A Second Drug Binding Site in P2X3

Area of Science:

• Structural Biology
• Pharmacology
• Molecular Neuroscience

Background:

• Purinergic P2X3 receptors are critical for chronic cough, affecting over 10% of the population.
• Developing selective P2X3 antagonists is challenging due to conserved receptor structures.
• Camlipixant is a promising P2X3 antagonist in late-stage clinical trials, but its precise binding and inhibition mechanisms are unknown.

Purpose of the Study:

• To determine the high-resolution structure of the P2X3 receptor in complex with camlipixant.
• To elucidate the molecular mechanisms of P2X3 receptor antagonism and allosteric inhibition by camlipixant.
• To understand the structural basis for camlipixant's selectivity over other P2X receptor family members.

Main Methods:

• Established a stable cell line expressing homotrimeric P2X3 receptors.
• Purified the P2X3-camlipixant complex using a peptide scaffold.
• Determined the complex's structure via cryo-electron microscopy (cryo-EM).
• Conducted structure-activity relationship studies, molecular modeling, and simulations.

Main Results:

• Revealed a previously unidentified drug-binding site on the P2X3 receptor for camlipixant.
• Demonstrated that camlipixant acts as an allosteric inhibitor of P2X3.
• Identified key structural features responsible for camlipixant's selective P2X3 antagonism.

Conclusions:

• The study provides the first structural insights into P2X3 receptor antagonism by camlipixant.
• Camlipixant's allosteric inhibition mechanism and selective binding site offer a new understanding of P2X3 targeting.
• These findings pave the way for improved drug design for chronic cough and related conditions.