Mazdutide (IBI362, LY3305677) is a once-weekly analog of oxyntomodulin (OXM), the gut hormone that turns on both the glucagon-like peptide-1 receptor (GLP-1R) and the glucagon receptor (GCGR). Eli Lilly designed it and Innovent licensed it for China. China’s National Medical Products Administration (NMPA) approved it in 2025 for chronic weight management, and it is not an FDA-approved drug.

TL;DR

  • Oxyntomodulin backbone, fatty-acyl chain. That chemistry is why a short gut peptide can be injected once a week (Jiang et al., 2022).
  • Two jobs. The GLP-1 arm cuts intake. The glucagon arm is the energy-expenditure and liver story.
  • Phase 2 obesity: mean weight change at 24 weeks was -11.3% at 6 mg versus +1.0% on placebo (Ji et al., 2023).
  • GLORY-1 (NEJM): treatment-policy mean change at 48 weeks was -14.01% at 6 mg versus +0.30% on placebo (Ji et al., 2025).
  • NMPA, not FDA. China approved the licensed product for overweight or obesity. A research-catalog vial is not that product.

What is mazdutide, and how is it different from semaglutide?

Most weight-loss peptide talk still starts at one receptor. Semaglutide is a GLP-1 agonist and tirzepatide adds GIP. Mazdutide adds glucagon, using the OXM template rather than a GLP-1 backbone.

Oxyntomodulin is the natural precedent. Native OXM already hits both receptors but is too short-lived to be a weekly drug, which is why analog work exists at all (Day et al., 2009).

Mazdutide is a synthetic mammalian OXM analog with a fatty-acyl side chain for albumin binding. In the Chinese type 2 diabetes phase 1b, absorption peaked around 72 hours and half-life spanned 6.1 to 28.1 days, the pharmacokinetic case for weekly dosing (Jiang et al., 2022).

It is not survodutide, the Zealand and Boehringer glucagon/GLP-1 peptide, which is still investigational. Mazdutide is the OXM analog China licensed. Semaglutide versus tirzepatide is a separate comparison, and the chemistry primer is on Peptides 101.

Why add glucagon agonism to a GLP-1 peptide?

GLP-1 receptor agonism slows gastric emptying, raises satiety, and lowers calorie intake. That is the familiar incretin half.

Glucagon receptor agonism is the other half. In overweight humans, native OXM reduced energy intake and raised energy expenditure in a randomized trial (Wynne et al., 2006). In rodents, balanced GLP-1/glucagon co-agonists produced larger weight cuts than GLP-1 activity alone (Day et al., 2009).

The liver is the glucagon story clinicians care about. GCGR sits on hepatocytes, so dual agonism is supposed to move hepatic fat more directly than GLP-1 alone, which is why GLORY-1 reported liver-fat imaging as well as scale weight.

Glucagon can raise glucose. Pairing it with GLP-1 is the design bet: keep the metabolic burn without losing glycemic control.

What did the Chinese phase 2 obesity trial actually measure?

Ji and colleagues randomized 248 Chinese adults with overweight or obesity to weekly 3 mg, 4.5 mg, 6 mg, or placebo for 24 weeks. Mean age was 35.5 years, mean weight was 89.4 kg, and mean BMI was 31.8.

Study Who was enrolled Design Main finding
Ji 2023, obesity phase 2 248 Chinese adults, mean BMI 31.8 Weekly 3, 4.5, or 6 mg vs placebo, 24 weeks Mean weight -11.3% at 6 mg vs +1.0% placebo
Ji 2025, GLORY-1 610 Chinese adults, mean BMI 31.1 Weekly 4 or 6 mg vs placebo, 48 weeks Treatment-policy mean weight -14.01% at 6 mg vs +0.30% placebo

Primary analysis at week 24: -6.7%, -10.4%, and -11.3% across the three mazdutide doses, versus +1.0% on placebo. Placebo-adjusted differences were -7.7%, -11.4%, and -12.3% (Ji et al., 2023).

Responder rates were not subtle. At 6 mg, 80.3% lost at least 5% and 50.8% lost at least 10%, versus 4.8% and 0% on placebo. Completion was high: 224 of 248 (90.3%) reached week 24.

Gastrointestinal events (diarrhea, nausea, vomiting) were the main tolerability story, mostly mild or moderate and dose-related. Heart rate rose 5.4 to 8.8 beats per minute on mazdutide versus 4.8 on placebo.

What did GLORY-1 report in the New England Journal of Medicine?

GLORY-1 enrolled 610 Chinese adults with obesity (BMI at least 28) or overweight (BMI 24 to under 28) plus a weight-related comorbidity. Mean baseline weight was 87.2 kg and mean BMI was 31.1. Doses were 4 mg, 6 mg, or placebo weekly for 48 weeks.

Read the estimand. The treatment-policy number keeps people in the average after dropout. The efficacy number estimates the effect if people stayed on drug.

At week 48, treatment-policy mean weight change was -11.00% at 4 mg, -14.01% at 6 mg, and +0.30% on placebo. Efficacy-estimand figures were -12.05%, -14.84%, and -0.47% (Ji et al., 2025).

At 6 mg, 49.5% lost at least 15% of body weight on the treatment-policy analysis, versus 2.0% on placebo. Waist fell 10.72 cm versus 1.41 cm.

Liver fat moved with the scale. In participants whose baseline liver fat was at least 10%, mean change at week 48 was -65.85% at 4 mg, -80.24% at 6 mg, and -5.27% on placebo.

GI events again led the safety table and were mostly mild or moderate. Mean heart-rate change at week 48 was 2.6 beats per minute on both licensed doses.

Is mazdutide an FDA drug, and what is a catalog vial?

NMPA approved mazdutide in 2025 for chronic weight management in Chinese adults with obesity (BMI at least 28) or overweight (BMI at least 24) plus a comorbidity (Innovent, 2025).

FDA has not approved mazdutide. The GLORY program was run in Chinese adults, using Chinese BMI cutoffs that sit below typical U.S. obesity thresholds. Those data do not automatically transfer to a U.S. label.

A research-chemical vial labeled “mazdutide” or “IBI362” is not the Innovent product in GLORY-1. Sequence, salt, purity, and sterility are the usual catalog gaps. Licensed incretin products, when they exist, show up in pharmacy and telehealth channels on the provider directory and price index.

Handling education lives on the reconstitution guide and the calculator. Clinician voices on metabolic peptides are collected on experts.

Bottom line: Mazdutide is a real oxyntomodulin analog with Chinese phase 2 obesity data, a NEJM phase 3 readout, and an NMPA weight-management label. It is a different receptor story from semaglutide. It is not an FDA-approved drug, and a research vial is not the trial product.

Educational only. Not medical advice. Not a recommendation to use mazdutide, IBI362, LY3305677, or any research-grade glucagon or GLP-1 peptide.