Dilemmas on emicizumab in children with haemophilia A: A survey of strategies from PedNet centres.

INTRODUCTION: Haemophilia A care has changed with the introduction of emicizumab. Experience on the youngest children is still scarce and clinical practice varies between haemophilia treatment centres. AIM: We aimed to assess the current clinical practice on emicizumab prophylaxis within PedNet, a collaborative research platform for paediatricians treating children with haemophilia. METHODS: An electronic survey was sent to all PedNet members (n = 32) between October 2022 and February 2023. The survey included questions on the availability of emicizumab, on the practice of initiating prophylaxis in previously untreated or minimally treated patients (PUPs or MTPs) and emicizumab use in patients with or without inhibitors. RESULTS: All but four centres (28/32; 88%) responded. Emicizumab was available in clinical practice in 25/28 centres (89%), and in 3/28 for selected patients only (e.g. with inhibitors). Emicizumab was the preferred choice for prophylaxis in PUPs or MTPs in 20/25 centres; most (85%) started emicizumab prophylaxis before 1 year of age (30% before 6 months of age) and without concomitant FVIII (16/20; 80%). After the loading dose, 13/28 centres administered the recommended dosing, while the others adjusted the interval of injections to give whole vials. In inhibitor patients, the use of emicizumab during ITI was common, with low-dose ITI being the preferred protocol. CONCLUSION: Most centres choose to initiate prophylaxis with emicizumab before 12 months of age and without concomitant FVIII. In inhibitor patients, ITI is mostly given in addition to emicizumab, but there was no common practice on how to proceed after successful ITI.

Guiding future paediatric drug studies based on existing pharmacokinetic and efficacy data: Cardiovascular drugs as a proof of concept.

INTRODUCTION: Off-label drug use in the paediatric population is common, and the lack of high-quality efficacy studies poses patients at risk for failing pharmacotherapy. Next to efficacy studies, pharmacokinetic (PK) studies are increasingly used to inform paediatric dose selection. As resources for paediatric trials are limited, we aimed to summarize existing PK and efficacy studies to identify knowledge gaps in available evidence supporting paediatric dosing recommendations, thereby taking paediatric cardiovascular drugs as proof of concept. METHODS: For each cardiovascular drug, paediatric indication and prespecified age group, together comprising one record, the authorized state was assessed. Next, for off-label records, the highest level of evidence was scored. High-quality efficacy studies were defined as meta-analysis or randomized controlled trials. Other comparative research, noncomparative research or consensus-based expert opinions were considered low quality. The level of evidence for PK studies was scored per drug and per age group, but regardless of indication. RESULTS: A total of 58 drugs included 417 records, of which 279 (67%) were off-label. Of all off-label records, the majority (81%) were not supported by high-quality efficacy studies, but for 140 of these records (62%) high-quality PK studies were available. CONCLUSION: We demonstrated that for the majority of off-label cardiovascular drugs, only low-quality efficacy studies were available. However, high-quality PK studies were frequently available. Combining these PK data with extrapolation of efficacy data from adults may help to close the current information gap and prioritize the drugs for which clinical studies and safety data are urgently needed.

Electronic diaries in the management of haemophilia gene therapy: Perspective of an expert group from the German, Austrian and Swiss Society on Thrombosis and Haemostasis (GTH).

INTRODUCTION: Gene therapy (GT) is becoming a realistic treatment option for patients with haemophilia. Outside clinical trials, the complexity and potential complications of GT will pose unprecedented challenges to haemophilia care centres. AIM: To explore the potential use of electronic tools to improve the delivery of GT under real-world conditions. METHODS: Considering the hub-and-spoke model, the GTH working group on GT considered the entire patient pathway and reached consensus on requirements for an integrative software tool to secure documenting and sharing information between treaters, pharmacies and patients. RESULTS: Six steps of the gene therapy process were identified, each requiring completion of the previous step as a prerequisite for entry. The responsibilities of GT dosing and follow-up treatment centres, read/write access rules, and the minimum data set were outlined. Data contributed by patients through mobile devices was also considered. CONCLUSION: Important information needs to be shared between patients and treatment centres in a real-world GT hub-and-spoke model. Collecting and sharing this information in well-organised electronic applications will not only improve patient care but also enable national and international data collection in clinical registries.

Efficacy and Safety of Non-Vitamin K Antagonist Oral Anticoagulants in Pediatric Venous Thromboembolism Treatment and Thromboprophylaxis: A Systematic Review of the Literature.

Venous thromboembolism (VTE) in children can lead to significant morbidity and mortality. Traditionally, treatment for thrombotic events in pediatric patients has been limited mainly to unfractionated heparin, low-molecular-weight heparin (LMWH), or vitamin K antagonists. Since the first non-vitamin K antagonist oral anticoagulant (NOAC) was approved for adult use, these agents have gained popularity for a variety of indications. This is largely due to their ease of administration, favorable pharmacokinetic and pharmacodynamic profile, decreased food interactions, and decreased need for therapeutic drug monitoring. Treating and preventing VTE with traditional anticoagulants in pediatric patients presents many challenges. This systematic review evaluated the current literature regarding pediatric NOAC trials. Additionally, based on an up-to-date query of clinicaltrials.gov, we detail current ongoing and as-yet unpublished clinical trials, study outcomes, and projected completion dates. Published pediatric NOAC trials have included 1,007 total children to date and have ranged from phase 1 to 4, with "indications" including both thromboembolism prophylaxis and VTE treatment. Three recent phase 3 trials, specifically involving rivaroxaban and dabigatran, have shown the agents to be at least as effective as traditional anticoagulants for acute and/or extended VTE treatment, with low frequency of recurrent thrombosis and clinically significant bleeding rates. Additionally, specially developed and tested pediatric formulations have allowed for accurate and reliable dosing, oral administration, stable pharmacokinetics and pharmacodynamics, and fewer drug or food interactions. Ongoing trials, anticipated for completion in the next few years, will reveal important information with regard to thromboembolism prophylaxis in special pediatric subpopulations and settings.

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

Factor VIII (FVIII) pharmacokinetic (PK) properties show high interpatient variability in hemophilia A patients. Although previous studies have determined that age, body mass index, von Willebrand factor antigen (VWF:Ag) levels, and ABO blood group status can influence FVIII PK, they do not account for all observed variability. In this study, we aim to describe the genetic determinants that modify the FVIII PK profile in a population of 43 pediatric hemophilia A patients. We observed that VWF:Ag and VWF propeptide (VWFpp)/VWF:Ag, but not VWFpp, were associated with FVIII half-life. VWFpp/VWF:Ag negatively correlated with FVIII half-life in patients with non-O blood type, but no correlation was observed for type O patients, suggesting that von Willebrand factor (VWF) half-life, as modified by the ABO blood group, is a strong regulator of FVIII PK. The FVIII-binding activity of VWF positively correlated with FVIII half-life, and the rare or low-frequency nonsynonymous VWF variants p.(Arg826Lys) and p.(Arg852Glu) were identified in patients with reduced VWF:FVIIIB but not VWF:Ag. Common variants at the VWF, CLEC4M, and STAB2 loci, which have been previously associated with plasma levels of VWF and FVIII, were associated with the FVIII PK profile. Together, these studies characterize the mechanistic basis by which VWF clearance and ABO glycosylation modify FVIII PK in a pediatric population. Moreover, this study is the first to identify non-VWF and non-ABO variants that modify FVIII PK in pediatric hemophilia A patients.

Inhibitor incidence in an unselected cohort of previously untreated patients with severe haemophilia B: a PedNet study.

The incidence of FIX inhibitors in severe hemophilia B (SHB) is not well defined. Frequencies of 3-5% have been reported but most studies to date were small, including patients with different severities, and without prospective follow-up for inhibitor incidence. Study objective was to investigate inhibitor incidence in patients with SHB followed up to 500 exposure days (ED), the frequency of allergic reactions, and the relationship with genotypes. Consecutive previously untreated patients (PUPs) with SHB enrolled into the PedNet cohort were included. Detailed data was collected for the first 50 ED, followed by annual collection of inhibitor status and allergic reactions. Presence of inhibitors was defined by at least two consecutive positive samples. Additionally, data on factor IX gene mutation was collected. 154 PUPs with SHB were included; 75% were followed until 75 ED, and 43% until 500 ED. Inhibitors developed in 14 patients (7 high-titre). Median number of ED at inhibitor manifestation was 11 (IQR 6.5-36.5). Cumulative inhibitor incidence was 9.3% (95%CI 4.4-14.1) at 75 ED, and 10.2% (5.1-15.3) at 500 ED. Allergic reactions occurred in 4 (28.6%) inhibitor patients. Missense mutations were most frequent (46.8%) overall but not associated with inhibitors. Nonsense mutations and deletions with large structural changes comprised all mutations among inhibitor patients and were associated with an inhibitor risk of 26.9% and 33.3%, respectively. In an unselected, well-defined cohort of PUPs with SHB, cumulative inhibitor incidence was 10.2% at 500 ED. Nonsense mutations and large deletions were strongly associated with the risk of inhibitor development. The PedNet Registry is registered at clinicaltrials.gov; identifier: NCT02979119.

Lower physical activity and altered body composition in patients with haemophilia compared with healthy controls.

INTRODUCTION: Patients with haemophilia (PWH) have traditionally been discouraged from engaging in sports and strenuous exercise activities, due to the perceived risk of bleeding complications. This puts PWH at an increased risk to become overweight or obese. However, the benefits of many forms of physical activity seem to outweigh their risks, although activities with significant trauma risk should be avoided. AIM: To evaluate physical activity patterns and body composition of adult PWH. METHODS: This cross-sectional study compared data on physical activity from tri-axial accelerometers and body composition of 18 male adult PWH (aged 18-49 years) on prophylactic replacement therapy and without acute joint bleedings to those of 24 healthy age-matched controls, by means of Mann-Whitney-U-Tests. RESULTS: Median moderate-to-vigorous physical activity was significantly (p = .000) lower in PWH (34.6 min/day) than in healthy controls (65.2 min/day). Body mass index was almost similar between PWH and controls (25.1 vs 24.2 kg/m2 , p = .431). Yet, we found a consistent trend towards less desirable outcomes across body composition parameters, such as median body fat rate (23.5 vs 17.0%, p = .055) in PWH, compared with controls. CONCLUSION: Although physical activity has been recommended for PWH since the mid-1970s, the physical activity engagement of adult PWH was still severely limited, possibly due to over-cautiousness but presumably also in consequence of chronic pain. Poor physical activity engagement may well be expected to contribute to the increased body fat and decreased leg muscle mass. Consequently, policies should focus on improving the knowledge and motivation of PWH to engage in health-enhancing physical activity.

Prophylaxis in children with haemophilia in an evolving treatment landscape.

INTRODUCTION: For children with haemophilia, early initiation of prophylaxis is crucial to prevent life-threatening bleeds and maintain joint health throughout life. Options for prophylaxis have recently increased from replacement therapy with standard or extended half-life coagulation factor products to include other haemostasis products, such as the non-replacement therapy emicizumab. AIM: To review key factors that determine the choice of prophylaxis in young children. METHODS: Key clinical questions on the implementation of prophylaxis for haemophilia in children were identified and PubMed was searched for evidence supporting guidance on the implementation of prophylaxis. RESULTS: The results of the literature search and the practical experience of the authors were used to build consensus on when to start prophylaxis, the pros and cons of the products available to guide the choice of product, and practical aspects of starting prophylaxis to guide the choice of regimen. CONCLUSIONS: In this era of increasing therapeutic choices, available information about the range of treatment options must be considered when initiating prophylaxis in young children. Parents or care givers must be sufficiently informed to allow informed shared decision making. Although plentiful data and clinical experience have been gathered on prophylaxis with clotting factor replacement therapy, its use in young children brings practical challenges, such as the need for intravenous administration. In contrast, our relatively brief experience and limited data with subcutaneously administered non-replacement therapy (i.e., emicizumab) in this patient group imply that starting emicizumab prophylaxis in young children requires careful consideration, despite the more convenient route of administration.

The relation of etiology based on the 2017 ILAE classification to the effectiveness of the ketogenic diet in drug-resistant epilepsy in childhood.

OBJECTIVE: To investigate the effectiveness and safety of the ketogenic diet (KD) in drug-resistant epilepsy in childhood in relation to the new 2017 International League Against Epilepsy (ILAE) classification of etiology. METHODS: A consecutive cohort of patients treated with the KD were categorized according to the ILAE classification into known (structural, genetic, metabolic, infectious, and immune-mediated) and unknown etiology. Primary outcome was the frequency of patients achieving seizure freedom with the KD at 3 months, secondary outcomes were seizure reduction >50% at 3 months, and both seizure freedom and seizure reduction >50% at 6, 12 months, and at last follow-up (LFU), and adverse effects. Outcomes were compared between etiology groups. RESULTS: Etiology was known in 70% (129/183). Outcomes did not differ at 3 months (known vs unknown: seizure freedom 28% vs 33%, seizure reduction 62 vs 67%), but seizure freedom was significantly less frequent in known etiology at 6 months (26% vs 43%) and beyond (22% vs 37%). Logistic regression identified duration of epilepsy, number of previous antiseizure medications (ASMs), and age-appropriate psychomotor development as positive determinants of outcome. Among individual etiology groups, the effectiveness of KD was relatively best for genetic (33% at LFU) and poorest for metabolic etiology (8% at LFU). The small number of patients with infectious and immune-mediated etiology requires larger numbers in each etiology group to corroborate our results. No differences in type and frequency of adverse effects (in 71%) between etiology groups were observed, requiring medical intervention in 21%. SIGNIFICANCE: The KD was most effective in genetic and unknown etiology, many unknowns probably represent yet unidentified genetic causes. We recommend consequent diagnostic and genetic work-up to identify etiologies that respond best to the KD. The KD should be offered early to infants with genetic epilepsy before deterioration of epileptic symptoms and of psychomotor development.

3D gait analysis, haemophilia joint health score, leg muscle laterality and biomarkers of joint damage: A cross-sectional comparative assessment of haemophilic arthropathy.

INTRODUCTION: 3D gait analysis has been proposed as a reproducible and valid method to assess abnormal gait patterns and to monitor disease progression in patients with haemophilia (PWH). AIM: This study aimed at comparing Gait Deviation Index (GDI) between adult PWH and healthy controls, and at assessing the agreement between outcome measures of haemophilic arthropathy. METHODS: Male PWH aged 18-49 years (prespecified subgroups: 18-25 vs 26-49 years) on prophylactic replacement therapy, and male healthy age-matched controls passed through a cross-sectional assessment panel. Besides the 3D gait analysis derived GDI, secondary outcomes included kinematic, kinetic and spatio-temporal gait parameters, the Haemophilia Joint Health Score (HJHS), electric impedance derived leg muscle laterality and inflammatory biomarkers. RESULTS: Patients with haemophilia (n = 18) walked slower, in shorter steps and accordingly with less functional range of motion in the hips and ankles, as compared to healthy controls (n = 24). Overall, PWH did not differ significantly in GDI and specific gait parameters. PWH had a higher mean HJHS (18.8 vs 2.6, P = .000) and leg muscle laterality (4.3% vs 1.5%, P = .004). A subgroup analysis revealed progressed gait pathology in PWH aged 26-49 years (not statistically significant). Leg muscle laterality was strongly correlated with HJHS (r = .76, P = .000), whereas GDI just moderately (r = -.39, P = .110). PWH had higher levels of the inflammatory markers CRP and IL-6. CONCLUSION: Progressed gait pathology was found in PWH, mainly those aged 26-49 years. Leg muscle laterality correlated strongly with HJHS and was identified as a promising tool for detecting progression and physiological consequences of haemophilic joint arthropathy.