Mazdutide's US path stays theoretical as Lilly publishes a Phase 2

Mazdutide, a once-weekly GLP-1/glucagon dual agonist discovered by Eli Lilly, remains approved only in China even after Lilly published US Phase 2 results in The Lancet Diabetes and Endocrinology on August 21, 2026 ^[1]. No Phase 3 program and no FDA filing have been announced ^[1][2].

The drug has an unusual corporate history. Lilly discovered the molecule, known internally as LY3305677, and licensed Greater China rights to Innovent Biologics in August 2019 ^[1]. Innovent runs the Chinese trials, manufactures for that market and sells the product under the brand name Xinermei ^[1]. China's National Medical Products Administration approved it for chronic weight management on June 27, 2025, and for glycemic control in adults with type 2 diabetes on September 19, 2025 ^[1][2].

What the data show

The Chinese obesity approval rested on GLORY-1, a 48-week trial in 610 Chinese adults with a BMI of 28 or higher, or 24 or higher with a weight-related condition ^[1]. Mean weight change was -11.00 percent at 4 mg and -14.01 percent at 6 mg, versus +0.30 percent with placebo ^[1]. At week 48, 35.7 percent of the 4 mg group, 49.5 percent of the 6 mg group and 2.0 percent of the placebo group had lost at least 15 percent of body weight ^[1]. Discontinuation for adverse events was 1.5 percent, 0.5 percent and 1.0 percent, respectively ^[1]. Innovent's own June 27, 2025 release described the results using a different statistical approach, reporting 12.0 percent and 14.8 percent versus 0.5 percent — a reminder that the same trial can yield different headline numbers depending on how missing data and treatment interruptions are handled ^[1].

A larger-dose Chinese trial, GLORY-2, tested 9 mg in 462 adults with a BMI of 30 or higher over 60 weeks and reported -18.55 percent overall and -20.08 percent in participants without type 2 diabetes; Innovent said in November 2025 that it planned a Chinese application for the 9 mg dose ^[1].

The newly published US study is much smaller. It enrolled 179 adults, ran from November 2023 to July 2025, and reported 32-week weight change of -7.3 percent at 3 to 6 mg, -15.6 percent at 10 mg and -18.1 percent at 16 mg, compared with -0.9 percent on placebo ^[1]. Tolerability at the top dose was a concern: 20 percent of the 16 mg group stopped because of adverse events, against 1.5 percent or less in the Chinese 4 mg and 6 mg arms ^[1]. Across the program, nausea, diarrhea and vomiting were the most common side effects, concentrated during dose escalation ^[1].

Why it matters for patients

A Phase 2 result, even a strong one, is several years and several thousand patients away from a US prescription. Lilly has not said whether it will run a Phase 3 trial of mazdutide in the United States ^[1][2]. The company's late-stage US obesity work centers on tirzepatide, already approved as Zepbound and Mounjaro, and retatrutide, a triple agonist that reported up to 30.3 percent average weight loss at two years in the Phase 3 TRIUMPH-1 trial and has an FDA submission planned for the first quarter of 2027 ^[1][2].

Because mazdutide is not part of any FDA-approved drug, no US pharmacy can lawfully compound or dispense it ^[1]. Sellers marketing it online are operating outside the approval system: the FDA has warned companies selling mazdutide labeled "for research purposes," and a December 10, 2024 warning letter to Summit Research Peptides named mazdutide among unapproved drugs sold as research chemicals ^[1].

Several questions relevant to American patients are simply unanswered. The pivotal efficacy and safety data come from Chinese adults, whose average BMI at obesity diagnosis is lower than in US populations, so the same percentage loss translates to fewer absolute pounds ^[1]. No large cardiovascular outcomes trial for mazdutide has been published, and the long-term liver effects of the glucagon component have not been studied as deeply as semaglutide's ^[1].

What happens next

As of September 5, 2026, mazdutide was not approved by the FDA or, based on available reporting, by any regulator outside China ^[1]. A US and Argentina Phase 2 master protocol was still recruiting ^[1]. Whether Lilly advances the molecule in the US, and on what timeline, has not been disclosed ^[1][2].