Elevated Factor VIII Levels Research Articles

Targeting an elevated FVIII level using personalized rurioctocog alfa pegol prophylaxis in specific patient populations with hemophilia A: post hoc subanalysis of the randomized, phase 3 PROPEL study.

The phase 3, prospective PROPEL study demonstrated that pharmacokinetic (PK)-guided prophylaxis targeting elevated factor VIII (FVIII) troughs in patients with hemophilia A resulted in lower annualized bleeding rates (ABRs) and a higher proportion of patients experiencing zero bleeds in the second 6 months of treatment when targeting a FVIII trough of 8-12% versus 1-3%. To investigate the benefit of PK-guided prophylaxis with rurioctocog alfa pegol targeting two FVIII trough levels in specific patient subgroups in a post hoc analysis using data from PROPEL. This is a post hoc analysis of data from the PROPEL study. The design and primary outcomes of the prospective, randomized PROPEL study (NCT02585960) have been reported previously. This post hoc analysis reports data stratified by FVIII half-life (t1/2), hemophilic arthropathy status, number of target joints at screening, previous treatment regimen, and ABR range in the 12 months before study entry. Targeting an elevated FVIII trough of 8-12% was associated with higher average FVIII levels over time, regardless of FVIII t1/2 at baseline. The decrease in total ABR between the 8-12% and 1-3% arms was greatest in patients with a FVIII t1/2 of 6 to <12 h (0.7 versus 3.5); a higher number of target joints, that is, at least four target joints, at baseline (0.2 versus 1.6); the presence of arthropathy (0.1 versus 1.7); and those previously treated on-demand (0.3 versus 1.8). These results support the feasibility of targeting elevated FVIII levels using personalized rurioctocog alfa pegol prophylaxis. These benefits may be especially important in patients with a short FVIII t1/2 and those receiving standard prophylaxis with frequent breakthrough bleeds, arthropathy, and target joints. ClinicalTrials.gov Identifier: NCT02585960; https://clinicaltrials.gov/ct2/show/NCT02585960.

Prolonged Elevations of Factor VIII and von Willebrand Factor Antigen After Multisystem Inflammatory Syndrome in Children.

Multisystem Inflammatory Syndrome in Children (MIS-C) is a late systemic inflammatory response to a recent mild or asymptomatic coronavirus disease of 2019 infection. The pathophysiology is incompletely understood but it often features significant coagulopathy along with cardiac and endothelial dysfunction. Endothelial inflammation has been primarily described in acute coronavirus disease of 2019 infection, with less characterization in MIS-C. Here we describe novel findings of nearly universal severe and prolonged factor VIII (FVIII) and von Willebrand factor antigen elevations in an institutional cohort of patients with MIS-C ages younger than or 21 years old (N=31). All patients had elevated acute phase reactants and D-dimer at presentation and met published criteria for MIS-C. FVIII was high at presentation in 97% of patients but continued to rise during the ensuing weeks of treatment to a mean 429%, peaking on median day 17 of illness as an outpatient. FVIII levels were >600% in multiple patients. von Willebrand factor antigen was measured less frequently but showed similar trends. These escalations occurred amidst resolving cardiac dysfunction and acute phase reactant normalization and despite patients receiving multimodal anti-inflammatory treatments and aspirin and enoxaparin thromboprophylaxis. No thrombotic events occurred. Endothelial dysfunction represented by very elevated FVIII levels may persist longer than other acute phase reactants may reflect.

Pseudo Heparin Resistance After Pulmonary Endarterectomy: Role of Thrombus Production of Factor VIII

Pulmonary endarterectomy (PEA) is the main treatment for chronic thromboembolic pulmonary hypertension (CTEPH). Postoperative unfractionated heparin dosing can be monitored by activated partial thromboplastin time (APTT) or by anti-factor Xa activity (anti-Xa). In pseudo heparin resistance, APTT response to heparin is blunted due to elevated Factor VIII (FVIII) which can underestimate anticoagulation. We examined possible pseudo heparin resistance after PEA and assessed the impact of FVIII. APTT response to heparin before and after operation was determined in 13 PEA patients anticoagulated with unfractionated heparin. APTT and anti-Xa concordance was analyzed from paired postoperative samples, and antithrombin, fibrinogen and FVIII levels were measured. Single-cell RNA sequencing was used to characterize FVIII gene expression in PEA specimens of 5 patients. APTT response to heparin was blunted after PEA. APTT and anti-Xa were discordant in 36% of postoperative samples and most common discordant patterns were subtherapeutic APTT with therapeutic (16%) or supratherapeutic (11%) anti-Xa. Overall, APTT underestimated anticoagulation relative to anti-Xa in one-third of the samples. FVIII levels were elevated before surgery, increased substantially 1 and 3 days (median 4.32 IU/mL) after PEA, and were higher in discordant than concordant samples. Single-cell RNA sequencing showed FVIII gene expression in PEA specimen endothelial cells. Pseudo heparin resistance is common after PEA likely due to highly elevated postoperative FVIII levels indicating that anti-Xa reflects postoperative heparinization better than APTT in these patients. FVIII production by the pulmonary artery endothelium may participate in local prothrombotic processes important for CTEPH pathogenesis.

Partial F8 gene duplication (factor VIII Padua) associated with high factor VIII levels and familial thrombophilia

AbstractHigh coagulation factor VIII (FVIII) levels comprise a common risk factor for venous thromboembolism (VTE), but the underlying genetic determinants are largely unknown. We investigated the molecular bases of high FVIII levels in 2 Italian families with severe thrombophilia. The proband of the first family had a history of recurrent VTE before age 50 years, with extremely and persistently elevated FVIII antigen and activity levels (>400%) as the only thrombophilic defects. Genetic analysis revealed a 23.4-kb tandem duplication of the proximal portion of the F8 gene (promoter, exon 1, and a large part of intron 1), which cosegregated with high FVIII levels in the family and was absent in 103 normal controls. Targeted screening of 50 unrelated VTE patients with FVIII levels ≥250% identified a second thrombophilic family with the same F8 rearrangement on the same genetic background, suggesting a founder effect. Carriers of the duplication from both families showed a twofold or greater upregulation of F8 messenger RNA, consistent with the presence of open chromatin signatures and enhancer elements within the duplicated region. Testing of these sequences in a luciferase reporter assay pinpointed a 927-bp region of F8 intron 1 associated with >45-fold increased reporter activity in endothelial cells, potentially mediating the F8 transcriptional enhancement observed in carriers of the duplication. In summary, we report the first thrombophilic defect in the F8 gene (designated FVIII Padua) associated with markedly elevated FVIII levels and severe thrombophilia in 2 Italian families.

Premature Myocardial Infarction as the Presenting Sign of Hypercoagulable Syndrome

Introduction Premature myocardial infarction (MI) in a young patient proves to be a challenge to manage. In the absence of family history or provoking factors, etiology can be difficult to determine. Hypercoagulable syndromes should be considered as an etiology for premature MI, as future management may be influenced by the presence of these syndromes. We report the case of a young heart-kidney transplant recipient presenting with multiple thrombotic events including premature MI, LVAD thrombosis, and deep vein thrombosis (DVT) in the setting of May-Thurner Syndrome (MTS) exemplifying the importance of thorough hypercoagulability testing. Case Report Our patient is a 41-year-old male with a history of MI at age 37, resulting in ischemic cardiomyopathy complicated by cardiogenic shock requiring LVAD placement for bridge to transplant. Patient's post LVAD course was complicated by recurrent LVAD thrombosis despite adequate anticoagulation (AC) requiring two device exchanges. Hypercoagulability testing was limited due to the necessity of chronic AC. One month after undergoing heart-kidney transplant, patient presented with left lower extremity (LLE) pain and difficulty ambulating with duplex ultrasound showing DVT of LLE extending from the L common iliac vein to the L popliteal vein, requiring thrombectomy. Venography identified narrowing of the L common iliac vein confirming the diagnosis of MTS and an iliac vein stent was placed. Repeat hypercoagulability testing revealed an elevated factor VIII (FVIII) activity level to 319% of normal, warranting long-term AC with an elevated therapeutic INR range and high dose aspirin. Patient has had no recurrent thrombosis since starting this regimen. Summary Patients with multiple thrombotic events should undergo thorough hypercoagulability testing to identify risk for future thromboses and need for AC. Traditionally, elevated FVIII levels are thought to be an acute phase reactant, not necessitating AC. However, it has recently been shown that patients with an elevated FVIII level are at significant risk for thrombosis and require long-term AC. Our case highlights the importance of early FVIII level testing in hypercoagulability evaluation.

Common VWF sequence variants associated with higher VWF and FVIII are less frequent in subjects diagnosed with type 1 VWD

Unlabelled Box BackgroundGenetic variation in the VWF gene is associated with von Willebrand factor (VWF) and factor VIII (FVIII) levels in healthy individuals. ObjectivesWe hypothesized that VWF sequence variants associated with higher VWF or FVIII could impact the diagnosis of type 1 von Willebrand disease (VWD). MethodsWe examined VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), VWF propeptide (VWFpp), and FVIII levels along with VWF gene sequencing in 256 healthy control and 97 type 1 VWD subjects as part of a cross‐sectional study. ResultsWe found several VWF sequence variants (VWF c.2880G>A and VWF c.2365A>G(;)c.2385T>C, found in linkage disequilibrium) associated with higher VWF and FVIII levels in healthy controls (P<.001 for both variants). In addition, these variants were significantly more common in controls than in subjects diagnosed with type 1 VWD and VWF:Ag <30 (P<.005). The decreased variant frequencies in type 1 VWD was not seen in other VWD types. VWF:Ag, VWF:RCo, and FVIII were not statistically different in type 1 VWD subjects who had these VWF variants compared to type 1 VWD patients without them. There was no difference in ABO blood group, VWF propeptide levels (excluding subjects with known VWF clearance defects), or bleeding score using the ISTH bleeding assessment tool. ConclusionsThese data suggest that certain VWF sequence variants associated with elevated FVIII and VWF levels may protect against reduced VWF levels. These findings were independent of other pathogenic sequence variants in VWF, suggesting a possible independent effect of c.2880G>A and c.2365A>G(;)c.2385T>C on VWF levels.

Elevated Factor VIII and von Willebrand Factor Levels Predict Unfavorable Outcome in Stroke Patients Treated with Intravenous Thrombolysis.

Plasma factor VIII (FVIII) and von Willebrand factor (VWF) levels have been associated with the rate and severity of arterial thrombus formation and have been linked to outcomes following thrombolytic therapy in acute myocardial infarction patients. Here, we aimed to investigate FVIII and VWF levels during the course of thrombolysis in acute ischemic stroke (AIS) patients and to find out whether they predict long-term outcomes. Study population included 131 consecutive AIS patients (median age: 69 years, 60.3% men) who underwent i.v. thrombolysis with recombinant tissue plasminogen activator (rt-PA). Blood samples were taken on admission, 1 and 24 h after rt-PA administration to measure FVIII activity and VWF antigen levels. Neurological deficit of patients was determined according to the National Institutes of Health Stroke Scale (NIHSS). ASPECT scores were assessed using computer tomography images taken before and 24 h after thrombolysis. Intracranial hemorrhage was classified according to the European Cooperative Acute Stroke Study (ECASS) II criteria. Long-term functional outcome was determined at 90 days after the event by the modified Rankin scale (mRS). VWF levels on admission were significantly elevated in case of more severe AIS [median and IQR values: NIHSS <6:189.6% (151.9-233.2%); NIHSS 6-16: 199.6% (176.4-250.8%); NIHSS >16: 247.8% (199.9-353.8%), p = 0.013]; similar, but non-significant trend was observed for FVIII levels. FVIII and VWF levels correlated well on admission (r = 0.748, p < 0.001) but no significant correlation was found immediately after thrombolysis (r = 0.093, p = 0.299), most probably due to plasmin-mediated FVIII degradation. VWF levels at all investigated occasions and FVIII activity before and 24 h after thrombolysis were associated with worse 24 h post-lysis ASPECT scores. In a binary backward logistic regression analysis including age, gender, high-sensitivity C-reactive protein, active smoking, diabetes, and NIHSS >5 on admission, elevated FVIII and VWF levels after thrombolysis were independently associated with poor functional outcomes (mRS ≥ 3) at 90 days (immediately after thrombolysis: FVIII: OR: 7.10, 95% CI: 1.77-28.38, p = 0.006, VWF: OR: 6.31, 95% CI: 1.83-21.73, p = 0.003; 24 h after thrombolysis: FVIII: OR: 4.67, 95% CI: 1.42-15.38, p = 0.011, VWF: OR: 19.02, 95% CI: 1.94-186.99, p = 0.012). Elevated FVIII activity and VWF antigen levels immediately after lysis and at 24 h post-therapy were shown to have independent prognostic values regarding poor functional outcomes at 90 days.

Coagulation factor VIII, IX and XI levels in north Indian patients with venous thromboembolism

Studies have shown elevated levels of certain coagulation factors as risk factors for venous thromboembolism (VTE). In this study, we investigated the levels of coagulation factor VIII (FVIII), FIX and FXI in north Indian patients with VTE. A total of 123 patients with VTE were screened prospectively for FVIII, FIX and FXI levels and the conventional risk factors - deficiencies of protein C, S and antithrombin, positivity for antiphospholipid antibodies and the factor V Leiden mutation. Age-matched and sex-matched controls were included. VTE was secondary to known circumstantial and thrombophilic risk factors in 66 (53.7%) patients. In 46.3% (idiopathic VTE) patients, no cause was identified. The mean FVIII levels in idiopathic (187 IU/dl) and secondary VTE patients (185.4 IU/dl) were significantly higher compared with controls (129.6 IU/dl; P < 0.001). However, there was no statistically significant difference in the levels of FIX and FXI between patients and controls (P = 0.214 and 0.198, respectively). Patients with elevated FVIII levels had increased risk of VTE compared with controls (odds ratio: 9.4, 95% confidence interval: 4.7-18.79). On logistic regression analysis after adjusting for surgery and presence of antiphospholipid antibodies, this risk remained unchanged (odds ratio: 9.54, 95% confidence interval: 4.68-19.44). A dose-response relationship was observed with progressive increase in FVIII levels. Elevated FVIII levels constitute an independent risk factor for VTE in the north Indian population. Elevated levels of FIX and FXI were not associated with increased risk of VTE.

Profile of Patients with Thrombosis Evaulauted in a Tertiary Care Centre

A delicate balance exists between fibrin formation and fibrinolysis in vivo. Reduced blood flow, changes in the vessel wall and changes in blood composition result in disturbance of this balance, which favors fibrin formation and ultimately lead to formation of occlusive thrombi. Venous and arterial thrombosis are common diseases with an estimated incidence of 1 in 1000 individuals per year50 .Despite the growing insight in the pathogenesis of thrombophilia, the cause of many thrombotic episodes remain unknown. Although the causes are not always identified, several risk factors have been studied and it was observed that hypercoagulability is one of the triggers that alters the hemostasis. Hypercoagulability may occur due to defective naturally occurring anticoagulant mechanisms or due to heightened levels of procoagulant factors. Several risk factors have been identified like increased levels of coagulation factors-factor VIII, IX, XI, II and fibrinogen which are cumulatively explored by activated partial thromboplastin time used over the last 50 years as a standard screening test in clinical laboratories throughout the world. Several groups have identified elevated levels of factor VIII as an independent risk. The present study was aimed at examining risk factors involved in the pathogenesis of thrombosis in the Indian population. Review of literature has shown that most of the epidemiology studies to date with reference to thrombophilias, are confined to data derived from the European population. This study was done on 310 patients who presented with different thrombotic disorders. While the clinical utility of diagnostic testing for an inherited or acquired thrombophilia remains controversial, studies such as these hold the potential of further stratifying individual patients into high- and low-risk for incident and recurrent VTE. This in turn will help target prophylaxis to those who benefit the most and ultimately reduce the occurrence of venous thromboembolism. The commonest risk factor identified was increased Factor VIII:C levels, followed by antiphospholipid antibody and shortened activated partial thromboplastin time. Two hemolytic anemias – one genetic (sickle cell anemia) and the other an acquired membrane disorder (paroxysmal nocturnal hemoglobinuria) were also found to be associated with a tendency to thrombosis. 50% of the patients in this study who presented with thrombosis had no identifiable risk factors.

A Model for Predicting Persistent Elevation of Factor VIII among Patients with Acute Ischemic Stroke

Elevated levels of coagulation factor VIII (FVIII) may persist independent of the acute-phase response; however, this relationship has not been investigated relative to acute ischemic stroke (AIS). We examined the frequency and predictors of persistently elevated FVIII in AIS patients. AIS patients admitted between July 2008 and May 2014 with elevated baseline FVIII levels and repeat FVIII levels drawn for more than 7 days postdischarge were included. The patients were dichotomized by repeat FVIII level for univariate analysis at 150% and 200% activity thresholds. An adjusted model was developed to predict the likelihood of persistently elevated FVIII levels. Among 1616 AIS cases, 98 patients with elevated baseline FVIII had repeat FVIII levels. Persistent FVIII elevation was found in more than 75% of patients. At the 150% threshold, the prediction score ranged from 0 to 7 and included black race, female sex, prior stroke, hyperlipidemia, smoking, baseline FVIII > 200%, and baseline von Willebrand factor (vWF) level greater than 200%. At the 200% threshold, the prediction score ranged from 0-5 and included female sex, prior stroke, diabetes mellitus, baseline FVIII level greater 200%, and baseline vWF level greater than 200%. For each 1-point increase in score, the odds of persistent FVIII at both the 150% threshold (odds ratio [OR] = 10.4, 95% confidence interval [CI] 1.63-66.9, P = .0134) and 200% threshold (OR = 10.2, 95% CI 1.82-57.5, P = .0083) increased 10 times. Because an elevated FVIII level confers increased stroke risk, our model for anticipating a persistently elevated FVIII level may identify patients at high risk for recurrent stroke. FVIII may be a target for secondary stroke prevention.

Elevated levels of factor VIII and subsequent risk of all‐cause mortality: results from the MEGA follow‐up study

Factor VIII (FVIII) levels are increased in individuals with a non-O blood group and play a role in the etiology of thrombosis. High FVIII levels have also been associated with increased all-cause mortality. We explored whether elevated FVIII levels are associated with an increased risk of death in patients who had venous thrombosis and in individuals from the general population, and to what extent this association is causal. We followed 2178 patients with previous venous thrombosis and 2827 age and sex-matched community controls for on average 5.5years and measured their FVIII levels and ABO blood group. All-cause mortality increased in a dose-response fashion with increasing percentiles of FVIII levels. In the thrombosis patients the risk was highest above the 97.5th percentile (FVIII>199IUdL(-1) ) with an adjusted hazard ratio (HR) of 3.1 (95% confidence interval [CI], 0.9-10.8) as compared with patients in the 25th percentile category (FVIII≤85IUdL(-1) ). The adjusted HR was 4.5 (95% CI, 1.4-14.3) in controls. Using non-O blood group as a measure of genetically elevated FVIII levels to determine a causal relationship between FVIII and death showed observed HRs of 0.99 (95% CI, 0.72-1.36) in patients and 1.25 (95% CI, 0.82-1.90) in controls. We showed a dose-response relationship between high FVIII levels and risk of death in venous thrombosis patients and in individuals from the general population. However, environmental factors, such as chronic comorbidities and chronic inflammation, are at least in part responsible for the association between factor VIII and mortality.

Utility of a high VWF: FVIII ratio in preventing FVIII accumulation: a study in VWF-deficient mice.

Treatment of von Willebrand disease typically requires multiple infusions of von Willebrand factor (VWF)/factor VIII (FVIII) concentrate. Accumulation of FVIII is a clinical concern due to potential risk for thromboembolism. This study sought to determine whether VWF/FVIII concentrate of high VWF:FVIII ratio can prevent FVIII accumulation. VWF-deficient knockout mice received four 150 IU/kg VWF:ristocetin cofactor (RCo) infusions at 3-h intervals, with VWF/FVIII concentrates of a high (Haemate P/Humate-P) or low (Wilate) VWF:FVIII ratio. After each infusion, trough FVIII and VWF levels in plasma were determined. Separately, pharmacokinetic analysis was performed after single 250-IU/kg VWF:RCo infusions of each concentrate. Over the course of the four infusions, trough FVIII increased significantly in the group receiving Wilate (P < 0.001), but not Haemate P/Humate P (P = 0.058). After the first infusion, mean trough FVIII level in the Wilate group (31.7 IU/dl) was greater by 82% (P = 0.017) than that in the Haemate P/Humate P group (17.4 IU/dl). After the final infusion, mean trough FVIII of animals receiving Wilate (55.1 IU/dl) continued to exceed that of Haemate P/Humate P recipients (30.2 IU/dl) significantly (P < 0.001). Trough VWF levels were similar in the two groups. The VWF pharmacokinetics of the two concentrates coincided closely; however, the FVIII peak concentration and area under the curve were approximately twice as great in the mice treated with Wilate. In a murine model of severe von Willebrand disease, a VWF/FVIII concentrate with a high VWF:FVIII ratio prevented persistent exposure to elevated trough FVIII levels.

Abstract T P190: A Model for Predicting Persistent Elevation of Factor VIII Among Patients with Acute Ischemic Stroke (AIS)

Background and Purpose: Recent studies have demonstrated that elevated levels of coagulation factor VIII (FVIII), a risk factor for stroke, may persist independent of the acute-phase response; however, this relationship has not yet been investigated in the context of acute ischemic stroke (AIS). We sought to determine 1) the proportion of AIS patients with acutely elevated serum FVIII levels who had persistently elevated FVIII levels in the outpatient setting and 2) the characteristics at baseline predictive of persistently elevated FVIII levels. Methods: From our stroke registry, patients diagnosed with AIS between 07/2008-05/2014 were included if the initial FVIII level was elevated and a repeat FVIII level was obtained. A score was developed to predict which patients are at the greatest odds of remaining persistently elevated at both the 150% and 200% thresholds. Results: Among 1,616 AIS cases, 106 patients had initially elevated FVIII levels and repeat FVIII levels obtained. A total of 82.7% of patients had persistent elevation at the 150% threshold and 75.7% had persistent elevation at the 200% threshold. Time from initial FVIII measurement to second FVIII measurement was not different between the two groups (p=0.054). According to the models developed, for every one-point increase in the score, an individual is at ten-fold increased odds to have persistently elevated FVIII at both the 150% threshold (OR=10.43, 95% CI 1.63-66.9, p=0.0134) and 200% threshold (OR=10.2, 95% CI 1.82-57.5, p=0.0083). Conclusions: Persistent elevation in FVIII is common and in most AIS patients likely represents a constitutional risk factor. Persistent elevation in FVIII can be predicted by baseline characteristics in the setting of AIS, potentially proving useful in identifying patients at high risk for developing subsequent stroke.

New Thrombotic Events in Ischemic Stroke Patients with Elevated Factor VIII.

Background. Heightened levels of Factor VIII (FVIII) have been associated with both arterial and venous thrombosis. While elevated FVIII is common during acute ischemic stroke (AIS), whether elevated FVIII confers an increased risk for recurrent thrombotic events (RTEs) following AIS has not been previously explored. Methods. Consecutive AIS patients who presented to our center between July 2008 and September 2013 and had FVIII measured during admission were identified from our stroke registry. Baseline characteristics and the occurrence of RTE (recurrent or progressive ischemic stroke, DVT/PE, and MI) were compared in patients with and without elevated FVIII levels. Results. Of the 298 patients included, 203 (68.1%) had elevated FVIII levels. Patients with elevated FVIII had higher rates of any in-hospital RTE (18.7% versus 8.4%, P = 0.0218). This association remained after adjustment for baseline stroke severity and etiology (OR 1.01, 95% CI 1.00–1.01, P = 0.0013). Rates of major disability were also higher in patients who experienced a RTE (17.8% versus 3.2%, P < 0.0001). Conclusion. A significantly higher frequency of in-hospital RTEs occurred in AIS patients with elevated FVIII. The occurrence of such events was associated with higher morbidity. Further study is indicated to evaluate whether FVIII is a candidate biomarker for increased risk of RTEs following AIS.

A von Willebrand factor fragment containing the D′D3 domains is sufficient to stabilize coagulation factor VIII in mice

AbstractPlasma factor VIII (FVIII) and von Willebrand factor (VWF) circulate together as a complex. We identify VWF fragments sufficient for FVIII stabilization in vivo and show that hepatic expression of the VWF D′D3 domains (S764-P1247), either as a monomer or a dimer, is sufficient to raise FVIII levels in Vwf−/− mice from a baseline of ∼5% to 10%, to ∼50% to 100%. These results demonstrate that a fragment containing only ∼20% of the VWF sequence is sufficient to support FVIII stability in vivo. Expression of the VWF D′D3 fragment fused at its C terminus to the Fc segment of immunoglobulin G1 results in markedly enhanced survival in the circulation (t1/2 > 7 days), concomitant with elevated plasma FVIII levels (>25% at 7 days) in Vwf−/− mice. Although the VWF D′D3-Fc chimera also exhibits markedly prolonged survival when transfused into FVIII-deficient mice, the cotransfused FVIII is rapidly cleared. Kinetic binding studies show that VWF propeptide processing of VWF D′D3 fragments is required for optimal FVIII affinity. The reduced affinity of VWF D′D3 and VWF D′D3-Fc for FVIII suggests that the shortened FVIII survival in FVIII-deficient mice transfused with FVIII and VWF D′D3/D′D3-Fc is due to ineffective competition of these fragments with endogenous VWF for FVIII binding.

Abstract T MP74: The Effect of Elevated Factor VIII on Glycemic Control in Acute Ischemic Stroke Patients

Background: Elevated Factor VIII (FVIII) levels are associated with diabetes mellitus (DM) and hyperglycemia and are common in acute ischemic stroke (AIS). We sought to investigate if elevated FVIII would be associated with insulin administration during hospitalization for AIS. Methods: We retrospectively analyzed 219 patients who presented to our center from 07/2008-12/2012 with AIS. Cases were grouped by peristroke FVIII levels (normal: 50-150%; elevated: &gt;150 %;), with a priori subgroup analysis restricted to those with severely elevated FVIII &gt;200%. Per standard orders, glucose is measured at least every 6hrs during the first 48hrs and is treated when &gt;160mg/dl with sliding scale insulin. The odds ratios of receiving various forms of insulin were calculated using logistic regression in four sequentially adjusted models: (1) unadjusted, (2) demographics, (3) added baseline NIHSS and admission glucose and (4) added variables significant in univariate analysis. Results: Patients with elevated FVIII (n=143) were more likely Black, have a history of diabetes and have higher serum glucose and HbA1C’s on admission. Patients with elevated FVIII received more insulin/day than patients with normal FVIII (median 0.71 units vs 0 units, respectively, p=0.0014). In fully adjusted models, insulin use did not differ between normal or elevated FVIII levels. Patients with severely elevated FVIII, however, were 16 times more likely to receive intermediate/long acting insulin to treat hyperglycemia, compared to those with normal FVIII. The presence of severely elevated FVIII elevations did not predict insulin requirements in adjusted models. Conclusion: Our results further support a relationship between FVIII and elevated glucose, particularly in the setting of AIS when hyperglycemia is predictive of poor outcome. Further study is needed to investigate if elevated FVIII levels drive or simply reflect hyperglycemia and may help guide glycemic management in AIS patients.

Elevated plasma factor VIII enhances venous thrombus formation in rabbits: Contribution of factor XI, von Willebrand factor and tissue factor

Elevated plasma levels of factor VIII (FVIII) are associated with increased risk of deep venous thrombosis. The aim of this study is to elucidate how elevated FVIII levels affect venous thrombus formation and propagation in vivo. We examined rabbit plasma FVIII activity, plasma thrombin generation, whole blood coagulation, platelet aggregation and venous wall thrombogenicity before and one hour after an intravenous infusion of recombinant human FVIII (rFVIII). Venous thrombus induced by the endothelial denudation of rabbit jugular veins was histologically assessed. Thrombus propagation was evaluated as indocyanine green fluorescence intensity. Argatroban, a thrombin inhibitor, and neutralised antibodies for tissue factor (TF), factor XI (FXI), and von Willebrand factor (VWF) were infused before or after thrombus induction to investigate their effects on venous thrombus formation or propagation. Recombinant FVIII (100 IU/kg) increased rabbit plasma FVIII activity two-fold and significantly enhanced whole blood coagulation and total plasma thrombin generation, but did not affect initial thrombin generation time, platelet aggregation and venous wall thrombogenicity. The rFVIII infusion also increased the size of venous thrombus 1 hour after thrombus induction. Argatroban and the antibodies for TF, FXI or VWF inhibited such enhanced thrombus formation and all except TF suppressed thrombus propagation. In conclusion, elevated plasma FVIII levels enhance venous thrombus formation and propagation. Excess thrombin generation by FXI and VWF-mediated FVIII recruitment appear to contribute to the growth of FVIII-driven venous thrombus.

Ibrutinib (PCI 32765) Rapidly Improves Platelet Counts in Chronic Lymphocytic Leukemia / Small Lymphocytic Lymphoma (CLL/SLL) Patients and Has Minimal Effects On Platelet Aggregation

AbstractAbstract 1789 INTRODUCTION:Ibrutinib (PCI 32765) is an orally administered covalent inhibitor of Bruton's Tyrosine Kinase (BTK). Ibrutinib has significant activity in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and is typically well tolerated (Byrd ASCO 2011, O'Brien ASH 2011). Rarely serious bleeding in patients concurrently on oral anticoagulation has been reported but was not related to thrombocytopenia (O'Brien ASH 2011). However, grade 1 or 2 ecchymosis/contusion is a frequent adverse event in patients on ibrutinib. In addition to being essential for B cell receptor signaling BTK is also involved in the signaling of the glycoprotein (GP)VI and GPIV von Willebrand (vW) receptors (Liu, Blood 2006). Thus, it is possible that ibrutinib could increase the bleeding risk by interfering with thrombus formation. In addition, lymphoproliferative disorders and some drugs have been associated with acquired vW-disease (AvWD). METHODS AND PATIENTS:In an ongoing single center, open label phase II trial we treat CLL/SLL patients with ibrutinib 420 mg daily on 28 day cycles (NCT01500733). We measured platelet (PLT) function on the PFA-100 instrument, vW-factor (vWF) antigen levels and activity (vWF-Ag/vWF-Act), and factor VIII (FVIII) on baseline, days 2 and 28. Here we report on effects of ibrutinib on platelet counts and function in 25 patients who completed >2 cycles. RESULTS:PLT counts prior to treatment ranged from 36 k/μl to 256 k/μl with a median of 102 k/μl. Twelve (48%) patients had a pre-treatment PLT count <100 k/μl. Median PLT counts for days 14, 28, and 56 increased to 140, 137, and 135 k/μl, respectively (P<.01). 76% of patients showed an increase after only 2 weeks on drug (median increase 25 k/μl (range 4–183 k/μl) that was sustained at subsequent timepoints. On day 14, 6 patients (24%) had a decrease in PLT count by a median of 13 k/μl from baseline; of these, 3 had a pre-treatment PLT count of <100 k/ul and 1 developed grade III thrombocytopenia (42 k/μl) that resolved to >100 k/μl by day 56. 20% (5 of 25) of patients reported grade 1 spontaneous ecchymosis with no correlation to platelet count, PFA testing, or vWF measurements. Of note we performed lymph node core biopsies in 35 patients taking ibrutinib with minimal bruising. Only 2 patients had more extensive local bruising/ecchymosis at the biopsy site.Test (normal range)baselineday 2day 28PLT count (161-347 k/μl)102140137PFA-100 EPI (86-154 sec)109110110PFA-100 ADP (73-129 sec)747979vWF-ACT (52-156 IU/dL)182nd99vWF-AG (50-197 IU/dL)158nd101FVIII (41-184 IU/dL)181nd157All values are median, nd = not doneIn 19 patients PFA-100 measurements of epinephrine (EPI) and adenosine diphosphate (ADP) stimulated platelet aggregation times were available (test requires PLT count >100 k/μl). Median changes in closure times with EPI and ADP on treatment were not significantly different from baseline (See table). Four (21%) patients started with abnormally prolonged EPI closure times (one on aspirin, one on ibuprofen; discontinued with the start of ibrutinib) which resolved by day 28 in 3 and decreased in 1. Three (16%) patients had a prolongation of EPI closure times on day 2 that resolved by day 28 in 2 and decreased in 1. All closure times on ADP were low or normal. No patients with abnormal PFA testing demonstrated spontaneous ecchymosis. From baseline to day 28 vWF-Act, vWF-Ag and FVIII decreased (P<0.05; n=24). All 3 values were high normal to elevated prior to treatment and decreased to normal on treatment. CONCLUSION:This preliminary report does not identify any significant ibrutinib effect on platelet function. PLT counts improved rapidly in the majority of patients and when seen transient decreases have been minimal. Three patients (16%) developed an abnormal reading in PLT function tests on treatment but none developed spontaneous echymosis or bleeding. The observed normalization of mildly elevated baseline levels of vWF and FVIII seems most consistent with a reduction in acute phase reactants and there was no evidence for AvWD on ibrutinib. The apparent functional tolerance of BTK inhibition in platelets is likely attributable to redundancy in the affected signaling pathways.This work was supported by the Intramural Research Program of NHLBI, NIH. We thank our patients for participating in these research studies. Disclosures:No relevant conflicts of interest to declare.

Elevated factor VIII levels and risk of venous thrombosis

Modern thrombophilia testing fails to identify any underlying prothrombotic tendency in a significant number of patients presenting with objectively confirmed venous thromboemboembolism (VTE). This observation has led to a search for other novel inherited or acquired human thrombophilias. Although a number of putative mechanisms have been described, the evidence behind many of these candidates remains weak. In contrast, an increasing body of work supports the hypothesis that increased plasma factor VIII (FVIII) levels may be important in this context. An association between elevated plasma FVIII levels and VTE was first described in the Leiden Thrombophilia Study (LETS). Subsequently, these conclusions have been supported by an increasing number of independent case-control studies. Cumulatively, these studies have clearly demonstrated that high FVIII levels constitute a prevalent, dose-dependent risk factor for VTE. Furthermore, more recent studies have shown that the risk of recurrent venous thrombosis is also significantly increased in patients with high FVIII levels. In this review, we present the evidence supporting the hypothesis that elevated FVIII levels constitute a clinically important thrombophilia. In addition, we examine the biological mechanisms that may underlie persistently elevated FVIII levels, and the pathways through which high FVIII may serve to increase thrombotic risk.

Is coagulation factor VIII a useful marker for colorectal carcinoma?

Increased thromboembolic events are well known in patients suffering from malignant diseases. In the following pilot study, we investigated the usefulness of coagulation factor VIII (FVIII) as a possible prognostic marker in patients with colorectal carcinoma (CRC). Plasma FVIII levels were measured in 79 patients with CRC, correlated with tumor characteristics, and compared with normal ranges of blood group (BG) 0 and BG A/AB/B and with 19 control patients. In CRC patients mean FVIII levels were elevated compared with controls (BG 0: p=0.283, BG A/AB/B: p=0.001) and normal ranges. Interestingly, mean FVIII levels varied significantly in different blood groups (p=0.002). UICC stage I CRC patients presented with mean FVIII plasma levels within normal ranges, whereas UICC stage II-IV CRC patients presented with elevated FVIII plasma levels. In BG A/AB/B a significantly elevated FVIII level was found in G2 compared with G1 tumors (p< 0.001). Patients with elevated carcinoembryonic antigen also showed significantly elevated FVIII levels (p=0.050). FVIII levels at time of surgery did not correlate with survival within the first 2 years following surgery. In this pilot study, we demonstrated that FVIII plasma levels are elevated in patients with CRC and affected by T-stage and differentiation of the tumor. Whether FVIII is a clinical useful marker needs to be tested in a larger cohort.