Retatrutide vs tirzepatide vs semaglutide
Semaglutide activates one receptor, tirzepatide two and retatrutide three. What does that mean for their structure, how do the clinical results compare and which compound suits which research question? Below we compare the three incretin peptides point by point.
At a glance
All three are lipidated peptides given once weekly in clinical studies and derived from gut hormones (incretins). The big difference is the number of receptors they activate.
- Semaglutide (Novo Nordisk) – GLP-1 agonist, 31 amino acids, half-life about 7 days
- Tirzepatide (LY3298176, Eli Lilly) – dual GIP/GLP-1 agonist, 39 amino acids, half-life about 5 days
- Retatrutide (LY3437943, Eli Lilly) – triple GIP/GLP-1/glucagon agonist, 39 amino acids, half-life about 6 days
Receptors: one, two or three
Semaglutide is a GLP-1 analogue and acts only through the GLP-1 receptor. Tirzepatide adds the GIP receptor, which is why it is called a 'twincretin' or dual agonist. Retatrutide additionally activates the glucagon receptor.
That glucagon component is why researchers follow retatrutide so closely. In the liver, glucagon increases fat oxidation and energy expenditure, while GLP-1 and GIP mainly affect insulin secretion and appetite. The question is how much the third receptor adds on top of the dual GIP/GLP-1 signal – which is exactly why retatrutide and tirzepatide are often tested side by side in receptor assays.
Structure and half-life
Semaglutide is built on the sequence of human GLP-1; tirzepatide and retatrutide are built on a GIP backbone. All three carry a fatty-acid side chain that binds serum albumin, so they are cleared slowly and one dose a week is enough in studies.
In the lab, that albumin binding means the protein content of your assay medium can shift the measured potency. Always compare the compounds under the same conditions.
Clinical results side by side
The studies differ in duration, population and analysis method, so the figures are not directly comparable. They do show how the three compounds relate in the literature. The only head-to-head trial so far is SURMOUNT-5 (NEJM, 2025), in which tirzepatide gave 20.2% weight loss after 72 weeks versus 13.7% for semaglutide.
- Semaglutide 2.4 mg – STEP 1 (NEJM, 2021): mean 14.9% weight loss after 68 weeks
- Tirzepatide 15 mg – SURMOUNT-1 (NEJM, 2022): mean 20.9% after 72 weeks
- Retatrutide 12 mg – phase 2 (NEJM, 2023): mean 24.2% after 48 weeks
- Retatrutide 12 mg – TRIUMPH-1 (phase 3, 2026): mean 28.3% after 80 weeks, according to Eli Lilly
Side effects in the studies
For all three, gastrointestinal complaints such as nausea, diarrhoea, constipation and vomiting were the most commonly reported side effects, mainly during dose escalation. In TRIUMPH-1, 11.3% of participants on retatrutide 12 mg stopped because of side effects, versus 4.9% on placebo. Phase 2 studies of retatrutide also showed a dose-dependent rise in heart rate that later declined.
Status in the EU
Semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) are approved medicines in the EU. Retatrutide is not: it is an investigational compound in phase 3, and a marketing application is not expected before 2027.
Virexa Labs supplies retatrutide and tirzepatide solely as research reagents for in-vitro laboratory research – not for human or veterinary use.
Which compound fits your research?
To isolate the effect of the glucagon receptor, retatrutide plus tirzepatide is the logical setup: the two molecules share a similar backbone and lipidation and differ mainly in glucagon activity. We supply both as lyophilized powder with ≥99% HPLC purity and a batch-specific certificate of analysis (COA).
Orders paid before 3 PM on a business day ship the same day: 1–2 business days to Belgium, the Netherlands and Germany.
Retatrutide and tirzepatide for research
Frequently asked questions
What is the main difference between retatrutide and tirzepatide?
Tirzepatide activates two receptors (GIP and GLP-1); retatrutide also activates the glucagon receptor. Both are lipidated 39-amino-acid peptides developed by Eli Lilly.
Is retatrutide stronger than tirzepatide?
In published studies, retatrutide 12 mg produced greater mean weight loss (24.2% after 48 weeks in phase 2, 28.3% after 80 weeks in TRIUMPH-1) than tirzepatide 15 mg (20.9% after 72 weeks in SURMOUNT-1). No study has compared the two directly yet.
What is the difference between semaglutide and retatrutide?
Semaglutide is a 31-amino-acid GLP-1 agonist that activates one receptor; retatrutide is a 39-amino-acid triple agonist that activates the GIP, GLP-1 and glucagon receptors.
Is retatrutide approved?
No. Retatrutide is in phase 3 and is not approved as a medicine anywhere. A marketing application is not expected before 2027.
Do you sell semaglutide?
No. For metabolic research we supply retatrutide, tirzepatide, 5-Amino-1MQ and MOTS-c, among others, all as research peptides with ≥99% purity.