Acquired bleeding disorders.

Acquired bleeding disorders can develop in previously healthy people irrespective of age or gender but are particularly common in patients with certain underlying conditions. Here, we review recent advances in the management of acquired haemophilia A (AHA), acquired von Willebrand syndrome (AVWS), and patients with hemostatic abnormalities due to chronic liver disease (CLD). Patients with AHA can now benefit from prophylaxis with emicizumab, a therapeutic antibody that mimics the function of activated coagulation factor VIII. The treatment of AVWS remains challenging in many situations and requires careful consideration of the underlying condition. Haemostatic abnormalities in CLD are often compensated by proportional reduction in pro and anti-haemostatic factors resulting in sustained or even increased thrombin generation. Consequently, bleeding in CLD is rarely caused by haemostatic failure and infusion of plasma or coagulation factor concentrates may not be effective.

Uncommon Causes of Nontraumatic Intracerebral Hemorrhage.

Nontraumatic intracerebral hemorrhage is an important health issue. Although common causes such as hypertension and cerebral amyloid angiopathy predominantly affect the elderly, there exists a spectrum of uncommon etiologies that contribute to the overall incidence of intracerebral hemorrhage. The identification of these rare causes is essential for targeted clinical management, informed prognostication, and strategic secondary prevention where relevant. This topical review explores the uncommon intracerebral hemorrhage causes and provides practical clues for their clinical and imaging identification. By expanding the clinician's differential diagnosis, this review aims to bridge the gap between standard intracerebral hemorrhage classification systems and the nuanced reality of clinical practice.

Definitions of major bleeding for predicting mortality in critically ill adult patients who survived 24 hours while supported with peripheral veno-arterial extracorporeal membrane oxygenation for cardiogenic shock: a comparative historical cohort study.

PURPOSE: The severity of bleeding events is heterogeneously defined during peripheral veno-arterial extracorporeal membrane oxygenation (pVA-ECMO). We studied three bleeding definitions in pVA-ECMO: the Extracorporeal Life Support Organization (ELSO)-serious bleeding, the Bleeding Academic Research Consortium (BARC), and the universal definition of postoperative bleeding (UPDB) classifications. METHODS: We included consecutive adult patients supported by pVA-ECMO for refractory cardiogenic shock admitted to Lille academic hospitals between January 2013 and December 2019. We assessed the association of bleeding definitions with the primary endpoint of 28-day all-cause mortality with the use of multivariate models accounting for time-dependent and competing variables. We compared models' performances using the Harrell's C-Index and the Akaike information criteria. RESULTS: Twenty-eight-day mortality occurred in 128/308 (42%) 308 patients. The ELSO-serious bleeding (hazard ratio [HR], 1.67; 95% confidence interval [CI], 1.09 to 2.56) and BARC ≥ type 2 (HR, 1.55; 95% CI, 1.01 to 2.37) were associated with 28-day mortality (Harrell's C-index, 0.69; 95% CI, 0.63 to 0.74 for both). Predictors of ELSO-serious bleeding were postcardiotomy, body mass index, baseline platelets count, fibrinogen, and hemoglobin levels. CONCLUSION: Extracorporeal Life Support Organization-serious bleeding and BARC ≥ type 2 are relevant definitions of major bleeding regarding their association with mortality in critically ill patients who survived the first 24 hr while supported with pVA-ECMO for cardiogenic shock. STUDY REGISTRATION: CERAR (IRB 00010254-2022-050, Paris, France); first submitted on 18 April 2022.

RéSUMé: OBJECTIF: La gravité des événements hémorragiques est définie de manière hétérogène pendant une oxygénation par membrane extracorporelle veino-artérielle périphérique (ECMO-VA périphérique). Nous avons étudié trois définitions du saignement sous ECMO-VA périphérique : les classifications des saignements graves selon l'Extracorporeal Life Support Organization (ELSO), celles du Bleeding Academic Research Consortium (BARC) et la définition universelle du saignement postopératoire (UPDB). MéTHODE: Nous avons inclus des patient·es adultes pris·es en charge de manière consécutive par ECMO-VA périphérique à la suite d'un choc cardiogénique réfractaire et admis·es dans les centres hospitaliers universitaires de Lille entre janvier 2013 et décembre 2019. Nous avons évalué l'association des définitions du saignement avec le critère d'évaluation principal de mortalité toutes causes confondues à 28 jours à l'aide de modèles multivariés tenant compte des variables dépendantes du temps et concurrentes. Nous avons comparé les performances des modèles à l'aide de l'indice C de Harrell et du critère d'information d'Akaike. RéSULTATS: La mortalité à 28 jours est survenue chez 128/308 (42 %) patient·es. Le saignement grave selon l'ELSO (rapport de risque [RR], 1,67; intervalle de confiance [IC] à 95 %, 1,09 à 2,56) et une classification BARC ≥ type 2 (RR, 1,55; IC 95 %, 1,01 à 2,37) étaient associés à une mortalité à 28 jours (indice C de Harrell, 0,69; IC 95 %, 0,63 à 0,74 pour les deux). Les prédicteurs d'hémorragie grave selon l'ELSO étaient la postcardiotomie, l'indice de masse corporelle, la numération plaquettaire initiale, le taux de fibrinogène et les taux d'hémoglobine. CONCLUSION: Les définitions du saignement grave de l'Extracorporeal Life Support Organization et une classification BARC ≥ type 2 sont des définitions pertinentes des saignements majeurs en ce qui touche à leur association avec la mortalité chez les personnes gravement malades qui ont survécu aux premières 24 heures alors qu'elles étaient prises en charge par ECMO-VA périphérique à la suite d'un choc cardiogénique. ENREGISTREMENT DE L'éTUDE: CERAR (IRB 00010254-2022-050, Paris, France); soumis pour la première fois le 18 avril 2022.

Negative Impact of TET2 Mutations on Long-Term Survival After Transcatheter Aortic Valve Replacement.

Clonal hematopoiesis of indeterminate potential (CHIP) is considered as being a novel age-related risk factor for cardiovascular diseases. By capture-sequencing of a 67-gene panel, we established a large spectrum of CHIP in 258 patients with aortic valve stenosis undergoing transcatheter aortic valve replacement (TAVR) and assessed their association with long-term survival after TAVR. One or several CHIP variants in 35 genes were identified in 68% of the cohort, DNMT3A and TET2 being the 2 most frequently mutated genes. Patients carrying a TET2-CHIP-driver variant with low variant allele frequency (2%-10%) had a significant decrease in overall survival 5 years after TAVR.

Shear Forces Induced Platelet Clearance Is a New Mechanism of Thrombocytopenia.

BACKGROUND: Thrombocytopenia has been consistently described in patients with extracorporeal membrane oxygenation (ECMO) and associated with poor outcome. However, the prevalence and underlying mechanisms remain largely unknown, and a device-related role of ECMO in thrombocytopenia has been hypothesized. This study aims to investigate the mechanisms underlying thrombocytopenia in ECMO patients. METHODS: In a prospective cohort of 107 ECMO patients, we investigated platelet count, functions, and glycoprotein shedding. In an ex vivo mock circulatory ECMO loop, we assessed platelet responses and VWF (von Willebrand factor)-GP Ibα (glycoprotein Ibα) interactions at low- and high-flow rates, in the presence or absence of red blood cells. The clearance of human platelets subjected or not to ex vivo perfusion was studied using an in vivo transfusion model in NOD/SCID (nonobese diabetic/severe combined Immunodeficient) mice. RESULTS: In ECMO patients, we observed a time-dependent decrease in platelet count starting 1 hour after device onset, with a mean drop of 7%, 35%, and 41% at 1, 24, and 48 hours post-ECMO initiation (P=0.00013, P<0.0001, and P<0.0001, respectively), regardless of the type of ECMO. This drop in platelet count was associated with a decrease in platelet GP Ibα expression (before: 47.8±9.1 versus 24 hours post-ECMO: 42.3±8.9 mean fluorescence intensity; P=0.002) and an increase in soluble GP Ibα plasma levels (before: 5.6±3.3 versus 24 hours post-ECMO: 10.8±4.1 µg/mL; P<0.0001). GP Ibα shedding was also observed ex vivo and was unaffected by (1) red blood cells, (2) the coagulation potential, (3) an antibody blocking VWF-GP Ibα interaction, (4) an antibody limiting VWF degradation, and (5) supraphysiological VWF plasma concentrations. In contrast, GP Ibα shedding was dependent on rheological conditions, with a 2.8-fold increase at high- versus low-flow rates. Platelets perfused at high-flow rates before being transfused to immunodeficient mice were eliminated faster in vivo with an accelerated clearance of GP Ibα-negative versus GP Ibα-positive platelets. CONCLUSIONS: ECMO-associated shear forces induce GP Ibα shedding and thrombocytopenia due to faster clearance of GP Ibα-negative platelets. Inhibiting GP Ibα shedding could represent an approach to reduce thrombocytopenia during ECMO.

Colon cancer surgery in von Willebrand disease type 3 setting triggering vascular abnormalities on bowel anastomosis.

Background: von Willebrand disease (VWD) is associated with vascular malformations in the gastrointestinal tract. This complication, more frequent in VWD types 2A and 3, may be due to abnormal angiogenesis, but the precise mechanism is still unclear. Angiogenesis and inflammation are closely linked and can potentiate each other. Key Clinical Question: Can colon inflammation in the setting of cancer surgery potentiate angiogenesis in the VWD setting? Clinical Approach: A woman with VWD type 3 underwent partial colectomy twice for an adenocarcinoma. After managing the first surgery with a plasma-derived von Willebrand factor (VWF) concentrate (Wilfactin; LFB), refractory gastrointestinal bleeding occurred from neovessels on bowel anastomosis. After a multidisciplinary discussion, a second surgery was undertaken with a recombinant VWF concentrate (Veyvondi; Takeda Pharmaceuticals). Pathologic neovessels were again observed on the new anastomosis. Conclusion: Colectomy was complicated twice by pathologic neovessels on bowel anastomosis in 2 distinct procedures managed either with plasma-derived VWF or with recombinant VWF.

Development of a Decision Support Tool for Anticoagulation in Critically Ill Patients Admitted for SARS-CoV-2 Infection: The CALT Protocol.

Severe COVID-19 infections are at high risk of causing thromboembolic events (TEEs). However, the usual exams may be unavailable or unreliable in predicting the risk of TEEs at admission or during hospitalization. We performed a retrospective analysis of two centers (n = 124 patients) including severe COVID-19 patients to determine the specific risk factors of TEEs in SARS-CoV-2 infection at admission and during stays at the intensive care unit (ICU). We used stepwise regression to create two composite scores in order to predict TEEs in the first 48 h (H0-H48) and during the first 15 days (D1-D15) in ICU. We then evaluated the performance of our scores in our cohort. During the period H0-H48, patients with a TEE diagnosis had higher D-Dimers and ferritin values at day 1 (D1) and day 3 (D3) and a greater drop in fibrinogen between D1 and D3 compared with patients without TEEs. Over the period D1-D15, patients with a diagnosis of a TEE showed a more marked drop in fibrinogen and had higher D-Dimers and lactate dehydrogenase (LDH) values at D1 and D3. Based on ROC analysis, the COVID-related acute lung and deep vein thrombosis (CALT) 1 score, calculated at D1, had a diagnostic performance for TEEs at H0-H48, estimated using an area under the curve (AUC) of 0.85 (CI95%: 0.76-0.93, p < 10-3). The CALT 2 score, calculated at D3, predicted the occurrence of TEEs over the period D1-D15 with an estimated AUC of 0.85 (CI95%: 0.77-0.93, p < 10-3). These two scores were used as the basis for the development of the CALT protocol, a tool to assist in the decision to use anticoagulation during severe SARS-CoV-2 infections. The CALT scores showed good performances in predicting the risk of TEEs in severe COVID-19 patients at admission and during ICU stays. They could, therefore, be used as a decision support protocol on whether or not to initiate therapeutic anticoagulation.

Prophylaxis with recombinant von Willebrand factor in patients with type 3 von Willebrand disease: Results of a post hoc analysis from a phase 3 trial.

OBJECTIVES: To describe efficacy/safety of recombinant von Willebrand factor (rVWF) prophylaxis in patients with type 3 von Willebrand disease (VWD). METHODS: This post hoc analysis of a phase 3 open-label trial provides a more detailed analysis of adults with type 3 VWD, categorized based on prior treatment at screening: "Prior On-Demand (OD)" (OD VWF; ≥3 documented spontaneous bleeding events [BEs] requiring VWF in previous 12 months) or "Switch" (plasma-derived [pd] VWF prophylaxis for ≥12 months). Annualized bleeding rates (ABRs) were evaluated during 12 months of rVWF prophylaxis versus historical data from medical records. RESULTS: In the Prior OD group (n = 10), mean spontaneous ABR (sABR) for treated BEs was reduced by 91.6% (ratio, 0.08; 95% CI, 0.02-0.45) versus mean historical sABR. In the Switch group (n = 8), mean sABR for treated BEs was reduced by 47% (ratio, 0.53; 95% CI, 0.08-3.62). One non-serious adverse event (AE) was considered possibly related to rVWF. No treatment-related, fatal, or life-threatening serious AEs were reported, and no patient developed VWF inhibitors. CONCLUSIONS: rVWF prophylaxis reduced sABR in type 3 VWD patients previously treated with OD VWF therapy, and maintained a similar level of hemostatic control in those switching from pdVWF prophylaxis to rVWF prophylaxis.

Efanesoctocog Alfa Prophylaxis for Patients with Severe Hemophilia A.

BACKGROUND: Efanesoctocog alfa provides high sustained factor VIII activity by overcoming the von Willebrand factor-imposed half-life ceiling. The efficacy, safety, and pharmacokinetics of efanesoctocog alfa for prophylaxis and treatment of bleeding episodes in previously treated patients with severe hemophilia A are unclear. METHODS: We conducted a phase 3 study involving patients 12 years of age or older with severe hemophilia A. In group A, patients received once-weekly prophylaxis with efanesoctocog alfa (50 IU per kilogram of body weight) for 52 weeks. In group B, patients received on-demand treatment with efanesoctocog alfa for 26 weeks, followed by once-weekly prophylaxis with efanesoctocog alfa for 26 weeks. The primary end point was the mean annualized bleeding rate in group A; the key secondary end point was an intrapatient comparison of the annualized bleeding rate during prophylaxis in group A with the rate during prestudy factor VIII prophylaxis. Additional end points included treatment of bleeding episodes, safety, pharmacokinetics, and changes in physical health, pain, and joint health. RESULTS: In group A (133 patients), the median annualized bleeding rate was 0 (interquartile range, 0 to 1.04), and the estimated mean annualized bleeding rate was 0.71 (95% confidence interval [CI], 0.52 to 0.97). The mean annualized bleeding rate decreased from 2.96 (95% CI, 2.00 to 4.37) to 0.69 (95% CI, 0.43 to 1.11), a finding that showed superiority over prestudy factor VIII prophylaxis (P<0.001). A total of 26 patients were enrolled in group B. In the overall population, nearly all bleeding episodes (97%) resolved with one injection of efanesoctocog alfa. Weekly prophylaxis with efanesoctocog alfa provided mean factor VIII activity of more than 40 IU per deciliter for the majority of the week and of 15 IU per deciliter at day 7. Prophylaxis with efanesoctocog alfa for 52 weeks (group A) improved physical health (P<0.001), pain intensity (P = 0.03), and joint health (P = 0.01). In the overall study population, efanesoctocog alfa had an acceptable side-effect profile, and the development of inhibitors to factor VIII was not detected. CONCLUSIONS: In patients with severe hemophilia A, once-weekly efanesoctocog alfa provided superior bleeding prevention to prestudy prophylaxis, normal to near-normal factor VIII activity, and improvements in physical health, pain, and joint health. (Funded by Sanofi and Sobi; XTEND-1 ClinicalTrials.gov number, NCT04161495.).

Communication from the Scientific Standardization Committees of the International Society on Thrombosis and Haemostasis on vascular endothelium-related biomarkers in disseminated intravascular coagulation.

Disseminated intravascular coagulation (DIC) is not a disease criterion but a pathomechanistic process that accompanies various underlying diseases. According to the International Society on Thrombosis and Haemostasis definition, endothelial injury is an essential component in addition to systemic coagulation activation. Despite this definition, current diagnostic criteria for DIC do not include biomarkers for vascular endothelial injury. Endothelial cells are critical for hemostatic regulation because they produce various antithrombotic substances and express anticoagulant factors at the same time as facilitating coagulation, inflammatory reactions, platelet aggregation, and fibrinolysis with acute injury. Endothelial cells also exhibit various receptors, adhesion molecules, and the critical role of glycocalyx that regulates cellular interactions in thromboinflammation. For clinicians, biomarkers suitable for assessing endothelial injury are not readily available. Although we still do not have ideal biomarkers, antithrombin activity and von Willebrand factor can be candidates for the endothelium-related markers because those reflect the severity and are available in most clinical settings. Further, the dysfunction of endothelial cell in DIC arising from various underlying diseases is likely highly variable. For example, the involvement of endothelial dysfunction is significant in sepsis-induced coagulopathy, while moderate in trauma-induced coagulopathy, and variable in hematologic malignancy-associated coagulopathy. Because of the complexity of disease status associated with DIC, further research searching clinically available endothelium-related biomarkers is expected to establish individualized diagnostic criteria and potential therapeutic approaches.

Modulation of inflammatory M1-macrophages phenotype by valvular interstitial cells.

BACKGROUND: Aortic valve stenosis involves inflammation, excess deposition of a collagen-rich extracellular matrix, and calcification. Recent studies have shown that M1 or inflammatory macrophages derived from infiltrating monocytes promote calcification of valvular interstitial cells, the most prevalent cell type of the aortic valve. We hypothesized that valvular interstitial cells could modulate inflammatory macrophages phenotype. METHODS: We first assessed macrophage phenotype in human aortic valve stenosis and control aortic valves from donors. Then, we examined profibrotic and inflammatory-related gene expression in valves and valvular interstitial cells. Finally, we investigated whether valvular interstitial cells can modify the phenotype of inflammatory macrophages. RESULTS: Circulating monocytes and plasma transforming growth factor beta-1 levels of patients with aortic valve stenosis were significantly higher compared with patients without aortic valve stenosis. Histologic analysis of thickened spongiosa of the aortic valve from patients with aortic valve stenosis showed a high macrophage infiltration but a low matrix metalloproteinase-9 expression compared with control aortic valves. On the other hand, valvular interstitial cell culture of aortic valve stenosis exhibited a profibrotic phenotype with a high expression of transforming growth factor beta-1 and transforming growth factor beta-1/transforming growth factor beta-3 ratio but a decreased expression of the peroxisome proliferator-activated receptor gamma nuclear receptor. Valvular interstitial cell-conditioned media of aortic valve stenosis led to a decrease in enzymatic activity of matrix metalloproteinase-9 and an increase in production of collagen in inflammatory macrophages compared with valvular interstitial cell-conditioned media from control aortic valve donors. CONCLUSIONS: These findings indicate that profibrotic valvular interstitial cells promote the imbalance of extracellular matrix remodeling by reducing matrix metalloproteinase-9 production on inflammatory macrophages that lead to excessive collagen deposition observed in aortic valve stenosis. Further investigation is needed to clarify the role of transforming growth factor beta-1/proliferator-activated receptor gamma nuclear receptor/matrix metalloproteinase-9 in aortic valve stenosis.

Inflammatory markers and auto-Abs to type I IFNs in COVID-19 convalescent plasma cohort study.

BACKGROUND: COVID-19 convalescent plasma (CCP) contains neutralising anti-SARS-CoV-2 antibodies that may be useful as COVID-19 passive immunotherapy in patients at risk of developing severe disease. Such plasma from convalescent patients may also have additional immune-modulatory properties when transfused to COVID-19 patients. METHODS: CCP (n = 766) was compared to non-convalescent control plasma (n = 166) for soluble inflammatory markers, ex-vivo inflammatory bioactivity on endothelial cells, neutralising auto-Abs to type I IFNs and reported adverse events in the recipients. FINDINGS: CCP exhibited a statistically significant increase in IL-6 and TNF-alpha levels (0.531 ± 0.04 vs 0.271 ± 0.04; (95% confidence interval [CI], 0.07371-0.4446; p = 0.0061) and 0.900 ± 0.07 vs 0.283 ± 0.07 pg/mL; (95% [CI], 0.3097-0.9202; p = 0.0000829) and lower IL-10 (0.731 ± 0.07 vs 1.22 ± 0.19 pg/mL; (95% [CI], -0.8180 to -0.1633; p = 0.0034) levels than control plasma. Neutralising auto-Abs against type I IFNs were detected in 14/766 (1.8%) CCPs and were not associated with reported adverse events when transfused. Inflammatory markers and bioactivity in CCP with or without auto-Abs, or in CCP whether or not linked to adverse events in transfused patients, did not differ to a statistically significant extent. INTERPRETATION: Overall, CCP exhibited moderately increased inflammatory markers compared to the control plasma with no discernible differences in ex-vivo bioactivity. Auto-Abs to type I IFNs detected in a small fraction of CCP were not associated with reported adverse events or differences in inflammatory markers. Additional studies, including careful clinical evaluation of patients treated with CCP, are required in order to further define the clinical relevance of these findings. FUNDING: French National Blood Service-EFS, the Association "Les Amis de Rémi" Savigneux, France, the "Fondation pour la Recherche Médicale (Medical Research Foundation)-REACTing 2020".

A nanobody against the VWF A3 domain detects ADAMTS13-induced proteolysis in congenital and acquired VWD.

von Willebrand factor (VWF) is a multimeric protein, the size of which is regulated via ADAMTS13-mediated proteolysis within the A2 domain. We aimed to isolate nanobodies distinguishing between proteolyzed and non-proteolyzed VWF, leading to the identification of a nanobody (designated KB-VWF-D3.1) targeting the A3 domain, the epitope of which overlaps the collagen-binding site. Although KB-VWF-D3.1 binds with similar efficiency to dimeric and multimeric derivatives of VWF, binding to VWF was lost upon proteolysis by ADAMTS13, suggesting that proteolysis in the A2 domain modulates exposure of its epitope in the A3 domain. We therefore used KB-VWF-D3.1 to monitor VWF degradation in plasma samples. Spiking experiments showed that a loss of 10% intact VWF could be detected using this nanobody. By comparing plasma from volunteers to that from congenital von Willebrand disease (VWD) patients, intact-VWF levels were significantly reduced for all VWD types, and most severely in VWD type 2A-group 2, in which mutations promote ADAMTS13-mediated proteolysis. Unexpectedly, we also observed increased proteolysis in some patients with VWD type 1 and VWD type 2M. A significant correlation (r = 0.51, P < .0001) between the relative amount of high-molecular weight multimers and levels of intact VWF was observed. Reduced levels of intact VWF were further found in plasmas from patients with severe aortic stenosis and patients receiving mechanical circulatory support. KB-VWF-D3.1 is thus a nanobody that detects changes in the exposure of its epitope within the collagen-binding site of the A3 domain. In view of its unique characteristics, it has the potential to be used as a diagnostic tool to investigate whether a loss of larger multimers is due to ADAMTS13-mediated proteolysis.

Successful and safe response to ibrutinib alone in treating relapsed Waldenström macrogobulinemia and related acquired von Willebrand syndrome: an option to consider.

Ibrutinib, a first-class Bruton tyrosine kinase inhibitor, is known to be associated with adverse bleeding events and has been recently approved for the treatment of relapse Waldenström macroglobulinemia (WM). Here, we report the exhaustive clinical and biological follow-up of 2 patients treated by ibrutinib alone in the context of relapsed WM with an acquired von Willebrand syndrome (AVWS) complication. In two cases, ibrutinib has been shown to be quickly efficient and safe for treating both AVWS and its underlying condition the WM, without bleeding complications. Interestingly, ibrutinib treatment brings a rapid and extended over time normalization of von Willebrand factor clearance. These observations show that ibrutinib is a valuable therapeutic option in relapsed WM patients associated with AVWS and highlighting the need for further cohort studies with long-term follow-up of patients to confirm the efficacy and safety of a treatment by ibrutinib for WM patients with AVWS complication.

Tranexamic acid dose-response relationship for antifibrinolysis in postpartum haemorrhage during Caesarean delivery: TRACES, a double-blind, placebo-controlled, multicentre, dose-ranging biomarker study.

BACKGROUND: The optimal dose of tranexamic acid to inhibit hyperfibrinolysis in postpartum haemorrhage is unclear. Tranexamic Acid to Reduce Blood Loss in Hemorrhagic Cesarean Delivery (TRACES) was a double-blind, placebo-controlled, randomised, multicentre dose-ranging study to determine the dose-effect relationship for two regimens of intravenous tranexamic acid vs placebo. METHODS: Women experiencing postpartum haemorrhage during Caesarean delivery were randomised to receive placebo (n=60), tranexamic acid 0.5 g (n=57), or tranexamic acid 1 g i.v. (n=58). Biomarkers of fibrinolytic activation were assayed at five time points, with inhibition of hyperfibrinolysis defined as reductions in the increase over baseline in D-dimer and plasmin-antiplasmin levels and in the plasmin peak time. RESULTS: In the placebo group, hyperfibrinolysis was evidenced by a mean increase over baseline [95% confidence interval] of 93% [68-118] for D-dimer level at 120 min and 56% [25-87] for the plasmin-antiplasmin level at 30 min. A dose of tranexamic acid 1 g was associated with smaller increases over baseline (D-dimers: 38% [13-63] [P=0.003 vs placebo]; plasmin-antiplasmin: -2% [-32 to 28] [P=0.009 vs placebo]). A dose of tranexamic acid 0.5 g was less potent, with non-significant reductions (D-dimers: 58% [32-84] [P=0.06 vs placebo]; plasmin-antiplasmin: 13% [18-43] [P=0.051]). Although both tranexamic acid doses reduced the plasmin peak, reduction in plasmin peak time was significant only for the 1 g dose of tranexamic acid. CONCLUSIONS: Fibrinolytic activation was significantly inhibited by a dose of intravenous tranexamic acid 1 g but not 0.5 g. Pharmacokinetic-pharmacodynamic modelling of these data might identify the best pharmacodynamic monitoring criteria and the optimal tranexamic acid dosing regimen for treatment of postpartum haemorrhage. CLINICAL TRIAL REGISTRATION: NCT02797119.

ADAMTS13 inhibition to treat acquired von Willebrand syndrome during mechanical circulatory support device implantation.

BACKGROUND: Acquired von Willebrand syndrome (aVWS) is common in patients with mechanical circulatory support (MCS) devices. In these patients, the high shear stress in the device leads to increased shear-induced proteolysis of von Willebrand factor (VWF) by A Disintegrin And Metalloprotease with Thrombospondin type 1 repeats, number 13 (ADAMTS13). As a result, the high molecular weight (HMW) VWF multimers are lost, leading to a decreased VWF function and impaired hemostasis that could explain the bleeding complications that are frequently observed in these patients. To counteract this abnormal VWF degradation by ADAMTS13, we developed a novel targeted therapy, using an anti-ADAMTS13 monoclonal antibody (mAb) that inhibits the shear-induced proteolysis of VWF by ADAMTS13. METHODS: Human or bovine blood was circulated through in vitro MCS device systems with either inhibitory anti-ADAMTS13 mAb 3H9 or 17C7 (20 µg/ml) or control anti-ADAMTS13 mAb 5C11 or phosphate buffered saline (PBS). VWF multimers and function (collagen binding activity) were determined at different time points. Next, Impella pumps were implanted in calves and the calves were injected with PBS and subsequently treated with mAb 17C7. VWF, ADAMTS13, and blood parameters were determined. RESULTS: We demonstrated that blocking ADAMTS13 could prevent the loss of HMW VWF multimers in in vitro MCS device systems. Importantly, our antibody could reverse aVWS in a preclinical Impella-induced aVWS calf model. CONCLUSION: Hence, inhibition of ADAMTS13 could become a novel therapeutic strategy to manage aVWS in MCS device patients.

Identification of von Willebrand factor D4 domain mutations in patients of Afro-Caribbean descent: In vitro characterization.

Background: Von Willebrand disease was diagnosed in two Afro-Caribbean patients and sequencing of the VWF gene (VWF) revealed the presence of multiple variants located throughout the gene, including variants located in the D4 domain of VWF: p.(Pro2145Thrfs*5) in one patient and p.(Cys2216Phefs*9) in the other patient. Interestingly, D4 variants have not been studied often. Objectives: Our goal was to characterize how the D4 variants p.(Pro2145Thrfs*5) and p.(Cys2216Phefs*9) influenced VWF biosynthesis/secretion and functions using in vitro assays. Methods: Recombinant VWF (rVWF), mutant or wild-type, was produced via transient transfection of the human embryonic kidney cell line 293T. The use of different tags for the wild-type and the mutant allele allowed us to distinguish between the two forms when measuring VWF antigen in medium and cell lysates. Binding of rVWF to its ligands, collagen, factor VIII, ADAMTS13, and platelet receptors was also investigated. Results: Homozygous expression of the p.(Cys2216Phefs*9)-rVWF mutation resulted in an almost complete intracellular retention of the protein. Heterozygous expression led to secretion of almost exclusively wild-type-rVWF, logically capable of normal interaction with the different ligands. In contrast, the p.(Pro2145Thrfs*5)-rVWF exhibited reduced binding to type III collagen and αIIbß3 integrin compared to wild-type-rVWF. Conclusions: We report two mutations of the D4 domains that induced combined qualitative and quantitative defects.