Mazdutide vs Retatrutide: Which is better for weight loss?

Mazdutide and retatrutide are two of the most closely watched compounds in the GLP-1 research field. Both are once-weekly injectables under active clinical investigation, and both have now produced multi-year, large-scale trial data — which is more than can be said for most comparisons floating around right now. Here's an up-to-date, data-first breakdown of how they differ.

Quick Comparison

Mazdutide is developed by Innovent Biologics, which holds the rights in China, while Eli Lilly retains development rights for the rest of the world. Retatrutide, by contrast, is developed entirely by Eli Lilly. Mechanistically, mazdutide is a dual agonist, activating the GLP-1 and glucagon receptors, while retatrutide is a triple agonist, adding GIP into the mix alongside GLP-1 and glucagon. Both are administered the same way: a once-weekly subcutaneous injection.

On efficacy, the furthest trial readouts to date favor retatrutide. Mazdutide's GLORY-1 Phase 3 trial, published in NEJM in 2025, showed 14.0% weight loss at 48 weeks on the 6 mg dose. Retatrutide's TRIUMPH-1 Phase 3 trial, with topline results announced in May 2026, showed 28.3% weight loss at 80 weeks on the 12 mg dose.

Regulatory status is where mazdutide currently leads: it was approved in China by the NMPA in June 2025 for weight management, though it remains unapproved by the FDA. Retatrutide isn't approved anywhere yet — it's still moving through Eli Lilly's global TRIUMPH registrational program.

Side effects are broadly similar between the two, as expected given their shared GLP-1 mechanism. Mazdutide's most common adverse events are diarrhea, decreased appetite, nausea, and vomiting. Retatrutide's are nausea, diarrhea, and vomiting — the same GI-driven profile typical of this drug class.

Mechanism: Dual vs. Triple Agonism

Both molecules descend from the same research lineage — oxyntomodulin-inspired multi-receptor agonists designed to outperform single-target GLP-1 drugs like semaglutide.

• Mazdutide (IBI362 / LY3305677) activates two receptors: GLP-1 and glucagon. The glucagon component is theorized to add energy expenditure on top of the appetite suppression and slowed gastric emptying that GLP-1 provides.

• Retatrutide goes a step further, activating GLP-1, GIP, and glucagon simultaneously — the first "triple-G" agonist to reach late-stage trials. The added GIP pathway is associated with additional insulin sensitization and appetite regulation beyond what dual agonists achieve.

More receptor targets isn't automatically "better" — it usually means a different tolerability curve alongside different efficacy, which is exactly what the trial data shows.

Weight Loss Data: The Real Numbers (Updated 2026)

This is where a lot of older comparison content is now out of date. Both programs have published newer, larger readouts since late 2025.

Retatrutide — TRIUMPH-1 (Phase 3, topline results announced May 21, 2026): 2,339 adults with obesity/overweight, no diabetes, randomized to 4 mg, 9 mg, 12 mg, or placebo over 80 weeks:

• 4 mg: 19.0% weight loss

• 9 mg: 25.9% weight loss

• 12 mg: 28.3% weight loss (vs. 2.2% placebo)

• In a blinded extension for participants with baseline BMI ≥35, the 12 mg group reached 30.3% weight loss at 104 weeks, with no plateau observed

Mazdutide — GLORY-1 (Phase 3, published in NEJM, 2025): 610 Chinese adults with obesity or overweight with comorbidities, randomized to 4 mg, 6 mg, or placebo over 48 weeks:

• 4 mg: 11.0% weight loss

• 6 mg: 14.0% weight loss (vs. 0.3% placebo)

• GLORY-2, testing a 9 mg dose, reported up to 20.1% weight loss

Taken together, retatrutide's ceiling is currently higher at every comparable dose tier and duration, though the trials weren't run head-to-head, use different populations (mazdutide's program is Chinese-adult-only so far; retatrutide's TRIUMPH program is international), and cover different follow-up windows — so treat this as directional, not a controlled comparison.

Safety and Tolerability

Adverse event profiles are broadly similar across both compounds, consistent with what's expected from incretin-pathway agonists:

• Mazdutide: most common adverse events across trials were diarrhea (~36%), decreased appetite (~29%), nausea (~23%), and vomiting (~14%). GI effects were mostly mild-to-moderate and concentrated in the dose-escalation phase.

• Retatrutide: discontinuation due to adverse events in TRIUMPH-1 was 4.1% (4 mg), 6.9% (9 mg), and 11.3% (12 mg), versus 4.9% on placebo — meaning higher-dose retatrutide carries a somewhat higher discontinuation rate, though still low in absolute terms.

Both compounds carry the standard incretin-class contraindication flags (personal/family history of medullary thyroid carcinoma, MEN2, pancreatitis history) and require titration to manage GI tolerability.

Regulatory Status: Where Each One Actually Stands

This is the part that's most commonly out of date on other comparison pages, so it's worth being precise:

• Mazdutide was approved by China's NMPA in June 2025 for chronic weight management, sold domestically as Xinermei. It has not been submitted for FDA approval, and no US IND/NDA filing has occurred as of mid-2026 — Lilly's US development (outside Innovent's China rights) is still in earlier-phase trials.

• Retatrutide has no approval anywhere yet. It's in Eli Lilly's global registrational TRIUMPH program (TRIUMPH-1 through TRIUMPH-4), which has enrolled more than 5,800 participants across obesity, diabetes, cardiovascular, and comorbidity-specific trials. TRIUMPH-1 data (the core dataset likely to anchor an eventual FDA submission) was released in May 2026; additional trial arms are expected to read out through the rest of 2026.

Neither compound is legally available for human use in the US or UK outside of clinical trial enrollment. Anything sold outside a licensed trial or approved market is, by definition, unapproved for human use.

Which One Should You Be Watching?

• If your interest is current highest-efficacy data, retatrutide's triple-agonist mechanism is currently producing the larger effect sizes at comparable trial durations.

• If your interest is regulatory maturity, mazdutide is ahead — it already has a live approval and a commercial market (China), while retatrutide is still pre-approval everywhere.

• If your interest is research-grade compound tracking, both are worth following closely through 2026 as TRIUMPH-2/3/4 and mazdutide's broader international trials continue to read out.

Sources

1. Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med, 2023.

2. Eli Lilly. TRIUMPH-1 topline Phase 3 results, announced May 21, 2026.

3. Ji L, et al. GLORY-1: Phase 3 trial of mazdutide in Chinese adults with obesity/overweight. N Engl J Med, 2025. DOI: 10.1056/NEJMoa2411528.

4. Innovent Biologics / Eli Lilly press releases, NMPA approval announcement, June 2025.

5. Giblin et al. TRIUMPH program design. Diabetes, Obesity and Metabolism, 2026.

This content is for research and informational purposes only. Neither mazdutide nor retatrutide is approved for human use in the United States, and this article does not constitute medical advice or a recommendation for use outside of licensed clinical trials.