Ecnoglutide: Molecular Structure

Molecular Structure and Properties#

Ecnoglutide (XW003) is a 31-amino acid synthetic peptide analog of human GLP-1(7-37), developed by Sciwind Biosciences. It has a molecular formula of C194H304N48O61 and CAS number 2459531-73-6. The molecule was engineered through systematic optimization of the native GLP-1 sequence to achieve three goals: DPP-4 resistance, prolonged duration of action through albumin binding, and deliberate cAMP signaling bias at the GLP-1 receptor.

Amino Acid Sequence#

The primary structure of ecnoglutide is based on the native human GLP-1(7-37) sequence with key modifications:

His-Val-EGTFTSDVSSYLEEQAAREFIAWLVRGRG

with a C18 fatty diacid (octadecanedioic acid) conjugated at the lysine residue at position 26 via a gamma-glutamic acid spacer and dual AEEA (aminoethyloxy-acetyl) linker.

Key structural features and their significance:

• Position 1 (Histidine): Retained from native GLP-1; essential for GLP-1 receptor binding and activation
• Position 2 (Valine): Replaces native alanine. Unlike semaglutide which uses the non-natural amino acid alpha-aminoisobutyric acid (Aib) at this position, ecnoglutide uses the natural amino acid valine. This substitution provides DPP-4 resistance while maintaining cAMP signaling bias and simplifying manufacturing since no non-natural amino acids are required
• Position 26 (Lysine): Conjugation site for the C18 fatty diacid moiety, attached through a gamma-glutamic acid spacer and dual AEEA (2-[2-(2-aminoethoxy)ethoxy]acetyl) linker. This modification enables non-covalent albumin binding for extended half-life
• Entire sequence: Composed exclusively of natural amino acids, which is a notable manufacturing advantage over peptides containing non-natural residues

Biased Signaling Profile#

The most distinctive molecular feature of ecnoglutide is its signaling bias at the GLP-1 receptor. In vitro characterization shows:

• cAMP induction: EC50 = 0.018 nM (highly potent)
• Receptor internalization: EC50 > 10,000 nM (negligible)
• Bias factor: Greater than 500,000-fold preference for cAMP signaling over receptor internalization

This extreme bias means ecnoglutide activates the therapeutic cAMP pathway at concentrations far below those needed to trigger receptor internalization. In contrast, semaglutide and liraglutide activate both pathways at similar concentrations, leading to receptor downregulation with chronic dosing. The structural basis for this bias is attributed to the valine substitution at position 2 and the specific fatty acid linker geometry.

Lipid Modification and Albumin Binding#

The C18 fatty diacid conjugated at Lys26 serves the same general purpose as in semaglutide: enabling non-covalent albumin binding for extended circulating half-life. The linker design uses a gamma-glutamic acid spacer with two AEEA (aminoethyloxy-acetyl) units, providing hydrophilicity to offset the lipophilicity of the C18 chain.

Pharmacokinetics#

Ecnoglutide exhibits pharmacokinetic properties suitable for once-weekly dosing.

Half-life: At steady state, the half-life ranges from 124 to 138 hours (approximately 5.2-5.8 days), as determined in the Phase 1 clinical trial. This is slightly shorter than semaglutide's half-life of approximately 168 hours but adequate for weekly dosing.

Albumin binding: The C18 diacid modification provides high-affinity albumin binding, creating a circulating depot that protects the peptide from renal filtration and proteolytic degradation.

Dose proportionality: Pharmacokinetic data from Phase 1 studies demonstrated dose-proportional exposure across the tested dose range.

Structural Comparison with Related Peptides#

• vs. Semaglutide: Both are C18 diacid-modified GLP-1(7-37) analogs with similar linker strategies. The key difference is at position 2: semaglutide uses non-natural Aib while ecnoglutide uses natural valine. This substitution, combined with other design choices, produces ecnoglutide's marked cAMP bias versus semaglutide's relatively balanced signaling
• vs. Liraglutide: Liraglutide uses a shorter C16 fatty acid at Lys26 without a PEG spacer, yielding a half-life of only approximately 13 hours. Ecnoglutide's C18 diacid with dual AEEA linker provides stronger albumin binding and a much longer half-life
• vs. Tirzepatide: Tirzepatide is a dual GIP/GLP-1 agonist with a fundamentally different mechanism. Ecnoglutide is a selective GLP-1 agonist with biased signaling, representing a different approach to improving therapeutic outcomes

Related Reading#

• Ecnoglutide overview and research guide
• Peptides similar to Ecnoglutide
• Ecnoglutide research evidence