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  1. Article ; Online: Evaluation of the procoagulant state in chronic immune thrombocytopenia before and after eltrombopag treatment-a prospective cohort study.

    van Dijk, Wobke E M / Poolen, Geke C / Huisman, Albert / Koene, Harry R / Fijnheer, Rob / Thielen, Noortje / van Bladel, Esther R / van Galen, Karin P M / Schutgens, Roger E G / Urbanus, Rolf T

    Journal of thrombosis and haemostasis : JTH

    2022  Volume 21, Issue 4, Page(s) 1020–1031

    Abstract: Background: Thrombopoietin receptor agonists are frequently used in treating immune thrombocytopenia (ITP) owing to high response rates and good tolerability. ITP is associated with an increased risk of thrombosis. Whether treatment with eltrombopag ... ...

    Abstract Background: Thrombopoietin receptor agonists are frequently used in treating immune thrombocytopenia (ITP) owing to high response rates and good tolerability. ITP is associated with an increased risk of thrombosis. Whether treatment with eltrombopag further increases this risk is controversial. The mechanisms behind the thrombotic risk in ITP are unclear.
    Objectives: To assess platelet function and hypercoagulability in patients with ITP and the effect of eltrombopag thereon.
    Methods: This prospective multicenter study assessed adult primary patients with ITP who were starting eltrombopag treatment. Platelet (re)activity and hypercoagulability were measured in whole blood or plasma before start and after 2 to 3 weeks of eltrombopag treatment and compared with those of controls. Change over time was assessed by mixed-effects models, and the results were corrected for multiple testing.
    Results: We included 16 patients and 33 controls. At baseline, patients with ITP exhibited lower expression of glycoprotein VI, more activated platelets, and lower reactivity toward agonists compared with controls. β-Thromboglobulin levels reduced and thrombin generation peak height increased compared with those of controls. In line with this finding, patients with ITP showed high factor VIII (median, 217%; IQR, 174%-272%) and von Willebrand factor levels (median, 167%; IQR, 109%-198%). Eltrombopag treatment increased thrombin generation potential: lag time decreased and peak height and endogeneous thrombin potential increased. The latter changes were not significant after correction for multiple testing.
    Conclusion: Patients with ITP in this study were in a hypercoagulable state, with preactivated platelets, increased thrombin generation potential, and increased levels of factor VIII and von Willebrand factor. Eltrombopag treatment further increased plasma thrombin generation potential but no other hemostatic parameters.
    MeSH term(s) Adult ; Humans ; Purpura, Thrombocytopenic, Idiopathic/diagnosis ; Purpura, Thrombocytopenic, Idiopathic/drug therapy ; Purpura, Thrombocytopenic, Idiopathic/chemically induced ; Prospective Studies ; Factor VIII ; Thrombin ; von Willebrand Factor ; Thrombocytopenia ; Hydrazines/adverse effects ; Thrombophilia/chemically induced
    Chemical Substances eltrombopag (S56D65XJ9G) ; Factor VIII (9001-27-8) ; Thrombin (EC 3.4.21.5) ; von Willebrand Factor ; Hydrazines
    Language English
    Publishing date 2022-12-22
    Publishing country England
    Document type Multicenter Study ; Journal Article
    ZDB-ID 2112661-6
    ISSN 1538-7836 ; 1538-7933
    ISSN (online) 1538-7836
    ISSN 1538-7933
    DOI 10.1016/j.jtha.2022.11.039
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: VhH anti-thrombomodulin clone 1 inhibits TAFI activation and enhances fibrinolysis in human whole blood under flow.

    van Moorsel, Marc V A / Poolen, Geke C / Koekman, Cornelis A / Verhoef, Sandra / de Maat, Steven / Barendrecht, Arjan / van Kleef, Nadine D / Meijers, Joost C M / Schiffelers, Raymond M / Maas, Coen / Urbanus, Rolf T

    Journal of thrombosis and haemostasis : JTH

    2022  Volume 20, Issue 5, Page(s) 1213–1222

    Abstract: Background: Thrombomodulin on endothelial cells can form a complex with thrombin. This complex has both anticoagulant properties, by activating protein C, and clot-protective properties, by activating thrombin-activatable fibrinolysis inhibitor (TAFI). ... ...

    Abstract Background: Thrombomodulin on endothelial cells can form a complex with thrombin. This complex has both anticoagulant properties, by activating protein C, and clot-protective properties, by activating thrombin-activatable fibrinolysis inhibitor (TAFI). Activated TAFI (TAFIa) inhibits plasmin-mediated fibrinolysis.
    Objectives: TAFIa inhibition is considered a potential antithrombotic strategy. So far, this goal has been pursued by developing compounds that directly inhibit TAFIa. In contrast, we here describe variable domain of heavy-chain-only antibody (VhH) clone 1 that inhibits TAFI activation by targeting human thrombomodulin.
    Methods: Two llamas (Lama Glama) were immunized, and phage display was used to select VhH anti-thrombomodulin (TM) clone 1. Affinity was determined with surface plasmon resonance and binding to native TM was confirmed with flow cytometry. Clone 1 was functionally assessed by competition, clot lysis, and thrombin generation assays. Last, the effect of clone 1 on tPA-mediated fibrinolysis in human whole blood was investigated in a microfluidic fibrinolysis model.
    Results: VhH anti-TM clone 1 bound recombinant TM with a binding affinity of 1.7 ± 0.4 nM and showed binding to native TM. Clone 1 competed with thrombin for binding to TM and attenuated TAFI activation in clot lysis assays and protein C activation in thrombin generation experiments. In a microfluidic fibrinolysis model, inhibition of TM with clone 1 fully prevented TAFI activation.
    Discussion: We have developed VhH anti-TM clone 1, which inhibits TAFI activation and enhances tPA-mediated fibrinolysis under flow. Different from agents that directly target TAFIa, our strategy should preserve direct TAFI activation via thrombin.
    MeSH term(s) Carboxypeptidase B2/metabolism ; Clone Cells/metabolism ; Endothelial Cells/metabolism ; Fibrinolysis ; Humans ; Protein C/metabolism ; Thrombin/metabolism ; Thrombomodulin/chemistry
    Chemical Substances Protein C ; Thrombomodulin ; Carboxypeptidase B2 (EC 3.4.17.20) ; Thrombin (EC 3.4.21.5)
    Language English
    Publishing date 2022-03-11
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2112661-6
    ISSN 1538-7836 ; 1538-7933
    ISSN (online) 1538-7836
    ISSN 1538-7933
    DOI 10.1111/jth.15674
    Database MEDical Literature Analysis and Retrieval System OnLINE

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