Tirzepatide — Dual GIP/GLP-1 Agonist

Background

Tirzepatide is a once-weekly synthetic peptide engineered by Eli Lilly that acts as a dual agonist of the GIP and GLP-1 receptors. It is licensed as Mounjaro® for type 2 diabetes and as Zepbound® for chronic weight management.

Mechanism

Tirzepatide is a 39-amino-acid linear peptide with a C20 fatty-diacid side-chain conferring albumin binding and a long half-life (~5 days). Dual GIP/GLP-1 activation produces synergistic incretin effects with greater glycaemic and weight outcomes than GLP-1-only agonists in head-to-head trials.

What is proven

The SURPASS program (Phase 3 in T2D) demonstrated superior HbA1c and weight reduction versus placebo, semaglutide 1 mg, insulin glargine and insulin degludec. SURPASS-2 (NEJM 2021) reported HbA1c reductions of 2.01–2.30% and weight loss of 7.6–11.2 kg across 5/10/15 mg doses.

The SURMOUNT-1 trial (NEJM 2022) reported mean body-weight reductions of 20.9% at 72 weeks on 15 mg weekly tirzepatide in adults with obesity without T2D. SURMOUNT-2 confirmed efficacy in adults with T2D and obesity.

SURMOUNT-MMO (2024) reported cardiovascular outcome signals consistent with class effect.

What is NOT proven (for research-grade material)

Same caveats as semaglutide — research-grade tirzepatide is not a licensed medicine and is not manufactured to pharmacopoeial standards. Long-term lean-mass, bone-density and gastrointestinal-motility effects continue to be characterised even for the licensed product.

Open research questions

Definitive cardiovascular outcomes (the SURPASS-CVOT trial is ongoing), long-term durability of weight loss, MASH/NASH liver outcomes (SYNERGY-NASH read out positively in 2024), and head-to-head comparison with triple-agonist retatrutide.

Regulatory status

Approved by the FDA, EMA, MHRA and others for type 2 diabetes (2022) and chronic weight management (2023, as Zepbound/Mounjaro for weight depending on jurisdiction).

All Proteus® compounds are sold strictly for in-vitro research. Nothing on this page is medical advice, a treatment claim, or a recommendation for human use. Where compounds are licensed medicines in any jurisdiction, that approval applies to the licensed product supplied through a regulated pharmacy — not to research-grade material.