Molecular basis for the long duration of action and kinetic selectivity of tiotropium for the muscarinic M3 receptor.

Abstract

Antagonizing the human M3 muscarinic receptor (hM3R) over a long time is a key feature of modern bronchodilating COPD drugs aiming at symptom relief. The long duration of action of the antimuscarinic drug tiotropium and its kinetic subtype selectivity over hM2R are investigated by kinetic mapping of the binding site and the exit channel of hM3R. Hence, dissociation experiments have been performed with a set of molecular matched pairs of tiotropium on a large variety of mutated variants of hM3R. The exceedingly long half-life of tiotropium (of more than 24 h) is attributed to interactions in the binding site; particularly a highly directed interaction of the ligands' hydroxy group with an asparagine (N508(6.52)) prevents rapid dissociation via a snap-lock mechanism. The kinetic selectivity over hM2R, however, is caused by differences in the electrostatics and in the flexibility of the extracellular vestibule. Extensive molecular dynamics simulations (several microseconds) support experimental results.

• Authors: Christofer S Tautermann, Tobias Kiechle, Daniel Seeliger, Sonja Diehl, Eva Wex, Rolf Banholzer, Florian Gantner, Michael P Pieper, Paola Casarosa
• Journal: Journal of medicinal chemistry (J Med Chem) Vol. 56 Issue 21 Pg. 8746-56 (Nov 14 2013) ISSN: 1520-4804 [Electronic] United States
• PMID: 24088171 (Publication Type: Journal Article)

Chemical References

• Receptor, Muscarinic M3
• Scopolamine Derivatives
• Tiotropium Bromide

Topics

• Binding Sites (drug effects)
• Humans
• Kinetics
• Models, Molecular
• Molecular Dynamics Simulation
• Molecular Structure
• Mutation
• Receptor, Muscarinic M3 (antagonists & inhibitors, genetics, metabolism)
• Scopolamine Derivatives (chemistry, pharmacology)
• Structure-Activity Relationship
• Tiotropium Bromide