PSB 10

PSB-10 is a drug which acts as a selective antagonist for the adenosine A₃ receptor (k_i value at human A₃ receptor is 0.44 nM), with high selectivity over the other three adenosine receptor subtypes (k_i values at human A₁, A_2A and A_2B receptors are 4.1, 3.3 and 30 µM). Further pharmacological experiments in a [³⁵S]GTPγS binding assay using hA₃-CHO-cells indicated that PSB-10 acts as an inverse agonist (IC₅₀ = 4 nM). It has been shown to produce antiinflammatory effects in animal studies. Simple xanthine derivatives such as caffeine and DPCPX have generally low affinity for the A₃ subtype and must be extended by expanding the ring system and adding an aromatic group to give high A₃ affinity and selectivity. The affinity towards adenosine A₃ subtype was measured against the radioligand PSB-11.