| Assay Method Information | |
| | FLIPR assay |
| Description: | The FLIPR assay is an exemplary in vitro assay for measuring the activity of the PAR4 antagonists of the present invention. In this assay, intracellular calcium mobilization is induced in PAR4 expressing cells by a PAR4 agonist and calcium mobilization is monitored. See, e.g., Example A.AYPGKF is a known PAR4 agonist. An alternative PAR4 agonist is H-Ala-Phe(4-F)-Pro-Gly-Trp-Leu-Val-Lys-Asn-Gly-NH2. H-Ala-Phe(4-F)-Pro-Gly-Trp-Leu-Val-Lys-Asn-Gly-NH2 has improved agonist activity as compared to AYPGKF with an EC50 that is 10 fold lower than the EC50 for AYPGKF in the FLIPR assay. H-Ala-Phe(4-F)-Pro-Gly-Trp-Leu-Val-Lys-Asn-Gly-NH2 can be synthesized using methods well known to those of skill in the art.The FLIPR assay can also be used as a counterscreen to test agonist activity or PAR1 antagonist activity in a cell line that expresses both PAR1 and PAR4. The PAR1 antagonist activity can be tested by the ability of the compound to inhibit calcium mobilization induced by the PAR1 agonist peptide SFLLRN or other PAR1 agonist peptides.The compounds of the current invention can be tested in vitro for their ability to inhibit platelet aggregation induced by gamma-thrombin as shown in Example B. Gamma-thrombin, a proteolytic product of alpha-thrombin which no longer interacts with PAR1, selectively cleaves and activates PAR4 (Soslau, G. et al., Unique pathway of thrombin-induced platelet aggregation mediated by glycoprotein Ib , J. Biol. Chem., 276:21173-21183 (2001)). Platelet aggregation can be monitored in a 96-well microplate aggregation assay format or using standard platelet aggregometer. The aggregation assay can also be employed to test the selectivity of the compound for inhibiting platelet aggregation induced by PAR4 agonist peptides, PAR1 agonist peptide, ADP, or thromboxane analogue U46619.Example C is an alpha-thrombin-induced platelet aggregation assay. Alpha-thrombin activates both PAR1 and PAR4. |
| Affinity data for this assay | |
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