Thrombin generation on vascular cells in the presence of factor VIII and/or emicizumab

Emicizumab promotes factor Xa generation on endothelial cells

BACKGROUND

Until recently, the treatment of hemophilia A relied on factor (F)VIII replacement. However, up to one-third of patients with severe hemophilia A develop neutralizing alloantibodies that render replacement therapies ineffective. The development of emicizumab, a bispecific antibody that partially mimics FVIIIa, has revolutionized the treatment of these patients. However, the use of an activated prothrombin complex concentrate [FEIBA (Takeda)] to treat breakthrough bleeding in patients on emicizumab has been associated with thrombotic complications including a unique microangiopathy.

OBJECTIVES

We hypothesized that the thrombotic complications observed with the combination of emicizumab and FEIBA might be due to excessive expression of procoagulant activity on the surface of endothelial cells.

METHODS

We examined the ability of emicizumab to promote FX activation on endothelial cells using 2 cell culture models.

RESULTS

We found that endothelial cells readily support emicizumab-mediated activation of FX by FIXa. The level of FXa generation depends on the concentration of available FIXa. The addition of FEIBA to emicizumab increased FXa generation in a dose-dependent manner on endothelial cells in both models. The rate of FXa generation was further enhanced by endothelial cell activation. However, unlike emicizumab, we found limited FXa generation in the presence of FVIII(a), which followed a significant lag time and was not dependent on FIXa concentration under these conditions.

CONCLUSION

Emicizumab promotes FXa generation on the surface of endothelial cells, which is markedly enhanced in the presence of FEIBA. These findings demonstrate a potential mechanism for the thrombotic complications seen with the combined use of emicizumab and FEIBA.

Characterization of active peptides derived from three leeches and comparison of their anti-thrombotic mechanisms using the tail vein thrombosis model in mice and metabonomics

Background and aims: The increasing incidence of cardiovascular diseases has created an urgent need for safe and effective anti-thrombotic agents. Leech, as a traditional Chinese medicine, has the effect of promoting blood circulation and removing blood stasis, but its real material basis and mechanism of action for the treatment of diseases such as blood stasis and thrombosis have not been reported. Methods: In this study, Whitmania Pigra Whitman (WPW), Hirudo nipponica Whitman (HNW) and Whitmania acranutata Whitman (WAW) were hydrolyzed by biomimetic enzymatic hydrolysis to obtain the active peptides of WPW (APP), the active peptides of HNW (APH) and the active peptides of WAW (APA), respectively. Then their structures were characterized by sykam amino acid analyzer, fourier transform infrared spectrometer (FT-IR), circular dichroism (CD) spectrometer and LC-MS. Next, the anti-thrombotic activities of APP, APH and APA were determined by carrageenan-induced tail vein thrombosis model in mice, and the anti-thrombotic mechanisms of high-dose APP group (HAPP), high-dose APH group (HAPH) and high-dose APA group (HAPA) were explored based on UHPLC-Q-Exactive Orbitrap mass spectrometry. Results: The results showed that the amino acid composition of APP, APH and APA was consistent, and the proportion of each amino acid was few different. The results of FT-IR and CD showed that there were no significant differences in the proportion of secondary structures (such as β-sheet and random coil) and infrared absorption peaks between APP, APH and APA. Mass spectrometry data showed that there were 43 common peptides in APP, APH and APA, indicating that the three have common material basis. APP, APH and APA could significantly inhibit platelet aggregation, reduce black-tail length, whole blood viscosity (WBV), plasma viscosity (PV), and Fibrinogen (FIB), and prolong coagulation time, including activated partial thrombin time (APTT), prothrombin time (PT) and thrombin time (TT). In addition, 24 metabolites were identified as potential biomarkers associated with thrombosis development. Among these, 19, 23, and 20 metabolites were significantly normalized after administration of HAPP, HAPH, and HAPA in the mice, respectively. Furthermore, the intervention mechanism of HAPP, HAPH and HAPA on tail vein thrombosis mainly involved in linoleic acid metabolism, primary bile acid biosynthesis and ether lipid metabolism. Conclusion: Our findings suggest that APP, APH and APA can exert their anti-blood stasis and anti-thrombotic activities by interfering with disordered metabolic pathways in vivo, and there is no significant difference in their efficacies.