PEPTIDEREPORT

Compound comparison

Retatrutide vs Tirzepatide

Retatrutide and tirzepatide are both Eli Lilly investigational peptides targeting incretin receptors for obesity and metabolic disease, but they differ in receptor pharmacology and regulatory status. Tirzepatide is a dual GIP/GLP-1 receptor agonist FDA-approved as Mounjaro (Type 2 diabetes) and Zepbound (chronic weight management). Retatrutide is a triple GLP-1/GIP/glucagon receptor agonist still in Phase 3 clinical trials (TRIUMPH program) and not approved for any indication. Early Phase 2 data showed retatrutide achieving approximately 24% weight loss at 48 weeks, while the SURMOUNT-1 Phase 3 trial showed tirzepatide achieving 22.5% mean weight loss at 72 weeks. The addition of glucagon receptor agonism in retatrutide may provide additional metabolic effects beyond weight loss, though Phase 3 confirmation is pending.

Last reviewed 2026-07-08 Next review 2026-08-07

At a glance

Attribute Retatrutide Tirzepatide
Mechanism Triple receptor agonist: GLP-1, GIP, and glucagon receptor agonism; the glucagon component may provide additional metabolic effects beyond weight loss Dual receptor agonist: GIP and GLP-1 receptor agonism; does not target glucagon receptors
Receptor targets GLP-1, GIP, and glucagon receptors (three simultaneous targets) GLP-1 and GIP receptors (two simultaneous targets)
Developer Eli Lilly Eli Lilly
FDA approval status Not FDA-approved for any indication; investigational only FDA-approved as Mounjaro (Type 2 diabetes, May 2022) and Zepbound (chronic weight management, November 2023)
Clinical trial stage Phase 3 (TRIUMPH trial program, NCT05882045); Phase 2 published in NEJM 2023 Post-approval; multiple Phase 3 trials completed (SURMOUNT-1, SURPASS-2); ongoing outcomes trials
Key weight loss evidence Phase 2 trial: approximately 24% weight loss at 48 weeks at the highest dose (Jastreboff et al., NEJM 2023); Phase 3 data pending SURMOUNT-1 Phase 3 trial: 22.5% mean weight loss at 72 weeks at the highest dose (Jastreboff et al., NEJM 2022)
Approved indications None (investigational) Type 2 diabetes (Mounjaro) and chronic weight management (Zepbound)
Regulatory availability Available only through clinical trial enrollment; not available via prescription or telehealth Available by prescription through healthcare providers and telehealth platforms for FDA-approved indications
Additional metabolic effects Glucagon receptor agonism is hypothesized to increase energy expenditure and enhance lipid metabolism; Phase 3 confirmation pending No glucagon receptor activity; metabolic effects are mediated through GLP-1 and GIP pathways
Social media attention High and growing attention from fitness and biohacking communities; multiple long-form YouTube videos with hundreds of thousands of views discussing it as a future weight loss treatment Among the most discussed weight loss drugs in biohacking and fitness communities; extensive mainstream and social media coverage

Retatrutide (LY3437943) is an investigational triple receptor agonist developed by Eli Lilly that simultaneously targets GLP-1, GIP, and glucagon receptors. The addition of glucagon receptor agonism distinguishes it from tirzepatide and is hypothesized to provide additional metabolic benefits such as increased energy expenditure and enhanced lipid metabolism, though these effects require confirmation in Phase 3 trials.

The Phase 2 trial published in NEJM (Jastreboff et al., 2023) demonstrated dose-dependent weight loss with retatrutide, achieving approximately 24% weight loss at 48 weeks at the highest dose studied. This supported advancement to the Phase 3 TRIUMPH trial program, which is currently ongoing.

Retatrutide is not FDA-approved for any indication. It is available only through clinical trial enrollment (TRIUMPH program, ClinicalTrials.gov NCT05882045). Any products marketed online as retatrutide outside of clinical trials are unapproved and subject to FDA enforcement, as illustrated by the 2026 FDA warning letter to Gram Peptides.

Tirzepatide is a dual GIP and GLP-1 receptor agonist developed by Eli Lilly. It was FDA-approved as Mounjaro in May 2022 for Type 2 diabetes and as Zepbound in November 2023 for chronic weight management. It is one of the most prescribed and discussed drugs in the GLP-1 receptor agonist class.

The SURMOUNT-1 Phase 3 trial, published in NEJM (Jastreboff et al., 2022), demonstrated a mean weight loss of 22.5% at 72 weeks at the highest dose. The SURPASS-2 trial showed superior A1C reduction versus semaglutide in Type 2 diabetes patients.

Tirzepatide is available by prescription through healthcare providers and telehealth platforms for its FDA-approved indications. Ongoing trials are evaluating cardiovascular outcomes, sleep apnea, and liver disease (MASH) as additional indications.

Summary verdict

Retatrutide and tirzepatide are both Eli Lilly incretin-based peptides, but they differ fundamentally in receptor pharmacology and regulatory status. Tirzepatide is a dual GLP-1/GIP agonist with FDA approval for Type 2 diabetes and chronic weight management, backed by completed Phase 3 trials showing 22.5% weight loss at 72 weeks. Retatrutide is a triple GLP-1/GIP/glucagon agonist still in Phase 3 trials with promising Phase 2 data showing approximately 24% weight loss at 48 weeks, but no regulatory approval. The glucagon receptor component in retatrutide may offer additional metabolic benefits that tirzepatide does not, though this remains to be confirmed in Phase 3. Tirzepatide is available by prescription; retatrutide is available only through clinical trials. This comparison documents mechanistic and regulatory differences; it does not recommend either compound or provide treatment guidance.

Related compounds: Retatrutide · Tirzepatide

Sources on this page

Source records are stored in the repo and linked from this comparison.

Retatrutide for Obesity — A Phase 2 Trial

New England Journal of Medicine · Peer reviewed · 2023-06-26 · accessed 2026-07-01

Phase 2 randomized trial of retatrutide (LY3437943), a triple GLP-1/GIP/glucagon receptor agonist, showing dose-dependent weight loss up to 17.5% at 48 weeks in adults with obesity.

TRIUMPH Phase 3 Trial Program for Retatrutide — ClinicalTrials.gov

ClinicalTrials.gov / U.S. National Library of Medicine · Primary regulatory · 2023-07-01 · accessed 2026-07-01

ClinicalTrials.gov registry entry for the TRIUMPH Phase 3 trial program evaluating retatrutide for obesity, sponsored by Eli Lilly. Retatrutide is not FDA-approved for any indication.

Warning Letter: Gram Peptides

U.S. Food and Drug Administration · Primary regulatory · 2026-03-31 · accessed 2026-06-30

FDA warning letter discussing peptide products marketed online and the limits of research-use-only positioning.