Semaglutide
What is semaglutide?
Semaglutide is a peptide that activates the GLP-1 receptor. GLP-1 is a hormone involved in blood sugar and appetite signals. Clinical findings concern tested medicine formulations, not a laboratory vial.
Last updated: 2026-10-08
At a Glance
IN THIS ARTICLE
Why is Semaglutide studied?
Semaglutide is important because it has been studied in large human trials. STEP, SELECT and FLOW examine different outcomes. They concern body weight, cardiovascular events and kidney disease.
A cardiovascular event includes outcomes such as heart attack or stroke. A kidney endpoint measures a defined change in kidney health. These are distinct from receptor activity in a cell assay.
The clinical evidence applies to the tested formulations and populations. A medicine containing semaglutide is not the same product as a research vial. Brand approval does not approve laboratory inventory for treatment.
How does Semaglutide work in research models?
GLP-1 means glucagon-like peptide-1. Semaglutide is a modified analogue of this hormone. An analogue is a molecule designed to resemble another molecule.
The modifications affect breakdown and binding to albumin, a blood protein. The pathway below outlines receptor and cellular responses. These responses need to be distinguished from clinical results.
MACE means major adverse cardiovascular events. SELECT measured these events in a defined population. That finding does not establish every proposed effect of GLP-1 signaling.
Semaglutide's Mechanism of Action
Structural Modifications
Modifications affect enzymatic breakdown and albumin binding. Albumin is a protein in blood.
GLP-1 Receptor Binding
Semaglutide activates GLP-1 receptors. Receptor activation changes signaling molecules inside cells.
Appetite Suppression (Hypothalamic)
Brain signaling related to appetite is one research focus. Human trial outcomes must be distinguished from a receptor assay.
Gastric Emptying Delay
Gastric emptying means movement of food from the stomach. Researchers examine how this process changes under study conditions.
Insulin & Glucagon Regulation
Studies examine insulin and glucagon responses. These hormones have roles in blood glucose regulation.
Cardiovascular & Systemic Effects
SELECT measured cardiovascular events in a defined population. A clinical outcome does not prove every proposed cellular mechanism.
What does the evidence show?
The trial programs ask different questions in different populations. STEP focuses on body-weight outcomes. SELECT and FLOW examine cardiovascular and kidney outcomes.
The figures below retain the original profile’s reported results. Read each with its endpoint and analysis method. A percentage from one trial is not a universal expected response.
The inherited program table contains time-sensitive descriptions. Its ESSENCE label should not be used as evidence of an Alzheimer’s trial without checking the actual source.
Major Semaglutide Clinical Programs
| Program | Population | Key Finding | Significance |
|---|---|---|---|
| STEP 1-5 | Obesity/overweight ± T2D | 16.9% mean weight loss at 68 weeks (2.4mg) | Led to Wegovy FDA approval |
| SELECT | Obesity + established CVD | 20% MACE reduction vs. placebo | First CV indication for obesity drug |
| SUSTAIN 1-10 | Type 2 diabetes | Superior HbA1c reduction vs. all comparators | Established Ozempic as T2D standard |
| PIONEER 1-10 | Type 2 diabetes (oral) | First oral GLP-1 agonist; non-inferior to injectable | Led to Rybelsus approval |
| FLOW | T2D + chronic kidney disease | 24% reduction in kidney disease progression | First GLP-1 with renal endpoint |
| STEP HFpEF | Obesity + heart failure (preserved EF) | Significant symptom improvement | Expanded CV applications |
| ESSENCE | Alzheimer's disease | Ongoing — results expected 2026-2027 | Tests neuroinflammation hypothesis |
Landmark Results
STEP 1 (NEJM, 2021)
16.9% mean body weight reduction at 68 weeks with semaglutide 2.4mg vs. 2.4% with placebo. 86.4% of patients achieved ≥5% weight loss. First time an anti-obesity medication achieved results comparable to bariatric surgery in a large RCT.
SELECT (NEJM, 2023)
20% reduction in major adverse cardiovascular events (cardiovascular death, non-fatal MI, non-fatal stroke) in 17,604 patients with obesity and established CVD but without diabetes. The trial that changed how the medical field views obesity treatment.
FLOW (NEJM, 2024)
24% reduction in the composite kidney endpoint (kidney failure, sustained GFR decline, renal death) in patients with T2D and CKD. Trial stopped early for efficacy — the first GLP-1 agonist to demonstrate kidney protection.
Semaglutide vs. Tirzepatide vs. Retatrutide
The key structural comparison is receptor activity. Semaglutide targets GLP-1, tirzepatide targets GLP-1 and GIP, and retatrutide targets all three listed receptors. These differences inform research questions.
Cross-trial percentages are not direct comparative evidence. The populations and methods differ. Outcomes from a tested medicine do not validate another formulation.
| Property | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Receptor Targets | GLP-1 only | GLP-1 + GIP | GLP-1 + GIP + Glucagon |
| Generation | 2nd gen single-agonist | 1st gen dual-agonist | 1st gen triple-agonist |
| Max Weight Loss | ~16.9% (STEP 1) | ~22.5% (SURMOUNT-1) | ~28.7% (TRIUMPH-4) |
| Cardiovascular | SELECT: 20% MACE reduction ✓ | SURPASS-CVOT: ongoing | TRIUMPH-3: ongoing |
| Kidney Protection | FLOW: 24% reduction ✓ | Not yet studied | Not yet studied |
| Oral Formulation | Yes (Rybelsus) | In development | Not available |
| FDA Status | Fully approved (multiple indications) | Fully approved (T2D + obesity) | Investigational (~2027) |
| Safety Database | Largest (17,000+ in SELECT alone) | Large | Moderate (Phase 3 ongoing) |
| Annual Revenue | $30B+ (2025) | $15B+ (2025) | N/A (investigational) |
| Key Advantage | Deepest evidence base; CV + renal proven | Superior weight loss to semaglutide | Most weight loss; liver fat clearance |
What are the limits of the safety evidence?
The cited trials report digestive adverse events and other safety observations. These are findings about defined clinical preparations. They do not support self-treatment with a research vial.
Risk depends on population, formulation and exposure conditions. Frequency figures should be read in their original study context. No brief summary can rule out rare or long-term harm.
What questions remain for future research?
GLP-1 research extends beyond glucose and body weight. Cardiovascular, kidney and other proposed outcomes need their own evidence. A plausible mechanism does not establish a new indication.
Formulations and combinations are also being investigated. A combination must be tested as that combination. Results for semaglutide alone cannot prove the effect of a premixed research product.
Frequently Asked Questions
What is semaglutide?
How does semaglutide cause weight loss?
What is the SELECT trial?
How does semaglutide compare to tirzepatide?
What are the main side effects of semaglutide?
Is there an oral form of semaglutide?
Does weight come back after stopping semaglutide?
References
- [1] Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). NEJM. 2021;384:989-1002.
- [2] Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). NEJM. 2023;389:2221-2232.
- [3] Perkovic V, et al. Effects of Semaglutide on Chronic Kidney Disease in Patients with Type 2 Diabetes (FLOW). NEJM. 2024;391:109-121.
- [4] Kosiborod MN, et al. Semaglutide in Patients with Heart Failure with Preserved Ejection Fraction and Obesity (STEP-HFpEF). NEJM. 2023;389:1069-1084.
- [5] Knop FK, et al. Oral Semaglutide 50 mg Taken Once Daily in Adults with Overweight or Obesity (OASIS 1). Lancet. 2023;402:705-719.
- [6] Drucker DJ. The GLP-1 Journey: From Discovery Science to Therapeutic Impact. J Clin Invest. 2024;134(2):e175634.
