FVIII Levels Research Articles

Accurate evaluation of factor VIII activity of efanesoctocog alfa in the presence of emicizumab.

Efanesoctocog is a B-domain-deleted, Fc-fusion FVIII linked to the D'D3 domain of VWF and two XTEN polypeptides, designed for an ultra-extended half-life for prophylaxis in hemophilia A, but also aiding in managing acute bleeding or surgery in patients on long-term emicizumab. However, no current laboratory method accurately measures FVIII levels in the presence of emicizumab. We hypothesized that the chromogenic (CSA) FVIII assay, specifically calibrated for efanesoctocog using bovine coagulation factors, could provide an accurate assessment of efanesoctocog activity. Seven centers across five countries received 12 plasma samples to measure in triplicate using two calibration methods across three independent days. Samples (n=6) contained either only efanesoctocog (FVIII :C=150 to 5 IU/dL), or efanesoctocog (FVIII:C=150 to 5 IU/dL) in combination with emicizumab (50 μg/mL)(n=5). One sample contained efanesoctocog (FVIII :C=50 IU/dL) and a high dose of emicizumab (80 μg/mL), another sample contained efanesoctocog (FVIII :C=50 IU/dL) with a low dose of emicizumab (20 μg/mL). Each center used its own analyzers, along with their usual reagents. CSA calibrated with standard calibrators highly overestimate FVIII activity. However, specific calibration with efanesoctocog enabled accurate measurement of FVIII activity, with low inter- and intra-laboratory variability, and no interference from emicizumab. All CSA reagents used in the study demonstrated low variability across different laboratories (Inter-laboratory coefficient of variation ranges between 9% and 20%). Specific calibration of the CSA FVIII assay using efanesoctocog and bovine reagents allows for accurate measurement of FVIII activity in patients receiving efanesoctocog, even in the presence of emicizumab.

Flow Cytometry Evaluation of Blood-Cell-Bound Surface FVIII in Hemophilia A and Thrombosis.

Hemophilia A (HA) is associated with FVIII coagulation insufficiency or inactivity leading to excessive bleeding. Elevated FVIII, on the contrary, is associated with thrombophilia, thrombosis, myocardial infarctions, and stroke. Active FVIII (aFVIII) uses its C2 domain to bind to blood cells' membranes, consequently carrying out its coagulative function. We developed a reliable flow cytometry (FC) method for FVIII detection that can be utilized for assessing surface-bound FVIII on leukocytes in different coagulation/clinical states; we analyzed 49 pediatric subjects, encompassing patients with HA, other coagulopathies, venous thrombosis, and normal coagulation. Interestingly, the total leukocyte surface FVIII showed a declining trend across thrombosis, normal, and hypo-coagulation states. As expected, the leukocytes of HA patients displayed significantly lower levels of cellular-surface FVIII in comparison to patients with thrombosis. However, no significant correlation was observed between circulating levels of FVIII in plasma and the levels of FVIII bound to leukocytes, indicating that the differences in FVIII surface binding are not directly proportional to the availability of FVIII in the circulation and suggesting a specific binding mechanism governing the interaction between FVIII and leukocytes. Intriguingly, when analyzing the distinct blood subpopulations, we observed that surface FVIII levels were significantly elevated in classical monocytes of thrombosis patients compared to HA patients, healthy controls, and patients with other coagulopathies. Our study highlights the reliability of our FC platform in assessing FVIII abundance on leukocytes' membranes across coagulation states. Monocytes, particularly in cases of thrombosis, exhibit active binding of FVIII on their surface, suggesting a potential role in the pathophysiology of thrombosis that requires further investigation.

The Influence of Vitamin K Levels on Blood Coagulation Factors After Tooth Extraction in Hemophilia Patients

Hemophilia is a genetic disorder resulting from impaired blood clotting. This disorder can be caused by coagulation factor abnormalities due to a deficiency of clotting factors, including vitamin K. A lack of vitamin K disrupts the coagulation process, increasing the tendency for bleeding. This article aims to determine whether there is an influence of vitamin K levels on the blood clotting factors in hemophilia patients. Searching any information needed by analyzing kinds of papers of recent research from the year of 2014 until 2024. Online databases like PubMed, ScienceDirect, Google Scholar, Scopus, and ResearchGate are utilized by inserting relevant keywords, such as hemophilia, blood clotting factors, vitamin K deficiency and extraction. From 10 articles reviewed, a relationship was identified between vitamin K levels and blood clotting factors in hemophilia patients. Individuals with severe hemophilia experience bleeding episodes characterized by delayed onset, as well as bleeding into muscles, joints, and other internal structures, including the brain. Hemophilia is typically diagnosed through the identification of low or absent levels of FVIII:C or FIX:C. The genes encoding FVIII and FIX are located on the long arm of the X chromosome. Hemophilia A and B are the only hereditary clotting disorders inherited in a sex-linked recessive pattern. Vitamin K levels can influence the blood clotting factors in hemophilia patients, particularly those factors synthesized artificially.

Pilot evaluation of LR EXT sets of the Reveos automated blood processing system.

The Reveos automated blood processing system is the only system developed till date, which can separate whole blood into components on complete automation. Their proprietary LR and NLR blood collection sets have their own advantages and disadvantages. Using LR sets, leukodepleted components can be prepared but individual platelet units cannot be prepared. Using NLR sets, individual platelet units can be prepared, but components are non-leukodepleted. The newly launched LR EXT with the apparent advantage of both LR and NLR sets have been evaluated in this pilot study. Blood components prepared from 31 LR EXT sets were evaluated in this study in comparison with the National regulations and with components routinely prepared from LR and NLR sets. Excluding under-collected and sero-reactive units, components prepared from 27 LR EXT sets were evaluated for their quality. QC of PRBC units prepared had a mean volume of 296.86 ml, Hct of 59.2 % and WBC count as low as 0.06 × 106 per bag. FFP units had a mean volume of 221.89 ml, mean Fibrinogen of 432.47 mg and FVIII levels of 98.13 IU per bag. PLT units had a mean volume of 73.07 ml, PLT count of 5.74 × 1010 and WBC count of 3.21 × 108 per bag. The use LR EXT blood collection sets help in achieving adequate inventory of both LD-PRBCs and RDPs especially in blood centres with a lower daily collection rate.

A fully humanized von Willebrand disease type 1 mouse model as unique platform to investigate novel therapeutic options.

Patients suffering from von Willebrand disease (VWD) have reduced quality-of-life despite current treatment options. Moreover, innovation in VWD therapeutic strategies has essentially stalled and available treatments have remained unchanged for decades. Therefore, there is an unmet need to develop new therapeutic strategies for VWD-patients, especially for the large portion of those with VWD-type 1. Due to species differences, the available VWD murine models are not suitable for preclinical studies, making it difficult to test new therapeutic approaches in vivo. With this in mind, we generated mice selectively expressing human von Willebrand factor (VWF) and human GPIbα. Because this fully humanized model was found to express low VWF (12%) and FVIII (40%) levels with normal multimer profile and activity/antigen ratio, we repositioned it as a VWD-type 1 model (hVWD1 mice). In depth characterization of this model confirmed VWD-type 1 features with a decrease in platelet adhesion and thrombus formation in vitro. In vivo, a moderate bleeding phenotype was observed which was corrected upon the administration of recombinant-VWF or upon histamine-induced release of endothelial VWF. In search for new therapeutic options for VWD, we designed a bispecific single-domain antibody that bridges VWF to albumin (KB-V13A12). Remarkably, a single subcutaneous administration of KB-V13A12 coincided with a sustained 2-fold increase in VWF antigen levels for up to 10 days and normalized haemostasis in a tail-clip model in hVWD1 mice. We have developed a unique humanized mouse model for VWD-type 1 and a promising new therapeutic that corrected haemostasis in these mice.

Bleeding Symptoms in Pediatric Patients with Congenital FVII Deficiency and Correlation to Thrombin Generation Assay Parameters: A Single-Center Retrospective Analysis.

Inherited factor VII deficiency is the most common rare bleeding disorder, affecting about 1/500,000 individuals without gender predilection. Most of the patients with FVII 20-50% are asymptomatic, but post-traumatic or post-surgical bleeding may often occur since there is not an exact correlation between FVII plasma levels and the bleeding phenotype. We enrolled 19 children and adolescents with FVII levels of 20-35% and 33 controls. Laboratory data collected included thrombin generation, prothrombin time, activated partial thromboplastin time, fibrinogen, and FVII levels. In our study, we found a statistical difference in the lag time ratio (p < 0.01) and tt-peak ratio (p < 0.05) between patients and controls but no difference in the other parameters, such as the endogenous thrombin potential (ETP). However, when we categorized patients, regardless of their bleeding scores, as presenting symptoms and having no symptoms, both the lag time ratio (p = 0.01) and tt-peak ratio (p < 0.05) were significantly different, and the vel. index % showed increased levels in patients without symptoms (p < 0.05). This study shows that thrombin generation may be a useful tool in assessing the risk of bleeding symptoms in children with an FVII deficiency categorized in the mild category (20-35%), although we cannot predict the severity of the bleeding.

Saliva of persons with hemophilia A triggers coagulation via extrinsic tenase complexes

AbstractHuman saliva contains extracellular vesicles (EVs). These EVs expose extrinsic tenase complexes of tissue factor (TF) and activated factor VII (FVIIa), and trigger blood coagulation. Here, we show that EVs exposing extrinsic tenase complexes are also present in saliva of persons with severe hemophilia A, that is, persons with FVIII deficiency. Addition of these salivary EVs to autologous FVIII-deficient blood results in FXa generation, thereby compensating for the lack of FXa generation via intrinsic tenase (FVIIIa/FIXa) complexes. Consistently, in our retrospective analysis of persons with severe hemophilia A who do not receive prophylactic FVIII substitution, oropharyngeal mucosal bleedings are infrequent and self-limited. Conversely, in saliva of persons with severe FVII deficiency, in whom oropharyngeal bleedings are prevalent, functional extrinsic tenase complexes are absent, because EVs lack FVII. Saliva of persons with severe FVII deficiency is unable to restore blood coagulation, which is because of the absence of FVII in both their saliva and blood. Picomolar levels of recombinant FVIIa can restore the coagulant potential of saliva of persons with FVII deficiency. Taken together, our findings may explain the paucity of oropharyngeal bleedings in persons with hemophilia A as well as the occurrence of such bleedings in persons with severe FVII deficiency.

Moderate haemophilia A: Recommendations from a Spanish panel of experts.

Diagnosing moderate haemophilia A (MHA) solely based on deficient FVIII protein levels limits its optimal management and delays the initiation of prophylaxis. Updating protocols and incorporating new variables into its diagnosis could prevent underestimating disease severity, avoiding early arthropathies and impairing patients' quality of life. To propose recommendations to improve the comprehensive management of people with MHA. Recommendations from a Spanish panel of eight experts from public comprehensive care centres (CCCs) for people with haemophilia and over 140 people with MHA in follow-up. In a previous analysis, the panel identified the unmet needs of people with MHA and the necessity to develop new specific recommendations for their management. The panel proposed recommendations in four areas: diagnosis, treatment, follow-up and referrals. They detailed the necessary steps and procedures for the diagnosis, adding other variables to the FVIII levels like bleeding phenotype, genetic profile and joint status to specify the severity and risk classification of people with MHA. Experts proposed an algorithm with unique independent criteria to facilitate the decision to initiate prophylaxis, where the recommended FVIII levels and variables coexist for treatment decision-making. Follow-up proposals addressed periodicity, recommended tests and required visits to CCCs. For referrals, experts proposed criteria and situations considered urgent for a transfer to a CCC for haemophilia patients. The proposals agreed upon by this expert panel can contribute to update and optimize the management of people with MHA, delaying joint deterioration, pain and disabilities, and improving their quality of life.

Activity Assessment of Factor Replacement Therapies to Guide Infusion Rate Protocols in Patients with Bleeding Disorders

Abstract Introduction The development of institutional protocols guiding administration of clotting factor replacements in patients with bleeding disorders requires an understanding of product stability over infusion duration. Inclusion of new factor products on formulary at our institution raised consideration for optimal administration routes, including whether a bolus intravenous push versus infusion over 4-12h provided acceptable factor activities. Here we assessed the activity of two clotting factor replacement therapies over a 24h period to guide clinical care protocols. Method This study was performed in the Special Coagulation Lab as a collaboration between pharmacy, hematology, and laboratory medicine. Two vials each of Novoeight, a recombinant antihemophilic factor used in patients with factor VIII deficiency, and Vonvendi, a recombinant von Willebrand Factor (VWF) replacement approved for prophylaxis in adults with Type 3 von Willebrand Disease, were reconstituted to clinically relevant potencies (13 IU/ml, Novoeight; 27 IU/ml, Vonvendi). Products were spiked separately into factor VIII-deficient plasma (Novoeight) or assay diluent (Vonvendi), given inability to obtain VWF-deficient plasma, and tested for activity at various timepoints. Novoeight samples were assessed by traditional one-stage FVIII assays, while Vonvendi samples were assessed for VWF antigen, ristocetin cofactor activity (RCA), and glycoprotein Ib binding activity (GP1bM). Results Novoeight samples maintained similar FVIII activities at all timepoints tested, with differences falling within the coefficient of variation of the assay. Specifically, the two samples had FVIII levels of 108% and 95% at baseline and levels of 98% and 91%, respectively, at 12h, which was the timepoint of greatest interest given plans to allow 12h infusion rates. For Vonvendi samples, measurement of VWF antigen remained fairly stable throughout the 24h period. However, VWF activity decreased in both RCA and GP1bM assays over time, including by 4h. RCA values were 193% and 190% at baseline, 113% and 95% at 4h, and 63% and 63% at 12h. GP1bM was 140% and 133% at baseline, 92% and 91% at 4h, and 56% and 70% at 12h. Together, these results supported implementation of protocols allowing for extended (up to 12h) infusion of Novoeight and short (3-5min) bolus infusion of Vonvendi. Conclusion Our study demonstrated maintained Novoeight activity over the study period, confirming infusion rates of 12h should be efficacious. Conversely, Vonvendi yielded significantly decreased activity levels in as little as 4h, indicating the need for faster infusion rates. Based on our results, current practices at our institution were adapted to include extended infusion for Novoeight only. Drug activity studies may not directly reflect patient outcomes, and additional studies of factor activities following product infusion into patients and clinical hemostasis correlates are necessary. Nevertheless, the clinical lab should continue to play a primary role in testing, monitoring, and developing patient care protocols for therapeutic drugs through multidisciplinary collaboration.

Gene therapy for hemophilia

Concept Gene therapy with adeno-associated virus (AAV) vectors treats hemophilia A or B by delivering a functional F8 or F9 gene to hepatocytes. This single infusion enables endogenous production of FVIII or FIX protein, reducing bleeding in patients. Evolution Long-term clinical studies have provided insight into the efficacy, safety, and durability of AAV-mediated gene therapies for hemophilia A and B. Gene therapies have now been approved for hemophilia A (valoctocogene roxaparvovec) and hemophilia B (etranacogene dezaparvovec; fidanacogene elaparvovec) in select regions. Application The approved gene therapies are associated with a strong reduction in bleeding tendency and increased FVIII or FIX activity levels, without the need for additional FVIII or FIX replacement therapies, in the vast majority of patients. Future Steps Improvements in AAV technology, protein expression, and immunogenicity may render AAV-mediated gene therapies more efficient, longer lasting and safer for people with hemophilia A or B.

Blood coagulation in Prediabetes clusters–impact on all-cause mortality in individuals undergoing coronary angiography

BackgroundMetabolic clusters can stratify subgroups of individuals at risk for type 2 diabetes mellitus and related complications. Since obesity and insulin resistance are closely linked to alterations in hemostasis, we investigated the association between plasmatic coagulation and metabolic clusters including the impact on survival.MethodsUtilizing data from the Ludwigshafen Risk and Cardiovascular Health (LURIC) study, we assigned 917 participants without diabetes to prediabetes clusters, using oGTT-derived glucose and insulin, high-density lipoprotein cholesterol, triglycerides, and anthropometric data. We performed a comprehensive analysis of plasmatic coagulation parameters and analyzed their associations with mortality using proportional hazards models. Mediation analysis was performed to assess the effect of coagulation factors on all-cause mortality in prediabetes clusters.ResultsPrediabetes clusters were assigned using published tools, and grouped into low-risk (clusters 1,2,4; n = 643) and high-risk (clusters 3,5,6; n = 274) clusters. Individuals in the high-risk clusters had a significantly increased risk of death (HR = 1.30; CI: 1.01 to 1.67) and showed significantly elevated levels of procoagulant factors (fibrinogen, FVII/VIII/IX), D-dimers, von-Willebrand factor, and PAI-1, compared to individuals in the low-risk clusters. In proportional hazards models adjusted for relevant confounders, elevated levels of fibrinogen, D-dimers, FVIII, and vWF were found to be associated with an increased risk of death. Multiple mediation analysis indicated that vWF significantly mediates the cluster-specific risk of death.ConclusionsHigh-risk prediabetes clusters are associated with prothrombotic changes in the coagulation system that likely contribute to the increased mortality in those individuals at cardiometabolic risk. The hypercoagulable state observed in the high-risk clusters indicates an increased risk for cardiovascular and thrombotic diseases that should be considered in future risk stratification and therapeutic strategies.Graphical

Norepinephrine versus phenylephrine affects prethrombotic response in patients undergoing cesarean section under spinal anesthesia: a randomized, double-blind, controlled study.

Venous thromboembolism (VTE) is one of the most common and serious complications of cesarean section in parturients. Norepinephrine (NE) has been shown to activate coagulation. The aim of this study was to compare the effect of a fixed-rate prophylactic norepinephrine infusion and a fixed-rate prophylactic phenylephrine（PHE） infusion under spinal anesthesia for caesarean section on the prethrombotic response. Sixty-six women undergoing cesarean section under spinal anesthesia were randomly assigned to the NE group or PHE group, starting simultaneously with the administration of the subarachnoid solution, a "study drug" solution containing either NE or PHE was pumped intravenously at a constant rate of 15 ml/h until the end of the operation. Plasma coagulation factor VIII activity (FVIII: C), Fibrinogen, and D-dimer levels were measured in blood samples obtained on admission to the operating theatre and at the end of the procedure. Compared with preoperative levels, there were no significant differences in postoperative fibrinogen and D-dimer levels in the NE group, except for a decrease in FVIII: C levels (P = 0.003). However, postoperative levels of FVIII: C (P = 0.009), fibrinogen (P = 0.035) and D-dimer (P = 0.025) were increased in the NE group compared with postoperative levels in the PHE group. NE does not affect the maternal prethrombotic response and can be safely used in cesarean sections. Compared with PHE infusion, NE infusion increased the level of coagulation molecules, suggesting that NE maybe more beneficial for women with high intraoperative bleeding requiring hemostasis.

Efficacy of a 1:1 ratio VWF/FVIII concentrate in patients with von Willebrand disease.

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. 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 (24-120h). 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 35.7IU/kg CFC, recovery rates of FVIII and VWF were 2.6IU/dL per IU/kg and 2.4IU/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. 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.

Every minute counts: A comparison of thawing times and haemostatic quality of plasma thawed at 37°C and 45°C using four different methods.

Having faster plasma thawing devices could be beneficial for transfusion services, as it may improve the rapid availability of thawed plasma for bleeding patients, and it might remove the need to have extended pre-thawed plasma: thus, reducing unnecessary plasma wastage. The aims of this study were to assess (a) the thawing times and (b) in vitro haemostatic quality of thawed plasma using Barkey Plasmatherm V (PTV) at 37 and 45°C versus Barkey Plasmatherm Classic (PTC) at 37 and 45°C, Sarstedt Sahara-III Maxitherm (SS-III) at 37°C and Helmer Scientific Thermogenesis Thermoline (TT) at 37°C. Haemostatic quality was assessed using LG-Octaplas at three different time points: baseline (5 min), 24 and 120 h after thawing. The thawing time (SD) of 2 and 4 units was significantly different between different thawers. PTV at 45°C was the fastest method for both 2 and 4 units (7.06 min [0.68], 9.6 min [0.87], respectively). SS-III at 37°C being the slowest method (24.69 min [2.09] and 27.18 min [4.4], respectively) (p = < 0.05). Baseline measurements for all assays showed no significant difference in the prothrombin time, fibrinogen, FII, FV, protein C activity or free protein S antigen between all methods tested. However, at baseline PTV (both 37°C and 45°C) had significantly higher levels of FVII, FVIII and FXI and shortened activated partial thromboplastin time. PTV was the quickest method at thawing plasma at both 37 and at 45°C. The haemostatic quality of plasma thawed at 45 versus 37°C was not impaired. Thawing frozen plasma at 45°C should be considered.

Bleeding phenotype according to factor level in 825 children with nonsevere hemophilia: data from the PedNet cohort

BackgroundInformation on bleeding phenotype in nonsevere hemophilia may be used to determine target factor levels for prophylaxis or gene therapy in severe hemophilia. ObjectivesTo assess the association between endogenous factor level and bleeding phenotype in children with nonsevere (factor [F]VIII/FIX activity 1%-25%) hemophilia A (HA) and B without prophylaxis. MethodsData on annualized bleeding rate (ABR), annualized joint bleeding rate (AJBR), and onset of bleeding were extracted from the international PedNet cohort including children born since 2000. Mean ABR and AJBR were modeled and compared according to FVIII/FIX endogenous activity (1%-2%, 3%-5%, 6%-10%, 11%-15%, 16%-20%, and 21%-25%) using negative binomial regression. Onset of bleeding was analyzed using Kaplan–Meier survival curves. ResultsEight hundred twenty-five children (40% with moderate hemophilia; 87% with HA) with median follow-up of 7.4 years/child were included. The median age at onset of bleeding and median bleeding rates changed with increasing endogenous activity. From endogenous FVIII 1% to 2% to 21% to 25%, the age at onset of bleeding changed from a median of 1.4 to 14.2 years, ABR from 1.6 to 0.1/y, and AJBR from 0.5 to 0.0/y. From endogenous FIX 1% to 2% to 16% to 25%, the onset of bleeding changed from a median of 1.7 to 6.1 years, ABR from 0.5 to 0.1/y, and AJBR from 0.1 to 0.0/y. The negative correlation between AJBR and factor level was most strongly pronounced up to a factor level of 6% in HA and hemophilia B. ConclusionEndogenous factor activity of >5% was identified as a threshold to significantly lower joint bleeding rate, while FVIII levels >15% and FIX levels >10% were sufficient to achieve the goal of 0 bleeds in this pediatric cohort.

Hepatitis after gene therapy, what are the possible causes?

Hepatitis is a common adverse event following gene therapy for haemophilia, often associated with a loss of transgene expression. Investigating the potential causes and implications of this is crucial for the overall success of treatment. Gene therapy trials using adeno-associated virus (AAV) vectors have demonstrated promising results marked by increases in factor FVIII and FIX levels and reductions in episodes of bleeding. However, hepatocellular injury characterised by elevations in alanine aminotransferases (ALT) has been noted. This liver injury is typically transient and asymptomatic, posing challenges in determining its clinical significance. Proposed causes encompass immune-mediated responses, notably T cell cytotoxicity in response to the AAV vector, direct liver injury from the viral capsid or transcribed protein via the unfolded protein response and pre-existing liver conditions. Liver biopsy data conducted years post-gene therapy infusion has shown sinusoidal infiltration without significant inflammation. The overall safety profile of gene therapy remains favourable with no evidence drug-induced liver injury (DILI) based on Hy's Law criteria. Essential pre-therapy monitoring and identifying patients at high risk of liver injury should involve liver function tests and non-invasive fibroscans, while novel blood-based biomarkers are under exploration. Further research is required to comprehend the mechanisms underlying transaminitis, loss of transgene expression and long-term effects on the liver, providing insights for optimising gene therapy for haemophilia.

Current and emerging gene therapies for haemophilia A and B.

After decades of stumbling clinical development, the first gene therapies for haemophilia A and B have been commercialized and have normalized factor (F)VIII and factor (F)IX levels in some individuals in the long term. Several other clinical programs testing adeno-associated viral (AAV) vector gene therapy are at various stages of clinical testing. Multiyear follow-up in phase 1/2 and 3 studies showed long-term and sometimes curative but widely variable and unpredictable efficacy. Liver toxicities, mostly low-grade, occur in the 1st year in at least some individuals in all haemophilia A and B trials and are poorly understood. Wide variability and unpredictability of outcome and slow decline of FVIII levels are a major disadvantage because immune responses to AAV vectors preclude repeat dosing, which otherwise could improve suboptimal or restore declining expression, while overexpression may predispose to thrombosis. Long-term safety outcomes will need lifelong monitoring because AAV vectors infused at high doses integrate into chromosomes at rates that raise questions about potential oncogenicity and necessitate vigilance. Alternative gene transfer systems employing gene editing and/or non-viral vectors are under development and promise to overcome some limitations of the current state of the art for both haemophilia A and B. AAV gene therapies for haemophilia have now become new treatment options but not universal cures. AAV is a powerful but imperfect gene transfer platform. Biobetter FVIII transgenes may help solve some problems plaguing gene therapy for haemophilia A. Addressing variability and unpredictability of efficacy, and delivery of gene therapy to ineligible patient subgroups may require different gene transfer systems, most of which are not ready for clinical translation yet but bring innovations needed to overcome the current limitations of gene therapy.

Assessment of Factor VIII Activity and D-Dimer Levels in the Post-COVID Period.

Changes in the hemostatic system during COVID infection lead to hypercoagulability. Numerous studies have evaluated hemostatic abnormalities in COVID patients during acute infection, in the period of hospitalization. However, the hemostatic status following hospital discharge has not been sufficiently assessed. Considering the importance of FVIII and D-dimer levels as markers for the assessment of thrombosis, our study aimed to evaluate changes in these markers, as well as the influence of patient's age and clinical presentation of COVID infection on those hemostatic markers in the post-COVID phase. This prospective study (July 2020 to December 2022) included 115 COVID patients, 68 (59%) with asymptomatic/mild and 47 (41%) with moderate/severe clinical presentation. Patient follow-up included laboratory evaluation of FVIII and D-dimer levels at 1, 3, and 6 months following the COVID infection. Three months after the COVID infection, elevated FVIII was recorded in 44% of younger versus 65% of older individuals, p = 0.05, respectively, and 30 versus 57% (p = 0.008) 6 months post-COVID infection. With a focus on clinical presentation, a higher number of patients with moderate/severe COVID had elevated FVIII activity, but a statistically significant difference was observed only for the 6 months (32% mild vs. 53% moderate/severe, p = 0.041) post-infection time point. Following a COVID infection, an increase in FVIII activity suggests a continued hypercoagulable state in the post-COVID period and correlates with elevated D-dimer levels. This increase in FVIII is more pronounced in patients with moderate/severe clinical picture and those patients older than 50 years.

A Generative and Causal Pharmacokinetic Model for Factor VIII in Hemophilia A: A Machine Learning Framework for Continuous Model Refinement.

In rare diseases, such as hemophilia A, the development of accurate population pharmacokinetic (PK) models is often hindered by the limited availability of data. Most PK models are specific to a single recombinant factor VIII (rFVIII) concentrate or measurement assay, and are generally unsuited for answering counterfactual ("what-if") queries. Ideally, data from multiple hemophilia treatment centers are combined but this is generally difficult as patient data are kept private. In this work, we utilize causal inference techniques to produce a hybrid machine learning (ML) PK model that corrects for differences between rFVIII concentrates and measurement assays. Next, we augment this model with a generative model that can simulate realistic virtual patients as well as impute missing data. This model can be shared instead of actual patient data, resolving privacy issues. The hybrid ML-PK model was trained on chromogenic assay data of lonoctocog alfa and predictive performance was then evaluated on an external data set of patients who received octocog alfa with FVIII levels measured using the one-stage assay. The model presented higher accuracy compared with three previous PK models developed on data similar to the external data set (root mean squared error = 14.6 IU/dL vs. mean of 17.7 IU/dL). Finally, we show that the generative model can be used to accurately impute missing data (< 18% error). In conclusion, the proposed approach introduces interesting new possibilities for model development. In the context of rare disease, the introduction of generative models facilitates sharing of synthetic data, enabling the iterative improvement of population PK models.

The influence of dead space in blood sampling needle on FVIII level and pharmacokinetic profiles in children with hemophilia

ABSTRACT Objective To investigate the influence of the dead space in disposable blood sampling needle on activated partial thromboplastin time (APTT), FVIII level and pharmacokinetic (PK) profiles in children with hemophilia. Methods Children (<18 years) with severe hemophilia A were enrolled. After three days’ washout-period, blood samples were collected at pre-dose, 1 h, 3 h, 9 h, 24 h and 48 h post-infusion. At each timepoint, two 2 mL vacuum tubes with 3.2% trisodium citrate were used. The first tube was signed as ‘non-standard’ (NS) and the second tube was signed as ‘standard’ (S). FVIII activities were evaluated by one-stage assay. WAPPS-Hemo was used to generate PK profiles like half-life time (t1/2), clearance (CL), trough level and time to 1, 2 and 5IU/dL after a dose of 50 ± 10IU/dL. The FVIII activities at 9 h and 24 h post-infusion were put into WAPPS and thus brought four combinations by true or biased FVIII level that used. Result Compared with standard-collected blood samples, prolonged APTT results (P-values < 0.01) and decreased FVIII activity (P-values < 0.05) were revealed in those non-standard blood samples. The corresponding bias was in positive relation to both APTT-S (r = 0.44, P < 0.0001) and FVIII-S level(r = 0.68, P < 0.001). The FVIII bias percentage got larger as FVIII-S level reduced (r = −0.24, P < 0.01). During the four combinations of FVIII activity at 9 h and 24 h, statistically longer t1/2, lower CL and longer time to 1, 2 or 5IU/dL were observed in 9H-S&24H-S group and 9H-NS&24H-S group. Conclusion While using vacuum tubes for clotting indicators and PK profiles, the dead space of blood sampling needle should be eliminated in advance.