Semaglutide
Also known as: Ozempic, Wegovy, Rybelsus, GLP-1 RA
A long-acting GLP-1 receptor agonist with established efficacy in type 2 diabetes and obesity clinical trials.
Molecular Data
- Class
- GLP-1 receptor agonist / Incretin mimetic
- Molecular Weight
- 4,113.58 Da
- Molecular Formula
- C₁₈₇H₂₉₁N₄₅O₅₉
- Half-Life
- ~7 days (enables once-weekly dosing)
- Sequence / Structure
- 34-amino acid GLP-1 analog with C-18 fatty diacid modification at Lys²⁶
Mechanism of Action
Semaglutide is a synthetic analog of human glucagon-like peptide-1 (GLP-1), an incretin hormone secreted by intestinal L-cells in response to food intake. It shares ~94% sequence homology with native GLP-1 but incorporates modifications that dramatically extend its plasma half-life.
Key structural modifications: - Substitution of alanine at position 8 with α-aminoisobutyric acid (Aib) to prevent DPP-4 cleavage - C-18 fatty diacid chain attached at lysine 26 via a mini-PEG linker, enabling albumin binding (which prevents renal clearance and slows enzymatic degradation)
Pharmacological mechanisms: - Glucose-dependent insulin secretion: Activates GLP-1 receptors on pancreatic β-cells, stimulating insulin release only in the presence of elevated glucose — this glucose-dependence reduces hypoglycemia risk relative to sulfonylureas. - Glucagon suppression: Inhibits α-cell glucagon release in a glucose-dependent manner, reducing hepatic glucose output. - Delayed gastric emptying: Slows gastric motility, reducing post-meal glucose spikes and contributing to satiety. - Central appetite regulation: GLP-1 receptors in the hypothalamus and brainstem mediate reduced food intake. Neuroimaging studies show reduced activity in reward circuitry in response to food cues after semaglutide treatment. - Cardiovascular effects: Mechanisms include anti-inflammatory effects on vasculature, reduced lipid accumulation in macrophages, and direct GLP-1 receptor signaling in the heart and vasculature — investigated in the SUSTAIN-6 and LEADER trials.
Research History
Semaglutide was developed by Novo Nordisk as an improvement over liraglutide (once-daily GLP-1 RA) to enable once-weekly subcutaneous dosing. The key innovation was the C-18 fatty diacid albumin-binding modification, which extends the half-life to approximately 7 days.
The SUSTAIN clinical trial program (8 major trials, >7,000 participants) established efficacy and safety in type 2 diabetes. SUSTAIN-6 (2016) demonstrated a 26% reduction in major adverse cardiovascular events (MACE) in high-cardiovascular-risk patients with T2DM — the basis for the cardiovascular indication.
Subcutaneous semaglutide received FDA approval as Ozempic in December 2017 for T2DM and cardiovascular risk reduction. An oral formulation (Rybelsus) followed in 2019, using the absorption enhancer SNAC to enable gastrointestinal uptake.
The STEP clinical program (5 trials) evaluated higher-dose semaglutide (2.4 mg/week) in adults with obesity. STEP-1 (2021, NEJM) demonstrated ~14.9% mean body weight reduction versus ~2.4% placebo over 68 weeks. FDA approved this dose as Wegovy for chronic weight management in June 2021.
The SELECT trial (2023, NEJM) demonstrated a 20% reduction in MACE in overweight/obese adults without diabetes, establishing a cardiovascular benefit independent of glycemic effects and leading to an FDA indication expansion in 2024.
Notable Studies
Marso SP, Bain SC, Consoli A, et al. · New England Journal of Medicine
Landmark cardiovascular outcomes trial (n=3,297) demonstrating 26% relative risk reduction in MACE (CV death, non-fatal MI, non-fatal stroke) in T2DM patients with high CV risk over 2 years.
Wilding JPH, Batterham RL, Calanna S, et al. · New England Journal of Medicine
Phase III trial (n=1,961) showing 2.4 mg semaglutide weekly produced mean 14.9% body weight reduction vs. 2.4% placebo at 68 weeks. The pivotal trial supporting Wegovy approval.
Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. · New England Journal of Medicine
Phase III trial (n=17,604) in overweight/obese adults without T2DM demonstrating 20% reduction in MACE with semaglutide 2.4 mg weekly over ~3.3 years — establishing CV benefit independent of diabetes.
Effect of oral semaglutide on glycemic control and body weight in patients with type 2 diabetes (PIONEER 1)
2019Aroda VR, Rosenstock J, Terauchi Y, et al. · Diabetes Care
Phase III trial establishing efficacy and safety of oral semaglutide (SNAC co-formulation) across doses of 3, 7, and 14 mg, demonstrating dose-dependent HbA1c and weight reductions.
Research Protocols
The following protocols describe doses used in published research studies. They are not prescriptions or recommendations for human use.
Type 2 diabetes (SUSTAIN program dose escalation)
- Dose
- 0.25 mg → 0.5 mg → 1.0 mg (subcutaneous)
- Route
- Subcutaneous injection
- Frequency
- Once weekly
- Duration
- Escalation over 8 weeks, then maintenance
Standard escalation used in clinical trials to reduce GI side effects. Doses used in FDA-approved Ozempic labeling.
Chronic weight management (STEP program)
- Dose
- 0.25 mg → escalate to 2.4 mg over 16 weeks
- Route
- Subcutaneous injection
- Frequency
- Once weekly
- Duration
- 16-week escalation; ongoing maintenance
Dose used in STEP trials; corresponds to FDA-approved Wegovy 2.4 mg dose.