Sulfated Pentagalloylglucoside Is a Potent, Allosteric, and Selective Inhibitor of Factor XIa

Abstract

Inhibition of factor XIa (FXIa) is a novel paradigm for developing anticoagulants without major bleeding consequences. We present the discovery of sulfated pentagalloylglucoside (6) as a highly selective inhibitor of human FXIa. Biochemical screening of a focused library led to the identification of 6, a sulfated aromatic mimetic of heparin. Inhibitor 6 displayed a potency of 551 nM against FXIa, which was at least 200-fold more selective than other relevant enzymes. It also prevented activation of factor IX and prolonged human plasma and whole blood clotting. Inhibitor 6 reduced VMAX of FXIa hydrolysis of chromogenic substrate without affecting the KM suggesting an allosteric mechanism. Competitive studies showed that 6 bound in the heparin-binding site of FXIa. No allosteric small molecule has been discovered to date that exhibits equivalent potency against FXIa. Inhibitor 6 is expected to open up a major route to allosteric FXIa anticoagulants with clinical relevance.

Plasmin Regulation through Allosteric, Sulfated, Small Molecules

“…Both mechanisms arise from allosteric binding of NSGMs 32 and 52 to plasmin. Thus, the NSGMs studied in this work parallel the growing class of allosteric inhibitors of heparin-binding enzymes reported in the literature to date, such as low molecular weight lignins [27], sulfated benzofurans [34,35], sulfated tetrahydroisoquinolines [36], sulfated quinazolinones [37], and sulfated pentagalloyl glucopyranoses [38,39]. …”

“…We reasoned that small, synthetic, homogenous, non-saccharide GAG mimetics (NSGMs) may offer an avenue for discovering novel plasmin inhibitors. In fact, Desai and co-workers have developed a sizeable number of NSGMs based on various scaffolds including sulfated flavonoids [30][31][32][33], sulfated benzofurans [34,35], sulfated tetrahydroisoquinolines [36], sulfated quinazolinones [37] and sulfated galloyl glucopyranosides [38,39] as modulators of a range of coagulation proteins. The NSGMs resemble sulfated GAGs in the form of presenting one or more sulfate groups to interact with GAG-binding domains on targeted proteins.…”

“…The monomeric scaffolds included chalcones (compounds 1-10), flavonoids (11)(12)(13)(14)(15)(16) [30][31][32], sucrose octasulfate (17) [40], quinazolinones (18 and 19) [37], and tetrahydro-isoquinolines (20)(21)(22)(23)(24)(25)(26)(27) [36], whereas the dimeric scaffolds comprised flavonoid-quinazolinone heterodimers (28)(29)(30)(31)(32)(33)(34) [37], bis-quinazolinones homodimers (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47) [37], and bis-flavonoid homodimers (48-55). In addition to the inherent diversity of the scaffolds in this library, NSGMs also differed in the number (1 to 8) and orientation of the sulfate groups.…”

“…Briefly, the synthesis of these NSGMs was achieved in 4 to 8 steps using traditional protection-deprotection chemistry following construction of the base scaffold with appropriate substitution pattern. The final step for the generation of each NSGM was chemical sulfation using trimethylamine-sulfur trioxide at elevated temperature, as described in our studies earlier [30][31][32][33][34][35][36][37][38][39][40][41][42]. For example, the synthesis of two promising plasmin inhibitors (Scheme 1) involved exploitation of the intramolecularly hydrogen bonded 5-OH group of quercetin 60 to selectively introduce a reactive handle (propargyl group in 63 or in situ alkyl bromide) that can be coupled with either an alkyl azide containing quinazolinone unit 32a or MOM-protected quercetin 61 to eventually give inhibitors 32 and 52, respectively.…”

“…Sulfation of polyphenolic precursors was achieved using microwave assisted chemical sulfation as described earlier [30][31][32][33][34][35][36][37][38][39][40][41][42]. Briefly, to a stirred solution of polyphenol in anhydrous CH3CN (1-5 mL) at room temperature, Et3N (10 equivalents per -OH group) and Me3N:SO3 complex (6 equivalents per -OH) was added.…”