RetZama is Zama Biosciences’ designation for retatrutide (development code LY3437943), a synthetic 39-amino-acid peptide built on a GIP scaffold. Molecular formula C221H342N46O68, molecular weight 4731.33 g/mol.
Its defining characteristic is receptor breadth. Retatrutide is a triple agonist, active at the glucose-dependent insulinotropic polypeptide receptor, the glucagon-like peptide-1 receptor, and the glucagon receptor — the third of which sets it apart from the dual agonists that preceded it.
Research context
The progression in this compound class is the useful frame for understanding why retatrutide exists. Single GLP-1 agonism came first, then dual GIP/GLP-1 engagement in tirzepatide, and retatrutide adds glucagon receptor activity on top.
That third receptor is the interesting one. Glucagon receptor agonism is counterintuitive in a metabolic context, since glucagon raises blood glucose — but published work examines its contribution to energy expenditure and hepatic lipid handling, effects not reproduced by incretin agonism alone. How the three activities interact, and what the optimal balance between them is, remains an open research question rather than a settled one.
The sequence carries modified residues and a fatty diacid moiety for albumin binding, which extends plasma half-life sufficiently for weekly-interval protocols in study designs. Consult the manufacturer datasheet for the full modified-residue sequence.
For a fuller treatment of the sequence, published models and technical data, see the retatrutide research guide.
Specification
CAS number 2381089-83-2. Supplied as a white lyophilized powder, soluble in sterile or bacteriostatic water. This batch assayed at 99.31% purity, verified by HPLC and LC-MS at ILS Lab. Available in 5mg, 10mg, 15mg and 20mg presentations.
Handling
Reconstitute with bacteriostatic or sterile water, introducing the diluent against the vial wall and swirling gently rather than shaking. Store lyophilized at −20°C protected from light; refrigerate at 2–8°C once reconstituted.
Ships with a batch-specific Certificate of Analysis. Cross-check the batch ID printed on your vial against the CoA before use — see the guide to reading a CoA if you are unfamiliar with the format.
Frequently asked questions about retatrutide
What is a triple agonist?
A single molecule with agonist activity at three distinct receptors — here GIP, GLP-1 and glucagon. The design problem is that receptor selectivity normally trades off against breadth: engineering one peptide to bind three receptors with useful potency at each is difficult, which is why triple agonists arrived after single and dual agonists rather than alongside them.
Why include glucagon receptor agonism?
It looks contradictory at first, since glucagon raises blood glucose. The research rationale is that glucagon receptor activity is associated in published work with increased energy expenditure and altered hepatic lipid handling — effects not produced by incretin agonism alone. The proposition is that GLP-1 activity offsets the glycaemic effect while the energy expenditure contribution remains. Whether that balance holds across contexts is exactly what the literature is still working out.
Retatrutide or tirzepatide?
Tirzepatide is dual GIP/GLP-1 and has a substantially larger and more mature literature, making it the better-characterised reference compound. Retatrutide adds the glucagon receptor and is correspondingly less studied. Choose tirzepatide for work needing an established comparator; choose retatrutide where glucagon receptor involvement is the research question itself.
How is retatrutide stored and handled?
Bacteriostatic or sterile water for reconstitution. Introduce the diluent against the inner wall of the vial and swirl gently — do not shake or vortex. Store lyophilized at −20°C protected from light; refrigerate at 2–8°C once reconstituted and avoid repeated freeze-thaw cycles. The fatty diacid modification makes this a relatively robust peptide in storage, but mechanical agitation remains the main avoidable risk.
Research use only. Not for human or veterinary use, not for use in diagnostic procedures, and not evaluated by the U.S. Food and Drug Administration.
