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Qiu X, Wang W, Zhao Z, Sun S, Tang L. Pre-clinical pharmacodynamic study of a novel oral factor Xa inhibitor zifaxaban. Eur J Pharmacol 2018; 836:50-56. [PMID: 30125563 DOI: 10.1016/j.ejphar.2018.08.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 08/13/2018] [Accepted: 08/15/2018] [Indexed: 10/28/2022]
Abstract
Zifaxaban is an orally active, direct Factor Xa (FXa) inhibitor that is in development for the prevention and treatment of arterial and venous thrombosis. This study was conducted to investigate the biochemical and pharmacological activity of zifaxaban. In vitro activity was evaluated by enzyme, platelet aggregation, and clotting assays. In vivo effects were examined in venous thrombosis, arteriovenous-shunt thrombosis, carotid thrombosis, and bleeding models in rats. Zifaxaban competitively inhibits human FXa (IC50 = 11.1 nM) with > 10,000-fold greater selectivity than other serine proteases. It did not impair platelet aggregation induced by collagen, adenosine diphosphate (ADP) or arachidonic acid. It significantly prolonged clotting time, prothrombin time (PT), and activated partial thromboplastin time (APTT) in the plasma of humans, rabbits, and rats, with a relatively weak effect on thrombin time (TT). In venous thrombosis models in rats, zifaxaban strongly suppressed thrombus formation with ED50 values of 3.09 mg/kg, and its best efficacy time occurred at 2 h after administration. In arteriovenous-shunt thrombosis and carotid thrombosis models in rats, it inhibited thrombus formation in a dose-dependent manner. And in the rat tail bleeding assay, it showed a trend of less bleeding than rivaroxaban at doses that achieved the same antithrombotic effect. In conclusion, zifaxaban is a selective and direct FXa inhibitor and a promising oral anticoagulant for the prophylaxis and treatment of thromboembolic diseases.
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Affiliation(s)
- Xiaomiao Qiu
- Tianjin Medical University, Tianjin 300070, China
| | - Weiting Wang
- Tianjin Institute of Pharmaceutical Research New Drug Evaluation Co. Ltd, Tianjin 300193, China
| | - Zhuanyou Zhao
- Tianjin Institute of Pharmaceutical Research New Drug Evaluation Co. Ltd, Tianjin 300193, China
| | - Shuangyong Sun
- Tianjin Institute of Pharmaceutical Research New Drug Evaluation Co. Ltd, Tianjin 300193, China.
| | - Lida Tang
- Tianjin Institute of Pharmaceutical Research New Drug Evaluation Co. Ltd, Tianjin 300193, China.
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Characterization of a novel selective factor Xa inhibitor, DJT06001, which reduces thrombus formation with low risk of bleeding. Eur J Pharmacol 2018; 825:85-91. [PMID: 29475063 DOI: 10.1016/j.ejphar.2018.02.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 02/17/2018] [Accepted: 02/19/2018] [Indexed: 11/21/2022]
Abstract
Factor Xa (FXa) is a serine protease that plays key roles in linking the intrinsic and extrinsic coagulation pathways to the final common pathway. DJT06001 is an oral, highly specific and direct FXa inhibitor for the prevention and treatment of thromboembolic diseases. We characterized the compound in vitro and studied its in vivo activity in rat thrombosis models, as well as bleeding risk and Pharmacokinetics and Pharmacodynamics (PK/PD) relationship. DJT06001 inhibited free FXa with an inhibitory constant (Ki) of 0.99 nM, and exhibited >10000-fold selectivity for FXa than for other related serine proteases. DJT06001 concentration-dependently inhibited FXa activity in the prothrombinase complex with an IC50 of 2.53 nM. The concentrations for DJT06001 to double the prothrombin time (PT) and activated partial thromboplastin time (APTT) were 0.74 and 0.57 μM, respectively. Importantly, DJT06001 did not impair platelet aggregation induced by ADP, platelet activating factor (PAF) and collagen. Furthermore, DJT06001 inhibited thrombus formation in rat thrombosis models in a dose dependent manner. And in rat tail bleeding risk test, it caused less bleeding than rivaroxaban at doses that achieve the same antithrombotic effect. PK/PD studies further demonstrated that there was a good correlation between the plasma concentrations of DJT06001and its inhibition of plasma FXa activity and prolongation of PT. In conclusion, DJT06001 was shown to be a potent and specific FXa inhibitor with excellent PK/PD profiles and it could be developed as a new anticoagulant for the management of thromboembolic diseases.
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Deguchi H, Elias DJ, Griffin JH. Minor Plasma Lipids Modulate Clotting Factor Activities and May Affect Thrombosis Risk. Res Pract Thromb Haemost 2017; 1:93-102. [PMID: 29082360 PMCID: PMC5658053 DOI: 10.1002/rth2.12017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Essentials Circulating blood contains hundreds of lipids, many of which might influence blood coagulation. Recent discoveries about circulating lipids that can affect blood coagulation are reviewed. Minor abundance plasma lipids can modulate thrombin generation via direct effects on factor Xa. Variations in minor abundance plasma lipids can influence thrombin generation and thrombosis risk.
Abstract Different minor abundance plasma lipids significantly influence thrombin generation in vitro and significant differences in such lipids are linked to risk for venous thrombosis. Some plasma sphingolipids including glucosylceramide, lyso‐sulfatide and sphingosine have anticoagulant properties whereas, conversely, some plasma phospholipid derivatives, including certain lyso‐phospholipids and ethanolamides, have procoagulant properties. Plasma metabolite profiling of venous thrombosis patients showed association of venous thrombosis with decreased plasma long‐chain acylcarntines, leading to discovery of their anticoagulant activity as inhibitors of factor Xa. Inhibition of factor Xa by acylcarnitines does not require the protein's Gla‐domain, emphasizing an expanded framework for the paradigm for lipid‐clotting factor interactions. Overall, whether by genetics or environment, alterations in the dynamics of lipid metabolism linked to an altered lipidome may contribute to regulation of blood coagulation because imbalances between physiologic procoagulant and anticoagulant lipids may contribute to excessive thrombin generation that augments risk for thrombosis.
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Affiliation(s)
- Hiroshi Deguchi
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA
| | - Darlene J Elias
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA.,Scripps Clinic and Scripps Green Hospital, La Jolla, CA, USA
| | - John H Griffin
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA.,Department of Medicine, University of California San Diego, La Jolla, CA, USA
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Acylcarnitines are anticoagulants that inhibit factor Xa and are reduced in venous thrombosis, based on metabolomics data. Blood 2015; 126:1595-600. [PMID: 26175037 DOI: 10.1182/blood-2015-03-636761] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/02/2015] [Indexed: 12/11/2022] Open
Abstract
In many patients with deep vein thrombosis and pulmonary embolism (venous thromboembolism, VTE), biomarkers or genetic risk factors have not been identified. To discover novel plasma metabolites associated with VTE risk, we employed liquid chromatography-mass spectrometry-based untargeted metabolomics, which do not target any specific metabolites. Using the Scripps Venous Thrombosis Registry population for a case-control study, we discovered that 10:1 and 16:1 acylcarnitines were low in plasmas of the VTE patient group compared with matched controls, respectively. Data from targeted metabolomics studies showed that several long-chain acylcarnitines (10:1, 12:0, 12:2, 18:1, and 18:2) were lower in the VTE group. Clotting assays were used to evaluate a causal relationship for low acylcarnitines in patients with VTE. Various acylcarnitines inhibited factor Xa-initiated clotting. Inhibition of factor Xa by acylcarnitines was greater for longer acyl chains. Mechanistic studies showed that 16:0 acylcarnitine had anticoagulant activity in the absence of factor Va or phospholipids. Surface plasmon resonance investigations revealed that 16:0 acylcarnitine was bound to factor Xa and that binding did not require the γ-carboxy glutamic acid domain. In summary, our study identified low plasma levels of acylcarnitines in patients with VTE and showed that acylcarnitines have anticoagulant activity related to an ability to bind and inhibit factor Xa.
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Factor Xa dimerization competes with prothrombinase complex formation on platelet-like membrane surfaces. Biochem J 2015; 467:37-46. [PMID: 25572019 DOI: 10.1042/bj20141177] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Exposure of phosphatidylserine (PS) molecules on activated platelet membrane surface is a crucial event in blood coagulation. Binding of PS to specific sites on factor Xa (fXa) and factor Va (fVa) promotes their assembly into a complex that enhances proteolysis of prothrombin by approximately 10⁵. Recent studies demonstrate that both soluble PS and PS-containing model membranes promote formation of inactive fXa dimers at 5 mM Ca²⁺. In the present study, we show how competition between fXa dimerization and prothrombinase formation depends on Ca²⁺ and lipid membrane concentrations. We used homo-FRET measurements between fluorescein-E-G-R-chloromethylketone (CK)-Xa [fXa irreversibly inactivated by alkylation of the active site histidine residue with FEGR (FEGR-fXa)] and prothrombinase activity measurements to reveal the balance between fXa dimer formation and fXa-fVa complex formation. Changes in FEGR-fXa dimer homo-FRET with addition of fVa to model-membrane-bound FEGR-fXa unambiguously demonstrated that formation of the FEGR-fXa-fVa complex dissociated the dimer. Quantitative global analysis according to a model for protein interaction equilibria on a surface provided an estimate of a surface constant for fXa dimer dissociation (K(fXa×fXa)(d, σ)) approximately 10-fold lower than K(fXa×fVa)(d,σ) for fXa-fVa complex. Experiments performed using activated platelet-derived microparticles (MPs) showed that competition between fXa dimerization and fXa-fVa complex formation was even more prominent on MPs. In summary, at Ca²⁺ concentrations found in the maturing platelet plug (2-5 mM), fVa can compete fXa off of inactive fXa dimers to significantly amplify thrombin production, both because it releases dimer inhibition and because of its well-known cofactor activity. This suggests a hitherto unanticipated mechanism by which PS-exposing platelet membranes can regulate amplification and propagation of blood coagulation.
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Majumder R, Koklic T, Sengupta T, Cole D, Chattopadhyay R, Biswas S, Monroe D, Lentz BR. Soluble phosphatidylserine binds to two sites on human factor IXa in a Ca2+ dependent fashion to specifically regulate structure and activity. PLoS One 2014; 9:e100006. [PMID: 24979705 PMCID: PMC4076177 DOI: 10.1371/journal.pone.0100006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 05/20/2014] [Indexed: 11/23/2022] Open
Abstract
Clinical studies have demonstrated a correlation between elevated levels of FIX and the risk of coronary heart disease, while reduced plasma FIX causes hemophilia B. FIXa interacts with FVIIIa in the presence of Ca2+ and phosphatidylserine (PS)-containing membranes to form a factor X-activating complex (Xase) that is key to propagation of the initiated blood coagulation process in human. We test the hypothesis that PS in these membranes up-regulates the catalytic activity of this essential enzyme. We used a soluble form of phosphatidylserine, 1, 2-dicaproyl-sn-glycero-3-phospho-L-serine (C6PS), as a tool to do so. C6PS and PS in membranes are reported to regulate the homologous FXa nearly identically. FIXa binds a molecule of C6PS at each of with two sites with such different affinities (∼100-fold) that these appear to be independent. A high affinity C6PS binding site (Kd∼1.4 µM) regulates structure, whereas a low-affinity binding site (Kd∼140 µM) regulates activity. Equilibrium dialysis experiments were analyzed globally with four other data sets (proteolytic and amidolytic activities, intrinsic fluorescence, ellipticity) to unequivocally demonstrate stoichiometries of one for both sites. Michaelis-Menten parameters for FIXa proteolytic activity were the same in the presence of C6PS or PS/PC membranes. We conclude that the PS molecule and not a membrane surface is the key regulator of both factors Xa and IXa. Despite some minor differences in the details of regulation of factors Xa and IXa, the similarities we found suggest that lipid regulation of these two proteases may be similar, a hypothesis that we continue to test.
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Affiliation(s)
- Rinku Majumder
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail:
| | - Tilen Koklic
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Tanusree Sengupta
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Daud Cole
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Rima Chattopadhyay
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Subir Biswas
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Dougald Monroe
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Barry R. Lentz
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
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Abstract
Human coagulation FXa (Factor Xa) plays a key role in blood coagulation by activating prothrombin to thrombin on 'stimulated' platelet membranes in the presence of its cofactor FVa (Factor Va). PS (phosphatidylserine) exposure on activated platelet membranes promotes prothrombin activation by FXa by allosterically regulating FXa. To identify the structural basis of this allosteric regulation, we used FRET to monitor changes in FXa length in response to (i) soluble short-chain PS [C6PS (dicaproylphosphatidylserine)], (ii) PS membranes, and (iii) FVa in the presence of C6PS and membranes. We incorporated a FRET pair with donor (fluorescein) at the active site and acceptor (Alexa Fluor® 555) at the FXa N-terminus near the membrane. The results demonstrated that FXa structure changes upon binding of C6PS to two sites: a regulatory site at the N-terminus [identified previously as involving the Gla (γ-carboxyglutamic acid) and EGFN (N-terminus of epidermal growth factor) domains] and a presumptive protein-recognition site in the catalytic domain. Binding of C6PS to the regulatory site increased the interprobe distance by ~3 Å (1 Å=0.1 nm), whereas saturation of both sites increased the distance by a further ~6.4 Å. FXa binding to a membrane produced a smaller increase in length (~1.4 Å), indicating that FXa has a somewhat different structure on a membrane from when bound to C6PS in solution. However, when both FVa2 (a FVa glycoform) and either C6PS- or PS-containing membranes were bound to FXa, the overall change in length was comparable (~5.6-5.8 Å), indicating that C6PS- and PS-containing membranes in conjunction with FVa2 have comparable regulatory effects on FXa. We conclude that the similar functional regulation of FXa by C6PS or membranes in conjunction with FVa2 correlates with similar structural regulation. The results demonstrate the usefulness of FRET in analysing structure-function relationships in FXa and in the FXa·FVa2 complex.
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