Degradation of two novel congenital TTP ADAMTS13 mutants by the cell proteasome prevents ADAMTS13 secretion

INTRODUCTION: Over 150 mutations have been identified in the ADAMTS13 gene in patients with congenital thrombotic thrombocytopenic purpura (TTP). The majority of these (86%), lead to reduced (<50%) secretion of mutant recombinant ADAMTS13. The mechanism by which this occurs has not been investigated in vitro. Two novel ADAMTS13 mutations (p.I143T and p.Y570C) identified in two congenital adolescence onset TTP patients were studied, to investigate their effects on ADAMTS13 secretion and subcellular localisation. MATERIALS AND METHODS: HEK293T cells were transiently transfected with wild type or mutant ADAMTS13 cDNA. Immunofluorescence and confocal microscopy were used to study localisation within the endoplasmic reticulum (ER) and Golgi. The cell proteasome and lysosomes were inhibited in cells stably expressing ADAMTS13 to investigate degradation of ADAMTS13 by either organelle. RESULTS: Both mutations severely impaired secretion and both mutants localised within the ER and Golgi. Proteasome inhibition led to the intracellular accumulation of both mutants, suggesting proteasome degradation. Lysosome inhibition on the other hand did not lead to increased intracellular accumulation of the mutants. CONCLUSIONS: Proteasome degradation of these ADAMTS13 mutants contributed to their reduced secretion

Product type and other environmental risk factors for inhibitor development in severe hemophilia A

The development of FVIII inhibitory antibodies is currently the most challenging complication of treatment, affecting similar to 30% of severe hemophilia A patients. These inhibitors inactivate FVIII, rendering the treatment ineffective, causing disability and increasing morbidity and mortality. Inhibitor development results from a complex multicausal immune response involving both genetic and environmental risk factors. One of the most important modifiable risk factors is the source of FVIII products, eg, plasma-derived or recombinant FVIII. Other environmental risk factors, such as age at first treatment, regimen, and intensity of treatment, could contribute to inhibitor development. Severe bleeds, surgery, concomitant infections, or vaccinations may all be events initiating danger signaling resulting in an immune reaction towards administered FVIII. All in all, the etiology of inhibitor development still remains unclear. The risk factors have been stratified into genetic and environmental, but there are no definitive data to determine the impact of each of them

Factor V deficiency

Congenital factor V (FV) deficiency is a bleeding disorder associated with mild to severe hemorrhagic symptoms and a prevalence in the general population of 1 in 1,000,000 in the homozygous form. Patients with FV deficiency and clinically significant manifestations (mainly involving mucosal tracts) show very low or unmeasurable plasma FV levels and are usually homozygous or compound heterozygous for mutations located in the FV gene ( F5). Heterozygous carriers have approximately half-normal levels of FV and are usually asymptomatic. Replacement therapy for FV-deficient patients can only rely on administration of fresh-frozen plasma because specific FV concentrates are unavailable and FV is not present in cryoprecipitate or prothrombin complex concentrates. A total of 56 mutations have been published to date as being responsible for severe or moderately severe FV deficiency; more than two thirds of these are null mutations (mainly decreasing FV expression), with the remaining being missense mutations (usually impairing FV secretion). This article will provide a concise description of the FV protein and gene and will review the molecular, clinical, and therapeutic aspects of FV deficiency

Efficacy, safety and pharmacokinetics of a new high-purity factor X concentrate in subjects with hereditary factor X deficiency.

IntroductionHereditary factor X (FX) deficiency is a rare bleeding disorder affecting 1:500 000 to 1:1 000 000 of individuals. Until recently, no specific replacement factor concentrate was available.AimThe aim of this study was to assess safety and efficacy of a new, high‐purity plasma‐derived FX concentrate (pdFX) in subjects with hereditary FX deficiency.MethodsSubjects aged ≥12 years with moderate or severe FX deficiency (plasma FX activity <5 IU dL−1) received 25 IU kg−1 pdFX as on‐demand treatment or short‐term prophylaxis for 6 months to 2 years. Subjects assessed pdFX efficacy for each bleed; at end‐of‐study, investigators assessed overall pdFX efficacy. Blood samples for pharmacokinetic analysis were obtained at baseline and ≥6 months. Safety was assessed by adverse events (AEs), inhibitor development and changes in laboratory parameters.ResultsSixteen enrolled subjects (six aged 12–17 years; 10 aged 18–58 years) received a total of 468 pdFX infusions. In the 187 analysed bleeds, pdFX efficacy was categorized as excellent, good, poor or unassessable in 90.9%, 7.5%, 1.1% and 0.5% of bleeds respectively; 83% of bleeds were treated with one infusion. For pdFX, mean (median; interquartile range) incremental recovery and half‐life were 2.00 (2.12; 1.79–2.37) IU dL−1 per IU kg−1 and 29.4 (28.6; 25.8–33.1) h respectively. No serious AEs possibly related to pdFX or evidence of FX inhibitors were observed, and no hypersensitivity reactions or clinically significant trends were detected in laboratory parameters.ConclusionThese results demonstrate that a dose of 25 IU kg−1 pdFX is safe and efficacious for on‐demand treatment and short‐term prophylaxis in subjects with moderate or severe hereditary FX deficiency

Burden of mild haemophilia A: Systematic literature review

Introduction Although the clinical manifestations of severe haemophilia A (HA) are well studied, the challenges, if any, of living with mild HA are not clearly delineated to date. Aim To assess available evidence of clinical risks and societal/economic impacts of disease in adult patients with mild HA using a systematic literature review. Methods Prespecified study selection criteria were applied in a comprehensive literature search. Included studies varied in design and reported outcomes of interest for adults (&gt;= 13 years of age) with mild HA. Results Seventeen studies with a total of 3213 patients met eligibility criteria (published or presented in English, 1966-2017). Most studies were observational, and the outcomes reported were too sparse and dissimilar to support a formal meta-analysis. Mean annual bleeding rates ranged from 0.44 to 4.5 episodes per patient per year. Quality of life (QoL; SF-36 General Health) was impacted compared to healthy controls. Health care costs and productivity were seldom assessed and no robust comparisons to healthy controls were available. Conclusion Quantifying outcomes for adult patients with mild HA remains challenging, with estimates of key QoL and cost data often based on small data sets and without comparison to population norms. Therefore, the clinical impact of mild haemophilia may be under-represented and unmet needs may remain unaddressed. As paradigm-changing therapies for HA emerge, stronger knowledge of mild HA can guide the development of care options that minimize burden and enhance the QoL for this segment of the haemophilia community, and for the haemophilia community in totality

Long-term neuropsychological sequelae, emotional wellbeing and quality of life in patients with acquired thrombotic thrombocytopenic purpura

Neurological symptoms related to microthrombosis are the hallmark of acute manifestations of acquired thrombotic thrombocytopenic purpura. Despite the achievement of hematological remission, patients may report persisting neurological impairment that affects their quality of life. To assess the long-term neuropsychological consequences of acute thrombotic thrombocytopenic purpura, we recruited 35 acquired thrombotic thrombocytopenic purpura patients (77% females, median age at onset 41 years, interquartile range 35-48) regularly followed at our out-patient clinic of thrombotic microangiopathies in Milan (Italy) from December 2015 to October 2016. Patients underwent a psychological evaluation of memory and attentional functions, emotional wellbeing and health-related quality of life at least 3 months after their last acute thrombotic thrombocytopenic purpura event (median 36 months, interquartile range 17-54). During the psychological consultation, 17 patients (49%) referred persisting subjective neurological impairment in the frame of a remission phase, with at least one symptom as disorientation, loss of concentration, dizziness, lack of balance, headache and diplopia. Neuropsychological assessment revealed lower scores than the Italian general population pertaining to direct, indirect and deferred memory. A higher degree of impairment of memory domains was found in patients with neurological involvement at the time of presentation of the first acute thrombotic thrombocytopenic purpura episode. Anxiety and depression were detected in 7 (20%) and 15 (43%) patients, respectively. Health-related quality of life was lower than the Italian general population, with mental domains more impacted than physical domains (mean difference 58.43, 95% confidence interval [-71.49, -45.37]). Our study demonstrates compromised memory and attention functions, persisting anxiety/depression symptoms and a generally reduced quality of life in patients surviving from acute acquired thrombotic thrombocytopenic purpura. New clinical strategies should be considered to improve these symptoms