Mazdutide (Eli Lilly/Innovent), a once-weekly GLP-1/glucagon dual agonist, produced dose-dependent weight loss of 7.3% (3–6 mg dosing strategy), 15.6% (10 mg), and 18.1% (16 mg) versus 0.9% for placebo at week 32 — all comparisons p<0.0001 — in a US Phase 2 trial (NCT06124807) of 179 adults with obesity or overweight without type 2 diabetes, reported as published online August 21, 2026, in The Lancet Diabetes & Endocrinology. Weight loss continued deepening through week 48, reaching up to 22.3% at the highest dose in conference-presentation data. The catch: 20% of participants on 16 mg discontinued treatment because of adverse events, primarily gastrointestinal — the dose–tolerability tradeoff that headline weight-loss numbers alone do not capture.
What the trial was, and where the data now stand
The trade report of the journal publication describes the study — registered as NCT06124807 — as a randomized, double-blind, placebo-controlled Phase 2 trial across 24 US centers, enrolling adults aged 18 to 75 with a BMI of at least 30 kg/m², or 27 to under 30 kg/m² with at least one weight-related comorbidity. None had type 2 diabetes. Participants were assigned to once-weekly subcutaneous mazdutide using one of three dosing strategies — 3–6 mg, 10 mg, or 16 mg — or placebo over 48 weeks, with percent change in body weight at week 32 as the primary endpoint.
These results first circulated publicly at ObesityWeek 2025 in Atlanta (Oral-104), where investigator Stanley H. Hsia presented the dose-finding findings; Healio's meeting coverage reported the same core weight-loss figures at 32 and 48 weeks. The journal publication — titled, per the trade report's reference, "Efficacy and safety of mazdutide in adults with obesity or overweight: a US-based, multicentre, phase 2, randomised, placebo-controlled clinical trial" in The Lancet Diabetes & Endocrinology — is the peer-reviewed anchor for those numbers, a higher evidence tier than a conference oral or a press release. Note that PeptidePrices is working from trade and specialty coverage of that publication, not the primary article itself.
One small discrepancy worth flagging: the conference report described 177 enrolled adults, while the journal report as covered describes 179. It is a minor accounting difference, but a reminder that meeting slides and final publications can differ — the peer-reviewed version is the one to cite.
The dose–response picture, at 32 and 48 weeks
| Regimen | Week 32 weight change | Week 48 weight change | Tolerability signal |
|---|---|---|---|
| Placebo | −0.9% | No change | Treatment-related AEs in 53.2% |
| Mazdutide 3–6 mg | −7.3% | −10.5% | Treatment-related AEs in 78.1% |
| Mazdutide 10 mg | −15.6% | −19.2% | Treatment-related AEs in 76.6% |
| Mazdutide 16 mg | −18.1% | −22.3% | Treatment-related AEs in 82.4%; 20% discontinued, primarily GI |
Week-32 figures and dosing-strategy labels follow the journal report as covered; week-48 figures and AE percentages come from the ObesityWeek 2025 presentation coverage, which labels the lowest arm by its 6 mg target dose. Each mazdutide group began at 1.5 mg once weekly and titrated up.
The headline finding is a steep, statistically clean dose response. All active-dose comparisons versus placebo at week 32 reached p<0.0001, with treatment differences ranging from −6.5 to −17.2 percentage points. At week 48, the loss had deepened rather than leveled: 10.5% (6 mg), 19.2% (10 mg), and 22.3% (16 mg) versus no weight change with placebo (p<.001 across comparisons, per the conference coverage). Investigator Stanley H. Hsia noted that "all of these mazdutide treatment curves did not seem to plateau, suggesting that had we continued treatment beyond 48 weeks, greater degrees of weight loss might actually have been seen."
The magnitude at the top end clears a high bar: at 48 weeks, 52% of the 16 mg group and 49% of the 10 mg group had lost at least 20% of their body weight, versus 3% of placebo; 35% and 29%, respectively, lost at least 25%. Waist circumference fell by 11 cm, 16.7 cm, and 16.6 cm in the three mazdutide groups versus 1.2 cm with placebo. All three mazdutide groups showed significant decreases in HbA1c, fasting glucose, and fasting insulin versus placebo at 48 weeks, and the 10 mg and 16 mg groups also showed significant declines in LDL cholesterol, non-HDL cholesterol, and triglycerides.
The tradeoff: efficacy and discontinuation rose together
The same dose gradient that drove efficacy also drove attrition. Gastrointestinal events were the most frequently reported adverse events with mazdutide and were generally mild to moderate, but treatment discontinuation because of adverse events occurred most often at the top dose — 20% of the 16 mg group, primarily for GI disorders. Hsia described "a subtle imbalance in the incidence of gastrointestinal side effects between the mazdutide 16 mg group and the 10 mg group," evident in nausea, vomiting, and treatment discontinuations.
This is the number that tends to get lost when a 22.3% figure circulates on its own. A mean weight-loss figure measured across a 48-week trial is not the same real-world experience as the raw number suggests if a fifth of the people assigned to that dose could not stay on it. Both numbers are real; the tradeoff between them is the actual clinical — and eventually commercial — question. In PeptidePrices' reading, it mirrors a pattern across the incretin field, where tolerability, not ceiling efficacy, increasingly differentiates candidates.
For balance: serious adverse events were rare — two adults in the 16 mg group and one participant in each of the other two mazdutide groups and the placebo group. No deaths occurred, there were no reported cases of pancreatitis, retinopathy, C-cell hyperplasia, or thyroid malignancies, and mean heart-rate increases were under 10 bpm in all mazdutide groups, with greater increases at higher doses.
Mechanism: what is measured versus what is modeled
Mazdutide is a dual agonist of the GLP-1 and glucagon receptors. Per the trial coverage, GLP-1 receptor activation supports appetite suppression and glucose-dependent insulin secretion, while glucagon receptor activity "can influence energy expenditure and hepatic metabolism" — a mechanism that differs from selective GLP-1 receptor agonists. That second clause deserves precision. The weight loss in this trial is measured; a glucagon-driven energy-expenditure contribution in humans is a mechanistic hypothesis the reported endpoints cannot confirm, since no energy-expenditure measurement is described in the available coverage. Treating "dual agonist therefore burns more calories" as established fact would be a modeled claim dressed up as a measured one.
The dual-agonist design also places mazdutide inside a crowded competitive field of multi-receptor incretin candidates. Our ADA 2026 pipeline roundup on retatrutide, CagriSema, and orforglipron tracks how that broader set is faring on efficacy and tolerability. Critically, no head-to-head trial of mazdutide against retatrutide, semaglutide, or tirzepatide appears in the coverage reviewed here, and cross-trial percentage comparisons are not valid — populations, titration schedules, and durations differ.
Where mazdutide sits in the development program
The US Phase 2 extends an already large program. Earlier Chinese studies include the Phase 3 GLORY-1 trial, which reported 12.55% weight loss with a 6 mg dose in adults with overweight or obesity, and GLORY-2, which evaluated a 9 mg dose in adults with moderate-to-severe obesity. Development has since expanded into type 2 diabetes, metabolic dysfunction-associated fatty liver disease, obstructive sleep apnea, hypertension, and adolescent obesity — a breadth that mirrors the industry pattern we covered in GLP-1s becoming "everything" drugs.
What the US Phase 2 adds specifically, per the trade report, is evidence at substantially higher doses in a US population and — more usefully than any single number — a defined relationship between dose, weight reduction, and tolerability that will shape which dose advances into later-stage studies and long-term weight management.
What this does not mean
- It is not an approval. Mazdutide is investigational. A Phase 2 publication establishes dose-finding evidence, not regulatory approval anywhere, and a filing is not a decision.
- It is not head-to-head evidence. No active comparator appears in the available coverage. Comparing mazdutide's 18.1% or 22.3% to another drug's number from a different trial is not a valid efficacy ranking.
- The population is specific. Results apply to adults with obesity or overweight without type 2 diabetes, n=179, over 48 weeks. Extrapolation to other populations, including people with type 2 diabetes, is not supported by this trial.
- "Did not plateau" is not "keeps working forever." The investigators observed non-plateauing curves through 48 weeks and speculated about longer treatment; that is a trajectory observation within the trial window, not a demonstrated long-term outcome.
- Discontinuation rates are trial-specific. Phase 2 participants received close monitoring and structured titration (all mazdutide groups started at 1.5 mg weekly, per conference coverage); real-world discontinuation patterns can differ in either direction.
- Coverage of a journal article is not the journal article. Our figures come from trade and specialty coverage of the Lancet publication and the ObesityWeek presentation; researchers should consult the primary Lancet Diabetes & Endocrinology article for full methods and statistical detail.
Why the dose–discontinuation tradeoff matters for the pipeline
If the obesity-drug race is heading toward ever-higher efficacy, mazdutide's Phase 2 is a clean illustration of the constraint: the 16 mg arm delivered the largest weight loss and the highest discontinuation rate, while the 10 mg arm delivered 19.2% at week 48 with discontinuations reported less often. For a competitive field where differentiation increasingly hinges on the efficacy–tolerability frontier rather than the efficacy ceiling alone, the most citable number from this trial may end up being 20%, not 22.3%.
For readers tracking the compound class rather than any single asset, the useful frame is that this trial gives the GLP-1/glucagon dual-agonist approach its clearest US-population, dose-stratified datapoint in the coverage reviewed here — and it is explicit about its tolerability limits. That combination is exactly what later-stage trials will be designed around.
FAQs
What did mazdutide's US Phase 2 show?
Dose-dependent least-squares mean weight loss at week 32 of 7.3% (3–6 mg), 15.6% (10 mg), and 18.1% (16 mg) versus 0.9% for placebo (all p<0.0001), in 179 US adults with obesity or overweight without type 2 diabetes, reported as published online August 21, 2026, in The Lancet Diabetes & Endocrinology, with continued loss through week 48.
How much weight did participants lose at 48 weeks?
Per the ObesityWeek 2025 presentation coverage: 10.5% with the 6 mg strategy, 19.2% with 10 mg, and 22.3% with 16 mg, versus no change with placebo. At 48 weeks, 52% of the 16 mg group and 49% of the 10 mg group lost at least 20% of body weight versus 3% of placebo.
Why did 20% of participants stop the 16 mg dose?
Treatment discontinuation because of adverse events occurred most often at 16 mg, affecting 20% of participants, primarily because of gastrointestinal disorders. Investigators described a subtle imbalance in GI side effects — nausea, vomiting, and discontinuations — between the 16 mg and 10 mg groups; most GI events were mild to moderate.
Is mazdutide approved?
No. It remains investigational, with Phase 3 development in China (GLORY-1, GLORY-2) and expanding studies in other populations. A Phase 2 publication does not establish approval anywhere.
Did mazdutide raise energy expenditure in this trial?
No energy-expenditure measurement is described in the available coverage. Glucagon receptor activity "can influence energy expenditure and hepatic metabolism" as a mechanistic hypothesis; the measured endpoints reported were weight, waist circumference, and cardiometabolic labs.
Is mazdutide available as a research-use-only peptide?
No. Mazdutide is an investigational prescription drug in clinical development, not a research-use-only compound, and PeptidePrices does not provide dosing guidance or vendor recommendations for clinical candidates.
How does mazdutide compare to retatrutide?
Mazdutide activates two receptors (GLP-1 and glucagon). No head-to-head trial against retatrutide or any other incretin appears in the coverage reviewed here, so cross-trial weight-loss comparisons should not be read as rankings; our ADA 2026 roundup tracks the broader pipeline separately.
This article is for general informational purposes only and is not medical advice. Talk to a licensed clinician about personal medical decisions. Mazdutide is an investigational drug studied in controlled clinical trials; nothing here should be read as dosing guidance, availability information, or an endorsement of any non-clinical source.
Continue your research
Sources
- Mazdutide Produces Up to 18.1% Weight Loss in US Phase 2 Obesity Trial — Pharmacally (page dated Aug 24, 2026; reports The Lancet Diabetes & Endocrinology online publication of Aug 21, 2026)
- GLP-1/glucagon dual agonist reduces weight across three dosing regimens in obesity — Healio, ObesityWeek 2025 coverage (Nov 18, 2025)
Related PeptidePrices coverage: What the GLP-1 Pipeline Showed at ADA 2026: Retatrutide, CagriSema, Orforglipron and GLP-1s Are Becoming "Everything" Drugs: The New Indications Beyond Weight Loss.