Atopaxar hydrobromide  (Synonyms: E5555 hydrobromide; ER 172594-06)

Atopaxar (E5555) hydrobromide is a potent, orally active, selective and reversible thrombin receptor protease-activated receptor-1 (PAR-1) antagonist. Atopaxar hydrobromide, an antiplatelet agent, interferes with platelet signaling. Atopaxar hydrobromide can be used for the research of atherothrombotic disease^[1][2].

Atopaxar hydrobromide (0.0001-10 μM; 1h) inhibits haTRAP (high-affinity thrombin receptor activating peptide) binding to PAR-1 on human platelet membranes in a concentration-dependent manner, with an IC₅₀ of 0.019 μM^[2].
Atopaxar hydrobromide shows potent inhibitory effects on human platelet aggregation induced by thrombin and TRAP with IC₅₀s of 0.064 and 0.031 μM, respectively, but has no effect on platelet aggregation induced by either ADP or collagen^[2].
Atopaxar hydrobromide shows potent and selective inhibitory effects on guinea pig platelet aggregation induced by thrombin and TRAP with IC₅₀s of 0.13 and 0.097 μM, respectively^[2].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Atopaxar (30-100 mg/kg; p.o.) hydrobromide causes a dose-dependent prolongation of the time to occlusion of the femoral artery in photochemically-induced thrombosis (PIT) guinea pigs model^[2].
Atopaxar hydrobromide does not prolong bleeding time in guinea pigs at the highest tested dosage of 1000 mg/kg^[2].

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

608.54

C₂₉H₃₉BrFN₃O₅

474550-69-1

Room temperature in continental US; may vary elsewhere.

Please store the product under the recommended conditions in the Certificate of Analysis.

• [1]. Chris Dockendorff, et al. Discovery of 1,3-Diaminobenzenes as Selective Inhibitors of Platelet Activation at the PAR1 Receptor. ACS Med Chem Lett. 2012 Mar 8; 3(3): 232–237.  [Content Brief]

  [2]. Motoji Kogushi, et al. The novel and orally active thrombin receptor antagonist E5555 (Atopaxar) inhibits arterial thrombosis without affecting bleeding time in guinea pigs. Eur J Pharmacol. 2011 Apr 25;657(1-3):131-7.  [Content Brief]

  [3]. Sun J, et al., Discovery and evaluation of Atopaxar hydrobromide, a novel JAK1 and JAK2 inhibitor, selectively induces apoptosis of cancer cells with constitutively activated STAT3. Invest New Drugs. 2020 Aug;38(4):1003-1011.  [Content Brief]