Genetic determinants of VWF clearance and FVIII binding modify FVIII pharmacokinetics in pediatric hemophilia A patients

Binding Promiscuity of Therapeutic Factor VIII

The binding promiscuity of proteins defines their ability to indiscriminately bind multiple unrelated molecules. Binding promiscuity is implicated, at least in part, in the off-target reactivity, nonspecific biodistribution, immunogenicity, and/or short half-life of potentially efficacious protein drugs, thus affecting their clinical use. In this review, we discuss the current evidence for the binding promiscuity of factor VIII (FVIII), a protein used for the treatment of hemophilia A, which displays poor pharmacokinetics, and elevated immunogenicity. We summarize the different canonical and noncanonical interactions that FVIII may establish in the circulation and that could be responsible for its therapeutic liabilities. We also provide information suggesting that the FVIII light chain, and especially its C1 and C2 domains, could play an important role in the binding promiscuity. We believe that the knowledge accumulated over years of FVIII usage could be exploited for the development of strategies to predict protein binding promiscuity and therefore anticipate drug efficacy and toxicity. This would open a mutational space to reduce the binding promiscuity of emerging protein drugs while conserving their therapeutic potency.

Variant mapping using mass spectrometry-based proteotyping as a diagnostic tool in von Willebrand disease

BACKGROUND

von Willebrand disease (VWD) is the most common inherited bleeding disorder, characterized by either partial or complete von Willebrand factor (VWF) deficiency or by the occurrence of VWF proteoforms of altered functionality. The gene encoding VWF is highly polymorphic, giving rise to a variety of proteoforms with varying plasma concentrations and clinical significance.

OBJECTIVES

To address this complexity, we translated genomic variation in VWF to corresponding VWF proteoforms circulating in blood.

METHODS

VWF was characterized in VWD patients (n = 64) participating in the Willebrand in the Netherlands study by conventional laboratory testing, DNA sequencing and complementary discovery, and targeted mass spectrometry-based plasma proteomic strategies.

RESULTS

Unbiased plasma profiling combined with immune enrichment of VWF verified VWF and its binding partner factor VIII as key determinants of VWD and revealed a remarkable heterogeneity in VWF amino acid sequence coverage among patients. Subsequent VWF proteotyping enabled identification of both polymorphisms (eg, p.Thr789Ala, p.Gln852Arg, and p.Thr1381Ala), as well as pathogenic variants (n = 16) along with their corresponding canonical sequences. Targeted proteomics using stable isotope-labeled peptides confirmed unbiased proteotyping for 5 selected variants and suggested differential proteoform quantities in plasma. The variant-to-wild-type peptide ratio was determined in 6 type 2B patients heterozygous for p.Arg1306Trp, confirming the relatively low proteoform concentration of the pathogenic variant. The elevated VWF propeptide/VWF ratio indicated increased clearance of specific VWF proteoforms.

CONCLUSION

This study highlights how VWF proteotyping from plasma could be the first step to bridge the gap between genotyping and functional testing in VWD.

Immunogenicity profile of rurioctocog alfa pegol in previously treated patients with severe congenital hemophilia A

ABSTRACT

Rurioctocog alfa pegol is an extended-half-life full-length recombinant factor VIII (FVIII) bound to 20-kDa polyethylene glycol (PEG) that has been shown to be well tolerated and efficacious in the treatment and prevention of bleeding events in previously treated patients with severe hemophilia A. Here, we present a comprehensive analysis of immunogenicity data collected during 6 clinical studies of rurioctocog alfa pegol, including a total of 360 unique previously treated patients with severe hemophilia A. The analysis included treatment-emerging FVIII-neutralizing antibodies (FVIII inhibitors); preexisting and treatment-emerging antibodies binding to FVIII, PEG-FVIII, or PEG; and treatment-emerging antibodies binding to Chinese hamster ovary host cell proteins. Moreover, the potential association between the presence of these binding antibodies and adverse events (AEs) observed in patients was investigated, and the potential impact of these antibodies on the incremental recovery of rurioctocog alfa pegol in patients was analyzed. Overall, the data indicate that rurioctocog alfa pegol is not associated with any unexpected immunogenicity characteristics. Of 360 patients, 1 patient developed a transient FVIII inhibitor with a titer of 0.6 Bethesda units per mL, which was not associated with any serious AEs. Antibodies binding to FVIII, PEG-FVIII, or PEG were not detected at the time when the inhibitor was present. Moreover, 54 of 360 patients either entered the clinical studies with preexisting binding antibodies or developed these antibodies after exposure to rurioctocog alfa pegol. These antibodies were transient in most patients and did not show any causal relationship to either AEs or spontaneous bleeding episodes.

Dynamic molecular choreography induced by acute heat exposure in human males: a longitudinal multi-omics profiling study

Introduction

Extreme heat events caused by occupational exposure and heat waves are becoming more common. However, the molecular changes underlying the response to heat exposure in humans remain to be elucidated.

Methods

This study used longitudinal multi-omics profiling to assess the impact of acute heat exposure (50°C for 30 min) in 24 subjects from a mine rescue team. Intravenous blood samples were collected before acute heat exposure (baseline) and at 5 min, 30 min, 1 h, and 24 h after acute heat exposure (recovery). In-depth multi-omics profiling was performed on each sample, including plasma proteomics (untargeted) and metabolomics (untargeted).

Results

After data curation and annotation, the final dataset contained 2,473 analytes, including 478 proteins and 1995 metabolites. Time-series analysis unveiled an orchestrated molecular choreography of changes involving the immune response, coagulation, acid-base balance, oxidative stress, cytoskeleton, and energy metabolism. Further analysis through protein-protein interactions and network analysis revealed potential regulators of acute heat exposure. Moreover, novel blood-based analytes that predicted change in cardiopulmonary function after acute heat exposure were identified.

Conclusion

This study provided a comprehensive investigation of the dynamic molecular changes that underlie the complex physiological processes that occur in human males who undergo heat exposure. Our findings will help health impact assessment of extreme high temperature and inspire future mechanistic and clinical studies.

Comparison of different machine learning classification models for predicting deep vein thrombosis in lower extremity fractures

Deep vein thrombosis (DVT) is a common complication in patients with lower extremity fractures. Once it occurs, it will seriously affect the quality of life and postoperative recovery of patients. Therefore, early prediction and prevention of DVT can effectively improve the prognosis of patients. This study constructed different machine learning models to explore their effectiveness in predicting DVT. Five prediction models were applied to the study, including Extreme Gradient Boosting (XGBoost) model, Logistic Regression (LR) model, RandomForest (RF) model, Multilayer Perceptron (MLP) model, and Support Vector Machine (SVM) model. Afterwards, the performance of the obtained prediction models was evaluated by area under the curve (AUC), accuracy, sensitivity, specificity, F1 score, and Kappa. The prediction performances of the models based on machine learning are as follows: XGBoost model (AUC = 0.979, accuracy = 0.931), LR model (AUC = 0.821, accuracy = 0.758), RF model (AUC = 0.970, accuracy = 0.921), MLP model (AUC = 0.830, accuracy = 0.756), SVM model (AUC = 0.713, accuracy = 0.661). On our data set, the XGBoost model has the best performance. However, the model still needs external verification research before clinical application.

Impact of the blood group on postoperative CRP and leukocyte levels after primary total hip and knee arthroplasty

BACKGROUND

C-reactive protein (CRP)- and leukocyte levels are common parameters to evaluate the inflammatory response after orthopaedic surgery and rule out infectious complications. Nevertheless, both parameters are vulnerable to disturbing biases and therefore leave room for interpretation.

OBJECTIVE

Since blood groups are repeatedly discussed to influence inflammatory response, our aim was to observe their impact on CRP and leukocyte levels after total hip and knee arthroplasty (THA/TKA).

METHODS

Short term postoperative CRP and leukocyte levels of 987 patients, who received either primary TKH (n= 479) or THA (n= 508), were retrospectively correlated with their blood group. ABO, Rhesus and a combination of both blood groups were differentiated.

RESULTS

CRP levels after TKA were significantly higher in blood type AB than in type A and O on day 2-4 and also than in type A on day 6-8. Leukocyte levels after THA were significantly higher in blood group type O than in type A on day 6-8 while still remaining in an apathological range. We observed no significant differences between Rhesus types and Rhesus types and CRP or leukocyte levels.

CONCLUSION

We observed significantly increased CRP levels after TKA in patients with blood group AB. Since the elevated CRP levels do not account for early periprosthetic infection, surgeons should include this variation in their postoperative evaluation.

Pharmacokinetics of recombinant factor VIII in adults with severe hemophilia A: fixed-sequence single-dose study of octocog alfa, rurioctocog alfa pegol, and efanesoctocog alfa

Background

Efanesoctocog alfa is a new class of factor (F) VIII replacement therapy designed to provide high sustained factor levels for longer by overcoming the von Willebrand factor half-life ceiling.

Objectives

To assess the pharmacokinetics and safety of standard half-life (octocog alfa) and extended half-life (rurioctocog alfa pegol) FVIIIs and efanesoctocog alfa.

Methods

This phase 1 study (NCT05042440; EudraCT 2021-000228-37) enrolled previously treated adult men with severe hemophilia A. Patients received sequential single 50-IU/kg doses of octocog alfa, rurioctocog alfa pegol, and efanesoctocog alfa after appropriate washout periods between each dose.

Results

Thirteen participants were enrolled. Geometric mean elimination half-life of octocog alfa, rurioctocog alfa pegol, and efanesoctocog alfa was 11.0, 15.4, and 43.3 hours, respectively, and area under the FVIII activity-time curve was 1670, 2820, and 10,100 IU × h/dL, respectively. Efanesoctocog alfa maintained mean FVIII activity levels of >40 IU/dL for up to 4 days and at ∼10 IU/dL on day 7. Corresponding times for >40 IU/dL and >10 IU/dL were <1 and <2 days, respectively, for octocog alfa and 1 day and <3 days, respectively, for rurioctocog alfa pegol. No serious treatment-emergent adverse events were reported for efanesoctocog alfa, and no inhibitor development to FVIII was detected.

Conclusion

Efanesoctocog alfa had 3- to 4-fold longer elimination half-life and 3- to 6-fold greater exposure (area under the FVIII activity-time curve, 6.03 and 3.57 folds) than octocog alfa and rurioctocog alfa pegol. Efanesoctocog alfa provided high sustained FVIII activity in the normal-to-near-normal range (>40 IU/dL) for up to 4 days after the dose and at ∼10 IU/dL on day 7.

Modulation of factor VIII pharmacokinetics by genetic components in factor VIII receptors

INTRODUCTION

Gene variation in receptors for circulating factor VIII (FVIII) is candidate to explain the large inter-patient variability of infused FVIII pharmacokinetics (PK) in haemophilia A (HA).

AIM

To compare in an Italian HA cohort (n = 26) the influence on FVIII PK of genetic components in four von Willebrand factor (VWF)/FVIII receptors.

METHODS

Genotypes of low-density lipoprotein receptor (LDLR), asialoglycoprotein receptor minor subunit (ASGR2), family 4 member M (CLEC4M), stabilin2 (STAB2) and ABO blood-group, and VWF:Ag levels were included as independent variables in linear regression analyses of two-compartment model (TCM) - standard half-life (SHL) FVIII PK parameters.

RESULTS

In the initial FVIII distribution phase, the STAB2 rs4981022 AA, ASGR2 rs2289645 TT and LDLR rs688 TT genotypes may contribute to increase C_max , and prolong or shorten AlphaHL. In the elimination phase, a shorter BetaHL was associated with the CLEC4M rs868875 GG (beta-coefficient .366, p = .025) and ASGR2 rs2289645 TC (beta-coefficient .456, p = .006) genotypes, which also showed shorter mean residence time (MRT) than TT genotypes (p = .021). The alpha and beta phase effects were independent of ABO and VWF:Ag levels at baseline. The association of the LDLR rs2228671 genotypes with clearance was independent of ABO (beta-coefficient -.363, p = .035) but not of other receptors or VWF:Ag, which may point out multiple and competing interactions.

CONCLUSIONS

With the limitation of the small number of HA patients, these observations highlight multiple genetic components acting in distinct phases of FVIII PK and contributing to explain FVIII PK variability. This analysis provides candidates for genotype-based, individual tailoring of FVIII substitutive treatment.

Heterogeneity in the half-life of factor VIII concentrate in patients with hemophilia A is due to variability in the clearance of endogenous von Willebrand factor

BACKGROUND

Previous studies have reported marked interindividual variation in factor VIII (FVIII) clearance in patients with hemophilia (PWH) and proposed a number of factors that influence this heterogeneity.

OBJECTIVES

To investigate the importance of the clearance rates of endogenous von Willebrand factor (VWF) compared with those of other FVIII half-life modifiers in adult PWH.

METHODS

The half-life of recombinant FVIII was determined in a cohort of 61 adult PWH. A range of reported modifiers of FVIII clearance was assessed (including plasma VWF:antigen and VWF propeptide levels; VWF-FVIII binding capacity; ABO blood group; and nonneutralizing anti-FVIII antibodies). The FVIII-binding region of the VWF gene was sequenced. Finally, the effects of variation in FVIII half-life on clinical phenotype were investigated.

RESULTS

We demonstrated that heterogeneity in the clearance of endogenous plasma VWF is a key determinant of variable FVIII half-life in PWH. Both ABO blood group and age significantly impact FVIII clearance. The effect of ABO blood group on FVIII half-life in PWH is modulated entirely through its effect on the clearance rates of endogenous VWF. In contrast, the age-related effect on FVIII clearance is, at least in part, VWF independent. In contrast to previous studies, no major effects of variation in VWF-FVIII binding affinity on FVIII clearance were observed. Although high-titer immunoglobulin G antibodies (≥1:80) were observed in 26% of PWH, these did not impact FVIII half-life. Importantly, the annual FVIII usage (IU/kg/y) was significantly (p = .0035) increased in patients with an FVIII half-life of <12 hours.

CONCLUSION

Our data demonstrate that heterogeneity in the half-life of FVIII concentrates in patients with hemophilia A is primarily attributable to variability in the clearance of endogenous VWF.

Current Understanding of Inherited Modifiers of FVIII Pharmacokinetic Variation

The inherited bleeding disorder hemophilia A involves the quantitative deficiency of the coagulation cofactor factor VIII (FVIII). Prophylactic treatment of severe hemophilia A patients with FVIII concentrates aims to reduce the frequency of spontaneous joint bleeding and requires personalized tailoring of dosing regimens to account for the substantial inter-individual variability of FVIII pharmacokinetics. The strong reproducibility of FVIII pharmacokinetic (PK) metrics between repeat analyses in the same individual suggests this trait is genetically regulated. While the influence of plasma von Willebrand factor antigen (VWF:Ag) levels, ABO blood group, and patient age on FVIII PK is well established, estimates suggest these factors account for less than 35% of the overall variability in FVIII PK. More recent studies have identified genetic determinants that modify FVIII clearance or half-life including VWF gene variants that impair VWF-FVIII binding resulting in the accelerated clearance of VWF-free FVIII. Additionally, variants in receptors that regulate the clearance of FVIII or the VWF-FVIII complex have been associated with FVIII PK. The characterization of genetic modifiers of FVIII PK will provide mechanistic insight into a subject of clinical significance and support the development of personalized treatment plans for patients with hemophilia A.

Endothelial VWF is critical for the pathogenesis of vaso-occlusive episode in a mouse model of sickle cell disease

Vaso-occlusive episode (VOE) is a common and critical complication of sickle cell disease (SCD). Its pathogenesis is incompletely understood. von Willebrand factor (VWF), a multimeric plasma hemostatic protein synthesized and secreted by endothelial cells and platelets, is increased during a VOE. However, whether and how VWF contributes to the pathogenesis of VOE is not fully understood. In this study, we found increased VWF levels during tumor necrosis factor (TNF)-induced VOE in a humanized mouse model of SCD. Deletion of endothelial VWF decreased hemolysis, vascular occlusion, and organ damage caused by TNF-induced VOE in SCD mice. Moreover, administering ADAMTS13, the VWF-cleaving plasma protease, reduced plasma VWF levels, decreased inflammation and vaso-occlusion, and alleviated organ damage during VOE. These data suggest that promoting VWF cleavage via ADAMTS13 may be an effective treatment for reducing hemolysis, inflammation, and vaso-occlusion during VOE.

Correlation Analysis of DNA Methylation in the von Willebrand Factor Promoter Region and the Risk of Unexplained Recurrent Hemophilia: Systematic Review and Meta-Analysis

This study systematically reviewed the effect of DNA methylation in the promoter region of the coagulation factor vWF gene on the risk of unexplained recurrent hemophilia. PubMed, Medline, Web of Science, and other computers were used to search the database, and the statistical randomized controlled trials of coagulation factor vWF in the risk analysis of unknown recurrent hemophilia were collected. The Cochrane systematic evaluation method was used to evaluate the quality of the included kinds of literature, and Revman5 software was used to sort out and analyze the kinds of literature. Meta-analysis showed that there was a statistical difference between the experimental group and the control group in case fatality rate (OR = 1.76, 95% CI (1.29, 2.39), P=0.0003, I² = 0%, Z = 3.58), adverse events (OR = 2.38, 95% CI (1.65, 3.45), P < 0.00001, I² = 0%, Z = 4.60), incidence of joint hemorrhage (OR = 2.52, 95% CI (1.62, 3.91), P < 0.00001, I² = 0%, Z = 4.12), incidence of subcutaneous stasis (OR = 1.76, 95% CI (1.26, 2.45), P=0.0009, I² = 5%, Z = 3.33), and hematoma volume (OR = 1.78, 95% CI (1.32, 2.40), P=0.0001, I² = 23%, Z = 3.80). DNA methylation in the promoter region of the coagulation factor vWF gene was significantly associated with the risk of unexplained recurrent hemophilia. Whether demethylation can improve the bleeding index of patients with recurrent hemophilia remains to be further explored.

Screening of lncRNA-miRNA-mRNA Coexpression Regulatory Networks Involved in Acute Traumatic Coagulation Dysfunction Based on CTD, GeneCards, and PharmGKB Databases

Competitive endogenous RNA (ceRNA) networks play crucial roles in multiple biological processes and development of diseases. They might serve as diagnostic and prognosis markers as well as therapeutic targets. The purpose of this study was to identify a novel ceRNA network involving KCNQ1OT1, hsa-miR-24-3p, and VWF in acute traumatic coagulopathy (ATC) based on databases search. We searched the CTD, GeneCards, and PharmGKB databases for ATC-related target genes using Coagulopathy as a keyword. Upstream miRNAs and lncRNAs of the candidate target VWF were then explored using the miRWalk, microT, TargetScan, RNA22 and Tarbase, and DIANA-LncBase and Starbase databases, respectively. A KCNQ1OT1-hsa-miR-24-3p-VWF ceRNA network was constructed by R “ggalluvial” package. Interaction between KCNQ1OT1, hsa-miR-24-3p, and VWF was examined, and their expression was quantified in the peripheral blood samples from 30 ATC patients and liver tissues of ATC rat models. Forty-one ATC-related target genes were identified following data retrieval from publicly available databases, of which VWF was selected as the target and used for the subsequent analysis. KCNQ1OT1 and hsa-miR-24-3p were confirmed to be the key upstream regulatory factors of VWF. KCNQ1OT1-hsa-miR-24-3p-VWF coexpression regulatory network was constructed where KCNQ1OT1 competitively bound to hsa-miR-24-3p and attenuated its binding to VWF. Both the liver tissues of ATC rats and peripheral blood samples from ATC patients showed increased hsa-miR-24-3p expression and decreased VWF and KCNQ1OT1 expression. Collectively, we described the KCNQ1OT1-hsa-miR-24-3p-VWF ceRNA network in the development of ATC. We propose a new ceRNA that could help in the diagnosis and treatment of ATC.

Enhanced pharmacokinetics and reduced bleeds in boys with hemophilia A after switching to Kovaltry from other standard half-life factor VIII concentrates

Background

BAY81-8973 (Kovaltry; Bayer, Berkeley, CA, USA) was reported with enhanced pharmacokinetic (PK) profiles compared with some other standard half-life (SHL) factor VIII (FVIII) concentrates. Limited head-to-head comparative studies were conducted in a real-world setting.

Objective

To make head-to-head comparisons of PK and clinical outcomes between Kovaltry and three other SHL FVIII concentrates.

Methods

Forty-seven boys with severe hemophilia A were enrolled and divided into three groups according to their previously used FVIII concentrates (Kogenate FS, N = 22; Advate, N = 14; GreenMono, N = 11). Two separate PK tests were conducted in each participant with a five-point assay during the study period from 6 months before switching to 6 months after switching. FVIII levels were detected by one-stage assay, and PK profiles were calculated by noncompartmental assay. Annualized bleeding rates were collected through participant' bleed logs.

Results

Longer half-life time (Kogenate FS group: 14.4 vs 11.9 hours, P < .0001; Advate group: 13.4 vs 9.7 hours, P < .0001; GreenMono group: 15.1 vs 10.7 hours, P < .001]) and lower clearance (Kogenate FS group: 3.3 vs 3.9 mL/kg/h, P < .01; Advate group: 3.7 vs 5.9 mL/kg/h, P < .01; GreenMono group: 3.0 vs 5.1 mL/kg/h, P < .01) were observed with Kovaltry. In addition, longer mean residential time (P < .01) and higher area under the curve (P < .01) were demonstrated. No statistical difference was found in in vivo recovery between Kovaltry and the other FVIII products. Participants who switched to Kovaltry from three other FVIII concentrates with the same dosing regimens obtained higher trough FVIII levels and better protection with reduced annualized bleeding rates.

Conclusion

Compared with Kogenate FS, Advate, and GreenMono, Kovaltry showed enhanced PK profiles, which contributed to reduced bleeding rates.

Combination of CLEC4M rs868875 G-Carriership and ABO O Genotypes May Predict Faster Decay of FVIII Infused in Hemophilia A Patients

The C-type lectin CLEC4M binds and internalizes factor VIII (FVIII). Common CLEC4M variants have been associated with FVIII pharmacokinetic (PK) profiles in hemophilia A (HA) patients. The two-compartment PK analysis of plasma-derived (pd-) and full length recombinant FVIII concentrates was conducted in twenty-six patients (FVIII:C ≤ 2 IU/dL). F8, ABO blood-groups, and the CLEC4M rs868875A/G polymorphism were genotyped. CLEC4M genotype groups differed for the elimination rate constant K 1-0 (p < 0.001), half-life (K 1-0 HL), and the Beta rate constant. Patients treated with pd-FVIII also differed in the Alpha phase. In linear regression models, the contribution of the CLEC4M genotypes to FVIII PK parameters remained significant after correction for ABO, age, and VWF antigen levels at PK. Combined CLEC4M rs868875A/G and ABO genotypes displayed significant interaction (K 1-0, p = 0.014). Compared to other combined genotypes, the G-carriers/O genotypes showed half-reduced K 1-0 HL (p = 0.008), and faster FVIII clearance (mean 7.1 ± 2.2 mL/h/kg SE) than in the G-carriers/non-O (mean 2.4 ± 0.3 mL/h/kg SE), (p = 0.038). Comparison in HA patients recruited in several countries suggests that CLEC4M genotypes coherently influence infused FVIII half-life and clearance. Our analysis supports substantially faster FVIII decay associated with the rs868875 G-carrier/ABO O genotypes, which has potential implications for genetically tailored substitutive HA treatment.

Stabilin-2 deficiency increases thrombotic burden and alters the composition of venous thrombi in a mouse model

BACKGROUND

Stabilin-2 is an endocytic scavenger receptor that mediates the clearance of glycosaminoglycans, phosphatidylserine-expressing cells, and the von Willebrand factor-factor VIII (FVIII) complex. In a genome-wide screening study, pathogenic loss-of-function variants in the human STAB2 gene associated with an increased incidence of unprovoked venous thromboembolism (VTE). However, the specific mechanism(s) by which stabilin-2 deficiency influences the pathogenesis of VTE is unknown.

OBJECTIVES

The aim of this study was to assess the influence of stabilin-2 on deep vein thrombosis (DVT) and to characterize the underlying prothrombotic phenotype of stabilin-2 deficiency in a mouse model.

METHODS

DVT was induced using the inferior vena cava (IVC) stenosis model in two independent cohorts (littermates and non-littermates) of wild-type (Stab2+/+ ) and stabilin-2 (Stab2-/- )-deficient mice. Thrombus structure and contents were quantified by immunohistochemistry. Plasma procoagulant activity was assessed and complete blood counts were performed.

RESULTS

Incidence of thrombus formation was not altered between Stab2+/+ and Stab2-/- mice. When thrombi were formed, Stab2-/- mice developed significantly larger thrombi than Stab2+/+ controls. Thrombi from Stab2-/- mice contained significantly more leukocytes and citrullinated histone H3 than Stab2+/+ thrombi. Stab2-/- mice had increased FVIII activity. Circulating levels of monocytes and granulocytes were significantly elevated in Stab2-/- mice, and Stab2-/- mice had elevated plasma cell-free DNA 24 hours post-IVC stenosis compared to their Stab2+/+ counterparts.

CONCLUSIONS

These data suggest that stabilin-2 deficiency associates with a prothrombotic phenotype involving elevated levels of neutrophil extracellular trap-releasing leukocytes coupled with endogenous procoagulant activity, resulting in larger and qualitatively distinct venous thrombi.

MicroRNA-320a-3p Signatures as a Satisfactory Predictor of Acute Coronary Syndrome and Attenuates Inflammation by Targeting X-Linked Inhibitor of Apoptosis Protein

Acute coronary syndrome (ACS) is a heart disease with a high mortality rate. Recently, more and more evidence illustrated that microRNAs (miRNA) participated in regulating the occurrence of heart disease. This study aimed to detect the level of serum miR-320a-3p in patients with ACS, predict its possibility as a candidate gene for diagnosis, and explore its potential mechanism in the regulation of ACS. 139 ACS patients and 126 controls were recruited in this study. The expression level of miR-320a-3p was determined by qRT-PCR. The predictive value in ACS was assessed by receiver operating characteristic (ROC) curve. Enzyme-linked immunosorbent assay (ELISA) was used to measure the protein expression levels of inflammatory factors. The downstream targets of miR-320a-3p were verified by luciferase reporter gene assay. In ACS patients and rat models, the expression level of serum miR-320a-3p was significantly increased. ROC curve revealed that abnormal expression of miR-320a-3p was of diagnostic value for ACS. In an in vivo rat model, down-regulation of miR-320a-3p inhibited the production of von Willebrand factor (vWF), Heart fatty acid-binding protein (H-FABP), interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α). In other words, down-regulation of miR-320a-3p reduced rat vascular endothelial injury and inflammation. X-linked inhibitor of apoptosis protein (XIAP) was determined to be a direct target of miR-320a-3p. miR-320a-3p is useful for the diagnosis of ACS. Animal experiments confirmed that up-regulated miR-320a-3p promoted vascular endothelial injury and inflammatory response by targeting XIAP, thus promoting the development of ACS. MiR-320a-3p may be a new breakthrough in the diagnosis and treatment of ACS.

Pharmacokinetics of perioperative FVIII in adult patients with haemophilia A: An external validation and development of an alternative population pharmacokinetic model

INTRODUCTION

Haemophilia A patients require perioperative clotting factor replacement to limit excessive bleeding. Weight-based dosing of Factor VIII (FVIII) does not account for inter-individual pharmacokinetic (PK) variability, and may lead to suboptimal FVIII exposure.

AIM

To perform an external validation of a previously developed population PK (popPK) model of perioperative FVIII in haemophilia A patients.

METHODS

A retrospective chart review identified perioperative haemophilia A patients at the University of North Carolina (UNC) between April 2014 and November 2019. Patient data was used to externally validate a previously published popPK model proposed by Hazendonk. Based on these validation results, a modified popPK model was developed to characterize FVIII PK in our patients. Dosing simulations were performed using this model to compare FVIII target attainment between intermittent bolus (IB) and continuous infusion (CI) administration methods.

RESULTS

A total of 521 FVIII concentrations, drawn from 34 patients, were analysed. Validation analyses revealed that the Hazendonk model did not fully capture FVIII PK in the UNC cohort. Therefore, a modified one-compartment model, with weight and age as covariates on clearance (CL), was developed. Dosing simulations revealed that CI resulted in improved target attainment by 16%, with reduced overall FVIII usage by 58 IU/kg, compared to IB.

CONCLUSION

External validation revealed a previously published popPK model of FVIII did not adequately characterize UNC patients, likely due to differences in patient populations. Future prospective studies are needed to evaluate our model prior to implementation into clinical practice.

The Asialoglycoprotein Receptor Minor Subunit Gene Contributes to Pharmacokinetics of Factor VIII Concentrates in Hemophilia A

BACKGROUND

 The asialoglycoprotein receptor (ASGPR) binds with high affinity factor VIII (FVIII) through its N-linked oligosaccharides. However, its contribution to the wide inter-individual variation of infused FVIII pharmacokinetics (PK) in hemophilia A (HA) is unknown.

OBJECTIVE

 To investigate the variability in FVIII PK outcomes in relation to genetic variation in the ASGR2, encoding the ASGPR2 subunit.

METHODS

 Thirty-two HA patients with FVIII:C ≤2 IU/dL underwent 66 single-dose FVIII PK studies. PK parameters were evaluated in relation to ASGR2 5' untranslated region (5'UTR) polymorphisms, which were investigated by recombinant and white blood cell reverse transcription-polymerase chain reaction approaches.

RESULTS

 The 5'UTR polymorphisms determine a frequent and conserved haplotype (HT1) in a regulatory region. The HT1 homozygotes may differ in the amounts of alternatively spliced mRNA transcripts and thus ASGPR2 isoforms. Compared with the other ASGR2 genotypes, the c.-95TT homozygotes (n = 9), showed threefold longer Alpha HL (3.60 hours, 95% confidence interval: 1.44-5.76, p = 0.006), and the c.-95TC heterozygotes (n = 17) showed 25% shorter mean residence time (MRT; 18.5 hours, 15.0-22.0, p = 0.038) and 32% shorter Beta HL (13.5 hours, 10.9-16.0, p = 0.016). These differences were confirmed in patients (n = 27) undergoing PK studies (n = 54) with full-length FVIII only. In different linear regression models, the contribution of the ASGR2 genotypes remained significant after adjustment by ABO genotypes and von Willebrand factor (VWF) antigen levels, and explained 14% (MRT), 15 to 18% (Beta HL), and 22% (Alpha HL) of parameter variability.

CONCLUSIONS

 Infused FVIII distribution was modulated by frequent ASGR2 genotypes, independently from and together with ABO and VWF antigen levels, which has potential implications for genetically tailored substitutive treatment in HA.

FVIII at the crossroad of coagulation, bone and immune biology: Emerging evidence of biological activities beyond hemostasis

Hemophilia A is an X-linked hereditary disorder that results from deficient coagulation factor VIII (FVIII) activity, leading to spontaneous bleeding episodes, particularly in joints and muscles. FVIII deficiency has been associated with altered bone remodeling, dysregulated macrophage polarization, and inflammatory processes that are associated with the neoformation of abnormal blood vessels. Treatment based on FVIII replacement can lead to the development of inhibitors that render FVIII concentrate infusion ineffective. In this context, hemophilia has entered a new therapeutic era with the development of new drugs, such as emicizumab, that seek to restore the hemostatic balance by bypassing pathologically acquired antibodies. We discuss the potential extrahemostatic functions of FVIII that may be crucial for defining future therapies in hemophilia.

Efficacy, Safety and Pharmacokinetic Results of a Phase III, Open-Label, Multicenter Study with a Plasma-Derived Von Willebrand Factor (VWF)/Factor VIII (FVIII) Concentrate in Pediatric Patients <12 Years of Age with Hemophilia A (SWIFTLY-HA Study)

Background

Plasma-derived von Willebrand factor/factor VIII (pdVWF/FVIII; VONCENTO^®, CSL Behring) is a high-concentration, low-volume, high-purity concentrate, with a high level of VWF high-molecular-weight multimers and a VWF/FVIII ratio of ~2.4:1.

Methods

This study (NCT01229007) investigated the pharmacokinetics (PK), efficacy and safety of pdVWF/FVIII in 35 previously treated (minimum 20 exposure days [EDs]) pediatric patients (<12 years) with severe hemophilia A. PK was evaluated with a single 50 IU FVIII/kg dose of pdVWF/FVIII. Efficacy and safety analyses were performed during on-demand treatment (n=17) or prophylaxis (n=18) for up to 100 EDs with a maximum study duration of 12 months.

Results

PK profiles were similar for patients aged <6 years and those aged 6–12 years, and, as expected, the youngest patients had an increased clearance. On-demand patients reported 320 non-surgical bleeding (NSB) events and received a median number of 29.0 infusions (median dose 34.2 IU FVIII/kg). Hemostatic efficacy was assessed by the investigator as excellent/good in all cases (24%/76%). The 18 patients in the prophylaxis arm experienced 173 NSB events (97 NSBs [56%] in three patients). Five patients (28%) had no NSB events. Overall, patients received a median number of 92 infusions (median dose 30.6 IU FVIII/kg). The majority of bleeds (92%) were successfully controlled with only one infusion. Hemostatic efficacy was assessed by the investigator as excellent (86%) or good (14%). Inhibitors occurred in three patients of which two were transient (low titer) and one persisted (high titer). These three patients had known risk factors for inhibitor development.

Conclusion

This study demonstrated comparable PK profiles for pediatric patients aged <6 years and aged 6–12 years, and an excellent efficacy and safety profile in this population. The adverse events reported were mostly mild to moderate with inhibitor rates within the expected incidence range.

Pharmacokinetic-guided prophylaxis improved clinical outcomes in paediatric patients with severe haemophilia A

BACKGROUND

The traditional weight-based dosing regimen can lead to under- or overdosage due to the interindividual variability of pharmacokinetic (PK) parameters. PK-guided prophylaxis can be an optimized therapy choice.

AIM

This study aimed to investigate the clinical outcomes of PK-guided prophylaxis in 46 boys with severe haemophilia A.

METHODS

Forty-six boys with severe haemophilia A were enrolled in Beijing Children's Hospital. The PK tests were performed using a five-point assay. PK parameters were calculated using WinNonlin software. The dosing regimen and bleeding rates recorded during the observation period. The adjustment was based on PK evaluation, bleeding details, doctor's advice and patients' choice.

RESULTS

The half-life time, in vivo recovery and clearance of Kovaltry were 14.34 ± 2.68 h, 1.78 ± 0.29 kg/dl and 3.38 ± 0.94 ml/kg/h, respectively. In 18 patients without any change in the dosing regimen, the trough level was 4.0 ± 2.41 IU/dl and the bleeding rates were similar after PK tests. For patients with a higher trough level after adjustment, higher dose and frequency were observed, as well as a higher trough level. Also, reduced annual bleeding rate (ABR), annual joint bleeding rate and annual spontaneous bleeding rate (ASBR) were found. In five patients with a reduced trough level, lower infusion frequency and weekly coagulation factor VIII (FVIII) consumption were observed, with no statistically significant difference in ABR and ASBR.

CONCLUSION

PK-guided prophylaxis can help haemophiliac patients improve quality of life by decreasing bleeds with appropriate FVIII consumption and reducing infusion frequency without increments in bleeds, thus optimizing haemophilia treatment.

Perspective - The case for zero bleeds and drug bioequivalence in the treatment of congenital hemophilia A in 2021

Not all patients with severe hemophilia A (HA) respond optimally to a given dose of a given product. Within-individual variance in cross-over studies makes each patient unique in the response to each standard half-life (SHL) factor VIII (FVIII) product in pharmacokinetic (PK) terms. This hampers the prediction of efficacy when a SHL FVIII product is employed. PK data showing that half-lives of SHL rFVIII are unsatisfactory to achieve zero bleeding in individual HA patients provide the rationale for switching from SHL to extended half-life (EHL) products. However, not all subjects receiving prophylaxis with EHL products achieve zero bleeding, the most cogent objective of personalized prophylaxis. Known determinants of FVIII half-life (age, von Willebrand factor [VWF] levels, blood group) cumulatively account for one third of the total inter-individual variation in FVIII clearance in subjects with severe HA. Investigations into precision, and accuracy of laboratory measurement to be employed; newer pathways for the clearance of both free-FVIII and VWF-bound FVIII, and adequately powered studies on omics and phenotypic heterogeneity, are likely to provide additional information on the remaining two thirds of inter-individual variation in FVIII clearance in HA. Variability in the clinical response has also been documented in patients when FVIII activity is mimicked by fixed subcutaneous doses of the bispecific antibody emicizumab. National registries that collect PK data of available FVIII products and ad hoc information on the individual response to emicizumab should be encouraged, to establish newer standards of care and ease personalized clinical decisions to achieve zero bleeding.

Pharmacokinetic study of Kovaltry in thirty-five pediatric patients aged <12 years with severe hemophilia A

BACKGROUND

Kovaltry (BAY81-8973) is an unmodified full-length factor VIII (FVIII) concentrate that enhances the pharmacokinetic (PK) profiles as compared to some other standard half-life time FVIII concentrates. However, the PK of Kovaltry in haemophiliac patients aged <12 years has not been reported previously.

AIM

To investigate the pharmacokinetics and clinical outcomes of Kovaltry in 35 paediatric patients aged <12 years.

METHODS

A total of 35 boys with severe haemophilia A were enrolled from August 2019 to May 2020 in Beijing Children's Hospital. After 72-hour washout, PK tests were performed post-infusion of 50 IU/kg Kovaltry in a five-timepoint assay. WinNonlin software was used to generate individual PK parameters. The dose, frequency and bleeding details were collected within the first 6 months after switching to Kovaltry from other FVIII concentrates.

RESULTS

Compared to the blood group O, patients with blood group non-O showed longer mean half-life (t_1/2 ) (p < .01), lower mean clearance (CL) (p = .01) and similar in vivo recovery (IVR) (p = .51). Higher von Willebrand factor antigen (VWF:Ag) level was correlated to longer t_1/2 (p < .0001) and lower CL (p < .01). IVR was correlated to body mass index (BMI) (p < .0001). Patients with trough level >3 IU/dL demonstrated lower annual bleeding rate (ABR) (p < .01), annual joint bleeding rate (AJBR) (p < .01) and annual spontaneous bleeding rate (ASBR) (p < .01).

CONCLUSION

This study firstly reported the PK profiles of Kovaltry in 35 paediatric patients <12 years old. The great inter-individual variability of PK parameters was also confirmed in these patients. VWF:Ag and blood group were major influencing factors of t_1/2 and CL of Kovaltry, while BMI was a vital predictor for IVR. Patients with high trough FVIII level in routine prophylaxis had reduced bleeding rates.

Factor VIII pharmacokinetics associates with genetic modifiers of VWF and FVIII clearance in an adult hemophilia A population

BACKGROUND

Factor VIII (FVIII) pharmacokinetics (PK) in adult hemophilia A populations are highly variable and have been previously determined to be influenced by von Willebrand factor:antigen (VWF:Ag), ABO blood group, and age. However, additional genetic determinants of FVIII PK are largely unknown.

OBJECTIVES

The contribution of VWF clearance, VWF-FVIII-binding activity, and genetic variants in VWF clearance receptors to FVIII PK in adult patients were assessed.

METHODS

FVIII PK assessment was performed in 44 adult subjects (age 18-61 years) with moderate or severe hemophilia A. VWF:Ag, VWF propeptide (VWFpp), VWFpp/VWF:Ag, and VWF:FVIII binding activity were measured. The VWF modifying loci CLEC4M, SCARA5, STAB2, and ABO, and the D'D3 FVIII-binding region of the VWF gene were genotyped.

RESULTS

VWF:Ag, VWFpp, and VWF:FVIIIB positively correlated with FVIII half-life and negatively correlated with FVIII clearance. VWFpp/VWF:Ag negatively correlated with FVIII half-life and positively correlated with FVIII clearance. The correlation between VWFpp/VWF:Ag and FVIII half-life was stronger for type non-O patients than for type O patients, suggesting that slower VWF clearance increases FVIII half-life. Patients heterozygous for the CLEC4M rs868875 variant had increased FVIII clearance when compared with individuals homozygous for the reference allele. The CLEC4M variable number of tandem repeat (VNTR) alleles were also associated with the rate of FVIII clearance. When compared with the quartile of patients with the fastest FVIII clearance, the quartile of patients with the slowest FVIII clearance had a decreased frequency of the CLEC4M 5-VNTR.

CONCLUSIONS

VWF-FVIII binding activity and genetic determinants of VWF clearance are important contributors to FVIII pharmacokinetics in adult patients.

Glyco-engineered HEK 293-F cell lines for the production of therapeutic glycoproteins with human N-glycosylation and improved pharmacokinetics

N-glycosylated proteins produced in human embryonic kidney 293 (HEK 293) cells often carry terminal N-acetylgalactosamine (GalNAc) and only low levels of sialylation. On therapeutic proteins, such N-glycans often trigger rapid clearance from the patient bloodstream via efficient binding to asialoglycoprotein receptor (ASGP-R) and mannose receptor (MR). This currently limits the use of HEK 293 cells for therapeutic protein production. To eliminate terminal GalNAc, we knocked-out GalNAc transferases B4GALNT3 and B4GALNT4 by CRISPR/Cas9 in FreeStyle 293-F cells. The resulting cell line produced a coagulation factor VII-albumin fusion protein without GalNAc but with increased sialylation. This glyco-engineered protein bound less efficiently to both the ASGP-R and MR in vitro and it showed improved recovery, terminal half-life and area under the curve in pharmacokinetic rat experiments. By overexpressing sialyltransferases ST6GAL1 and ST3GAL6 in B4GALNT3 and B4GALNT4 knock-out cells, we further increased factor VII-albumin sialylation; for ST6GAL1 even to the level of human plasma-derived factor VII. Simultaneous knock-out of B4GALNT3 and B4GALNT4, and overexpression of ST6GAL1 further lowered factor VII-albumin binding to ASGP-R and MR. This novel glyco-engineered cell line is well-suited for the production of factor VII-albumin and presumably other therapeutic proteins with fully human N-glycosylation and superior pharmacokinetic properties.

Common Genetic Variants in ABO and CLEC4M Modulate the Pharmacokinetics of Recombinant FVIII in Severe Hemophilia A Patients

The pharmacokinetic (PK) response of severe hemophilia A (HA) patients to infused factor VIII (FVIII) shows substantial variability. Several environmental and genetic factors are associated with changes in FVIII plasma levels and infused FVIII PK. Based on the hypothesis that factors influencing endogenous FVIII can affect FVIII PK, the contribution of single-nucleotide variants (SNVs) in candidate genes was investigated in 51 severe HA patients. The effects of blood group, F8 variant type, von Willebrand factor antigen and activity levels, age, and weight were also explored. The myPKFiT device was used to estimate individual PK parameters, and SNVs and clinically reportable F8 variants were simultaneously analyzed in an Illumina MiSeq instrument, using the microfluidics-based Fluidigm Access Array system. The contribution of SNVs to FVIII half-life and clearance was addressed by robust regression modeling, taking into account other modulators. In line with previous studies, we provide robust evidence that age, body weight, and blood group, as well as SNVs in ABO and CLEC4M, participate in the variability of FVIII PK in HA patients. Main results: each copy of the rs7853989 (ABO) allele increases FVIII half-life by 1.4 hours (p = 0.0131) and decreases clearance by 0.5 mL/h/kg (p = 5.57E-03), whereas each additional rs868875 (CLEC4M) allele reduces FVIII half-life by 1.1 hours (p = 2.90E-05) and increases clearance by 0.3 mL/h/kg (p = 1.01E-03). These results contribute to advancing efforts to improve FVIII replacement therapies by adjusting to each patient's PK profile based on pharmacogenomic data. This personalized medicine will decrease the burden of treatment and maximize the benefits obtained.

Biological mechanisms underlying inter-individual variation in factor VIII clearance in haemophilia

Previous studies have highlighted marked inter‐individual variations in factor VIII (FVIII) clearance between patients with haemophilia (PWH). The half‐life of infused FVIII has been reported to vary from as little as 5.3 hours in some adult PWH, up to as long as 28.8 hours in other individuals. These differences in clearance kinetics have been consistently observed using a number of different plasma‐derived and recombinant FVIII products. Furthermore, recent studies have demonstrated that half‐life for extended half‐life (EHL‐) FVIII products also demonstrates significant inter‐patient variation. Since time spent with FVIII trough levels <1% has been shown to be associated with increased bleeding risk in PWH on prophylaxis therapy, this variability in FVIII clearance clearly has major clinical significance. Recent studies have provided significant novel insights into the cellular basis underlying FVIII clearance pathways. In addition, accumulating data have shown that endogenous plasma VWF levels, ABO blood group and age, all play important roles in regulating FVIII half‐life in PWH. Indeed, multiple regression analysis suggests that together these factors account for approximately 34% of the total inter‐individual variation in FVIII clearance observed between subjects with severe haemophilia A. In this review, we consider these and other putative modulators of FVIII half‐life, and discuss the biological mechanisms through which these factors impact upon FVIII clearance in vivo.

Delivering on the promise of gene therapy for haemophilia

The promise of gene therapy is a single treatment ('one and done') that leads to steady-state expression of endogenous factor VIII or factor IX sufficient to achieve a functional cure (free of recurrent haemophilic bleeding) if not normalized haemostasis. The elimination of the need for continued prophylaxis, or factor replacement following trauma or prior to surgery would lead to annual cost savings. Such optimized health and well-being would be reaching a level of health equity that was unimaginable several decades ago. 'Before anything else, preparation is the key to success'-Alexander Graham Bell. This quote from the famous inventor, scientist and engineer highlights that, although we currently stand on the threshold of this achievement, delivering on this promise will require broad-based multistakeholder preparation (scientists, manufacturers, federal regulators, health technology assessors, persons with haemophilia, national advocacy groups and multidisciplinary healthcare teams) with a focused emphasis on education, approval of safe and effective therapies, removal of barriers to access and excellence in clinical delivery.

Hemophilia A and von Willebrand deficiency: therapeutic implications

: Hemophilia A is an X-linked bleeding disorder caused by a deficiency of factor VIII. Depending on the factor VIII activity in patient's plasma, we can have three different forms of hemophilia A: mild (5-40 IU/dl), moderate (1-5 IU/dl) and severe (<1 IU/dl). The most common symptoms include recurrent bleeding episodes of soft tissues and joints. The treatment is based on the prophylactic use of clotting factor concentrates to prevent bleeding episodes. We describe three cases of patients with initially diagnosis of hemophilia A that show different clinical severity, undergoing prophylactic therapies with low benefit. In these patients, the dosage of von Willebrand antigen revealed either low level or absence of this factor, which in one case was caused by the occurrence of a type III form of von Willebrand disease.

Clinical Evidence and Safety Profile of Emicizumab for the Management of Children with Hemophilia A

Emicizumab is a bispecific, humanized, monoclonal antibody mimicking the factor (F) VIII cofactor activity in mediating the generation of FXa by FIXa in patients with hemophilia A (HA). This subcutaneous non-factor agent has been recently extensively approved for the prophylaxis of patients of HA patients with and without FVIII-inhibitors of all ages, although few data are currently available in children. In Phase 3 clinical trials and case series, emicizumab prophylaxis significantly reduced bleeding rates compared to previous treatment in HA adolescents and children with or without FVIII-inhibitors and was generally well tolerated. In addition, subcutaneous administration of emicizumab provided beneficial effects on health-related quality of life, and lessened the burden of the disease in HA patients as well as in their caregivers. However, additional prospective studies are required to evaluate the long-term safety of emicizumab prophylaxis in very young patients, including previously untreated patients. The aim of this paper was to review the limited data available on the use of emicizumab prophylaxis in children and to highlight the need for further studies to address remaining concerns.