Predictive performance of pharmacokinetic-guided prophylactic dosing of factor concentrates in hemophilia A and B.

Background: Pharmacokinetic (PK)-guided dosing is used to individualize factor (F)VIII and FIX replacement therapy. Objectives: This study investigates the reliability and feasibility of PK-guided prophylactic dosing of factor concentrates in hemophilia A and B. Methods: In this multicenter, prospective cohort study, people of all ages with hemophilia received prophylactic treatment with factor concentrates based on individual PK parameters. During follow-up, at least 4 measured FVIII/FIX levels per patient were compared with corresponding predicted levels obtained by Bayesian forecasting. Predictive performance was defined as adequate when ≥80% of measured FVIII/FIX levels were within ±25% of prediction (relative error). Additionally, mean absolute error and mean error were calculated. In post hoc analyses, predictive performance was assessed allowing maximum absolute errors of 1 (trough), 5 (mid), and 15 (peak) IU/dL. Five-point scale questionnaires addressed feasibility of PK guidance. Results: We included 50 patients (median age, 19 years; range: 2-72 years). Median follow-up was 36 weeks. Seventy-one percent of levels (58% trough, 83% mid, and 80% peak) were within ±25% of prediction. Mean absolute errors were 0.8 (trough), 2.0 (mid), and 8.6 (peak) IU/dL. In post hoc analyses, 81% (trough), 96% (mid), and 82% (peak) of levels were within set limits. Patients reported low burden and high satisfaction. Conclusion: PK-guided dosing was reliable according to post hoc analyses, based on low absolute errors that were regarded as clinically irrelevant in most cases. The predefined predictive performance was achieved in mid and peak factor levels but not in trough factor levels due to measurement inaccuracy. PK guidance also seemed feasible.

Navigating the challenges: a case report on managing a complicated postpartum course in type 3 von Willebrand disease with alloantibodies.

Background: Von Willebrand disease (VWD) type 3 is characterized by a complete deficiency of von Willebrand factor (VWF), resulting in a severe bleeding phenotype. Treatment often requires administration of VWF concentrates/factor (F)VIII. However, the development of alloantibodies is a rare complication, resulting in ineffective recovery and allergic reactions. Emicizumab, a bispecific antibody mimicking FVIII function, has emerged as a potential alternative, with promising results reported in several case reports. Key Clinical Question: Description of multiple approaches to control highly severe postpartum hemorrhage in type 3 VWD with alloantibodies, including off-label use of emicizumab. Clinical Approach: Here we present a 28-year-old patient with type 3 VWD and alloantibodies, known to have arthropathy of the right elbow. Previous immune tolerance induction was unsuccessful. Despite receiving negative pregnancy advice during preconception counseling, the patient became pregnant. Delivery was induced at 38 4/7 weeks with prostaglandin, and recombinant FVIIa (rFVIIa) was administered every 2 hours. Despite administration of rFVIIa, bleeding persisted, requiring manual placental removal and insertion of a Bakri balloon. Since bleeding persisted, plasma-derived VWF was administered with an initial excellent recovery and successful embolization of the uterine artery. Twelve days postpartum, she developed endometritis and recurrent vaginal bleeding treated with antibiotics, rFVIIa every 2 hours, and multiple erythrocyte transfusions. Plasma-derived VWF was administered but was complicated by anaphylaxis and no recovery. Due to persistent vaginal bleeding, reembolization of uterine arteries was performed and off-label emicizumab was initiated. Twenty-nine days postpartum, she developed septic shock requiring an abdominal hysterectomy, again complicated by severe bleeding necessitating direct intraabdominal packing after rFVIIa. A computed tomography scan 9 days postsurgery revealed thrombosis in the left iliac vein and asymptomatic pulmonary embolisms. rFVIIa was stopped and prophylactic low-molecular-weight heparin was started. The patient was discharged 2 months after delivery on low-dose low-molecular-weight heparin, emicizumab, and antibiotics for an intra-abdominal abscess. During 2.5 years of emicizumab prophylaxis, she has had no rebleeding in her arthropathic right elbow. Conclusion: The current case emphasizes the postpartum clinical challenges of patients with type 3 VWD and alloantibodies. It underscores the potential role of emicizumab in maintaining hemostatic control.

Limited value of testing for factor XIII and α2-antiplasmin deficiency in patients with a bleeding disorder of unknown cause.

INTRODUCTION: In patients with an increased bleeding tendency, extensive diagnostic blood testing is often performed. When results of tier 1 assays of primary haemostasis are normal, protocols recommend additional testing to rule out rare disorders including coagulation factor XIII (FXIII) and α2-antiplasmin (α2AP) deficiency. AIM: To evaluate the added diagnostic value of FXIII and α2AP levels in patients with a bleeding disorder of unknown cause (BDUC). METHODS: A retrospective monocentre cohort study between August 2011 and August 2023 was conducted. In all patients with bleeding tendencies and normal diagnostic tests for von Willebrand disease and platelet function, FXIII and α2AP were measured. RESULTS: We included 158 consecutive patients; mean ISTH-BAT scores were 8.2 (SD ± 3.7) in children, 6.2 (SD ± 2.1) in men and 10.6 (SD ± 3.3) in women. Median age was 37 (range 5-79) years, 88.6% of patients were female. Patients displayed median FXIII activity of 111% (IQR = 97-131) and median α2AP activity of 112% (IQR = 103-119). Three (1.9%) patients had FXIII levels < 50%, respectively 43%, 45% and 46%. Corresponding ISTH-BAT scores were 7, 12 and 14. No α2AP levels < 60% was observed. No significant association was found between FXIII levels and ISTH-BAT scores. CONCLUSION: In our cohort of BDUC patients, no clinical relevant FXIII deficiencies were detected; absolute values were well above the 30% cutoff considered adequate for normal haemostasis. No α2AP deficiencies were detected. These data suggest that in BDUC patients, measuring FXIII or AP activity is of limited value.

Towards Personalized Treatment in Haemophilia: The Role of Genetic Factors in Iron and Heme Control to Identify Patients at Risk for Haemophilic Arthropathy.

The treatment landscape for haemophilia is changing rapidly, creating opportunities for personalized treatment. As major morbidity is still caused by haemophilic arthropathy, understanding the factors affecting joint damage and joint damage progression might lead to more individualized treatment regimens. We investigated the association of HFE mutations or HMOX1 polymorphisms affecting iron/heme handling with radiographic joint damage in 252 haemophilia patients (severe and moderate). Although iron levels and transferrin saturation were significantly increased in the 95 patients with an HFE mutation, neither carrying this mutation nor the HMOX1 polymorphism was associated with radiographic joint damage, and the same was true after adjustment for well-known factors associated with arthropathy. In conclusion, this study does not support the hypothesis that HFE mutations or HMOX1 polymorphisms can be used to predict the development of haemophilic arthropathy.

Recombinant porcine factor VIII in patients with congenital haemophilia A with inhibitors undergoing surgery: Phase 3, single-arm, open-label study.

INTRODUCTION: Recombinant porcine factor VIII (rpFVIII; susoctocog alfa) is predicted to provide functional FVIII activity in patients with congenital haemophilia A with inhibitors (CHAWI). AIMS: To evaluate the efficacy and safety of rpFVIII in patients with CHAWI undergoing invasive procedures. METHODS: This phase 3, multicentre, single-arm, open-label study (NCT02895945) enrolled males aged 12-75 years with severe/moderately severe CHAWI who required surgical/invasive procedures. Patients received a loading dose of rpFVIII 1-2 h before surgery. The primary outcome was the proportion of all procedures with a 'good' or 'excellent' response (treatment success) on the global haemostatic efficacy assessment score. RESULTS: Of the eight dosed patients, five completed the study. Six of seven surgeries (85.7%; 95% confidence interval, 42.1-99.6) achieved treatment success; five were rated 'excellent', one was rated 'good'. Seven surgery-related bleeding episodes occurred in three patients during the study, with none requiring additional surgical intervention. Overall, six of eight patients experienced 17 treatment-emergent adverse events. Three patients developed de novo inhibitors to rpFVIII. Five patients reported anamnestic reactions, three to both human (h) FVIII (i.e., alloantibodies to exogenous FVIII detected with anti-hFVIII assays) and rpFVIII, and two to hFVIII only. Four serious adverse events were considered related to rpFVIII (three anti-rpFVIII antibody positive; one anamnestic reaction to hFVIII and rpFVIII). CONCLUSION: Good haemostasis was achieved with rpFVIII during the immediate perioperative period. The study was terminated early because the study sponsor and health authorities determined that the risk of anamnestic reactions outweighs the benefits in this study population.

Surgical Experience from the STASEY Study of Emicizumab Prophylaxis in People with Hemophilia A with Factor VIII Inhibitors.

Background Guidelines surrounding emicizumab prophylaxis and perioperative treatment for people with hemophilia A (PwHA) with factor (F)VIII inhibitors undergoing surgeries are limited. The phase IIIb multicenter, single-arm STASEY study evaluated safety and tolerability of emicizumab prophylaxis in PwHA aged ≥12 years with FVIII inhibitors. This analysis assesses surgeries during study conduct, associated hemophilia medications, and postoperative bleeds (treated and untreated). Methods PwHA with FVIII inhibitors received emicizumab 3.0 mg/kg/week for 4 weeks, then 1.5 mg/kg/week until 2 years. Surgeries were managed and documented by treating physicians. Bleeds and treatments were recorded by physicians and participants. Results Forty-six participants had ≥1 on-study surgery, 37 underwent 56 minor surgeries, and 13 underwent 22 major surgeries. Four participants underwent both minor and major surgeries. Of 18 (81.8%) and 4 (18.2%) major surgeries managed with/without additional hemostatic medication, 33.3 and 25.0% were associated with a treated postoperative bleed, respectively. Of 24 (42.9%) and 32 (57.1%) minor surgeries managed with/without additional hemostatic medication, 15.6 and 25.0% were associated with a treated postoperative bleed, respectively. Recombinant activated FVII was the most common medication for prophylaxis and bleed treatment. There were no thrombotic microangiopathies (TMAs). One hypertrophic clot, considered unrelated to emicizumab, occurred following tooth extraction. Conclusion In this challenging population with a high bleeding risk, major surgeries were performed in PwHA receiving emicizumab with/without additional hemostatic medication. Postoperative bleeds occurred following 59.1% of major surgeries; 53.8% were treated. No arterial/venous thrombotic events or TMAs occurred due to concomitant emicizumab and bypassing agents. Trial registration This trial is registered at ClinicalTrials.gov (NCT03191799).

Congenital fibrinogen disorders: a retrospective clinical and genetic analysis of the Prospective Rare Bleeding Disorders Database.

ABSTRACT: Congenital fibrinogen deficiency (CFD) is a rare bleeding disorder caused by mutations in FGA, FGB, and FGG. We sought to comprehensively characterize patients with CFD using PRO-RBDD (Prospective Rare Bleeding Disorders Database). Clinical phenotypes, laboratory, and genetic features were investigated using retrospective data from the PRO-RBDD. Patients were classified from asymptomatic to grade 3 based on their bleeding severity. In addition, FGA, FGB, and FGG were sequenced to find causative variants. A total of 166 CFD cases from 16 countries were included, of whom 123 (30 afibrinogenemia, 33 hypofibrinogenemia, 55 dysfibrinogenemia, and 5 hypodysfibrinogenemia) were well characterized. Considering the previously established factor activity and antigen level thresholds, bleeding severity was correctly identified in 58% of the cases. The rates of thrombotic events among afibrinogenemic and hypofibrinogenemic patients were relatively similar (11% and 10%, respectively) and surprisingly higher than in dysfibrinogenemic cases. The rate of spontaneous abortions among 68 pregnancies was 31%, including 86% in dysfibrinogenemic women and 14% with hypofibrinogenemia. Eighty-six patients received treatment (69 on-demand and/or 17 on prophylaxis), with fibrinogen concentrates being the most frequently used product. Genetic analysis was available for 91 cases and 41 distinct variants were identified. Hotspot variants (FGG, p.Arg301Cys/His and FGA, p.Arg35Cys/His) were present in 51% of dysfibrinogenemia. Obstetric complications were commonly observed in dysfibrinogenemia. This large multicenter study provided a comprehensive insight into the clinical, laboratory, and genetic history of patients with CFDs. We conclude that bleeding severity grades were in agreement with the established factor activity threshold in nearly half of the cases with quantitative defects.

Heavy menstrual bleeding in adolescents: incidence, diagnostics, and management practices in primary care.

Background: Heavy menstrual bleeding (HMB), self-reported by 37% of adolescents, can be the first sign of a bleeding disorder (BD) during adolescence. The Dutch general practitioner (GP) guideline demands laboratory diagnostics and referral for patients at risk for a BD. How often adolescents consult the GP for HMB and which diagnostic and management strategies are used are unknown. Objectives: This study aims to estimate the incidence of HMB in adolescents in primary care and to identify diagnostic and management practices for HMB, considering the HMB GP guideline. Methods: Retrospective analyses of a GP network database containing over 200 Dutch GPs were performed. Adolescents aged 10 to 21 years, with a new diagnosis of HMB between 2010 and 2020, and a 6-month follow-up were eligible. The incidence rate and diagnostic and therapeutic strategy data were extracted. Results: We identified 1879 new diagnoses of HMB in adolescents. The average incidence rate was 7.91 per 1000 person-years. No diagnostic studies were performed in 67%. Laboratory studies were mainly restricted to hemoglobin levels (31%). Full coagulation screening occurred in 1.3%, and ferritin levels in 10%. Medication was prescribed in 65%; mostly hormonal treatment (56%) and/or nonsteroidal antiinflammatory drugs (NSAIDs) (18%). The referral rate was higher after >2 follow-up visits (6.7%) vs after 1 GP visit for HMB (1.6%; Odds ratio: 8.8; 95% CI: 5.1-15), mostly to gynecologists (>85%). Conclusion: According to this GP database study, few adolescents visit their GP with HMB despite its high self-reported incidence. Most adolescents were prescribed hormonal contraception without further diagnostics. Referral was rare and mostly occurred after multiple follow-up visits.

One-year safety and efficacy of mitapivat in sickle cell disease: follow-up results of a phase 2, open-label study.

Targeting the primary pathogenic event of sickle cell disease (SCD), the polymerization of sickle hemoglobin (HbS), may prevent downstream clinical events. Mitapivat, an oral pyruvate kinase (PK) activator, has therapeutic potential by increasing adenosine triphosphate (ATP) and decreasing 2,3-diphosphoglycerate (2,3-DPG), a glycolytic red blood cell (RBC) intermediate. In the previously reported 8-week dose-finding period of this phase 2, investigator-initiated, open-label study, mitapivat was well tolerated and showed efficacy in SCD. Here, the 1-year fixed-dose extension period is reported in which 9 of 10 included patients (90%) aged ≥16 years with SCD (HbSS, HbS/ß0, or HbS/ß+) continued with mitapivat. Mostly mild treatment-emergent adverse events (AEs) (most commonly, transaminase increase and headache) were still reported. Apart from the reported nontreatment-related serious AE (SAE) of a urinary tract infection in the dose-finding period, 1 nontreatment-related SAE occurred in the fixed-dose extension period in a patient who died of massive pulmonary embolism due to COVID-19. Importantly, sustained improvement in Hb level (mean increase, 1.1 ± 0.7 g/dL; P = .0014) was seen, which was accompanied by decreases in markers of hemolysis. In addition, the annualized rate of vaso-occlusive events reduced significantly from a historic baseline of 1.33 ± 1.32 to 0.64 ± 0.87 (P = .0489) when combining the dose-finding period and fixed-dose extension period. Cellularly, the ATP:2,3-DPG ratio and Hb-oxygen affinity significantly increased and RBC sickling (point of sickling) nonsignificantly reduced. Overall, this study demonstrated 1-year safety and efficacy of treatment with mitapivat in SCD, supporting further evaluation in ongoing phase 2/3 study (RISE UP, NCT05031780). This trial was registered at https://www.clinicaltrialsregister.eu/ as NL8517 and EudraCT 2019-003438-18.

Subclinical synovial proliferation in patients with severe haemophilia A: The value of ultrasound screening and biochemical markers.

AIM: Subclinical bleeding and inflammation play a role in progression of haemophilic arthropathy. Synovial proliferation is predictive of joint bleeding and its early detection may guide treatment changes and prevent arthropathy progression. This study evaluated the prevalence of active and inactive subclinical synovial proliferation and investigated potential biochemical blood/urine markers to identify patients with active subclinical synovial proliferation. METHODS: This cross-sectional study included patients with severe haemophilia A born 1970-2006 who were evaluated during routine clinic visits. Patients with (a history of) inhibitors or recent joint bleeding were excluded. Elbows, knees and ankles were examined for subclinical synovial proliferation by ultrasound and physical examination. Active synovial proliferation was distinguished from inactive synovial proliferation using predefined criteria. Blood/urine biochemical markers (serum osteopontin, sVCAM-1, Coll2-1, COMP, CS846, TIMP, and urinary CTX-II) were compared individually and as combined indexes between patients with and without active synovial proliferation. RESULTS: This cohort consisted of 79 patients with a median age of 31 years (range 16.5-50.8 years) with 62/79 (78%) of the patients using continuous prophylaxis. The annualized joint bleeding rate over the last 5 years was .6 (.2-1.1). Active (17/79, 22%) and inactive subclinical synovial proliferation (17/79, 22%) were both prevalent in this cohort. Biochemical markers were not correlated with active subclinical synovial proliferation. CONCLUSION: Subclinical synovial proliferation, both active and inactive, was prevalent in patients with severe haemophilia A with access to prophylaxis and would be overlooked without routinely performed ultrasounds. Biochemical markers were unable to identify patients with active subclinical synovial proliferation.

High prevalence of heavy menstrual bleeding in women with rare bleeding disorders in the Netherlands: retrospective data from the RBiN study.

BACKGROUND: Heavy menstrual bleeding (HMB) is associated with a reduced quality of life and limitations in social and physical functioning. Data on HMB in women with rare bleeding disorders (RBDs), including coagulation factor deficiencies and fibrinolytic disorders, are scarce. OBJECTIVES: To analyze the prevalence, severity, and treatment of HMB in Dutch women with an RBD. METHODS: The Rare Bleeding Disorders in the Netherlands (RBiN) study included 263 patients with an RBD from all 6 hemophilia treatment centers (October 2017-November 2019). In this analysis, data of 111 women aged ≥16 years were studied. According to the International Society on Thrombosis and Haemostasis bleeding assessment tool, HMB symptoms were scored from 0 (no/trivial) to 4 (severe symptoms requiring medical intervention). HMB was defined as a score ≥1. Age at RBD diagnosis was extracted from patient files. RESULTS: HMB was reported by 80% of women (89/111) and was more prevalent in women with a fibrinolytic disorder (33/35; 94%) than in women with a coagulation factor deficiency (56/76; 74%) (P = .011). Of the 89 women with HMB, 82% (n = 73) ever required treatment. Multiple treatment modalities were frequently used, both in severe and mild deficiencies. Hormonal treatment was mostly used (n = 64; 88%), while antifibrinolytics were prescribed less frequently (n = 18; 25%). In women with HMB since menarche (n = 61; 69%), median age at RBD diagnosis was 28 years (IQR, 14-41). CONCLUSION: HMB is common in women with RBDs. Women with mild deficiencies also frequently reported HMB. Only a minority of women were treated with hemostatic agents. A significant diagnostic delay was observed after the onset of HMB symptoms.

No immunological changes after factor VIII product switch: An in depth analysis in haemophilia A patients.

BACKGROUND: A challenging complication in the treatment of haemophilia A is the formation of neutralizing anti-FVIII antibodies (inhibitors). There is ongoing debate on the effect of FVIII product and inhibitor risk, rendering patients and physicians reluctant to switch FVIII-products. AIM: This study aimed to evaluate changes in the immune profile of haemophilia A patients after switching FVIII products and their possible relation to inhibitor development. Secondary, FVIII efficacy after switching were assessed. METHODS: Patients, who switched FVIII-products between 2017-2019, were included in this single centre cohort study. Prospective comparison of immunoregulatory cells and markers by flow-cytometry before and after the switch was performed in a subgroup. For the total cohort clinical data regarding inhibitor development and FVIII efficacy 1 year before and after switching were retrospectively collected. RESULTS: One-hundred patients (including 39 with prospective immunological assessment) were analyzed, of which 31% switched from plasma-derived (pdFVIII) to recombinant standard half-life FVIII (SHL-rFVIII), 47% between different SHL-rFVIII, and 22% from pdFVIII/SHL-rFVIII to rFVIII-Fc. No remarkable changes in immunoregulatory cell functions were observed after switching, regardless the type of switch. None of the patients developed an inhibitor. FVIII efficacy, that is, FVIII usage, half-life and annual bleeding rate (ABR), was similar before and after switch for the SHL products, whereas rFVIII-Fc associated with a longer half-life (13.1 vs. 15.0 h) and lower ABR (3.0 vs. 1.0). CONCLUSIONS: Switching to a different FVIII product was not associated with inhibitor development, nor with differences in the immune profile. Switching to rFVIII-Fc lead to lower ABR.

Anti-ß2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies interfere with cleavage of factor V(a) by activated protein C.

BACKGROUND: The acquired thrombotic risk factor known as lupus anticoagulant (LA) interferes with laboratory clotting assays and can be caused by autoantibodies against ß2-glycoprotein I (ß2GPI) and prothrombin. LA is associated with activated protein C (APC) resistance, which might contribute to thrombotic risk in patients with antiphospholipid syndrome. How antibodies against ß2GPI and prothrombin cause APC resistance is currently unclear. OBJECTIVES: To investigate how anti-ß2GPI and antiphosphatidylserine/prothrombin (PS/PT) antibodies induce APC resistance. METHODS: The effects of anti-ß2GPI and anti-PS/PT antibodies on APC resistance were studied in plasma (of patients with antiphospholipid syndrome) and with purified coagulation factors and antibodies. RESULTS: APC resistance was observed in LA-positive patients with anti-ß2GPI or anti-PS/PT antibodies and in normal plasma spiked with monoclonal anti-ß2GPI or anti-PS/PT antibodies with LA activity. Analysis of factor (F)V cleavage patterns after APC incubation indicated that anti-ß2GPI antibodies attenuated APC-mediated FV cleavage at R506 and R306. APC-mediated cleavage at R506 is required for FV cofactor activity during inactivation of FVIIIa. Assays with purified coagulation factors confirmed that anti-ß2GPI antibodies interfered with the cofactor function of FV during FVIIIa inactivation but not with FVa inactivation. Anti-PS/PT antibodies attenuated APC-mediated FVa and FVIIIa inactivation. Analysis of FV(a) cleavage patterns after APC incubation indicated that anti-PS/PT antibodies interfere with APC-mediated cleavage of FV at positions R506 and R306. CONCLUSION: Anti-ß2GPI antibodies with LA activity contribute to a procoagulant state by causing APC resistance via interference with the cofactor function of FV during FVIIIa inactivation. LA-causing anti-PS/PT antibodies interfere with the anticoagulant function of APC by preventing FV(a) cleavage.

Toward responsible clinical n-of-1 strategies for rare diseases.

N-of-1 strategies can provide high-quality evidence of treatment efficacy at the individual level and optimize evidence-based selection of off-label treatments for patients with rare diseases. Given their design characteristics, n-of-1 strategies are considered to lay at the intersection between medical research and clinical care. Therefore, whether n-of-1 strategies should be governed by research or care regulations remains a debated issue. Here, we delineate differences between medical research and optimized clinical care, and distinguish the regulations which apply to either. We also set standards for responsible optimized clinical n-of-1 strategies with (off-label) treatments for rare diseases. Implementing clinical n-of-1 strategies as defined here could aid in optimized treatment selection for such diseases.

Antithrombotic Treatment in Patients With Hemophilia: an EHA-ISTH-EAHAD-ESO Clinical Practice Guidance.

Cardiovascular disease is an emerging medical issue in patients with hemophilia (PWH) and its prevalence is increasing up to 15% in PWH in the United States. Atrial fibrillation, acute and chronic coronary syndromes, venous thromboembolism, and cerebral thrombosis are frequent thrombotic or prothrombotic situations, which require a careful approach to fine-tune the delicate balance between thrombosis and hemostasis in PWH when using both procoagulant and anticoagulant treatments. Generally, PWH could be considered as being naturally anticoagulated when clotting factors are <20 IU/dL, but specific recommendations in patients with very low levels according to the different clinical situations are lacking and mainly based on the anecdotal series. For PWH with baseline clotting factor levels >20 IU/dL in need for any form of antithrombotic therapy, usually treatment without additional clotting factor prophylaxis could be used, but careful monitoring for bleeding is recommended. For antiplatelet treatment, this threshold could be lower with single-antiplatelet agent, but again factor level should be at least 20 IU/dL for dual antiplatelet treatment. In this complex growing scenario, the European Hematology Association in collaboration with the International Society on Thrombosis and Haemostasis, the European Association for Hemophilia and Allied Disorders, the European Stroke Organization, and a representative of the European Society of Cardiology Working Group on Thrombosis has produced this current guidance document to provide clinical practice recommendations for health care providers who care for PWH.

DosEmi study protocol: a phase IV, multicentre, open-label, crossover study to evaluate non-inferiority of pharmacokinetic-guided reduced dosing compared with conventional dosing of emicizumab in people with haemophilia A.

INTRODUCTION: Emicizumab effectively prevents bleeding in people with haemophilia A (PwHA), but is a burden for national healthcare budgets and consequently may limit access. According to the drug label, dosing of emicizumab is based on body weight with fixed intervals of 7, 14 or 28 days, which leads to mean plasma concentrations of 55 µg/mL (SD 15 µg/mL). However, a moderate variability of concentrations and a minimal effective concentration of 30 µg/mL have been suggested in studies. Therefore, a dose of emicizumab that targets a trough concentration of 30 µg/mL is hypothesised to be equally effective as conventional dosing in the prevention of bleeding. METHODS AND ANALYSIS: We designed a phase IV, multicentre, open-label, crossover study to evaluate non-inferiority of bleed control of ≥6 months on conventional dosing in comparison to ≥6 months on dose intervention. This dose intervention consists of reducing the dose of emicizumab to target a trough concentrations of 30 µg/mL using individual pharmacokinetic (PK) parameters. Ninety-five PwHA aged >1 years who received conventional dosing of emicizumab for ≥12 months with good bleeding control during the last 6 months will be recruited from all Dutch haemophilia treatment centres. The study is powered to detect a clinically relevant decrease (risk difference) of 15% in the proportion of patients without treated bleeds during follow-up. Secondary endpoints are spontaneous joint or muscle bleeds, and annualised treated bleeding rates (using negative binomial regression). Cost-effectivity between conventional dosing and individualised PK-guided dosing of emicizumab will be compared. ETHICS AND DISSEMINATION: The DosEmi study was approved by the Medical Ethics Review Committee NedMec of the University Medical Center of Utrecht, The Netherlands. Study results will be communicated through publications in international scientific journals and presentations at (inter)national conferences. TRIAL REGISTRATION NUMBER: EUCTR2021-004039-10-NL at https://trialsearch.who.int. PROTOCOL VERSION: V.4.1 on 28 October 2022 (DosEmi protocol_V4.1; NL81112.041.22).

Clotting factor activity levels and bleeding risk in people with haemophilia playing sports.

BACKGROUND: Improved treatment options for people with haemophilia (PWH) have increased the possibilities for sports participation, but the risk of sports-induced bleeding (SIB) is still considered considerable by many. AIM: To assess sports associated injury- and bleeding risk in PWH and to assess clotting levels associated with safe sports participation. METHODS: Sports injuries and SIBs were prospectively collected for 12 months in PWH aged 6-49 without inhibitors playing sports at least once weekly. Injuries were compared according to factor levels, severity, joint health, sports risk category and sports intensity. Factor activity at the time of injury was estimated using a pharmacokinetic model. RESULTS: 125 participants aged 6-49 (41 children, 90% haemophilia A; 48% severe, 95% severe on prophylaxis) were included. Sports injuries were reported by 51 participants (41%). Most participants (62%) reported no bleeds at all and only 16% reported SIBs. SIBs were associated with factor levels at time of injury (OR: 0.93/%factor level (CI 0.88-0.99); p = .02), but not with haemophilia severity (OR: 0.62 (CI 0.20-1.89); p = .40), joint health, sports risk category or sports intensity. PWH with factor levels <10% during sports injury had a bleeding risk of 41% versus 20% in those with higher (>10%) factor levels. CONCLUSION: The results of this study emphasize the importance of clotting factor levels in prevention of bleeds. This information is vital for patient counselling and tailoring prophylactic treatment with clotting factors and non-replacement therapy.

Acquired blood platelet disorder in patients with end-stage heart failure after implantation of a continuous centrifugal-flow left ventricular assist device: A prospective cohort study.

Background: Continuous-flow left ventricular assist devices (CF-LVADs) are an established therapy for advanced heart failure. Thrombosis and hemorrhage are common complications after CF-LVAD implantation, which may be explained by device-induced platelet activation. Few data on the effect of CF-LVAD implantation on platelets are available to date. Objectives: The aim of this study was to characterize the change in the platelet activation status after CF-LVAD. Methods: Platelet phenotype and reactivity were determined with flow cytometry in 32 adults with end-stage heart failure before and 4 to 6 weeks after CF-LVAD implantation. Sixteen adults with a biological aortic valve prosthesis (AVP) using the same antiplatelet regimen were included to discriminate between the effects of CF-LVAD and the antiplatelet regimen. Plasma markers for platelet activation were determined with enzyme-linked immunosorbent assay. Results: Median (IQR) plasma levels of soluble P-selectin increased from 115.6 (79.1-142.7) ng/mL to 144.5 (100.4-197.5) ng/mL after CF-LVAD implantation (P < .001). Median (IQR) ß-thromboglobulin levels were 60.5 (37.8-81.5) ng/mL before implantation and remained high after LVAD implantation [60.0 (42.0-69.5) ng/mL]. The platelet P-selectin expression after stimulation with ADP (30 and 60 µM) or PAR1-activating peptide (12.5 and 25 µM) was reduced by 17% to 21%, and fibrinogen binding was reduced by 37% to 86%. Platelet responses to agonists were similar in patients with a CF-LVAD and patients with an AVP, except for fibrinogen binding in response to 12.5 µM PAR1-AP, which was lower in patients with a CF-LVAD (P < .001). Conclusions: Combined, these data provide evidence for systemic platelet activation and an acquired platelet disorder after CF-LVAD implantation. This might contribute to the risk of both hemorrhage and thrombosis associated with CF-LVADs.