Tirzepatide vs Retatrutide: Dual vs Triple Agonist

Evidence at a glance

Human trials at different stages

Both have real human trial data, but at genuinely different stages. Tirzepatide has Phase 3 evidence and approval. Retatrutide published its first Phase 3 results in 2026 and is not yet approved.

Why researchers are interested

The difference is how many receptors each one works on. Tirzepatide is dual, covering GIP and GLP-1. Retatrutide adds glucagon, which raises energy expenditure on top of appetite reduction, and that third arm is the accepted explanation for its larger Phase 2 weight results.

What the research found

Tirzepatide beat semaglutideGreater HbA1c reduction in a direct Phase 3 head to head (SURPASS-2)
Tirzepatide, weight reductionSignificant weight loss across the SURMOUNT programme
Retatrutide, larger weight lossRoughly 24 percent mean body weight reduction at the top dose at 48 weeks (Jastreboff, NEJM 2023)
Retatrutide, blood sugar controlHbA1c reductions in type 2 diabetes (Rosenstock, Lancet 2023)
Retatrutide, Phase 3Mean body weight change of -25.0 percent at 12 mg over 80 weeks against -3.9 percent with placebo (TRIUMPH-1, NEJM 2026)

Reported in the literature

Both report dose related gastrointestinal effects, mainly nausea, vomiting and diarrhoea, as the dominant finding.
Tirzepatide carries a boxed warning for rodent thyroid C-cell tumours, plus pancreatitis and gallbladder warnings.
Retatrutide trials observed increases in heart rate, and TRIUMPH-2 reported dysesthesia and low blood pressure more often than placebo.
No published trial has compared the two directly; the head to head TRIUMPH-5 trial is still running.
Retatrutide has no long term outcome data yet; its cardiovascular and kidney outcomes trial runs to 2029, so the two cannot be compared on long term safety.

Findings are summarised from the sources listed under References on this page, and from approved product labelling where a compound has one. These are outcomes observed in published studies, not effects claimed for any person, and nothing here is a recommendation for human use.

All research guides

Tirzepatide and retatrutide are compared constantly because both are incretin-based peptides, and the comparison is usually framed as newer-versus-older or stronger-versus-weaker. Neither framing is right. The difference is structural: they engage a different number of receptors, and that changes what each one can be used to study. This guide covers identity, the receptor difference, the state of the evidence for each, and which suits which research question. It is written for researchers and is not medical guidance.

Research-use note: both compounds are supplied strictly for laboratory research. They are not supplements and not for human or animal consumption. Nothing below describes or endorses use in people.

The core difference: dual versus triple agonist

Incretin compounds are most clearly placed by counting the receptors each engages.

Tirzepatide is a dual agonist: GIP receptor + GLP-1 receptor.
Retatrutide is a triple agonist: GIP + GLP-1 + the glucagon receptor.

The glucagon receptor is the entire structural distinction. It is also the interesting one: glucagon signalling is conventionally discussed in opposition to insulin signalling, so a molecule deliberately engaging that receptor alongside two incretin receptors is a departure from how the earlier compounds were designed, rather than an increment on them.

The practical consequence for an experiment is that these are not interchangeable comparators. Comparing them compares two receptor profiles, not two strengths of one thing.

Identity

Property	Tirzepatide	Retatrutide
Receptor targets	GIP + GLP-1 (dual)	GIP + GLP-1 + glucagon (triple)
Developmental code	LY3298176	LY3437943
CAS	2023788-19-2	2381089-83-2
Formula	C₂₂₅H₃₄₈N₄₈O₆₈	C₂₂₁H₃₄₂N₄₆O₆₈
Molar mass	4813 g/mol	≈ 4731 g/mol
Length	39 residues	39 residues
Regulatory status	Approved as a prescription medicine	Investigational candidate, not approved; FDA filing planned for early 2027 (as reported)
Published record	SURPASS and SURMOUNT programmes	Phase 2 trials (2023); Phase 3 TRIUMPH and TRANSCEND trials (2026)

A note on verification. The tirzepatide row was confirmed against PubChem on 2 October 2026 (CID 166567236). The retatrutide CAS does not resolve in PubChem, by number or by name, so its identity figures are reproduced as published rather than independently confirmed here. Anyone depending on them should check against a supplier certificate for the specific lot. Stating that is more useful than implying both rows carry equal weight.

The evidence is not symmetrical

This is the difference most comparisons skip, and it matters more than the receptor count for anyone deciding which to cite.

Tirzepatide has a large registrational clinical record: the SURPASS programme in type 2 diabetes, including the head-to-head SURPASS-2 trial against semaglutide (Frías et al., NEJM, 2021), and SURMOUNT-2 in obesity (Garvey et al., Lancet, 2023). It is an approved medicine, which means its data has been through regulatory review.

Retatrutide’s record grew substantially in 2026. Before then it consisted of preclinical pharmacology (Coskun et al., Cell Metabolism, 2022) and Phase 2 trials in obesity (Jastreboff et al., NEJM, 2023) and type 2 diabetes (Rosenstock et al., Lancet, 2023). It now also has three peer-reviewed Phase 3 trials: TRANSCEND-T2D-1 in type 2 diabetes (Bajaj et al., Lancet, 2026), TRIUMPH-1 in obesity without diabetes (Jastreboff et al., NEJM, 2026) and TRIUMPH-2 in obesity with type 2 diabetes (Bellido et al., Lancet, 2026). It is still investigational: no regulator has reviewed that data, and its cardiovascular and kidney outcomes trial is not expected to complete before 2029.

So the gap has narrowed in kind but not in depth. The dual agonist has the larger, longer and regulator-reviewed literature; the triple agonist has a novel mechanism and a Phase 3 record that is months old. Our retatrutide research guide lists each trial with its population and primary result.

Why cross-trial numbers do not settle the comparison

It is tempting to set a TRIUMPH result beside a SURMOUNT result and call the larger number the winner. That comparison does not hold up. The trials enrolled different populations, ran for different lengths of time, and report results under different estimands (counting everyone randomised, or only those who stayed on treatment). Each of those changes the headline figure on its own.

The question can only be answered by randomising the two compounds within one trial. That trial exists: TRIUMPH-5, a Phase 3 comparison of retatrutide with tirzepatide in adults with obesity (NCT06662383), listed as active, not recruiting on 9 October 2026. Until it reports, no peer-reviewed trial has compared the two directly.

Which suits which research question

Dual incretin (GIP/GLP-1) pathways — tirzepatide is the reference compound, with the deepest and most independently scrutinised literature.
The addition of glucagon-receptor activity to incretin signalling — retatrutide is the compound of interest, and the only one of the two that can address it at all.
Dual versus triple agonism as the variable — both, read as two receptor profiles rather than two potencies.

Deeper background on each is in our tirzepatide research guide and retatrutide research guide.

Handling

Both are supplied as lyophilized powders and handled the same way: reconstitute with bacteriostatic water, swirl rather than shake, store the reconstituted solution at 2–8 °C, keep the sealed vial frozen and protected from light, and avoid repeated freeze-thaw cycles. See how to reconstitute peptides.

For research use only

All products and information referenced here are intended strictly for laboratory and scientific research use only. They are not for human or animal consumption and are not drugs, foods, supplements, or medical devices. The research material supplied here is not an approved pharmaceutical product. Nothing here should be interpreted as medical advice. Products are supplied against a stated purity specification.

Shop these research peptides

Tirzepatide 20 mg — GIP/GLP-1 dual agonist
Retatrutide (GLP-3) — GIP/GLP-1/glucagon triple agonist
Bacteriostatic Water 30 mL — reconstitution diluent
Full research catalog

Common questions about Tirzepatide vs Retatrutide

What is the difference between tirzepatide and retatrutide?

Receptor count. Tirzepatide activates the GIP and GLP-1 receptors. Retatrutide activates those two plus the glucagon receptor, which is why it is called a triple agonist.

Which has more published research?

Tirzepatide, by a wide margin: it has completed Phase 3 programs (SURPASS and SURMOUNT) and is an approved medicine. Retatrutide published Phase 2 results in 2023 and its first Phase 3 results in 2026, and is not yet approved.

Has retatrutide been compared directly with tirzepatide?

Not in a published trial yet. TRIUMPH-5 (NCT06662383), a Phase 3 trial randomising adults with obesity to one or the other, was listed as active, not recruiting in October 2026. Setting one trial's result beside another's is unreliable because populations, durations and estimands differ.

Is retatrutide the same as "GLP-3"?

Yes. "GLP-3" and "reta" are informal nicknames for retatrutide (LY3437943), not official classifications. See the retatrutide research guide.

References

Frías JP, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med. 2021. PubMed
Garvey WT, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2): a phase 3 trial. Lancet. 2023. PubMed
Coskun T, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist. Cell Metab. 2022. PubMed
Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity — a phase 2 trial. N Engl J Med. 2023. PubMed
Rosenstock J, et al. Retatrutide for people with type 2 diabetes: a phase 2 trial. Lancet. 2023. PubMed
Bajaj HS, et al. Efficacy and safety of retatrutide in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a phase 3 trial. Lancet. 2026. PubMed
Jastreboff AM, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1). N Engl J Med. 2026. PubMed
Bellido V, et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a phase 3 trial. Lancet. 2026. PubMed
ClinicalTrials.gov. NCT06662383 (TRIUMPH-5, retatrutide vs tirzepatide). Accessed 9 October 2026.