GLP‑1 Receptor Agonist Pharmacology and Clinical Efficacy

Regulatory Approvals and Dosing

Exenatide was the first GLP‑1 receptor agonist approved by the U.S. Food and Drug Administration in 2005; it shares ≈ 50 % homology with endogenous GLP‑1 and is resistant to dipeptidyl‑peptidase‑4 (DPP‑4) cleavage【1】.
Liraglutide (Victoza) received FDA approval for a daily 3 mg dose for weight‑loss therapy in adults with a body‑mass index > 30 kg/m² or > 27 kg/m² with obesity‑related comorbidities【2】.
Semaglutide (Ozempic/Wegovy) was approved in 2021 for weekly 2.4 mg dosing for weight‑loss indication, leveraging its higher albumin‑binding affinity compared with liraglutide【3】【2】.

All GLP‑1 receptor agonists have been chemically modified to prevent rapid cleavage and inactivation by DPP‑4, thereby extending their pharmacologic activity【3】.
Long‑acting agents achieve extended elimination half‑lives through distinct molecular strategies:
- Albumin binding (semaglutide, albiglutide)
- Immunoglobulin Fc‑fragment conjugation (dulaglutide)
- Microsphere encapsulation (exenatide once‑weekly)【3】.

Exenatide once‑weekly is formulated in biodegradable microspheres that provide sustained subcutaneous release over seven days【3】.
Dulaglutide is engineered by conjugating the peptide to the fragment crystallisable (Fc) region of IgG, markedly prolonging its systemic elimination【3】.
Albiglutide attains prolonged activity via non‑covalent conjugation to albumin, reducing renal clearance【3】.

Tirzepatide simultaneously activates GIP and GLP‑1 receptors and demonstrates superior reductions in glycated hemoglobin (HbA1c) and body weight compared with selective GLP‑1 agonists such as semaglutide and dulaglutide【1】.
Although tirzepatide binds the GIP receptor with high affinity, its affinity for the GLP‑1 receptor is approximately five‑fold lower than that of endogenous GLP‑1【1】.
In non‑diabetic obese participants receiving the 15 mg dose, tirzepatide produced a mean weight loss of ≈ 20.9 % after 72 weeks of treatment【2】.

Short‑acting GLP‑1 receptor agonists (e.g., exenatide) require at least once‑daily subcutaneous administration to maintain therapeutic effect【3】.

The American Diabetes Association recommends the use of GLP-1 receptor agonists, such as Byetta (exenatide) and Lyxumia (lixisenatide), for the treatment of type 2 diabetes, with Byetta available as a twice-daily subcutaneous injection and Lyxumia as a once-daily subcutaneous injection 4, 5
The European Association for the Study of Diabetes suggests that long-acting GLP-1 receptor agonists, including Victoza (liraglutide), Byetta (exenatide once-weekly), Trulicity (dulaglutide), Ozempic/Wegovy (semaglutide), and Eperzan (albiglutide), can be used for both diabetes and weight loss, with varying elimination half-lives and dosing regimens 4, 5

The American College of Endocrinology notes that Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist that demonstrates superior efficacy compared to selective GLP-1 receptor agonists, producing greater reductions in HbA1c and body weight in patients with type 2 diabetes mellitus 6