Halothiophene benzimidazoles as P1 surrogates of inhibitors of blood coagulation factor Xa

Neutral weak halothiophene benzimidazole inhibitors of the serine protease factor Xa were identified via screening of a compound library. The X-ray crystal structure of representative 3a bound to human fXa confirmed the S1 binding mode. Starting from 3a a series of halothiophene benzimidazoles was synthesized and investigated for their factor Xa inhibitory activity. This led to potent and selective achiral inhibitors against fXa such as compounds 9k and 9w.     

Novel factor Xa inhibitors based on a benzoic acid scaffold and incorporating a neutral P1 ligand

A series of novel, highly potent, achiral factor Xa inhibitors based on a benzoic acid scaffold and containing a chlorophenethyl moiety directed towards the protease S1 pocket is described. A number of structural features, such as the requirements of the P1, P4 and ester-binding pocket ligands were explored with respect to inhibition of factor Xa. Compound 46 was found to be the most potent compound in a series of antithrombotic secondary assays.     

Amido-(propyl and allyl)-hydroxybenzamidines: development of achiral inhibitors of factor Xa

The design, synthesis and SAR of amido-(propyl and allyl)-hydroxybenzamidine coagulation factor Xa inhibitors is described. These achiral inhibitors are selective for fXa vis a vis structurally related serine proteases and are readily prepared in 6-7 linear steps. The most potent member 9j (fXa Ki = 0.75 nM) is selective (>1000-fold) and an effective anticoagulant in mammalian plasma.     

Aminobenzisoxazoles with biaryl P4 moieties as potent, selective, and orally bioavailable factor Xa inhibitors

We have previously reported on a series of aminobenzisoxazoles as potent, selective, and orally bioavailable factor Xa inhibitors, which culminated in the discovery of razaxaban. Herein, we describe another approach to improve factor Xa inhibitory potency and pharmacokinetic profile by incorporating basic and water soluble functionalities on the terminal ring of the P4 biaryl group found in our earlier Xa inhibitors. This approach resulted in a series of potent, selective, and orally bioavailable factor Xa inhibitors.     

From selective substrate analogue factor Xa inhibitors to dual inhibitors of thrombin and factor Xa. Part 3

Highly potent and selective substrate analogue factor Xa inhibitors were obtained by incorporation of non-basic or modestly basic P1 residues known from the development of thrombin inhibitors. The modification of the P2 and P3 amino acids strongly influenced the selectivity and provided potent dual factor Xa and thrombin inhibitors without affecting the fibrinolytic enzymes. Several inhibitors demonstrated excellent anticoagulant efficacy in standard clotting assays in human plasma.     

Design,synthesis, and structure-activity relationships of unsubstituted piperazinone-based transition state factor Xa inhibitors

A series of novel transition state factor Xa inhibitors containing a variety of lactam ring systems as central templates was synthesized in an expedient manner and allowed for a great deal of structural variability. Among them, the piperazinone-based inhibitors were found to be not only active against factor Xa but also selective over thrombin. Optimization of the P4 moiety yielded several potent compounds with IC(50) below 1 nM against factor Xa.     

Preparation of pyrrolidine and isoxazolidine benzamidines as potent inhibitors of coagulation factor Xa.

The serine protease factor Xa is a critical enzyme in the blood coagulation cascade. Recently, the inhibition of factor Xa has begun to emerge as an attractive strategy for the discovery of novel antithrombotic agents. Here we describe pyrrolidine and isoxazolidine benzamidines as novel and potent inhibitors of factor Xa.     

Novel factor Xa inhibitors based on a 2-carboxyindole scaffold: SAR of P4 substituents in combination with a neutral P1 ligand

A series of novel, highly potent 2-carboxyindole-based factor Xa inhibitors is described. Structural requirements for P4 ligands in combination with a neutral biaryl P1 ligand were investigated with the 2-carboxyindole scaffold. A diverse set of P4 substituents was identified, which, in conjunction with a biaryl P1 ligand, gave highly potent factor Xa inhibitors, which were also selective versus other proteases and efficacious in various antithrombotic secondary assays.     

Synthesis and SAR of benzamidine factor Xa inhibitors containing a vicinally-substituted heterocyclic core

The selective inhibition of coagulation factor Xa has emerged as an attractive strategy for the discovery of novel antithrombotic agents. Here we describe highly potent benzamidine factor Xa inhibitors based on a vicinally-substituted heterocyclic core.     

Factor Xa inhibitors based on a 2-carboxyindole scaffold: SAR of neutral P1 substituents

A series of novel, highly potent 2-carboxyindole-based factor Xa inhibitors is described. Structural requirements for neutral ligands, which bind in the S1 pocket of factor Xa were investigated with the 2-carboxyindole scaffold. This privileged fragment assembly approach yielded a set of equipotent, selective inhibitors with structurally diverse neutral P1 substituents.     

Design,synthesis and structure-activity relationships of benzoxazinone-based factor Xa inhibitors

A series of benzoxazinone derivatives was designed and synthesized as factor Xa inhibitors. We demonstrated that the naphthyl moiety in the aniline-based compounds 1 and 2 can be replaced with benzene-fused heterobicycles and biaryls to give factor Xa inhibitors with improved trypsin selectivity. The P4 modifications lead to monoamidines which are moderately active. The benzoxazinones 41-45 are potent against factor Xa, retain the improved trypsin selectivity of the corresponding aniline-based compounds, and show strong antithrombotic effect dose responsively.     

Structural basis for inhibition promiscuity of dual specific thrombin and factor Xa blood coagulation inhibitors

BACKGROUND: A major current focus of pharmaceutical research is the development of selective inhibitors of the blood coagulation enzymes thrombin or factor Xa to be used as orally bioavailable anticoagulant drugs in thromboembolic disorders and in the prevention of venous and arterial thrombosis. Simultaneous direct inhibition of thrombin and factor Xa by synthetic proteinase inhibitors as a novel approach to antithrombotic therapy could result in potent anticoagulants with improved pharmacological properties. RESULTS: The binding mode of such dual specific inhibitors of thrombin and factor Xa was determined for the first time by comparative crystallography using human alpha-thrombin, human des-Gla (1--44) factor Xa and bovine trypsin as the ligand receptors. The benzamidine-based inhibitors utilize two different conformations for the interaction with thrombin and factor Xa/trypsin, which are evoked by the steric requirements of the topologically different S2 subsites of the enzymes. Compared to the unliganded forms of the proteinases, ligand binding induces conformational adjustments of thrombin and factor Xa active site residues indicative of a pronounced induced fit mechanism. CONCLUSION: The structural data reveal the molecular basis for a desired unselective inhibition of the two key components of the blood coagulation cascade. The 4-(1-methyl-benzimidazole-2-yl)-methylamino-benzamidine moieties of the inhibitors are able to fill both the small solvent accessible as well as the larger hydrophobic S2 pockets of factor Xa and thrombin, respectively. Distal fragments of the inhibitors are identified which fit into both the cation hole/aromatic box of factor Xa and the hydrophobic aryl binding site of thrombin. Thus, binding constants in the medium-to-low nanomolar range are obtained against both enzymes.     

Design,synthesis and biological activity of novel non-amidine factor Xa inhibitors. Part 1: P(1) structure-activity relationships of the substituted 1-(2-Naphthyl)-1H-pyrazole-5-carboxylamides

Based on DuPont Pharmaceuticals' monobenzamidine lead structure SN429, we have designed the biphenyl 1-(2-naphthyl)-1H-pyrazole-5-carboxylamides as a novel series of non-basic factor Xa inhibitors. We have discovered that the displacement of the benzamidine moiety with substituted 2-naphthyl structures not only results in highly potent factor Xa inhibitors, but also significantly increases their enzyme specificity and oral bioavailability.     

Optimization of the beta-aminoester class of factor Xa inhibitors. Part 2: Identification of FXV673 as a potent and selective inhibitor with excellent In vivo anticoagulant activity

Further optimization of the beta-aminoester class of factor Xa (fXa) inhibitors is described culminating in the identification of 9c (FXV673), a potent and selective factor Xa inhibitor with excellent in vivo anticoagulant activity. An X-ray structure of FXV673 bound to human fXa is also presented. Based on its selectivity, potent in vivo activity and favorable pre-clinical safety profile, FXV673 was selected for further development and is currently undergoing clinical trials.     

The design of phenylglycine containing benzamidine carboxamides as potent and selective inhibitors of factor Xa

Factor Xa, a critical serine protease in the blood coagulation cascade, has become a target for inhibition as a strategy for the invention of novel anti-thrombotic agents. Here we describe the development of phenylglycine containing benzamidine carboxamides as novel, potent and selective inhibitors of factor Xa.     

Development of potent and selective factor Xa inhibitors.

The development of potent and selective small molecule inhibitors of factor Xa is described.     

Increase of anti-metastatic efficacy by selectivity- but not affinity-optimization of synthetic serine protease inhibitors

Although tumors frequently show elevated protease activities, the concept of anti-proteolytic cancer therapy has lost momentum after failure of clinical trials with broad-spectrum matrix metalloproteinase inhibitors. Thus we need to adapt our design strategies for protease inhibitors. Here, we employed a series of seven structurally fine-modulated and pharmacokinetically closely related synthetic 4-amidinobenzylamine-based inhibitors with distinct selectivity for prototypical serine proteases in a murine T cell lymphoma liver metastasis model. This in vivo screening revealed efficacy of urokinase inhibitors but no correlation between urokinase selectivity or affinity and anti-metastatic effect. In contrast, factor Xa-selective inhibitors were more potent, demonstrating factor Xa or a factor Xa-like serine protease likely to be more determinant in this model. Factor Xa selectivity, but not affinity, significantly improved anti-metastatic efficacy. For example, factor Xa inhibitors CJ-504 and CJ-510 exert similar affinity for factor Xa (K(i)=14 nM versus 8.8 nM) but CJ-504 was 70-fold more selective for factor Xa. This correlated with higher anti-metastatic efficacy (58.8% with CJ-504; 28.2% with CJ-510). Our results show that among the protease inhibitors employed that have affinities in the nanomolar range, the strategy of selectivity-optimization is superior to further improvement of affinity to significantly enhance anti-metastatic efficacy. This appreciation may be important for the future rational design of new anti-proteolytic agents for cancer therapy.     

Design, synthesis and structure-activity relationship of a series of arginine aldehyde factor Xa inhibitors. Part 1: structures based on the (D)-Arg-Gly-Arg tripeptide sequence

A series of arginine aldehyde inhibitors was designed as transition state (TS) analogues based on the known factor Xa specific substrate Cbz-D-Arg-Gly-Arg-pNA. BnSO2-(D)Arg-Gly-Arg-H (20) was found to be the most potent and selective inhibitor of factor Xa and prothrombinase activity in this series.