Retatrutide vs Tirzepatide vs Semaglutide: Comparing the GLP-1 Research Peptides
Three names dominate metabolic peptide research in 2026: semaglutide, tirzepatide, and retatrutide. They are often grouped together, but they work through different numbers of receptor pathways — and the published data reflects that. Here is a clear, side-by-side look at what the research actually shows.
The key difference: how many receptors each one targets
The simplest way to understand these compounds is by the receptors they engage. Semaglutide is a single agonist (GLP-1 only). Tirzepatide is a dual agonist (GLP-1 and GIP). Retatrutide is a triple agonist (GLP-1, GIP, and glucagon). For a deeper explanation, see our guide to single, dual and triple agonists.
Semaglutide: the single GLP-1 agonist
Semaglutide is the most studied of the three. In the STEP-1 obesity trial, participants on the 2.4 mg weekly dose lost roughly 15% of body weight at 68 weeks. It set the benchmark that newer compounds are measured against.
Tirzepatide: the dual GIP/GLP-1 agonist
Tirzepatide adds GIP receptor activity on top of GLP-1. In the SURMOUNT-1 trial, the highest dose produced about 21% mean weight loss at 72 weeks — a clear step up from single-agonist results. Our semaglutide vs tirzepatide write-up covers this in more detail.
Retatrutide: the triple agonist
Retatrutide is the newest of the three and adds glucagon-receptor activity. In a Phase 2 trial, the 12 mg dose produced about 24% weight loss at 48 weeks, and the curve had not clearly plateaued — one reason the ongoing Phase 3 TRIUMPH program has drawn so much attention in 2026. See our full retatrutide explainer.
Side-by-side summary
Semaglutide — 1 receptor (GLP-1), ~15% in STEP-1. Tirzepatide — 2 receptors (GIP/GLP-1), ~21% in SURMOUNT-1. Retatrutide — 3 receptors (GIP/GLP-1/glucagon), ~24% in Phase 2. The trend is consistent: in the published literature, engaging more complementary pathways has been associated with larger effects.
What this means for researchers
These figures come from separate trials with different populations and durations, so they are not perfectly comparable head-to-head — but the direction of the field is clear. Each compound is supplied as a lyophilized powder and reconstituted with bacteriostatic water; see our reconstitution guide for general handling.
Research use only. This article is educational and is not medical advice. The compounds discussed are not approved for human or veterinary use, consumption, or therapeutic application.