Tirzepatide

Tirzepatide represents a paradigm shift in metabolic peptide science as the first dual GIP (Glucose-dependent Insulinotropic Polypeptide) and GLP-1 (Glucagon-Like Peptide-1) receptor agonist. By activating both incretin pathways simultaneously, it produces metabolic effects that exceed what either pathway achieves alone.

At the GLP-1 receptor, tirzepatide slows gastric emptying, suppresses glucagon secretion, enhances glucose-dependent insulin release, and activates satiety centres in the hypothalamus — reducing appetite and food intake. At the GIP receptor, it enhances insulin sensitivity in adipose tissue, promotes fat metabolism, and may have direct effects on energy expenditure.

The 39-amino acid peptide is engineered with a C20 fatty diacid moiety that enables albumin binding, extending its half-life to approximately 5 days — allowing once-weekly dosing. Clinical trials have demonstrated unprecedented efficacy in both glycaemic control and weight reduction, with the SURMOUNT-1 trial showing mean weight loss of 22.5% at the highest dose, surpassing all previous pharmacological interventions.

Tirzepatide was developed by Eli Lilly and Company, building on decades of incretin biology research. The concept of dual incretin receptor agonism emerged from observations that GIP and GLP-1 activate complementary metabolic pathways, and that simultaneous activation might produce synergistic benefits.

The SURPASS clinical trial programme (for type 2 diabetes) and SURMOUNT programme (for obesity) established tirzepatide as a breakthrough compound. SURPASS-2 (2021) demonstrated superiority over semaglutide 1mg for HbA1c reduction, while SURMOUNT-1 (2022) showed 22.5% mean body weight reduction — the largest weight loss achieved by any pharmacological agent in a Phase III trial. The FDA approved tirzepatide as Mounjaro (for T2D) in 2022 and Zepbound (for obesity) in 2023.