thrombin inhibitor
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Author(s):  
Jorge Ripoll-Rozada ◽  
Joshua W. C. Maxwell ◽  
Richard J. Payne ◽  
Pedro José Barbosa Pereira

Tyrosine-O-sulfation is a common post-translational modification (PTM) of proteins following the cellular secretory pathway. First described in human fibrinogen, tyrosine-O-sulfation has long been associated with the modulation of protein–protein interactions in several physiological processes. A number of relevant interactions for hemostasis are largely dictated by this PTM, many of which involving the serine proteinase thrombin (FIIa), a central player in the blood-clotting cascade. Tyrosine sulfation is not limited to endogenous FIIa ligands and has also been found in hirudin, a well-known and potent thrombin inhibitor from the medicinal leech, Hirudo medicinalis. The discovery of hirudin led to successful clinical application of analogs of leech-inspired molecules, but also unveiled several other natural thrombin-directed anticoagulant molecules, many of which undergo tyrosine-O-sulfation. The presence of this PTM has been shown to enhance the anticoagulant properties of these peptides from a range of blood-feeding organisms, including ticks, mosquitos and flies. Interestingly, some of these molecules display mechanisms of action that mimic those of thrombin's bona fide substrates.


2021 ◽  
Vol 23 (12) ◽  
Author(s):  
Teresa Siller ◽  
Arvind Chandratheva ◽  
Philipp Bücke ◽  
David J. Werring ◽  
David Seiffge

Abstract Purpose of Review Direct oral anticoagulants (DOACs: the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban and the direct thrombin inhibitor dabigatran) are the mainstay of stroke prevention in patients with non-valvular atrial fibrillation (AF). Nevertheless, there is a residual stroke risk of 1–2% per year despite DOAC therapy. Intravenous thrombolysis (IVT) reduces morbidity in patients with ischemic stroke and improves functional outcome. Prior DOAC therapy is a (relative) contraindication for IVT but emerging evidence supports its use in selected patients. Recent Findings Recent observational studies highlighted that IVT in patients on prior DOAC therapy seems feasible and did not yield major safety issues. Different selection criteria and approaches have been studied including selection by DOAC plasma levels, non-specific coagulation assays, time since last intake, and prior reversal agent use. The optimal selection process is however not clear and most studies comprised few patients. Summary IVT in patients taking DOAC is a clinically challenging scenario. Several approaches have been proposed without major safety issues but current evidence is weak. A patient-oriented approach balancing potential benefits of IVT (i.e., amount of salvageable penumbra) against expected bleeding risk including appropriate monitoring of anticoagulant activity seem justified.


Author(s):  
Lea Brückner ◽  
Jan Beyer-Westendorf ◽  
Oliver Tiebel ◽  
Jörg Pietsch

AbstractSince direct oral anticoagulants (DOAC) are administered frequently to an elderly, co-morbid population, medical emergencies including trauma, acute bleeding or organ failure are not uncommon. In these situations, the type, dosage or the time of last intake of anticoagulants is often unknown and single substance analysis by functional tests is only possible if the substance contained in the sample is known. A reliable and validated toxicology screen of DOAC and argatroban would be helpful inform not only attending physicians in the emergency department but also law enforcement and courts of justice. After precipitation with acetone, HPLC separation was achieved on a Phenomenex Luna Pentafluorophenyl Colum using acetonitrile–water (90:10, v/v) as mobile phase system. Detection was performed using a 3200 Q Trap mass spectrometer (AB Sciex). For analysis MRM Scans (MS/MS) with positive ionization were chosen. The method was validated for blank serum as the matrix of choice. Limits of detection are between 0.5 and 1.0 ng/mL, limits of quantification are between 1.9 and 3.6 ng/mL and recoveries are above 60%. The applicability of the method was demonstrated by the determination of DOAC in body fluids from forensic cases and in therapeutic drug monitoring. The rapid simultaneous detection and quantification of apixaban, argatroban, dabigatran etexilate, dabigatran, edoxaban and rivaroxaban in body fluids by HPLC–MS/MS closes an important gap in emergency toxicology.


TH Open ◽  
2021 ◽  
Author(s):  
Ramin Artang ◽  
Joao Dias ◽  
Mark Walsh ◽  
Kevin P Bliden ◽  
Jørn Dalsgaard Nielsen ◽  
...  

Background: Direct-acting oral anticoagulants (DOACs) do not require monitoring. Measurement of DOAC effect would be useful in the event of bleeding, trauma, and thromboembolism while on anticoagulation. We evaluated the effectiveness of the investigational DOAC assays on the TEG®6s Hemostasis Analyzer to assess the anticoagulant effect of DOACs in patients treated for atrial fibrillation or DVT. Methods: Patients on treatment for a minimum of 7 days with standard doses of dabigatran, rivaroxaban and apixaban were included. DOAC plasma concentrations and TEG®6s R-time were measured and correlated. The sensitivity, specificity and negative predictive value (NPV) of R-time to detect DOAC concentrations of ≥ 30, ≥ 50 and ≥ 100 ng/mL were calculated. Results: 189 Subjects were included, (n=50) on apixaban, (n= 62) on rivaroxaban, (n=53) on dabigatran and (n=24) on no DOAC were studied. Using the direct thrombin inhibitor (DTI) channel, R-time demonstrated strong linear correlation with dabigatran levels (r = 0.93, p < 0.0001). Using the anti-factor Xa (AFXa) channel, R-time demonstrated strong non-linear correlation with rivaroxaban and apixaban levels (rs = 0.92 and 0.84 respectively, p < 0.0001 for both). R-time revealed strong sensitivity and NPV in detecting low DOAC levels for the predefined concentrations. Conclusion: R-time measured by TEG®6s DOAC Specific cartridge has a strong correlation with concentrations of the most commonly used DOACs, with high sensitivity and NPV for detecting lower drug levels that are considered clinically relevant for patients in need of antidote, or prior to urgent surgery. Further studies to determine the relation of R-time to clinical outcomes are warranted.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2065-2065
Author(s):  
Tanja Knopp ◽  
Jeremy Lagrange ◽  
Rebecca Jung ◽  
Johannes Wild ◽  
Heidi Rossmann ◽  
...  

Abstract Introduction: Pro-inflammatory cytokines play an essential role as activators of the hemostatic system and in the regulation of physiological antithrombotic mechanisms. Interleukin-6 (IL-6) influences platelet production and platelet activation. It was associated with accelerated clotting and intravascular coagulation in tissue factor (TF)-driven murine thrombosis models. However, the precise role of myeloid cell-derived IL-6 on thrombosis formation and the hemostatic system is still unknown. Methods and Results: To better understand the role of IL-6 in thrombosis and the hemostatic system, we developed a new mouse strain with Cre-recombinase driven constitutive IL-6 expression specifically in myeloid cells (LysM-IL-6 OE, Control mice: IL-6 OE). LysM-IL-6 OE mice had a prolonged tail bleeding time and lacked venous thrombus formation induced by inferior vena cava (IVC) stenosis. There were no differences in D-Dimer levels in LysM-IL-6 OE mice neither on baseline level nor after IVC ligation. However, we found unstoppable post-operative bleedings in LysM-IL-6 OE. They showed a prolonged aPTT, a significantly increased INR and a prolonged thrombin converting time. The Factor V and IX expression were reduced, but von Willebrand factor, antithrombin and fibrinogen expression were up-regulated and could not explain the missing thrombus formation. We found significantly elevated erythrocyte sedimentation in line with erythrocytes aggregates, which seemed to be mediated by IL-6 and α2M. Most importantly, hepatic levels of thrombin inhibitor α2 macroglobulin (α2M) mRNA and protein were increased in LysM-IL-6 OE/+ mice compared to control mice. In parallel, Platelet erythrocyte interaction seemed to be essential in the development of the bleeding phenotype. Conclusions: These findings show the role of chronically elevated IL-6 in driving the accumulation of A2m on the surface of erythrocytes, thereby mediating a phenotype of increased bleeding complications. This work was supported by the DFG KA4035/1-1 and by the German Ministry for Education and Research (BMBF 01EO1503) Disclosures Lämmle: Takeda: Membership on an entity's Board of Directors or advisory committees; Ablynx: Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Baxter: Other: Travel Support, Speakers Bureau; Alexion: Other: Travel Support, Speakers Bureau; Siemens: Other: Travel Support, Speakers Bureau; Bayer: Other: Travel Support, Speakers Bureau; Roche: Other: Travel Support, Speakers Bureau; Sanofi: Other: Travel Support, Speakers Bureau. Ruf: ARCA bioscience: Consultancy, Patents & Royalties; ICONIC Therapeutics: Consultancy; MeruVasimmune: Current holder of individual stocks in a privately-held company.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4270-4270
Author(s):  
Afshin Ameri ◽  
Courtney M Anderson ◽  
Joetta H Smith ◽  
Julisa Patel

Abstract Direct oral anticoagulants (DOAC) such as the thrombin inhibitor Dabigatran and the coagulation factor Xa inhibitors Apixaban and Rivaroxaban have been in clinical use for the past 5-6 years. Familiarity with their use in the general pediatric population with thrombosis secondary to inflammatory disorders and rheumatologic disease is currently not as prevalent due to the widespread more conventional anticoagulation practice with the fractionated heparins in particular Lovenox. In this report we would like to summarize our experience in a pediatric patient population ranging from 3- 17 years with thrombotic disease. Of 55 patients with various thrombotic events 16 patients were treated with DOAC. There were 5 patients who had underlying inflammatory disease including COVID. Thrombotic complications included arterial as well as venous thrombotic events. All patients had elevated D-Dimer levels ranging from 360-4000 mcg/ml on diagnosis and normalized with successful anticoagulation. All patients had resolution of thrombosis. Thrombelastogram (TEG) were obtained on isolated patients during therapy and were useful to balance anticoagulation to prevent hemorrhagic complications. In conclusion, DOAC are a safe and effective alternative to LMW Heparin in pediatric patients with arterial or venous thrombosis. Monitoring should include determination of D-Dimer levels for efficacy of treatment and TEG in cases with arterial disease where bleeding may be a secondary complication of therapy. Disclosures No relevant conflicts of interest to declare.


eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Yanyan Ding ◽  
Yuzhe Li ◽  
Zhiqian Zhao ◽  
Qiangfeng Cliff Zhang ◽  
Feng Liu

Although thrombosis has been extensively studied using various animal models, our understanding of the underlying mechanism remains elusive. Here, using zebrafish model, we demonstrated that smarca5-deficient red blood cells (RBCs) formed blood clots in the caudal vein plexus. We further used the anti-thrombosis drugs to treat smarca5zko1049a embryos and found that a thrombin inhibitor, argatroban, partially prevented blood clot formation in smarca5zko1049a. To explore the regulatory mechanism of smarca5 in RBC homeostasis, we profiled the chromatin accessibility landscape and transcriptome features in RBCs from smarca5zko1049a and their siblings and found that both the chromatin accessibility at the keap1a promoter and expression of keap1a were decreased. Keap1 is a suppressor protein of Nrf2, which is a major regulator of oxidative responses. We further identified that the expression of hmox1a, a downstream target of Keap1-Nrf2 signaling pathway, was markedly increased upon smarca5 deletion. Importantly, overexpression of keap1a or knockdown of hmox1a partially rescued the blood clot formation, suggesting that the disrupted Keap1-Nrf2 signaling is responsible for the RBC aggregation in smarca5 mutants. Together, our study using zebrafish smarca5 mutants characterizes a novel role for smarca5 in RBC aggregation, which may provide a new venous thrombosis animal model to support drug screening and pre-clinical therapeutic assessments to treat thrombosis.


2021 ◽  
Vol 14 (10) ◽  
pp. e245245
Author(s):  
Arun Prabhahar Rajarajen ◽  
Raihan Ashraf ◽  
Nishtha Ahuja ◽  
Joyita Bharati

Dabigatran, a novel oral anticoagulant, is a direct thrombin inhibitor and is being increasingly used owing to the advantage of dosing without the need for laboratory monitoring. While extensive skin necrosis is known to be associated with oral anticoagulants such as warfarin and factor Xa inhibitors, dabigatran toxicity typically manifests with bleeding, especially in the elderly. We describe a 70-year-old woman who was prescribed dabigatran for the treatment of unprovoked deep venous thrombosis. She developed bleeding diathesis along with extensive skin necrosis and acute kidney injury shortly after commencing the drug. Haemodialysis was given in view of dabigatran toxicity and complications of kidney dysfunction which resolved promptly over a week. However, the patient succumbed to severe sepsis from secondary skin infections. It is crucial to closely monitor for signs of dabigatran toxicity, especially in the elderly patients.


2021 ◽  
pp. 101322
Author(s):  
Stephen Lu ◽  
Lucas Tirloni ◽  
Markus Berger Oliveira ◽  
Christopher F. Bosio ◽  
Glenn A. Nardone ◽  
...  

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