Equilibrium and kinetic selectivity profiling on the human adenosine receptors

Area of Science:

• Pharmacology and Medicinal Chemistry
• Drug Discovery and Development
• Biophysics and Molecular Interactions

Background:

• Traditional drug target selectivity assessment relies solely on equilibrium binding affinity.
• Ligand-receptor interaction kinetics are often overlooked in early drug discovery.
• Adenosine receptors (ARs) are a key target class in various therapeutic areas.

Purpose of the Study:

• To propose and validate a combined strategy for assessing drug target selectivity using both equilibrium and kinetic profiling.
• To evaluate AR antagonists for their affinity and kinetic selectivity across different AR subtypes.
• To investigate the functional consequences of kinetic selectivity in AR antagonists.

Main Methods:

• Radioligand displacement assays were used to determine binding affinity (equilibrium).
• Competition association assays were employed to measure binding kinetics.
• Functional activity was assessed using a [(35)S]-GTPγS binding assay.

Main Results:

• Compounds XAC and LUF5964 demonstrated kinetic selectivity for A1R and A3R, respectively, despite lacking equilibrium-based selectivity.
• LUF5967 showed equilibrium-based selectivity for A1R over A2AR, but less pronounced kinetic selectivity.
• LUF5964 exhibited insurmountable antagonism on A3R and surmountable antagonism on A1R, correlating with its kinetic profile.

Conclusions:

• Both equilibrium and kinetic selectivity profiling are crucial in early drug discovery.
• The proposed combined strategy can enhance the design and discovery of novel drug leads.
• Kinetic selectivity offers a valuable dimension for optimizing AR antagonist profiles for clinical applications.