Structure–Affinity Relationships and Structure–Kinetics Relationships of Pyrido[2,1‑<i>f</i>]purine-2,4-dione Derivatives as Human Adenosine A₃ Receptor Antagonists

We
expanded on a series of pyrido­[2,1-f]­purine-2,4-dione
derivatives as human adenosine A3 receptor (hA3R) antagonists to determine their kinetic profiles and affinities.
Many compounds showed high affinities and a diverse range of kinetic
profiles. We found hA3R antagonists with very short residence
time (RT) at the receptor (2.2 min for 5) and much longer
RTs (e.g., 376 min for 27 or 391 min for 31). Two representative antagonists (5 and 27) were tested in [35S]­GTPγS binding assays, and
their RTs appeared correlated to their (in)­surmountable antagonism.
From a kon–koff–KD kinetic map, we divided
the antagonists into three subgroups, providing a possible direction
for the further development of hA3R antagonists. Additionally,
we performed a computational modeling study that sheds light on the
crucial receptor interactions, dictating the compounds’ binding
kinetics. Knowledge of target binding kinetics appears useful for
developing and triaging new hA3R antagonists in the early
phase of drug discovery.