2.4% (placebo)
Mean body-weight change · n=2539 · 72 wk — Pivotal obesity trial for Zepbound
~21% (tirz) vs ~13% (sema)
Head-to-head weight change · n=~750 · 72 wk — Direct head-to-head; tirzepatide superior on primary endpoint
20% MACE reduction vs placebo
MACE (CV outcome) · n=17604 · ~5 yr — Established CV benefit in obesity without T2D
Non-inferior; full results pending
MACE non-inferiority · n=~14000 · Reported ~2024 — Comparator is diabetes-dose sema, not Wegovy dose
| Chain length | 31 AA | 39 AA — more coupling cycles, more deletion impurities |
| Acylation | C18 fatty-diacid on Lys34 (γGlu/mini-PEG linker) | C20 fatty-diacid on Lys26 (modified linker) |
| Receptor design | Native GLP-1 backbone with Aib substitutions | Chimeric GIP/GLP-1 — de novo pharmacophore |
| Analytical | RP-HPLC + SEC + MS | Same, plus more complex impurity profile |
A credible certificate of analysis is the minimum bar for research-grade material of either compound.
On weight reduction, tirzepatide’s dual GIP/GLP-1 agonism outperforms semaglutide’s GLP-1 mono-agonism in both pivotal trials and the direct SURMOUNT-5 head-to-head. Semaglutide has the more mature cardiovascular-outcome evidence (SELECT). These are population means from trial data, not predictions for any individual.
The trajectory continues with retatrutide (LY3437943), an investigational triple agonist that adds glucagon-receptor agonism and reported ~24% mean weight reduction in Phase 2 — exceeding both, but not FDA-approved.
Semaglutide activates only the GLP-1 receptor (mono-agonism). Tirzepatide simultaneously activates both the GIP and GLP-1 receptors (dual agonism). This additional GIP-receptor engagement is associated with larger body-weight reductions in both placebo-controlled and direct head-to-head trials.
In the SURMOUNT-5 direct head-to-head trial, tirzepatide 15 mg achieved approximately 21% mean body-weight reduction vs approximately 13% for semaglutide 2.4 mg over 72 weeks. The difference was statistically significant on the primary endpoint. Individual responses vary, and these are population means — not predictions for any individual.
Ozempic and Wegovy are both semaglutide at different doses: Ozempic (≤2 mg) for type 2 diabetes; Wegovy (2.4 mg) for chronic weight management. Mounjaro (≤15 mg) is tirzepatide for type 2 diabetes and Zepbound is tirzepatide for weight management. The active compound is the same in each pair; dose, labeling, and FDA indication differ.
GIP provides a complementary insulinotropic signal through pancreatic GIPR and potentially an adipose-tissue signal through peripheral GIPR. In tirzepatide, co-activation of both receptor types is hypothesized to produce synergistic satiety and metabolic effects exceeding GLP-1 agonism alone — supported by the magnitude of weight loss in trials.
Retatrutide (LY3437943) adds glucagon-receptor agonism to the GIP/GLP-1 dual mechanism — a triple agonist. In Phase 2 trials it reported approximately 24% mean body-weight reduction at the highest dose, exceeding both semaglutide and tirzepatide data. It remains investigational and is not FDA-approved.