TPα and TPβ are two isoforms of the human TP receptor, the G protein-coupled receptor (GPCR) that mediates the actions of thromboxane A2 (TXA2). Although their distinct physiological functions have not been fully elucidated, TPβ is believed to be responsible for vascular endothelial growth factor-induced endothelial cell differentiation and migration whereas TPα appears to be the predominant isoform expressed in platelets. CAY10535 is a TP receptor antagonist that shows ~20-fold selectivity for TPβ (IC50 = 99 nM) relative to TPα (IC50 = 1,970 nM) in the inhibition of U46619-mediated Ca2+ mobilization. This compound exhibits relatively poor activity on platelets (IC50 = 985 nM) when inhibiting U-46619-induced platelet aggregation.