Retatrutide vs Tirzepatide vs Semaglutide: Research Comparison

Three peptides, three receptor profiles

Semaglutide, Tirzepatide, and Retatrutide all belong to the incretin-mimetic class, but they target different receptors and produce different effects in published research.

Semaglutide — single agonist (GLP-1)

• Receptor: GLP-1 receptor.
• Half-life: ~7 days (via C18 fatty-acid modification + albumin binding).
• Research history: the most published of the three; SUSTAIN, PIONEER, STEP trial series.
• Notable feature: once-weekly dosing became the class benchmark.

Tirzepatide — dual agonist (GLP-1 + GIP)

• Receptors: GLP-1 and GIP.
• Half-life: ~5 days.
• Research history: SURPASS and SURMOUNT trial series demonstrated stronger effects than single-agonist GLP-1 approaches in the studied populations.
• Notable feature: GIP co-agonism appears to complement GLP-1 signaling.

Retatrutide — triple agonist (GLP-1 + GIP + Glucagon)

• Receptors: GLP-1, GIP, and glucagon.
• Half-life: ~6 days.
• Research history: Phase 2 trial data (Jastreboff et al., NEJM 2023) showed substantially larger reductions than dual-agonist reference arms at 48 weeks. Phase 3 trials ongoing at time of writing.
• Notable feature: glucagon-receptor activity is thought to add energy-expenditure effects, though the mechanism is still being characterized.

Side-by-side

Research handling notes

All three are stable lyophilized peptides. Reconstitute with bacteriostatic water; refrigerated post-reconstitution stability is typically 4–6 weeks. Store lyo vials sealed at room temperature or refrigerated.

See PX1's research monograph on Retatrutide for full sequence, mass, and handling data. All three are sold strictly for laboratory research use only.