What is Semaglutide?
Semaglutide is a long-acting glucagon-like peptide-1 (GLP-1) analogue consisting of 31 amino acids with a molecular weight of 4113.64 g/mol and CAS registry number 910463-68-2. It was developed through strategic modifications to the native human GLP-1(7-37) peptide sequence to dramatically extend its pharmacokinetic half-life from approximately 2 minutes (native GLP-1) to approximately 165 hours.
The key structural modifications include: substitution of alanine with aminoisobutyric acid (Aib) at position 8, which confers resistance to enzymatic degradation by dipeptidyl peptidase-4 (DPP-4); substitution of lysine with arginine at position 34; and conjugation of a C-18 fatty diacid chain to lysine at position 26 via a mini-PEG linker, enabling non-covalent binding to serum albumin. These modifications collectively allow for once-weekly subcutaneous administration while maintaining potent GLP-1 receptor activation.
Semaglutide has been the subject of one of the most extensive clinical development programs in metabolic medicine, including the SUSTAIN trials (type 2 diabetes), PIONEER trials (oral formulation), STEP trials (weight management), and the landmark SELECT cardiovascular outcomes trial. It is classified as a research peptide at AminoCore Research and is available exclusively for laboratory and scientific investigation.
Mechanism of Action
Semaglutide exerts its biological effects through selective activation of the GLP-1 receptor, a G protein-coupled receptor expressed in pancreatic beta cells, the central nervous system, the gastrointestinal tract, the cardiovascular system, and other tissues.
Pancreatic Effects
GLP-1 receptor activation on pancreatic beta cells stimulates glucose-dependent insulin secretion through increased intracellular cAMP levels and calcium influx. Critically, this insulinotropic effect is glucose-dependent, meaning insulin release is enhanced primarily when blood glucose is elevated, which minimizes the risk of hypoglycemia. Simultaneously, semaglutide suppresses glucagon secretion from alpha cells in a glucose-dependent manner, reducing hepatic glucose output.
Central Nervous System — Appetite Regulation
Semaglutide crosses the blood-brain barrier and acts on GLP-1 receptors in hypothalamic and hindbrain regions involved in appetite regulation, including the arcuate nucleus, paraventricular nucleus, and the nucleus tractus solitarius. These actions promote satiety, reduce hunger, and decrease food intake. Neuroimaging studies suggest that semaglutide may modulate food reward pathways and reduce cravings for high-fat and energy-dense foods.
Gastrointestinal Effects
Semaglutide delays gastric emptying, which contributes to reduced postprandial glucose excursions and enhanced satiety. This effect is most pronounced during early treatment and may attenuate partially with continued use, a phenomenon known as tachyphylaxis.
Cardiovascular Mechanisms
GLP-1 receptors are expressed in cardiomyocytes and vascular endothelium. Research suggests semaglutide may exert cardioprotective effects through anti-inflammatory pathways, reduction of oxidative stress, improved endothelial function, and favorable effects on lipid metabolism. The SELECT trial demonstrated a 20% reduction in major adverse cardiovascular events.
Research & Clinical Studies
STEP 1 Trial: Body Weight Regulation Research
The Semaglutide Treatment Effect in People with Obesity (STEP 1) trial was a landmark randomized, double-blind, placebo-controlled study published in the New England Journal of Medicine in 2021. The trial enrolled 1,961 adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related comorbidity, without diabetes.
Participants were randomized 2:1 to receive once-weekly subcutaneous semaglutide 2.4 mg or placebo for 68 weeks, alongside lifestyle intervention (reduced-calorie diet and increased physical activity). The co-primary endpoints were percentage change in body weight and achievement of at least 5% weight reduction.
Results demonstrated that the semaglutide group achieved a mean body weight reduction of 14.9% from baseline compared to 2.4% in the placebo group — an estimated treatment difference of 12.4 percentage points (95% CI, −13.4 to −11.5; P<0.001). Among semaglutide-treated participants, 86.4% achieved ≥5% weight loss (vs. 31.5% placebo), 69.1% achieved ≥10% weight loss (vs. 12.0% placebo), and 50.5% achieved ≥15% weight loss (vs. 4.9% placebo).
Clinically significant improvements in cardiometabolic risk factors were observed, including reductions in waist circumference, blood pressure, C-reactive protein, and lipid parameters. The safety profile was consistent with the GLP-1 receptor agonist class, with gastrointestinal events (nausea, diarrhea, vomiting) being the most common adverse effects.
[1] Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989-1002. PubMed ↗
[2] Rubino D, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021;325(14):1414-1425. PubMed ↗
SUSTAIN Program: Glycemic Control Research
The Semaglutide Unabated Sustainability in Treatment of Type 2 Diabetes (SUSTAIN) clinical trial program comprised 10 multinational studies evaluating once-weekly subcutaneous semaglutide (0.5 mg and 1.0 mg) in patients with type 2 diabetes.
SUSTAIN 1 through 6 formed the phase 3a core program, enrolling 7,215 participants. Across these trials, semaglutide was compared to placebo and active comparators including sitagliptin, exenatide extended-release, and insulin glargine. The primary endpoint in each trial was change in glycated hemoglobin (HbA1c) from baseline.
Consistent findings across the program demonstrated HbA1c reductions of 1.0% to 1.8% with semaglutide, with a significant proportion of participants achieving HbA1c targets of <7.0%. In head-to-head comparisons, semaglutide showed superior glycemic control compared to exenatide ER (SUSTAIN 3), insulin glargine (SUSTAIN 4), and sitagliptin (SUSTAIN 2). Notably, semaglutide also produced significant weight loss across all SUSTAIN trials, with reductions of 3.5 to 6.5 kg versus comparators.
The SUSTAIN 6 cardiovascular outcomes trial (n=3,297) was particularly significant, demonstrating a 26% reduction in the composite outcome of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke (HR 0.74; 95% CI, 0.58–0.95; P=0.02) over 104 weeks.
[3] Marso SP, et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2016;375(19):1834-1844. PubMed ↗
[4] Ahmann AJ, et al. Efficacy and Safety of Once-Weekly Semaglutide Versus Exenatide ER in Subjects With Type 2 Diabetes (SUSTAIN 3). Diabetes Care. 2018;41(2):258-266. PubMed ↗
SELECT Trial: Cardiovascular Outcomes Research
The Semaglutide Effects on Cardiovascular Outcomes in People with Overweight or Obesity (SELECT) trial was a landmark randomized, double-blind, placebo-controlled cardiovascular outcomes study that enrolled 17,604 adults aged 45 years or older with established cardiovascular disease and BMI ≥27, without diabetes.
Participants were randomized to once-weekly subcutaneous semaglutide 2.4 mg or placebo and followed for a mean of approximately 40 months. The primary endpoint was the first occurrence of a major adverse cardiovascular event (MACE): cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke.
Semaglutide demonstrated a 20% reduction in the primary MACE endpoint compared to placebo (HR 0.80; 95% CI, 0.72–0.90; P<0.001). This was the first trial to demonstrate cardiovascular benefit with a weight-management medication in a population without diabetes. The cardiovascular benefit appeared early and was sustained throughout the follow-up period.
In a prespecified analysis of weight outcomes, semaglutide produced sustained weight loss over 4 years, with a mean reduction of 10.2% from baseline at week 208, compared to 1.5% with placebo (P<0.0001). Corresponding reductions were observed in waist circumference (−7.7 cm vs. −1.3 cm) and waist-to-height ratio. The safety profile was consistent with the established GLP-1 receptor agonist class.
[5] Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. N Engl J Med. 2023;389(24):2221-2232. PubMed ↗
[6] Ryan DH, et al. Long-term weight loss effects of semaglutide in obesity without diabetes in the SELECT trial. Nat Med. 2024;30:2049-2057. PubMed ↗
STEP 5 Trial: Long-Term Sustained Effects Research
The STEP 5 trial was specifically designed to evaluate the long-term efficacy and safety of once-weekly subcutaneous semaglutide 2.4 mg over 104 weeks (2 years) — the longest treatment duration in the STEP program. Published in Nature Medicine in 2022, the trial enrolled 304 adults with obesity or overweight with at least one weight-related comorbidity, without diabetes.
Participants were randomized 1:1 to semaglutide 2.4 mg or placebo, both combined with behavioral intervention. The co-primary endpoints were percentage change in body weight and achievement of ≥5% weight loss at week 104.
At 2 years, the semaglutide group achieved a mean body weight reduction of 15.2% from baseline, compared to 2.6% with placebo. Improvements in cardiometabolic parameters were sustained throughout the 104-week treatment period, including reductions in waist circumference, systolic blood pressure, HbA1c, fasting glucose, and C-reactive protein.
Notably, 80% of participants with prediabetes at baseline who received semaglutide reverted to normoglycemia by the end of the trial, compared to 37% with placebo. Among participants with normoglycemia at baseline, 99% maintained normoglycemic status with semaglutide versus 86% with placebo. These findings suggest a potential role for semaglutide in diabetes prevention research.
[7] Garvey WT, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med. 2022;28(10):2083-2091. PubMed ↗
PIONEER Program: Oral Formulation Research
The Peptide Innovation for Early Diabetes Treatment (PIONEER) program evaluated the world's first oral GLP-1 receptor agonist formulation of semaglutide. The oral formulation utilizes co-formulation with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC), an absorption enhancer that facilitates transcellular absorption across the gastric epithelium.
The PIONEER program comprised 10 global clinical trials enrolling over 9,500 patients with type 2 diabetes. Oral semaglutide was evaluated at doses of 3 mg, 7 mg, and 14 mg daily and compared against placebo, sitagliptin, empagliflozin, liraglutide, and dulaglutide.
At the 14 mg dose, oral semaglutide demonstrated HbA1c reductions of 1.0% to 1.3% across trials, with a significant proportion of patients achieving HbA1c targets below 7.0%. Weight reductions ranged from 2.3 to 4.7 kg depending on the trial population and comparator. In PIONEER 7, oral semaglutide 14 mg showed comparable efficacy to injectable liraglutide 1.8 mg at 52 weeks.
The clinical significance of this oral peptide delivery system extends beyond convenience — it represents a technological breakthrough in peptide pharmacology, demonstrating that large peptide molecules can achieve clinically meaningful systemic bioavailability through oral administration.
[8] Husain M, et al. Oral Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2019;381(9):841-851. PubMed ↗
[9] Aroda VR, et al. PIONEER 1: Randomized Clinical Trial of the Efficacy and Safety of Oral Semaglutide Monotherapy. Diabetes Care. 2019;42(9):1724-1732. PubMed ↗
Handling & Reconstitution Guidelines
Reconstitution Protocol
Semaglutide lyophilized powder should be reconstituted using sterile bacteriostatic water (BAC water) or sterile phosphate-buffered saline (PBS). Allow the vial to equilibrate to room temperature (15-25°C) for approximately 10 minutes before reconstitution. Using a sterile syringe, inject the diluent slowly along the inner wall of the vial. Do not direct the stream onto the lyophilized cake. Gently swirl the vial until the peptide is completely dissolved. Do not vortex or shake vigorously, as this may cause aggregation or denaturation of the peptide.
Recommended Diluent Volumes
For a 3 mg vial: 0.6 mL BAC water yields a 5 mg/mL concentration. For a 5 mg vial: 1.0 mL BAC water yields a 5 mg/mL concentration. For a 10 mg vial: 2.0 mL BAC water yields a 5 mg/mL concentration. Exact volumes should be adjusted based on experimental protocols and desired final concentrations.
Post-Reconstitution Storage
Store reconstituted semaglutide solution at 2-8°C (refrigerated) and use within 28 days. For extended storage, aliquot into single-use volumes using sterile low-bind microcentrifuge tubes and store at -20°C. Avoid repeated freeze-thaw cycles as these may compromise peptide integrity and biological activity.
Handling Precautions
Use appropriate personal protective equipment (PPE) including nitrile gloves and safety glasses. Work under aseptic conditions to minimize contamination. Semaglutide contains a lipid moiety (C-18 fatty diacid) which may increase adsorption to certain plastic surfaces — use low-bind tubes and tips for precise quantitative work. Use only sterile, single-use needles and syringes for reconstitution.
Storage & Stability Information
Lyophilized Form (Unreconstituted)
Store semaglutide lyophilized powder at -20°C in its original sealed container, protected from light and moisture. Under optimal conditions, the lyophilized peptide maintains stability and purity for up to 24 months. Short-term storage at 2-8°C is acceptable for up to 60 days without significant degradation. Avoid exposure to temperatures above 25°C or to direct sunlight.
Reconstituted Solution
Store reconstituted semaglutide at 2-8°C (standard laboratory refrigeration). Use within 28 days of reconstitution. For longer preservation, prepare aliquots in sterile low-bind microcentrifuge tubes and store at -20°C for up to 3 months. Each freeze-thaw cycle may reduce peptide integrity by 2-5%, so single-use aliquots are strongly recommended.
Stability Considerations
The C-18 fatty diacid modification significantly enhances the pharmacokinetic stability of semaglutide compared to native GLP-1. The Aib substitution at position 8 provides resistance to DPP-4 cleavage, while albumin binding shields the peptide from renal clearance and proteolytic degradation in circulation. However, in the reconstituted form, standard peptide handling best practices should be observed to maintain experimental consistency. Monitor for precipitation or discoloration, which may indicate degradation.
Shipping
Semaglutide is shipped as a lyophilized powder with cold packs. Upon receipt, transfer immediately to -20°C storage.
