Mazdutide: mechanism, evidence and research limits

Mazdutide (IBI362; LY3305677) is a synthetic, long-acting peptide analogue of the gut hormone oxyntomodulin. Its fatty-acyl modification is intended to prolong exposure, and it is designed to agonise both the GLP-1 receptor (GLP-1R) and glucagon receptor (GCGR). It is therefore a peptide medicine candidate/medicine, not a small molecule, supplement, topical ingredient, hormone replacement, or a blend.

Mazdutide is a dual GLP-1R/GCGR peptide agonist derived from the oxyntomodulin concept, not a generic ‘research peptide’. Chinese randomised trials found placebo-adjusted reductions in body weight and improvements in glycaemic measures in selected adult populations, while gastrointestinal effects were common and long-term clinical-outcome evidence remains incomplete. China’s NMPA approved a specific mazdutide injection for chronic weight management in 2025; this does not establish Australian ARTG registration or validate supplier vials sold as ‘mazdutide’.

Mazdutide is also called IBI362 or LY3305677. The primary literature describes it as a once-weekly synthetic analogue of mammalian oxyntomodulin, with a fatty-acyl moiety added to extend half-life. Oxyntomodulin is relevant because it can engage both GLP-1R and GCGR; mazdutide was developed to retain that dual pharmacology in a longer-acting peptide. [1] [2]

That identity matters when reading marketing. A named active ingredient is not interchangeable with a vial offered by a research-chemical supplier: the human trials used protocol-controlled investigational product, and the Chinese authorisation concerns an NMPA-approved mazdutide injection (brand name 信尔美/Xinermei), not every product that carries the name online. No dilution, storage, sourcing, or self-administration protocol can be inferred from published trial reports. [4] [8]

GLP-1R agonism is the incretin-oriented part of the design. GCGR agonism is the second component. In vitro work cited in the original clinical development paper found IBI362 bound human and mouse GLP-1 and glucagon receptors. The same paper explains the design challenge: glucagon signalling can promote hepatic glucose production, so the balance between the two receptor activities matters rather than ‘more glucagon’ automatically being better. [1]

Mechanistic language needs restraint. In mouse work summarised by the early clinical report, both receptor systems contributed to weight-related effects and energy expenditure increased. That supports a biological rationale, but it does not prove that energy expenditure is the reason for every kilogram lost by people in later trials. The demonstrated human findings are clinical endpoints such as body weight, HbA1c and adverse events. [1] [2] [5]

The pivotal published obesity evidence is GLORY-1, a 610-participant, randomised, double-blind, placebo-controlled phase 3 trial conducted in China. Adults had BMI at least 28 kg/m², or BMI 24 to under 28 kg/m² plus a weight-related condition; diabetes was excluded. At week 32, mean body-weight change was −10.09% with 4 mg and −12.55% with 6 mg, versus +0.45% with placebo. At week 48, the corresponding changes were −11.00%, −14.01% and +0.30%. [5] [7]

Earlier phase 2 evidence provides a useful consistency check, not a substitute for the phase 3 study. In 248 Chinese adults with overweight or obesity, 24 weeks of 3 mg, 4.5 mg or 6 mg mazdutide produced estimated mean changes in body weight of −6.7%, −10.4% and −11.3%, compared with +1.0% on placebo. This dose-ranging result was short and population-specific, and it should not be converted into a personal dosing plan. [4]

Small early studies are especially easy to over-read. A phase 1b trial of 24 Chinese adults tested protocol-defined escalating cohorts up to 9 mg or 10 mg; the primary purpose was safety and tolerability. It reported no serious adverse events and larger average weight reductions than placebo at 12 or 16 weeks, but each active cohort contained only eight people and the authors called for larger, longer trials. [3]

In a 20-week phase 2 trial, 250 Chinese adults with type 2 diabetes inadequately controlled by diet and exercise alone or stable metformin were randomised to mazdutide, placebo, or open-label dulaglutide. Mean HbA1c change with mazdutide ranged from −1.41% to −1.67%, versus +0.03% with placebo; mean weight change was dose-dependent and reached −7.1% with mazdutide. These are trial results in a defined population, not evidence that the drug is suitable for all people with diabetes. [6]

The phase 2 diabetes paper explicitly limits its conclusions: the dulaglutide arm was open label, no non-inferiority framework supported a rigorous comparative glycaemic claim, baseline BMI was relatively low, and all participants were Chinese. A separate 43-person phase 1b study also showed short-term reductions in glycaemic measures and weight, but its 12-week duration and small sample precluded robust efficacy conclusions. [1] [6]

Gastrointestinal effects are the clearest recurring safety signal. In GLORY-1, the most frequent adverse events were gastrointestinal and mostly mild or moderate; trial-regimen discontinuation due to adverse events was 1.5% with 4 mg, 0.5% with 6 mg and 1.0% with placebo. In the 20-week diabetes trial, diarrhoea (36%), decreased appetite (29%), nausea (23%) and vomiting (14%) were among the common mazdutide adverse events. [5] [6]

The phase 2 obesity trial also observed dose-related gastrointestinal symptoms, transient lipase elevations in some participants and heart-rate increases across groups. No investigator-suspected pancreatitis occurred in that 24-week trial, but it was not sized or long enough to rule out uncommon harms or establish cardiovascular-event benefit. The authors specifically said cardiovascular benefits and risks require larger, longer studies. [4]

Study eligibility narrows what can safely be assumed. GLORY-1 excluded, among others, people with diabetes, prior pancreatitis, relevant personal or family thyroid C-cell tumour or MEN2 history, and certain severe mental-health histories. Results therefore do not automatically extend to people outside those trial criteria, during pregnancy, or to combinations with other weight-loss products. [5] [7]

First identify the estimator and time point. GLORY-1’s co-primary endpoints were percentage body-weight change and the proportion reaching at least 5% weight reduction at week 32, analysed with a treatment-policy estimand. The trial continued to week 48 and then included 12 weeks of withdrawal follow-up. A 48-week average does not tell a reader whether an individual will have the average response, tolerate treatment, or retain change after treatment stops. [5] [7]

Second, separate endpoint findings from hard-outcome claims. The GLORY-1 authors reported improvements in prespecified cardiometabolic measures, but the study was not a cardiovascular-outcomes trial. Improvements in laboratory markers, waist measures or blood pressure do not by themselves demonstrate prevention of heart attack, stroke, kidney failure, or liver disease progression. [5]

China’s NMPA approved mazdutide injection for chronic weight management in adults in June 2025, alongside diet control and increased physical activity, for defined BMI thresholds. Innovent subsequently reported NMPA approval for glycaemic control in adults with type 2 diabetes. These are China-specific regulatory events; they are not TGA approval, PBS listing, or an Australian product information document. [8] [9]

In Australia, the ARTG is the public reference database for therapeutic goods that can be supplied, and it can be searched by active ingredient or product name. At the time this record was researched, no public Australian mazdutide product information or ARTG entry was located; readers should re-check the live ARTG because regulatory status can change. If a therapeutic good is not in the ARTG, the TGA describes it as unapproved and says clinician-led Special Access Scheme or Authorised Prescriber pathways may apply in defined circumstances; that is not the same as ordinary retail availability. [10] [11]

The TGA has separately warned that imported, unregistered GLP-1-labelled weight-loss products sold online may be counterfeit, have incorrect or undisclosed ingredients, or lack the quality, safety and efficacy standards of TGA-approved products. That warning is especially relevant to supposed ‘peptide’ vials: a seller’s label cannot establish identity, sterility, concentration, clinical equivalence, or lawful supply. [12]

Mazdutide belongs to the dual GLP-1R/GCGR agonist approach. It should not be described as simply a GLP-1-only agonist, because GCGR agonism is an intentional part of its molecular design. Conversely, the presence of two targets does not establish that mazdutide is clinically superior to every single-target or other multi-target medicine; valid comparisons require appropriately designed head-to-head trials in comparable populations. [1] [6]

The phase 2 diabetes study included open-label dulaglutide as an active reference, but its authors stated that the design did not allow statistically rigorous relative glycaemic-effect conclusions. For that reason, this evidence record does not rank mazdutide against dulaglutide, semaglutide, tirzepatide, retatrutide, or a combination of products. Blends and unvalidated combinations are not supported by a standard combined protocol in the mazdutide trials reviewed here. [6]

Is mazdutide actually a peptide?

Yes. It is a synthetic, fatty-acylated, long-acting peptide analogue of oxyntomodulin, designed to activate GLP-1R and GCGR. It is not a small molecule and not an endogenous hormone replacement product. [1] [2]

Is mazdutide an approved medicine?

It is an approved injectable medicine in China: the NMPA announced approval for chronic weight management in June 2025, and the sponsor later announced an NMPA type 2 diabetes indication. Approval in China does not mean the medicine is approved or ordinarily supplied in Australia. [8] [9] [10]

What is the strongest published weight-management evidence?

GLORY-1 is the strongest published study in this record: a 610-person, randomised, double-blind, placebo-controlled phase 3 trial in Chinese adults with overweight or obesity. Mean weight change at week 48 was −11.00% with 4 mg and −14.01% with 6 mg, compared with +0.30% with placebo. [5] [7]

Are gastrointestinal side effects only a theoretical concern?

No. Gastrointestinal adverse events were common in controlled trials. In the 20-week phase 2 diabetes study, diarrhoea, reduced appetite, nausea and vomiting were among the most frequently reported events. The longer obesity trial likewise described mostly mild-to-moderate gastrointestinal events as most frequent. [5] [6]

Can a research-supplier mazdutide vial be treated as the Chinese approved injection?

No. The NMPA announcement concerns a named, approved injection made by the applicant company. A supplier vial is not made equivalent by using the same ingredient name. The TGA cautions that unregistered GLP-1-labelled internet products may have incorrect or undisclosed ingredients and may not meet approved quality, safety or efficacy standards. [8] [12]

The highest-quality published obesity evidence is phase 3 but was conducted in Chinese adults and does not establish cardiovascular-event prevention, post-withdrawal durability, or effects in every population. Earlier studies were shorter and/or small; the phase 2 diabetes paper has an open-label dulaglutide arm and explicitly rejects a rigorous relative-effect conclusion. The China type 2 diabetes approval claim is sourced to a sponsor announcement in this record, whereas the weight-management approval has an NMPA regulator record. Australian regulatory status should be checked live in the ARTG; this record located no Australian product entry or product information at its research date.

1. [1] A phase 1b randomised controlled trial of a glucagon-like peptide-1 and glucagon receptor dual agonist IBI362 (LY3305677) in Chinese patients with type 2 diabetes. Randomised, placebo-controlled, dose-escalation, multiple-ascending-dose phase 1b study with open-label dulaglutide reference; 43 enrolled Chinese adults with type 2 diabetes; 12-week treatment.
2. [2] IBI362 (LY3305677), a weekly-dose GLP-1 and glucagon receptor dual agonist, in Chinese adults with overweight or obesity: a randomised, placebo-controlled, multiple ascending dose phase 1b study. Randomised, placebo-controlled, multiple-ascending-dose phase 1b study in Chinese adults with overweight or obesity.
3. [3] Safety and efficacy of a GLP-1 and glucagon receptor dual agonist mazdutide (IBI362) 9 mg and 10 mg in Chinese adults with overweight or obesity: a randomised, placebo-controlled, multiple-ascending-dose phase 1b trial. Randomised, placebo-controlled multiple-ascending-dose phase 1b trial; 24 participants across 9 mg and 10 mg cohorts; 12 or 16 weeks of treatment.
4. [4] A phase 2 randomised controlled trial of mazdutide in Chinese overweight adults or adults with obesity. 20-centre, randomised, double-blind, placebo-controlled phase 2 trial; 248 Chinese adults; 24-week primary analysis of 3 mg, 4.5 mg and 6 mg doses.
5. [5] Once-Weekly Mazdutide in Chinese Adults with Obesity or Overweight. Phase 3, randomised, double-blind, placebo-controlled GLORY-1 trial; 610 Chinese adults; 48-week treatment and 12-week withdrawal follow-up.
6. [6] Efficacy and Safety of Mazdutide in Chinese Patients With Type 2 Diabetes: A Randomized, Double-Blind, Placebo-Controlled Phase 2 Trial. Randomised, double-blind, placebo-controlled phase 2 study with an open-label dulaglutide reference; 250 Chinese adults with type 2 diabetes; 20-week treatment.
7. [7] A Study of IBI362 in Participants With Obesity or Overweight (GLORY-1), NCT05607680. Completed Chinese multicentre phase 3, randomised, triple-masked, placebo-controlled trial; 610 participants; two primary week-32 body-weight endpoints.
8. [8] 国家药监局批准玛仕度肽注射液上市 (NMPA approves mazdutide injection for marketing). Chinese NMPA approval announcement, published 27 June 2025.
9. [9] Innovent Announces Mazdutide Received Approval from China's NMPA for Glycemic Control in Adults with Type 2 Diabetes. Company announcement published 19 September 2025, reporting NMPA approval and summarising phase 3 diabetes programme results.
10. [10] Searching the Australian Register of Therapeutic Goods (ARTG). TGA guidance for the public ARTG reference database and search fields.
11. [11] Access an unapproved therapeutic good (health practitioners). TGA guidance on clinician access to unapproved therapeutic goods, updated 28 July 2026.
12. [12] Imported unregistered GLP-1 weight-loss products. TGA safety advisory published 29 September 2025.