Survodutide SYNCHRONIZE-1: what the phase 3 data actually shows
The once-weekly glucagon/GLP-1 dual agonist reduced body weight by up to 13.0% at 76 weeks — real and clinically meaningful, but below the phase 2 headline and below tirzepatide. Here's the honest read of the numbers.
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How It Works
Survodutide activates BOTH the GLP-1 receptor (appetite, satiety, glucose control) and the glucagon receptor. Layering glucagon agonism on top of GLP-1 is the design bet behind its weight-loss and liver-fat effects.
Unlike pure GLP-1 drugs, survodutide also activates the glucagon receptor, which is proposed to raise energy expenditure and act directly on the liver — a hypothesized basis for its MASH / liver-fat signal.
Subcutaneous once-weekly, escalated up to 3.6 mg or 6.0 mg. Slow titration is required because gastrointestinal side effects are the main tolerability limit.
SYNCHRONIZE-1’s primary number uses the conservative treatment-regimen estimand, which counts early discontinuations and rescue-medication use. Phase 2’s -14.9% came from a different (planned-treatment) analysis, so the two figures are not directly comparable.
What the Data Shows
Key Takeaways
- SYNCHRONIZE-1 (n=725) met both primary endpoints: mean weight change at week 76 was -12.2% (3.6 mg) and -13.0% (6.0 mg) vs -5.4% for placebo (treatment-regimen estimand).
- 72.6% (3.6 mg) and 71.9% (6.0 mg) of participants lost at least 5% of body weight vs 46.3% on placebo (P<0.001 for all comparisons).
- In SYNCHRONIZE-1, the 3.6 mg and 6.0 mg doses produced similar weight loss (-12.2% vs -13.0%).
- In people with type 2 diabetes, the separate SYNCHRONIZE-2 phase 3 trial (n=752; PMID: 42820639) found smaller weight loss: -8.2% (3.6 mg) and -9.8% (6.0 mg) vs -3.9% for placebo at week 76 (treatment-regimen estimand), with HbA1c falling 0.9 and 0.8 percentage points vs 0.2 on placebo from a 7.4% baseline.
- In the separate SYNCHRONIZE-MASLD phase 3 trial, 68.5% of survodutide-treated patients had a ≥30% reduction in liver fat vs 28.6% on placebo at week 48 (treatment-regimen estimand; 84.2% vs 24.3% under the efficacy estimand). The trial was placebo-controlled, with no GLP-1 comparator.
- Phase 2 MASH data showed histologic MASH improvement without worsening fibrosis in up to 62% of patients (4.8 mg) vs 14% on placebo.
- Gastrointestinal side effects dominate the safety profile: reported by 80.9% (3.6 mg) and 89.7% (6.0 mg) of participants in SYNCHRONIZE-1, typically mild-to-moderate; no deaths were reported. In SYNCHRONIZE-2, GI adverse events occurred in 72.8% (3.6 mg) and 77.7% (6.0 mg) vs 38.6% on placebo.
- Whether survodutide is more or less effective than tirzepatide — cross-trial numbers (~13% vs ~21%) are indirect and no head-to-head trial has been run.
- How it compares with tirzepatide or semaglutide in type 2 diabetes — SYNCHRONIZE-2 was placebo-controlled, with no active comparator.
- Long-term (multi-year) weight maintenance and hard cardiovascular outcomes — the phase 3 cardiovascular safety trial, SYNCHRONIZE-CVOT (design paper: PMID: 39453356; registry: NCT06077864), is listed as completed in June 2026 on ClinicalTrials.gov, but its results have not yet been published.
- Which estimand best predicts real-world results — the ~13% headline uses the conservative treatment-regimen estimand, which counts early discontinuations and rescue-medication use.
- When or whether it will be approved or available — survodutide is investigational and not FDA/EMA-approved.
Frequently Asked Questions
What is survodutide and how does it work?
Survodutide (BI 456906) is an investigational once-weekly injectable that activates both the GLP-1 receptor and the glucagon receptor. GLP-1 activity suppresses appetite and improves glucose handling, while glucagon activity is intended to raise energy expenditure and reduce liver fat — a dual mechanism that pure GLP-1 drugs like semaglutide do not have.
What did the SYNCHRONIZE-1 phase 3 trial show?
In 725 adults with obesity and without diabetes, once-weekly survodutide reduced body weight by a mean of 12.2% (3.6 mg) to 13.0% (6.0 mg) at week 76 versus 5.4% on placebo (treatment-regimen estimand). About 72% of participants on each dose lost at least 5% of body weight versus 46% on placebo.
Does survodutide work in people with type 2 diabetes (SYNCHRONIZE-2)?
Yes, but the weight loss was smaller. In the separate SYNCHRONIZE-2 phase 3 trial (752 adults with obesity and type 2 diabetes, N Engl J Med 2026), mean weight change at week 76 was -8.2% (3.6 mg) and -9.8% (6.0 mg) versus -3.9% on placebo (treatment-regimen estimand), and 57.6% and 64.5% lost at least 5% of body weight versus 35.1% on placebo. HbA1c fell by 0.9 and 0.8 percentage points versus 0.2 on placebo, from a baseline of 7.4%.
How does survodutide compare to tirzepatide (Mounjaro/Zepbound)?
No head-to-head trial exists. Indirectly, survodutide’s ~13% treatment-regimen weight loss at 76 weeks reads below tirzepatide’s ~20.9% at 15 mg in SURMOUNT-1, but the trials used different designs, doses and estimands, so the comparison is approximate. Survodutide also has liver-fat data (SYNCHRONIZE-MASLD), but that trial was placebo-controlled, so it does not show how survodutide compares with tirzepatide on liver fat.
Why is survodutide considered promising for fatty liver (MASH/MASLD)?
Its glucagon-receptor activity is proposed to act directly on the liver. In the SYNCHRONIZE-MASLD phase 3 trial, 84.2% of treated patients had a ≥30% reduction in liver fat versus 24.3% on placebo (efficacy estimand; 68.5% vs 28.6% under the treatment-regimen estimand), and phase 2 data showed histologic MASH improvement in up to 62% of patients. Both trials were placebo-controlled, with no GLP-1 comparator.
Is survodutide FDA-approved or available to buy?
No. Survodutide is investigational, is being developed by Boehringer Ingelheim (which funded its trials), and is in phase 3 trials. It is not approved by the FDA or EMA and is not legitimately available as a research chemical or from consumer vendors.
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Educational purposes only. Not medical advice.
Survodutide is investigational and not approved by the FDA or EMA. Cross-trial comparisons are indirect. Consult a licensed clinician before making any treatment decisions.