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In the original publication [...].
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Background: Hemophilia B is a coagulation disorder that puts patients at an increased risk of bleeding. Factor (F) IX replacement therapy is traditionally used in such cases to maintain hemostasis. Nonacog beta pegol (N9-GP; Refixia) is a glycoPEGylated, extended half-life, recombinant FIX product that has demonstrated safety and efficacy when used to manage persons with hemophilia B. Key clinical question: Given the limited real-world evidence, we aimed to explore the role of N9-GP in maintaining hemostasis in persons with hemophilia B undergoing surgery. Clinical approach: In this case series, we report real-world clinical experience with N9-GP to maintain hemostasis in persons with hemophilia B undergoing major and minor surgeries. Conclusion: The majority of cases presented in this case series had an excellent or very good hemostatic response, with no reported surgical complications related to the use of N9-GP.
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Sickle cell disease (SCD) is an inherited monogenic disorder with high prevalence throughout sub-Saharan Africa, the Mediterranean basin, the Middle East, and India. Sources of SCD epidemiology remain scarce and fragmented. A systematic literature review (SLR) to identify peer-reviewed studies on SCD epidemiology was performed, with a search of bibliographic databases and key conference proceedings from 1 January 2010 to 25 March 2022 (congress abstracts after 2018). The SLR followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Meta-analyses, using a binomial normal random-effects model, were performed to estimate global and regional prevalence and birth prevalence. Of 1770 journal articles and 468 abstracts screened, 115 publications met the inclusion criteria. Prevalence was highest in Africa (~800/100,000), followed by the Middle East (~200/100,000) and India (~100/100,000), in contrast to ~30/100,000 in Europe. Birth prevalence was highest in Africa (~1000/100,000) and lowest in North America (~50/100,000) and Europe (~30/100,000). This SLR confirmed that sub-Saharan and North-East Africa, India, the Middle East, and the Caribbean islands are global SCD hotspots. Publications including mortality data were sparse, and no conclusions could be drawn about mortality. The identified data were limited due to gaps in the published literature for large parts of the world population; the inconsistent reporting of SCD genotypes, diagnostic criteria, and settings; and a sparsity of peer-reviewed publications from countries with assumed high prevalence. This SLR demonstrated a lack of systematic knowledge and a need to provide uniform data collection on SCD prevalence and mortality.
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AIM: Haemophilic pseudotumours are complications in patients with haemophilia A or B and result from locally repetitive bleeding, mainly in the musculoskeletal system. Abdominal haemophilic pseudotumours are exceptionally rare but may cause severe complications. This systematic review aimed to evaluate therapy strategies for symptomatic abdominal haemophilic pseudotumours. METHODS: We systematically searched three databases (Medline [PubMed], Web of Science and EMBASE) for publications published between 1995 and 2023. Two reviewers independently selected the studies, extracted data and performed a quality assessment using the JBI critical appraisal checklist. RESULTS: From a total of 1199 articles, 39 articles describing 41 cases were included for final analysis. Conservative or interventional treatment was performed in 12 cases. In eight cases, a step-up to surgical therapy after interventional treatment was indicated. Primary surgical therapy was performed in 21 cases. Failure to cure was documented in 50% (n = 6) of patients treated in the first group, with a mortality rate of 16.6% (n = 2). Interventional therapy with a step-up to surgery showed no morbidity or mortality. Primary surgical resection documented favourable results in 66.6% (n = 14), with failure to cure in 9.5% (n = 2) and a mortality rate of 14.3% (n = 3). CONCLUSION: Primary surgical resection can be a first-line therapy for symptomatic, abdominal haemophilic pseudotumours, whereas preoperative embolisation could be used as a bridging therapy before surgery, especially in emergency settings. Diagnostic biopsy and percutaneous drainage should be avoided to prevent complications.
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Hemofilia A , Medicina , Humanos , Hemofilia A/complicações , Hemofilia A/terapia , Abdome , Biópsia , Terapia ComportamentalRESUMO
BACKGROUND: Both diagnosis and treatment of hemoglobinopathies have been associated with an increased risk of fertility impairment. German guidelines recommend annual monitoring of fertility parameters to enable early detection of fertility impairment and/or to offer fertility preservation (FP) when indicated. We explored the general desire for parenthood, the frequency of recalling fertility counseling and testing, and the utilization of FP in adolescents and adults with hemoglobinopathies. PROCEDURE: In a cross-sectional study, patients aged 12-50 years, treated in Germany, Austria, or Switzerland, were surveyed on fertility-related aspects. Medical data, including fertility testing results, were collected from patient records. RESULTS: Overall, 116/121 eligible patients, diagnosed with sickle cell disease (70.7%), thalassemia (27.6%), or other hemoglobinopathy (1.7%), participated in our study (57.8% female, median age 17.0 years, range 12-50 years). All participants required treatment of the underlying hemoglobinopathy: 68.1% received hydroxyurea, 25.9% required regular blood transfusions, and 6.0% underwent hematopoietic stem cell transplantation (HSCT). Most patients (82/108, 75.9%) stated a considerable to strong desire for (future) parenthood, independent of sex, education, diagnosis, or subjective health status. Fertility counseling was only recalled by 32/111 patients (28.8%) and least frequently by younger patients (12-16 years) or those treated with regular blood transfusions or hydroxyurea. While fertility testing was documented for 59.5% (69/116) in medical records, only 11.6% (13/112) recalled previous assessments. FP was only used by 5.4% (6/111) of patients. CONCLUSION: Most patients with hemoglobinopathies wish to have biological children, yet only few recalled fertility counseling and testing. Adequate patient counseling should be offered to all patients at risk for infertility.
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Anemia Falciforme , Preservação da Fertilidade , Hemoglobinopatias , Infertilidade , Criança , Humanos , Adulto , Feminino , Adolescente , Adulto Jovem , Pessoa de Meia-Idade , Masculino , Hidroxiureia , Estudos Transversais , Preservação da Fertilidade/métodos , AconselhamentoRESUMO
A phase 1b/2, three-month study of marstacimab, a human monoclonal antibody targeting tissue factor pathway inhibitor (TFPI), was conducted in participants with haemophilia A or B, with or without inhibitors. Participants assigned to four cohorts received escalating weekly doses based on inhibitor status (without inhibitors: 300 mg, a single 300-mg loading dose with subsequent 150-mg doses, or 450 mg; with inhibitors: 300 mg). Safety outcomes were treatment-emergent adverse events (TEAEs), injection site reactions, clinical and laboratory parameter changes. Efficacy was assessed by annualised bleeding rates (ABRs). Pharmacokinetics and pharmacodynamics (PD) were also evaluated. Among 26 treated participants [haemophilia A without inhibitor, n = 16 (61.5%); haemophilia A with inhibitor, n = 7 (26.9%); haemophilia B, n = 3 (11.5%)], 24 completed the study. Overall, 80.8% experienced TEAEs. ABR during treatment was significantly reduced versus an external on-demand control group (p < 0.0001) and versus pretreatment ABR (p < 0.0001), with significant reductions observed across all dose cohorts. Marstacimab exposure generally increased in a dose-related manner, with steady-state concentration reached by day 57. Changes in pharmacodynamic biomarkers occurred across all dose cohorts. Marstacimab was safe and well tolerated. Clinically meaningful reductions in ABR and treatment-related changes for all PD biomarkers indicated effective targeting of TFPI. (Clinicaltrials.gov identifier, NCT02974855).
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Hemofilia A , Transtornos dos Cromossomos Sexuais , Humanos , Hemofilia A/tratamento farmacológico , Hemofilia A/induzido quimicamente , Anticorpos Monoclonais Humanizados/efeitos adversos , LipoproteínasRESUMO
OBJECTIVE: Prophylaxis treatment is the current standard of care for patients with severe hemophilia. Factor concentrates with improved pharmacokinetics have offered more options for individualizing treatment. The treatment focus may be on increased protection, aiming for higher trough factor levels or longer dosing intervals to reduce the burden of hemophilia. Both aspects can have long-term effects on joint health. Products, such as rVIIISingleChain and rIX-FP have been developed to reduce the treatment burden for patients with hemophilia and optimize prophylactic efficacy. The objective of this report is to provide a summary of the clinical experience of different Hemophilia Treatment Centers in managing the switch to rVIII-SingleChain or rIX-FP in patients with hemophilia. METHODS: This report summarizes a selection of patient cases presented at the 3rd Alliance for Coagulation Academy Meeting in October 2020. The cases from the participating centers provide examples of the clinical experience in managing patients' switch to rVIII-SingleChain and rIXFP, including which types of patients are suitable for switching, and practical steps in managing a switch. RESULTS: It is important to take into consideration the physical and social fulfillment of the patient when deciding to switch to rVIII-SingleChain or rIX-FP. The physician plays an important role in the motivation of patients as they understand not only the patient's needs but the potential benefits of the new treatment. CONCLUSION: The selected patient cases reported here demonstrate that patients may wish to switch factor products for a variety of reasons; therefore, it is critical to understand why patients switch and what they expect from switching.
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Hemofilia A , Humanos , Hemofilia A/tratamento farmacológico , Proteínas Recombinantes de Fusão/uso terapêuticoRESUMO
Immune thrombotic thrombocytopenic purpura (iTTP) is a life-threatening thrombotic microangiopathy. It is caused by a severe ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motifs, 13) deficiency due to circulating autoantibodies, and is associated with significant morbidity and mortality. Current treatment options include plasma exchange, immunosuppression, and caplacizumab. When remission is achieved, the risk of relapse is high, especially in patients with persistent ADAMTS13 deficiency. We report the eradication of persistent ADAMTS13 inhibitory autoantibodies and restoration of normal ADAMTS13 activity using the anti-CD38 antibody daratumumab in two patients with iTTP. One patient had a frequently relapsing course, and the other a treatment-refractory first episode. There were no relevant adverse drug reactions.
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Púrpura Trombocitopênica Idiopática , Púrpura Trombocitopênica Trombótica , Anticorpos Monoclonais/efeitos adversos , Autoanticorpos , Humanos , Púrpura Trombocitopênica Idiopática/terapia , Púrpura Trombocitopênica Trombótica/tratamento farmacológico , RecidivaRESUMO
The ability of red blood cells (RBCs) to transport gases, their lifespan as well as their rheological properties invariably depend on the deformability, hydration, and membrane stability of these cells, which can be measured by Laser optical rotational red cell analyser (Lorrca® Maxsis, RR Mechatronics). The osmoscan mode of Lorrca is currently used in diagnosis of rare anemias in clinical laboratories. However, a broad range of normal values for healthy subjects reduces the sensitivity of this method for diagnosis of mild disease phenotype. In this pilot study, we explored the impact of age and gender of 45 healthy donors, as well as RBC age on the Lorrca indices. Whereas gender did not affect the Lorrca indices in our study, the age donors had a profound effect on the O_hyper parameter. To study the impact of RBC age on the osmoscan parameters, we have isolated low (L)-, medium (M)-, or high (H)- density fractions enriched with young, mature, and senescent RBCs, respectively, and evaluated the influence of RBC age-related properties, such as density, morphology, and redox state, on the osmoscan indices. As before, O_hyper was the most sensitive parameter, dropping markedly with an increase in RBC density and age. Senescence was associated with a decrease in deformability (EI_max) and tolerability to low and high osmolatites (Area). L-fraction was enriched with reticulocytes and cells with high projected area and EMA staining, but also contained a small number of cells small in projected area and most likely, terminally senescent. L-fraction was on average slightly less deformable than mature cells. The cells from the L-fraction produced more oxidants and NO than all other fractions. However, RBCs from the L-fraction contained maximal levels of reduced thiols compared to other fractions. Our study suggests that reference values for O_hyper should be age-stratified, and, most probably, corrected for the average RBC age. Further multi-center study is required to validate these suggestions before implementing them into clinical practice.
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INTRODUCTION: Emicizumab (Hemlibra®, Hoffmann-La Roche, Switzerland) is now available for haemophilia A patients with or without factor VIII inhibitors. Management of bleeding events and replacement therapy for invasive procedures have to be adapted. OBJECTIVE: To provide a practical guidance for the management of breakthrough bleeding events and elective or urgent surgery in adult and paediatric patients with haemophilia A without inhibitors treated with emicizumab. METHODS: Based on the available literature and the experiences collected from adult and paediatric patients treated in Switzerland, the Working Party on Haemostasis of the Swiss Society of Haematology and the Swiss Haemophilia Network worked together to reach a consensus on the management of bleeding events and invasive procedures. RESULTS AND CONCLUSION: Minor bleeding events and invasive procedures associated with low bleeding risk can be treated without factor replacement therapy in most cases, whereas major bleeding events and high-risk surgery require additional factor VIII replacement at usual doses, at least for the first days. Emicizumab treatment should be continued throughout the procedure and during the postoperative period. Elective major surgery should be planned according to emicizumab dosing for patients with a once-a-month posology. Of note, so far only few data are available on the management of major bleeds and surgery in patients with haemophilia A treated with emicizumab and this practical guidance will have to be regularly updated with growing experience.  .
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Anticorpos Biespecíficos , Hemofilia A , Adulto , Anticorpos Monoclonais Humanizados/uso terapêutico , Criança , Hemofilia A/tratamento farmacológico , Hemorragia/induzido quimicamente , HumanosAssuntos
Anticoagulantes/administração & dosagem , Técnicas de Laboratório Clínico , Infecções por Coronavirus , Heparina de Baixo Peso Molecular/administração & dosagem , Pacientes Internados , Guias de Prática Clínica como Assunto , Tromboembolia Venosa/prevenção & controle , COVID-19 , Técnicas de Laboratório Clínico/normas , Consenso , Coronavirus , Hemostasia , Humanos , Pandemias , Pneumonia Viral , Sociedades Médicas , SuíçaRESUMO
Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse drug effect that occurs in 0.1–5% of heparin treated patients. Management of acute HIT currently involves (1) cessation of heparin exposure, and (2) inhibition of coagulation with an anticoagulant other than heparin. Several anticoagulants can be considered for the treatment of HIT. Anticoagulant monitoring, management of drug-induced adverse events including bleeding, and therapeutic dosing schedules in selected clinical settings represent challenges to the clinician treating HIT patients. Moreover, the fact that not all registered anticoagulants are approved for HIT in Switzerland further complicates the management of HIT. The present recommendations on the anticoagulant treatment of HIT in Switzerland have been elaborated by a panel of Swiss experts belonging to the Working Party Hemostasis (WPH) of the Swiss Society of Hematology (SGH-SSH). They are intended to support clinicians in their decision making when treating HIT patients.
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Anticoagulantes , Trombocitopenia , Anticoagulantes/efeitos adversos , Hemorragia , Heparina/efeitos adversos , Humanos , Suíça , Trombocitopenia/induzido quimicamente , Trombocitopenia/tratamento farmacológicoRESUMO
WHAT IS KNOWN ON THE SUBJECT? Red blood cell transfusions are frequently used in the care of newborns, particularly premature infants. Some countries have guidelines regarding preparation, indication and administration of red blood cells in newborns. There are no such guidelines in Switzerland. WHAT DOES THE CURRENT STUDY ADD? This study analysed the results of two national surveys, one among blood transfusion services and the other among neonatal units in Switzerland. The results demonstrate considerable heterogeneity and a lack of “unité de doctrine”. Establishment of national guidelines would be helpful and warranted. AIMS OF THE STUDY: The aim of the study was to analyse Swiss practices in blood transfusion services and neonatal units for the preparation and administration of red blood cells in newborns. METHODS: Two questionnaires were developed and their results analysed. A first questionnaire was developed for the Swiss blood transfusion services and local hospital haematology laboratories, and a second for the neonatal units in Switzerland. RESULTS: 18/25 (72%) of laboratories and 26/29 (90%) of neonatal units performing red blood cell transfusions participated. Responses revealed a lack of consensus for the majority of questions. Differences were found in all steps of the process, from preparation (testing, irradiation, splitting, shelf life and storage of blood bags) to indication and administration (volume, speed, vascular access, patient monitoring) of red blood cells. Forty-six percent of neonatal units stated that they apply internal guidelines. Nevertheless, all but two would welcome the establishment of national recommendations. CONCLUSION: This study confirmed the large variety in neonatal red blood cell transfusion practices in Switzerland. In the absence of clear evidence, national guidelines – as applied in other countries – would foster a common policy among Swiss neonatologists and facilitate the implementation of a national database for future research and comparison with international literature.
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Transfusão de Eritrócitos/métodos , Transfusão de Eritrócitos/normas , Padrões de Prática Médica/estatística & dados numéricos , Feminino , Saúde Global , Humanos , Recém-Nascido , Masculino , Guias de Prática Clínica como Assunto , Inquéritos e Questionários , SuíçaRESUMO
An increase in abundance and activity of N-methyl D-aspartate receptors (NMDAR) was previously reported for red blood cells (RBCs) of sickle cell disease (SCD) patients. Increased Ca2+ uptake through the receptor supported dehydration and RBC damage. In a pilot phase IIa-b clinical trial MemSID, memantine, a blocker of NMDAR, was used for treatment of four patients for 12 months. Two more patients that have enrolled into the study did not finish it. One of them had psychotic event following the involuntary overdose of the drug, whereas the other had vertigo and could not comply to the trial visits schedule. Acute and durable responses of RBCs of SCD patients to daily oral administration of memantine were monitored. Markers of RBC turnover, changes in cell density, and alterations in ion handling and RBC morphology were assessed. Acute transient shifts in intracellular Ca2+, volume and density, and reduction in plasma lactate dehydrogenate activity were observed already within the first month of treatment. Durable effects of memantine included (a) decrease in reticulocyte counts, (b) reduction in reticulocyte hemoglobinization, (c) advanced membrane maturation and its stabilization as follows from reduction in the number of NMDAR per cell and reduction in hemolysis, and (iv) rehydration and decrease in K+ leakage from patients' RBC. Memantine therapy resulted in reduction in number of cells with sickle morphology that was sustained at least over 2 months after therapy was stopped indicating an improvement in RBC longevity.
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N8-GP (ESPEROCT®; turoctocog alfa pegol; Novo Nordisk A/S, Bagsvaerd, Denmark) is an extended half-life recombinant factor VIII (FVIII) molecule. FVIII-deficient plasma spiked with N8-GP can be accurately measured using many activated partial thromboplastin time (aPTT)-based one-stage clotting assay reagents with normal human plasma calibrators. To date, there are few data on the measurement accuracy of samples from patients treated with N8-GP. Here, we measure patient samples during routine treatment monitoring. Three previously treated patients with severe hemophilia A (HA) without inhibitors (baseline FVIII activity <0.01 IU/mL) received 50 IU/kg N8-GP every fourth day or twice weekly over 5 years as part of the pathfinder2 trial. Patient samples were monitored using the Pathromtin® SL aPTT reagent (Siemens Healthcare GmbH, Erlangen, Germany), a BCS® XP System analyzer (Siemens), and Standard Human Plasma (Siemens) or product-specific calibrators. Patient age ranged from 36 to 62 years. Overall, measurements performed using product-specific or Standard Human Plasma calibrators were in good agreement, with ratios randomly distributed around 1.0. Peak ratios tended to be closer to 1.0 than trough samples. Pathromtin® SL with Standard Human Plasma calibrator consistently and accurately measured FVIII activity in samples from severe HA patients receiving N8-GP prophylaxis.
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Testes de Coagulação Sanguínea/métodos , Fator VIII/análise , Hemofilia A/patologia , Adulto , Fator VIII/uso terapêutico , Hemofilia A/sangue , Hemofilia A/tratamento farmacológico , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Anaemia and iron deficiency are frequent in patients scheduled for cardiac surgery. This study assessed whether immediate preoperative treatment could result in reduced perioperative red blood cell (RBC) transfusions and improved outcome. METHODS: In this single-centre, randomised, double-blind, parallel-group controlled study, patients undergoing elective cardiac surgery with anaemia (n=253; haemoglobin concentration (Hb) <120 g/L in women and Hb <130 g/L in men) or isolated iron deficiency (n=252; ferritin <100 mcg/L, no anaemia) were enrolled. Participants were randomly assigned (1:1) with the use of a computer-generated range minimisation (allocation probability 0·8) to receive either placebo or combination treatment consisting of a slow infusion of 20 mg/kg ferric carboxymaltose, 40â000 U subcutaneous erythropoietin alpha, 1 mg subcutaneous vitamin B12, and 5 mg oral folic acid or placebo on the day before surgery. Primary outcome was the number of RBC transfusions during the first 7 days. This trial is registered with ClinicalTrials.gov, number NCT02031289. FINDINGS: Between Jan 9, 2014, and July 19, 2017, 1006 patients were enrolled; 505 with anaemia or isolated iron deficiency and 501 in the registry. The combination treatment significantly reduced RBC transfusions from a median of one unit in the placebo group (IQR 0-3) to zero units in the treatment group (0-2, during the first 7 days (odds ratio 0·70 [95% CI 0·50-0·98] for each threshold of number of RBC transfusions, p=0·036) and until postoperative day 90 (p=0·018). Despite fewer RBC units transfused, patients in the treatment group had a higher haemoglobin concentration, higher reticulocyte count, and a higher reticulocyte haemoglobin content during the first 7 days (p≤0·001). Combined allogeneic transfusions were less in the treatment group (0 [IQR 0-2]) versus the placebo group (1 [0-3]) during the first 7 days (p=0·038) and until postoperative day 90 (p=0·019). 73 (30%) serious adverse events were reported in the treatment group group versus 79 (33%) in the placebo group. INTERPRETATION: An ultra-short-term combination treatment with intravenous iron, subcutaneous erythropoietin alpha, vitamin B12, and oral folic acid reduced RBC and total allogeneic blood product transfusions in patients with preoperative anaemia or isolated iron deficiency undergoing elective cardiac surgery. FUNDING: Vifor Pharma and Swiss Foundation for Anaesthesia Research.
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Anemia Ferropriva/tratamento farmacológico , Eritropoetina/administração & dosagem , Compostos Férricos/administração & dosagem , Ácido Fólico/administração & dosagem , Maltose/análogos & derivados , Cuidados Pré-Operatórios/métodos , Vitamina B 12/administração & dosagem , Administração Intravenosa , Administração Oral , Idoso , Idoso de 80 Anos ou mais , Anemia Ferropriva/complicações , Procedimentos Cirúrgicos Cardíacos , Método Duplo-Cego , Quimioterapia Combinada , Transfusão de Eritrócitos/estatística & dados numéricos , Feminino , Cardiopatias/complicações , Cardiopatias/cirurgia , Humanos , Masculino , Maltose/administração & dosagem , Pessoa de Meia-Idade , Estudos Prospectivos , Fatores de TempoRESUMO
BACKGROUND AND OBJECTIVE: Nonacog beta pegol (N9-GP) and recombinant factor IX-Fc fusion protein (rFIXFc) are extended half-life rFIX compounds. We report the first single-dose pharmacokinetic trial of N9-GP and rFIXFc. PATIENTS/METHODS: Paradigm 7 was a multicenter, open-label, randomized, crossover trial in previously treated (>150 exposure days) adults with congenital hemophilia B (FIX activity ≤2%). Patients received single intravenous injections (50 IU/kg) of N9-GP and rFIXFc with at least 21 days between doses. Plasma FIX activity, predose, and at serial time points up to 240 hours postdose, was measured using validated one-stage clotting assays (SynthAFax for N9-GP; Actin FSL for rFIXFc) and a chromogenic assay (ROX factor IX) with normal human plasma as calibrator. The primary endpoint was area under the FIX activity-time curve from 0 to infinity, dose-normalized to 50 IU/kg (AUC0-inf,norm). RESULTS: Fifteen patients received study treatment. Based on FIX activity results from the one-stage clotting assays, estimated AUC0-inf,norm was significantly greater for N9-GP than rFIXFc (ratio: 4.39; P < 0.0001, based on a two-sided test on 5% significance level). In addition, N9-GP had a longer terminal half-life, two times higher incremental recovery at 30 minutes and maximum FIX activity (dose-normalized to 50 IU/kg) and six times higher FIX activity at 168 hours than rFIXFc. These findings were largely comparable with the chromogenic assay data and are consistent with published data for each compound. CONCLUSIONS: In this comparison, N9-GP demonstrated favorable pharmacokinetic characteristics versus rFIXFc, helping clinicians to understand differences between N9-GP and rFIXFc. REGISTRATION: This trial is registered with clinicaltrials.gov (NCT03075670) and the European Clinical Trials Database (EudraCT: 2016-001149-25).
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BACKGROUND: Current hemophilia treatment involves frequent intravenous infusions of clotting factors, which is associated with variable hemostatic protection, a high treatment burden, and a risk of the development of inhibitory alloantibodies. Fitusiran, an investigational RNA interference (RNAi) therapy that targets antithrombin (encoded by SERPINC1), is in development to address these and other limitations. METHODS: In this phase 1 dose-escalation study, we enrolled 4 healthy volunteers and 25 participants with moderate or severe hemophilia A or B who did not have inhibitory alloantibodies. Healthy volunteers received a single subcutaneous injection of fitusiran (at a dose of 0.03 mg per kilogram of body weight) or placebo. The participants with hemophilia received three injections of fitusiran administered either once weekly (at a dose of 0.015, 0.045, or 0.075 mg per kilogram) or once monthly (at a dose of 0.225, 0.45, 0.9, or 1.8 mg per kilogram or a fixed dose of 80 mg). The study objectives were to assess the pharmacokinetic and pharmacodynamic characteristics and safety of fitusiran. RESULTS: No thromboembolic events were observed during the study. The most common adverse events were mild injection-site reactions. Plasma levels of fitusiran increased in a dose-dependent manner and showed no accumulation with repeated administration. The monthly regimen induced a dose-dependent mean maximum antithrombin reduction of 70 to 89% from baseline. A reduction in the antithrombin level of more than 75% from baseline resulted in median peak thrombin values at the lower end of the range observed in healthy participants. CONCLUSIONS: Once-monthly subcutaneous administration of fitusiran resulted in dose-dependent lowering of the antithrombin level and increased thrombin generation in participants with hemophilia A or B who did not have inhibitory alloantibodies. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02035605 .).