Mazdutide Explained: The Dual GLP-1 and Glucagon Agonist in Two Chinese Trials

Most weight-research peptides in the news act on one receptor or pair GLP-1 with GIP. Mazdutide takes a different pairing: it is described in the trial literature as a once-weekly agonist at both the glucagon-like peptide-1 (GLP-1) receptor and the glucagon receptor (Ji 2023; Gao 2026). This Vial Post explainer covers what public databases list for the molecule and how its two best-known clinical trials were built.

Nothing here is guidance on use in people or animals. The Vial Post covers mazdutide only as a subject of laboratory and literature research.

At a Glance

• Class: GLP-1 and glucagon receptor dual agonist, given once weekly in trials (Ji 2023).
• Formula and mass: PubChem lists C207H317N45O65 and a molecular weight of about 4476 g/mol under CID 167312357 (PubChem: Mazdutide).
• Code names: PubChem synonyms include IBI362, IBI-362 and LY3305677, plus CAS number 2259884-03-0 (PubChem: Mazdutide).

The LY prefix and the IBI prefix point to the two companies whose development codes appear in the record. At roughly 4.5 kDa, mazdutide is far larger than short signalling peptides, which matters for how a lab confirms identity.

The Phase 2 Study

Ji and colleagues published an interim analysis of a randomised, two-part, double-blind, placebo-controlled phase 2 trial run at 20 hospitals in China (NCT04904913). It enrolled overweight adults with a BMI of at least 24 who also had hyperphagia or an obesity-related comorbidity, or adults with a BMI of at least 28. A total of 248 participants were randomised across three active arms and placebo, and the primary endpoint was percentage change in body weight from baseline to week 24 (Ji 2023).

The authors reported that every active arm separated from placebo on that endpoint and listed diarrhoea, nausea and upper respiratory tract infection among the most common adverse events (Ji 2023).

GLORY-2

The phase 3 GLORY-2 trial, published in JAMA in 2026, was double-blind and placebo-controlled and ran at 27 hospitals from December 2023 to November 2025. It enrolled Chinese adults with a BMI of 30 or more, with or without type 2 diabetes, randomised 2:1 to mazdutide or placebo for 60 weeks. Its coprimary outcomes were percentage change in body weight and the share of participants reaching at least 5% weight reduction at week 60. In all, 461 participants received study treatment and were analysed (Gao 2026).

The Vial Post does not restate administered amounts from either paper. Readers who need the figures should go to the primary articles linked below.

Reader Questions

Is mazdutide the same as survodutide? No. Both are described as GLP-1 and glucagon dual agonists, but they are different molecules with separate PubChem records. Our survodutide explainer covers the other one.

Why does the code name matter? Older papers and catalogues may use IBI362 or LY3305677 instead of the INN, so searching all three avoids missing records (PubChem: Mazdutide).

Have the trials been run outside China? The two trials summarised here were both conducted at Chinese hospitals (Ji 2023; Gao 2026).

Lab Note

For a peptide of about 4.5 kDa, mass spectrometry is the practical identity check, and HPLC gives the purity figure. Our guides to HPLC versus mass spec and reading a Certificate of Analysis explain both.

For research and educational use only. This article is not medical advice and does not describe dosing or human use.