Originally identified in Gila monster lizard (Heloderma suspectum), exendin-4 is an incretin mimetic, an analog of glucagon-like-peptide-1 (GLP-1), it stimulates insulin secretion and modulates gastric emptying to slow the entry of ingested sugars into the bloodstream. Exendin-4 is resistant to cleavage by plasma DPP-IV unlike GLP-1. This gives it a longer half-life and duration of action than GLP-1, as well as greater potency in vivo. Exendin-4 increases insulin sensitivity and improves glucose tolerance and is currently used for the treatment of Type 2 diabetes mellitus in its synthetic form Exenatide.

Exendin-4 also promotes the production and proliferation of β-cells leading to regeneration of the pancreas. It is a ligand to the exendin receptor and increases pancreatic acinni cAMP levels. However, the GLP-1 analog was found to have a toxic effect by inducing hypotension due to relaxation of the cardiac smooth muscle.

The leucine residues at positions 10, 21, and 26 of this peptide are isotopically labelled with carbon-13 and nitrogen-15, giving this peptide a mass increase of 18.5 compared to the unlabelled peptide