Tissue Factor/Factor XIa Dual-activated Thrombin Generation is Able to Reliably Measure Thrombin Generation at All Hemophilia A Disease Severities

Factor V is an anticoagulant of the extrinsic pathway of coagulation and modifier of thrombin generation in hemophilia A.

FV is an endogenous anticoagulant that inhibits TF-initiated coagulation by limiting FX activation by TF:FVIIa through a membrane-dependent mechanism, which refines models of coagulation initiation and may help explain how FV variation contributes to bleeding and thrombosis.

The Tissue Factor-TFPI Pathway as a Therapeutic Target in Bleeding Disorders of Unknown Cause.

BACKGROUND Bleeding disorders of unknown cause (BDUC) comprise a heterogeneous group of conditions characterized by clinically significant bleeding despite normal results on standard haemostatic investigations. OBJECTIVES To investigate tissue factor (TF)-dependent coagulation in patients with BDUC and to evaluate the in vitro ability of concizumab and recombinant activated factor VII (rFVIIa) to restore thrombin generation. METHODS AND RESULTS Thrombin generation was assessed using an assay designed to isolate TF-dependent coagulation by inhibiting contact pathway activation with corn trypsin inhibitor (CTI). A subgroup of patients with BDUC exhibited impaired thrombin generation under these conditions. Reduced thrombin generation was frequently associated with increased tissue factor pathway inhibitor (TFPI) activity, suggesting that excessive inhibition of TF-mediated coagulation contributes to the bleeding phenotype in a subset of patients. In vitro addition of concizumab or rFVIIa restored thrombin generation, indicating that defects in TF-dependent coagulation can be pharmacologically corrected. CONCLUSIONS These findings identify dysregulation of the TF-TFPI axis as a potential pathophysiological mechanism underlying bleeding in a subset of patients with BDUC and highlight TFPI inhibition and rFVIIa administration as potential therapeutic approaches. However, the absence of abnormalities in all patients supports the concept that BDUC represents a biologically heterogeneous group of disorders with multiple underlying mechanisms.

[Utility of global coagulation assays for hemostasis management in hyperclearance-type autoimmune acquired coagulation factor V deficiency].

Hemostatic Profiling of Generic Factor Xa Inhibitors Using ROTEM® Viscoelastometry and Multimodal Coagulation Assays: A Real-World Study in a Tunisian Cohort

Background The emergence of generic direct factor Xa inhibitors like apixaban and rivaroxaban has significantly increased the global availability of essential anticoagulants in developing nations. However, we still lack a detailed understanding of how these generic versions behave in real-world clinical practice. This research offers an initial multimodal evaluation, within a Tunisian population, integrating conventional coagulation tests with specific anti-Xa activity and rotational thromboelastometry. Methods We conducted a prospective cross-sectional study at Sahloul University Hospital (Sousse, Tunisia) including 33 patients (mean age 71.3 ± 11.7 years) receiving generic apixaban (n = 25) or rivaroxaban (n = 8) for ≥1 month. Sixty-six paired blood samples were collected at trough (30 min before the next dose) and peak (2–3 h after intake). Standard coagulation tests (PT, aPTT, fibrinogen), calibrated chromogenic anti-Xa activity, and ROTEM®sigma assays were performed. Results Rivaroxaban produced consistent PT prolongation at trough (87.5%) and peak (100%), while apixaban exerted a milder, concentration-dependent effect (45.5% at trough; 73.9% at peak). PT correlated inversely with anti-Xa activity for both agents (apixaban: r = −0.79 at peak; rivaroxaban: r = −0.84 at peak). aPTT and fibrinogen were not significantly affected. Among ROTEM parameters, EXTEM clotting time (CT) was the sole viscoelastic parameter significantly correlated with anti-Xa activity: rivaroxaban r = 0.88 (p = 0.004) at trough and r = 0.87 (p = 0.012) at peak; apixaban ρ = 0.54 (p = 0.021) at trough and ρ = 0.69 (p < 0.001) at peak. INTEM CT showed no significant correlation for either agent. Clot firmness, formation time, and maximum lysis were unaffected by either agent. Conclusion Generic factor Xa inhibitors show hemostatic profiles mirroring those of brand-name versions. EXTEM CT emerged as the ROTEM® parameter most closely tied to anticoagulant intensity, making it a practical bedside surrogate in urgent settings.

Extended Half-Life Recombinant Factor VIII Conjugated with Modifying Substances Does Not Affect Fibrin Clot Formation or Stability in Haemophilia A Blood Samples.

INTRODUCTION Various extended half-life recombinant factor VIII (EHL-FVIII) products have been designed to improve the pharmacokinetic properties of FVIII, allowing prolonged haemostatic coverage and reducing the injection burden in people with haemophilia A. Nevertheless, the influence of direct molecular attachment on fibrin clot formation and stability remains to be investigated. AIM To investigate the stability and architecture of fibrin clots in the presence of various types of EHL-FVIII. METHODS Three EHL-FVIII products with direct attachment modifications (damoctocog alfa pegol, efraloctocog alfa, and rurioctocog alfa pegol) and two standard FVIII (turoctocog alfa and rurioctocog alfa) were added to FVIII-deficient whole blood and plasma at various concentrations for functional comparison. Under whole-blood conditions, functional assays were performed using rotational thromboelastometry (ROTEM) and a microchip flow-chamber system (T-TAS). Under plasma-based conditions, fibrin fibres were directly observed by electron microscopy and coagulation function was assessed using clot waveform analysis (CWA). Anticoagulant and fibrinolytic activities were evaluated by CWA with the addition of activated protein C and tissue plasminogen activator, respectively. RESULTS At equivalent activity levels, none of the assays revealed significant differences among the three EHL products or the two standard products. All contributed comparably to fibrin clot formation and stability, as well as to anticoagulation and fibrinolysis functions. CONCLUSION Direct modification by PEGylation or IgG-Fc fusion to impart EHL characteristics preserves the functional properties of native FVIII. PLAIN LANGUAGE SUMMARY People with haemophilia A require treatment with factor VIII (FVIII) to prevent or control bleeding. Some FVIII products are designed to remain active in the body for a longer time, which can reduce the number of injections needed. This extended half-life is achieved by chemically or biologically modifying FVIII, for example by attaching polyethylene glycol (PEG) or the Fc portion of immunoglobulin G. These treatments are known as extended half-life FVIII (EHL-FVIII) products. However, it has not been fully established whether these modifications affect how blood clots form and remain stable. In this study, we compared three EHL-FVIII products with two standard FVIII products using FVIII-deficient blood and plasma. We evaluated clot formation and stability using several laboratory techniques, including whole-blood assays and scanning electron microscopy. We also examined potential differences in anticoagulant and fibrinolytic properties. At comparable FVIII activity levels, we observed no major differences between the EHL-FVIII products and the standard FVIII products in any of the assays performed. These findings suggest that PEGylation or Fc fusion, which are used to extend the half-life of FVIII, do not impair its functional properties related to fibrin clot formation and stability.

Thrombosis and Haemostasis Clinical Validation of a Point-of-Care Whole Blood Coagulometer in Patients on Factor Xa Inhibitors