The Complete GLP-1 Class Comparison: Semaglutide vs. Tirzepatide vs. Retatrutide vs. CagriSema
12 min · 2026-01-12 · Ercle Editorial
A practitioner-focused breakdown of the GLP-1 drug class as of 2025: mechanism differences, efficacy comparisons, safety profiles, and what the pipeline looks like.
The Mechanism Ladder
Understanding how these agents differ mechanistically is essential to understanding their efficacy differences:
| Agent | Receptors | Half-life | Route |
|---|---|---|---|
| Liraglutide | GLP-1 | 13 hrs | SC daily |
| Semaglutide | GLP-1 | ~7 days | SC weekly / oral |
| Tirzepatide | GLP-1 + GIP | ~5 days | SC weekly |
| Retatrutide | GLP-1 + GIP + GCGR | ~6 days | SC weekly |
| CagriSema | GLP-1 + Amylin | ~7 days | SC weekly |
| Orforglipron | GLP-1 (small molecule) | ~12 hrs | Oral daily |
Efficacy Comparison
| Agent | Weight Loss (Phase III) | Trial |
|---|---|---|
| Liraglutide 3 mg | ~6% | SCALE |
| Semaglutide 2.4 mg | ~15% | STEP 1 |
| Tirzepatide 15 mg | ~21% | SURMOUNT-1 |
| CagriSema | ~23% | REDEFINE-1 |
| Retatrutide 12 mg | ~24% (Phase 2) | Phase 2 |
Key Safety Differentiators
All share:
- GI side effects (nausea, vomiting, diarrhea)
- Thyroid C-cell warning (animal data only; human significance unclear)
- Pancreatitis risk (rare; ~0.1%)
- Gastric emptying-related drug interactions
Tirzepatide-specific:
- Slightly higher nausea rate at initiation vs. semaglutide
Retatrutide-specific:
- Modest heart rate increase (glucagon receptor effect)
- Elevated liver enzymes at high doses (monitor LFTs)
The Access Question
The most efficacious agents are also the newest and most expensive. Insurance coverage patterns:
- Semaglutide/Tirzepatide: Increasingly covered; manufacturer PAP programs exist
- Retatrutide/CagriSema: Not yet approved; no commercial availability
Pipeline Watch
2025-2026 expected milestones:
- Retatrutide: Phase III TRIUMPH results expected 2026; NDA filing 2026-2027
- CagriSema: NDA filing expected 2025; approval possible 2026
- Orforglipron: Phase III results expected 2025; potential first oral GLP-1 without food restrictions
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