Retatrutide vs tirzepatide: how the triple and dual agonists compare

Retatrutide and tirzepatide come from the same developer, share most of their sequence and the same fatty-acid half-life strategy, and are studied in overlapping populations. The difference that defines them is one receptor: retatrutide adds glucagon receptor agonism to the GIP and GLP-1 receptor activity that tirzepatide already has. That single design choice shows up in the sequence, the trial results and the safety signals.

This page compares the two molecule by molecule and trial by trial, using the same verified figures as the retatrutide and tirzepatide overviews. One caution runs through everything below: no head-to-head result has been published. The trial results sit side by side because readers ask for them, not because they can be ranked. Nothing here is medical or usage guidance.

Retatrutide vs tirzepatide at a glance

Property	Retatrutide	Tirzepatide
Development code	LY3437943 [1]	LY3298176 [2]
Receptors	GIPR, GLP-1R, glucagon receptor (GCGR) [3] [4]	GIPR, GLP-1R [5]
Length	39 residues, C-terminal serine amide [1] [3]	39 residues, C-terminal serine amide [2] [5]
Molecular formula	C221H342N46O68 [3]	C225H348N48O68 [5]
Average molecular weight	4731.34 [3]	4813.53 Da (label); 4813.45 (KEGG) [5] [6]
Monoisotopic mass	About 4728.47 [3]	About 4810.52 [6]
CAS number	2381089-83-2 [1]	2023788-19-2 [2]
Lipid and linker	C20 di-acid via γGlu and one OEG unit, on Lys17 [1]	C20 di-acid via γGlu and two OEG units, on Lys20 [2] [5]
Half-life	About 6 days (phase 1b) [7]	About 5 days (label) [5]
Status (October 2026)	Investigational; no Drugs@FDA record [8]	FDA-approved since 13 May 2022 [9]

Receptor profile: triple versus dual agonism

Tirzepatide “selectively binds to and activates both the GIP and GLP-1 receptors” [5]. In HEK293 cells its GIP receptor binding affinity (Ki 0.135 nM) was comparable to native GIP, while its GLP-1 receptor affinity (Ki 4.23 nM) was about five-fold weaker than native GLP-1 [10]. Receptor-occupancy modelling at clinically efficacious exposures showed greater engagement of the GIP receptor than the GLP-1 receptor, and at the GLP-1 receptor tirzepatide favours cAMP signalling over β-arrestin recruitment, which is why its developers describe it as “imbalanced and biased” [11].

Retatrutide adds the glucagon receptor. In vitro it “shows balanced GCGR and GLP-1R activity but more GIPR activity” [4]. The case for the third receptor comes from mice: in obese mice, “body weight loss was augmented by the addition of GCGR-mediated increases in energy expenditure to GIPR- and GLP-1R-driven calorie intake reduction” [4]. In plain terms, the incretin components are thought to reduce intake and the glucagon component to raise expenditure.

Receptor	Retatrutide	Tirzepatide	Evidence level
GIP receptor	Agonist; the most active of its three in vitro [4]	Agonist; affinity comparable to native GIP [10]	In vitro
GLP-1 receptor	Agonist; activity balanced with GCGR [4]	Agonist; weaker than native GLP-1, cAMP-biased [10] [11]	In vitro
Glucagon receptor	Agonist; linked to energy expenditure in mice [4]	Not a target [5]	In vitro and animal

Both receptor profiles are measured in cells and mice. The separate contribution of each receptor to effects in people has not been isolated for either molecule.

Structure: sequence, linker and acylation site

Lining up the KEGG sequences with the FDA substance records shows how small the structural distance is [1] [2] [3] [6]:

Retatrutide  Y-Aib-QGTFTSDYSI-αMeL-LDK-K*-AQ-Aib-AFIEYLLEGGPSSGAPPPS-NH2
Tirzepatide  Y-Aib-EGTFTSDYSI-Aib-LDKIAQ-K*-AFVQWLIAGGPSSGAPPPS-NH2
(* = lysine carrying the C20 di-acid side chain)

The two chains are identical at 30 of 39 positions, including Tyr1, Aib2 and the C-terminal GPSSGAPPPS-NH2 segment. They differ at nine:

Position	Retatrutide	Tirzepatide	Why it matters
3	Gln	Glu	Retatrutide’s glutamine adds a deamidation site
13	α-methyl-L-leucine	Aib	Both are α-methylated, hindered residues
17	Lys, acylated	Ile	Acylation site in retatrutide
20	Aib	Lys, acylated	Acylation site in tirzepatide
23	Ile	Val	Hydrophobic face
24	Glu	Gln
25	Tyr	Trp	Tirzepatide’s Trp25 is an oxidation site; retatrutide has no tryptophan
27	Leu	Ile
28	Glu	Ala

Sources for the positions: KEGG one-letter sequences [3] [6] and the substance records, which identify position 13 of retatrutide as 2-methyl-L-leucyl and positions 2 and 20 as 2-methylalanyl (Aib) [1], and tirzepatide’s Aib at 2 and 13 [2].

The linker. Both carry a C20 fatty di-acid attached through γ-glutamate and 8-amino-3,6-dioxaoctanoic acid (OEG) spacers, but not the same number. Retatrutide’s systematic name contains a single “2-[2-(2-aminoethoxy)ethoxy]acetyl” unit on Lys17 [1]; tirzepatide’s structural modification is recorded as “γ-Glu-bis(iminobis(ethylenoxy)acetyl)” on Lys20, that is, two OEG units [2]. The label describes tirzepatide’s Lys20 as “attached to 1,20-eicosanedioic acid via a linker” [5]. The extra OEG unit plus the other substitutions account for the 82 Da difference in monoisotopic mass between the two molecules [3] [6].

Half-life. The C20 di-acid binds albumin in both. Tirzepatide is 99% albumin-bound with an elimination half-life of approximately 5 days [5]; retatrutide’s half-life was approximately 6 days in a 12-week phase 1b study, with dose-proportional pharmacokinetics [7]. Retatrutide has no approved label, so its figure comes from early-phase data only.

Published trial programmes side by side

Tirzepatide’s programmes are SURPASS (type 2 diabetes) and SURMOUNT (weight management). Retatrutide’s are TRIUMPH (obesity, with nested sleep apnoea and knee osteoarthritis protocols) and TRANSCEND-T2D (type 2 diabetes) [12]. Dose levels are omitted; ranges span each trial’s active arms.

Read every row with these limits in mind:

• The trials were run separately, not head to head.
• Durations differ: TRIUMPH weight trials ran 80 weeks, SURMOUNT-1 and SURMOUNT-2 ran 72 weeks [13] [14] [15].
• Placebo responses differ between trials (for example −5.1% in TRIUMPH-2 versus −3.2% in SURMOUNT-2), which shifts any naive comparison [16] [15].
• Baseline populations, estimands and enrolment periods differ.

Phase 2 in type 2 diabetes (both with a dulaglutide arm)

	Tirzepatide phase 2 (2018)	Retatrutide phase 2 (2023)
n	318 randomised [17]	281 randomised [18]
Primary endpoint	HbA1c change at 26 weeks [17]	HbA1c change at 24 weeks [18]
Active arms	−1.06 to −1.94 points [17]	−0.43 to −2.02 points [18]
Placebo	−0.06 [17]	−0.01 [18]
Dulaglutide	−1.21 [17]	−1.41 [18]

These are the closest thing to a common comparator in the published record, since both trials included the same GLP-1 receptor agonist. Even so, they were separate trials in different years and populations.

Obesity without diabetes

	SURMOUNT-1 (tirzepatide)	TRIUMPH-1 (retatrutide)
Phase	3 [14]	3, basket design [13] [12]
n	2,539 [14]	2,339 [13]
Duration	72 weeks [14]	80 weeks [13]
Mean weight change, active arms	−15.0%, −19.5%, −20.9% [14]	−17.6%, −23.7%, −25.0% [13]
Placebo	−3.1% [14]	−3.9% [13]

Retatrutide’s phase 2 obesity trial (338 adults, 48 weeks) reported −8.7% to −24.2% versus −2.1% with placebo [19]. TRIUMPH-1 also contained a knee osteoarthritis cohort of 574 participants, in which WOMAC pain differences versus placebo were −1.6 and −1.8 points in the primary analysis [13]; tirzepatide has no comparable published knee osteoarthritis trial among the sources reviewed here.

Obesity with type 2 diabetes

	SURMOUNT-2 (tirzepatide)	TRIUMPH-2 (retatrutide)
n	938 [15]	1,152 [16]
Duration	72 weeks [15]	80 weeks [16]
Mean weight change, active arms	−12.8% and −14.7% [15]	−11.9%, −16.8%, −18.8% [16]
Placebo	−3.2% [15]	−5.1% [16]
Baseline HbA1c	8.02% [15]	7.71% [16]

In both programmes, mean weight change in the trial of people with type 2 diabetes was smaller than in the trial of people without diabetes [14] [13] [15] [16].

Obstructive sleep apnoea

	SURMOUNT-OSA (tirzepatide)	TRIUMPH-1-OSA and TRIUMPH-2-OSA (retatrutide)
Design	Two placebo-controlled trials, with and without positive airway pressure [20]	Two protocols nested in TRIUMPH-1 and TRIUMPH-2 [21]
n	Not stated in the abstract [20]	243 and 448 [21]
Duration	52 weeks [20]	80 weeks [21]
Baseline AHI (events per hour)	51.5 and 49.5 [20]	58.6 and 55.9 [21]
AHI change, active	−25.3 and −29.3 [20]	−22.9 to −34.3 (without diabetes); −19.2 to −25.4 (with diabetes) [21]
AHI change, placebo	−5.3 and −5.5 [20]	−9.9 and −10.3 [21]
Largest difference versus placebo	−20.0 and −23.8 [20]	−24.4 and −15.1 [21]

TRIUMPH-2-OSA enrolled people with type 2 diabetes as a separate population, baseline AHI was higher in the retatrutide trials, and follow-up was 28 weeks longer [20] [21].

Type 2 diabetes monotherapy

	SURPASS-1 (tirzepatide)	TRANSCEND-T2D-1 (retatrutide)
n	478 [22]	537 [23]
Duration	40 weeks [22]	40 weeks [23]
Baseline HbA1c	7.9% [22]	7.9% [23]
HbA1c change, active arms	−1.87 to −2.07 points [22]	−1.69 to −1.94 points [23]
HbA1c change, placebo	+0.04 [22]	−0.81 [23]
Weight change, active arms	−7.0 to −9.5 kg [22]	−11.5% to −15.3% vs −2.6% [23]

The placebo arm in TRANSCEND-T2D-1 lowered HbA1c by 0.81 points, against a small rise in SURPASS-1 [22] [23]. Absolute changes therefore cannot be compared directly; the placebo-adjusted difference for retatrutide was −0.88 to −1.12 points [23].

Liver

The two liver studies measured different things. A substudy of retatrutide’s phase 2 obesity trial (98 participants with at least 10% liver fat) reported relative liver-fat reductions of −42.9% to −82.4% at 24 weeks versus +0.3% with placebo, measured by imaging [24]. Tirzepatide’s phase 2 SYNERGY-NASH trial (190 participants with biopsy-confirmed steatohepatitis and moderate or severe fibrosis) used liver biopsy at 52 weeks: resolution of steatohepatitis without worsening of fibrosis occurred in 10% with placebo and in 44% or more in the tirzepatide arms, with differences of up to 53 percentage points [25]. Imaging fat content and biopsy histology are not interchangeable endpoints.

Cardiovascular outcomes

Tirzepatide has a completed outcomes trial. In SURPASS-CVOT, among 13,165 patients with type 2 diabetes and atherosclerotic cardiovascular disease, cardiovascular death, myocardial infarction or stroke occurred in 12.2% with tirzepatide and 13.1% with dulaglutide (HR 0.92, 95.3% CI 0.83 to 1.01); noninferiority was met and superiority was not [26]. Retatrutide’s outcomes trial, TRIUMPH-Outcomes (NCT06383390), plans 10,000 participants with a composite of cardiovascular events and a second kidney composite, and is not expected to reach primary completion until February 2029 [27].

The head-to-head trial: TRIUMPH-5

TRIUMPH-5 (NCT06662383) is the direct comparison. It plans to enrol about 800 adults with obesity, randomised to retatrutide or tirzepatide, with percent change in body weight from baseline to week 80 as the primary outcome [28]. In October 2026 the record was listed as active, not recruiting, with primary completion estimated for November 2026 [28]. Until it reports, any claim that one molecule produces more weight loss than the other rests on cross-trial comparison.

Safety findings reported in studies

Finding	Retatrutide	Tirzepatide
Most common events	Gastrointestinal, dose-related, mostly mild to moderate [19]	Gastrointestinal, mostly mild to moderate, mainly during dose escalation [14]
Diarrhoea and nausea (obesity with type 2 diabetes)	TRIUMPH-2: diarrhoea 27–34% vs 13%; nausea 14–28% vs 8% [16]	SURMOUNT-2: nausea, diarrhoea and vomiting most frequent; discontinuation for events under 5% [15]
Heart rate	Dose-dependent increases peaked at 24 weeks then declined (phase 2) [19]	Not reported in the abstracts reviewed here
Hypotension, dysaesthesia	More frequent than placebo in TRIUMPH-2 (hypotension 1–6% vs under 1%; dysaesthesia 4–7% vs 1%) [16]	Not reported in the abstracts reviewed here
Discontinuation for adverse events	Up to 12% in one higher arm vs 5% with placebo (TRIUMPH-2) [16]	4.3–7.1% vs 2.6% with placebo (SURMOUNT-1) [14]
Label warnings	No label	Boxed warning: thyroid C-cell tumours in rats; human relevance unknown [5]

Hypotension and dysaesthesia in TRIUMPH-2 [16], and the dose-dependent heart-rate pattern in the retatrutide phase 2 trial [19], are findings reported for retatrutide that do not appear in the tirzepatide sources reviewed here. “Not reported in the abstracts reviewed here” means only that; it does not mean the event did not occur. Long-term cardiovascular safety for retatrutide awaits TRIUMPH-Outcomes [27].

Regulatory status

Region	Retatrutide	Tirzepatide
United States	Not approved; no Drugs@FDA record [8]	Approved 13 May 2022 (NDA 215866) and under a second application, NDA 217806 [9]
Names	INN, USAN assigned [1]	INN, USAN and JAN assigned [2]
Development stage	Phase 3 completed and ongoing [13] [28]	Marketed; further trials ongoing

Regional authorisations beyond the US for tirzepatide, and the absence of any authorisation for retatrutide in the EU, are covered in the individual overviews.

Laboratory and analytical comparison

For researchers handling both molecules, the practical differences are analytical:

• Intact mass. Monoisotopic masses of about 4728.47 (retatrutide) and 4810.52 (tirzepatide) differ by about 82 Da, easily resolved by LC-MS [3] [6].
• Acylation site. Peptide mapping should place the side chain on Lys17 for retatrutide, not on its neighbour Lys16, and on Lys20 for tirzepatide [1] [2].
• Linker composition. A missing or extra OEG unit changes mass by one spacer unit and is a specific side-chain impurity to look for in each molecule.
• Oxidation and deamidation. Tirzepatide’s Trp25 is an oxidation site that retatrutide lacks; retatrutide’s Gln3 adds a deamidation site where tirzepatide has glutamate [3] [6].
• Hindered couplings. Both have α,α-disubstituted or α-methylated residues (retatrutide: Aib2, αMeL13, Aib20; tirzepatide: Aib2, Aib13), so deletion sequences at those positions are expected process impurities [1] [2].

Synthesis routes and impurity control are covered in SPPS vs LPPS and peptide API impurities and specifications; storage of the dry powders in lyophilised peptide stability and storage. For how both compare with single GLP-1 receptor agonists, see GLP-1 agonists explained.

How Winhycare Pharma supplies retatrutide and tirzepatide

Winhycare Pharma supplies retatrutide and tirzepatide as research-use-only material for laboratories and, separately, as API to licensed pharmaceutical manufacturers and developers. Material is supplied at ≥99% purity, as stated in our brochure, with a certificate of analysis for every batch, and custom synthesis is available. Specifications are on the retatrutide and tirzepatide supplier pages; to request a quotation, use the retatrutide API enquiry or tirzepatide API enquiry form.

For laboratory research use only. Not for human or veterinary use.