Search

Computational models of the coagulation cascade are used for a wide range of applications in bio-medical engineering such as drug and bio-medical device developments. However, a lack of robustness of numerical models has been highlighted when studying clinically relevant scenarios. In order to develop more robust models, numerical simulations need to be confronted with realistic situations relevant to clinical practice. In this work, two well-established numerical representations of the coagulation cascade initiated by the intrinsic and extrinsic systems, respectively, were compared with thrombin generation assays considering realistic pathological conditions. Proper modifications were needed to align the in vitro and in silico data, namely; adapting initial conditions to the thrombin assay system, omitting reactions irrelevant to our case study, and improving the fitting of some reaction rates. The modified models were able to capture the experimental trends of thrombin generation for a range of concentrations of factors XII, XI, and VIII for cases in which the coagulation cascade is triggered through the extrinsic and intrinsic systems. Our work emphasizes that when existing coagulation cascade models are extrapolated to experimental settings for which they were not calibrated, careful adjustments must be made. We show that the two coagulation models used in this work can predict physiological conditions, but when studying pathological conditions, proper modifications are needed to improve the numerical results.

Pharmacokinetic properties of recombinant FVIIa in inherited FVII deficiency account for a large volume of distribution at steady state and a prolonged pharmacodynamic effect

Background: The European Network of Rare Bleeding Disorders (EN-RBD) was established to bridge the gap between knowledge and practise in the care of patients with RBDs. Objectives: To explore the relationship between coagulation factor activity level and bleeding severity in patients with RBDs. Patients/Methods: Cross-sectional study using data from 489 patients registered in the EN-RBD. Coagulation factor activity levels were retrieved. Clinical bleeding episodes were classified into four categories according to severity. Results: The mean age of patients at data collection was 31 years (range, 7 months to 95 years), with an equal sex distribution. On linear regression analysis, there was a strong association between coagulation factor activity level and clinical bleeding severity for fibrinogen, factor (F) X, FXIII, and combined FV and FVIII deficiencies. A weaker association was present for FV and FVII deficiencies. There was no association between coagulation factor activity level and clinical bleeding severity for FXI. The coagulation factor activity levels that were necessary for patients to remain asymptomatic were: fibrinogen, > 100 mg dL(-1); FV, 12 U dL(-1); combined FV + VIII, 43 U dL(-1); FVII, 25 U dL(-1); FX, 56 U dL(-1); FXI, 26 U dL(-1); FXIII, 31 U dL(-1). Moreover, coagulation factor activity levels that corresponded with Grade III bleeding were: undetectable levels for fibrinogen, FV and FXIII, < 15 U dL(-1) for combined FV + VIII; < 8 U dL(-1) for FVI; < 10 U dL(-1) for FX; and < 25 U dL(-1) for FXI. Conclusions: There is a heterogeneous association between coagulation factor activity level and clinical bleeding severity in different RBDs. A strong association is only observed in fibrinogen, FX and FXIII deficiencies.

Introduction A paucity of data exists on the incidence, diagnosis and treatment of bleeding in women with inherited factor VII (FVII) deficiency. Aim Here we report results of a comprehensive analysis from two international registries of patients with inherited FVII deficiency, depicting the clinical picture of this disorder in women and describing any gender-related differences. Methods A comprehensive analysis of two fully compatible, international registries of patients with inherited FVII deficiency (International Registry of Factor VII deficiency, IRF7; Seven Treatment Evaluation Registry, STER) was performed. Results In our cohort (N = 449; 215 male, 234 female), the higher prevalence of mucocutaneous bleeds in females strongly predicted ensuing gynaecological bleeding (hazard ratio = 12.8, 95% CI 1.68–97.6, P = 0.014). Menorrhagia was the most prevalent type of bleeding (46.4% of patients), and was the presentation symptom in 12% of cases. Replacement therapies administered were also analysed. For surgical procedures (n = 50), a receiver operator characteristic analysis showed that the minimal first dose of rFVIIa to avoid postsurgical bleeding during the first 24 hours was 22 μg kg−1, and no less than two administrations. Prophylaxis was reported in 25 women with excellent or effective outcomes when performed with a total weekly rFVIIa dose of 90 μg kg−1 (divided as three doses). Conclusion Women with FVII deficiency have a bleeding disorder mainly characterized by mucocutaneous bleeds, which predicts an increased risk of ensuing gynaecological bleeding. Systematic replacement therapy or long-term prophylaxis with rFVIIa may reduce the impact of menorrhagia on the reproductive system, iron loss and may avoid unnecessary hysterectomies.

International audience

We report 2 asymptomatic homozygotes for the nonsense p.R462X mutation affecting the carboxy-terminus of coagulation factor VII (FVII, 466 aminoacids). FVII levels of 3-5% and 2.7 ± 0.4% were found in prothrombin time-based and activated factor X (FXa) generation assays with human thromboplastins. Noticeably, FVII antigen levels were barely detectable (0.7 ± 0.2%) which suggested a gain-of-function effect. This effect was more pronounced with bovine thromboplastin (4.8 ± 0.9%) and disappeared with rabbit thromboplastin (0.7 ± 0.2%). This suggests that the mutation influences tissue factor/FVII interactions. Whereas the recombinant rFVII-462X variant confirmed an increase in specific activity (~400%), a panel of nonsense (p.P466X, p.F465X, p.P464X, p.A463X) and missense (p.R462A, p.R462Q, p.R462W) mutations of the FVII carboxy-terminus resulted in reduced secretion but normal specific activity. These data provide evidence for counteracting pleiotropic effects of the p.R462X mutation, which explains the asymptomatic FVII deficiency, and contributes to our understanding of the role of the highly variable carboxy-terminus of coagulation serine proteases.

Abstract 665 Introduction Prophylaxis is considered a difficult endeavour in FVII deficiency, especially because of the very short FVII zymogen and FVIIa half-lives, mainly in childhood. The Seven Treatment Evaluation Registry (STER, www.targetseven.org) is a prospective observational, multi-centre, web-based registry concerned with the evaluation of treatments for spontaneous bleeding episodes, surgery and prophylaxis in patients with FVII deficiency. As regards prophylaxis, STER provides the frame for a structured and detailed data capture aiming at: a) identifying patients in whom prophylaxis is advisable, b) defining clinical settings in which prophylaxis is necessary and c) describing effective and safe dosing schedules. Materials and Methods Together with basic clinical and laboratory data related to the patient, the following information has been collected for each prophylaxis treatment course: i. Type (primary or secondary, short- and long-term), ii. Indication iii. Start/stop date iv. Schedule, v. Concomitant medications and illness vi. Bleeding episodes, vii. Other complications. The prophylactic regimen adopted reflected the decision of each enrolling physician as was the type of replacement therapy. FVIIc assays were performed at each centre lab, whereas inhibitor assays were centralized. Results Nineteen patients with FVII deficiency (12 females, 7 males, age ranging from new born to 71 y.) were enrolled as a long-term prophylaxis was deemed necessary by the treating physician. FVIIc levels ranged from Conclusions We have identified a subset of patients with a FVII deficiency who may need a continuous, long-term prophylaxis treatment; these patients have a severe disease characterized by CNS or GI bleeding, hemarthrosis (mostly as presenting symptoms) or menorrhagia associated with low to very low FVIIc levels. Reported dosing and schedules varied widely so it is difficult to ascertain which is the optimal prophylaxis schedule but the 3 dose weekly regimens associated with medium to high replacement therapy doses appear the most efficacious. We have also shown that long-term prophylaxis is feasible in patients with an inhibitor to FVII. Disclosures: Knudsen: Novonordisk: Employment.