Vorapaxar (MK-5348) (SCH 530348) is an effective and orally active thrombin receptor (PAR-1) antagonist (Ki: 8.1 nM).

PAR1:8.1 nM(Ki)

Vorapaxar is a synthetic tricyclic 3-phenylpyridine and an orally active himbacine-based thrombin-receptor antagonist. Vorapaxar shows potent inhibition of thrombin-induced platelet aggregation with an IC50 of 47 nM and haTRAP-induced platelet aggregation with an IC50 of 25 nM, whereas it shows no inhibition of platelet aggregation induced by other agonists such as ADP, collagen and a PAR-4 agonist peptide. Vorapaxar also has no affect on the prothrombin time (PT), partial thromboplastin time (PTT), or activated partial thromboplastin time (aPTT). Moreover, Vorapaxar causes no increase in the bleeding time or in surgical bleeding compared with inactive control. SCH530348 is found to be selective for PAR-1 when tested over a number of ion channels and receptors, including PAR-4 receptor. [1]

Vorapaxar is well absorbed in rat (68%; 10 mg/kg) and in monkey (82%; 1 mg/kg) models. Tmax is observed at about 3 h in rats and 1 h in monkeys. The elimination half-life is 5.1 h in rats and 13 h in monkeys. The oral bioavailability is 33% in rats and 86% in monkeys. In preclinical studies in cynomolgus monkey platelets, oral administration of Vorapaxar at a dose greater than 0.1 mg/kg resulted in 100% inhibition of thrombin-receptor agonist peptide (TRAP)-induced platelet aggregation for 24 h with partial recovery occurring at 48 h. [1]