Trust signals
> Reviewed by FormBlends Medical Team · Last updated May 2026 · 11 sources cited
Key Takeaways
- Both molecules were discovered by Eli Lilly; both target the glucagon system in addition to GLP-1
- Mazdutide is a dual agonist (GLP-1 + glucagon); retatrutide is a triple agonist (GLP-1 + GIP + glucagon)
- Mazdutide phase 3 in China produced ~14.4% mean weight loss; retatrutide phase 2 globally produced ~24%
- Mazdutide is approved in China only; retatrutide is investigational in the U.S. and elsewhere
- Neither is FDA-approved. FormBlends does not sell or supply retatrutide or mazdutide
Direct answer
Mazdutide and retatrutide both come from Eli Lilly's metabolic discovery program. Mazdutide is a dual agonist of GLP-1 and glucagon receptors, licensed to Innovent Biologics for China, where it was approved for obesity in 2025. Retatrutide is a triple agonist that adds GIP receptor activity, in phase 3 trials globally. Retatrutide produced approximately 24% mean weight loss in phase 2; mazdutide produced approximately 14.4% in phase 3 (DREAMS-1, China). Neither is FDA-approved.
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- The two Lilly molecules and their pathways
- Mechanism comparison: GLP-1/glucagon vs GLP-1/GIP/glucagon
- Headline weight-loss numbers
- Trial design differences
- Side-effect profiles
- Regulatory and access status
- Why mazdutide is China-only while retatrutide is global
- The added value of GIP receptor activity
- Long-term outlook
- The contrary view: is the triple-agonist strategy worth the complexity?
- FAQ
- Sources
The two Lilly molecules and their pathways
Eli Lilly's metabolic peptide portfolio includes several investigational molecules at varying stages. Two of them, mazdutide and retatrutide, target the glucagon system in different ways.
Mazdutide (LY3305677). A GLP-1/glucagon dual agonist. Licensed to Innovent Biologics in 2019 for development and commercialization in Greater China. Approved by China's NMPA for obesity in 2025 under the brand Sineipasy.
Retatrutide (LY3437943). A GLP-1/GIP/glucagon triple agonist. Developed by Lilly directly. In phase 3 (TRIUMPH program) for obesity, type 2 diabetes, MASH, and obstructive sleep apnea. Not approved anywhere as of May 2026.
Both molecules were designed to leverage the glucagon system's effects on energy expenditure and hepatic fat. Retatrutide adds the GIP component already validated in tirzepatide; mazdutide does not.
Mechanism comparison: GLP-1/glucagon vs GLP-1/GIP/glucagon
| Receptor | Mazdutide | Retatrutide |
|---|---|---|
| GLP-1 | Yes | Yes |
| GIP | No | Yes |
| Glucagon | Yes | Yes |
What each receptor contributes:
- GLP-1: appetite suppression, slowed gastric emptying, enhanced meal-stimulated insulin secretion
- GIP: incretin amplification, additional appetite effects, glycemic improvement; the precise functional contribution is still debated
- Glucagon: increased energy expenditure, hepatic fatty acid oxidation, reduced hepatic fat storage
The hypothesis behind the triple agonist: by hitting all three receptors, retatrutide recruits multiple distinct mechanisms simultaneously, producing additive or near-additive effects. The 24% phase 2 weight loss is consistent with this hypothesis. The dual agonist mazdutide, with one fewer receptor in play, produces somewhat less.
Headline weight-loss numbers
| Drug / dose | Trial | Phase | Population | Duration | Mean weight loss |
|---|---|---|---|---|---|
| Retatrutide 12 mg | Jastreboff 2023 | Phase 2 | U.S. adults with obesity | 48 weeks | ~24% |
| Retatrutide 8 mg | Jastreboff 2023 | Phase 2 | U.S. adults with obesity | 48 weeks | ~22% |
| Mazdutide 9 mg | DREAMS-1 | Phase 3 | Chinese adults with obesity | 48 weeks | ~14.4% |
| Mazdutide 6 mg | DREAMS-1 | Phase 3 | Chinese adults with obesity | 48 weeks | ~12% |
The cross-trial comparison is unfair on multiple dimensions:
- Retatrutide's number is phase 2; mazdutide's is phase 3. Phase 2 numbers tend to overstate phase 3 results
- Retatrutide enrollment was U.S. adults; mazdutide enrollment was Chinese adults with lower mean baseline BMI
- The cohorts had different lifestyle interventions and adherence patterns
The honest conclusion is that retatrutide appears more potent at the molecular level, but the gap is exaggerated by the cross-trial comparison. Retatrutide phase 3 results, when they read out, may show a different number.
Trial design differences
The trials differ in ways that affect efficacy interpretation:
| Feature | Mazdutide DREAMS-1 | Retatrutide phase 2 |
|---|---|---|
| Population | Chinese adults, BMI ≥28 | U.S. adults, BMI ≥30 or 27+ with comorbidity |
| Baseline mean BMI | ~31 | ~37 |
| Trial phase | Phase 3 | Phase 2 |
| Duration | 48 weeks | 48 weeks |
| Sample size | ~600 | ~338 |
| Lifestyle counseling | Standard for region | Standard U.S. protocol |
Baseline BMI matters because higher-BMI populations tend to lose more absolute weight, and the percentage loss often runs higher in obesity-trial populations (BMI 35+) than in overweight populations. Mazdutide's lower baseline BMI is one reason its percentage weight loss is lower than retatrutide's.
Phase 3 vs phase 2 also matters. Phase 2 trials use smaller, more selected populations and tighter protocols, which tend to produce somewhat better numbers than phase 3.
Side-effect profiles
Both drugs produce GI-dominant adverse-event patterns consistent with the GLP-1 class. Specific observations:
| Event | Mazdutide 9 mg (DREAMS-1) | Retatrutide 12 mg (phase 2) |
|---|---|---|
| Nausea | Common, dose-dependent | ~50-60% |
| Diarrhea | Moderately common | ~30-40% |
| Vomiting | Common in titration | ~25-30% |
| Discontinuation for AEs | Comparable to GLP-1 class | Higher at maximum doses |
Retatrutide produces higher GI rates at its highest doses, consistent with stronger receptor engagement. Mazdutide's profile in the DREAMS-1 trial was more comparable to semaglutide than to retatrutide.
Specific safety dimensions:
- Heart rate: modest increase with both
- Glycemic effects: no net hyperglycemia in either trial; glucagon's acute effects offset by GLP-1
- Hepatic safety: favorable signals in both
- Cardiovascular: outcomes data not yet available for either at the scale of semaglutide's SELECT
Regulatory and access status
| Region | Mazdutide | Retatrutide |
|---|---|---|
| China (NMPA) | Approved for obesity (2025) | Not approved |
| U.S. (FDA) | Not approved; no disclosed plan | Investigational, phase 3 ongoing |
| EU (EMA) | Not approved | Investigational |
| Other major markets | Generally not approved | Generally investigational |
For a U.S. patient, both drugs are inaccessible through legitimate channels. The relevant U.S.-approved options are tirzepatide (Zepbound) and semaglutide (Wegovy).
Why mazdutide is China-only while retatrutide is global
This is a strategic question for Eli Lilly more than a biological one.
Reason 1: Portfolio differentiation. Lilly's U.S. obesity flagship is tirzepatide. Retatrutide is being developed as the next-generation U.S. product. Adding mazdutide to the U.S. portfolio would create direct internal competition without clearly differentiated indication.
Reason 2: China-specific clinical development. The DREAMS program was designed and conducted for the Chinese regulatory pathway. Repurposing it for FDA submission would require substantial additional U.S.-population data.
Reason 3: Partnership economics. Lilly licensed China rights to Innovent in part to accelerate the Chinese market entry. Lilly's economic interest is in the licensing revenue plus its own retatrutide pipeline, not in competing with itself.
Reason 4: Market segmentation. Different populations have different obesity drug needs. The Chinese market may be best served by a dual agonist tuned to local patient phenotypes; the U.S. market may be better served by a more potent triple agonist.
None of this is a value judgment. Mazdutide is a real and effective drug. Retatrutide is more potent in early data. Both are legitimate paths within Lilly's broader portfolio strategy.
The added value of GIP receptor activity
The functional impact of GIP receptor activity in retatrutide and tirzepatide has been a research debate. Preclinical work has produced conflicting evidence about whether GIP receptor agonism, antagonism, or biased signaling drives the weight-loss enhancement.
What is clear from clinical data:
- Drugs that activate both GLP-1 and GIP receptors (tirzepatide, retatrutide) produce more weight loss than GLP-1 alone (semaglutide)
- The magnitude of enhancement is substantial: tirzepatide 15 mg ~22.5% vs semaglutide ~14.9%
- Retatrutide adding GIP to a GLP-1/glucagon backbone pushes weight loss to ~24% in phase 2
- Mazdutide without GIP plateaus lower
The simple framing: GIP receptor activity adds weight-loss benefit even though the molecular details are debated. Mazdutide is essentially "what you get without GIP." Retatrutide is "what you get with all three."
Long-term outlook
The expected trajectory through 2027-2028:
- Mazdutide: continued growth in the Chinese market; possible expansion to other Asian markets via Innovent partnerships; no announced U.S. plans
- Retatrutide: phase 3 readouts in waves through 2025-2026; possible FDA filing in 2026-2027; potential approval in 2027 if data supports
- Direct competition: when retatrutide launches in the U.S., it would compete with Zepbound, Wegovy, and CagriSema for share
- Cross-market: Lilly may eventually develop mazdutide for non-China markets if strategic conditions change
The contrary view: is the triple-agonist strategy worth the complexity?
The argument for sticking with dual agonists like mazdutide:
Argument 1: Diminishing returns. Going from GLP-1 alone (~15%) to dual GLP-1/GIP (~22%) was a large gain. Going from dual to triple (~24%) is a smaller gain. The added complexity may not be worth the marginal weight loss.
Argument 2: Side-effect compounding. Each additional receptor adds GI signaling. Retatrutide at maximum dose has higher discontinuation rates than tirzepatide or semaglutide.
Argument 3: Liver and metabolic safety. Glucagon receptor activation has theoretical risks. Adding it to a dual GLP-1/GIP backbone (rather than to GLP-1 alone) compounds the unknowns.
Argument 4: Regulatory complexity. A triple agonist requires more comprehensive safety characterization across each receptor's effect. The regulatory bar is higher.
The counterargument: for patients seeking maximum weight loss or with refractory obesity, the triple agonist's incremental benefit may matter. Patient phenotyping will likely determine which drug suits which patient.
Decision framework
If you are a U.S. patient: neither drug is available. The relevant options are FDA-approved Zepbound, Wegovy, and the soon-to-launch CagriSema (if approved).
If you live in China: mazdutide (Sineipasy) is an approved option. Local clinicians can prescribe it.
If you are evaluating Lilly's pipeline: retatrutide is the Lilly molecule to watch for the U.S. market; mazdutide is a China-focused product.
If you are considering "research peptide" versions of either: don't. The products are not the clinical formulations. Quality and identity are unverifiable.
FAQ
Are mazdutide and retatrutide the same drug? No. Different molecules and different receptor profiles.
Which produces more weight loss? Retatrutide in phase 2 trials. The phase 3 comparison is not yet possible.
Which is safer? Neither has a clear safety advantage. Both are within the GLP-1 class adverse-event range, with retatrutide showing higher GI rates at maximum doses.
Can I combine them? No. Combining incretin-class drugs is not supported by any evidence and predictably stacks side effects.
Why is mazdutide only in China? Lilly licensed China rights to Innovent and is developing retatrutide for other markets.
Will retatrutide be approved in the U.S. before mazdutide? Almost certainly, given mazdutide has no announced U.S. development plan.
Is one cheaper than the other? Mazdutide is currently priced for the Chinese market. Retatrutide pricing is unknown until launch.
Which has more cardiovascular data? Neither has substantial cardiovascular outcomes data yet.
Which has better diabetes data? Both are being tested in type 2 diabetes. Mazdutide has Chinese phase 3 diabetes data; retatrutide has earlier-phase data.
Is mazdutide better for liver disease? Both molecules' glucagon component should affect hepatic fat. Retatrutide has more developed liver-disease evidence in U.S. trials.
Can I get retatrutide if I qualify for a trial? Yes. ClinicalTrials.gov lists active retatrutide trials. Enrollment requires meeting site-specific criteria.
Related guides
- Retatrutide vs Mazdutide: Triple Agonist vs Dual Agonist, Lilly vs Innovent
- What Is Mazdutide? China's New Obesity Drug, Explained for U.S. Readers
- Retatrutide vs Survodutide: Dual vs Triple Agonist Comparison 2026
- Is Retatrutide Legal? The Investigational-Drug Gray Area in 2026
- Retatrutide vs Tesofensine: Investigational Drugs Comparison 2026
- What Is Retatrutide? The Triple-Agonist Obesity Drug Explained
Sources
- Jastreboff AM et al. Triple-Hormone Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. New England Journal of Medicine. 2023.
- Ji L et al. Mazdutide for chronic weight management in Chinese adults (DREAMS-1). 2024-2025.
- Eli Lilly. Annual Report Pipeline Disclosure. 2024.
- Innovent Biologics. NMPA Approval for Sineipasy. 2025.
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). NEJM. 2022.
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). NEJM. 2021.
- le Roux CW et al. Survodutide for obesity (phase 2). Lancet. 2024.
- Coskun T et al. LY3437943 (retatrutide), a novel triple agonist: preclinical pharmacology. Cell Metabolism. 2022.
- Eli Lilly. TRIUMPH Phase 3 Program Disclosures. 2024-2025.
- National Medical Products Administration (China). Approval Documents. 2025.
- Endocrine Society. Pharmacological Management of Obesity Clinical Practice Guideline. 2024 update.
Footer disclaimers
Platform Disclaimer. FormBlends is a U.S. telehealth platform. We connect patients with independent licensed clinicians. We do not provide care or prescriptions for medications that are not FDA-approved or legally available in our service areas.
Investigational/Foreign-Approved Drug Notice. Retatrutide is investigational and not approved by the FDA or any regulatory body as of May 2026. Mazdutide is approved in China but is not FDA-approved in the U.S. FormBlends does not sell or supply either drug.
Results Disclaimer. Trial percentages are population means from controlled studies with structured lifestyle interventions. Phase 2 results are preliminary and may not replicate in phase 3 or in real-world populations. Cross-trial comparisons in this article are descriptive and not a substitute for head-to-head clinical evidence.
Trademark Notice. Retatrutide and mazdutide are generic names. Sineipasy is the Innovent brand for mazdutide in China. Mounjaro and Zepbound are registered trademarks of Eli Lilly and Company. Wegovy and Ozempic are registered trademarks of Novo Nordisk A/S. FormBlends is not affiliated with these companies.
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