What Is Semaglutide?
Semaglutide is a synthetic glucagon-like peptide-1 (GLP-1) receptor agonist originally developed for the study of glucose homeostasis and metabolic regulation. With a molecular weight of 4,113.58 Da and the molecular formula C187H291N45O59, semaglutide is a 31-amino acid peptide analog of human GLP-1(7-36) with key structural modifications that confer a dramatically extended half-life of approximately 168 hours (7 days), compared to the native peptide's half-life of just 2-3 minutes.
The CAS registry number for semaglutide is 910463-68-2. It was first described in the scientific literature by Lau et al. in 2015 (PMID: 25524397) as part of Novo Nordisk's GLP-1 analog development program. Since then, it has become one of the most extensively studied peptide compounds in metabolic research, with data from the SUSTAIN, STEP, PIONEER, and SELECT trial programs encompassing over 30,000 research subjects.
BeaCapra provides research-grade semaglutide at 99%+ HPLC-verified purity with batch-specific Certificates of Analysis. It is the only supplier offering subscribe & save for automated research compound delivery.
Molecular Structure and Modifications
Semaglutide's extended duration of action stems from three critical structural modifications to the native GLP-1(7-36) sequence:
- Aib substitution at position 8: The native alanine is replaced with α-aminoisobutyric acid (Aib), conferring resistance to dipeptidyl peptidase-4 (DPP-4) enzymatic degradation — the primary clearance pathway for endogenous GLP-1 (PMID: 25524397).
- Arg34Lys substitution: Arginine at position 34 is replaced with lysine, providing an attachment point for the fatty acid moiety.
- C18 fatty diacid side chain: A C18 fatty diacid is conjugated to Lys26 via a mini-PEG linker. This modification enables non-covalent binding to serum albumin, dramatically reducing renal clearance and extending the circulating half-life to approximately 168 hours (PMID: 28479964).
These modifications work in concert: DPP-4 resistance prevents rapid enzymatic inactivation, while albumin binding reduces both renal filtration and receptor-mediated clearance. The result is a compound suitable for once-weekly research dosing protocols — a practical advantage for sustained experimental designs.
Mechanism of Action
Semaglutide exerts its effects through selective agonism of the GLP-1 receptor (GLP-1R), a class B G-protein-coupled receptor (GPCR). The GLP-1R is expressed across multiple tissue types, including pancreatic islets, the central nervous system, gastrointestinal tract, cardiovascular system, and kidney (PMID: 24934313).
Pancreatic Effects
GLP-1R activation on pancreatic β-cells stimulates glucose-dependent insulin secretion through a cAMP/PKA-mediated signaling cascade (PMID: 25348717). Critically, this insulinotropic effect is glucose-dependent — it occurs only when blood glucose exceeds fasting levels, providing an inherent safeguard against hypoglycemia. Simultaneously, GLP-1R agonism suppresses glucagon secretion from pancreatic α-cells, reducing hepatic glucose output (PMID: 21190504).
Central Nervous System Effects
Semaglutide crosses the blood-brain barrier and activates GLP-1R in the hypothalamus, particularly in the arcuate nucleus (PMID: 32773571). Activation of pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) neurons reduces orexigenic signaling, while direct effects on the nucleus tractus solitarius modulate satiety responses. Research by Gabery et al. (PMID: 32773571) confirmed direct neuronal activation in appetite-regulating brain regions using c-Fos immunohistochemistry.
Gastrointestinal Effects
GLP-1R agonism delays gastric emptying through vagal afferent signaling (PMID: 27383054). This slowed transit contributes to post-prandial satiety and altered nutrient absorption kinetics. The magnitude of gastric slowing with semaglutide has been characterized using acetaminophen absorption testing and scintigraphy in multiple clinical research protocols.
Cardiovascular Effects
The SELECT trial (PMID: 37952131) — a 17,604-subject cardiovascular outcomes study — demonstrated a 20% reduction in major adverse cardiovascular events (MACE) with semaglutide versus placebo in subjects with established atherosclerotic cardiovascular disease but without diabetes. This represented the first demonstration of cardiovascular risk reduction with a GLP-1R agonist in a non-diabetic population.
Key Published Research
SUSTAIN Program (Type 2 Diabetes)
The SUSTAIN trials (SUSTAIN 1-10) evaluated semaglutide in over 10,000 subjects with type 2 diabetes. SUSTAIN-6 (PMID: 27633186), a cardiovascular outcomes trial, demonstrated a 26% reduction in MACE. Mean HbA1c reductions ranged from 1.4-1.8% across studies, with dose-dependent effects observed at 0.5 mg and 1.0 mg weekly dosing.
STEP Program (Obesity/Overweight)
The STEP trials evaluated semaglutide 2.4 mg weekly in subjects with obesity or overweight. STEP 1 (PMID: 33567185) demonstrated a mean weight reduction of 14.9% from baseline at 68 weeks versus 2.4% with placebo (n=1,961). STEP 2-5 replicated these findings across various populations including those with type 2 diabetes.
PIONEER Program (Oral Formulation)
The PIONEER trials evaluated an oral formulation of semaglutide co-formulated with the absorption enhancer SNAC (sodium N-[8-(2-hydroxybenzoyl)amino]caprylate). PIONEER 6 (PMID: 31185157) demonstrated cardiovascular safety in 3,183 subjects, while PIONEER 1-10 established efficacy across glycemic and weight endpoints.
SELECT Trial (Cardiovascular Outcomes)
SELECT (PMID: 37952131) enrolled 17,604 subjects with established cardiovascular disease but without diabetes. Semaglutide 2.4 mg weekly reduced the primary MACE endpoint by 20% (HR 0.80, 95% CI 0.72-0.90, p<0.001) over a median follow-up of 39.8 months. This was the first cardiovascular outcomes trial for any GLP-1R agonist in a non-diabetic population.
Pharmacokinetic Profile
| Parameter | Value |
|---|---|
| Molecular Weight | 4,113.58 Da |
| Half-Life | ~168 hours (7 days) |
| Bioavailability (SC) | ~89% |
| Time to Peak (Tmax) | 1-3 days |
| Steady State | 4-5 weeks |
| Protein Binding | >99% (albumin) |
| Metabolism | Proteolytic cleavage, β-oxidation of fatty acid |
| Primary Elimination | Urine (~3%) and feces (~1%) |
| Volume of Distribution | ~12.5 L |
Reconstitution and Handling
BeaCapra semaglutide is supplied as a lyophilized white powder. For detailed reconstitution instructions, see our step-by-step reconstitution guide or use our Reconstitution Calculator.
Basic Protocol
- Allow the vial to reach room temperature (15-25°C) for 10-15 minutes.
- Using a sterile syringe, add the desired volume of bacteriostatic water (BAC water) to the vial. Direct the stream against the glass wall — do not inject directly onto the lyophilized cake.
- Swirl the vial gently in circular motions until the powder fully dissolves. Do not vortex or shake vigorously, as this may denature the peptide.
- The reconstituted solution should be clear and colorless. Discard if particulates or cloudiness are observed.
- Store reconstituted semaglutide at 2-8°C (standard refrigeration). Use within 30 days.
Storage Guidelines
| Form | Temperature | Stability | Notes |
|---|---|---|---|
| Lyophilized | -20°C | 24+ months | Desiccated, light-protected |
| Lyophilized | 2-8°C | 6-12 months | Acceptable for short-term |
| Reconstituted | 2-8°C | 30 days | BAC water preservative |
| Reconstituted | Room temp | 48 hours max | Not recommended |
Purity Verification
Research outcomes depend on reagent quality. BeaCapra publishes batch-specific Certificates of Analysis for every semaglutide batch, including:
- Reverse-phase HPLC — Quantifies purity as the percentage of the target peak area versus total peak area. BeaCapra maintains a ≥99% purity floor.
- Mass spectrometry (ESI-MS) — Confirms molecular identity by matching observed mass-to-charge ratios with the theoretical molecular weight of 4,113.58 Da.
- Amino acid analysis — Verifies the peptide sequence composition.
- Endotoxin testing — LAL assay confirms <1 EU/mg for research applications requiring low endotoxin material.
For a detailed guide on interpreting these results, see our article: Semaglutide Purity: How to Verify Your Source with COA Analysis.
BeaCapra Semaglutide
BeaCapra offers research-grade semaglutide in a 3 mg lyophilized format at $129.99 per vial, or $110.49 with Subscribe & Save (15% off every order). Every vial ships with a batch-specific Certificate of Analysis. Orders placed before 2PM EST ship the same business day. Free shipping on orders over $149.
Frequently Asked Questions
What is the half-life of semaglutide?
Semaglutide has a half-life of approximately 168 hours (7 days), primarily due to its C18 fatty diacid side chain that enables non-covalent albumin binding. This extended half-life supports once-weekly research dosing protocols.
What is the difference between semaglutide and tirzepatide?
Semaglutide is a selective GLP-1 receptor agonist (MW: 4,113.58 Da), while tirzepatide is a dual GIP/GLP-1 receptor agonist (MW: 4,813.45 Da). Tirzepatide's dual receptor activity represents a distinct pharmacological mechanism. See our detailed comparison.
How should semaglutide be reconstituted?
Reconstitute with bacteriostatic water added slowly to the vial wall. Swirl gently — do not shake. See our complete reconstitution guide for step-by-step instructions with volume calculations.
What purity should I look for in research-grade semaglutide?
Research-grade semaglutide should be ≥98% purity by HPLC, with mass spectrometry confirmation of molecular identity. BeaCapra maintains a ≥99% purity floor and publishes batch-specific COAs. See our purity verification guide.
Can I get semaglutide on subscription?
Yes. BeaCapra is the only research peptide supplier offering subscribe & save on semaglutide. Save 15% on every order with automated delivery every 30, 60, or 90 days. Cancel, skip, or modify anytime.
All BeaCapra products are sold for research use only. Not for human consumption.