New insights into the expression and role of platelet FXIII-A

25 p.-6 fig.Background: The A subunit of factor XIII (FXIII-A) functions as an intracellular transglutaminase (TG) in the megakaryocyte/platelet lineage, where it probably participates in the cytoskeletal remodeling associated with cell activation. However, so far, the precise role of cellular FXIII (cFXIII) and the functional consequences of its absence in FXIII-A-deficient patients are unknown. Objectives and methods: In this study, we used platelets from four patients with congenital deficiency of FXIII-A to study the role of cFXIII in platelet functions. Results: We found that FXIII-A represents the only detectable source of TG activity in platelets and that the binding of fibrinogen in response to thrombin receptor agonist peptide (TRAP) stimulation was significantly reduced in platelets from the patients. In agreement with this, in control platelets, monodansyl-cadaverine (MDC), a competitive amino-donor for TGs, inhibited fibrinogen binding induced by TRAP in a dose-dependent manner. Moreover, upon adhesion to fibrinogen, normal platelets incubated with MDC as well as FXIII-A-deficient platelets showed a distinct extension pattern with reduced lamellipodia and increased filopodia formation, suggesting a delay in spreading. Conclusions: These findings provide evidence for the direct involvement of cFXIII-dependent TG activity in the regulation of platelet functionsThis work was supported by grants from the Dirección General de Investigación del Ministerio de Educación y Ciencia (BFU2006-00914) and Fundación Rodríguez Pascual. A. Jayo was recipient of a fellowship from the Ministerio de Educación y Ciencia. I. Conde holds a research contract from the Consejo Superior de Investigaciones Científica

Outcomes in children with hemophilia A with inhibitors: Results from a noninterventional study

Background: Data regarding management of pediatric persons with hemophilia A (PwHA) with factor VIII (FVIII) inhibitors are limited. This prospective noninterventional study (NCT02476942) evaluated annualized bleeding rates (ABRs), safety, and health-related quality of life (HRQoL) in pediatric PwHA with FVIII inhibitors. Procedure: PwHA aged <12 years with current FVIII inhibitors and high-titer inhibitor history were enrolled. Participants remained on usual treatment; no interventions were applied. Outcomes included ABR, safety, and HRQoL. Results: Twenty-four PwHA aged 2-11 years (median 7.5) were enrolled and monitored for 8.7-44.1 weeks (median 23.4). In the episodic (n = 10) and prophylactic (n = 14) groups, respectively, 121 of 185 (65.4%) and 101 of 186 (54.3%) bleeds were treated using activated prothrombin complex concentrate (aPCC) and/or recombinant activated FVII (rFVIIa). ABRs (95% confidence interval) were 19.4 (13.2-28.4) and 18.5 (14.2-24.0) for treated bleeds, and 32.7 (20.5-52.2) and 33.1 (22.4-48.9) for all bleeds, respectively. Most prophylactic group participants (92.9%) were prescribed aPCC; 50% adhered to their prescribed treatment regimen. Adherence to prophylactic rFVIIa was not assessed. Serious adverse events included hemarthrosis (12.5%) and mouth hemorrhage (12.5%); the most common nonserious adverse event was viral upper respiratory tract infection (12.5%). HRQoL showed functional impairment at baseline; scores remained stable throughout, with little intergroup variation. Conclusions: ABRs remained high in pediatric PwHA with inhibitors receiving standard treatment. This study demonstrates the need for more effective treatments, with reduced treatment burden, to prevent bleeds, increase prophylaxis adherence, and improve patient outcomes.Was funded by F. Hoffmann-La Roche Ltd

Emicizumab prophylaxis in infants with hemophilia A (HAVEN 7): primary analysis of a phase 3b, open-label trial

Subcutaneous emicizumab enables prophylaxis for people with hemophilia A (HA) from birth, potentially reducing risk of bleeding and intracranial hemorrhage (ICH). HAVEN 7 (NCT04431726) is the first clinical trial of emicizumab dedicated to infants, designed to investigate the efficacy, safety, pharmacokinetics, and pharmacodynamics of emicizumab in those aged ≤12 months with severe HA without factor VIII (FVIII) inhibitors. Participants in this phase 3b trial received emicizumab 3 mg/kg maintenance dose every 2 weeks for 52 weeks and are continuing emicizumab during the 7-year long-term follow-up. Efficacy end points included annualized bleed rate (ABR): treated, all, treated spontaneous, and treated joint bleeds. Safety end points included adverse events (AEs), thromboembolic events (TEs), thrombotic microangiopathies (TMAs), and immunogenicity (anti-emicizumab antibodies [ADAs] and FVIII inhibitors). At primary analysis, 55 male participants had received emicizumab (median treatment duration: 100.3; range, 52-118 weeks). Median age at informed consent was 4.0 months (range, 9 days to 11 months 30 days). Model-based ABR for treated bleeds was 0.4 (95% confidence interval, 0.30–0.63), with 54.5% of participants (n = 30) having zero treated bleeds. No ICH occurred. All 42 treated bleeds in 25 participants (45.5%) were traumatic. Nine participants (16.4%) had ≥1 emicizumab-related AE (all grade 1 injection-site reactions). No AE led to treatment changes. No deaths, TEs, or TMAs occurred. No participant tested positive for ADAs. Two participants were confirmed positive for FVIII inhibitors. This primary analysis of HAVEN 7 indicates that emicizumab is efficacious and well tolerated in infants with severe HA without FVIII inhibitors

Type II Glanzmann thrombasthenia in a compound heterozygote for the [alpha]IIb gene. A novel missense mutation in exon 27 that results in enhanced skipping of exon 28

8 páginas, 5 figuras -- PAGS nros. 1352-1359Background and Objectives. Glanzmann thrombasthenia is an autosomal recessive bleeding disorder characterized by a life-long hemorrhagic tendency and absent or severely reduced platelet aggregation in response to agonists, caused by quantitative or qualitative abnormalities in the platelet fibrinogen receptor, integrin αIIbβ3. The aim of this study was to identify the molecular genetic defect and determine its functional consequences in a patient with type II Glanzmann thrombasthenia. Design and Methods. The expression of platelet αIIbβ3 was determined by flow cytometry and western blotting. Mutations were identified by sequencing both cDNA and genomic DNA. Functional characterization was assessed by exontrap and transient transfection analysis. Results. Flow cytometry and western blot analysis revealed markedly reduced levels of platelet αIIbβ3, which may account for the residual fibrinogen binding detected upon platelet activation. Sequencing of genomic DNA revealed the presence of two mutations in the αIIb gene: a C1750T transition in the last codon of exon 17 changing Arg553 to STOP, and a C2829T transition in exon 27 that changes Pro912 to Leu. Sequence analysis of reversely transcribed αIIb mRNA did not detect cDNA from the C1750T mutant allele, and revealed a significant increase of the physiological splicing out of exon 28 in the cDNA carrying the C2829T mutation. Transient expression of [912Leu]αIIb in CHO-β3 cells showed a marked reduction in the rate of surface expression of αIIbβ3. Interpretation and Conclusions. The results suggest that the thrombasthenic phenotype is the result of reduced availability of αIIb-mRNA, enhanced expression of exon 28- deleted transcripts, and defective processing of [912Leu]αIIbFunding: this work was supported by a grant from the Dirección General de Investigación of the Ministerio de Educación y Ciencia (BMC2003-01409). A. Jayo is recipient of a fellowship from the Ministerio de Educación y CienciaPeer reviewe

Optimizing joint function : new knowledge and novel tools and treatments

Progressive joint destruction resulting from intra-articular bleeding is the major morbidity affecting patients with haemophilia (PWH), particularly those with inhibitors. Advances in understanding the detrimental processes set in motion by the exposure of joints to bleeding have shaped current management methods. However, to achieve optimal joint health in PWH, in addition to achieving haemostasis at the bleeding vessel, it may be appropriate to explore experimentally other conceptual frameworks. These include the possibilities that markers might help to identify individuals at the risk of more rapid joint deterioration, that clotting factors may have additional local action within tissues, and that outcomes might be improved with therapies that directly address wound healing and inflammation. Joint assessment tools are important. Conventional radiography is frequently used, but given the possibility of subclinical joint bleeds, accurate non-invasive imaging tools are required to detect soft tissue and cartilage changes. Magnetic resonance imaging and ultrasonography can prove valuable here. New imaging techniques should help to increase understanding of the biological basis of early events in haemophilic arthropathy. The optimal way to measure outcomes in haemophilia is to use several methods - in addition to imaging methods, a 360° approach will use physical, functional and quality-of-life instruments. In PWH, inhibitor development complicates treatment of joint bleeds and increases the risk of developing arthropathy. A new therapeutic approach for joint bleeds in inhibitor patients divides treatment into two phases: bleed control, with bypassing agent therapy until bleeding has definitely ceased, followed by regular dosing to prevent rebleeds until synovial recovery is complete

Considerations for shared decision management in previously untreated patients with hemophilia A or B

Recent advances in therapeutics are now providing a wide range of options for adults and children living with hemophilia. Although therapeutic choices are also increasing for the youngest individuals with severe disease, challenges remain about early management decisions, as supporting data are currently limited. Parents and healthcare professionals are tasked with helping children achieve an inclusive quality of life and maintain good joint health into adulthood. Primary prophylaxis is the gold standard to optimize outcomes and is recommended to start before 2 years of age. A range of topics need to be discussed with parents to aid their understanding of the decisions they can make and how these will affect the management of their child/children. For those with a family history of hemophilia, prenatal considerations include the possibility of genetic counseling, prenatal investigations, and planning for delivery, together with monitoring of the mother and neonate, as well as diagnosis of the newborn and treatment of any birth-associated bleeding. Subsequent considerations, which are also applicable to families where infant bleeding has resulted in a new diagnosis of sporadic hemophilia, involve explaining bleed recognition and treatment options, practical aspects of initiating/continuing prophylaxis, dealing with bleeds, and ongoing aspects of treatment, including possible inhibitor development. Over time, optimizing treatment efficacy, in which individualizing therapy around activities can play a role, and long-term considerations, including retaining joint health and tolerance maintenance, become increasingly important. The evolving treatment landscape is creating a need for continually updated guidance. Multidisciplinary teams and peers from patient organizations can help provide relevant information. Easily accessible, multidisciplinary comprehensive care remains a foundation to care. Equipping parents early with the knowledge to facilitate truly informed decision-making will help achieve the best possible longer-term health equity and quality of life for the child and family living with hemophilia. Plain language summary Points to be taken into account to help families make decisions to best care for children born with hemophilia Medical advances are providing a range of treatment options for adults and children with hemophilia. There is, however, relatively limited information about managing newborns with the condition. Doctors and nurses can help parents to understand the choices for infants born with hemophilia. We describe the various points doctors and nurses should ideally discuss with families to enable informed decision-making. We focus on infants who require early treatment to prevent spontaneous or traumatic bleeding (prophylaxis), which is recommended to start before 2 years of age. Families with a history of hemophilia may benefit from discussions before pregnancy, including how an affected child would be treated to protect against bleeds. When mothers are pregnant, doctors can explain investigations that can provide information about their unborn child, plan for the birth, and monitor mother and baby to minimize bleed risks at delivery. Testing will confirm whether the baby is affected by hemophilia. Not all infants with hemophilia will be born to families with a history of the condition. Identification of hemophilia for the first time in a family (which is ‘sporadic hemophilia’) occurs in previously undiagnosed infants who have bleeds requiring medical advice and possibly hospital treatment. Before any mothers and babies with hemophilia are discharged from hospital, doctors and nurses will explain to parents how to recognize bleeding and available treatment options can be discussed. Over time, ongoing discussions will help parents to make informed treatment decisions: • When and how to start, then continue, prophylaxis. • How to deal with bleeds (reinforcing previous discussions about bleed recognition and treatment) and other ongoing aspects of treatment.  ○ For instance, children may develop neutralizing antibodies (inhibitors) to treatment they are receiving, requiring a change to the planned approach. • Ensuring treatment remains effective as their child grows, considering the varied needs and activities of their child

Immune tolerance induction in the era of emicizumab – still the first choice for patients with haemophilia A and inhibitors?

Introduction The development of inhibitory antibodies is a severe complication of clotting factor replacement therapy in patients with severe haemophilia A (HA). Current World Federation of Hemophilia (WFH) guidelines for haemophilia care indicate that eradication of inhibitors is best achieved through immune tolerance induction (ITI) therapy. Aim The European Collaborative Haemophilia Network conducted a survey to determine whether ITI is still used in the routine management of patients with HA, and whether the availability of emicizumab prophylaxis has influenced treatment decisions. Methods The survey was conducted in late 2020/early 2021 in 18 centres representing 17 countries in the Europe/Middle East region treating a total of 4955 patients, and included sections specific to patient and centre demographics, treatment protocols (both ITI and prophylactic), inhibitor development and initiation of ITI, treatment success, and the incidence of adverse events. Results While our results indicate that ITI can still be considered a mainstay of treatment for patients with HA with inhibitors, less than daily dosing of ITI in combination with emicizumab prophylaxis is becoming commonplace across the spectrum of disease severity, with initiation being guided by bleeding patterns. The most frequently cited reasons for not initiating emicizumab prophylaxis were availability or reimbursement issues. Conclusion ITI remains a mainstay for haemophilia treatment of patients with HA with inhibitors, but emicizumab has become a preferred first-line approach to protect against bleeds and represents an alternative to burdensome ITI in certain patient groups

Factor VIII activity and bleeding risk during prophylaxis for severe hemophilia A : a population pharmacokinetic model

Copyright © 2020, Ferrata Storti Foundation.During factor VIII prophylaxis for severe hemophilia A, bleeding risk increases with time when factor VIII activity is below 1%. Maintaining trough activity above 1% does not protect all patients from bleeding. The relationship between factor VIII activity during prophylaxis and bleeding risk has not been thoroughly studied. We investigated factor VIII activity and annualized bleeding rate for spontaneous bleeds during prophylaxis. A population pharmacokinetic model derived from three clinical trials was combined with dosing data and bleed information from patient diaries. Each patients' time on prophylaxis was divided into five categories of predicted activity (0-1%, >1-5%, >5-15%, >15-50%, and >50%). Exposure time, mean factor VIII activity, and bleed number (from patient diaries) were calculated for each activity category, and annualized bleeding rates estimated using negative binomial regression and a parametric model. Relationships between these bleeding rates and factor VIII activity were evaluated by trial phase (pivotal vs. extension) and age (adults/adolescents [≥12 years] vs. children [0-1% for 85.64% of the time. Annualized bleeding rate decreased as factor VIII activity increased in each trial phase and age group. However, for a given activity level, bleeding rate differed substantially by trial phase, and age. This suggests that bleeding risk can change over time and is influenced by factors independent of factor VIII pharmacokinetics and trough levels. Target trough and prophylactic regimen should consider patient age, joint disease activity, and other bleeding risk determinants.publishersversionPeer reviewe