Identification and characterization of novel and selective PAR4 antagonist for the treatment of thrombosis

Protease-activated receptor 4 (PAR4), the fourth member of the PAR family, is expressed in platelets. It plays a critical role in platelet activation as well as various of coagulation processes. PAR4 is an important therapeutic target in anti-platelet therapy aimed at reducing the risk of thrombotic complications. In this study, we identified P4i-147, a novel PAR4 antagonist that effectively inhibited PAR4-mediated intracellular calcium increases with an IC 50 of 1.31 µM. P4i-147 exhibited weak inhibitory activity against PAR1-mediated intracellular calcium increases, while showing no inhibitory effect on PAR2-mediated calcium increases. In addition, P4i-147 showed minimal effects on other targets involved in platelet activation. It significantly suppressed PAR4-mediated ERK1/2 phosphorylation without inhibiting PAR1-mediated ERK1/2 phosphorylation. In MEG-01 cells, P4i-147 dose-dependently blocked PAR4-activating peptide (AP)-induced platelet-like shape changes but did not affect those induced by PAR1-AP. Interestingly, in mice, P4i-147 prolonged bleeding time and increased hemoglobin levels and body weight loss through PAR4 inhibition. These findings suggest that P4i-147, as a novel PAR4 antagonist, may have potential therapeutic applications in the treatment of thrombosis. NRF-2018R1A6A1A03023718 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.