Lynn M. Malec

Extended half‐life factor VIII for immune tolerance induction in haemophilia

Prophylactic replacement therapy in severe haemophilia prevents bleeds and associated arthropathy [1] and is considered standard of care [2]. The FDA-approved long-acting recombinant factor VIII Fc fusion protein, rFVIIIFc (Eloctate), is safe and effective in prevention and treatment of bleeding events accomplished in two rather than three doses weekly, thereby simplifying treatment [3,4]. Prolonged protection is attributed to increased factor VIII (FVIII) half-life and areaunder-the-curve (AUC), resulting in longer time ≥0.01 IU mL , the level below which spontaneous bleeds occur [5]. rFVIIIFc may also promote tolerance to FVIII, as shown in preclinical animal models [6] and in an inhibitor-prone child [7], as Fc suppresses immunoregulatory T cells to proteins to which Fc is attached [8]. Whether rFVIIIFc is effective in suppressing inhibitor formation in haemophilia patients with existing inhibitors has not been studied. Given its immunoregulatory potential, we hypothesized rFVIIIFc might shorten and simplify ITI, which involves highdose daily FVIII, which is costly, invasive and ineffective in up to 20%. We, therefore, describe the use of rFVIIIFc in induction of ITI in three patients with severe haemophilia A and anti-VIII inhibitors. Immune tolerance induction was initiated with rFVIIIFc (Eloctate) in three children with severe haemophilia A and an anti-FVIII inhibitor. This included two children who had not previously undergone ITI and one individual who underwent salvage ITI after failing to achieve tolerance due to noncompliance with a prior daily rFVIII ITI taper regimen (Table 1). No patient had previously received rFVIIIFC; patient 1 had received rFVIII (Advate) prior to ITI, patient 2 had received rFVIII (Advate) prior to and with his failed prior ITI attempt, patient 3 had been treated abroad with pdFVIII and rFVIII (specifics unknown) and was receiving rFVIII (Kogenate) prior to ITI initiation with rFVIIIFc. ITI was initiated in the two patients beginning initial ITI once the inhibitor titre was <10 Bethesta Units (BU). Utilization of rFVIIIFc was at the discretion of the treating physician after discussion with the family; rFVIIIFc was utilized instead of a standard half-life product for reasons including avoidance of CVAD, decreased frequency of dosing and possible novel mechanisms to induce tolerance. ITI was performed using rFVIIIFc alone; patients did not receive additional immunosuppressive agents and were not on prophylaxis with bypassing agents. Follow-up was scheduled every 4–8 weeks, per institutional standard, with planned determination of FVIII recovery and half-life once the anti-FVIII fell to <0.6 BU. Tolerance was a priori defined as achieving anti-FVIII <0.6 BU, FVIII recovery of at least 60% and half-life ≥6 h [9]. FVIII half-life was determined by one-stage FVIII:C assay on citrate samples drawn preand 10 min, 1, 2, 4 and 6 h postinfusion of a single dose of rFVIIIFc; half-life estimates were calculated based on 1 h peak recovery. Inhibitor titres were determined by modification of the Nijmegen-Bethesda assay that includes heating patient plasma to 56°C for 30 min and centrifugation prior to testing which allows patients to avoid undergoing a rFVIIIFc washout period prior to sampling [10]. Once tolerance was achieved, incremental reduction of rFVIIIFc was performed based on pharmacokinetic data; once there was evidence of maintenance of inhibitor neutralization and a >6 h FVIII:C half-life rFVIIIFc was reduced to a dose of 50 IU kg 1 to 100 IU kg 1 every other day or three times weekly. Immune tolerance induction was initiated with rFVIIIFc via central venous access device or peripheral venipuncture in three children with severe haemophilia A and a history of an anti-FVIII inhibitor >5 BU (Table 1). Historic peak titres were 32 BU, 422 BU and 16 BU in patients 1, 2 and 3 respectively. In patient 2, who had previously undergone attempted ITI, he had a low titre inhibitor that was detected for approximately 4 years prior to undergoing ITI with rFVIIIFc and had been maintained on three times weekly rFVIII prophylaxis. Given his prior peak inhibitor of 422 BU and prior failure to achieve tolerance with prior ITI utilizing a standard half-life product, this patient was considered poor risk. The Correspondence: Lynn Malec, MD, MS, Assistant Professor of Medicine and Pediatrics, University of Pittsburgh School of Medicine, Associate Director, Hemophilia Center of Western Pennsylvania, 3636 Boulevard of the Allies, Pittsburgh, PA 15213, USA. Tel.: 412-692-5055; fax: 412-692-6675; e-mail: lynn.malec@chp.edu

Design of the INHIBIT trial: preventing inhibitors by avoiding ‘danger’, prolonging half-life and promoting tolerance

Inhibitor formation is among the most serious complications of hemophilia treatment. With the US FDA licensure of the novel long-lasting recombinant factor VIII (FVIII) Fc fusion protein, Eloctate, which prolongs FVIII half-life, we propose an innovative approach to prevent inhibitor formation. In this paper, we describe a multicenter, Phase II, single-arm, 48-week trial, the INHIBIT trial, to determine if Eloctate, begun before a bleed and continued as once weekly prophylaxis, will reduce inhibitor formation in children with hemophilia A. We hypothesize that avoiding ‘danger,’ that is, immune activation by a bleed at first factor exposure and prolonging FVIII half-life will prevent inhibitors and promote FVIII-specific T-cell tolerance. If successful, this approach will suggest a new paradigm in clinical practice.

Postpartum haemorrhage in women with von Willebrand disease: an observational study of the Pennsylvania Health Care Cost Containment Council (PHC4) database.

1 Plug I, Mauser-Bunschoten EP, Brocker-Vriends AH et al. Bleeding in carriers of hemophilia. Blood 2006; 108: 52–6. 2 Miesbach W, Alesci S, Geisen C, Oldenburg J. Association between phenotype and genotype in carriers of haemophilia A. Haemophilia 2011; 17: 246–51. 3 Mauser Bunschoten EP, van Houwelingen JC, Sjamsoedin Visser EJ, van Dijken PJ, Kok AJ, Sixma JJ. Bleeding symptoms in carriers of hemophilia A and B. Thromb Haemost 1988; 59: 349–52. 4 Di Michele DM, Gibb C, Lefkowitz JM, Ni Q, Gerber LM, Ganguly A. Severe and moderate haemophilia A and B in US females. Haemophilia 2014; 20: 136–43. 5 Orstavik KH, Scheibel E, Ingerslev J, Schwartz M. Absence of correlation between X chromosome inactivation pattern and plasma concentration of factor VIII and factor IX in carriers of haemophilia A and B. Thromb Haemost 2000; 83: 433–7. 6 Knobe KE, Ljung RC. Haemophilia B carrier detection by factor IX: C analysis; no impact of the type of mutation or severity of disorder. Haemophilia 1999; 5: 238–42. 7 Ay C, Thom K, Abu-Hamdeh F et al. Determinants of factor VIII plasma levels in carriers of haemophilia A and in control women. Haemophilia 2010; 16: 111–7. 8 Armstrong E, Hillarp A. Assay discrepancy in haemophilia. Eur J Haemotol 2014; 93 (suppl 76): 48–50.

Venous thromboembolism in pediatric trauma patients: Ten-year experience and long-term follow-up in a tertiary care center.

Pediatric trauma patients are at high risk for development of venous thromboembolism (VTE). Our objective is to describe incidence, risk factors, and timing of development of VTE, anticoagulation complications, and long‐term VTE outcomes in a critically injured pediatric population.

Validation study of the composite score to identify von Willebrand disease in children

Background:The diagnosis of type 1 von Willebrand disease (VWD) presents a diagnostic challenge in children. In fact, 25% or more of children with VWD may be diagnosed only after they experience postoperative bleeding. We previously described a 4-variable composite score that has 92.5% sensitivity and 95% specificity for diagnosing VWD in children with known VWD when 2 of 4 criteria are positive: (1) Tosetto bleeding score ≥1; (2) family history of VWD; (3) personal history of iron deficiency anemia; and/or (4) positive James early bleeding score. The purpose of this study was to prospectively validate a composite score of ≥2 for identifying children with VWD. Procedure:Children without a previously diagnosed bleeding disorder presenting for hematology evaluation were enrolled. Sensitivity, specificity, positive, and negative predictive value of the composite score was determined. Results:A total of 193 subjects were enrolled from 12 participating centers were included in the analysis. Forty-seven children had type 1 VWD, including 11 with von Willebrand Ristocetin Cofactor (VWF):RCo <30 IU/dL, 14 subjects with a VWF:RCo 30 to 39 IU/dL, and 22 with a VWF:RCo 40 to 49 IU/dL. Including all 4 variables, a composite score of ≥2 had a sensitivity of 63.6% to 76.0%, specificity of 33.5% to 35.1%, negative predictive value of 76.9% to 93.8%, and positive predictive value of 5.5% to 25%. Conclusions:The negative predictive value of the composite score was robust, especially at lower VWF:RCo suggesting that VWD testing could be eliminated in nearly a third of children referred for VWD testing.

Von Willebrand factor for menorrhagia: a survey and literature review.

von Willebrand disease (VWD) is the most common congenital bleeding disorder. In women, menorrhagia is the most common bleeding symptom, and is disabling with iron deficiency anaemia, high health cost and poor quality of life. Current hormonal and non‐hormonal therapies are limited by ineffectiveness and intolerance. Few data exist regarding von Willebrand factor (VWF), typically prescribed when other treatments fail. The lack of effective therapy for menorrhagia remains the greatest unmet healthcare need in women with VWD. Better therapies are needed to treat women with menorrhagia.

Inhibitor development in two cousins receiving full‐length factor VIII (FVIII) and FVIII‐Fc fusion protein

To the Editor, Inhibitor formation is a serious complication of haemophilia treatment, occurring in approximately 28% of those with severe haemophilia A [1]. Characterized as a T-cell-dependent, B-cell-mediated immune response directed against infused factor VIII (FVIII) [2], inhibitors neutralize FVIII activity and disrupt haemostasis. Treatment with bypass agents, for example, activated recombinant FVII (rFVIIa) or activated prothrombin complex concentrate, results in less predictable haemostasis and greater morbidity and mortality than in individuals without inhibitors. Thus, inhibitor prevention is a goal of haemophilia treatment. Although there are no proven strategies to prevent inhibitors, several factors may be associated with inhibitor formation. First, when early FVIII treatment is high-intensity [1], such as at the time of bleeds, surgery or trauma, inhibitor risk is 5-fold higher than when early factor is low-intensity, such as to prevent bleeds (prophylaxis). The ‘danger theory’ suggests that bleeds at the time of first factor exposure activates the immune system, triggering an inhibitor response to FVIII [3], but this remains unproven. Second, the recently FDA approved rFVIII fusion protein, rFVIIIFc (rFVIIIFc), Eloctate [4], contains an Fc sequence which not only increases FVIII half-life by delaying its lysosomal degradation [5], but also promotes antigenspecific tolerance to proteins to which it is fused, in this case rFVIII, by inducing regulatory T cells [6]. In preclinical studies, inhibitor titre and frequency were significantly reduced in Eloctate-treated vs. rFVIIItreated haemophilia A mice [7]. We report the development of a low-titre inhibitor in a child from an inhibitor-prone family with severe haemophilia A treated with rFVIIIFc, Eloctate, as compared to a hightitre inhibitor in his rFVIII-treated maternal cousin. Patient 1 is a child with severe haemophilia A, FVIII < 0.01 IU mL , born in 2010, with a strong family history of haemophilia and inhibitor formation in his maternal grandfather. Next-generation sequencing of his F8 gene identified a pathogenic nonsense variant in exon 14, c.5177G>A, resulting in p.W12726X. At 5 months of age, with no previous bleeds or factor treatment, and to avoid inhibitor formation, he was begun on once weekly rFVIII, Kogenate, 25 IU kg 1 weekly (Fig. 1, Table 1). Although standard prophylaxis is 2–3 times weekly FVIII, he was treated once weekly to avoid port placement for venous access and associated complications. After 15 exposures, an anti-VIII inhibitor was detected at 22.4 Bethesda units (BU), confirmed as high-titre (>5.0 BU), with peak titre 43.2 BU. After confirmation, rFVIII prophylaxis was stopped, and per standard of care [8], when the anti-VIII titre fell to <10.0 BU, a port was placed and immune tolerance induction (ITI), a program of high-dose factor to suppress the inhibitor, was begun with rFVIII, Kogenate, 200 IU kg 1 daily. Bleeds were managed with bypass therapy, rFVIIa 90 mcg kg . His course was complicated by recurrent port infections requiring parenteral antibiotics and hospitalization. By week 83, the antiVIII titre fell to <0.6 BU, after which rFVIII was tapered, and the anti-VIII remained undetectable <0.6 BU, with peak VIII:C = 1.26 IU mL 1 and halflife exceeding 5 h, not quite achieving tolerance (halflife > 6 h) [8]. Standard prophylaxis was begun at rFVIII 25 IU kg 1 every other day, and subsequently switched to rFVIIIFc, Eloctate, 25 IU kg 1 twice weekly, once available, with undetectable anti-VIII, 0.0 BU. Compliance with treatment was excellent with no missed doses. Patient 2, the maternal first cousin of patient 1, was born in 2014 with severe haemophilia A, FVIII <0.01 IU mL , with the same pathogenic nonsense variant in exon 14, c.5177G>A, resulting in p.W12726X. At 8 months of age, with no previous bleeds or factor treatment, prophylaxis was initiated with Eloctate 50 IU kg 1 weekly, as his cousin had developed an inhibitor on rFVIII (Fig. 1, Table 1). While the current standard for Eloctate prophylaxis is twice-weekly dosing in children, adolescents and adults [4], no standard exists at younger age, and as with rFVIII, weekly dosing was chosen to avoid port Correspondence: Margaret V. Ragni, MD, MPH, Professor of Medicine and Clinical Translational Science, Division of Hematology/Oncology, Department of Medicine, University of Pittsburgh Medical Center or Director, Hemophilia Center of Western PA, 3636 Boulevard of the Allies, Pittsburgh, PA 15213-4306. Tel.: 412 209 7288; fax: 412 209 7281; e-mail: ragni@dom.pitt.edu

Three cost-utility analyses of screening for intracranial hemorrhage in neonates with hemophilia.

Background: Intracranial hemorrhage (ICH) in the newborn period is a potential cause of serious morbidity and mortality in individuals with hemophilia. The incidence of ICH is estimated to be 2% to 4%; however, depending on the mode of delivery, it may be considerably higher. Considering the varying sensitivities and costs of various imaging modalities, there remains controversy surrounding universal cranial imaging. Cost-utility analysis is the ideal tool to display the consequences of a decision made. Methods: We constructed a decision tree to evaluate the direct and indirect costs, possible outcomes, and probabilities of ICH in neonates with hemophilia. We created 3 decision analysis models to evaluate the cost-utility of different screening modalities for ICH: ultrasound, computed tomography, and magnetic resonance imaging. Within each model, 3 different strategies were compared: screen all neonates; screen only neonates born by instrumented delivery; and not screen any neonates. A societal perspective was used for all models. The base case models were later reanalyzed in sensitivity analysis to account for uncertainties. Results: Total costs for screening all neonates, screening only neonates born by instrumented delivery, and not screening any neonates were

rFIXFc for Immune Tolerance Induction in a Severe Hemophilia B Patient with an Inhibitor and Prior History of ITI Related Nephrotic Syndrome

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Feasibility of the Von Willebrand disease PREVENT trial

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