Development of Potent and Selective Inhibitors of Ecto-5'-nucleotidase Based on an Anthraquinone Scaffold

ecto-5'-Nucleotidase (eN, CD73) plays a major role in controlling extracellular adenosine levels. eN inhibitors have potential as novel drugs, for example, for the treatment of cancer. In the present study, we synthesized and investigated a series of 55 anthraquinone derivatives as potential inhibitors of eN, 11 of which are novel compounds and another 11 of which had previously been described but have now been synthesized by an improved method. We identified several potent inhibitors of rat eN. The most potent compounds were 1-amino-4-[4-fluoro-2-carboxyphenylamino]-9,10-dioxo-9,10-dihydroanthracene-2-sulfonate (45, PSB-0952, K(i) = 260 nM) and 1-amino-4-[2-anthracenylamino]-9,10-dioxo-9,10-dihydroanthracene-2-sulfonate (52, PSB-0963, 150 nM), with 52 being the most potent eN inhibitor described to date. Selected compounds were further characterized and found to exhibit a competitive mechanism of inhibition. Investigations of ecto-nucleoside triphosphate diphosphohydrolases (NTPDases) and the P2Y receptor subtypes P2Y(2), P2Y(4), P2Y(6), and P2Y(12) showed that compound 45 exhibited the highest degree of selectivity (>150-fold).