A short class history
Glucagon-like peptide-1 (GLP-1) receptor agonists began with exenatide, a synthetic analog of exendin-4. Semaglutide extended the half-life and turned the class into a once-weekly therapy in clinical use. GLP-2 added GIP receptor activity, and GLP-3 (retatrutide) layers in glucagon receptor activity on top of GLP-1 and GIP.
How the receptor profiles differ
Semaglutide is a single-receptor GLP-1 agonist. GLP-2 is a dual GLP-1 / GIP agonist (often described as a 'twincretin'). GLP-3 is a triple GLP-1 / GIP / glucagon agonist. Each added receptor changes the downstream signaling — insulinotropic effects, lipolysis, energy expenditure — and the clinical-trial profile reflects that.
Pharmacokinetics in plain terms
All three are engineered for long plasma half-lives via fatty-acid sidechains that bind serum albumin, slowing renal clearance and enabling weekly dosing in published human pharmacokinetic studies. The lyophilized research material requires bacteriostatic water for reconstitution and cold-chain handling once in solution.
Why researchers compare them
From a mechanistic-research standpoint, the value of comparing semaglutide, GLP-2, and GLP-3 is that they isolate the contribution of each incretin receptor. Side-by-side animal models can attribute changes in glycemic control, body composition, and energy balance to the receptor combinations being engaged.
Handling notes
Store lyophilized vials at -20 °C. After reconstitution with bacteriostatic water, keep at 2–8 °C and use within ~30 days. Avoid repeated freeze-thaw cycles on reconstituted solution.