History

The molecule originated at Eli Lilly (code LY3305677, also called OXM3). On 21 August 2019, Innovent Biologics licensed it for development in China (code IBI362), with Lilly retaining ex-China rights. First human data appeared in 2022 (Phase 1b, eClinicalMedicine), followed by Phase 2 obesity and diabetes trials in 2023. The pivotal Phase 3 GLORY-1 weight-loss trial was published in the New England Journal of Medicine in 2025. China's NMPA approved mazdutide for chronic weight management on 27 June 2025 and for type 2 diabetes on 18 September 2025, making it the first GCG/GLP-1 dual agonist approved anywhere.

Mazdutide is an injectable drug for weight loss and type 2 diabetes that activates two metabolic hormone receptors at once. Unlike most of the attention-grabbing GLP-1 compounds, it is not stuck at the press-release stage: it has a published Phase 3 trial in a major journal and is actually approved in one country. The catch is that the country is China, the trials were funded and partly authored by the developer, and there is still no approval, no long-term outcome data, and very little non-Chinese evidence anywhere else in the world.

What it is

Mazdutide is a once-weekly subcutaneous peptide, structurally a long-acting analogue of oxyntomodulin — a naturally occurring gut hormone that hits both the GLP-1 and glucagon receptors. It has been engineered (lipidated for once-weekly dosing) from that scaffold. Its molecular formula is C₂₁₀H₃₂₂N₄₆O₆₇, with a molar mass of roughly 4,563 g/mol and CAS number 2259884-03-0. No full amino-acid sequence has been published in a primary source, so anyone stating a precise sequence is guessing.

The “dual agonism” is the whole point. The GLP-1 arm does the familiar work seen in drugs like semaglutide: glucose-dependent insulin release, slowed gastric emptying, and appetite suppression. The glucagon arm is the differentiator — glucagon-receptor activation is thought to raise energy expenditure and increase fat-burning in the liver, potentially adding weight loss and liver-fat reduction beyond what GLP-1 alone delivers. But glucagon-receptor agonism cuts both ways: glucagon naturally raises blood glucose and heart rate. Trial data show net glucose lowering, but the heart-rate increase is real and dose-dependent, and it is the clearest safety theme across the studies.

The claims

Marketing and forum discussion frame mazdutide as a next-generation GLP-1 that beats semaglutide and adds liver benefits the older drugs lack. The approved and well-studied uses are chronic weight management and glycemic control in type 2 diabetes. Weaker, more exploratory claims involve liver-fat reduction (MASLD/MASH) and broad cardiometabolic improvements — blood pressure, lipids, uric acid, waist circumference — which appear as secondary endpoints rather than primary outcomes.

Outside China, mazdutide is also sold by research-chemical and “peptide” vendors riding the GLP-1 wave. Those products are not approved, not quality-controlled for human use, and their claims are not regulated. Treat vendor pages as marketing, not evidence.

The evidence

The honest framing first: nearly all of the pivotal data come from Chinese populations, in trials sponsored by Innovent, with Innovent employees among the authors. That does not make the data wrong, but it is a structural limitation that runs through the entire evidence base.

The early work was small. A 2022 Phase 1b trial (eClinicalMedicine, n=24) used dose-escalation cohorts and reported about 11.7% weight loss in the 9 mg cohort versus 1.8% on placebo at week 12 — but it also recorded heart-rate increases of up to about +17.4 bpm at 9 mg, the first clear hint of the cardiac signal. Two Phase 2 trials in 2023 firmed things up: an obesity trial (Nature Communications, n=248) found weight loss of roughly 6.7% to 11.3% across doses over 24 weeks, and a diabetes trial (Diabetes Care, n=250) showed HbA1c reductions comparable to or better than the active comparator dulaglutide, with more weight loss.

The pivotal weight-loss trial is GLORY-1, published in the New England Journal of Medicine in 2025 (n=610 Chinese adults, 48 weeks). At 6 mg it produced about 14.8% mean weight loss versus roughly 0.5% on placebo, with around 83% of participants losing at least 5% of body weight. It also reported a large reduction in liver fat. (Reported figures differ by subgroup — Innovent’s own summary cites up to about −80% in people with high baseline liver fat — so the liver benefit is best described qualitatively rather than as one precise number.) Blood pressure, lipids, uric acid, transaminases, and waist circumference all improved, and the trial reported no signal of increased cardiovascular risk, though it was not designed to measure that.

For diabetes, the Phase 3 DREAMS program matters because two of its trials — DREAMS-1 (monotherapy) and DREAMS-2 (versus dulaglutide) — were published back-to-back in Nature on 17 December 2025. DREAMS-1 was the registrational basis for China’s diabetes approval. This is genuine peer-reviewed Phase 3 evidence, not a press release.

Other striking figures remain at the press-release stage and should be treated cautiously. GLORY-2 (n=462, 60 weeks) reported mean weight loss of about 18.55% overall at the higher 9 mg dose, and about 20.08% in participants without diabetes — but it is not peer-reviewed. DREAMS-3, a head-to-head versus semaglutide, reported superiority on a combined glucose-and-weight endpoint, but it too remains conference- and press-release-level. There is also a 2025 animal study (eBioMedicine) suggesting cognitive benefits in diabetic mice; that is preclinical and not a basis for any human claim.

What is missing is as important as what exists. There is no published cardiovascular-outcome trial and no hard-outcome or mortality data — only metabolic surrogates and safety signals. The pivotal efficacy is essentially all from Chinese populations, so generalizability to other groups is unproven. Long-term durability and weight regain after stopping are not characterized in published long-term data, and there is no published head-to-head against tirzepatide. The sponsor funded the trials and employed multiple authors throughout.

Safety and side effects

The most common adverse effects are gastrointestinal — nausea, diarrhea, vomiting, and reduced appetite — mostly mild to moderate and concentrated during dose escalation. In the Phase 2 diabetes trial, diarrhea occurred in about 36% of participants, nausea in 23%, and vomiting in 14%.

The signature mechanism-linked concern is heart rate. The increase is dose-dependent, reaching up to about +17.4 bpm at 9 mg in the small Phase 1b study, and was more modest at the 4 and 6 mg doses in GLORY-1. Anyone with cardiac risk should weigh this carefully, and there is no cardiovascular-outcome trial to lean on. Hypoglycemia ran around 10% in the Phase 2 diabetes trial (versus 8% on placebo), with no severe cases reported. On the liver, published trials point toward improvement rather than harm. The real unknowns are long-term multi-year safety, the pancreatitis, gallbladder, and thyroid signals seen as class concerns for incretin drugs, pregnancy safety, and how the drug behaves in non-Chinese populations.

Legal and regulatory status

In China, the NMPA approved mazdutide for chronic weight management on 27 June 2025 — billed as the world’s first GCG/GLP-1 dual agonist approved for weight loss — and for type 2 diabetes glycemic control on 18 September 2025. A supplemental application for the 9 mg dose was accepted for NMPA review in November 2025 and is pending.

In the United States, mazdutide is not approved. It is investigational, with Lilly holding ex-China rights at an earlier development stage. Any “FDA timeline” you see comes from commercial or secondary sites, not the FDA, and is speculative. Outside China there is no legal, approved consumer product; anything sold online as a “research chemical” or unapproved peptide is unregulated, of unverified identity and purity, and not legal for human use in the US or EU.

For athletes: mazdutide is not named on the WADA Prohibited List, and the GLP-1 class is not banned — semaglutide is on WADA’s Monitoring Program (watched, not prohibited). By class analogy mazdutide is currently permitted in sport, but the category is under watch and WADA has funded detection-method development for GLP-1 drugs, so the status could change.

Bottom line

Mazdutide has more real, peer-reviewed human evidence behind it than most of the buzzy GLP-1 compounds — a Phase 3 NEJM weight-loss trial, two Phase 3 diabetes trials in Nature, and actual regulatory approval in China for two indications. That is well past “early.” But it falls short of “Strong human” because the pivotal efficacy is confined to Chinese, sponsor-funded populations, the most eye-catching weight-loss numbers (the 9 mg ~20% result and the win over semaglutide) are still press-release-level, there is no published cardiovascular-outcome or long-term safety trial, and there is no FDA or EMA approval. Outside China, nothing sold as mazdutide is approved or quality-controlled. Nothing here is medical advice.

Evidence grade: Preliminary human.

Mazdutide: real Phase 3 data, but almost all of it from China