The Low Von Willebrand Factor in Ireland Cohort Study - Defining Optimal Management for Procedures in Patients with Low VWF (30-50 IU/dL)

Abstract Recent international consensus guidelines recommend that patients with significant bleeding phenotypes and plasma VWF levels in the 30-50 IU/dL range should be classified as Low von Willebrand factor (Low VWF). Critically however, evidence-based guidelines regarding optimal clinical management strategies for this cohort have not been defined. In particular, data regarding the need for hemostatic cover for procedures in Low VWF are limited. To address this deficit, as part of the Low Von Willebrand in Ireland Cohort (LoVIC) study we conducted a systematic retrospective review of all procedures in a large cohort of well characterised patients with Low VWF. Methods: Following written informed consent, we collated data on all procedures performed in LoVIC patients over a 17 year period (1/1/00-12/31/17). Case notes were reviewed and data collected in a standard proforma - age at intervention, choice of hemostatic cover, perioperative VWF, haemoglobin (Hgb) levels and reported bleeding. Procedures were categorised as dental extractions (DE), minor (e.g. endoscopies, joint injections) or major surgery. Tranexamic acid (TA) was prescribed 1g TDS. All desmopressin (DDAVP) was administered intravenously (IV, 0.3mg/kg). Results: 165 procedures in 65 LoVIC participants were identified. The procedural group was significantly older (median 45 vs 38.8 years, p<0.0001) and with a longer duration of Low VWF (9.0 vs 6.5 years, p=0.02) compared to the rest of the cohort. The majority of procedures were either minor (69.1%) or DEs (24.2%), with only 11 major procedures. Overall, 41 (24.8%) were covered with TA alone; 103 (62.4%) with DDAVP+/- TA; clotting factor concentrate (CFC) was used in only 4 procedures. Dental extractions: DDAVP+/-TA was used in 72.5% of DEs with no excess bleeding. Of the 10 DE with only TA, 4 developed bleeding requiring treatment (DDAVP/suturing/TA). On comparison of the DDAVP/TA and TA groups, no significant difference in ISTH BAT (median 9 vs 7, p=0.3) or plasma VWF levels (Table 1) at time of procedure was seen. However, the TA only cohort were significantly older (median 55.1 vs 29.3 years, y, p=0.0002), influencing treatment choice. Of interest, in the 4/10 with TA only who bled, pre-DE plasma VWF levels were close to or within the normal range (VWF:RCo 47- 79 IU/dL). Minor procedures: Of the 114 minor procedures, 45.6% (52) were endoscopies, 31 with biopsy. The other 62 procedures were dermatological (19), orthopaedic (19), gynecological (8) or other (e.g. minor biopsies, 14). 17 procedures with low bleeding risk were performed with no hemostatic cover independent of the coagulation service. Excessive bruising was reported in 2/17 procedures, both patients were older (54 and 70 years) with pre-op plasma VWF levels within the normal range. For the remaining 97 procedures, 3 patients had CFC cover (unsuitable for DDAVP); 68 DDAVP/TA and 26 received only TA. Age contributed to prophylaxis choice, with TA cohort significantly older than the DDAVP/TA group (median 65.6 vs 42.5y, p=0.0004). However, phenotype also influenced with ISTH BAT scores significantly lower in the TA only cohort (median 3 vs 10.5, p<0.0001). No bleeding or significant change in perioperative Hgb levels were reported in any procedure covered with prophylaxis. Major : Data on major procedures were limited to 11 procedures covered with TA or DDAVP/TA. Plasma VWF levels were maintained following a single dose of DDAVP in all cases. A significant reduction in post-op Hgb levels was observed in TA only patients but no significant bleeding occurred (Table 1). The TA group were significantly older than DDAVP/TA patients (54.8 vs 33.6,p=0.03) but no significant difference in ISTH BAT score, pre-operative plasma VWF or Hgb levels or inpatient stay was seen, although numbers are limited. Conclusion: This study represents the largest analysis of procedural outcomes in patients with Low VWF to date. Our data suggest that age and ISTH BAT score significantly influence choice of hemostatic prophylaxis. Bleeding complications were observed only in LoVIC patients undergoing DE covered by TA, or with minor procedures with no hemostatic cover. Interestingly, patients who developed bleeding were typically older (median 59.7y) and, critically in this subgroup, bleeding occurred despite that plasma VWF levels had corrected to within the normal range, clearly raising the possibility that age-corrected normal ranges may need to be considered. Table Table. Disclosures Lavin: Shire: Honoraria, Research Funding, Speakers Bureau. O'Donnell:Bayer: Research Funding, Speakers Bureau; Baxter: Research Funding, Speakers Bureau; Shire: Research Funding, Speakers Bureau; Novo Nordisk: Research Funding, Speakers Bureau; Leo Pharma: Speakers Bureau; Octapharma: Speakers Bureau; CSL Behring: Consultancy; Daiichi Sankyo: Consultancy; Pfizer: Consultancy, Research Funding.

Download Full-text

Ex Vivo Evaluation of the Effect of Plasma-Derived Factor VIII/Von Willebrand Factor in Patients with Severe Hemophilia_A on Prophylaxis with Emicizumab By Thrombin Generation Assay

Blood ◽

10.1182/blood-2021-147184 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 4233-4233

Author(s):

Maria-Isabel Bravo ◽

Aida Raventós ◽

Alba Pérez ◽

Elena G Arias-Salgado ◽

María Teresa Alvarez Román ◽

...

Keyword(s):

Von Willebrand Factor ◽

Research Funding ◽

Thrombin Generation ◽

Ex Vivo ◽

Concomitant Treatment ◽

Healthy Controls ◽

Normal Range ◽

Von Willebrand ◽

Willebrand Factor

Abstract Introduction: Hemophilia A (HA) patients under emicizumab prophylaxis treatment may require the concomitant use of procoagulant factors for breakthrough bleedings or immune tolerance induction. Thromboembolic events have been described with the concomitant use of emicizumab and activated prothrombin complex concentrate (aPCC), but not with recombinant activated factor VII (rFVIIa). Previous studies showed that the in vitro combination of emicizumab and plasma-derived Factor VIII/Von Willebrand Factor (pdFVIII/VWF) had a non-additive effect on thrombin generation (TG)(Bravo M-I, et al J Thromb Haemost. 2020;18:1934-39). The aim of this study was to evaluate the TG resulting from ex vivo combination of plasma samples from HA patients treated with emicizumab, with a pdFVIII/VWF concentrate (Fanhdi ®, Grifols). Methods: Twelve adult patients with severe HA without inhibitors on prophylaxis with emicizumab and nine healthy controls were included in the study. Blood samples were drawn in citrate plus corn trypsin inhibitor tubes. Then, platelet poor plasma (PPP) was collected for the TG assay, which measures the whole kinetics of TG. Thrombin peak (TP) and endogenous thrombin potential (ETP) were calculated using calibrated automated thrombogram (Thrombinoscope ™ software, Stago) after in vitro activation of coagulation by trigger solution, PPP Reagent LOW TM (4 μM phospholipids/1 pM tissue factor), fluorogenic substrate and CaCl 2 (FLUKAkit TM) reagents (Diagnostica Stago). Fluorescence was read in a Fluoroskan Ascent reader (Thermo) equipped with a 390/460 filter set. Samples were spiked with increasing concentrations of pdFVIII/VWF (10 to 400 IU/dL), rFVIIa (0.9 µg/mL) or aPCC (0.5 U/mL). Results: TG from healthy control samples was measured to establish TP and ETP normal ranges. TP and ETP results obtained from HA plasma with emicizumab were lower than in healthy controls. The addition of pdFVIII/VWF as of 25 IU/kg (prophylaxis dose in HA w/o inhibitors) to samples from HA patients concomitantly treated with emicizumab restored TP and ETP levels within healthy controls normal range (Table 1). Increasing ex vivo concentrations of pdFVIII/VWF maintained TP and ETP similar to healthy controls. The highest concentration of concomitant treatment with pdFVIII/VWF (200 IU/kg) and emicizumab did not result in excessive TP and, importantly, ETP levels were always within the normal range. The combination with the bypassing agent rFVIIa moderately increased TP and ETP values up to normal range. However, when HA plasma was spiked with aPCC in the presence of emicizumab, TP and ETP dramatically increased above normal range resulting in a synergistic procoagulant profile. Conclusions: The concomitant use of pdFVIII/VWF in patients with prophylaxis with emicizumab did not trigger a multiplying effect on TG. These results were aligned with previous in vitro data and suggested the low risk of overdose and thrombotic events of concomitant treatment emicizumab with the pdFVIII/VWF concentrate in HA patients. Figure 1 Figure 1. Disclosures Bravo: Grifols: Current Employment, Other: Grifols is a manufacturer of the pdFVIII/VWF concentrate, Fanhdi®. Raventós: Grifols: Current Employment, Other: Grifols is a manufacturer of the pdFVIII/VWF concentrate, Fanhdi®. Pérez: Grifols: Current Employment, Other: Grifols is a manufacturer of the pdFVIII/VWF concentrate, Fanhdi®. Alvarez Román: Grifols: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Novo-Nordisk: Consultancy, Honoraria, Research Funding; Sobi: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; CSL-Behring: Consultancy, Honoraria, Research Funding; Biomarin: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding. Butta: CSL-Behring: Research Funding; Roche: Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Novo-Nordisk: Speakers Bureau. Jiménez-Yuste: Bayer: Consultancy, Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; CSL Behring: Consultancy, Honoraria, Research Funding; BioMarin: Consultancy; Sobi: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria, Research Funding. Costa: Grifols: Current Employment, Other: Grifols is a manufacturer of the pdFVIII/VWF concentrate, Fanhdi®. Willis: Grifols: Current Employment, Other: Grifols is a manufacturer of the pdFVIII/VWF concentrate, Fanhdi®.

Download Full-text

Standardisation of von Willebrand Factor in Therapeutic Concentrates: Calibration of the 1st International Standard for von Willebrand Factor Concentrate (00/514)

Thrombosis and Haemostasis ◽

10.1055/s-0037-1613226 ◽

2002 ◽

Vol 88 (09) ◽

pp. 380-386 ◽

Cited By ~ 9

Author(s):

Dawn Sands ◽

Andrew Chang ◽

Claudine Mazurier ◽

Anthony Hubbard

Keyword(s):

Von Willebrand Factor ◽

International Study ◽

Expert Committee ◽

International Standard ◽

A Value ◽

Significant Difference ◽

Factor Concentrate ◽

Von Willebrand ◽

Willebrand Factor ◽

Good Agreement

SummaryAn international study involving 26 laboratories assayed two candidate von Willebrand Factor (VWF) concentrates (B and C) for VWF:Antigen (VWF:Ag), VWF:Ristocetin Cofactor (VWF:RCo) and VWF:Collagen binding (VWF:CB) relative to the 4th International Standard Factor VIII/VWF Plasma (4th IS Plasma) (97/586). Estimates of VWF:Ag showed good agreement between different methods, for both candidates, and the overall combined means were 11.01 IU/ml with inter-laboratory variability (GCV) of 10.9% for candidate B and 14.01 IU/ml (GCV 11.8%) for candidate C. Estimates of VWF:RCo showed no significant difference between methods for both candidates and gave overall means of 9.38 IU/ml (GCV 23.7%) for candidate B and 10.19 IU/ml (GCV 24.4%) for candidate C. Prior to the calibration of the candidates for VWF:CB it was necessary to calibrate the 4th IS Plasma relative to local frozen normal plasma pools; there was good agreement between different collagen reagents and an overall mean of 0.83 IU per ampoule (GCV 11.8%) was assigned. In contrast, estimates of VWF:CB in both candidates showed large differences between collagen reagents with inter-laboratory GCV’s of 40%. Candidate B (00/514) was established as the 1st International Standard von Willebrand Factor Concentrate by the WHO Expert Committee on Biological Standardisation in November 2001 with assigned values for VWF:Ag (11.0 IU/ampoule) and VWF:RCo (9.4 IU/ampoule). Large inter-laboratory variability of estimates precluded the assignment of a value for VWF:CB.

Download Full-text

Increased plasma von Willebrand factor antigen levels but normal von Willebrand factor cleaving protease (ADAMTS13) activity in preeclampsia

Thrombosis and Haemostasis ◽

10.1160/th08-05-0330 ◽

2009 ◽

Vol 101 (02) ◽

pp. 305-311 ◽

Cited By ~ 37

Author(s):

János Rigó Jr ◽

Tamás Bõze ◽

Zoltán Derzsy ◽

László Cervenak ◽

Veronika Makó ◽

...

Keyword(s):

Pregnant Women ◽

Von Willebrand Factor ◽

Hellp Syndrome ◽

Enzyme Linked Immunosorbent Assay ◽

Adamts13 Activity ◽

Elevated Liver Enzymes ◽

Significant Difference ◽

Low Platelet Count ◽

Von Willebrand ◽

Willebrand Factor

SummaryThe activity of ADAMTS13, the von Willebrand factor (VWF) cleaving protease is low in several conditions, including HELLP (haemolysis, elevated liver enzymes, and low platelet count) syndrome. As HELLP syndrome develops in most cases on the basis of preeclampsia, our aim was to determine whether plasma ADAMTS13 activity is decreased in preeclampsia. Sixty-seven preeclamptic patients, 70 healthy pregnant women and 59 healthy non-pregnant women were involved in this case-control study. Plasma ADAMTS13 activity was determined with the FRETS-VWF73 assay, while VWF antigen (VWF:Ag) levels with an enzyme-linked immunosorbent assay. The multimeric pattern of VWF was analyzed by SDS-agarose gel electrophoresis. There was no significant difference in plasma ADAMTS13 activity between the preeclamptic and the healthy pregnant and non-pregnant groups (median [25–75 percentile]: 98.8 [76.5–112.8] %, 96.3 [85.6–116.2] % and 91.6 [78.5–104.4] %, respectively; p>0.05). However, plasma VWF:Ag levels were significantly higher in preeclamptic patients than in healthy pregnant and non-pregnant women (187.1 [145.6–243.1] % versus 129.3 [105.1–182.8] % and 70.0 [60.2–87.3] %, respectively; p<0.001). The multimeric pattern of VWF was normal in each group. Primiparas had lower plasma ADAMTS13 activity than multi-paras (92.6 [75.8–110.6] % versus 104.2 [92.1–120.8] %; p=0.011). No other relationship was found between clinical characteristics, laboratory parameters and plasma ADAMTS13 activity in either study group. In conclusion, plasma ADAMTS13 activity is normal in preeclampsia despite the increased VWF:Ag levels. However, further studies are needed to determine whether a decrease in plasma ADAMTS13 activity could predis-pose preeclamptic patients to develop HELLP syndrome.

Download Full-text

BLEEDING TIME IN NORMAL SUBJECTS: ITS RELATIONSHIP WITH SEX, AGE, BLOOD GROUP, HEMATOCRIT, PLATELET COUNT AND PLASMA VON WILLEBRAND FACTOR LEVEL

10.1055/s-0038-1644848 ◽

1987 ◽

Author(s):

F Rodeghiero ◽

G Castaman ◽

E Di Bona ◽

M Ruggeri

Keyword(s):

Platelet Count ◽

Blood Group ◽

Von Willebrand Factor ◽

Bleeding Time ◽

Physiological Parameters ◽

Factor Level ◽

Significant Difference ◽

Von Willebrand ◽

Willebrand Factor

Bleeding time (BT) is the most important test for in "vivo" Vevaluation of primary hemostasis. Several physiological parameters namely sex, age, blood group, hematocrit, platelet count and von Willebrand factor level could exert a significant influenceIn this study, the relationships between BT (Simplate II,General Diagnostics)and these physiological parameters havebeen examined in 58 subjects aging 17-71 (32 males and 26 females; 26 of 0 and 32 of non-0 group). In all the subjects bleedingdiathesis was excluded by interview. They were not taking anvmedicament for at least 10 days and showed normal platelet aggregation by ADP and ArachidonateMean BT value (seconds) was 318± 65 (range 195-A95)Statistical analysis failed to show any significant difference realated to sex and blood group. There was no significant relationship with hematocrit (0.01), platelet count (−0.2A), age (−0.28) and von Willebrand factor level, mesured as ristocetin cofactor (−0.2A). In particular, our data indicate that higher von Willebrand factor levels found in non-0 group in comparison with O-group (113.3 vs 83.5, P < 0:001) do not exert any apparent influence on bleeding time

Download Full-text

Influence of mutations and size of multimers in type II von Willebrand disease upon the function of von Willebrand factor

Blood ◽

10.1182/blood.v83.12.3553.3553 ◽

1994 ◽

Vol 83 (12) ◽

pp. 3553-3561 ◽

Cited By ~ 13

Author(s):

O Christophe ◽

AS Ribba ◽

D Baruch ◽

B Obert ◽

C Rouault ◽

...

Keyword(s):

Von Willebrand Factor ◽

Point Mutations ◽

Von Willebrand Disease ◽

Platelet Glycoprotein ◽

Binding Assays ◽

Normal Individuals ◽

Binding Isotherms ◽

Significant Difference ◽

Von Willebrand ◽

Willebrand Factor

Abstract We compared the properties of plasma von Willebrand factor (vWF) from normal individuals and from two patients with type IIA (Glu875Lys) and type IIB (duplication of Met 540) von Willebrand disease (vWD) with the corresponding fully multimerized recombinant proteins. We included cryosupernatant from normal human plasma and type IIA plasma (Cys509Arg). Functions of vWF were analyzed by binding assays to platelets in the presence of ristocetin or botrocetin. Parameters of binding (number of binding sites per vWF subunit, and dissociation constant Kd) were quantitatively estimated from the binding isotherms of 125I-botrocetin or glycocalicin to vWF, independently of the size of the multimers. We found that ristocetin- or botrocetin-induced binding to platelets was correlated in all cases with the size of vWF multimers. In the absence of inducer, only type IIB rvWF Met-Met540 spontaneously bound to platelets. No significant difference of binding of purified botrocetin to vWF was found between normal and patients' plasma, or between wild-type rvWF (rvWF-WT) and rvWF-Lys875. In contrast, affinity of botrocetin for type IIB rvWF Met-Met540 was decreased. Botrocetin-induced binding of glycocalicin to vWF from all plasma and cryosupernatant was similar. Compared with rvWF-WT, binding of glycocalicin to rvWF-Lys875 was normal. In contrast, the affinity for type IIB rvWF Met-Met540 was 10-fold greater. Thus, our data suggest that, in the patients tested, the abnormal IIA phenotype results from the lack of large-sized multimers and is independent of the point mutations. In contrast, the type IIB mutation is directly involved by providing a conformation to the vWF subunits that allows the high molecular weight multimers to spontaneously interact with platelet glycoprotein Ib.

Download Full-text

von Willebrand Factor/Factor VIII Concentrate (Humate-P®) Is Safe and Effective in the Prevention of Perioperative Bleeding in Patients with Very Low von Willebrand Factor: Ristocetin Cofactor (VWF:RCo).

Blood ◽

10.1182/blood.v108.11.4071.4071 ◽

2006 ◽

Vol 108 (11) ◽

pp. 4071-4071

Author(s):

Joan Cox Gill ◽

Cindy A. Leissinger ◽

Jorge DiPaola ◽

Jonathan Bernstein ◽

Margaret V. Ragni ◽

...

Keyword(s):

Adverse Events ◽

Factor Viii ◽

Von Willebrand Factor ◽

Treatment Duration ◽

Major Surgery ◽

Minor Surgery ◽

Hemostatic Efficacy ◽

Von Willebrand ◽

Tooth Extractions ◽

Willebrand Factor

Abstract Optimal dosing to prevent excessive surgical bleeding in von Willebrand Disease (VWD) was investigated in an open-label study of replacement therapy with a von Willebrand factor/factor VIII concentrate (VWF/FVIII, Humate-P®). This analysis focused on the subset of patients with very low VWF, defined as those with baseline VWF:RCo levels of <12 IU/dL. Of a total of 35 patients, 17 had very low levels of VWF:RCo; of these 17 “severe” VWD patients, 12 had type 3 VWD, one each had types 1, 2A or 2B, and 2 had type 2M VWD. Previous pharmacokinetic data in each patient was utilized to calculate pre-operative and immediate postoperative doses to raise plasma VWF:RCo and FVIII to 80–100 IU/dL for major surgery and 50–60 IU/dL for minor and oral surgery; subsequent doses were adjusted based on VWF:RCo levels. Eleven patients underwent major surgery including orthopedic, gynecologic and plastic surgery, and multiple tooth extractions; 4 had minor surgery and 2 had single tooth extractions. Hemostatic efficacy was assessed by investigators as excellent, good, moderate/poor, or none immediately after the surgery, 24 hours after the last VWF/FVIII infusion and 14 days post-op. Expected and actual estimated blood loss (EBL) was compared, transfusions recorded and adverse events (AEs) documented. The median loading dose was higher among subjects with severe VWD types (71 IU/kg, range 39 to 135) compared with non-severe VWD (44 IU/kg, range 17 to 121). Subjects with severe VWD types also used higher total doses (median: 280 IU/kg, range 63 to 859) and had longer treatment duration (6 days, range 1–26) than subjects with non-severe VWD types (median total dose: 208 IU/kg, range 79 to 1699; and treatment duration: 4.5 days, range 2–19). Hemostasis was rated as effective (good or excellent efficacy) in 15/17 (88.2%) patients immediately postoperatively, in 17/17 (100%) patients 24 hours after the last infusion (primary endpoint), and in 17/17 (100%) patients 14 days postoperatively. A bleeding related serious AE occurred in one patient; she had hemorrhage post-hysteroscopic resection of uterine fibroids followed by hysterectomy; actual EBL exceeded expected EBL and hemostatic efficacy was considered moderate/poor immediately post-op but good/excellent at the other time points. Three other surgery-related hemorrhagic events were mild in the severe VWD types; in the non-severe VWD patients, 1 severe, 1 moderate and 2 mild hemorrhagic adverse events were reported; none of these were considered to be related to poor efficacy of the drug. No thromboembolic complications or changes in viral titers were observed in the study. We conclude that patients with very low baseline VWF levels can safely undergo both major and minor surgery with VWF/FVIII concentrate when dosing is calculated to achieve and maintain hemostatic VWF levels based on VWF:RCo monitoring. It is important to base therapeutic decisions on the severity of disease as assessed by baseline plasma VWF and FVIII levels as well as VWD type.

Download Full-text

Compromised Proteolytic Cleavage of Von Willebrand Factor Type 2N Variants by ADAMTS13 in the Presence of Factor VIII (and Platelets) Under Fluid Shear Stress.

Blood ◽

10.1182/blood.v114.22.28.28 ◽

2009 ◽

Vol 114 (22) ◽

pp. 28-28

Author(s):

Christopher G. Skipwith ◽

Sandra L. Haberichter ◽

Wenjing Cao ◽

Ashley L. Gehrand ◽

X. Long Zheng

Keyword(s):

Shear Stress ◽

Factor Viii ◽

Von Willebrand Factor ◽

Fluid Shear Stress ◽

Proteolytic Cleavage ◽

Binding Activity ◽

Clotting Factor ◽

Fluid Shear ◽

Von Willebrand ◽

Willebrand Factor

Abstract Abstract 28 von Willebrand Factor (VWF) is a large, multimeric adhesive glycoprotein that is involved in the formation of a platelet plug after vascular injury. In addition, VWF functions as a carrier protein for clotting factor VIII (FVIII) which prevents rapid clearance of plasma FVIII. Decreased levels of VWF or defects in VWF function are found in patients with von Willebrand disease (VWD). Quantitative defects of VWF protein in type 1 and 3 VWD affect plasma levels of both VWF and FVIII, whereas qualitative defects in type 2 VWD result in abnormal binding of VWF to platelets such as in type 2A, 2B, and 2M, or to FVIII such as in type 2N. Previous studies have demonstrated that FVIII binds VWF, which dramatically accelerates the proteolytic cleavage of multimeric VWF by ADAMTS13 under mechanically-induced shear stresses. This rate-enhancing effect of FVIII on VWF proteolysis appears to depend on the ability of FVIII to bind VWF, as a FVIII variant lacking the A3 acidic region fails to exhibit the cofactor activity that accelerates VWF proteolysis. To determine whether reduced FVIII binding in VWF type 2N variants affects VWF proteolysis, we examined the proteolytic cleavage of recombinant VWF type 2N variants in the presence of FVIII (and lyophilized platelets) for variants with a moderate VWD phenotype (Arg854Gln and His817Gln) or severe VWD phenotype (Arg763Gly, Arg782Trp, Thr791Met, and Arg782Trp + His817Gln). Recombinant VWF type 2N variants (37.5 μg/ml or 150 nM) were incubated with ADAMTS13 (25 nM) in the absence and the presence of various concentrations of FVIII (0-40 nM) with or without lyophilized platelets (0-600×103/μl) under fluid shear stress. The proteolytic cleavage products (350 kDa) were determined by 5% SDS-PAGE and Western blot under denaturing but non-reducing conditions. We show that the proteolytic cleavage of VWF type 2N variants by ADAMTS13 under these conditions was variably reduced as compared that of wild type VWF. The reduction in the cleavage rate was proportional to the degree of reduction in VWF FVIII binding activity, which was assessed with a microtiter assay, with the least cleavage by ADAMTS13 of the variants with the lowest FVIII binding activity. This reduced cleavage of the type 2N variants was not correlated with the binding affinity between the type 2N variants and ADAMTS13 protease. These results provide further evidence that binding of FVIII to VWF, which may alter VWF conformation, is necessary to accelerate VWF proteolysis by ADAMTS13 under fluid shear stress. This variability in ADAMTS13 cleavage may contribute to the heterogeneity of bleeding phenotype of type 2N VWD variants. The bleeding phenotype may be modulated not only by plasma FVIII levels, but also the extent of VWF proteolysis by ADAMTS13 under physiological fluid shear stress. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Therapeutic Algorithm for Patients with Acquired Von Willebrand Syndrome and Monoclonal Gammopathy.

Blood ◽

10.1182/blood.v114.22.4445.4445 ◽

2009 ◽

Vol 114 (22) ◽

pp. 4445-4445

Author(s):

Peter Staritz ◽

Manuela Krause ◽

Rainer Zimmermann ◽

Angela Huth-Kuehne

Keyword(s):

Von Willebrand Factor ◽

Half Life ◽

Major Surgery ◽

Ivig Treatment ◽

First Line ◽

Acquired Von Willebrand Syndrome ◽

Acute Bleeding ◽

Therapeutic Algorithm ◽

Von Willebrand ◽

Willebrand Factor

Abstract Abstract 4445 In contrast to congenital von Willebrand Syndrome therapy of acute bleeding in acquired von Willebrand Syndrome (AWS) with von Willebrand factor containing concentrates (F VIII/vWF) is often ineffective. In patients with IgG monoclonal antibodies therapy with intravenous immunoglobulins (IVIG) is reported to be effective whereas patients with IgM antibodies seem not to respond to IVIG. Over the last years we diagnosed and treated several patients with AWS either prior to surgery or due to acute bleeding. About half of the patients responded adequately to IVIG as reported in the literature. One patient with no response to IVIG 4 days after the last dose received DDAVP with a significant increase in von Willebrand factor-antigen and ristocetin cofactor and normalized half life. Dental surgery could be performed without any bleeding complications under daily infusions of DDAVP. Another patient with partial response to IVIG and contraindications to DDAVP received F VIII/vWF prior to dental extraction. In contrast to former recoveries with a shortened half life of the infused concentrate (about 2 hours), half life of vWF was significantly prolonged following prior IVIG treatment. Another patient responded sufficiently to single therapy with F VIII/vWF. A further patient with suspected diagnosis of moderate hemophilia A had received DDAVP for severe epistaxis with good response and sufficient half lifes. He was transferred to our centre and we diagnosed AVW with IgM antibodies. We performed another recovery and half life with DDAVP with adequate response. According to our experience we propose the following therapeutic algorithm: A recovery with DDAVP should be performed first line if treatment is not contraindicated. In case of insufficient half lifes and/or intended major surgery, a recovery and half life with F VIII/vWF concentrate should follow. In case of significantly reduced half life of wWF an attempt with IVIG is necessary. If response to IVIG is not adequate further treatment with DDAVP or F VIII/vWF is indicated. As treatment with IVIG is not predictable in all patients with IgG antibodies and is very costly a therapeutic attempt with DDAVP in the first line and F VIII/vWF second line is worthwhile. In major surgery requiring prolonged replacement therapy, IVIG treatment, if effective, is less costly than treatment with FVIII/vWF. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Primary Myeloma Cell Induced Von Willebrand Factor Release from the Endothelium Is Mediated By VEGF and Attenuated By Heparin

Blood ◽

10.1182/blood-2021-149134 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3141-3141

Author(s):

Claire Comerford ◽

Sukhraj Pal Singh Dhami ◽

Philip Murphy ◽

Sean Patmore ◽

Siobhan Glavey ◽

...

Keyword(s):

Molecular Weight ◽

Partial Response ◽

Von Willebrand Factor ◽

Research Funding ◽

Myeloma Cell ◽

Response To Therapy ◽

Dependent Manner ◽

Anti Vegf ◽

Von Willebrand ◽

Willebrand Factor

Abstract Introduction Multiple Myeloma (MM) remains an incurable disease and is associated with high rates of venous thromboembolism (VTE), the biological basis for which is not fully understood. Critically, VTE is associated with increased mortality in MM. This highlights the clinical importance of understanding cancer-coagulation crosstalk in MM. Accumulating evidence demonstrates that many solid tumours trigger endothelial cell (EC) activation with resultant von Willebrand Factor (VWF) secretion proposed to contribute to both risk of VTE and cancer metastasis. However, the interplay between VWF and MM disease biology remains poorly defined. Methods/Results 100 patients with plasma cell disorders were recruited to this study. Significantly elevated plasma VWF antigen (VWF:Ag) levels were observed in patients with newly diagnosed MM (NDMM) compared to those with monoclonal gammopathy of undetermined significance (MGUS) or smouldering MM (SMM) (median 292.7 IU/dL vs 133.1 IU/dL; P<0.0001). Moreover, VWF:Ag levels in those with relapsed/refractory MM (RRMM) were further elevated (median 339 IU/dL; P<0.0001]). VWF:Ag levels also appear to correlate with disease response to therapy, with lower levels seen in patients achieving a complete response/very good partial response compared with those gaining only a partial response or worse (median 154.45 IU/dL vs 338.5 IU/dL; P<0.05). We also observed increased VWF collagen binding activity in NDMM/RRMM compared with MGUS/SMM (median 455.7 IU/dL vs 189.7 IU/dL; P<0.05). This qualitative measurement is sensitive to alterations in haemostatically active high molecular weight multimers of VWF secreted upon EC activation. Supporting this, raised plasma VWF propeptide (VWFpp) levels, a marker of acute EC activation, were seen in those with NDMM/RRMM compared with MGUS/SMM (median 182 IU/dL vs 133.01 IU/dL; P<0.05). Reduced VWFpp/VWF:Ag ratios were seen in those with NDMM/RRMM, indicating decreased circulatory clearance of VWF. We hypothesise that MM may exhibit a 'double-hit' in regulation of plasma VWF:Ag with increased secretion of VWF but also simultaneously reduced VWF clearance leading to sustained and markedly elevated systemic plasma VWF levels. Next we measured VWF:Ag levels in bone marrow (BM) samples from 10 patients and found that VWF is released locally within the BM niche (median 190.2 IU/dL). Co-culture of primary human ECs with supernatant from freshly isolated primary MM cells or several Human Myeloma Cell Lines (HMCLs) demonstrated that MM cells stimulate release of VWF from ECs in a rapid manner, suggestive of Weibel-Palade body exocytosis (median 34.9ng/ml vs 9.2ng/ml in untreated EC; P<0.05). Elevated levels of Vascular Endothelial Growth Factor-A (VEGF-A), a potent EC activator, were observed in MM cell supernatants. Pre-treatment of primary MM cells or HMCLs with anti-VEGF antibody bevacizumab abolished EC VWF secretion in a dose dependant manner (32.3ng/ml vs anti-VEGF treated 10.1ng/ml P<0.0001). Furthermore, clinically relevant doses of low molecular weight heparin (LMWH) also attenuated VWF secretion (29.6ng/ml vs LMWH treated 15ng/ml; P<0.05). Measurement of VEGF-A in primary MM cell and HMCL supernatant treated with LMWH or bevacizumab confirmed significant reductions in VEGF-A levels. Together these data indicate that stimulation of VWF release from the endothelium by MM cells is mediated by VEGF-A and directly inhibited by LMWH treatment. Using flow cytometry, we assessed the direct interaction of MM cells and VWF in vitro. Both primary MM cells and HMCLs bound significantly to human recombinant VWF in a dose-dependent manner. Binding was reduced by 50% following treatment with LMWH (P<0.05). Given that the VWF A1 domain contains a heparin binding motif, we speculate that MM cell adhesion to VWF may be at least in part mediated by this domain and future work focuses on elucidating the receptors involved. Conclusion These data suggest that MM is not only associated with a marked quantitative increase in plasma VWF:Ag, but also impacts VWF functional activity. Our novel data help define the biological mechanisms underpinning elevated VWF levels in MM, with a key contribution of VEGF-A secreted directly from MM cells in the BM microenvironment. Collectively, our findings provide insights into cancer-coagulation crosstalk in MM and may help identify novel therapeutic targets to reduce VTE risk and disease progression. Disclosures Glavey: Celgene and BMS company: Research Funding; Janssen: Honoraria, Research Funding; Abbvie: Research Funding; Amgen: Honoraria, Research Funding. Quinn: Takeda: Honoraria. O'Sullivan: Leo Pharma: Research Funding.

Download Full-text

The spectrum and severity of bleeding in adolescents with low von Willebrand factor–associated heavy menstrual bleeding

Blood Advances ◽

10.1182/bloodadvances.2020002081 ◽

2020 ◽

Vol 4 (13) ◽

pp. 3209-3216 ◽

Cited By ~ 1

Author(s):

Lakshmi Srivaths ◽

Charles G. Minard ◽

Sarah H. O’Brien ◽

Allison P. Wheeler ◽

Eric Mullins ◽

...

Keyword(s):

Von Willebrand Factor ◽

Assessment Tool ◽

Combined Therapy ◽

Laboratory Data ◽

Heavy Menstrual Bleeding ◽

Menstrual Bleeding ◽

Bleeding Complications ◽

Eligibility Criteria ◽

Von Willebrand ◽

Willebrand Factor

Abstract Low von Willebrand factor (VWF) in adults is associated with significant bleeding, most notably heavy menstrual bleeding (HMB) and postpartum hemorrhage, although this has not been characterized in adolescents. The objectives of this analysis of a multicenter single arm observational cohort study in adolescents with low VWF–associated HMB were to describe the bleeding phenotype, HMB severity, and related complications. Eligibility criteria included postmenarchal females <21 years of age with HMB (Pictorial Blood Assessment Chart [PBAC] score >100) and low VWF (2 values of VWF activity ≥30 and ≤50 IU/dL). Patients diagnosed with other bleeding disorders were ineligible. Clinical phenotype data, including PBAC and Bleeding Assessment Tool (BAT) scores, laboratory data, and HMB management/outcome details, were extracted. Patient demographics and clinical characteristics were summarized as medians with minimum/maximum values or frequencies with percentages. Groups were compared using a Wilcoxon rank-sum test or Fisher’s exact test. A total of 113 patients met inclusion criteria, and 2 were excluded. Ninety four percent had a significant bleeding phenotype (BAT score >2), with predominantly mucocutaneous bleeding (32%-44%), postprocedural/surgical bleeding (15%), and severe HMB (BAT HMB domain score ≥2; 90%). Bleeding complications included iron deficiency (60%), anemia (21%), transfusion (12%), and hospitalization (10%). Desmopressin challenge response in subjects tested was good and sustained. Several (48%) required combined therapy for HMB (hormonal/hemostatic), and one third did not show improvement despite therapy. Our results suggest that adolescent females with low VWF have a significant bleeding phenotype and resultant complications warranting a focus on prompt diagnosis, appropriate therapy, and prevention of complications.

Download Full-text