The discovery of glycine and related amino acid-based factor Xa inhibitors

Potent direct inhibitors of factor Xa based on the tetrahydroisoquinoline scaffold

Direct inhibition of coagulation factor Xa (FXa) carries significant promise for developing effective and safe anticoagulants. Although a large number of FXa inhibitors have been studied, each can be classified as either possessing a highly flexible or a rigid core scaffold. We reasoned that an intermediate level of flexibility will provide high selectivity for FXa considering that its active site is less constrained in comparison to thrombin and more constrained as compared to trypsin. We studied several core scaffolds including 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid for direct FXa inhibition. Using a genetic algorithm-based docking and scoring approach, a promising candidate 23 was identified, synthesized, and found to inhibit FXa with a K(i) of 28 μM. Optimization of derivative 23 resulted in the design of a potent dicarboxamide 47, which displayed a K(i) of 135 nM. Dicarboxamide 47 displayed at least 1852-fold selectivity for FXa inhibition over other coagulation enzymes and doubled PT and aPTT of human plasma at 17.1 μM and 20.2 μM, respectively, which are comparable to those of clinically relevant agents. Dicarboxamide 47 is expected to serve as an excellent lead for further anticoagulant discovery.

The discovery of (2R,4R)-N-(4-chlorophenyl)-N- (2-fluoro-4-(2-oxopyridin-1(2H)-yl)phenyl)-4-methoxypyrrolidine-1,2-dicarboxamide (PD 0348292), an orally efficacious factor Xa inhibitor

Herein, we report the discovery of novel, proline-based factor Xa inhibitors containing a neutral P1 chlorophenyl pharmacophore. Through the additional incorporation of 1-(4-amino-3-fluoro-phenyl)-1H-pyridin-2-one 22, as a P4 pharmacophore, we discovered compound 7 (PD 0348292). This compound is a selective, orally bioavailable, efficacious FXa inhibitor that is currently in phase II clinical trials for the treatment and prevention of thrombotic disorders.

Structure-based Drug Design of Pyrrolidine-1, 2-dicarboxamides as a Novel Series of Orally Bioavailable Factor Xa Inhibitors

A novel series of pyrrolidine-1,2-dicarboxamides was discovered as factor Xa inhibitors using structure-based drug design. This series consisted of a neutral 4-chlorophenylurea P1, a biphenylsulfonamide P4 and a D-proline scaffold (1, IC(50) = 18 nM). Optimization of the initial hit resulted in an orally bioavailable, subnanomolar inhibitor of factor Xa (13, IC(50) = 0.38 nM), which was shown to be efficacious in a canine electrolytic model of thrombosis with minimal bleeding.

Substituted thiophene-anthranilamides as potent inhibitors of human factor Xa

A series of thiophene-containing non-amidine factor Xa inhibitors is described. Simple methyl-substituted thiophene analogs were relatively weak inhibitors. However, introduction of hydrophilic substituents at C-4 or C-5 of the thiophene afforded inhibitors with low nanomolar potency. Optimization of the thiophene substituent at C-4 afforded subnanomolar inhibitors with improved in vitro anticoagulant activity. Incorporating basic amine substituents on the thiophene increased hydrophilicity and improved anticoagulant activity. The pharmacokinetic profile of one inhibitor was evaluated in dogs, and the X-ray crystal structure of this compound bound to factor Xa provides insight into the observed SAR for binding to factor Xa.

Enzyme inhibition potency enhancement by active site metal chelating and hydrogen bonding induced conformation-restricted cyclopropanecarbonyl derivatives

Two cyclopropanecarbonyl derivatives were independently found to be 15 and 14 times more potent than the corresponding isopropylcarbonyl analogues as inhibitors of 4-hydroxyphenylpyruvate dioxygenase and dihydroorotate dehydrogenase, respectively. A thorough examination of the co-crystal structures of available enzyme inhibitor complexes and the conformation of X-ray crystal structures of several synthesized cyclopropanecarbonyl derivatives revealed that this enhancement by one order of magnitude of inhibition potency exhibited by cyclopropanecarbonyl derivatives in both enzymes is probably caused by respective metal chelating and hydrogen bonding interactions at the ligand-receptor binding site. These specific interactions subsequently cause the cyclopropyl group of the molecules to adopt a fixed bisected conformation, which is unavailable for isopropylcarbonyl derivatives.