Overview
An investigational triple agonist peptide acting at the GIP, GLP-1 and glucagon receptors. It is one of the most closely watched compounds in metabolic research because of the magnitude of body-weight change reported in published phase 2 trials.
Mechanism of Action
Retatrutide is a single synthetic peptide engineered to bind three distinct incretin and metabolic receptors: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and the glucagon receptor (GCGR).
GLP-1 receptor activity is associated in the literature with glucose-dependent insulin secretion, slowed gastric emptying and central appetite signalling. GIP receptor activity is studied for its complementary effects on nutrient handling and adipose tissue.
The addition of glucagon receptor agonism is the distinguishing feature. In published research, glucagon signalling is linked to increased energy expenditure and hepatic lipid mobilisation, which investigators propose may account for the larger weight changes observed relative to single or dual agonists.
A fatty-acid moiety attached to the peptide backbone promotes albumin binding, extending circulating exposure and supporting once-weekly administration in trial protocols.
Areas Being Studied
- Weight management
- Type 2 diabetes glycaemic research
- Hepatic steatosis / liver fat content
- Energy expenditure and metabolic rate
Listing a research area does not imply efficacy, approval, or suitability for any use.
Research Summary
- Phase 2 trial data published in the New England Journal of Medicine in 2023 reported dose-dependent body-weight change over 48 weeks in adults with obesity, with the highest dose arms showing the largest mean reductions recorded to date for an incretin-class investigational agent.
- A parallel phase 2 programme in adults with type 2 diabetes reported reductions in HbA1c alongside body-weight change across the tested dose range.
- Exploratory imaging sub-studies reported reductions in liver fat content in participants with elevated baseline hepatic steatosis.
- Retatrutide remains investigational. It has not completed phase 3 evaluation and is not an approved medicine in any jurisdiction as of publication of the cited literature.
Potential Adverse Effects Reported in Research
- Gastrointestinal events were the most frequently reported findings in trials: nausea, vomiting, diarrhoea and constipation, generally described as mild to moderate and dose-related.
- Reported increases in heart rate at higher dose levels.
- Transient changes in appetite and early satiety were consistently reported.
- Trial protocols used stepwise dose escalation specifically because adverse-event frequency clustered around escalation periods.
Reconstitution Basics
Supplied in research settings as a lyophilised powder. Published handling guidance emphasises gentle mixing rather than shaking, because agitation can denature long-chain peptides.
Bacteriostatic water
Sterile water containing roughly 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth in multi-access vials.
Sterile technique
Laboratory documentation describes disinfecting the stopper, using a fresh sterile needle for each access, and avoiding contact with non-sterile surfaces.
After reconstitution
Solutions are refrigerated, protected from light, and not subjected to repeated freeze–thaw cycles.
This section is educational background on laboratory handling. It is not an instruction or protocol.
Open the reconstitution calculator →Dosing & Reconstitution Guide
Phase 2 trial protocols used a once-weekly subcutaneous schedule with mandatory stepwise escalation. Escalation intervals of four weeks were used specifically because gastrointestinal events clustered around dose increases.
Protocol overview
- Once-weekly subcutaneous administration on the same day each week, reflecting the ~6-day half-life.
- A minimum of four weeks at each step before escalation in the published protocols.
- Escalation was held or reversed when gastrointestinal events were reported.
- Trial protocols paired escalation with hydration and protein intake guidance for participants.
Dosing protocol — standard titration
| Phase | Reported dose | Notes |
|---|---|---|
| Weeks 1–4 | 2 mg weeklyInitiation step used across published arms. | Initiation step used across published arms. |
| Weeks 5–8 | 4 mg weeklyFirst escalation after four weeks at the prior step. | First escalation after four weeks at the prior step. |
| Weeks 9–12 | 8 mg weeklyMid-range step in the trial escalation ladder. | Mid-range step in the trial escalation ladder. |
| Week 13+ | 8–12 mg weeklyHighest published maintenance range in phase 2. | Highest published maintenance range in phase 2. |
Dosing protocol — gradual titration
| Phase | Reported dose | Notes |
|---|---|---|
| Weeks 1–4 | 1 mg weeklyHalf-step initiation reported in tolerability-focused arms. | Half-step initiation reported in tolerability-focused arms. |
| Weeks 5–8 | 2 mg weeklyEscalation only if the prior step was tolerated. | Escalation only if the prior step was tolerated. |
| Weeks 9–16 | 4 mg weeklyExtended plateau before any further increase. | Extended plateau before any further increase. |
| Week 17+ | 6–8 mg weeklySlower ladder reaching a lower ceiling. | Slower ladder reaching a lower ceiling. |
Schedules summarise what appears in published studies, trial protocols or manufacturer documentation. They are reference material, not a recommendation.
Where to Buy Compounds & Supplies
External link. PepDex does not sell products and does not endorse any supplier.
Supplies needed
Lyophilised peptide vial
Sealed vial with an intact stopper and a legible mass label (mg or mcg).
Bacteriostatic water
Sterile water with ~0.9% benzyl alcohol, used where a vial will be accessed more than once. Sterile water for injection is used for single-access work.
Reconstitution syringe
A 1–3 mL syringe with a larger-gauge needle for drawing and transferring solvent.
Insulin syringe (U-100)
Fine-gauge syringe graduated in units; 100 units = 1 mL. Used for accurate small-volume measurement.
Alcohol prep pads
70% isopropyl swabs for disinfecting both vial stoppers before every access.
Sharps container
Rigid, puncture-resistant container for single-use needle disposal.
Refrigeration and light protection
2–8 °C storage plus an opaque box or the original carton for reconstituted vials.
Labels
Date of reconstitution, resulting concentration and compound name on every vial.
Reconstitution steps
- 01
Bring the vial to room temperature
Lyophilised powder is allowed to equilibrate out of the refrigerator before the stopper is pierced, which reduces condensation inside the vial.
- 02
Disinfect both stoppers
The peptide vial and the bacteriostatic water vial are each swabbed with 70% isopropyl alcohol and allowed to air dry.
- 03
Draw the calculated solvent volume
Solvent volume is chosen to produce a convenient concentration — the reconstitution calculator converts vial mass and solvent volume into concentration and syringe units.
- 04
Add the solvent slowly down the vial wall
The stream is directed against the glass rather than onto the powder cake. Peptides are shear-sensitive and direct jetting is avoided.
- 05
Dissolve without shaking
The vial is left to stand, then gently swirled or rolled. Shaking introduces foam and mechanical stress that can denature peptide chains.
- 06
Inspect the solution
Documentation describes checking for a clear, particle-free solution. Cloudiness, visible particulate or discolouration is treated as a failed preparation.
- 07
Label and refrigerate
The vial is labelled with compound, concentration and date, then stored at 2–8 °C protected from light.
Storage instructions
- Before reconstitution: lyophilised powder is kept sealed, dry and away from light; most suppliers specify refrigeration at 2–8 °C, with freezer storage for long-term holding.
- After reconstitution: refrigerated at 2–8 °C and used within the window described in the literature (commonly cited as ~28–56 days refrigerated).
- Protection from light: the vial is kept in its carton or an opaque container; repeated exposure to daylight is avoided.
- Handling: repeated freeze–thaw cycles are avoided, and vials are not left at room temperature between accesses.
- Integrity checks: any solution that becomes cloudy, discoloured or shows particulate is discarded rather than filtered.
Half-Life
~6 days
Pharmacokinetic analyses report a half-life supporting once-weekly dosing intervals in trial design.
Storage
- Before reconstitution
- Lyophilised powder is reported to remain stable when kept frozen or refrigerated in its sealed vial.
- After reconstitution
- After reconstitution, refrigeration between 2–8 °C is the storage condition described in research handling documentation.
- Light protection
- Vials are kept in their carton or otherwise shielded from light; peptide bonds are susceptible to photodegradation.
- Shelf-life considerations
- Reconstituted solutions are generally described as having a limited usable window measured in weeks rather than months.
Frequently Asked Questions
References
- Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial
New England Journal of Medicine, 2023
- Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo- and active-controlled, parallel-group, phase 2 trial
The Lancet, 2023
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Educational reference only. Figures are compiled from published research literature. PepDex does not provide medical advice, dosing recommendations, or instructions for use.