Efanesoctocog alfa: the renaissance of Factor VIII replacement therapy.

Efanesoctocog alfa (ALTUVIIIOTM, Sanofi-SOBI) is a B domain-deleted single-chain Factor VIII (FVIII) connected to D'D3 domain of von Willebrand Factor (VWF). Its ingenious design allows efanesoctocog alfa to operate independently of endogenous VWF and results in an outstanding 3-4 times longer half-life compared to standard and extended half-life (EHL) FVIII products. The prolonged half-life ensures sustained high levels of factor activity, maintaining normal to near-normal ranges for the majority of the week, facilitating the convenience of once-weekly administration. Efanesoctocog alfa received regulatory approval in 2023 for application in both adults and children with inherited hemophilia A in the United States and Japan. Its sanctioned use encompasses both prophylaxis and on demand treatment for bleeding episodes. The European Medicines Agency (EMA) is currently undertaking a comprehensive review of ALTUVIIIOTM. This comprehensive review focuses on the immunological profile of efanesoctocog alfa, a highly sophisticated new class of EHL FVIII molecule. The integration of the VWF D'D3 domain, XTEN polypeptides, and potential regulatory T-cell epitopes within various segments of efanesoctocog alfa collectively serves as a mitigating factor against the development of a neutralizing T-cell-mediated immune response. We hypothesize that such distinctive attribute may significantly reduce the risk of neutralizing antibodies, particularly in previously untreated patients. The discussion extends beyond regulatory approval to encompass the preclinical and clinical development of efanesoctocog alfa, including considerations for laboratory monitoring. The review also highlights areas that warrant further investigation to deepen our understanding of this groundbreaking therapeutic agent.

Perspectives and perception of haemophilia gene therapy by French patients.

INTRODUCTION AND AIM: A national survey was initiated by representatives of French patients with haemophilia (AFH) and the French reference centre for haemophilia, in order to appreciate the awareness and knowledge of these patients regarding haemophilia gene therapy (HGT) and understand better their position about this innovative treatment that will soon become available. RESULTS: Of 143 answers received, 137 could be analysed, representing about 3.5% of patients with severe or moderate haemophilia over 16year-old. They were 80.3% with haemophilia A and 19.7 % with haemophilia B, with a severe form of the disease for 80.3 % of them. Curiosity for HGT was formulated by 64.2% of the participants, 33.6 % being interested by this approach as soon as it will be available and 38.7 % preferring to wait until more patients have been treated. Only 3.6 % of the participants would never consider receiving HGT. The level of awareness and knowledge was estimated to be limited by 39.5 % of the patients. More than 60 % of them declared having never or almost never discussed HGT with the team of their haemophilia centre. Before deciding to get HGT, 54.4 % of the participants considered that it will be very important to compare it with their current treatment and 53.7 % would like to be better informed by their care providers. CONCLUSIONS: These results highlight the need for training and education for patients, but also for professionals at haemophilia centres, about HGT and the shared decision-making process. Objective, unbiased and transparent information must be available for patients about this very promising therapy which nonetheless carries more uncertainty and unknowns compared to other haemophilia treatments.

Comparison of one-stage and chromogenic factor VIII assays to tailor the dose of recombinant factor VIII-Fc fusion protein (rFVIIIFc, efmoroctocog alfa) in adult patients with haemophilia A: Single-centre, real-world experience of surgery.

BACKGROUND: Efmoroctocog alfa (rFVIIIFc) is an extended half-life FVIII used notably in surgery for patients with haemophilia A. More information is needed of its usage in real-life. METHODS: Adult patients with HA followed at the Lyon Comprehensive Hemophilia Care Center who underwent a surgery with rFVIIIFc were included in this retrospective analysis. The pharmacokinetics of rFVIIIFc was assessed by plasma factor VIII clotting activity (FVIII:C) using both one-stage (OSA) and chromogenic substrate (CSA) assays. RESULTS: A total of 39 major and 31 minor surgeries were performed in 49 patients treated with rFVIIIFc. The median dose of rFVIIIFc infused before major and minor surgeries respectively was 67.5 ((interquartile range [IQR] 52.6-76.9) and 48.0 (38.5-51.8) IU/kg. For major surgeries, during the first postoperative week, the median residual FVIII:C was 78 (64.5-101.5) IU/dL with OSA and 99 (71-118) IU/dL with CSA (p < .0001). After surgery, rFVIIIFc doses were adjusted according to CSA results. This led to a significant decrease of rFVIIIFc consumption compared to what would have been proposed according to the OSA assay, without unusual bleeding or appearance of inhibitor. Considering the high price of the molecule, this was also associated with a significant cost reduction. CONCLUSION: Dose adjustment of rFVIIIFc according to FVIII: C measured by CSA is effective, safe and well tolerated in patients with haemophilia A undergoing invasive surgery.

Eptacog beta for the management of patients with haemophilia A and B with inhibitors: A European perspective.

Eptacog beta (activated), a recombinant human factor VIIa (rFVIIa), was approved by the US Food and Drug Administration (FDA) in 2020 (SEVENFACT®, LFB & HEMA Biologics) and the European Medicines Agency (EMA) in 2022 (CEVENFACTA®, LFB). In Europe, eptacog beta is indicated for the treatment of bleeds and the prevention of bleeds during surgery or invasive procedures in adults and adolescents (≥12 years old) with congenital haemophilia A or B with high-titre inhibitors (≥5 BU) or with low-titre inhibitors who are expected to have a high anamnestic response to factor VIII or factor IX, or to be refractory to increased dosing of these factors. The efficacy and safety of eptacog beta were evaluated in three Phase III clinical studies, PERSEPT 1, 2 and 3. For the EMA filing dossier, the analysis of data from PERSEPT 1 and 2 differed from the analysis used to support the filing in the US. In this review, we summarise current data regarding the mode of action, clinical efficacy and safety of eptacog beta for the management of haemophilia A and B in patients with inhibitors from a European perspective. In addition to providing a valuable summary of the analyses of the clinical data for eptacog beta conducted for the EMA, our review summarises the potential differentiators for eptacog beta compared with other current bypassing agents.

Relationship between plasma tissue Factor Pathway Inhibitor (TFPI) levels, thrombin generation and clinical risk of bleeding in patients with severe haemophilia A or B.

INTRODUCTION: Bleeding severity in severe haemophilic patients, with low thrombin generation (TG) capacity, can vary widely between patients, possibly reflecting differences in tissue factor pathway inhibitor (TFPI) level. AIM: To compare free TFPI (fTFPI) levels in patients with severe haemophilia A (sHA) and severe haemophilia B (sHB) and to investigate in these patients as a whole the relationships between bleeding and TG potential, between TG potential and fTFPI level and between fTFPI level and bleeding tendency. METHODS: Data on bleeding episodes retrospectively recorded during follow-up visits over 5-10 years were collected and used to calculate the annualised joint bleeding rate (AJBR). fTFPI levels and basal TG parameters were determined in platelet-poor plasma (PPP) and platelet-rich plasma (PRP) using calibrated automated tomography (CAT). RESULTS: Mean fTFPI levels did not differ significantly between sHA (n = 34) and sHB (n = 19) patients. Mean values of endogenous thrombin potential (ETP) and thrombin peak (peak) in PPP and PRP were two-fold higher when fTFPI levels < 9.4 versus > 14.3 ng/mL. In patients treated on demand, ETP and peak in PRP were doubled when AJBR was ≤ 4.9 $ \le 4.9$ , AJBR being halved in patients with a low fTFPI level (9.4 ng/mL). In patients on factor prophylaxis, no association was found between TG parameters and either fTFPI level or AJBR. CONCLUSION: In patients treated on demand, bleeding tendency was influenced by fTFPI levels, which in turn affected basal TG potential. In patients on prophylaxis, bleeding tendency is probably determined primarily by the intensity of this treatment.

The obstetrical consequences of ischemic stroke in women of childbearing age.

PURPOSE: Although recurrence risk is a major concern for women having had an ischemic stroke (IS) and who are planning a pregnancy, studies on recurrence risk and pregnancy outcomes are scarce and heterogeneous. METHODS: This retrospective study assessed women aged 15-44 years with a diagnosis of ischemic stroke admitted in the Lyon Stroke Centre, France, between January 2009 and December 2013. The primary outcome was stroke recurrence during pregnancy or the post-partum period. Secondary outcomes were pregnancy complications. RESULTS: Overall, 104 women with a prior ischemic stroke were included. Mean age at the time of the stroke was 36 ± 6.7 years old. Stroke etiology was large-artery atherosclerosis for 1 woman, cardioembolism for 23 women, and undetermined for 55 women. No antiphospholipid syndrome was found. Among them, 29 women had 58 subsequent pregnancies. Overall, there were three IS recurrence (2.9%), but none occurred during pregnancy. There were 27 miscarriages (47% of pregnancies), two pre-eclampsia (3%), and one stillbirth (1.7%). CONCLUSIONS: We observed no recurrence of IS during pregnancy. The study also highlighted that the risk of miscarriages was higher than general population and that of stillbirth should be further studied.

Increased retention of functional mitochondria in mature sickle red blood cells is associated with increased sickling tendency, hemolysis and oxidative stress.

Abnormal retention of mitochondria in mature red blood cells (RBC) has been recently reported in sickle cell anemia (SCA) but their functionality and their role in the pathophysiology of SCA remain unknown. The presence of mitochondria within RBC was determined by flow cytometry in 61 SCA patients and ten healthy donors. Patients were classified according to the percentage of mature RBC with mitochondria contained in the whole RBC population: low (0-4%), moderate (>4% and <8%), or high level (>8%). RBC rheological, hematological, senescence and oxidative stress markers were compared between the three groups. RBC senescence and oxidative stress markers were also compared between mature RBC containing mitochondria and those without. The functionality of residual mitochondria in sickle RBC was measured by high-resolution respirometry assay and showed detectable mitochondrial oxygen consumption in sickle mature RBC but not in healthy RBC. Increased levels of mitochondrial reactive oxygen species were observed in mature sickle RBC when incubated with Antimycin A versus without. In addition, mature RBC retaining mitochondria exhibited greater levels of reactive oxygen species compared to RBC without mitochondria, as well as greater Ca2+, lower CD47 and greater phosphatidylserine exposure. Hematocrit and RBC deformability were lower, and the propensity of RBC to sickle under deoxygenation was higher, in the SCA group with a high percentage of mitochondria retention in mature RBC. This study showed the presence of functional mitochondria in mature sickle RBC, which could favor RBC sickling and accelerate RBC senescence, leading to increased cellular fragility and hemolysis.

Evaluation of the care pathway in the context of the dispensing of emicizumab (Hemlibra) in community and hospital pharmacies in France: A patient satisfaction survey.

INTRODUCTION: Since June 2021 in France, patients with haemophilia A with anti-factor VIII inhibitors and patients with severe haemophilia A without anti-factor VIII inhibitors, and treated with emicizumab (Hemlibra), have to choose the dispensing circuit community or hospital pharmacy. AIM: To evaluate satisfaction of patients whether they choose dispensation from a community pharmacy or retained dispensation from the hospital pharmacy, to understand the main motivation for choosing the community or the hospital pharmacy. METHODS: All patients living in France, regardless of age, were eligible to participate. Between September 13, 2022, and January 9, 2023, 175 respondents answered the satisfaction survey, including 123 in community pharmacy and 52 in hospital pharmacy. RESULTS: Eighteen months after availability in community pharmacies, treatment accessibility is improved for the benefit of the patient. The door-to-door travel times are significantly reduced to the community pharmacy with an average gain of 16.5 min saved from the place of residence. Patients are mostly satisfied with the new dispensing circuit especially concerning the overall satisfaction (p < .0001), the travel time (p < .0001) and the strong relationship with the pharmacist (p = .0022) compared to hospital pharmacy. CONCLUSION: Innovation in care pathways is showing its full potential in improving access to medication, made possible by the implementation of a rigorous organization accompanied by training to enable healthcare professionals involved in primary care to provide appropriate management.

Whole F8 gene sequencing combined with splicing functional analyses led to a substantial increase of the molecular diagnosis yield for non-severe haemophilia A.

INTRODUCTION: Conventional genetic investigation fails to identify the F8 causal variant in 2.5%-10% of haemophilia A (HA) patients with non-severe phenotypes. In these cases, F8 deep intronic variants could be causal. AIM: To identify pathogenic F8 deep intronic variants in genetically unresolved families with non-severe HA analysed in the haematology laboratory of the Hospices Civils de Lyon. METHODS: The whole F8 was analysed by next generation sequencing. The pathogenic impact of candidate variants identified was assessed using both in silico analysis (MaxEntScan and spliceAI) and functional analysis (RNA or minigene assay). RESULTS: Sequencing was performed in 49/55 families included for which a DNA sample from a male propositus was available. In total, 33 candidate variants from 43 propositi were identified. These variants corresponded to 31 single nucleotide substitutions, one 173-bp deletion, and an 869-bp tandem triplication. No candidate variant was found in six propositi. The most frequent variants found were the association of [c.2113+1154G>C and c.5374-304C>T], identified in five propositi, and the c.2114-6529C>G identified in nine propositi. Four variants had been previously described as HA-causing. Splicing functional assay found a deleterious impact for 11 substitutions (c.671-94G>A, c.788-312A>G, c.2113+1154G>C, c.2114-6529C>G, c.5999-820A>T, c.5999-786C>A, c.5999-669G>T, c.5999-669G>A, c.5999-669G>C, c.6900+4104A>C, and c.6901-2992A>G). The HA-causing variant was identified in 33/49 (67%) cases. In total, F8 deep intronic variants caused 8.8% of the non-severe HA among the 1643 families analysed in our laboratory. CONCLUSION: The results emphasise the value of whole F8 gene sequencing combined with splicing functional analyses to improve the diagnosis yield for non-severe HA.

Reinvestigation of unidentified causative variants in FXI-deficient patients: Focus on gene segment deletions.

INTRODUCTION: Data on failure to identify the molecular mechanism underlying FXI deficiency by Sanger analysis and the contribution of gene segment deletions are almost inexistent. AIMS AND METHODS: Prospective and retrospective analysis was conducted on FXI-deficient patients' DNA via Next Generation Sequencing (NGS), or Sanger sequencing and Multiplex Probe Ligation-dependent Assay (MLPA) to detect cryptic causative gene variants or gene segment deletions. RESULTS: Sanger analysis or NGS enabled us to identify six severe and one partial (median activity 41 IU/dl) FXI deficient index cases with deletions encompassing exons 11-15, the whole gene, or both. After Sanger sequencing, retrospective evaluation using MLPA detected seven additional deletion cases in apparently homozygous cases in non-consanguineous families, or in previously unsolved FXI-deficiency cases. Among the 504 index cases with a complete genetic investigation (Sanger/MLPA, or NGS), 23 remained unsolved (no abnormality found [n = 14] or rare intronic variants currently under investigation, [n = 9]). In the 481 solved cases (95% efficiency), we identified F11 gene-deleted patients (14 cases; 2.9%). Among these, whole gene deletion accounted for four heterozygous cases, exons 11-15 deletion for five heterozygous and three homozygous ones, while compound heterozygous deletion and isolated exon 12 deletion accounted for one case each. CONCLUSION: Given the high incidence of deletions in our population (2.9%), MLPA (or NGS with a reliable bioinformatic pipeline) should be systematically performed for unsolved FXI deficiencies or apparently homozygous cases in non-consanguineous families.

Characterization of a recombinant factor IX molecule fused to coagulation factor XIII-B subunit.

INTRODUCTION AND AIM: Severe haemophilia B (HB) is characterized by spontaneous bleeding episodes, mostly into joints. Recurrent bleeds lead to progressive joint destruction called haemophilic arthropathy. The current concept of prophylaxis aims at maintaining the FIX level >3-5 IU/dL, which is effective at reducing the incidence of haemophilic arthropathy. Extended half-life FIX molecules make it easier to achieve these target trough levels compared to standard FIX concentrates. We previously reported that the fusion of a recombinant FIX (rFIX) to factor XIII-B (FXIIIB) subunit prolonged the half-life of the rFIX-LXa-FXIIIB fusion molecule in mice and rats 3.9- and 2.2-fold, respectively, compared with rFIX-WT. However, the mechanism behind the extended half-life was not known. MATERIALS AND METHODS: Mass spectrometry and ITC were used to study interactions of rFIX-LXa-FXIIIB with albumin. Pharmacokinetic analyses in fibrinogen-KO and FcRn-KO mice were performed to evaluate the effect of albumin and fibrinogen on in-vivo half-life of rFIX-LXa-FXIIIB. Finally saphenous vein bleeding model was used to assess in-vivo haemostatic activity of rFIX-LXa-FXIIIB. RESULTS AND CONCLUSION: We report here the key interactions that rFIX-LXa-FXIIIB may have in plasma are with fibrinogen and albumin which may mediate its prolonged half-life. In addition, using the saphenous vein bleeding model, we demonstrate that rFIX-FXIIIB elicits functional clot formation that is indistinguishable from that of rFIX-WT.

A focus on dominant negative variants in a series of 170 heterozygous FXI-deficient patients.

INTRODUCTION: Dominant-negative effects have been described for 10 F11 variants in the literature. AIM: The current study aimed at identifying putative dominant-negative F11 variants. MATERIAL AND METHODS: This research consisted in a retrospective analysis of routine laboratory data. RESULTS: In a series of 170 patients with moderate/mild factor XI (FXI) deficiencies, we identified heterozygous carriers of previously reported dominant-negative variants (p.Ser243Phe, p.Cys416Tyr, and p.Gly418Val) with FXI activities inconsistent with a dominant-negative effect. Our findings also do not support a dominant-negative effect of p.Gly418Ala. We also identified a set of patients carrying heterozygous variants, among which five out of 11 are novel, with FXI activities suggesting a dominant-negative effect (p.His53Tyr, p.Cys110Gly, p.Cys140Tyr, p.Glu245Lys, p.Trp246Cys, p.Glu315Lys, p.Ile421Thr, p.Trp425Cys, p.Glu565Lys, p.Thr593Met, and p.Trp617Ter). However, for all but two of these variants, individuals with close to half normal FXI coagulant activity (FXI:C) were identified, indicating an inconstant dominant effect. CONCLUSION: Our data show that for some F11 variants recognized has having dominant-negative effects, such effects actually do not occur in many individuals. The present data suggest that for these patients, the intracellular quality control mechanisms eliminate the variant monomeric polypeptide before homodimer assembly, thereby allowing only the wild-type homodimer to assemble and resulting in half normal activities. In contrast, in patients with markedly decreased activities, some mutant polypeptides might escape this first quality control. In turn, assembly of heterodimeric molecules as well as mutant homodimers would result in activities closer to 1:4 of FXI:C normal range.

Management of rare inherited bleeding disorders: Proposals of the French Reference Centre on Haemophilia and Rare Coagulation Disorders.

INTRODUCTION: The rare coagulation disorders may present significant difficulties in diagnosis and management. In addition, considerable inter-individual variation in bleeding phenotype is observed amongst affected individuals, making the bleeding risk difficult to assess in affected individuals. The last international recommendations on rare inherited bleeding disorders (RIBDs) were published by the United Kingdom Haemophilia Centre Doctors' Organisation in 2014. Since then, new drugs have been marketed, news studies on surgery management in patients with RIBD have been published, and new orphan diseases have been described. AIM: Therefore, the two main objectives of this review, based on the recent recommendations published by the French Reference Centre on Haemophilia and Rare Bleeding Disorders, are: (i) to briefly describe RIBD (clinical presentation and diagnostic work-up) to help physicians in patient screening for the early detection of such disorders; and (ii) to focus on the current management of acute haemorrhages and long term prophylaxis, surgical interventions, and pregnancy/delivery in patients with RIBD.

Report of surgeries, their outcome and the thrombin generation assay in patients with Factor XI deficiency: A retrospective single-centre study.

BACKGROUND: In patients with FXI deficiency, the risk of surgery-related bleeding is poorly correlated with plasma FXI activity (FXI:C); the latter can therefore not be used as a reliable predictor of bleeding in surgeries. OBJECTIVES: The aim of this retrospective study was to determine whether thrombin generation assay (TGA) could be used to evaluate the risk of surgery-related bleeding in FXI-deficient patients. TGA parameters were compared to FXI:C values, haemostatic treatments and surgical outcomes. PATIENTS: All patients followed at the haemophilia treatment care centre (Lyon, France) with a FXI:C < 50IU/dL, and for whom a baseline TGA was performed between January 2014 and December 2019, were included. RESULTS: Among the 175 surgeries reported herein in 49 patients, FXI concentrates were used for 11 (6%) surgeries and fresh frozen plasma was used for five (3%) surgeries; these surgeries were performed in patients with two or three impaired TGA parameters. No haemostatic treatment was prescribed for 119 (68%) surgeries. A surgery-related bleeding occurred in 12 patients during 21 (12%) surgeries. Thrombin generation was significantly reduced or delayed in patients who reported surgery related-bleeding. Among the 34 (68%) surgeries performed without haemostatic treatment in patients with three impaired TGA parameters, a surgery-related bleeding was reported in 44% of cases (15 surgeries out of 34). CONCLUSION: The present study confirmed that TGA is an interesting laboratory test in FXI deficiency, for determining the bleeding risk and guiding the haemostatic management of surgeries, while taking into account the surgical bleeding risk and the history of bleeding.

Increased blood viscosity and red blood cell aggregation in patients with COVID-19.

The aim of this study was to (1) analyze blood viscosity, red blood cell (RBC) deformability, and aggregation in hospitalized patients with Coronavirus disease 19 (COVID-19); (2) test the associations between impaired blood rheology and blood coagulation; and (3) test the associations between impaired blood rheology and several indicators of clinical severity. A total of 172 patients with COVID-19, hospitalized in COVID-unit of the Internal Medicine Department (Lyon, France) participated in this study between January and May 2021. Clinical parameters were collected for each patient. Routine hematological/biochemical parameters, blood viscosity, RBC deformability and aggregation, and RBC senescence markers were measured on the first day of hospitalization. A control group of 38 healthy individuals was constituted to compare the blood rheological and RBC profile. Rotational thromboelastography was performed in 76 patients to study clot formation dynamics. Our study demonstrated that patients with COVID-19 had increased blood viscosity despite lower hematocrit than healthy individuals, as well as increased RBC aggregation. In-vitro experiments demonstrated a strong contribution of plasma fibrinogen in this RBC hyper-aggregation. RBC aggregation correlated positively with clot firmness, negatively with clot formation time, and positively with the length of hospitalization. Patients with oxygen supplementation had higher RBC aggregation and blood viscosity than those without, and patients with pulmonary lesions had higher RBC aggregation and enhanced coagulation than those without. This study is the first to demonstrate blood hyper-viscosity and RBC hyper-aggregation in a large cohort of patients with COVID-19 and describe associations with enhanced coagulation and clinical outcomes.

Arterial and venous thromboembolism in COVID-19: a study-level meta-analysis.

BACKGROUND: The prevalence of venous thromboembolic event (VTE) and arterial thromboembolic event (ATE) thromboembolic events in patients with COVID-19 remains largely unknown. METHODS: In this meta-analysis, we systematically searched for observational studies describing the prevalence of VTE and ATE in COVID-19 up to 30 September 2020. RESULTS: We analysed findings from 102 studies (64 503 patients). The frequency of COVID-19-related VTE was 14.7% (95% CI 12.1% to 17.6%, I2=94%; 56 studies; 16 507 patients). The overall prevalence rates of pulmonary embolism (PE) and leg deep vein thrombosis were 7.8% (95% CI 6.2% to 9.4%, I2=94%; 66 studies; 23 117 patients) and 11.2% (95% CI 8.4% to 14.3%, I2=95%; 48 studies; 13 824 patients), respectively. Few were isolated subsegmental PE. The VTE prevalence was significantly higher in intensive care unit (ICU) (23.2%, 95% CI 17.5% to 29.6%, I2=92%, vs 9.0%, 95% CI 6.9% to 11.4%, I2=95%; pinteraction<0.0001) and in series systematically screening patients compared with series testing symptomatic patients (25.2% vs 12.7%, pinteraction=0.04). The frequency rates of overall ATE, acute coronary syndrome, stroke and other ATE were 3.9% (95% CI 2.0% to to 3.0%, I2=96%; 16 studies; 7939 patients), 1.6% (95% CI 1.0% to 2.2%, I2=93%; 27 studies; 40 597 patients) and 0.9% (95% CI 0.5% to 1.5%, I2=84%; 17 studies; 20 139 patients), respectively. Metaregression and subgroup analyses failed to explain heterogeneity of overall ATE. High heterogeneity limited the value of estimates. CONCLUSIONS: Patients admitted in the ICU for severe COVID-19 had a high risk of VTE. Conversely, further studies are needed to determine the specific effects of COVID-19 on the risk of ATE or VTE in less severe forms of the disease.

Haemostatic effect of adding tranexamic acid to emicizumab prophylaxis in severe haemophilia A: A preclinical study.

BACKGROUND: Patients with severe haemophilia have impaired haemostatic response, delayed clot formation and fibrin clots that are vulnerable to fibrinolysis. Emicizumab is a bispecific antibody that mimics activity of activated factor VIII (FVIII) and increases haemostatic capacity to the level of moderate-to-mild haemophilia, thereby used for prophylaxis. Regardless of the impressive clinical performance of emicizumab, breakthrough bleeds may still occur. We aimed to study, in FVIII knockout mice (FVIII-KO), whether haemostasis is improved with the addition of tranexamic acid (TxAc) to emicizumab. METHODS: FVIII-KO mice received prophylaxis with emicizumab or emicizumab+TxAc before trauma. FVIII-KO mice were given emicizumab 1.5 mg/kg via IV injection. A second retro-orbital IV injection containing human FIX and FX (both 100U/kg) was given 24 h later and 5 min before the tail amputation or knee trauma. After trauma-induced knee joint bleeding, magnetic resonance imaging (MRI), and histological analysis were used to compare haemostatic efficacy of the two prophylactic strategies. Thrombin generation (TG) was measured and clots obtained with TG experiment were analysed by scanning electron microscopy. RESULTS: In FVIII-KO mice, blood loss after tail clip was lower after prophylaxis with emicizumab+TxAc compared to emicizumab. MRI results and histological analysis of knee joints showed that the addition of TxAc significantly decreased joint bleeding. Fibrin fibre diameters of mice treated with emicizumab only was thicker than those who received combined prophylaxis with emicizumab+TxAc. CONCLUSION: Our results suggest a potential benefit of TxAc when used in combination with emicizumab in prophylactic settings, especially in patients presenting breakthrough bleeds.

Eltrombopag for the Treatment of Severe Inherited Thrombocytopenia.

Inherited thrombocytopenias correspond to a group of hereditary disorders characterized by a reduced platelet count, platelet dysfunction, and a family history of thrombocytopenia. It is commonly associated with mucocutaneous bleeding. Thrombocytopenia results from mutations in genes involved in megakaryocyte differentiation, platelet formation, and clearance. Here we report on a patient presenting with severe syndromic inherited thrombocytopenia manifesting as spontaneous mucocutaneous bleeds, requiring frequent platelet transfusions. Thrombocytopenia was explained by the presence of 4 mutations in 3 hematopoietic transcription factor genes: FLI1, RUNX1, and ETV6. The patient was successfully treated with high-dose eltrombopag at 150 mg/day, an orally available non-peptide thrombopoietin receptor agonist. Since the start of treatment 23 months ago, the manifestations of bleeding have resolved, and no platelet transfusions or corticosteroids have been required. The patient has no clinical or laboratory evidence of myeloid malignancy so far.

A new paradigm for personalized prophylaxis for patients with severe haemophilia A.

AIM: For patients with severe haemophilia A, guidelines recommend prophylactic treatment with FVIII, with dose calculations targeting a predetermined FVIII trough level. However, this pharmacokinetic (PK) approach is suboptimal, with some patients experiencing breakthrough bleeds. We aimed to improve FVIII dosing by incorporating the thrombin generation assay, a global haemostasis assay whose main pharmacodynamic (PD) parameter, endogenous thrombin potential (ETP), predicts spontaneous bleeding risk. METHODS: We performed post hoc combined PK-PD modelling using data from 66 adults who received human-cl rhFVIII (Nuwiq® , Octapharma AG) in a phase IIIb study. Time-to-event analyses simulated the probability of spontaneous bleeding for different FVIII exposures and baseline ETPs. RESULTS: Ninety-one spontaneous bleeds occurred in 20/66 patients. The relationship between FVIII:C and ETP was non-linear, and the sigmoid Emax model adequately described the data. Individual PK-PD Bayesian estimation significantly improved predictive performance. Simulations showed that the mean spontaneous annual bleeding rate decreased with increasing baseline ETP or dosing: with ETP values of 200, 400 and 600 (nmol/L)·min annual bleeding rates were 2.36, 1.25 and 0.66, respectively, on 40 IU/kg human-cl rhFVIII every 3 days; and annual bleeding rates were 2.09, 1.10, and 0.60, respectively, on 60 IU/kg every 3 days. CONCLUSION: Prophylactic FVIII dosing is more clinically meaningful when incorporating ETP alongside FVIII level. For the first time, FVIII dosing can be personalized with the aim of eliminating spontaneous breakthrough bleeds.

Reversal of rivaroxaban anticoagulant effect by prothrombin complex concentrates: which dose is sufficient to restore normal thrombin generation?

Rivaroxaban has the most available data to support the use of prothrombin complex concentrates (PCC) as a reversal agent. However, PCC might increase the incidence of thrombotic events by shifting the haemostatic balance towards hypercoagulability. We assessed the in vitro efficacy and safety of three 4-factor PCCs for reversing rivaroxaban anticoagulant effect. Our in vitro finding indicates that 4-factor PCCs at the dose of 25 U.kg- 1 may be sufficient to reverse rivaroxaban anticoagulant effect.