retatrutide
What is retatrutidee
retatrutidee is a synthetic peptide from Eli Lilly’s pipeline. It acts simultaneously on three incretin receptors: GLP-1, GIP and glucagon. This triple agonist property distinguishes retatrutide from semaglutide (only GLP-1) and tirzepatide (GLP-1 plus GIP).
The internal code name is LY3437943. The molecule consists of a modified 39-amino acid peptide chain with C20 fatty acid anchor for albumin binding, stretching the half-life to about one week. The active substance was first introduced in the scientific literature in 2022. The Phase 3 studies have been ongoing since 2023. FDA approval is expected no earlier than 2027.
Mechanism of action
GLP-1 receptor agonism reduces appetite, slows gastric emptying and increases insulin secretion after meals. You already know that from Ozempic. The GIP portion enhances this insulin response and affects fat cell function. tirzepatide uses this pathway.
New to retatrutide is glucagon receptor activation. Glucagon increases basic metabolism and increases lipolysis, i.e. the burning of fat in the liver and fat tissue. Exactly this combination should explain why retatrutide in the previous studies has a stronger effect on body weight than anything else in the incretin space.
The Phase 2 data (Yesstreboff et al., New England Journal of Medicine, 2023) showed a mean weight loss of 24.2 percent in the 12 mg group after 48 weeks. For comparison: semaglutide is around 15 percent, tirzepatide around 20 percent in comparable settings.
Areas of application in research
- Obesity therapy: Main indication in the phase 3 studies TRIUMPH-1 to TRIUMPH-5
- Type 2 diabetes: Glycemic control plus weight reduction
- Non-alcoholic fatty liver disease (NASH): Early data suggest reduction of liver fat
- Cardiovascular endpoints: Triumph Outcomes study ongoing, data expected from 2027
Study situation
Phase 1 data (Coskun et al., Cell Metabolism, 2022) established pharmacological plausibility in humans. Phase 2 provided the spectacular weight data in 2023: 24.2 percent body weight reduction at 12 mg weekly after 48 weeks, with no discernible plateau.
Phase 3 is underway. The TRIUMPH-1 study (obesity without diabetes) and TRIUMPH-2 (obesity with T2D) are in evaluation according to Lilly Pipeline Update Q4 2025. Fully published data are pending.
What remains unclear: long-term compliance beyond two years, rebound effect after discontinuation, safety profile in vulnerable subgroups (older, patients with pre-existing conditions).
Mixing (reconstitution)
retatrutidee is typically offered as lyophilisate in 5-mg or 10-mg vials. Example reconstitution:
- 10 mg Vial with 2 ml bacteriostatic water → final concentration 5 mg/ml
- 10 mg Vial with 1 ml → 10 mg/ml for smaller injection volumes
After mixing, store in the refrigerator (2 to 8 degrees Celsius), stability typically 4 to 6 weeks. Lyophilisateeeee unopened lasts at 2 to 8 degrees 24 months.
Dosage range (research data)
In the Phase 2 studies, the following dose levels were evaluated:
- Start: 2 mg per week, subcutaneous
- Escalation over 4 to 8 weeks
- Maintenance doses: 4 mg, 8 mg, 12 mg per week
- Maximum study dose: 12 mg weekly
Important: These are clinical trial protocols, not a recommendation. Application to humans outside clinical trials is not approved in Germany.
Side effects
The Phase 2 data show a profile similar to other GLP-1 agonists, plus glucagon-specific effects:
- Nausea (most common side effect, 30 to 40 percent in higher doses)
- Vomiting
- Diarrhoea
- Increased heart rate (on average 6 to 8 bpm in the 12-mg group)
- Temporary liver increases
- Possible effects on thyroid gland (analogous to other GLP-1 agonists, box warning expected)
Long-term data on pancreatitis incidence and risk of medullary thyroid carcinoma are pending.
Half-Life and Pharmacokinetics
The elimination half-life is about 6 days. This results in the weekly dosage. Steady-state is reached after 4 to 6 weeks. Bioavailability subcutaneously around 50 to 60 percent.
Administration: exclusively subcutaneous, usually abdomen, thigh or upper arm.
Frequent questions
Is retatrutide stronger than ozempic? In the previous studies, yes, the mean weight loss was about 60 percent higher than for semaglutide in comparable protocols.
When does retatrutide come on the market? According to the current pipeline at the earliest in 2027 in the US, EU approval typically follows 6 to 12 months later.
Is retatrutide already available in pharmacies? No. Outside of clinical studies, the active substance is not marketable in Germany.
How is retatrutidee different from Mounjaro? Mounjaro (tirzepatide) is a dual agonist (GLP-1 plus GIP). retatrutidee adds the glucagon receptor.
Legal status U.S.
As of 2026: retatrutidee has no market approval in Germany, Austria or Switzerland. It is not subject to a pharmacy in the classical sense, because it is simply not an approved medicine. Sales, import and application to humans are subject to the Medicines Act (AMG). Research-use-only distribution exists in a legal grey area and is not intended for self-application.
For purchases from abroad: self-import of non-approved medicines according to §73 AMG is basically prohibited, exceptions for individual imports are narrowly defined. Customs controls are real.
Related compounds
- semaglutideGLP-1 mono-agonist, established (Ozempic, Wegovy)
- tirzepatide: GLP-1/GIP dual agonist, established (Mounjaro, Zepbound)
- survodutideGLP-1/Glucagon dual agonist by Boehringer Ingelheim, Phase 3
- mazdutide: Triple agonist from China (Innovent), market launch there 2024
- CagriSemasemaglutidee plus cagrilintide, Novo-Nordisk combination in phase 3
Note: All information is for research information only. These peptides are not approved as medicines in Germany. The contents do not replace medical advice. Application to humans is not legally covered in Germany.