Semaglutide - Frequently Asked Questions

Per the entry, semaglutide is an acylated GLP-1 receptor agonist: an incretin mimetic and long-acting glucagon-like peptide-1 (GLP-1) analogue. In receptor terms it is a full agonist at the GLP-1 receptor (GLP-1R), a class B (secretin-family) G-protein-coupled receptor that couples to the stimulatory G-protein Galpha-s.

It is a 31-residue analogue of human GLP-1(7-37) with about 94% sequence homology. The pre-modification one-letter backbone reference is H-Aib-EGTFTSDVSSYLEGQAAKEFIAWLVRGRG. It carries an Aib substitution at position 8, an Arg34 substitution, and a C18 fatty-diacid acylation on Lys26 via a gamma-Glu/2x-AEEA (OEG) linker.

The entry lists an average molecular weight of 4113.58 g/mol (reported 4113.58-4113.64, about 4114 Da), a molecular formula of C187H291N45O59, and CAS Registry Number 910463-68-2. The PubChem CID is 56843331 and the DrugBank ID is DB13928.

It targets the GLP-1 receptor (GLP-1R), a class B Gs-coupled GPCR. Receptor activation engages Galpha-s, stimulating adenylate cyclase and raising intracellular cyclic AMP, which is the standard in-vitro readout. Downstream signaling involves PKA and Epac2 pathways, alongside reported beta-arrestin recruitment and Gq-dependent components in GLP-1R-expressing cells.

The entry reports a recombinant GLP-1R binding affinity of approximately 0.38 nM (0.38 +/- 0.06 nM), attributed to Lau et al. 2015 (J Med Chem, PMID 26308095). This is a high-affinity, sub-nanomolar interaction measured in a recombinant receptor system.

Each modification serves a defined biochemical purpose. The alpha-aminoisobutyric-acid (Aib) substitution at position 8 confers resistance to DPP-4 cleavage. The Arg34 substitution directs site-specific acylation to a single lysine. The C18 fatty-diacid chain on Lys26, attached via a gamma-Glu/2x-AEEA/OEG linker, drives reversible albumin binding that prolongs the molecule's residence in vitro.

Cryo-EM of the semaglutide-GLP-1R-Gs complex (Zhang et al. 2021, Cell Reports, PMID 34260945) shows canonical Gs coupling with a sharp kink in transmembrane helix 6, the hallmark of class B receptor activation, with the peptide clasped between the receptor extracellular domain and transmembrane core. Zhang et al. 2017 (Nature, PMID 28538729) provides the activated GLP-1R-G protein structural template.

The four citations cover discovery chemistry and stability (Lau et al. 2015), development and structure-activity context including the 94% homology backbone identity (Knudsen and Lau 2019, PMID 31031702), and cryo-EM structural pharmacology of the receptor-Gs complex (Zhang et al. 2021 and Zhang et al. 2017). The research areas are biochemical, structural, and cell-signaling, not clinical.

As a lyophilized powder, it is reconstituted by adding a measured volume of diluent (commonly bacteriostatic water for multi-use vials) to a known mass, using concentration = mass / volume. For instance, 2 mL into a 5 mg vial gives a 2.5 mg/mL stock. The molecular weight of 4113.58 g/mol converts this to molar terms for assay use. This is laboratory preparation only, not a dosing protocol.

No. The entry does not state a numeric half-life. It instead attributes prolonged molecular residence to two engineered features: Aib8-conferred DPP-4 resistance and C18 fatty-diacid-driven reversible albumin binding. Stability and clearance are therefore described qualitatively through these documented structure-stability relationships rather than a specific duration.

All information here is strictly research-use-only and limited to in-vitro, receptor-signaling, and laboratory-handling contexts. It describes biochemical, structural, and cell-signaling assay observations as characterized in the cited sources, with no human dosing, therapeutic, or disease-treatment claims.