Search

Introduction: Patients with von Willebrand disease (VWD) require administration of von Willebrand factor (VWF) concentrates peri‐operatively. Concerns about FVIII accumulation after repetitive injections of a 1:1 ratio VWF/FVIII clotting factor concentrate (CFC) led this study to explore the recovery and FVIII accumulation over time. Methods: This monocentre study examined patients with VWD receiving perioperative 1:1 ratio CFC infusions. CFC dosing was based on body weight and endogenous VWF/FVIII activity. FVIII and VWF activity was monitored at T0 (baseline), T1 (15 min postinfusion), and trough levels at T2‐T6 (24‐120 h). Results: We included 125 patients, undergoing 125 procedures (63 major surgeries, 62 minor), with a median of two CFC infusions (IQR 1–3). With a mean administered dose of 35.7 IU/kg CFC, recovery rates of FVIII and VWF were 2.6 IU/dL per IU/kg and 2.4 IU/dL per IU/kg, respectively. Mean FVIII levels at T0 were 62 (SD 51.9), T1: 164 (SD 80.4), T2: 155 (SD 62.8), T3: 162 (SD 59.8), T4: 124 (SD 78.4), and T5: 120 (SD 65.3) IU/dL. Mean VWF activity levels at T0 were 29 (SD 25.0), T1: 133 (SD 43.7), T2: 92 (SD 37.2), and T3: 86 (SD 37.5) IU/dL. Subgroup analysis in 47 patients with more than three infusions, showed no accumulation of mean FVIII levels. Conclusion: This perioperative study demonstrated excellent FVIII and VWF recovery of a 1:1 ratio VWF product in patients with VWD. Stable FVIII and VWF activity levels were observed after repeated infusions, without accumulation. Most major surgeries required only three CFC infusions. [ABSTRACT FROM AUTHOR]

Blood disorders, such as sickle cell disease, and other clinical conditions are often accompanied by intravascular hemolytic events along with the development of severe coagulopathies. Hemolysis, in turn, leads to the accumulation of Fe(II/III)-protoporphyrin IX (heme) in the intravascular compartment, which can trigger a variety of proinflammatory and prothrombotic reactions. As such, heme binding to the blood coagulation proteins factor VIII (FVIII), fibrinogen, and activated protein C with functional consequences has been demonstrated earlier. We herein present an in-depth characterization of the FVIII-heme interaction at the molecular level and its (patho-)physiological relevance through the application of biochemical, biophysical, structural biology, bioinformatic, and diagnostic tools. FVIII has a great heme-binding capacity with seven heme molecules associating with the protein. The respective binding sites were identified by investigating heme binding to FVIII-derived peptides in combination with molecular docking and dynamic simulation studies of the complex as well as cryo-electron microscopy, revealing three high-affinity and four moderate heme-binding motifs (HBMs). Furthermore, the relevance of the FVIII-heme complex formation was characterized in physiologically relevant assay systems, revealing a ~ 50 % inhibition of the FVIII cofactor activity even in the protein-rich environment of blood plasma. Our study provides not only novel molecular insights into the FVIII-heme interaction and its physiological relevance, but also strongly suggests the reduction of the intrinsic pathway and the accentuation of the final clotting step (by, for example, fibrinogen crosslinking) in hemolytic conditions as well as a future perspective in the context of FVIII substitution therapy of hemorrhagic events in hemophilia A patients. [Display omitted] • Coagulation factor VIII (FVIII) binds rapidly up to seven heme molecules. • Heme binds to sequence stretches of functional relevance for FVIII. • Labile heme causes distinct structural changes in FVIII, including increased flexibility. • FVIII cofactor function is significantly impaired by heme in blood plasma. [ABSTRACT FROM AUTHOR]

Snake venoms, comprising a complex array of protein-rich components, an important part of which are snake venom metalloproteinases (SVMPs). These SVMPs, which are predominantly isolated from viperid venoms, are integral to the pathology of snakebites. However, SVMPs derived from elapid venoms have not been extensively explored, and only a handful of SVMPs have been characterized to date. Atrase A, a nonhemorrhagic P-III class metalloproteinase from Naja atra venom, exhibits weak proteolytic activity against fibrinogen in vitro but has pronounced anticoagulant effects in vivo. This contrast spurred investigations into its anticoagulant mechanisms. Research findings indicate that atrase A notably extends the activated partial thromboplastin time, diminishes fibrinogen levels, and impedes platelet aggregation. The anticoagulant action of atrase A primarily involves inhibiting coagulation factor VIII and activating the endogenous fibrinolytic system, which in turn lowers fibrinogen levels. Additionally, its effect on platelet aggregation further contributes to its anticoagulant profile. This study unveils a novel anticoagulant mechanism of atrase A, significantly enriching the understanding of the roles of cobra venom metalloproteinases in snake venom. Furthermore, these findings underscore the potential of atrase A as a novel anticoagulant drug, offering insights into the functional evolutions of cobra venom metalloproteinases.

Background: Von Willebrand factor (vWF) is an important part of blood coagulation since it binds platelets to each other and to endothelial cells. In traumatic and surgical haemorrhage, both blood cells and plasmatic factors are consumed, leading to consumption coagulopathy and fluid resuscitation. This often results in large amounts of crystalloids and blood products being infused. Additional administration of vWF complex and platelets might mitigate this problem. We hypothesize that administration of vWF concentrate additionally to platelet concentrates reduces blood loss and the amount of blood products (platelets, red blood cells [RBC], fresh frozen plasma [FFP]) administered. Methods: We conducted a monocentric 6-year retrospective data analysis of cardiac surgery patients. Included were all patients receiving platelet concentrates within 48 h postoperatively. Patients who additionally received vWF concentrates were allocated to the intervention group and all others to the control group. Groups were compared in mixed regression models correcting for known confounders, based on nearest neighbour propensity score matching. Primary endpoints were loss of blood (day one and two) and amount of needed blood products on day one and two (platelets, RBC, FFP). Secondary endpoints were intensive care unit (ICU) and in-hospital length of stay, ICU and in-hospital mortality, and absolute difference of platelet counts before and after treatment. Results: Of 497 patients analysed, 168 (34%) received vWF concentrates. 121 patients in both groups were considered for nearest neighbour matching. Patients receiving additional vWF were more likely to receive more blood products (RBC, FFP, platelets) in the first 24 h after surgery and had around 200 mL more blood loss at the same time. Conclusion: In this retrospective analysis, no benefit in additional administration of vWF to platelet concentrates on perioperative blood loss, transfusion requirement (platelets, RBC, FFP), length of stay, and mortality could be found. These findings should be verified in a prospective randomized controlled clinical trial (www.clinicaltrials.gov identifier NCT04555785). [ABSTRACT FROM AUTHOR]

Background and Objectives: In Australia, the vast distances between blood collection centres and processing facilities make it challenging to align supply with demand. Increasing the time to freezing for clinical plasma beyond 6 h would alleviate supply issues. This study aimed to determine the quality of clinical apheresis plasma frozen within 12 h of collection. Materials and Methods: Apheresis plasma (n = 20) collected at donor centres was immediately transported to a blood processing facility, stored at 26°C and sampled aseptically at 6, 8 and 12 h post collection. Frozen samples were thawed, and coagulation factors (F) II, V, VII, VIII and XIII, von Willebrand factor (vWF) and fibrinogen were measured using a coagulation analyser. Results: FVIII concentrations declined in plasma frozen at 6, 8 and 12 h post collection (1.22 ± 0.27, 1.21 ± 0.25 and 1.16 ± 0.24 IU/mL, respectively) but not significantly (p = 0.3338). Importantly, all components met the FVIII specification (>0.7 IU/mL) for clinical plasma. Fibrinogen concentrations were stable from 6 to 12 h (p = 0.3100), as were vWF concentrations (p = 0.1281). Coagulation factors II, V, VII and XIII were not significantly different (p > 0.05 for all factors). Conclusion: Clinical apheresis plasma can be frozen within 12 h of collection, allowing collections from donor centres further from processing centres and increasing supply. [ABSTRACT FROM AUTHOR]

Acquired hemophilia A（AHA) is a rare bleeding disorder caused by the circulating autoantibodies directedly against coagulation factor Ⅷ, resulting in decreased activity of coagulation factor Ⅷ.In recent years, awareness of the disease has gradually increased due to the increased reporting of the disease and data reported from several large registry studies in China and abroad, but due to the relative rarity of the disease itself, there is still a lack of awareness and delay in diagnosis and treatment.Its treatment consists of three main aspects: control of bleeding in the acute phase, eradication of inhibitors, and treatment of the primary disease or removal of the causative agent. Immunosuppressive treatment（IST) to eradicate inhibitors is the therapeutic foundation. However, recent studies have shown that IST-related mortality exceeds even that caused directly by bleeding, so the IST of AHA is still very challenging and requires continuous experience and exploration of optimal treatment protocols. In this paper, we will focus on the basic clinical features, characteristics of coagulation factor Ⅷ inhibitors in acquired hemophilia A, the current major immunosuppressive treatment options, and the latest treatment options. [ABSTRACT FROM AUTHOR]

Background Pre-anesthetic evaluation is an important aspect of perioperative patient management. However, anesthesiologists often encounter challenges during anesthesia due to conditions that are not detected during pre-anesthetic evaluations. Case Case 1 involved a 74-year-old female patient scheduled for cranioplasty and meningioma excision. Severe pancytopenia was detected during anesthesia. Cranioplasty was only performed, the surgery was terminated, and drug-induced pancytopenia was diagnosed and treated. The pre-anesthetic test results were normal, except for anemia. Case 2 involved a 71-year-old male patient who discovered large ecchymosis during general anesthesia preparation in the operating room for choledochal cyst surgery. Surgery was canceled to evaluate the bleeding tendency, and acquired coagulation factor VIII deficiency was diagnosed and treated. The pre-anesthetic tests were normal, except for prolongation of the activated partial thromboplastin time. Conclusions Abrupt hematologic and hemostatic changes may occur during anesthesia even though pre-anesthetic evaluation findings are normal.

Hemophilia A is an X-chromosome-linked recessive genetic disease that lacks coagulation factor Ⅷ (Factor Ⅷ, FⅧ) and is clinically manifested as spontaneous or excessive bleeding after injury.The current main treatment for hemophilia A is alternative infusion of FⅧ, but the fixed infusion mode is still used for the dosage and frequency of infusion, which cannot achieve the optimal curative effect under the principle of individualized treatment.Among the factors that affect the efficacy of FⅧ replacement therapy, the difference in the pharmacokinetics (PK) of FⅧ products by individuals is an important factor.The clinical understanding of individualized FⅧ replacement therapy under the guidance of PK is not sufficient.Therefore, this article reviews the PK characteristics, analysis models, clinical application scenarios and specific treatment plan formulation of FⅧ.

Background The efficacy, safety, and immunogenicity of each of Octapharma's factor VIII (FVIII) products, Nuwiq, octanate, and wilate, have been investigated in previously untreated patients (PUPs) with severe hemophilia A in prospective clinical trials. The aim of the Protect-NOW study is to evaluate the effectiveness, safety, and utilization patterns of Nuwiq, octanate, and wilate in PUPs and minimally treated patients (MTPs;

Introduction: Despite receiving standard half‐life (SHL) factor VIII (FVIII) concentrates prophylaxis, some severe haemophilia A (HA) patients still encounter spontaneous breakthrough bleeding. Individualized pharmacokinetic (PK)‐guided dosing of extended half‐life (EHL) FVIII concentrates may reduce their bleeding events. Aim: To compare clinical outcomes before and after switching low‐dose prophylaxis using weight‐based SHL FVIII to PK‐guided EHL FVIII concentrates, taking into consideration of a trough FVIII activity at 1 IU/dl above natural baseline. Methods: In this single‐centre prospective cohort, Thai severe or moderate HA (FVIII activity ≤3 IU/dl) patients receiving low‐dose weight‐based SHL FVIII prophylaxis were enrolled. After a 3‐day wash‐out period, participants underwent low‐dose EHL FVIII prophylaxis with PK‐based adjustment (myPKFiT®) for 6 months. The annualized bleeding rates (ABR), the annualized joint bleeding rates (AJBR), the haemophilia‐specific quality‐of‐life (Haemo‐QoL or Haemo‐QoL‐A) scores, the Hemophilia Joint Health Scores (HJHS) and the annualized FVIII consumption were compared between the two prophylactic periods. Results: Of 15 eligible subjects (mean age 18.7 ± 6.7 years), ABR, AJBR and HJHS were significantly reduced (mean differences of ‐11.1 ± 4.9 bleeds/year, ‐10.4 ± 5.2 joint bleeds/year and ‐5.1 ± 1.5 marks, respectively; P <.001 for all comparisons) after switching regimen. The quality‐of‐life scores had also improved (P =.001). Nonetheless, FVIII consumption tended to increase despite no statistical significance (means of 1240.9 ± 531.3 SHL FVIII IU/kg/year versus 1591.7 ± 438.9 EHL FVIII IU/kg/year; P =.05). Conclusions: This is the first low‐dose, PK‐guided, EHL FVIII prophylaxis clinical study in Thailand. Benefits and practicability of this personalized regimen may support the implementation of regular FVIII prophylaxis in developing countries with budget constraints. ClinicalTrials.gov NCT05281185. [ABSTRACT FROM AUTHOR]

The splenic endothelial Weibel‐palade bodies are one of the most important candidate organelles to release von Willebrand factor upon stimulation with desmopressin. However, the presence of functional desmopressin‐specific receptor has not yet been demonstrated on endothelial cells. Experimental evidences are in favour of an indirect pro‐haemostatic effect of desmopressin, but the exact mediator and its cellular origin are largely elusive. Here, we report partially hampered desmopressin response in a splenectomised severe haemophilia A/Beta Thalassemia patient without any genetic variant relevant to his incomplete desmopressin response. To further investigate the role of the spleen in this phenomenon, the release of VWF from desmopressin‐treated human splenic endothelial cells was assessed in vitro. As a result, desmopressin induced the release of VWF from endothelial cells when the cells were co‐cultured with non‐classical (CD14dim/CD16++), but not other subtypes of monocytes or PBMCs. This in vitro study which resembles close proximity of endothelial cells of sinusoids to monocyte reservoir reside in parenchyma of subcapsular red pulp of the spleen sheds a light upon the role of this highly vascularized VWF‐producing organ in driving indirect effect of desmopressin. [ABSTRACT FROM AUTHOR]

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder due to the presence of neutralizing autoantibodies directed against the coagulation factor VIII (FVIII). The reference method to detect and quantify anti-FVIII antibodies is the Bethesda assay (BA), but it presents some limitations such as a lack of sensitivity for low titers of inhibitor and the need for experienced laboratory. A commercially available ELISA detecting anti-FVIII antibodies has demonstrated excellent sensitivity and specificity. The aim of our study was to assess the performance of this ELISA for the detection of anti-FVIII IgG in AHA patients during the follow-up. In total, 11 acquired hemophilia A patients were recruited, and anti-FVIII antibody levels were monitored by BA and ELISA. Anti-FVIII IgG ELISA showed 100% sensitivity and 100% specificity, and it correlated with the BA. Discrepancies observed in 13.3% of cases were consistent with patients' biological evolution. All these data suggest the possible use of anti-FVIII IgG ELISA for both diagnosis and follow-up of AHA patients. [ABSTRACT FROM AUTHOR]

Acquired hemophilia A (AHA) is a rare bleeding disorder, especially in adolescents and young adults (AYAs) attributable to the development of autoantibodies against coagulation factor VIII (FVIII). AHA diagnosis is difficult; patients lack any history of coagulopathy. We report here on an AYA with AHA who responded well to treatment. A 19-year-old woman visited our hospital with painful swelling of the right lower leg. She had no past or familial history of a bleeding disorder. The initial laboratory data revealed a prolonged activated partial thromboplastin time and an uncorrected mixing test result. The FVIII activity was below 1% and the FVIII antibody level 22.4 Bethesda units. She was diagnosed with AHA and treated with recombinant activated coagulation factor VII, activated prothrombin complex concentrates and an oral steroid. After 9 months, FVIII antibody level was negative and the FVIII activity was normalized. AHA is very rare especially in AYAs, but physicians must be suspicious about the disorder and plan specialized coagulation tests to diagnose the disease. An early diagnosis of acquired bleeding disorders should be done for initiating the adequate treatment immediately by both controlling the acute bleeding episode and eliminating FVIII antibodies.

Parth Vashi,1,&ast; Katharine Batt,2,&ast; Robert Klamroth,3 Maria Elisa Mancuso,4 Renata Majewska,5,6 Andreas Tiede,7 Lorenzo Giovanni Mantovani8,9 1US Data Generation and Observational Studies, Bayer Corporation, Whippany, NJ, USA; 2Department of Internal Medicine, Section on Hematology/Medical Oncology, Wake Forest University Baptist Medical Center, Winston-Salem, NC, USA; 3Department for Internal Medicine - Vascular Medicine and Coagulation Disorders, Vivantes Klinikum im Friedrichshain, Berlin, Germany; 4Center for Thrombosis and Hemorrhagic Diseases, IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy; 5HEOR, Creativ-Ceutical, Krakow, Poland; 6Department of Epidemiology, Epidemiology and Preventive Medicine, Jagiellonian University Medical College, Krakow, Poland; 7Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany; 8Center for Public Health Research, University of Milan - Bicocca, Monza, Italy; 9Value-Based Healthcare Unit, IRCCS Multimedica, Sesto San Giovanni, Italy&ast;These authors contributed equally to this workCorrespondence: Renata MajewskaCreativ-Ceutical, ul. Przemys&lstrok;owa 12, Kraków, 30-701, PolandTel +33176704790Email renata.majewska@creativ-ceutical.comPurpose: To assess the efficacy and FVIII consumption of BAY 94-9027 versus N8-GP in prophylaxis in adolescent and adult patients with severe hemophilia A (HA).Patients and Methods: A systematic literature review was conducted to identify studies on the efficacy of BAY-94-9027 and N8-GP for prophylaxis in patients with HA aged ≥ 12 years without a history of inhibitors. Eight studies met systematic literature review inclusion criteria, but only data from PROTECT VIII on BAY 94-9027 and PATHFINDER 2 on N8-GP could be used for an indirect comparison. Matching-adjusted indirect comparison (MAIC) and simulated treatment comparison were performed.Results: No significant differences (unadjusted and adjusted) were observed in the mean annualized bleeding rate (ABR) for any bleed and proportion of patients with zero bleeds when comparing BAY 94-9027 to N8-GP. The adjusted treatment difference [incidence rate ratio (IRR)] in terms of ABR was 1.11 (95% CI, 0.85– 1.44). The odds ratio (OR) of any bleed, measuring the relative effect of BAY 94-9027 versus N8-GP on the proportion of patients with zero bleeds, was 1.03 (95% CI, 0.60– 1.77). FVIII consumption was significantly lower in BAY 94-9027 [mean adjusted difference=− 1292.57 IU/kg/year (95% CI, ‒2152.44 to ‒432.70)]; a 26.7% reduction in consumption of BAY-94-9027. The results of the sensitivity analyses were similar to the main analysis for mean ABRs, percentages of patients with zero bleeds, and significant reduction in rFVIII consumption. For patients on BAY 94-9027 every-5-days and every-7-days, no differences versus every-4-days N8-GP were observed for the mean ABR for any bleed [IRR=0.90 (95% CI, 0.68‒1.20)] and proportion of patients with zero bleeds [OR=1.06 (95% CI, 0.56‒2.02)].Conclusion: BAY 94-9027 prophylaxis demonstrated 26.7% lower annual consumption when compared to N8-GP with similar efficacy in terms of ABR and percentage of patients with zero bleeds.Keywords: BAY 94-9027, N8-GP, prophylaxis, bleed, coagulation factor VIII, adults, factor VIII consumption

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: We examined the associations between haematological and inflammatory variables with future venous thromboembolism (VTE), in 3494 men aged 60–79 years, with no previous history of VTE or myocardial infarction, who were not receiving oral anticoagulants. After a mean follow‐up period of 18 years, there were 149 confirmed cases of fatal or non‐fatal VTE (deep vein thrombosis and/or pulmonary embolism). Among classical cardiovascular risk factors, only obesity and cigarette smoking were associated with VTE risk. After adjustment for age, obesity and smoking, VTE risk was associated with coagulation factor VIII, factor IX, von Willebrand factor (VWF), activated partial thromboplastin time (APTT), and fibrin D‐dimer. Hazard ratios (95% CI) for top to bottom quarters (bottom to top for APTT), were respectively 2.17 (1.37, 3.44), 2.15 (1.30, 3.53), 2.02 (1.27, 3.22), 2.43 (1.47, 4.02) and 3.62 (2.18, 6.08). The 11% of men with both the shortest APTT and highest D‐dimer combined had a 5.02 (2.37, 10.62) higher risk of VTE. VTE risk was not associated with fibrinogen, factor VII or activated protein C resistance; full blood count variables or with inflammatory markers, plasma viscosity, C‐reactive protein or interleukin‐6. The combination of D‐dimer and APTT merits evaluation as an adjunct to VTE risk prediction scores. [ABSTRACT FROM AUTHOR]

Single-chain variable fragments (scFv) are antigen-recognizing variable fragments of antibodies (FV) where both subunits (VL and VH) are connected via an artificial linker. One particular scFv, iKM33, directed against blood coagulation factor VIII (FVIII) was shown to inhibit major FVIII functions and is useful in FVIII research. We aimed to investigate the properties of iKM33 enabled with protease-dependent disintegration. Three variants of iKM33 bearing thrombin cleavage sites within the linker were expressed using a baculovirus system and purified by two-step chromatography. All proteins retained strong binding to FVIII by surface plasmon resonance, and upon thrombin cleavage, dissociated into VL and VH as shown by size-exclusion chromatography. However, in FVIII activity and low-density lipoprotein receptor-related protein 1 binding assays, the thrombin-cleaved iKM33 variants were still inhibitory. In a pull-down assay using an FVIII-affinity sorbent, the isolated VH, a mixture of VL and VH, and intact iKM33 were carried over via FVIII analyzed by electrophoresis. We concluded that the isolated VL and VH assembled into scFv-like heterodimer on FVIII, and the isolated VH alone also bound FVIII. We discuss the potential use of both protease-cleavable scFvs and isolated Fv subunits retaining high affinity to the antigens in various practical applications such as therapeutics, diagnostics, and research. [ABSTRACT FROM AUTHOR]

In recent decades, the use of adult multipotent stem cells has paved the way for the identification of new therapeutic approaches for the treatment of monogenic diseases such as Haemophilia A. Being already studied for regenerative purposes, adipose-derived mesenchymal stem cells (Ad-MSCs) are still poorly considered for Haemophilia A cell therapy and their capacity to produce coagulation factor VIII (FVIII) after proper stimulation and without resorting to gene transfection. In this work, Ad-MSCs were in vitro conditioned towards the endothelial lineage, considered to be responsible for coagulation factor production. The cells were cultured in an inductive medium enriched with endothelial growth factors for up to 21 days. In addition to significantly responding to the chemotactic endothelial stimuli, the cell populations started to form capillary-like structures and up-regulated the expression of specific endothelial markers (CD34, PDGFRα, VEGFR2, VE-cadherin, CD31, and vWF). A dot blot protein study detected the presence of FVIII in culture media collected from both unstimulated and stimulated Ad-MSCs. Remarkably, the activated partial thromboplastin time test demonstrated that the clot formation was accelerated, and FVIII activity was enhanced when FVIII deficient plasma was mixed with culture media from the untreated/stimulated Ad-MSCs. Overall, the collected evidence supported a possible Ad-MSC contribution to HA correction via specific stimulation by the endothelial microenvironment and without any need for gene transfection. [ABSTRACT FROM AUTHOR]

Poor management of either type 1 diabetes or haemophilia A can lead to complications such as organ dysfunction and haemarthropathy. Here, we describe the case of an 8-year-old boy diagnosed with severe haemophilia A shortly after birth. At 2 years old, he was also diagnosed with type 1 diabetes. After six years, the haemophilia treatment was changed from a plasma-derived factor VIII (FVIII) concentrate (octanate®, Octapharma, Lachen, Switzerland) to Nuwiq® (simocotocog alfa, Octapharma, Lachen, Switzerland), a recombinant FVIII (rFVIII) product from a human cell line, which allowed for a personalised treatment schedule that supported good adherence. The dosing regimen could be reduced to two weekly rFVIII infusions. The patient has experienced no spontaneous bleeds since switching to rFVIII and shows no signs of joint damage after over seven years of FVIII prophylaxis. rFVIII was well tolerated, with no treatment-related adverse events observed. This case illustrates the importance of treatment personalisation for young patients and their families managing concomitant diseases.

According to the World Federation of Hemophilia (WFH), there are currently about 400 thousand patients with hemophilia in the world. Severe clinical manifestations of the disease associated with a genetically determined deficiency of blood clotting factor activity require continuous replacement therapy with blood clotting medicines. Long-term use of protein-based medicines often leads to the formation of specific antibodies, which causes a decrease in or loss of efficacy of the medicine or results in severe adverse reactions, including anaphylaxis. Therefore, it is important to search for new optimal approaches to hemophilia treatment, which requires the development of new blood clotting factor products, improvement of the production technology for already authorised products, as well as the use of non-factor products. The aim of the study was to present the results of the analysis of key issues related to the development and characteristics of plasma-derived and recombinant factor VIII products, new approaches to hemophilia A treatment, including the use of non-factor products. The review summarises current data on the etiology, clinical manifestations, and complications of hemophilia A treatment. It provides information on the blood clotting factor products (plasma-derived and recombinant) used as replacement therapy. It also provides information on advanced research projects for the development of new biotechnology-derived products which have good prospects of successful clinical use.

Osteoporosis is a clinically prevalent comorbidity in patients with hemophilia. A preventive effect of kefir peptides (KPs) on postmenopausal osteoporosis has been proved. The aim of this study was to evaluate the therapeutic effect of KPs for the treatment of osteoporosis in coagulation factor VIII (FVIII) gene knockout mice (F8KO), a model of hemophilia A. In this study, male F8KO mice at 20 weeks of age were orally administered different doses of KPs for 8 weeks. The therapeutic effects of KPs were shown in the femoral trabeculae and the 4th lumbar vertebrae, which increased the trabecular bone mineral density (BMD), bone volume (Tb.BV/TV), and trabecular number (Tb.N) and decreased the trabecular separation (Tb.Sp), and they were also observed in the femoral cortical bones, in which the mechanical properties were enhanced in a dose-dependent manner. Characterization of receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), and interleukin 6 (IL-6) demonstrated that the serum RANKL/OPG ratio and IL-6 levels were significantly decreased in the F8KO mice after the KP treatment. Tartrate-resistant acid phosphatase (TRAP) staining of mature osteoclasts indicated that the therapeutic effect of KPs in F8KO mice was associated with the functions of KPs to inhibit RANKL-induced osteoclastogenesis by reducing serum RANKL/OPG ratio and IL-6 secretion. The present study is the first to address the potentials of KPs for the treatment of hemophilia-induced osteoporosis in mice and it also provides useful information for the application of KPs as a complementary therapy for the treatment of osteoporosis in hemophilic patients.

Aims: Population pharmacokinetic (PK) models are increasingly applied to perform individualized dosing of factor VIII (FVIII) concentrates in haemophilia A patients. To guarantee accurate performance of a population PK model in dose individualization, validation studies are of importance. However, external validation of population PK models requires independent data sets and is, therefore, seldomly performed. Therefore, this study aimed to validate a previously published population PK model for FVIII concentrates administrated perioperatively. Methods: A previously published population PK model for FVIII concentrate during surgery was validated using independent data from 87 children with severe haemophilia A with a median (range) age of 2.6 years (0.03–15.2) and body weight of 14 kg (4–57). First, the predictive performance of the previous model was evaluated with MAP Bayesian analysis using NONMEM v7.4. Subsequently, the model parameters were (re)estimated using a combined dataset consisting of the previous modelling data and the data available for the external validation. Results: The previous model underpredicted the measured FVIII levels with a median of 0.17 IU mL−1. Combining the new, independent and original data, a dataset comprising 206 patients with a mean age of 7.8 years (0.03–77.6) and body weight of 30 kg (4–111) was obtained. Population PK modelling provided estimates for CL, V1, V2, and Q: 171 mL h−1 68 kg−1, 2930 mL 68 kg−1, 1810 mL 68 kg−1, and 172 mL h−1 68 kg−1, respectively. This model adequately described all collected FVIII levels, with a slight median overprediction of 0.02 IU mL−1. Conclusions: This study emphasizes the importance of external validation of population PK models using real‐life data. [ABSTRACT FROM AUTHOR]

It is well known that canine factor VIII (cFVIII) has a higher specific activity than does human FVIII (hFVIII), and it has been previously demonstrated that cFVIII light chain is able to enhance hFVIII activity. The goal of this study was to first determine which amino acids in cFVIII light chain were responsible for enhancing hFVIII activity, and second to use these amino acids to develop a hFVIII variant with enhanced functional activity. We systemically screened segments of cFVIII light chain by testing an array of human-canine light chain hybrids and found that canine amino acids 1857–2147 were key to this enhancement. Each canine amino acid within this span was screened individually using a negative selection method, which led to the identification of 12 aa (JF12) in the FVIII light chain that could enhance activity. Substitution of the corresponding 12 aa into hFVIII (hFVIIIJF12BDD) elevated the specific activity profile in vitro. Furthermore, hFVIIIJF12BDD expressed an in vivo-displayed increased coagulation activity compared to wild-type, while maintaining normal secretion efficiency. In conclusion, we identified the amino acids in cFVIII that are the key determinants for higher specific activity and may be the basis for future development of therapeutic treatments for hemophilia A.

Snake venoms, comprising a complex array of protein-rich components, an important part of which are snake venom metalloproteinases (SVMPs). These SVMPs, which are predominantly isolated from viperid venoms, are integral to the pathology of snakebites. However, SVMPs derived from elapid venoms have not been extensively explored, and only a handful of SVMPs have been characterized to date. Atrase A, a nonhemorrhagic P-III class metalloproteinase from Naja atra venom, exhibits weak proteolytic activity against fibrinogen in vitro but has pronounced anticoagulant effects in vivo. This contrast spurred investigations into its anticoagulant mechanisms. Research findings indicate that atrase A notably extends the activated partial thromboplastin time, diminishes fibrinogen levels, and impedes platelet aggregation. The anticoagulant action of atrase A primarily involves inhibiting coagulation factor VIII and activating the endogenous fibrinolytic system, which in turn lowers fibrinogen levels. Additionally, its effect on platelet aggregation further contributes to its anticoagulant profile. This study unveils a novel anticoagulant mechanism of atrase A, significantly enriching the understanding of the roles of cobra venom metalloproteinases in snake venom. Furthermore, these findings underscore the potential of atrase A as a novel anticoagulant drug, offering insights into the functional evolutions of cobra venom metalloproteinases., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Protobothrops mucrosquamatus , also known as the Taiwan Habu, is a venomous snake prevalent in Taiwan. It is accountable for most snakebites in the region. The toxin of the Taiwan Habu has significant hemorrhagic potential. However, patients bitten by this snake often suffer more local injuries than systemic ones. This report presents two cases of individuals bitten by the Taiwan Habu who subsequently experienced thromboembolism. In the first case, an 88-year-old male, bitten on his fourth toe, suffered a cerebral infarction 32 hours post-bite. In the second case, an 82-year-old female, bitten on her ankle, experienced cardiac arrest 19 hours later. Both patients promptly received antivenom and showed no signs of coagulopathy either before or after the snakebite. However, elevated coagulation factor VIII levels were observed in the first case. Our aim is to understand the mechanism behind these thromboembolic events. This report emphasizes the unusually high level of coagulation factor VIIIa and highlights the need for further investigation into the mechanisms involved. Consequently, physicians should assess the risk of thromboembolic events in snakebite patients by evaluating coagulation factors during treatment. [Display omitted] • Taiwan Habu bites rarely result in systemic thromboembolic events. • High levels of coagulation factor VIIIa, possibly caused by snake venom or snakebite stress. • Monitoring coagulation levels is important when managing snakebite patients. [ABSTRACT FROM AUTHOR]

Single-chain variable fragments (scFv) are antigen-recognizing variable fragments of antibodies (FV) where both subunits (VL and VH) are connected via an artificial linker. One particular scFv, iKM33, directed against blood coagulation factor VIII (FVIII) was shown to inhibit major FVIII functions and is useful in FVIII research. We aimed to investigate the properties of iKM33 enabled with protease-dependent disintegration. Three variants of iKM33 bearing thrombin cleavage sites within the linker were expressed using a baculovirus system and purified by two-step chromatography. All proteins retained strong binding to FVIII by surface plasmon resonance, and upon thrombin cleavage, dissociated into VL and VH as shown by size-exclusion chromatography. However, in FVIII activity and low-density lipoprotein receptor-related protein 1 binding assays, the thrombin-cleaved iKM33 variants were still inhibitory. In a pull-down assay using an FVIII-affinity sorbent, the isolated VH, a mixture of VL and VH, and intact iKM33 were carried over via FVIII analyzed by electrophoresis. We concluded that the isolated VL and VH assembled into scFv-like heterodimer on FVIII, and the isolated VH alone also bound FVIII. We discuss the potential use of both protease-cleavable scFvs and isolated Fv subunits retaining high affinity to the antigens in various practical applications such as therapeutics, diagnostics, and research.

In recent decades, the use of adult multipotent stem cells has paved the way for the identification of new therapeutic approaches for the treatment of monogenic diseases such as Haemophilia A. Being already studied for regenerative purposes, adipose-derived mesenchymal stem cells (Ad-MSCs) are still poorly considered for Haemophilia A cell therapy and their capacity to produce coagulation factor VIII (FVIII) after proper stimulation and without resorting to gene transfection. In this work, Ad-MSCs were in vitro conditioned towards the endothelial lineage, considered to be responsible for coagulation factor production. The cells were cultured in an inductive medium enriched with endothelial growth factors for up to 21 days. In addition to significantly responding to the chemotactic endothelial stimuli, the cell populations started to form capillary-like structures and up-regulated the expression of specific endothelial markers (CD34, PDGFRα, VEGFR2, VE-cadherin, CD31, and vWF). A dot blot protein study detected the presence of FVIII in culture media collected from both unstimulated and stimulated Ad-MSCs. Remarkably, the activated partial thromboplastin time test demonstrated that the clot formation was accelerated, and FVIII activity was enhanced when FVIII deficient plasma was mixed with culture media from the untreated/stimulated Ad-MSCs. Overall, the collected evidence supported a possible Ad-MSC contribution to HA correction via specific stimulation by the endothelial microenvironment and without any need for gene transfection.

Myocardial infarction is a life-threatening emergency with a high mortality rate. A high plasma level of factor VIII is an established risk for both arterial and venous thrombotic events. In this mini-review, we report the case of a 41-year-old woman without cardiovascular risk factors or a previous history of thrombotic events, admitted for ST-elevation myocardial infarction, in whom, coronary angiography showed a thrombotic occlusion in the left anterior descending artery. The patient underwent primary percutaneous coronary intervention (PCI), with the administration of GPIIB-IIIA antagonist, then, a pre-dilation with a semi-compliant balloon-catheter, followed by implantation of 2 stents. The etiological assessment revealed a high level of coagulation factor VIII (FVIII). She underwent anticoagulation therapy (with acenocoumarol) with well-controlled international normalised ratio (INR).

Poor management of either type 1 diabetes or haemophilia A can lead to complications such as organ dysfunction and haemarthropathy. Here, we describe the case of an 8-year-old boy diagnosed with severe haemophilia A shortly after birth. At 2 years old, he was also diagnosed with type 1 diabetes. After six years, the haemophilia treatment was changed from a plasma-derived factor VIII (FVIII) concentrate (octanate®, Octapharma, Lachen, Switzerland) to Nuwiq® (simocotocog alfa, Octapharma, Lachen, Switzerland), a recombinant FVIII (rFVIII) product from a human cell line, which allowed for a personalised treatment schedule that supported good adherence. The dosing regimen could be reduced to two weekly rFVIII infusions. The patient has experienced no spontaneous bleeds since switching to rFVIII and shows no signs of joint damage after over seven years of FVIII prophylaxis. rFVIII was well tolerated, with no treatment-related adverse events observed. This case illustrates the importance of treatment personalisation for young patients and their families managing concomitant diseases. [ABSTRACT FROM AUTHOR]

Von Willebrand factor (VWF) levels are regulated by genetic and acquired factors. The acquired factors are mostly related to age and could be mediators of the age effect on VWF levels. To disentangle the role of genetic (sex, blood group) and acquired factors (comorbidities, body mass index, reduced kidney function, hormone use, and inflammation) in regulating von Willebrand factor antigen (VWF:Ag) and factor VIII activity (FVIII:C) levels in the normal population. Analysis were performed in a large population sample (2923 individuals) from the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA study), after exclusion of individuals with active cancer and women who were pregnant or within nine months postpartum. The increase of VWF:Ag and FVIII:C with age was evaluated by linear regression after the age of 40 years. Analyses were adjusted for acquired factors and stratified for sex and blood group. VWF:Ag and FVIII:C increased with age: increase per decade of age for VWF:Ag 18 IU/dL (95%CI 15–20) and for FVIII:C 12 IU/dL (95%CI 10–14). After adjustment for acquired factors, the increase per decade was 13 IU/dL (95%CI 10–16) for VWF:Ag and 9 IU/dL (95%CI 6–11) for FVIII:C. The stratified analysis for blood group showed higher increase in the non-O group, but these differences were annulled after adjustment for acquired factors. VWF:Ag and FVIII:C increase with age. Carriers of blood group non-O present a steeper increase of VWF:Ag and FVIII:C with age, that is mediated by acquired factors. • Von Willebrand factor (VWF) and factor VIII (FVIII) increase with age. • VWF and FVIII levels are regulated by genetic and acquired factors. • VWF and FVIII increase with age is partially mediated by acquired factors. • Blood group non-O shows a higher increase of VWF mediated by acquired factors. [ABSTRACT FROM AUTHOR]

Myocardial infarction is a life-threatening emergency with a high mortality rate. A high plasma level of factor VIII is an established risk for both arterial and venous thrombotic events. In this mini-review, we report the case of a 41-year-old woman without cardiovascular risk factors or a previous history of thrombotic events, admitted for ST-elevation myocardial infarction, in whom coronary angiography showed a thrombotic occlusion in the left anterior descending artery. The patient underwent primary percutaneous coronary intervention (PCI), with GPIIB-IIIA antagonist, then, a pre-dilation with a semi-compliant balloon catheter, followed by implantation of 2 stents. The etiological assessment revealed a high level of coagulation factor VIII (FVIII). She underwent anticoagulation therapy (with acenocoumarol) with well-controlled international normalised ratio (INR). [ABSTRACT FROM AUTHOR]

Acquired hemophilia A is a rare condition characterized by the development of autoantibodies against coagulation factor VIII. It often initially presents as serious bleeding in the absence of risk factors and carries high morbidity and mortality if not diagnosed early. Due to its rare nature, data is limited, and guidelines are primarily based on expert opinion. Here we present a case of an elderly patient with severe gastrointestinal bleeding found to have activated partial thromboplastin times, plasma mixing studies, and coagulation factor activity levels consistent with acquired hemophilia A. We hope to bring awareness of this rare disease and promote its consideration in the differential of unexpected bleeding to improve safety outcomes., (© 2024 Greater Baltimore Medical Center.)

Hemophilia A (HA) is a F8 gene mutational disorder resulting in deficiency or dysfunctional FVIII protein. However, surprisingly, in few cases, HA is manifested even without mutations in F8. To understand this anomaly, we recently sequenced microRNAs (miRNAs) of two patients with mild and moderate HA with no F8 gene mutations and selected two highly expressing miRNAs, miR-374b-5p and miR-30c-5p, from the pool to explain the FVIII deficiency that could be mediated by miRNA-based F8/FVIII suppression. In this report, an established orthogonal in vivo RNA-affinity purification approach was utilized to directly identify a group of F8-interacting miRNAs and we tested them for F8/FVIII suppression. From this pool, two miRNAs, miR-19b-3p and miR-186-5p, were found to be upregulated in a severe HA patient with a mutation in the F8 coding sequence and two HA patients without mutations in the F8 coding sequence were selected to demonstrate their role in F8 gene expression regulation in mammalian cells. Overall, these results provide further evidence for the hypothesis that by targeting the 3′UTR of F8, miRNAs can modulate FVIII protein levels. This mechanism could either be the primary cause of HA in patients who lack F8 mutations or control the severity of the disease in patients with F8 mutations.

Dorothy M Adcock,1 Mazi Rasulnia,2 Natalia Holot,3 David L Cooper3 1Laboratory Corporation of America Holdings, Burlington, NC, 2M Consulting LLC, Birmingham, AL, 3Clinical, Medical, and Regulatory Affairs,Novo Nordisk Inc., Plainsboro, NJ, USA Introduction: Diagnosis and management of hemophilia require accurate and precise measurements of factor activity levels. Activity is traditionally measured via one-stage (OS) clot-based assay; however, chromogenic substrate (CS) assays may be needed for certain cases. A survey was performed to understand assay-related knowledge gaps among hematologists and laboratory professionals. Methods: Separate web-based surveys were administered to hematologists who manage hemophilia and to laboratory professionals and queried practice patterns, knowledge of/attitudes toward CS assays, and interest in continuing education. Results: A total of 51 hematologists participated in this study; 67% managed hemophilia patients for ≥10 years and 24% were affiliated with a hemophilia treatment center (HTC). Most (80%) stated familiarity with general assay interpretation. Majorities of non-HTC and HTC respondents agreed that CS assays are more accurate than OS assays (62%/67%), although non-HTC hematologists indicated less understanding of when to order a CS assay (49%/67%). Fewer non-HTC respondents expressed concerns regarding the reliability of OS assays for diagnosis (38%/67%) and monitoring (38%/75%). Most (80%) expressed an interest in factor assay education, especially on available assays, efficacy, and best practices (39%). A total of 57 laboratory professionals participated, averaging 10 years in their current position; most (88%) were hospital based. More performed OS (72%) than CS (10%) or both (17%) assays; only 11% reported confidence with the interpretation of CS results. Few expressed concerns regarding the reliability of OS for diagnosis (9%) or monitoring (12%). Reported barriers to CS use included infrequent need (68%), lack of US Food and Drug Administration (FDA) approval (61%), and need for validation work (56%). Most (70%) were interested in CS assay education; top interests included advantages over traditional assays, general information on CS assays, and indications for testing (each 18%). Conclusion: Future educational efforts may focus on limitations of OS assays, indications for CS assay diagnosis/monitoring, and support for clinic-laboratory dialog. Keywords: hemophilia, factor activity assay, chromogenic substrate assay, coagulation factor VIII, coagulation factor IX, monitoring

In recent years, several modified recombinant factor (F) VIII and FIX therapeutics with extended half-life have been licensed internationally for the treatment of haemophilia. Safe and effective use of these products requires monitoring of factor activity in patient plasma. The potency of all FVIII and FIX products is currently assigned in International Units (IU) which anchors the relationship between potency labelling, dosing and clinical monitoring. However, varying degrees of discrepancies in factor activity assays are observed between and within the factor activity analytical methods (one-stage clotting and chromogenic), when measuring these modified products against plasma and plasma-derived (concentrate) International Standards (IS) or in-house reference standard traceable to the IS. Availability of product-specific reference reagents would mitigate assay discrepancies, facilitate independent testing of assay methods and reagents, and ensure long-term continuity of the IU related to each product. A hearing meeting was organised by the WHO to discuss the requirements for product-specific reference materials for these products and whether these reference materials should be produced by the WHO. Advantages and disadvantages of product-specific reference materials were identified and discussed. • Several modified recombinant factor (F) VIII and FIX therapeutics were licensed. • Factor activity assay discrepancies occur with primary international standards. • This WHO hearing discussed the requirements for product-specific reference materials. • The WHO is responsible mainly for providing primary standards, not secondary ones. • Pros and cons of product-specific reference materials were identified and discussed. [ABSTRACT FROM AUTHOR]

The paper describes 4 clinical cases of thrombotic events (pulmonary embolism, deep vein thrombophlebitis, acute myocardial infarction, ischemic stroke) that have occurred in patients with hemophilia. It discusses the possible causes of their development and methods for their prevention and treatment. Controlled natural hypocoagulation, in which the dose of an administered deficient factor decreases to such an extent that in order to maintain the safe level of hypocoagulation (plasma factor activity is 15—20%; activated partial thromboplastin time is 1.5—2 times normal values), is proposed as one of the treatment options.

Objective: To analyze the results of activated partial thromboplastin time (APTT) mixing test in coagulation factor Ⅷ inhibitor-positive hemophilia patients, so as to increase the value of APTT mixing test in the screen of factor Ⅷ inhibitor., Methods: Eighty plasmas samples with different titers of coagulation factor Ⅷ inhibitors had been collected and diluted for routine immediate APTT mixing test and at 37 ℃ 2 hours incubation APTT mixing test. Fifteen samples were selected for immediate and normal temperature incubation for 15 min, 30min, 1 hour, 2 hours and 37 ℃ for 30 min, 1 hour, 2 hours APTT mixing test., Results: The results of APTT mixing test were significantly correlated with the titers of coagulation factor Ⅷ inhibitors. The ROC curve result showed that the best diagnostic cut-off value for 2 hours incubation APTT mixing test at 37 ℃ to determine the presence or absence of coagulation factor Ⅷ inhibitors was 43.8 s (sensitivity and specificity was 85.90% and 100%, respectively), while the best diagnostic cut-off value for distinguishing high-titer and low-titer Ⅷ inhibitors was 52.4 s (sensitivity and specificity was 98.18% and 95.65%, respectively). The critical coagulation factor Ⅷ inhibitor titer that could not be corrected by immediate APTT was 5.14 BU/ml, while that could not be corrected by 37 ℃ 2 hours incubation APTT was 1.31 BU/ml. Paired samples t -test was performed on the APTT mixing test results at different times and temperatures, and the differences were statistically significant ( P < 0.05)., Conclusions: The APTT mixing test can be used as a screening index for coagulation factor Ⅷ inhibitors. APTT mixing test result shows a significant time-temperature dependence with lower titers of coagulation factor Ⅷ inhibitor. Patients with hemophilia who cannot be corrected by immediate APTT mixing test should be alert to the possibility of high titer of coagulation factor Ⅷ.

Background: Coagulation factor VIII (FVIII) and von Willebrand factor (VWF) circulate as a noncovalent complex, but each has its distinct functions. Binding of FVIII to VWF results in a prolongation of FVIII's half-life in circulation and modulates FVIII's immunogenicity during hemophilia therapy. However, the biological effect of FVIII and VWF interaction on VWF homeostasis is not fully understood., Objectives: To determine the effect of FVIII in VWF proteolysis and homeostasis in vivo., Methods: Mouse models, recombinant FVIII infusion, and patients with hemophilia A on a high dose FVIII for immune tolerance induction therapy or emicizumab for bleeding symptoms were included to address this question., Results: An intravenous infusion of a recombinant B-domain less FVIII (BDD-FVIII) (40 and 160 μg/kg) into wild-type mice significantly reduced plasma VWF multimer sizes and its antigen levels; an infusion of a high but not low dose of BDD-FVIII into Adamts13 +/- and Adamts13 -/- mice also significantly reduced the size of VWF multimers. However, plasma levels of VWF antigen remained unchanged following administration of any dose BDD-FVIII into Adamts13 -/- mice, suggesting partial ADAMTS-13 dependency in FVIII-augmented VWF degradation. Moreover, persistent expression of BDD-FVIII at ∼50 to 250 U/dL via AAV8 vector in hemophilia A mice also resulted in a significant reduction of plasma VWF multimer sizes and antigen levels. Finally, the sizes of plasma VWF multimers were significantly reduced in patients with hemophilia A who received a dose of recombinant or plasma-derived FVIII for immune tolerance induction therapy., Conclusion: Our results demonstrate the pivotal role of FVIII as a cofactor regulating VWF proteolysis and homeostasis under various (patho)physiological conditions., Competing Interests: Declaration of competing interests X.L.Z. is a consultant and a member of the advisory boards for Alexion, Apollo, GC Biopharma, Sanofi, Stago, and Takeda. X.L.Z. is also the cofounder of Clotsolution. W.C. holds equity in Ivygen. All other authors have declared no relevant conflict., (Copyright © 2023 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Hemophilia A is a genetic disorder through which patients suffer from recurrent bleeding. This can be caused by a defect in human plasma coagulation factor VIII. High incidence of FVIII inhibitors in some severe hemophilia A patients after FVIII therapy is a considerable complication. Determination of good predictive factors can improve the safety of this treatment. HLA-II have been shown as a predictive element for inhibitor development. The goal of this study is to determine the association between HLA-DRB1*15:03, HLA-DRB1*11 and HLA-DRB1*01:01 alleles and FVIII inhibitors in severe hemophilia A patients in Iran. HLA-DRB1 genotyping was performed using Multiplex sequences Specific Primers (PCR-SSP) in two groups of severe hemophilia A patients comprising 51 and 50 individuals with and without FVIII inhibitors respectively. The levels of inhibitor were determined through Nijmegen-modified Bethesda assay. HLA-DRB1 allele frequencies were compared between groups by using multiple logistic regression models. HLA-DRB1*01:01 allele frequency was significantly higher in patients without inhibitor OR adj : 2.7 (95%CI: 1.08, 6.97; P = 0.034). There wasn't any statistically significant difference in HLA-DRB1*11 allele frequency between groups OR adj : 0.7 (95%CI: 0.27, 1.82; P = 0.47). There was no connection between HLA-DRB1*15:03 and inhibitor development OR adj : 0.94 (95%CI: 0.38, 2.35; P = 0.94). An association between HLA-DRB1*01:01 and paucity of FVIII inhibitor showed that this allele has probably a protective effect in severe hemophilia A patients in Iran. Determination of the predictive and protective alleles are beneficial in pre-treatment activities and decrease the risk of unsuccessful therapy with FVIII in each population. [ABSTRACT FROM AUTHOR]

Background: Accurate determination of coagulation factor VIII activity (FVIII:C) is essential for effective and safe FVIII replacement therapy. FVIII:C can be measured by one‐stage and chromogenic substrate assays (OSAs and CSAs, respectively); however, there is significant interlaboratory and interassay variability. Aims: This international comparative field study characterized the behaviour of OSAs and CSAs used in routine laboratory practice to measure the activity of Nuwiq® (human‐cl rhFVIII, simoctocog alfa), a fourth‐generation recombinant human FVIII produced in a human cell line. Methods: FVIII‐deficient plasma was spiked with Nuwiq® or Advate® at 1, 5, 30 and 100 international units (IU)/dL. Participating laboratories analysed the samples using their routine procedures and equipment. Accuracy, inter‐ and intralaboratory variation, CSA:OSA ratio and the impact of different OSA and CSA reagents were assessed. Results: Forty‐nine laboratories from 9 countries provided results. Mean absolute FVIII:C was comparable for both products at all concentrations with both OSA and CSA, with interproduct ratios (Nuwiq®:Advate®) of 1.02‐1.13. Mean recoveries ranged from 97% to 191% for Nuwiq®, and from 93% to 172% for Advate®, with higher recoveries at lower concentrations. Subgroup analyses by OSA and CSA reagents showed minor variations depending on reagents, but no marked differences between the two products. CSA:OSA ratios based on overall means ranged from 0.99 to 1.17 for Nuwiq® and from 1.01 to 1.17 for Advate®. Conclusions: Both OSAs and CSAs are suitable for the measurement of FVIII:C of Nuwiq® in routine laboratory practice, without the need for a product‐specific reference standard. [ABSTRACT FROM AUTHOR]

Blood coagulation factor VIII (FVIII) can bind calcium ions and ion-protein interactions appear central importance for both their structure and function in coagulation cascade. However, the mechanism and details of how calcium dependent structure change of proteins to fulfill their function remain to be fully defined. In this work, PeakForce Quantitative Nanomechanics (PF-QNM) mode atomic force microscopy (AFM) was used to map the topography and mechanical properties of FVIII with single protein resolution under different calcium concentrations. The obtained nanomechanical spectroscopy showed that calcium ions play dual roles in the chain association and structural flexibility of FVIII. Low concentration of calcium ions prefer to bind isolated chains and increase their mechanical properties, whereas they link the heavy and light chains to keep the protein re-association under higher ions concentration. Our results provide a novel insight into the mechanistic details of the metal ions on the stability and function of blood clotting proteins. Image 1 • Atomic force microscopy-based nanomechanical spectroscopy of proteins has been developed. • Topography and mechanical properties of blood clotting factor VIII was measured with single protein resolution. • Calcium ions play dual roles in the chain association and structural flexibility of factor VIII. [ABSTRACT FROM AUTHOR]

Von Willebrand factor (VWF) is a multimeric plasma glycoprotein that plays a central role in the initiation of blood coagulation. Through interactions between its specific functional domains, the vascular wall, coagulation factor VIII, and platelet receptors, VWF maintains hemostasis by binding to platelets and delivering factor VIII to the sites of vascular injury. In the healthy human population, plasma VWF levels vary widely. The important role of VWF is illustrated by individuals at the extremes of the normal distribution of plasma VWF concentrations where individuals with low VWF levels are more likely to present with mucocutaneous bleeding. Conversely, people with high VWF levels are at higher risk for venous thromboembolic disease, stroke, and coronary artery disease. This report will summarize recent advances in our understanding of environmental influences and the genetic control of VWF plasma variation in healthy and symptomatic populations and will also highlight the unanswered questions that are currently driving this field of study.