Compound Guide• 7 min read
Retatrutide vs Tirzepatide: Triple Agonist vs Dual Agonist Research
Retatrutide adds glucagon-receptor activity on top of the GLP-1/GIP dual agonism that defines tirzepatide. The Phase 2 readout (NEJM, 2023) made it the most-watched investigational peptide in metabolic research.
Mechanism difference
Tirzepatide is engineered as a balanced GLP-1/GIP dual agonist. Retatrutide adds a third arm — glucagon receptor agonism — which increases energy expenditure and accelerates hepatic lipid mobilization in published rodent and human work.
Phase 2 trial outcomes
The retatrutide Phase 2 obesity trial (Jastreboff et al., NEJM 2023) reported a mean 24.2% body-weight reduction at the 12 mg dose over 48 weeks. Tirzepatide's SURMOUNT-1 reported ~22.5% at 15 mg over 72 weeks. The delta is meaningful given retatrutide's shorter trial duration.
Why glucagon agonism matters
Glucagon receptor activity increases basal metabolic rate and drives hepatic fat oxidation. The traditional concern — hyperglycemia from unopposed glucagon — is offset by simultaneous GLP-1/GIP activity, which preserves insulin secretion and glycemic control.
Research-availability status
Tirzepatide is FDA-approved (Mounjaro, Zepbound) and widely available as a research-grade peptide. Retatrutide is in Phase 3 trials (TRIUMPH program) and is research-use-only — not approved for human use in any jurisdiction.
FAQ
Is retatrutide also called GLP-3?
GLP-3 is informal shorthand used in the research community for the GLP-1/GIP/glucagon triple-agonist class. It is not an official receptor designation.
When is retatrutide expected to launch?
Eli Lilly's TRIUMPH Phase 3 program is ongoing through 2026–2027; commercial launch decisions follow regulatory submission.