Inside the body with Semaglutide

The C18 fatty diacid on Lys26 mediates albumin binding (>99% bound), reducing renal clearance and protecting against metabolic degradation; Aib8 confers DPP-4 stability. Volume of distribution is about 12.5 L, clearance about 0.05 L/h, and elimination half-life about 1 week. The design was published in the discovery paper, where the plasma half-life in mini-pigs after intravenous dosing was 46.1 h (animal data).[src][src]

Semaglutide selectively binds and activates the GLP-1 receptor, stimulating insulin secretion and lowering glucagon secretion in a glucose-dependent manner. The cryo-EM structure of the receptor-Gs complex (PDB 7KI0) shows the receptor in its active, G-protein-coupled state.[src][src]

The label describes a minor delay in gastric emptying in the early postprandial phase. In a 20-week placebo-controlled study of semaglutide in 72 adults with obesity, paracetamol absorption over 5 hours after a meal (an indirect gastric-emptying measure) rose 8% (P=0.005), not significant after adjusting for body weight (P=0.12), with no effect over the first hour. The authors concluded there was no evidence of delayed gastric emptying at week 20 by this indirect measure, so the effect appears small with continued use.[src][src]

Human data: in a placebo-controlled study, semaglutide reduced ad libitum energy intake by 35% at week 20, reduced hunger and prospective food consumption, and increased fullness and satiety. Animal-only data: in rodents, semaglutide did not cross the blood-brain barrier but reached the brainstem, septal nucleus and hypothalamus through circumventricular organs and sites next to the ventricles, activated c-Fos in 10 brain areas, and lowered body weight without lowering energy expenditure. The label states the GLP-1 receptor is present in brain areas involved in appetite regulation, and that animal studies show semaglutide activates neurons there.[src][src][src]

In STEP 1 (1,961 adults with overweight or obesity, 68 weeks, plus lifestyle intervention), mean body-weight change was -14.9% with semaglutide versus -2.4% with placebo (difference -12.4 percentage points). 86.4% versus 31.5% lost at least 5%, 69.1% versus 12.0% at least 10%, and 50.5% versus 4.9% at least 15%. Weight loss is understood to follow reduced energy intake; STEP 1 is a human trial and is not a fat-tissue mechanism study.[src]

SUSTAIN-6 (type 2 diabetes, 104 weeks): primary composite outcome in 6.6% versus 8.9%, hazard ratio 0.74 (95% CI 0.58 to 0.95). SELECT (heart disease and overweight or obesity without diabetes, mean follow-up 39.8 months): 6.5% versus 8.0%, hazard ratio 0.80 (95% CI 0.72 to 0.90). The label states the exact mechanism of cardiovascular risk reduction has not been established.[src][src][src]

FLOW (3,533 participants with type 2 diabetes and CKD; median follow-up 3.4 years; stopped early at a prespecified interim analysis): major kidney disease events in 331 versus 410 first events, hazard ratio 0.76 (95% CI 0.66 to 0.88; P=0.0003); annual eGFR decline slower by 1.16 mL/min/1.73 m2. The label states the mechanism of kidney-related risk reduction has not been established.[src][src]

ESSENCE part 1 (800 patients, week 72 interim analysis, biopsy-defined MASH with fibrosis stage 2 or 3): steatohepatitis resolution without worsening fibrosis in 62.9% versus 34.3%; fibrosis reduction without worsening steatohepatitis in 36.8% versus 22.4%. The FDA approved this indication in August 2025 under accelerated approval; continued approval may depend on a confirmatory trial showing clinical benefit. The label says the precise mechanism in humans is not fully understood and may involve weight loss and other pathways; mouse-model liver improvements are animal-only evidence.[src][src]