Discovery of 1-[3-(Aminomethyl)phenyl]-N-[3-fluoro-2‘-(methylsulfonyl)- [1,1‘-biphenyl]-4-yl]-3-(trifluoromethyl)-1H-pyrazole-5-carboxamide (DPC423), a Highly Potent, Selective, and Orally Bioavailable Inhibitor of Blood Coagulation Factor Xa

Abstract

Factor Xa (fXa) plays a critical role in the coagulation cascade, serving as the point of convergence of the intrinsic and extrinsic pathways. Together with nonenzymatic cofactor Va and Ca2+ on the phospholipid surface of platelets or endothelial cells, factor Xa forms the prothrombinase complex, which is responsible for the proteolysis of prothrombin to catalytically active thrombin. Thrombin, in turn, catalyzes the cleavage of fibrinogen to fibrin, thus initiating a process that ultimately leads to clot formation. Recently, we reported on a series of isoxazoline and isoxazole monobasic noncovalent inhibitors of factor Xa which show good potency in animal models of thrombosis. In this paper, we wish to report on the optimization of the heterocyclic core, which ultimately led to the discovery of a novel pyrazole SN429 (2b; fXa K(i) = 13 pM). We also report on our efforts to improve the oral bioavailability and pharmacokinetic profile of this series while maintaining subnanomolar potency and in vitro selectivity. This was achieved by replacing the highly basic benzamidine P1 with a less basic benzylamine moiety. Further optimization of the pyrazole core substitution and the biphenyl P4 culminated in the discovery of DPC423 (17h), a highly potent, selective, and orally active factor Xa inhibitor which was chosen for clinical development.

Pharmacological Interruption of Acute Thrombus Formation with Minimal Hemorrhagic Complications by a Small Molecule Tissue Factor/Factor VIIa Inhibitor: Comparison to Factor Xa and Thrombin Inhibition in a Nonhuman Primate Thrombosis Model

“…The small molecule factor Xa inhibitor (Pinto et al, 2001) was synthesized in the Pfizer laboratories. Pinto et al (2001) reported K i values for this compound of 0.013 nM against factor Xa, 300 nM against thrombin, and 16 nM against trypsin. The inhibitor was dissolved in a combination of 10% ethanol, 10% PEG-400, and 80% saline to a final concentration of 3 mg/ml.…”

“…Experimental reagent PHA-927F (TF/FVIIa inhibitor) is a new chemical entity that was synthesized in the laboratories of Pfizer Corp. (St. Louis, MO). The small molecule thrombin inhibitor and the small molecule factor Xa inhibitor were prepared in the laboratories of Pfizer Corp. (St. Louis, MO) based on previously published information (Sanderson et al, 1998;Pinto et al, 2001).…”

“…Throm-bin is also a potent platelet agonist, inducing platelet aggregation and possessing smooth muscle cell proliferative properties as well (Coughlin, 2000). Pharmacological attempts have been made at various points of potential intervention in the coagulation cascade, ranging from nonspecific inhibitors such as warfarin, unfractionated heparin, and low-molecular weight heparins, to specific inhibitors of factor Xa or direct acting thrombin inhibitors (Hara et al, 1995;Sanderson et al, 1998;Hauptmann and Sturzebecher, 1999;Pinto et al, 2001). Previous reports suggest that inhibitors of the TF/VIIa complex may prevent thrombosis with a lower bleeding risk than other types of coagulation inhibitors (Harker et al, 1996;Himber et al, 1997;Zoldhelyi et al, 2000).…”

“…The intent of the present study is to compare, in a nonhuman primate model of acute thrombus formation, the antithrombotic efficacy and propensity for bleeding diatheses of a small-molecule inhibitor of TF/VIIa (PHA-927F) to a selective, small-molecule inhibitor of factor Xa (Pinto et al, 2001) or a selective, small-molecule, direct-acting inhibitor of thrombin (Sanderson et al, 1998).…”

Reductive Isoxazole Ring Opening of the Anticoagulant Razaxaban Is the Major Metabolic Clearance Pathway in Rats and Dogs

“…Extensive preclinical and clinical studies show that inhibition of factor Xa is effective in both venous and arterial thrombosis (Pinto et al, 2001;Lam et al, 2003;Walenga et al, 2003). In animal models a better therapeutic index (antithrombotic efficacy versus antihemostatic effects) has been shown for direct factor Xa inhibitors compared with direct thrombin inhibitors (Leadley, 2001;Wong et al, 2002aWong et al, ,b, 2007.…”