How Tirzepatide Activates Two Receptors at Once: A Molecular-Level Explanation | Research

The takeaway

Computer simulations reveal that tirzepatide's two ends serve different functions — one end preferentially binds the GIP receptor while the other binds the GLP-1 receptor, explaining its dual action.

2 receptors, 1 peptide
Simulations show tirzepatide's N-terminal preferentially activates GIPR while its C-terminal is critical for GLP-1R — a biased binding mode that explains its dual-agonist profile

What the researchers found

Molecular dynamics simulations revealed how tirzepatide activates both the GLP-1 and GIP receptors. The receptor activation involves a closure-to-open transition in the extracellular domain and movement of transmembrane helices — similar to how simpler class A receptors activate. Tirzepatide's conserved residues bind similarly to both receptors, but mutations in non-conserved residues create a biased binding pattern: C-terminal mutations weaken binding to GLP-1R, while N-terminal mutations strengthen binding to GIPR. This explains tirzepatide's dual-agonist profile at the molecular level.

Why it matters

Tirzepatide (Mounjaro/Zepbound) is the first dual GLP-1/GIP agonist to reach the market, but exactly how a single peptide activates two different receptors wasn't fully understood. This study reveals the molecular details — showing which parts of the tirzepatide molecule are responsible for each receptor interaction. This knowledge is essential for designing the next generation of dual and triple agonist peptide drugs.

The numbers in context

C-terminal mutations weaken GLP-1R binding · N-terminal mutations enhance GIPR binding · ECD closure-open transition observed · Conserved residues bind similarly to both receptors

How the study worked

The researchers used molecular dynamics (MD) simulations to model tirzepatide binding to GLP-1R and GIPR at atomic resolution. They tracked conformational changes in the receptors during activation and inactivation, analyzed binding characteristics at specific residue positions, and performed computational mutation studies to determine how changes in tirzepatide's amino acid sequence affect its affinity for each receptor.

Who was studied

Computational molecular dynamics simulations of tirzepatide-receptor complexes

What this study cannot tell us

This is entirely a computational study — all findings are based on molecular simulations, not experimental measurements of actual binding or receptor activation. Molecular dynamics simulations depend on force field accuracy and simulation timescales, which may not capture all biologically relevant conformational states. The predictions about mutation effects need experimental validation.

How to read the evidence

This is a computational study using molecular dynamics simulations published in a respected macromolecular journal. While the simulations are sophisticated and provide detailed mechanistic insights, the findings are theoretical predictions that require experimental validation.

When this study was published

Published in 2025, this is cutting-edge computational work that builds on the clinical success of tirzepatide to explain its molecular mechanism. The findings are directly relevant to ongoing drug development efforts.

The bigger picture

The success of tirzepatide has sparked a race to develop more multi-receptor agonists — drugs that hit two or three targets at once for greater efficacy. Understanding exactly how tirzepatide binds differently to GLP-1R versus GIPR at the molecular level provides a roadmap for designing next-generation peptides like retatrutide (a triple agonist) and other multi-target drugs in development for obesity and diabetes.

Questions still open

Could this molecular blueprint be used to design a peptide with even stronger GIP receptor activation for greater metabolic benefit?
Do the predicted mutation effects match experimental binding data, or do the simulations need refinement?
Can this same computational approach predict how triple agonists like retatrutide interact with their three target receptors?

Common questions

How does tirzepatide activate two different receptors with one molecule?

Computer simulations show that different parts of the tirzepatide peptide are responsible for binding each receptor. The front end (N-terminal) of the molecule preferentially engages the GIP receptor, while the back end (C-terminal) is critical for the GLP-1 receptor. Shared structural features in the middle bind to conserved parts of both receptors. This allows one molecule to activate two distinct signaling pathways.

Why does this matter for future weight-loss drugs?

Understanding exactly which parts of tirzepatide are responsible for each receptor interaction gives drug designers a molecular blueprint. They can now rationally modify the peptide to shift the balance between GLP-1 and GIP activation, potentially creating drugs that are more effective or have fewer side effects than current options.

Read the original research

Understanding the activation mechanism of GLP-1R/GIPR by dual agonist Tirzepatide via molecular dynamics and protein-peptide binding.

International journal of biological macromolecules, 321(Pt 1), 146141

View on PubMed ↗Publisher’s paper ↗

Citation

Zou, Xuejun; He, Yu; Gao, Ya; Wang, Jian; Zhang, John Z H. (2025). Understanding the activation mechanism of GLP-1R/GIPR by dual agonist Tirzepatide via molecular dynamics and protein-peptide binding.. International journal of biological macromolecules, 321(Pt 1), 146141. https://doi.org/10.1016/j.ijbiomac.2025.146141