Uridine Triphosphate Thio Analogues Inhibit Platelet P2Y(12) Receptor and Aggregation

Platelet P2Y(12) is an important adenosine diphosphate (ADP) receptor that is involved in agonist-induced platelet aggregation and is a valuable target for the development of anti-platelet drugs. Here we characterise the effects of thio analogues of uridine triphosphate (UTP) on ADP-induced platelet aggregation. Using human platelet-rich plasma, we demonstrate that UTP inhibits P2Y(12) but not P2Y(1) receptors and antagonises 10 µM ADP-induced platelet aggregation in a concentration-dependent manner with an IC(50) value of ~250 µM. An eight-fold higher platelet inhibitory activity was observed with a 2-thio analogue of UTP (2S-UTP), with an IC(50) of 30 µM. The 4-thio analogue (4S-UTP) with an IC(50) of 7.5 µM was 33-fold more effective. A three-fold decrease in inhibitory activity, however, was observed by introducing an isobutyl group at the 4S- position. A complete loss of inhibition was observed with thio-modification of the γ phosphate of the sugar moiety, which yields an enzymatically stable analogue. The interaction of UTP analogues with P2Y(12) receptor was verified by P2Y(12) receptor binding and cyclic AMP (cAMP) assays. These novel data demonstrate for the first time that 2- and 4-thio analogues of UTP are potent P2Y(12) receptor antagonists that may be useful for therapeutic intervention.