The Definitive Peptide Research Reference Guide — Compound Review

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Retatrutide vs Tirzepatide

Retatrutide vs Tirzepatide: triple agonist vs dual agonist. Retatrutide adds glucagon receptor agonism to the GLP-1/GIP dual mechanism of tirzepatide, producing greater weight loss in Phase 3 trials.

Clinical Trial Comparison

Tirzepatide (SURMOUNT-1): 20.9% weight loss at 72 weeks. Retatrutide (TRIUMPH-1): 24.2% at 48 weeks. The additional 3–4 percentage points of weight loss with retatrutide is attributed to glucagon receptor agonism increasing energy expenditure.

Mechanism Difference

Tirzepatide: GLP-1 + GIP dual agonism. Retatrutide: GLP-1 + GIP + glucagon triple agonism. The glucagon component increases hepatic glucose production and energy expenditure — the key mechanistic difference driving additional weight loss.

Regulatory Status

Tirzepatide: FDA-approved as Mounjaro (T2D) and Zepbound (obesity). Retatrutide: Phase 3 trials ongoing as of 2026, FDA approval anticipated 2026–2027. Tirzepatide is the appropriate choice for any protocol requiring an approved compound.