The cubic ternary complex receptor-occupancy model. III. resurrecting efficacy

Area of Science:

• Pharmacology
• Biochemistry
• Computational Biology

Background:

• Traditional pharmacology uses affinity and efficacy (bipartite view) for receptor-ligand interactions.
• Existing efficacy models are limited, particularly for complex systems involving receptor activation and signaling.
• A more comprehensive understanding is needed for intricate pharmacological processes.

Purpose of the Study:

• To extend the concept of efficacy to models incorporating receptor activation and G-protein coupling.
• To propose a new framework distinguishing potential and realized efficacy.
• To re-evaluate the bipartite view in light of these extended concepts.

Main Methods:

• Utilized the cubic ternary complex model for analysis.
• Defined potential efficacy as a vector of part-worth utilities assigned to each receptor species.
• Defined realized efficacy as the expectation of these utilities based on receptor species distribution.

Main Results:

• Efficacy is not solely a ligand-receptor property but depends on receptor species distribution.
• Introduced potential efficacy (vector) and realized efficacy (scalar).
• Realized efficacy represents the utility of ligand binding as a random prospect.

Conclusions:

• The extended definition of efficacy provides a more accurate representation of drug action in complex systems.
• The bipartite view's limitations are highlighted, suggesting a need for revised pharmacological models.
• This framework has implications for understanding agonism and drug efficacy assessment.