Tirzepatide

A 39-amino-acid first-in-class dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist. Tirzepatide's backbone derives from native GIP, engineered with Aib substitutions at positions 2 and 13 for DPP-4 resistance and a C-20 fatty diacid (eicosanedioic acid) at Lys20 via a γ-Glu + AEEA linker enabling albumin binding and a ~5-day half-life.

FDA-approved for the treatment of type 2 diabetes (Mounjaro, May 2022) and chronic weight management (Zepbound, Nov 2023; expanded Dec 2024 for moderate-to-severe obstructive sleep apnea in adults with obesity). The SURMOUNT-1 trial demonstrated mean weight loss of −20.9% at the 15 mg dose vs −3.1% placebo, with 57% of the 15 mg group losing ≥20% body weight — the largest reductions observed in any pharmaceutical weight-loss trial.

Tirzepatide has been evaluated in the SURPASS program (T2DM) and SURMOUNT program (weight management). SURPASS-1 showed HbA1c reductions of 1.87–2.07% vs +0.04% placebo. SURPASS-2 demonstrated tirzepatide was noninferior and superior to semaglutide 1 mg for both HbA1c and weight. SURMOUNT-1 showed −20.9% weight loss at 15 mg with 57% achieving ≥20% loss.

SURMOUNT-2 confirmed efficacy in obesity with T2DM. Active investigation continues in MASH/NASH (SYNERGY-NASH phase 2: 44–62% resolution), heart failure with preserved ejection fraction (SUMMIT trial), PCOS, and chronic kidney disease. Off-label uses are not FDA-approved and are under clinical investigation.