Shaping the thrombotic cascade: From clinical risk prediction to targeted modulation of coagulation

Venous thromboembolism is a common thrombotic disorder presenting complex clinical
challenges, particularly regarding the optimal duration of anticoagulation therapy.
Extending anticoagulation reduces the risk of recurrence but increases bleeding risk.
Accurate prediction of recurrence risk could help guide decisions on whether to continue
or stop anticoagulation.

In Chapter 2, we investigated platelet and endothelial biomarkers and found that
elevated levels of von Willebrand Factor during anticoagulation were associated with early
recurrence, especially in men. These findings suggest VWF might be a useful biomarker for
personalized risk prediction, enabling more tailored anticoagulation strategies if validated
in further studies.

Chapter 3 employed unbiased mass spectrometry to discover new biomarkers but did
not find proteins that significantly differed between patients with and without recurrence,
either during or after anticoagulation.

Chapter 4 evaluated global coagulation assays focusing on thrombin generation and
thrombin dynamics. We found that reduced endogenous thrombin potential (ETP) and
reduced thrombin inhibition by antithrombin were linked to recurrence, particularly when
excluding hormone-related VTE cases. Additionally, impaired thrombomodulin-mediated
inhibition of thrombin generation was associated with recurrence risk.

Chapter 5 shifted focus to patients with immune thrombocytopenia (ITP) , a patient group
with heightened thrombotic risk. These patients showed elevated ETP, which increased
further following eltrombopag treatment, highlighting a prothrombotic state.
After establishing the importance of thrombin generation in predicting recurrence and
assessing thrombotic state, Part II of the thesis examined thrombomodulin’s ability to
modulate thrombin generation for diagnostic and therapeutic purposes, focusing on
strategies to enhance or inhibit its activity.

In Chapter 6, we developed liposomes conjugated with thrombomodulin (TM-liposomes)
that more effectively inhibited thrombin generation in plasma and whole blood compared
to soluble thrombomodulin. The lipid composition of these liposomes influenced their
efficacy, with higher phosphatidylserine content enhancing protein C activation. These
TM-liposomes may improve diagnostics by more closely mimicking the natural endothelial
membrane environment and enabling better assessment of the activated protein C
pathway in thrombin generation.

Chapter 7 describes the design of a nanobody (VhH) that inhibits thrombin-activatable
fibrinolysis inhibitor (TAFI) activation by thrombomodulin. We demonstrated that this VhH
enhanced fibrinolysis in whole blood under flow conditions, offering a new strategy to
enhance clot breakdown and possibly reduce thrombotic complications.