High-affinity, non-nucleotide-derived competitive antagonists of platelet P2Y₁₂ receptors

Anthraquinone derivatives related to the moderately potent, nonselective P2Y₁₂ receptor antagonist reactive blue 2 (6) have been synthesized and optimized with respect to P2Y₁₂ receptor affinity. A radioligand binding assay utilizing human blood platelet membranes and the P2Y₁₂ receptor-selective antagonist radioligand [³H]2-propylthioadenosine- 5′-adenylic acid (1,1-dichloro-1-phosphonomethyl-1-phosphonyl) anhydride ([³H]PSB-0413) was applied for compound testing. 1-Amino-2- sulfoanthraquinone derivatives bearing a (p-phenylamino) anilino substitution in the 4-position and an additional acidic function in the meta-position of the aniline ring showed high P2Y₁₂ receptor affinity. These new anthraquinone derivatives became accessible by a recently developed copper(0)-catalyzed Ullmann coupling reaction of 1-amino-4-bromoanthraquinone derivatives with anilines in phosphate buffer under microwave irradiation. The most potent compounds exhibited K_i values of 24.9 nM (1-amino-4-[4-phenylamino-3-sulfophenylamino]-9,10-dioxo-9,10-dihydroanthracene- 2-sulfonate, PSB-0739, 39), and 21.0 nM (1-amino-4-[4-phenylamino-3- carboxyphenylamino]-9,10-dioxo-9,10-dihydroanthracene-2-sulfonate, PSB-0702, 41), respectively. 1-Amino-2-sulfo-4-anilinoanthraquinone derivatives appeared to be noncytotoxic, as shown for selected derivatives at two human cell lines (melanoma and astrocytoma). Compounds 39 and 41 represent new lead structures for the development of antithrombotic drugs.