Thrombin Generation In Patients Research Articles

Assessment of Platelet Aggregation and Thrombin Generation in Patients with Familial Chylomicronemia Syndrome Treated with Volanesorsen: A Cross-Sectional Study.

The antisense oligonucleotide against APOC3 mRNA volanesorsen was recently introduced to treat Familial Chylomicronemia Syndrome (FCS). Cases of decreased platelet count are reported among patients treated with volanesorsen. The aim of the study was to evaluate platelet function and thrombin generation (TG) assessment in FCS patients receiving volanesorsen. We performed a cross-sectional study on FCS patients treated with volanesorsen. Changes in platelet count PLC were assessed from baseline to Tw12 and Tw36. To assess TG, samples were processed by CAT (with PPP-reagent LOW). The results were expressed by the thrombogram graphic (thrombin variation over time); LagTime; endogenous thrombin potential (ETP); peak; time to reach peak (ttpeak), StartTail and Velocity Index. Platelet aggregation was assessed by testing different agonists using the turbidimetry method. Four FCS patients and four matched healthy controls were included in the present study. Changes in PLC were 30% at Tw12 and 34% at Tw36. Thrombin generation results showed values in the normal range (for patients and controls, respectively, LagTime:10.42 ± 4.40 and 9.25 ± 0.99; ttPeak:14.33 ± 4.01 and 13.10 ± 0.67; StartTail: 32.13 ± 3.54 and 29.46 ± 1.69; Velocity Index: 20.21 ± 3.63 and 33.05 ± 13.21; ETP: 599.80 ± 73.47 and 900.2 ± 210.99; peak value: 76.84 ± 1.07 and 123.30 ± 39.45) and no significant difference between cases and controls. Platelet aggregation test showed values in range, with no significant difference compared to healthy controls. Our study showed for the first time that no significant changes in general hemostasis assessed by TG and in platelet function were observed in FCS patients receiving volanesorsen.

Clot lysis time and thrombin generation in patients undergoing transcatheter aortic valve implantation.

Aortic valve stenosis (AS) is the most prevalent valvular heart disease and is associated with a significant increase in mortality. AS has been shown to be linked with numerous coagulation system abnormalities, including increased fibrin deposition on the stenotic aortic valves. Transcatheter aortic valve implantation (TAVI) is the primary treatment method for patients at high surgical risk. The aim of the study was to assess the impact of treating severe AS with TAVI on thrombin generation and clot lysis time (CLT). We studied 135 symptomatic AS patients recommended for TAVI by the local Heart Team. All measurements were performed before and 5-7 days after TAVI. Alongside clinical assessment and echocardiographic analysis, we assessed clot lysis time (CLT) and thrombin generation parameters, including lag time, peak thrombin generation, time to peak thrombin generation (ttPeak), and endogenous thrombin potential (ETP). 70 patients were included in the final analysis. After TAVI, there was a significant 9% reduction in CLT despite a 12% increase in fibrinogen concentration. We observed significant increase in lag time and ttPeak (20% and 12%, respectively), and 13% decrease in peak thrombin concentration compared to pre-procedural levels. Multivariable linear regression analysis demonstrated that baseline CLT and C-reactive protein (CRP) levels were independent predictors of significant reduction in mean aortic gradient, defined as TAVI procedure success. CLT and peak thrombin concentration decreased, while Lag time and ttPeak increased significantly after TAVI. Multivariable linear regression analysis demonstrated CLT and CRP levels as independent predictors of achieving a reduction in mean aortic gradient, defining TAVI procedure success.

Abstract TP294: Sex Differences in Thrombin Generation in Patients With Acute Ischemic Stroke

Background and Purpose: Sex differences in stroke exist, including variation in stroke risk and outcome. Differences in thrombin generation may contribute to this variation between females and males. To examine this, we assessed sex differences in thrombin generation between females and males with acute ischemic stroke and the relationship to blood cell gene expression. Methods: In 97 patients with acute ischemic stroke thrombin generation was measured by thrombin generation assay. Blood cell gene expression was measured by microarray. Differences in thrombin generation between sexes were identified and the relationship to blood cell gene expression examined. Genes associated with sex differences in thrombin generation were analysed by functional pathway analysis. Results: Females and males had similar overall capacity to generate thrombin. The peak thrombin generated in females was 468.8nM (SD 91.6), comparable to males 479.3 (SD 90.8; p=0.58). Lag time, time to peak thrombin, and endogenous thrombin potential were also similar between females and males. While overall thrombin generation was comparable between females and males with stroke, differences in genes that promote this thrombin generation exist. Females with high peak thrombin had an increase in genes that promote thrombosis, and platelet activation. In contrast, males with high peak thrombin had a decrease in genes involved in thrombus degradation. Conclusion: Females and males with acute ischemic stroke have similar capacity to generate thrombin. However, differences may exist in how this thrombin generation is achieved, with females having increased thrombin signaling, and platelet activation, and males having decreased thrombus degradation. This suggests regulatory differences in thrombosis may exist between females and males that may contribute to sex differences in stroke.

Sex Differences in Thrombin Generation in Patients with Acute Ischemic Stroke.

Sex differences in stroke exist, including variation in stroke risk and outcome. Differences in thrombin generation may contribute to this variation between females and males. To examine this, we assessed sex differences in thrombin generation between females and males with acute ischemic stroke and the relationship to blood cell gene expression. In 97 patients with acute ischemic stroke, thrombin generation was measured by thrombin generation assay. Blood cell gene expression was measured by microarray. Differences in thrombin generation between sexes were identified and the relationship to blood cell gene expression examined. Genes associated with sex differences in thrombin generation were analyzed by functional pathway analysis. Females and males had similar overall capacity to generate thrombin. The peak thrombin generated in females was 468.8nM (SD 91.6), comparable to males (479.3nM;SD 90.8; p = 0.58). Lag time, time to peak thrombin, and endogenous thrombin potential were also similar between females and males. While overall thrombin generation was comparable between females and males with stroke, differences in genes that promote this thrombin generation exist. Females with high peak thrombin had an increase in genes that promote thrombosis, and platelet activation. In contrast, males with high peak thrombin had a decrease in genes involved in thrombus degradation. Females and males with acute ischemic stroke have similar capacity to generate thrombin, however, differences may exist in how this thrombin generation is achieved, with females having increased thrombin signaling, and platelet activation, and males having decreased thrombus degradation. This suggests regulatory differences in thrombosis may exist between females and males that may contribute to sex differences in stroke.

Augmented thrombin formation is related to circulating levels of extracellular vesicles exposing tissue factor and citrullinated histone-3 in anti-neutrophil cytoplasmic antibody-associated vasculitides.

To study circulating myeloperoxidase (MPO)-positive extracellular vesicles (MPO+EVs) exposing citrullinated histone-3 (H3Cit), tissue factor (TF), and plasminogen (Plg) in association to thrombin generation in patients with anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV). We have involved well-characterized patients with AAV together with population-based controls. Flow cytometry was used to assess the levels of MPO+EVs in citrated plasma. MPO+EVs were phenotyped by anti-MPO-antibodies together with anti-CD142 (anti-TF), anti-H3Cit, and anti-Plg antibodies. A modified Calibrated Automated Thrombogram (CAT) assay was utilized to measure thrombin generation in plasma initiated by EVs-enriched pellets. The activity of AAV was evaluated with the Birmingham Vasculitis Activity Score (BVAS). This study comprised 46 AAV patients, 23 in the active stage of the disease and 23 in remission, as well as 23 age- and sex matched population-based controls. Augmented levels of all investigated MPO+ EVs were found in active AAV patients in comparison to the subgroup of patients in remission and controls. Thrombin generation, measured by endogenous thrombin potential (ETP) and peak of thrombin formation, was higher in plasma when triggered by EVs-enriched pellet from AAV patients. ETP and peak were associated with the levels of MPO+TF+ and MPO+H3Cit+ EVs. Additionally, MPO+TF+ EVs correlated with the disease activity evaluated with BVAS. Augmented thrombin generation is found in AAV patients regardless of disease activity and is associated with higher exposure of TF and H3Cit on MPO+EVs. This may contribute to the increased risk of thrombosis seen in AAV patients.

Procoagulant effect of extracellular vesicles in patients after transcatheter aortic valve replacement or transcatheter aortic valve replacement with percutaneous coronary intervention.

Patients with severe aortic stenosis (AS) after replacement of the transcatheter aortic valve (TAVR) are more likely to develop thrombotic complications such as cerebral embolism and artificial valve thrombosis. However, the mechanism is not yet well defined. We aimed to explore the plasma extracellular vesicles (EVs) levels and their role in the induction of procoagulant activity (PCA) in patients receiving TAVR alone or TAVR with percutaneous coronary intervention (PCI). EVs were analyzed with flow cytometer. Markers of platelet and endothelial cell activation were quantified using selective enzyme-linked immunosorbent assay (ELISA) kits. Procoagulant activity (PCA) was assessed by clotting time, purified clotting complex assays, and fibrin production assays. Our results confirmed that EVs with positive phosphatedylserin (PS+EV), platelet EVs (PEVs) and positive tissue factor EVs (TF+EVs) were higher in patients following TAVR than before TAVR, particularly in TAVR with PCI. Furthermore, endothelial-derived EVs (EEVs) were also higher in patients after TAVR with PCI than pre-TAVR, however, the EEVs levels in TAVR alone patients were gradually reduce than pre-TAVR. In addition, we further proved that total EVs contributed to dramatically shortened coagulation time, increased intrinsic/extrinsic factor Xa and thrombin generation in patients after TAVR, especially in TAVR with PCI. The PCA was markedly attenuated by approximately 80% with lactucin. Our study reveals a previously unrecognized link between plasma EV levels and hypercoagulability in patients after TAVR, especially TAVR with PCI. Blockade of PS+EVs may improve the hypercoagulable state and prognosis of patients.

Intraindividual variability over time of thrombin generation in patients with cirrhosis

BackgroundPatients with cirrhosis are at high risk of thrombotic events, including portal vein thrombosis and venous thromboembolism. In such patients, hypercoagulability is not detected by conventional coagulation tests, but only by the thrombin generation assay (TGA) that integrates the role of pro- and anticoagulant factors. However, TGA use to predict clinical events depends on thrombin generation variability over time. ObjectivesThe aim of this study was to compare TGA intraindividual variability over time in patients with cirrhosis and in healthy controls. MethodsBlood samples were prospectively collected from 34 healthy controls and 52 patients with cirrhosis at week 0 (inclusion), 6, and 12. TGA was performed with the calibrated automated thrombogram method, tissue factor (5 pM), phospholipids, and with and without thrombomodulin (4 nM) or activated protein C (1 nM). ResultsWhen TGA was performed with thrombomodulin, endogenous thrombin potential in patients with cirrhosis was higher compared with controls and increased with cirrhosis severity. Stability over time of all thrombin generation parameters was excellent in healthy controls, good in Child-Turcotte-Pugh (CTP)-A patients, and poor in CTP-B/C patients (severe cirrhosis). In CTP-B/C patients, the phenotype was more variable because one-third of patients switched to normal or hypercoagulability during the 3-month follow-up. ConclusionA study with longer monitoring is needed to correlate the hypercoagulable phenotype of patients with cirrhosis with the occurrence of thrombotic events.

Increased In Vivo Thrombin Generation in Patients with Localized Non-Small Cell Lung Cancer Unfit for Surgery.

Patients with lung cancer face a substantially increased risk of thromboembolic disease. Patients with localized non-small cell lung cancer (NSCLC) who are unfit for surgery due to age or comorbidity have additional thrombotic risk factors. Thus, we aimed to investigate markers of primary and secondary hemostasis, since this could assist in treatment decisions. We included 105 patients with localized NSCLC. Ex vivo thrombin generation was determined by calibrated automated thrombogram and in vivo thrombin generation was determined by measurement of thrombin-antithrombin complex (TAT) levels and prothrombin fragment F1 + 2 concentrations (F1 + 2). Platelet aggregation was investigated by impedance aggregometry. Healthy controls were used for comparison. TAT and F1 + 2 concentrations were significantly higher in NSCLC patients than in healthy controls (P < .001). The levels of ex vivo thrombin generation and platelet aggregation were not increased in the NSCLC patients. Patients with localized NSCLC considered unfit for surgery had significantly increased in vivo thrombin generation. This finding should be further investigated as it could be relevant for the choice of thromboprophylaxis in these patients.

IMPAIRED BALANCE OF CLOTTING FACTORS IN LIVER CIRRHOSIS

Liver cirrhosis (LC) has been accepted as prototype of a disease with acquired prohemorrhagic diathesis. However, as the synthesis of all coagulant factors is affected, a rebalanced but fragile hemostasis is maintained. With increasing disease severity, a disproportion between levels of certain coagulants occurs that can lead to prothrombotic tendency. We aimed to evaluate the levels of factor VIII (FVIII), protein C (PC) and their ratio (FVIII/PC) as the main determinants of thrombin generation in patients with LC at different stages of disease. Fifty patients with LC were divided in three groups according to LC severity using the Child-Turcotte-Pugh Score (CTP-A, CTP-B, CTP-C). The levels of FVIII and protein C were measured in sodium citrate plasma on Siemens, BCS XP Blood Coagulometer. The levels of FVIII, PC and FVIII/PC were compared between the groups and a correlation of their values to MELD score was performed. Plasma levels of FVIII increased with severity of the disease, with concurrent statistically significant decrease of plasma PC levels (p=0.0008). This was accompanied with statistically significant increase of the FVIII/PC ratio (p=0.0004) indicating hypercoagulable state in advanced stage of the disease. A significant correlation to MELD score was identified for PC in group CTP-B and CTP-C and for FVIII/PC ratio in group CTP-C. As liver cirrhosis severity increases, a disproportion in plasma levels of the most powerful determinants of thrombin generation occurs. This could be the explanation for the observed increased risk of venous thromboembolism in patients with liver cirrhosis.

Relationship between Molecular Profile and Platelet Function and Thrombin Generation in Patients with Essential Thrombocytemia

Relationship between Molecular Profile and Platelet Function and Thrombin Generation in Patients with Essential Thrombocytemia

Effect of invasive therapeutic coronary interventions on endothelial cell activation and thrombin generation in patients with chronic total coronary occlusion

BackgroundPercutaneous coronary intervention (PCI) is commonly used treatment for chronic total occlusion (CTO). PCI can be performed in two different ways using wire escalation (WE) or subintimal dissection and reentry (DR) technique. During both procedures patients are treated with anticoagulants, however a substantial activation of coagulation cascade is expected, which may affect clinical outcome. ObjectivesOur aim was to compare the impact of WE and DR techniques regarding endothelial cell activation and thrombin formation. MethodsFifty patients after CTO-PCI were enrolled into this study. Blood samples were obtained before PCI, at 48 h and 3–6 months after the intervention to measure soluble endothelium-specific markers and to investigate thrombin generation. ResultsTwenty-nine patients were treated with WE, 21 received DR. In the DR group, soluble VCAM-1 (vascular cell adhesion molecule-1) and ICAM-1 (intercellular cell adhesion molecule-1) concentrations were gradually elevated and remained significantly increased at 3–6 months (p = 0.006 and p = 0.037, respectively) compared to pre-PCI. Furthermore, significant decrease in lagtime (p = 0.004) and time to peak (p = 0.002) with a substantial increment in peak thrombin (p = 0.001) were observed in these patients. In contrast, no significant alteration was found in the WE cohort. Clinical complications (myocardial infarction, stroke, thrombosis, revascularization) did not occur in the first 9 months of follow-up period in either group. ConclusionAlthough DR intervention induces more thrombin generation with a larger degree of endothelium activation compared to WE, this technique does not cause more clinical complications.

T208 Thrombin generation in patients with inflammatory bowel disease

T208 Thrombin generation in patients with inflammatory bowel disease

Circulating microparticles and thrombin generation in patients with Chronic Lymphocytic Leukemia

Circulating microparticles and thrombin generation in patients with Chronic Lymphocytic Leukemia

Hemophilia: The Past, the Present, and the Future.

Hemophilia: The Past, the Present, and the Future.

Thrombin Generation in Patients with Severe Hemophilia A May Be Variable but Predictive of Response to Treatment

Introduction: Patients with severe hemophilia A (HA) may have variable bleeding phenotypes despite having equivalently low factor VIII (FVIII) levels of <1%. The basis for this heterogeneity in the clinical expression of severe hemophilia is poorly understood. Recent evidence indicates that global assays of coagulation may be better predictors of the coagulation capacity and hemostasis compared with traditional coagulation tests. Current prophylaxis goals in patients with hemophilia minimize time spent at baseline. Thus, we hypothesized that evaluating endogenous thrombin potential (ETP) at baseline, 10% and 40% FVIII correction levels would better reflect real-world scenarios and the effects of treatment.Our objective was to study thrombin generation (TG) parameters (ETP, peak thrombin and lag time) at baseline, 10% and 40% factor correction levels in patients with severe hemophilia A. Additionally we aimed to determine if the baseline TG parameters were predictive of response at the spiked levels .Methods: Our study was a single institution cross-sectional study. Patients were recruited from 4/28/2011 - 7/31/2014. A total of 123 patients with HA were recruited out of which 55 patients with severe HA without inhibitors were included in our study. Descriptive characteristics of the study population included in our study are described in Table 1. A hemophilia severity score (HSS) was calculated based on adjusted bleeding scores, factor scores and joint scores. Baseline plasma samples at trough FVIII were obtained from patients and thrombin generation was evaluated using a standard calibrated automated thrombogram (CAT). Full-length recombinant FVIII was added to trough patient plasma for final factor concentrations of 0.1 U/dl and 0.4 U/dl. Spearman's rank correlation coefficients were calculated and p values of <0.05 were considered statistically significant.Results: Samples from 55 patients with severe HA without inhibitors were evaluated. CAT mean lag times were 5.04 minutes (SD 1.92), 8.06 minutes (SD 10.0), 5.87 minutes (SD 4.38); mean ETPs were 485.4 nM/minute (SD 296.6), 822.9 nM/minute (SD 372.2), 1038 nM/minute (SD 254); and mean peak thrombin levels were 37.2 nM (SD 37.9), 77.7 nM (SD 45.9), 138.4 nM (SD 58.5) at baseline, 10% correction and 40% factor correction respectively. There were no significant correlations between HSS score and TG parameters at baseline, 10% or 40%. The correlations ranged from -0.15 to .012. Severe versus non-severe genotype and TG was analyzed in 47 participants in whom genotype status was recorded. In the 29 patients with severe genotypes (62%) there were no comparisons that were statistically significant. However, the peak thrombin generation at 40% correction trended towards significance with levels lower in the patients with severe as compared to those with non-severe genotypes (p=0.07). Additionally we evaluated if TG parameters at baseline were predictive of responses at 10% and 40% correction levels. Baseline ETP significantly predicted ETP with both 10% (p<0.001) and 40% correction (p=0.0018) levels. Baseline peak thrombin was a significant predictor of peak thrombin levels with 10% (p<0.001) and 40% correction (p<0.001). Lagtime at baseline was a significant predictor of lag time at 10% correction (p=0.008) but not 40% correction levels (p=0.737). (Figure 1)Conclusion: Our results confirm previous studies indicating variability in thrombin generation among patients with severe HA (FVIII<1%) at baseline as well as at different correction levels. Since phenotypic heterogeneity is observed in patients with severe HA, this may suggest that TG better correlates with bleeding severity as compared to factor levels. Even though the HSS scores do not correlate with TG parameters this may be reflective of the need for a more robust phenotypic score evaluating bleeding severity in patients with hemophilia. Additionally, baseline TG parameters appear to be responsive to treatment at 10% and 40% factor correction levels, suggesting that baseline measurements maybe sufficient to predict response. The introduction of continuous primary prophylaxis has dramatically changed the natural history of the disease as well as orthopedic status. Therefore, new criteria may be warranted to define the degree of clinical severity of hemophilia to improve patient management and healthcare costs. [Display omitted] DisclosuresDunn:World Federation of Hemophilia USA: Membership on an entity's Board of Directors or advisory committees; Shire: Consultancy, Other: Unrestricted educational grant, Research Funding; Octapharma: Other: Unrestricted educational grant; NovoNordisk: Other: Unrestricted educational grant; Kedrion: Other: Unrestricted educational grant; Biogen: Other: Unrestricted educational grant, Research Funding; CSL Behring: Consultancy, Other: Unrestricted educational grant; Bayer: Consultancy, Other: Unrestricted educational grant; Alnylam: Other: Unrestricted educational grant.

Plasma levels do not predict thrombin generation in patients taking direct oral anticoagulants.

The antithrombotic effect of direct oral anticoagulants (DOAC) in specific clinical scenarios is difficult to assess. This study aimed to evaluate the effect of DOAC on thrombin generation (TG) in relation to their plasma level. Eighty patients newly started on anticoagulation were included, 20 patients for each DOAC-apixaban, edoxaban, rivaroxaban, and dabigatran. Plasma was sampled before DOAC (baseline), at plasma peak time, 6 and 12hours after starting DOAC for quantification of drug levels and TG. The baseline TG before DOAC intake showed inter-individual variability. All DOACs significantly prolonged lag time (LT) and time to peak (TTP), but did not change endogenous thrombin potential (ETP). Anti-Xa inhibitors but not dabigatran reduced thrombin peak, but the effect of apixaban at plasma peak was less pronounced (factor 1.6). LT and TTP prolongation of dabigatran was lower compared to anti-Xa inhibitors. All DOACs showed a nonlinear dose-response relationship, with the greatest antithrombotic effect at lower DOAC plasma levels. The inhibition of TG parameters between baseline and peak was parallel between individual patients but the coefficient of variation of TG was lower compared to drug levels. The antithrombotic effect at DOAC peak plasma level measured by TG depends on the patient-specific baseline TG level and the drug-specific inhibition by the particular DOAC. Although peak plasma levels have a high variability, the variation of TG is lower compared to drug levels. Therefore, TG assays may be superior to plasma levels in the assessment of the intensity of anticoagulation.

Heparins have adequate ex vivo anticoagulant effects in hospitalized patients with cirrhosis

BackgroundPatients with cirrhosis are at risk of venous thromboembolism (VTE), but strategies for thromboprophylaxis have not been defined. Previous in vitro studies suggest an altered anticoagulant effect of heparins in patients with cirrhosis. ObjectivesTo assess the anticoagulant effects of prophylactic low‐molecular‐weight heparin (LMWH) or unfractionated heparin (UFH) doses in patients with cirrhosis in a real‐life clinical setting. MethodsWe studied patients with cirrhosis (n = 16) and acute‐on‐chronic liver failure (ACLF) (n = 14), and compared these with patients without underlying liver disease admitted to non‐liver general medical wards (n = 18) and non‐liver intensive care units (n = 14), respectively. Blood samples were taken before and 4 h after administration of the first dose of LMWH or UFH. We assessed hemostatic status using thrombin generation assays, thrombin‐antithrombin complexes (TAT), and conventional coagulation assays, and included healthy controls (n = 20) to establish reference values. Anti‐Xa activity was determined to estimate peak heparin levels. ResultsBaseline thrombin generation was similar among all cohorts and healthy controls despite alterations in conventional coagulation assays. On heparin, both absolute and proportional changes of thrombin generation were comparable between all four cohorts (−62% to −85%). TAT levels decreased in all cohorts apart from the ACLF cohort, but did not correlate with the proportional change in thrombin generation. Anti‐Xa activity correlated with the proportional change in thrombin generation in patients receiving LMWH, but not in patients receiving UFH. ConclusionsThese data suggest that current prophylactic heparin doses have comparable anticoagulant effects in patients with cirrhosis compared with patients without underlying liver disease.

Thrombin Generation in Chronic Liver Diseases-A Pilot Study.

The knowledge about coagulation disorders in patients with chronic liver disease changed in the last decade. The aim of this study was to analyze the parameters of thrombin generation in patients with chronic liver disease, as they are the most appropriate biomarkers to explore coagulation. (1) Background: The knowledge about coagulation disorders in patients with chronic liver disease changed in the last decade. The study of thrombin generation in patients with chronic liver disease provides a much more accurate assessment of the coagulation cascade; (2) Methods: This study is a prospective observational pilot study on hospitalized patients with chronic liver diseases that analyzed thrombin generation performed from their platelet-poor plasma versus that of control subjects. We analyzed a group of 59 patients with chronic liver disease and 62 control subjects; (3) Results: Thrombin generation was lower in hepatitis and cirrhosis patients compared to controls and decreases as the disease progressed. Lag time was higher in ethanolic etiology compared to the control group. Peak thrombin and endogenous thrombin potential were shorter in all etiologies when compared to the control group. The velocity index was significantly lower in HCV hepatopathies, ethanolic, and mixed etiology when compared with normal individuals; (4) Conclusions: Given the variability of thrombin generation in patients with chronic liver disease, its assay could serve to identify patients with high thrombotic and hemorrhagic risk and establish personalized conduct toward them.

Progress in the Development of Anti-tissue Factor Pathway Inhibitors for Haemophilia Management.

The unprecedented progress in addressing unmet needs in haemophilia care to date includes developing several novel therapies that rebalance haemostasis by restoring thrombin generation in patients with haemophilia A or B with and without inhibitors. These novel therapies are FVIII mimetics, antithrombin interference RNA therapy and several monoclonal antibodies directed against the tissue factor pathway inhibitor (anti-TFPI). In this review, we provide an update on the progress made in developing anti-TFPI therapie. Phase 1 data from the three anti-TFPI studies showed acceptable safety profiles, and currently, available phase 2 data are encouraging. While these data support these molecules' further development progression, there is uncertainty on several aspects of their evolution. Two of the three anti-TFPIs have shown drug-related thrombosis, with one study consequently terminated. None of the thrombotic events is predictable with current monitoring tools, and none correlate with known coagulation parameters. All three anti-TFPIs undergo target mediated drug disposition, which impacts the formulation of dosing regimen fo these therapies. They would require more frequent dosing than some of the extended half-life clotting factor products and antithrombin RNAi therapy. There is no assay to measure the TFPI as the physiological levels are very low, which makes monitoring the impact of the anti-TFPI a challenge. The anti-TFPIs have several advantages, including their bioavailability when administered subcutaneously, their stable pharmacokinetics and their ability to prevent bleeds in haemophilia A or B patients with and without inhibitors. Whether these advantages can be realized will depend on the outcome of the currently ongoing studies.

Abstract P683: Thrombin Generation in Plasma of Stroke Patients With Atrial Fibrillation

Background and Purpose: Thrombus formation is central to pathophysiology of stroke in patients with atrial fibrillation. Whether factors in plasma contribute to thrombus generation in patients with atrial fibrillation remains unclear. In this study we sought to determine whether plasma contributes to thrombin generation in patients with atrial fibrillation. Methods: There were 78 acute ischemic strokes with atrial fibrillation and 37 non-stroke controls. Plasma thrombin generation was measured by thrombin generation assay, resulting lag time, peak thrombin, time to peak and area under the curve was assessed. Thrombin generation capacity was compared in stroke patients with atrial fibrillation to non-stroke controls. The relationship to anticoagulation was assessed. In vitro, the effect of anticoagulation on plasma thrombin generation was determined. Results: Thrombin generation capacity was increased (shorter lag time and time to peak) in ischemic stroke patients with atrial fibrillation compared to non-stroke atrial-fibrillation controls (p&lt;0.05 and p&lt;0.01, respectively). Anticoagulation decreased plasma induced thrombin generation. Ischemic stroke patients with atrial fibrillation treated with anticoagulation (DOAC or warfarin) had lower plasma induced thrombin generation compared to atrial-fibrillation patients not on anticoagulation (p&lt;0.05). Thrombin generation by plasma could be further reduced by DOAC in an in-vitro assay. Conclusions: Stroke patients with atrial fibrillation have a higher plasma induced thrombin generation compared to atrial fibrillation controls. Factors in plasma such as leukocyte derived tissue factor likely contribute to thrombus formation in patients with atrial fibrillation. As such, components in plasma may represent new targets to reduce thrombus formation and stroke risk in patients with atrial fibrillation.