Avexitide

Mechanism

Avexitide is a 31-amino-acid peptide comprising residues 9-39 of exendin-4. Exendin-4 is a 39-amino-acid peptide isolated from the saliva of the Gila monster (Heloderma suspectum) that acts as a potent GLP-1 receptor agonist (the basis for the drug exenatide). By removing the N-terminal eight amino acids (the activation domain), the resulting exendin(9-39) retains high binding affinity for the GLP-1 receptor but cannot activate it — functioning as a competitive antagonist. Avexitide blocks GLP-1-mediated stimulation of insulin secretion from pancreatic beta cells, counteracting the excessive insulin response that characterises post-bariatric hypoglycaemia. It also blocks GLP-1's effects on gastric emptying and glucagon suppression, though the therapeutic benefit in PBH is primarily through insulin secretion modulation.

Evidence base

Key Published Trials

1. PBH proof-of-concept (Salehi M, et al. Journal of Clinical Endocrinology & Metabolism. 2014;99(11):4203-4206): Randomised, double-blind, placebo-controlled crossover trial in 10 patients with PBH. Avexitide infusion reduced postprandial insulin and improved glycaemic nadir. 6/10 patients protected from hypoglycaemia.

2. PBH subcutaneous study (Salehi M, et al. Diabetes Care. 2018;41(4):e34-e35): Extended findings with subcutaneous administration, demonstrating feasibility for outpatient use.

3. Congenital hyperinsulinism (Calabria A, et al. Journal of Clinical Endocrinology & Metabolism. 2022): Pilot study showing avexitide reduced insulin secretion in a subset of CHI patients.

4. Mechanistic basis: Exendin(9-39) was first characterised as a GLP-1 receptor antagonist by Eng J, et al. (Journal of Biological Chemistry. 1990;265(32):19631-19637).

Limitations

All trials are small (n=10 to n=20), and no Phase 3 trials have been completed. The crossover design provides robust within-patient comparisons but limits generalisability. Long-term safety data are lacking.

Protocols

Avexitide has been administered in clinical trials only:

• Intravenous infusion: Used in proof-of-concept studies during mixed-meal tolerance testing (Salehi et al., 2014)
• Subcutaneous injection: Investigated in follow-up studies for outpatient feasibility (Salehi et al., 2018)

No standardised dosing protocol exists outside clinical trials. Avexitide is an investigational compound and is not available for self-directed research use. No research peptide vendor sells avexitide for human use.

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UK legal status

Avexitide is classified as a UK grey area. It is not a licensed medicine, not a controlled substance, and not specifically regulated as a research chemical.

Key points:

• MHRA status: Not approved; any product making medicinal claims would be classified as an unlicensed medicinal product
• Clinical trial use: Only permitted within the framework of an MHRA-approved clinical trial
• Research chemical availability: Bulk exendin(9-39) may be available from international research chemical suppliers for in vitro / laboratory use only
• Human use outside trials: Not sanctioned; would be experimental and unregulated

This compound is included in the Peptide Data knowledge base for educational completeness, given its significance as the only GLP-1 receptor antagonist peptide under active clinical investigation.