Body journey · 7 steps

Inside the body with Survodutide

Survodutide is an experimental weekly injection that copies two natural hormones: GLP-1, made in the gut, and glucagon, made in the pancreas. It is being tested for obesity and for fatty liver disease. Large trials show weight loss and less liver fat, but it is not approved by any regulator we checked, and stomach side effects were common.

Scroll to follow it through the body

01Skin
A weekly injection under the skin
In the trials, survodutide is given as a small injection under the skin once a week. From there it slowly moves into the blood.
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Survodutide has been studied as a subcutaneous injection. In a phase 1 study in Japanese men with overweight or obesity, drug exposure rose with dose and with dose escalation. The phase 3 obesity trials used once-weekly subcutaneous administration.[src][src]
02Bloodstream
A fatty tail helps it last in the blood
Natural hormones like glucagon vanish from the blood within minutes. Survodutide has a fat-like tail added to it, a design trick that helps a drug last much longer, so one injection can work for a week.
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The molecule is a lipidated peptide: a C18 fatty diacid is attached to the lysine at position 24 through a gamma-glutamate and glycine/serine linker, and a non-natural amino acid sits at position 2. Lipidation of this kind is used to promote binding to serum albumin and slow clearance, which is why weekly dosing is possible. The exact terminal half-life was not verified from a primary source, In a dedicated phase 1 study, single-dose exposure (AUC and Cmax) was similar in people with cirrhosis and in healthy individuals.[src][src]
03Brain
The brain receives a fullness signal
Survodutide switches on the GLP-1 receptor, one of the body's fullness signals. People in the trials felt less hungry, and the most common side effect early on was reduced appetite. This is thought to be how it helps people eat less.
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GLP-1R agonism is the proposed driver of reduced appetite and increased satiety; the sponsor describes it in these terms. In a phase 1 study in Japanese men with overweight or obesity, decreased appetite was the most frequent drug-related adverse event (24 of 36 participants, 66.7%). Direct central GLP-1R engagement by survodutide has been inferred from GLP-1 biology and clinical effects rather than imaged in humans in the sources reviewed.[src][src]
04Stomach
The stomach empties more slowly
GLP-1 also slows how fast food leaves the stomach, which helps people feel full for longer. A small human study saw this effect in the first week of treatment, and it faded afterwards.
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In the Japanese phase 1 study, paracetamol absorption, a standard proxy for gastric emptying, decreased in week 1 in two of the three dose groups, which the authors interpret as transient delayed gastric emptying. The same study found plasma glucagon and alanine reduced, consistent with engagement of both receptors. Gastrointestinal events (nausea, vomiting, diarrhoea, constipation) were the most common adverse events in SYNCHRONIZE-1, typically during dose escalation.[src][src][src]
05Liver
The liver gets a glucagon-type signal
Glucagon works mainly on the liver. Survodutide is designed to use that link. In human trials, people with fatty liver disease had much less fat in the liver. Part of that comes from weight loss. An early analysis suggests some effects, especially on liver scarring, may not be explained by weight loss alone, but this is not settled.
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The liver is the main site of glucagon receptor expression, and GCGR agonism is thought to act directly on liver fat handling. Reductions in plasma amino acids and glucagon in phase 1 studies indicate GCGR engagement in humans. Clinical liver effects are established: in the phase 2 MASH trial, a 30% or greater fall in liver fat occurred in 57-67% of survodutide groups versus 14% with placebo, and MASH improvement without worsening fibrosis in 43-62% versus 14%; in SYNCHRONIZE-MASLD, 84.2% versus 24.3% reached a 30% or greater fall (efficacy estimand). A post hoc mediation analysis of the phase 2 MASH trial (n=170, F2-F3) estimated that weight loss accounted for 58.2% of the effect on MRI-measured liver fat and 71.8% of the effect on MASH improvement, but only 36.3% of the effect on fibrosis improvement and under 50% for inflammation/fibrosis blood and imaging markers; the authors read this as suggestive of a direct glucagon-receptor effect in the liver. This is an exploratory, sponsor-authored analysis, not a trial designed to separate the two effects.[src][src][src][src]
06Fat tissue
Weight lost is mostly fat, including belly fat
In a sub-study that used body scans, most of the weight people lost was fat, including fat deep inside the belly. Some lean tissue was lost too, as with other weight-loss drugs. A separate small study is checking whether the drug changes how the body burns energy.
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In the SYNCHRONIZE-1 MRI sub-study, visceral fat fell by up to 34% and liver fat by up to 63.1% from baseline at the higher dose, per the sponsors, and lean-tissue loss was reported at no more than 10.8% of the change in total tissue mass in the company's pre-specified analysis. Whether glucagon receptor activation raises energy expenditure in people on survodutide is under study (a phase 1 comparison with semaglutide, NCT06745284) and is not established here.[src][src]
07Heart
A small rise in heart rate
GLP-1 type drugs can raise heart rate a little. In the big trial, the average rise was about three beats per minute. A large study is checking whether survodutide is safe for the heart over a longer time.
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A published summary of SYNCHRONIZE-1 reports mean heart-rate increases of 3.2 to 3.5 beats per minute at week 76 and no deaths. In early rapid-escalation phase 1 cohorts, cardiac or vascular adverse events were the commonest reason for stopping (7.5% in one cohort). The SYNCHRONIZE-CVOT cardiovascular outcomes trial (n=5,531) is listed as completed on ClinicalTrials.gov, and Zealand Pharma said in August 2026 that results are expected later in the year.[src][src][src][src]