Semaglutide Research Review: Structure, GLP-1R and Trials

Semaglutide is the reference compound against which most newer incretin peptides are measured. A long-acting analogue of human glucagon-like peptide-1 (GLP-1), it was designed by Novo Nordisk as a successor to liraglutide and has since been studied in some of the largest randomised trials ever run for a peptide. This review covers its discovery, chemistry, receptor pharmacology, the clinical programmes that define it, and the questions still open for researchers.

Origin and discovery

Native GLP-1 is a product of the proglucagon gene released by intestinal L-cells after nutrient intake. Its biologically active forms, GLP-1(7–36) amide and GLP-1(7–37), are cleaved by dipeptidyl peptidase-4 (DPP-4) and cleared by the kidney within minutes, which makes the native hormone unsuitable as a research tool for sustained receptor activation.

Novo Nordisk's first answer was liraglutide, which attached a C16 fatty acid to the GLP-1 backbone so that the peptide bound albumin. Semaglutide extended this approach. Its discovery was described by Lau and colleagues in the Journal of Medicinal Chemistry in 2015, which documented a systematic search over fatty-acid length, linker chemistry and position-8 substitutions to maximise albumin affinity while retaining GLP-1 receptor potency. Knudsen and Lau (2019) later reviewed the full development path from liraglutide to semaglutide. The programme illustrates a general principle of peptide half-life engineering: reversible binding to a long-lived plasma protein, rather than covalent conjugation or PEGylation, can extend exposure while leaving the peptide free to dissociate and engage its receptor.

Structure and chemistry

Semaglutide is a 31-residue analogue of GLP-1(7–37) with three defining changes:

• Position 8: alanine is replaced by α-aminoisobutyric acid (Aib), which blocks DPP-4 cleavage.
• Position 34: lysine is replaced by arginine, leaving a single lysine for selective acylation.
• Position 26: the lysine side chain carries a C18 fatty diacid attached through a γ-glutamic acid and two OEG (8-amino-3,6-dioxaoctanoic acid) spacer groups.

The C18 diacid binds serum albumin strongly, and the hydrophilic spacer was optimised to preserve receptor binding. The combination of DPP-4 resistance, albumin binding and reduced renal clearance gives a reported half-life of about seven days. The theoretical molecular weight is about 4,113.6 Da.

From an analytical standpoint, semaglutide is often used as a model lipidated peptide. Its identity is confirmed by mass spectrometry, and impurity profiles typically include deletion sequences and isomers arising during solid-phase synthesis and acylation.

Receptor pharmacology and mechanism studied

The GLP-1 receptor is a class B G protein-coupled receptor that signals mainly through Gαs and cAMP. Semaglutide is a full agonist with a receptor affinity lower than native GLP-1, a deliberate trade-off for albumin binding.

Mechanisms studied include:

• Pancreas. Glucose-dependent stimulation of insulin secretion and suppression of glucagon secretion, which together lower glucose without the hypoglycaemia associated with glucose-independent secretagogues.
• Gastrointestinal tract. Slowing of gastric emptying, most pronounced early in exposure.
• Central nervous system. In mouse studies, fluorescently labelled semaglutide reached circumventricular organs and the arcuate nucleus and engaged hypothalamic and hindbrain networks involved in food intake (Gabery et al., 2020). How a large, albumin-bound peptide accesses these regions remains a research topic in its own right.
• Cardiovascular and renal tissues. GLP-1 receptors are expressed in parts of the heart, vasculature and kidney, and anti-inflammatory and atherosclerosis-related effects have been described in animal models. The relative contribution of direct and indirect effects is unresolved (Drucker, 2018).
• Receptor regulation. Desensitisation and internalisation of the GLP-1 receptor after prolonged agonist exposure are studied because they may shape how responses evolve over time.

Research and clinical-trial landscape

Semaglutide's clinical record is extensive:

• SUSTAIN (type 2 diabetes) included SUSTAIN-6, a cardiovascular safety trial (Marso et al., 2016).
• STEP (obesity and overweight) began with STEP 1, which evaluated body-weight endpoints over 68 weeks in adults without diabetes (Wilding et al., 2021), and included STEP-HFpEF in heart failure with preserved ejection fraction and obesity (Kosiborod et al., 2023).
• SELECT evaluated major adverse cardiovascular events in adults with established cardiovascular disease and overweight or obesity, without diabetes (Lincoff et al., 2023).
• FLOW evaluated kidney outcomes in people with type 2 diabetes and chronic kidney disease (Perkovic et al., 2024).
• ESSENCE evaluated histological endpoints in metabolic dysfunction-associated steatohepatitis (Sanyal et al., 2025).

Semaglutide is also the GLP-1 component of CagriSema, an investigational fixed combination with the amylin analogue cagrilintide. In addition, the phase 3 evoke trials examined semaglutide in early Alzheimer's disease; the sponsor reported in late 2025 that they did not meet their primary endpoint.

Evidence quality and open questions

• High-quality evidence base. Multiple large, randomised, double-blind trials with hard clinical endpoints support semaglutide's approved indications.
• Mechanism of cardiovascular effect. SELECT showed an effect on cardiovascular events, but how much is mediated by body-weight change, glycaemia, blood pressure, inflammation or direct vascular action is still debated.
• Lean mass. As for all agents that reduce body weight, the composition of tissue lost is an active research question.
• Discontinuation. The STEP 1 extension and STEP 4 examined body-weight endpoints after withdrawal, raising questions about long-term maintenance.
• Rare events. Pancreatitis, gallbladder events and ophthalmic signals (including reports of non-arteritic anterior ischaemic optic neuropathy) continue to be studied in pharmacovigilance and observational research.

Regulatory and anti-doping status

Semaglutide is an approved prescription medicine. It is marketed by Novo Nordisk as Ozempic and Rybelsus for type 2 diabetes and as Wegovy for chronic weight management and cardiovascular risk reduction in eligible adults, with further indications added by regulators over time. Regulators including the FDA have warned about unapproved and compounded products. Research-grade semaglutide is not a medicine; it is intended only for in vitro and animal research.

Semaglutide has not been named on the WADA Prohibited List at the time of writing. The list is updated annually and should be checked directly.

Summary table

Property	Semaglutide
Developer	Novo Nordisk
Receptor target	GLP-1R
Basis	Analogue of human GLP-1(7–37)
Length	31 residues
Key modifications	Aib8, Arg34, C18 diacid on Lys26 via γGlu-2xOEG linker
Molecular weight	About 4,113.6 Da
Reported half-life	About seven days
Key programmes	SUSTAIN, STEP, SELECT, FLOW, ESSENCE
Regulatory status	Approved prescription medicine (Ozempic, Rybelsus, Wegovy)
Anti-doping	Not named on WADA list; check current edition

References

• Lau J, Bloch P, Schäffer L, et al. Discovery of the once-weekly glucagon-like peptide-1 (GLP-1) analogue semaglutide. J Med Chem. 2015;58(18):7370–7380.
• Knudsen LB, Lau J. The discovery and development of liraglutide and semaglutide. Front Endocrinol. 2019;10:155.
• Drucker DJ. Mechanisms of action and therapeutic application of glucagon-like peptide-1. Cell Metab. 2018;27(4):740–756.
• Gabery S, Salinas CG, Paulsen SJ, et al. Semaglutide lowers body weight in rodents via distributed neural pathways. JCI Insight. 2020;5(6):e133429.
• Marso SP, Bain SC, Consoli A, et al. Semaglutide and cardiovascular outcomes in patients with type 2 diabetes. N Engl J Med. 2016;375:1834–1844.
• Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384:989–1002.
• Kosiborod MN, Abildstrøm SZ, Borlaug BA, et al. Semaglutide in patients with heart failure with preserved ejection fraction and obesity. N Engl J Med. 2023;389:1069–1084.
• Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med. 2023;389:2221–2232.
• Perkovic V, Tuttle KR, Rossing P, et al. Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes. N Engl J Med. 2024;391:109–121.
• Sanyal AJ, Newsome PN, Kliers I, et al. Phase 3 trial of semaglutide in metabolic dysfunction-associated steatohepatitis. N Engl J Med. 2025.