Hemophilia A subjects with an intron-22 gene inversion mutation show CD4+ T-effector responses to multiple epitopes in FVIII.

Background: Almost half of severe hemophilia A (HA) is caused by an intron 22 inversion mutation (Int22Inv), which disrupts the 26-exon F8 gene. Inverted F8 mRNA exons 1-22 are transcribed, while F8B mRNA, containing F8 exons 23-26, is transcribed from a promoter within intron 22. Neither FVIII activity nor FVIII antigen (cross-reacting material, CRM) are detectable in plasma of patients with an intron-22 inversion. Objectives: To test the hypothesis that (putative) intracellular synthesis of FVIII proteins encoded by inverted F8 and F8B mRNAs confers T-cell tolerance to almost the entire FVIII sequence, and to evaluate the immunogenicity of the region encoded by the F8 exon 22-23 junction sequence. Patients/Methods: Peripheral blood mononuclear cells (PBMCs) from 30 severe or moderate HA subjects (17 with an Int22Inv mutation) were tested by ELISPOT assays to detect cytokine secretion in response to FVIII proteins and peptides and to map immunodominant T-cell epitopes. Potential immunogenicity of FVIII sequences encoded by the F8 exon 22-23 junction region was also tested using peptide-MHCII binding assays. Results: Eight of the Int22Inv subjects showed robust cytokine secretion from PBMCs stimulated with FVIII proteins and/or peptides, consistent with earlier publications from the Conti-Fine group. Peptide ELISPOT assays identified immunogenic regions of FVIII. Specificity for sequences encoded within F8 mRNA exons 1-22 and F8B mRNA was confirmed by staining Int22Inv CD4+ T cells with peptide-loaded HLA-Class II tetramers. FVIII peptides spanning the F8 exon 22-23 junction (encoding M2124-V2125) showed limited binding to MHCII proteins and low immunogenicity, with cytokine secretion from only one Int22Inv subject. Conclusions: PBMCs from multiple subjects with an Int22Inv mutation, with and without a current FVIII inhibitor, responded to FVIII epitopes. Furthermore, the FVIII region encoded by the exon 22-23 junction sequence was not remarkably immunoreactive and is therefore unlikely to contain an immunodominant, promiscuous CD4+ T-cell epitope. Our results indicate that putative intracellular expression of partial FVIII proteins does not confer T-cell tolerance to FVIII regions encoded by inverted F8 mRNA or F8B mRNA.

Natural and engineered mediators of desiccation tolerance stabilize Human Blood Clotting Factor VIII in a dry state.

Biologics, pharmaceuticals containing or derived from living organisms, such as vaccines, antibodies, stem cells, blood, and blood products are a cornerstone of modern medicine. However, nearly all biologics have a major deficiency: they are inherently unstable, requiring storage under constant cold conditions. The so-called 'cold-chain', while effective, represents a serious economic and logistical hurdle for deploying biologics in remote, underdeveloped, or austere settings where access to cold-chain infrastructure ranging from refrigerators and freezers to stable electricity is limited. To address this issue, we explore the possibility of using anhydrobiosis, the ability of organisms such as tardigrades to enter a reversible state of suspended animation brought on by extreme drying, as a jumping off point in the development of dry storage technology that would allow biologics to be kept in a desiccated state under not only ambient but elevated temperatures. Here we examine the ability of different protein and sugar-based mediators of anhydrobiosis derived from tardigrades and other anhydrobiotic organisms to stabilize Human Blood Clotting Factor VIII under repeated dehydration/rehydration cycles, thermal stress, and long-term dry storage conditions. We find that while both protein and sugar-based protectants can stabilize the biologic pharmaceutical Human Blood Clotting Factor VIII under all these conditions, protein-based mediators offer more accessible avenues for engineering and thus tuning of protective function. Using classic protein engineering approaches, we fine tune the biophysical properties of a protein-based mediator of anhydrobiosis derived from a tardigrade, CAHS D. Modulating the ability of CAHS D to form hydrogels make the protein better or worse at providing protection to Human Blood Clotting Factor VIII under different conditions. This study demonstrates the effectiveness of tardigrade CAHS proteins and other mediators of desiccation tolerance at preserving the function of a biologic without the need for the cold-chain. In addition, our study demonstrates that engineering approaches can tune natural products to serve specific protective functions, such as coping with desiccation cycling versus thermal stress. Ultimately, these findings provide a proof of principle that our reliance on the cold-chain to stabilize life-saving pharmaceuticals can be broken using natural and engineered mediators of desiccation tolerance.

Upregulation of Coagulation Factor VIII and Fibrinogen After Pulmonary Endarterectomy in Patients with Chronic Thromboembolic Pulmonary Hypertension.

OBJECTIVES: Chronic thromboembolic pulmonary hypertension (CTEPH) is associated with thrombotic states including elevated coagulation factor VIII (FVIII). Pulmonary endarterectomy (PEA) is the main treatment for CTEPH, and efficient anticoagulation is essential to prevent thromboembolism recurrence after surgery. We aimed to characterize longitudinal changes in FVIII and other coagulation biomarkers after PEA. METHODS: Coagulation biomarker levels were measured at baseline and up to 12 months after operation in 17 consecutive patients with PEA. Temporal patterns of coagulation biomarkers, and correlation of FVIII with other coagulation biomarkers, were analyzed. RESULTS: Baseline FVIII levels were elevated in 71% of the patients (mean 216 ± 67 IU/dl). FVIII doubled 7 days after PEA, peaking at 471 ± 87 IU/dl, and gradually returned to respective baseline levels within 3 months. Postoperative fibrinogen levels were also elevated. Antithrombin decreased at 1 to 3 days, D-dimer increased at 1 to 4 weeks, and thrombocytosis was observed at 2 weeks. CONCLUSIONS: FVIII is elevated in most patients with CTEPH. After PEA, early but transient elevation of FVIII and fibrinogen, and delayed reactive thrombocytosis, occurs, and warrants careful postoperative anticoagulation to prevent thromboembolism recurrence.

Switch to pdVWF:pdFVIII concentrate for prophylaxis in a paediatric patient with Type 3 von Willebrand disease: a case report.

OBJECTIVES: To report the long-term prophylaxis management of a child with type 3 von Willebrand disease by switching to Wilate (Octapharma AG), a plasma-derived, double virus-inactivated concentrate of freeze-dried of a 1 to 1 ratio of active Von Willebrand Factor and Factor VIII (pdVWF:pdFVIII) recently marketed as Eqwilate in France. METHODS: This is a case report of 12.6-year-old boy with congenital Type 3 VWD who had a history of frequent bleeds. Prophylaxis started at the age of 38 months with FVIII-poor pdVWF concentrate (Wilfactin, LFB) and FVIII (Wilstart, LFB). Pharmacokinetics and thrombin generation assay were performed. Annualized bleeding rate was derived from the bleeding episodes documented in the medical record during a 24-month period before and after starting pdVWF:pdFVIII concentrate. RESULTS: Both product injections promptly raised the endogenous thrombin potential (ETP). However, the maximal concentration of formed thrombin was higher following pdVWF:pdFVIII injection. Due to a high bleeds frequency and better results regarding FVIII levels and thrombin generation, the prophylaxis regimen was changed to the same dose and frequency of pdVWF:pdFVIII concentrate (42 IU/kg per day, three times a week). During the last 24 months, annualized total, trauma, and spontaneous bleeding rates were 7.5, 4.5, and 3, respectively. These rates decreased to 2, 1.5, and 0.5 respectively during the next two years. The mother reported a marked improvement in the quality of life of his son and hers. CONCLUSION: Switch to pdVWF:pdFVIII concentrate for long-term prophylaxis in a young type 3 VWD patient was safe and effective in reducing bleeds.

Preparation of Cryoprecipitate and Cryo-depleted Plasma for Proteomic Research Analysis.

When frozen plasma is slowly thawed in cold conditions (1-6 °C), high-molecular-weight plasma proteins precipitate forming a concentrate known as cryoprecipitate. The concentrate is enriched with several important coagulation proteins, including fibrinogen, antihemophilic factor (factor VIII), von Willebrand factor, fibrin stabilizing factor (factor XIII), fibronectin, and small amounts of other plasma proteins. In current medical practice, clinical-grade preparations of cryoprecipitate are used mostly to correct fibrinogen deficiency caused by acute blood loss or due to functional abnormalities of the fibrinogen protein. In the past, cryoprecipitate was used to treat von Willebrand disease and hemophilia A (factor VIII deficiency), but the availability of more highly purified coagulation factor concentrates or recombinant protein preparations has superseded the use of cryoprecipitate for these coagulopathies. Cryo-depleted plasma (also called cryosupernatant) is the plasma supernatant remaining following removal of the cryoprecipitate from frozen-thawed plasma and contains all the remaining soluble plasma proteins. This protocol describes the research-scale preparation of cryoprecipitate and cryo-depleted plasma suitable for proteomic studies and is based on the procedures used to prepare clinical-grade cryoprecipitate.

Spectrum of Causative Mutations in Patients with Hemophilia A in Russia.

Hemophilia A (HA) is one of the most widespread, X-linked, inherited bleeding disorders, which results from defects in the F8 gene. Nowadays, more than 3500 different pathogenic variants leading to HA have been described. Mutation analysis in HA is essential for accurate genetic counseling of patients and their relatives. We analyzed patients from 273 unrelated families with different forms of HA. The analysis consisted of testing for intron inversion (inv22 and inv1), and then sequencing all functionally important F8 gene fragments. We identified 101 different pathogenic variants in 267 patients, among which 35 variants had never been previously reported in international databases. We found inv22 in 136 cases and inv1 in 12 patients. Large deletions (1-8 exons) were found in 5 patients, and we identified a large insertion in 1 patient. The remaining 113 patients carried point variants involving either single nucleotide or several consecutive nucleotides. We report herein the largest genetic analysis of HA patients issued in Russia.

Two-Year Outcomes of Valoctocogene Roxaparvovec Therapy for Hemophilia A.

BACKGROUND: Valoctocogene roxaparvovec delivers a B-domain-deleted factor VIII coding sequence with an adeno-associated virus vector to prevent bleeding in persons with severe hemophilia A. The findings of a phase 3 study of the efficacy and safety of valoctocogene roxaparvovec therapy evaluated after 52 weeks in men with severe hemophilia A have been published previously. METHODS: We conducted an open-label, single-group, multicenter, phase 3 trial in which 134 men with severe hemophilia A who were receiving factor VIII prophylaxis received a single infusion of 6×1013 vector genomes of valoctocogene roxaparvovec per kilogram of body weight. The primary end point was the change from baseline in the annualized rate of treated bleeding events at week 104 after receipt of the infusion. The pharmacokinetics of valoctocogene roxaparvovec were modeled to estimate the bleeding risk relative to the activity of transgene-derived factor VIII. RESULTS: At week 104, a total of 132 participants, including 112 with data that were prospectively collected at baseline, remained in the study. The mean annualized treated bleeding rate decreased by 84.5% from baseline (P<0.001) among the participants. From week 76 onward, the trajectory of the transgene-derived factor VIII activity showed first-order elimination kinetics; the model-estimated typical half-life of the transgene-derived factor VIII production system was 123 weeks (95% confidence interval, 84 to 232). The risk of joint bleeding was estimated among the trial participants; at a transgene-derived factor VIII level of 5 IU per deciliter measured with chromogenic assay, we expected that participants would have 1.0 episode of joint bleeding per year. At 2 years postinfusion, no new safety signals had emerged and no new serious adverse events related to treatment had occurred. CONCLUSIONS: The study data show the durability of factor VIII activity and bleeding reduction and the safety profile of valoctocogene roxaparvovec at least 2 years after the gene transfer. Models of the risk of joint bleeding suggest that the relationship between transgene-derived factor VIII activity and bleeding episodes is similar to that reported with the use of epidemiologic data for persons with mild-to-moderate hemophilia A. (Funded by BioMarin Pharmaceutical; GENEr8-1 ClinicalTrials.gov number, NCT03370913.).

Body Mass Index and Waist Circumference as Determinants of Hemostatic Factors in Participants of a Population-Based Study.

Background: In contrast to studies in patients, an association between obesity and blood coagulation factors has not been established in the population. If confirmed it could become a target for primary prevention. Objective: To investigate the relationship between Body Mass Index (BMI) and waist circumference (WC) with plasma concentrations of antithrombin III, D-dimers, fibrinogen D, protein S, factor VIII, activated partial thromboplastin time (aPTT), quick value, and international normalized ratio (INR) in the general population. Materials and Methods: Participants of the Cooperative Health Research in the Region of Augsburg (KORA) S4 study who took part in the KORA Fit follow-up (2018-2019, aged 54-74 years) examination were eligible. Citrate plasma samples were collected in fasted participants. After the exclusion of participants with anticoagulative treatment, 776 participants (420 women and 356 men) with analytic data on hemostatic factors were included in the present analysis. Linear regression models were used to explore the association between BMI or WC with hemostatic markers, adjusted for sex, age, alcohol consumption, education, smoking status, and physical activity. In a second model, additional adjustments were made for the prevalence of stroke, hypertension, myocardial infarction, serum non-HDL cholesterol, and serum triglycerides. Results: In the multivariable models (with or without health conditions), significant positive associations with BMI were obtained for plasma concentrations of D-dimers, factor VIII, fibrinogen D, protein S, and quick value, while INR and antithrombin III were inversely associated. Similar to BMI, WC was significantly associated with all hemostatic factors, except for aPTT. Conclusion: In this population-based study, both increasing BMI and WC affect the blood coagulation system. Thus, modification of a prothrombotic coagulation profile emerged as a potential target for primary prevention in obese subjects.

Macrophage Galactose Lectin Contributes to the Regulation of FVIII (Factor VIII) Clearance in Mice-Brief Report.

BACKGROUND: Although most plasma FVIII (Factor VIII) circulates in complex with VWF (von Willebrand factor), a minority (3%-5%) circulates as free-FVIII, which is rapidly cleared. Consequently, 20% of total FVIII may be cleared as free-FVIII. Critically, the mechanisms of free-FVIII clearance remain poorly understood. However, recent studies have implicated the MGL (macrophage galactose lectin) in modulating VWF clearance. METHODS: Since VWF and FVIII share similar glycosylation, we investigated the role of MGL in FVIII clearance. FVIII binding to MGL was assessed in immunosorbent and cell-based assays. In vivo, FVIII clearance was assessed in MGL1-/- and VWF-/-/FVIII-/- mice. RESULTS: In vitro-binding studies identified MGL as a novel macrophage receptor that binds free-FVIII in a glycan-dependent manner. MGL1-/- and MGL1-/- mice who received an anti-MGL1/2 blocking antibody both showed significantly increased endogenous FVIII activity compared with wild-type mice (P=0.036 and P<0.0001, respectively). MGL inhibition also prolonged the half-life of infused FVIII in FVIII-/- mice. To assess whether MGL plays a role in the clearance of free FVIII in a VWF-independent manner, in vivo clearance experiments were repeated in dual VWF-/-/FVIII-/- mice. Importantly, the rapid clearance of free FVIII in VWF-/-/FVIII-/- mice was significantly (P=0.012) prolonged in the presence of anti-MGL1/2 antibodies. Finally, endogenous plasma FVIII levels in VWF-/- mice were significantly increased following MGL inhibition (P=0.016). CONCLUSIONS: Cumulatively, these findings demonstrate that MGL plays an important role in regulating macrophage-mediated clearance of both VWF-bound FVIII and free-FVIII in vivo. We propose that this novel FVIII clearance pathway may be of particular clinical importance in patients with type 2N or type 3 Von Willebrand disease.

Suppression of anti-drug antibody formation against coagulation factor VIII by oral delivery of anti-CD3 monoclonal antibody in hemophilia A mice.

Active tolerance to ingested dietary antigens forms the basis for oral immunotherapy to food allergens or autoimmune self-antigens. Alternatively, oral administration of anti-CD3 monoclonal antibody can be effective in modulating systemic immune responses without T cell depletion. Here we assessed the efficacy of full length and the F(ab')2 fragment of oral anti-CD3 to prevent anti-drug antibody (ADA) formation to clotting factor VIII (FVIII) protein replacement therapy in hemophilia A mice. A short course of low dose oral anti-CD3 F(ab')2 reduced the production of neutralizing ADAs, and suppression was significantly enhanced when oral anti-CD3 was timed concurrently with FVIII administration. Tolerance was accompanied by the early induction of FoxP3+LAP-, FoxP3+LAP+, and FoxP3-LAP+ populations of CD4+ T cells in the spleen and mesenteric lymph nodes. FoxP3+LAP+ Tregs expressing CD69, CTLA-4, and PD1 persisted in spleens of treated mice, but did not produce IL-10. Finally, we attempted to combine the anti-CD3 approach with oral intake of FVIII antigen (using our previously established method of using lettuce plant cells transgenic for FVIII antigen fused to cholera toxin B (CTB) subunit, which suppresses ADAs in part through induction of IL-10 producing FoxP3-LAP+ Treg). However, combining these two approaches failed to improve suppression of ADAs. We conclude that oral anti-CD3 treatment is a promising approach to prevention of ADA formation in systemic protein replacement therapy, albeit via mechanisms distinct from and not synergistic with oral intake of bioencapsulated antigen.

Thrombin generation in real life bleeding patients on oral anticoagulants reversed (or not) with (activated) prothrombin complex concentrate.

BACKGROUND: Bleeding during oral anticoagulant therapy is currently codified by expert guidelines. Monitoring of coagulation during bleeding events is challenging. Our study sought to assess thrombin generation assay (TGA) in direct oral anticoagulant-treated patients without bleeding (WB), bleeding without reversal therapy (BR-), and bleeding with reversal therapy (BR+). METHODS: We conducted a prospective, monocentric study from June 2015 to June 2018. For all bleeding groups, TGA was evaluated using platelet-poor plasma collected upon arrival at emergency (T0), and 30 min (T1), 6 h (T2) and 24 h (T3) after reversal therapy (if indicated) following activation by tissue factor 5 pM and phospholipids. RESULTS: Overall, 292 patients participated, including 91 BR+, 94 BR-, and 107 WB patients. At T0, vitamin K antagonist reversed (VKA-BR+) patients experienced a significant decrease in TGA parameters (ETP and peak) compared with VKA without bleeding (VKA-WB). Compared with healthy controls, VKA-BR+ patients reversed by four-factor prothrombin complex concentrate (4F-PCC) displayed comparable TGA 's ETP and peak at T1, T2, and T3, whereas direct anti-Xa BR+ patients reversed by 4F-PCC or activated prothrombin complex concentrate (aPCC) reached thrombin generation parameters that exceeded normal range at T2 and T3. CONCLUSIONS: In VKA-treated patients reversed by 4F-PCC, TGA parameters were normalized, whereas in rivaroxaban or apixaban-treated patients reversed by 4F-PCC or aPCC, TGA parameters exceeded normal range. Further studies are needed to compare the efficacy and safety of a different dose of reversal therapy and the impact on coagulation parameters.

Progranulin deficiency suppresses allergic asthma and enhances efferocytosis via PPAR-γ/MFG-E8 regulation in macrophages.

Efferocytosis can resolve airway inflammation and enhance airway tolerance in allergic asthma. While previous work has reported that progranulin (PGRN) regulated macrophage efferocytosis, but it is unclear whether PGRN-mediated efferocytosis is associated with asthma. Here, we found that in an ovalbumin (OVA)-induced allergic asthma model, the airway inflammation was suppressed and the apoptosis in lung tissues was ameliorated in PGRN-deficient mice. In contrast, PGRN knockdown in human bronchial epithelial cells increased apoptosis in vitro. Furthermore, PGRN-deficient macrophages had significantly stronger efferocytosis ability than wild type (WT) macrophages both in vitro and in vivo. PGRN-deficient peritoneal macrophages (PMs) exhibited increased expression of genes associated with efferocytosis including milk fat globule-epidermal growth factor 8 (MFG-E8), peroxisome proliferator-activated receptor gamma (PPAR-γ) and sirtuin1 (SIRT1) and increased capacity to produce the anti-inflammatory mediator interleukin (IL)-10 during efferocytosis. GW9662, the inhibitor of PPAR-γ, abolished increased efferocytosis and MFG-E8 expression in PGRN-deficient PMs suggesting that PGRN deficiency enhanced MFG-E8-mediated efferocytosis through PPAR-γ. Correspondingly, efferocytosis genes were increased in the lungs of OVA-induced PGRN-deficient mice. GW9662 treatment reduced MFG-E8 expression but did not significantly affect airway inflammation. Our results demonstrated that PGRN deficiency enhanced efferocytosis via the PPAR-γ/MFG-E8 pathway and this may be one of the reasons PGRN deficiency results in inhibition of airway inflammation in allergic asthma.

Cerebellar hematoma in severe hemophilia with inhibitor on emicizumab prophylaxis: a case report.

BACKGROUND: Emicizumab is a novel prophylactic medication used to treat patients with hemophilia A. It is indicated to minimize the frequency of bleeding episodes and the severity of serious bleeding in patients with hemophilia A utilizing inhibitors. However, some cases of bleeding episodes have been reported, and more data are needed regarding their management and expected outcomes. CASE PRESENTATION: We report a case of a 4-year-old Saudi Arabian boy with severe hemophilia A who presented with a post-traumatic cerebral hemorrhage. The patient, with high titer inhibitors, was on emicizumab prophylaxis therapy. On hospital admission, he received tranexamic acid (10 mg intravenously, every 6 hours), and recombinant activated factor VII 120 µg/kg every 2 hours for 2 days then every 4 hours for 4 days. On follow-up, the patient showed no signs of neurological deficit. There was no need for emergency neurosurgical intervention since the bleeding had been controlled throughout the first 2 days. There were no recorded thrombotic sequelae or neurological complications, with complete resolution within 10 days. CONCLUSIONS: This case implies that low-dose recombinant activated factor VII might be used safely and effectively with patients with hemophilia A on emicizumab prophylaxis, to reduce the risk of cerebral hemorrhage or another episode of serious bleeding along with its long-term complications.

Activated 4-Factor Prothrombin Complex Concentrate as a Hemostatic Adjunct for Neonatal Cardiac Surgery: A Propensity Score-Matched Cohort Study.

BACKGROUND: Prothrombin complex concentrates are an emerging "off-label" therapy to augment hemostasis after cardiopulmonary bypass (CPB), but data supporting their use for neonatal cardiac surgery are limited. METHODS: We retrospectively reviewed neonates undergoing open heart surgery with first-time sternotomy between May 2014 and December 2018 from a hospital electronic health record database. Neonates who received activated 4-factor prothrombin complex concentrate (a4FPCC) after CPB were propensity score matched (PSM) to neonates who did not receive a4FPCC (control group). The primary efficacy outcome was total volume (mL/kg) of blood products transfused after CPB, including the first 24 hours on the cardiovascular intensive care unit (CVICU). The primary safety outcome was the incidence of 7- and 30-day postoperative thromboembolism. Secondary outcomes included 24 hours postoperative chest tube output, time to extubation, duration of CVICU stay, duration of hospital stay, 30-day mortality, and incidence of acute kidney injury on postoperative day 3. We used linear regression modeling on PSM data for the primary efficacy outcome. For the primary safety outcome, we tested for differences using McNemar test on PSM data. For secondary outcomes, we used linear regression, Fisher exact test, or survival analyses as appropriate, with false discovery rate-adjusted P values. RESULTS: A total of 165 neonates were included in the final data analysis: 86 in the control group and 79 in the a4FPCC group. After PSM, there were 43 patients in the control group and 43 in the a4FPCC group. We found a statistically significant difference in mean total blood products transfused for the a4FPCC group (47.5 mL/kg) compared with the control group (63.7 mL/kg) for PSM patients (adjusted difference, 15.3; 95% CI, 29.4-1.3; P = .032). We did not find a statistically significant difference in 7- or 30-day thromboembolic rate, postoperative chest tube output, time to extubation, incidence of postoperative acute kidney injury (AKI), or 30-day mortality between the groups. The a4FPCC group had a significantly longer length of intensive care unit stay (32.9 vs 13.3 days; adjusted P = .049) and hospital stay (44.6 vs 24.1 days; adjusted P = .049) compared with the control group. CONCLUSIONS: We found that the use of a4FPCC as a hemostatic adjunct for post-CPB bleeding in neonatal cardiac surgery was associated with a decrease in mean total blood products transfused after CPB without an increased rate of 7- or 30-day postoperative thromboembolism. Our findings suggest that a4FPCCs can be considered as part of a hemostasis pathway for refractory bleeding in neonatal cardiac surgery.

[Acquired hemophilia A that developed after BNT162b2 mRNA COVID-19 vaccination and worsened following re-vaccination].

An 86-year-old Japanese male patient visited a nearby hospital with painful swelling in his left upper and lower limbs 35 days after the second dose of the BNT162b2 mRNA coronavirus disease-2019 (COVID-19) vaccine. He was referred to our hematological department due to a prolonged activated partial thromboplastin time and was urgently admitted. He was diagnosed with acquired hemophilia A (AHA) based on factor VIII (FVIII) activity of 1.7%, FVIII inhibitor of 152.3 BU/ml, and FVIII-binding antibodies detected by enzyme-linked immunosorbent assay. Immunosuppressive therapy with prednisolone (PSL) at 0.5 mg/kg/day was started owing to the risk of infection due to old age and poor activities of daily living. Hemostasis treatment with bypass hemostatic preparations (rFVIIa preparation, FVIIa/FX) was administered for each bleeding event, such as intramuscular and knee joint bleeding, resulting in good hemostatic effects. Coagulative complete remission was achieved on day 69 with PSL treatment; however, FVIII activity decreased with PSL tapering. AHA relapse with rectus abdominis muscle hematoma was observed after the third vaccination. This is the first Japanese report of AHA after COVID-19 vaccination and the world's first case, in which the presence of anti-FVIII-binding antibodies were observed.

Decrease in in vivo coagulant potential of emicizumab in a patient with hemophilia A and inhibitor complicated with infectious mononucleosis.

Emicizumab prophylaxis significantly reduces bleeding episodes in patients with hemophilia A (PwHA). There is little information on coagulant potentials in emicizumab-treated PwHA with infection, however. We encountered an emicizumab-treated PwHA with inhibitor, complicated with Epstein-Barr virus-associated infectious mononucleosis (IM) in phase 1/2 study (ACE001JP/ACE002JP). Although it was a typical clinical course of IM, activated partial thromboplastin time was mildly prolonged but rotational thromboelastometry revealed severely impaired coagulant potential. The blood concentration of emicizumab decreased moderately in the low concentration range, resulting in an increased risk of bleeding and possibly leading to severe ileocecal bleeds requiring coil embolization. The blood concentrations of factors IX/X little decreased and antiemicizumab antibodies did not develop, however. After the influence by IM resolved, his coagulant potentials gradually recovered with the recovery of emicizumab concentration, and parameters by global coagulation assays improved. An IM case for emicizumab-treated PwHA may need to monitor using global coagulation assays.