Liraglutide

1 Identity

Acylated lipopeptide, not a plain peptide. A 31-residue GLP-1-derived backbone carrying a C16 fatty acyl group on a gamma-glutamyl spacer. Incretin receptor agonist by class. It is the active ingredient of FDA-approved drug products, including approved generics since 2024. so a purchase order citing only one is under-specified. both commonly published and neither independently verified for this entry; the free base and the acetate carry different registry numbers. liraglutide free base CAS 204656-20-2 and liraglutide acetate CAS 1997361-86-0. Trade names of the approved US drug products in which liraglutide is the active ingredient are not used as aliases in this catalog, and no record here names an indication for this molecule. Not synonyms, and each a different article: semaglutide, the des-acyl liraglutide backbone, and GLP-1(7-37) itself.

Sequence

Backbone: H-His-Ala-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Val-Ser-Ser-Tyr-Leu-Glu-Gly-Gln-Ala-Ala-Lys-Glu-Phe-Ile-Ala-Trp-Leu-Val-Arg-Gly-Arg-Gly-OH; one-letter HAEGTFTSDVSSYLEGQAAKEFIAWLVRGRG, 31 residues, being human GLP-1(7-37) with a single Lys34Arg substitution in GLP-1 numbering, which is chain position 28 of the 31-mer. A hexadecanoyl (C16 palmitoyl) chain is attached through an L-gamma-glutamyl spacer to the epsilon-amino group of Lys26 in GLP-1 numbering, which is chain position 20 of the 31-mer. Both numberings are stated together, GLP-1 Lys26 being chain position 20 and GLP-1 Lys34Arg being chain position 28, so that a supplier and a buyer using different numbering conventions cannot silently disagree. Free N-terminal alpha-amine, free C-terminal carboxylic acid, no amidation, no cysteine, no disulfide, no non-proteinogenic residue in the backbone. The acyl group and its spacer are approximately 9.8 percent of the molecular mass and are the entire basis of the molecule's design; a description giving only the residue count describes a different substance and leaves a release panel with no des-acyl, over-acyl or positional-isomer control.

Molecular formula

C172H265N43O51 (free base). Mono-acetate salt C174H269N43O53. Des-acyl backbone C151H228N42O47. Semaglutide, for separation on paper, C187H291N45O59.

Average mass

3,751.262 Da free base (C172H265N43O51), on IUPAC 2021 abridged conventional atomic weights. Listings commonly print 3,751.20; the formula gives 3,751.262, and the difference is an atomic-weight revision rather than a discrepancy. Mono-acetate C174H269N43O53 is 3,811.31, which reconciles with one institutional supplier's printed 3,811.3 for the acetate article to within 0.02 Da. Des-acyl backbone C151H228N42O47 is 3,383.73, that is 367.53 Da lighter. Semaglutide C187H291N45O59 is 4,113.64, that is 362.38 Da heavier. Figures of 3,383.68 for the des-acyl backbone and 4,113.58 for semaglutide also circulate; the formulas give 3,383.73 and 4,113.64, and the two deltas that matter, 367.53 Da to the des-acyl species and 362.38 Da to semaglutide, are stated on the formula-derived figures.

Monoisotopic mass

3,748.94646 Da neutral free base. [M+3H]3+ 1,250.65610; [M+4H]4+ 938.24389; [M+5H]5+ 750.79825. In practice a 3.75 kDa conjugate is released on deconvoluted average mass from a multiply-charged ESI envelope rather than on a monoisotopic peak, and the certificate should print the charge states used. Des-acyl backbone 3,381.67420 monoisotopic; semaglutide 4,111.11538.

Salt / variant note

Four articles, one of which is among the highest-probability substitutions in the entire catalog. (1) Liraglutide free base, C172H265N43O51, 3,751.26 average / 3,748.94646 monoisotopic. (2) Mono-acetate C174H269N43O53, 3,811.31 / 3,808.96759, carrying a different CAS number from the free base, so an order citing one registry number is under-specified. (3) des-acyl backbone, the unacylated 31-mer C151H228N42O47, 3,383.73 / 3,381.67420, which is 367.53 Da lighter and the single most important limit on any certificate for this molecule, because it is a different substance with the entire design feature missing and it is exactly what a failed or partial acylation step produces. (4) semaglutide, C187H291N45O59, 4,113.64 / 4,111.11538, formula corroborated at PubChem CID 56843331 and on a reagent catalog datasheet for CAS 910463-68-2, which is 362.38 Da heavier, a different backbone and a different acyl, and the molecule most likely to be in a vial sold under any GLP-1 label. (5) Over-acylated species and acylation positional isomers, with acyl on the wrong lysine or on the N-terminal alpha-amine, are exactly isobaric with the correct molecule and are invisible to intact mass at any resolution; only peptide mapping reaches them. (6) Trp25-oxidized species, 15.99 Da heavier, Trp being the one classically oxidation-labile residue in the chain.

2 Class & testing panel

Form

Single article

Testing panel

P2 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Published literature exists and is very large. What exists, by study type and identifier: multiple completed Phase 3 programs; a dedicated cardiovascular outcomes trial (LEADER, ClinicalTrials.gov identifier NCT01179048); FDA and EMA review documents including the approved labeling, which carries a boxed warning; more than a decade of post-marketing surveillance and pharmacovigilance reporting; and, since 2024, abbreviated new drug application review records for approved generics. The regulatory review documents and the outcomes trial are indexed. No statement is made anywhere in this record about what the molecule does; the entries above record which documents exist and under which identifiers.

4 Storage & specification

Storage

Held as the lyophilized solid at -20 degrees C plus or minus 5 degrees C, desiccated and protected from light, in low-adsorption glass with a desiccant sachet and a tamper-evident closure, with the adsorption behavior of an acylated conjugate treated as an analytical problem rather than a cosmetic one: the recovered concentration in a dilute solution depends on the container as much as on the peptide.

Shelf life

Each lot is dated from its date of manufacture and carries a retest date on its certificate, set on the company's own stability data for the lot. The attributes that govern the interval are des-acyl content, which is the single most important limit on any certificate for this molecule, and oxidation at Trp, the one classically oxidation-labile residue in the chain. Acylation positional isomers are exactly isobaric with the parent, so they are followed by peptide mapping rather than by intact mass.