Activated prothrombin complex concentrate (APCC)-mediated activation of factor (F)VIII in mixtures of FVIII and APCC enhances hemostatic effectiveness.

BACKGROUND AND OBJECTIVES: Activated prothrombin complex concentrates (APCCs), utilized in bypassing therapy for hemophiliacs with inhibitor, contain factors (Fs) VII, FII, FIX and FX, and their active forms. A recent report has demonstrated that mixtures of APCC and FVIII potentiated thrombin generation, in vitro, in plasma from patients with severe hemophilia A, but the mechanism(s) involved remains unknown. RESULTS: APCC (0.05 U mL(-1) ) increased FVIII activity ~ 4-fold within 1 min in one-stage clotting assays, followed by a return to initial levels within 10 min. This reaction was dependent on the presence of tissue factor and phospholipid. Thrombin generation produced from APCC was ~ 3.5-fold greater in the presence of FVIII than that in its absence. SDS-PAGE analysis revealed that APCC sequentially proteolyzed the heavy chain of FVIII at Arg(372) and Arg(740) , followed by cleavage at Arg(336) . Proteolysis was prevented by FVIIa inhibitor, but not by hirudin, supporting the concept that APCC itself possessed the potential to activate FVIII in early coagulation phases, and that FVIIa in APCC contributed mainly to this reaction. APCC-mediated FVIII activation was unaffected by the addition of anti-FVIII inhibitor antibodies, irrespective of epitope specificity. Anti-C2 type 1 inhibitors, however, diminished the inactivation phase of the APCC reaction by inhibiting cleavage at Arg(336) . CONCLUSION: Small amounts of APCC, relative to the standard concentration used for clinical purposes, could activate FVIII directly, even in the presence of anti-FVIII antibodies. Combination therapy based on mixtures of APCC and FVIII could have significant beneficial implications for the treatment of hemophilia A patients with inhibitors.博士（医学）・甲第601号・平成25年7月22日発行元の猶予期間終了の後、本文を登録予定（2014.05

後天性血友病A (抗C2 自己抗体)の凝固機能低下におけるFX 複合体阻害様式の解明

Acquired haemophilia A (AHA) is caused by the development of factor (F)VIII autoantibodies, demonstrating type 1 or type 2 inhibitory behaviour, and results in more serious haemorrhagic symptoms than in congenital severe HA. The reason(s) for this remains unknown, however. The global coagulation assays, thrombin generation tests and clot waveform analysis, demonstrated that coagulation parameters in patients with AHA-type 2 inhibitor were more significantly depressed than those in patients with moderate HA with similar FVIII activities. Thrombin and intrinsic FXa generation tests were significantly depressed in AHA-type 1 and AHA-type 2 compared to severe HA, and more defective in AHA-type 1 than in AHA-type 2. To investigate these inhibitory mechanism(s), anti-FVIII autoantibodies were purified from AHA plasmas. AHA-type 1 autoantibodies, containing an anti-C2 ESH4-epitope, blocked FVIII(a)-phospholipid binding, whilst AHA-type 2, containing an anti-C2 ESH8-epitope, inhibited thrombin-catalysed FVIII activation. The coagulation function in a reconstituted AHA-model containing exogenous ESH4 or ESH8 was more abnormal than in severe HA. The addition of anti-FIX antibody to FVIII-deficient plasma resulted in lower coagulation function than its absence. These results support the concept that global coagulation might be more suppressed in AHA than in severe HA due to the inhibition of FIXa-dependent FX activation by steric hindrance in the presence of FVIII-anti-C2 autoantibodies. Additionally, AHA-type 1 inhibitors prevented FVIIIa-phospholipid binding, essential for the tenase complex, whilst AHA-type 2 antibodies decreased FXa generation by inhibiting thrombin-catalysed FVIII activation. These two distinct mechanisms might, in part, contribute to and exacerbate the serious haemorrhagic symptoms in AHA.博士（医学）・乙第1298号・平成24年5月28日© Schattauer Publishers, Stuttgart, 201

Activated partial thromboplastin time‑based clot waveform analysis enables measurement of very low levels of factor IX activity in patients with severe hemophilia B

The precise measurement of very low levels of factor IX activity (FIX:C < 1 IU/dL) is essential for understanding clinical severity and risk of inhibitor development in patients with severe hemophilia B (Pw-SHB). However, such measurement sensitivity has not yet been achieved. We aimed to establish a measurement method using clot waveform analysis (CWA). Residual FIX:C by adding anti-FIX monoclonal antibody, FIX:C by adding recombinant (r)FIX to the commercial Pw-SHB plasmas, and FIX:C in our Pw-SHB were determined by CS-2000i™/CS-2400™, followed by analysis of CWA parameters. The presence of anti-FIX antibody in the commercial Pw-SHB plasmas significantly decreased coagulation potential compared to its absence. The addition of rFIX to these innate plasma samples produced significant changes in three parameters upon adding FIX:C at 0.1–1 IU/dL, supporting the presence of trace FIX:C in Pw-SHB. Therefore, appropriate FIX-depleted plasma containing minimum residual FIX:C was chosen from reference curves of FIX:C (0.01–1 IU/dL). Among patients with untreated Pw-SHB, two had FIX:C 0.6–0.7 IU/dL and two had lower than detectable levels using FIX-depleted plasma. One of the latter had detectable trough levels post-rFIX administration. In conclusion, CWA enabled measurement of very low levels of FIX:C using appropriate FIX-deficient plasma.博士（医学）・乙第1528号・令和4年12月22

第IX(a)因子および第X因子に対する二重特異性抗体であるエミシズマブはin vitroで第XI因子欠乏血漿における凝固機能を増強する

Essentials Emicizumab mimics factor (F)VIIIa cofactor function, augments the intrinsic tenase activity. We assessed the emicizumab-driven hemostatic function in FXI-deficient plasmas. Emicizumab improved the coagulation potentials in severe FXI-deficient plasma. Emicizumab may provide a possibility for clinical application in patients with FXI deficiency. SUMMARY: Background Patients with factor (F)XI deficiency commonly present with markedly prolonged activated partial thromboplastin times (APTT), although bleeding phenotypes are heterogeneous. Emicizumab, a bispecific monoclonal antibody to FIX/FIXa and FX/FXa, mimics FVIIIa cofactor function on phospholipid (PL) surfaces. Antibody reactions were designed, therefore, to augment mechanisms during the propagation phase of blood coagulation. Aim To assess emicizumab-driven hemostatic function in FXI-deficient plasmas. Methods and Results Standard ellagic acid (Elg)/PL-based APTTs of different FXI-deficient plasmas (n = 13; FXI activity, < 1 IU dl-1 ) were markedly shortened dose dependently by the presence of emicizumab. To further analyze the effects of emicizumab, clot waveform analysis (CWA) in FXI-deficient plasmas with emicizumab, triggered by tissue factor (TF)/Elg demonstrated improvements in both clot times, reflecting the initiation phase, and coagulation velocity, which represents the propagation phase. Emicizumab also enhanced the TF/Elg-triggered thrombin generation in FXI-deficient plasmas dose-dependently although the degree of enhancement varied in individual cases. Thrombin generation with either FVII-deficient plasma or FIX-deficient plasma treated with anti-FXI antibody showed little or no increase by the co-presence of emicizumab, suggesting that the accelerated thrombin generation in FXI-deficient plasmas by emicizumab should depend on the FIXa-involved coagulation propagation initially triggered by FVIIa/TF. The ex vivo addition of emicizumab to whole blood from three patients with severe FXI deficiency demonstrated modest, dose-dependent improvements in Ca2+ -triggered thromboelastograms (NATEM mode). Conclusion Emicizumab appeared to improve coagulation function in severe FXI-deficient plasma, and might provide possibilities for clinical application in patients with FXI deficiency.博士（医学）・乙第1427号・平成31年3月15日© 2018 International Society on Thrombosis and HaemostasisThis is the pre-peer reviewed version of the following article: [https://onlinelibrary.wiley.com/doi/full/10.1111/jth.14334], which has been published in final form at [http://dx.doi.org/10.1111/jth.14334]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions

組織因子惹起-トロンボモジュリン添加凝固波形解析を用いたプロテインC経路異常を伴う血栓性素因のスクリーニング法

Objectives: Absolute or relative protein (P)C pathway abnormalities (PC deficiency, PS deficiency, antiphospholipid syndrome (APS), factor (F)V-abnormality, and high FVIII level) cause thrombophilia. Although screening assays for these thrombophilias are available, one utilizing clot waveform analysis (CWA) remains unknown. We aimed to establish a CWA-based screening assay to distinguish PC pathway abnormality-related thrombophilia. Methods: Samples were reacted with tissue factor (TF)/phospholipids and recombinant thrombomodulin (rTM; optimal 20 nM), followed by CWA measurement. The peak ratio (with/without rTM) of the first derivative curve of clot waveform was calculated. Results: The peak ratio in healthy plasmas (n = 35) was 0.36 ± 0.13; hence, the cutoff value was set to 0.49. The peak ratios in plasmas with PC deficiency, PS deficiency, high-FVIII (spiked 300 IU/dl), and APS were higher than the cutoff values (0.79/0.97/0.50/0.93, respectively). PC-deficient plasma or PS-deficient plasma mixed with normal plasma (25%/50%/75%/100% PC or PS level) showed dose-dependent decreases in the peak ratios (PC deficient: 0.85/0.64/0.44/0.28; PS deficient: 0.69/0.53/0.40/0.25), suggesting that the peak ratio at ≤50% of PC or PS level exceeded the cutoff value. The peak ratio in FV deficiency with FV ≤25% was higher than the cutoff value. FV-deficient plasma spiked with 40 IU/dl rFV-R506Q (FVLeiden ) or rFV-W1920R (FVNara ) showed >90% peak ratios. Conclusions: rTM-mediated TF-triggered CWA might be useful for screening PC pathway abnormality-related thrombophilia.博士（医学）・乙第1527号・令和4年9月28日© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.This is the peer reviewed version of the following article: [https://onlinelibrary.wiley.com/doi/10.1111/ejh.13777], which has been published in final form at [https://doi.org/10.1111/ejh.13777]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.発行元が定める登録猶予期間終了の後、本文を登録予定（2023.07

エミシズマブは凝固第VIII因子と同様にフィブリン構造およびその安定性を向上させる

Introduction: Emicizumab is an antifactor (F)IXa/FX bispecific antibody, mimicking FVIIIa cofactor function. Emi prophylaxis effectively reduces bleeding events in patients with haemophilia A. The physical properties of emicizumab-induced fibrin clots remain to be investigated, however. Aim: We have investigated the stability and structure of emicizumab-induced fibrin clots. Methods: Coagulation was initiated by activated partial thromboplastin time (aPTT) trigger and prothrombin time (PT)/aPTT-mixed trigger in FVIII-deficient plasma with various concentrations of emicizumab or recombinant FVIII. The turbidity and stability of fibrin clots were assessed by clot waveform and clot-fibrinolysis waveform analyses, respectively. The resulting fibrin was analysed by scanning electron microscopy (SEM). Results: Using an aPTT trigger, the turbidity was decreased and the fibrinolysis times were prolonged in the presence of emicizumab dose-dependently. Scanning electron microscopy imaging demonstrated that emicizumab improved the structure of fibrin network with thinner fibres than in its absence. Although emicizumab shortened the aPTT dramatically, the nature of emicizumab-induced fibrin clots did not reflect the hypercoagulable state. Similarly, using a PT/aPTT-mixed trigger that could evaluate potential emicizumab activity, emicizumab improved the stability and structure of fibrin clot in a series of experiments. In this circumstance, fibrin clot properties with emicizumab at 50 and 100 µg/mL appeared to be comparable to those with FVIII at ~12 and ~24-32 IU/dL, respectively. Conclusion: Emicizumab effectively improved fibrin clot stability and structure in FVIII-deficient plasma, and the physical properties of emicizumab-induced fibrin clots were similar to those with FVIII.博士（医学）・甲第787号・令和3年3月15日© 2020 John Wiley & Sons Ltd.This is the peer reviewed version of the following article: https://onlinelibrary.wiley.com/doi/10.1111/hae.13961, which has been published in final form at https://doi.org/10.1111/hae.13961. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions

The common VWF single nucleotide variants c.2365A>G and c.2385T>C modify VWF biosynthesis and clearance

Plasma levels of von Willebrand factor (VWF) vary considerably in the general population and this variation has been linked to several genetic and environmental factors. Genetic factors include 2 common single nucleotide variants (SNVs) located in VWF, rs1063856 (c.2365A>G) and rs1063857 (c.2385T>C), although to date the mechanistic basis for their association with VWF level is unknown. Using genotypic/phenotypic information from a European healthy control population, in vitro analyses of recombinant VWF expressing both SNVs, and in vivo murine models, this study determined the precise nature of their association with VWF level and investigated the mechanism(s) involved. Possession of either SNV corresponded with a significant increase in plasma VWF in healthy controls (P G on VWF levels was also confirmed in vivo. This increase in VWF protein corresponded to an increase in VWF messenger RNA (mRNA) resulting, in part, from prolonged mRNA half-life. In addition, coinheritance of both SNVs was associated with a lower VWF propeptide-to-VWF antigen ratio in healthy controls (P < .05) and a longer VWF half-life in VWF knockout mice (P < .0001). Both SNVs therefore directly increase VWF plasma levels through a combined influence on VWF biosynthesis and clearance, and may have an impact on disease phenotype in both hemostatic and thrombotic disorders

ROTEMを用いた小児特発性ネフローゼ症候群患者の急性期における包括的全血凝固線溶能

Background: Venous thromboembolism is a rare, serious complication of idiopathic nephrotic syndrome (INS) in childhood. The mechanisms responsible for the hypercoagulable state in the acute phase of INS are poorly understood, however. This study aimed to assess overall coagulation and fibrinolytic function in pediatric patients with INS. Methods: Global coagulation and fibrinolysis were examined in whole blood samples from 22 children with initial onset INS (initial-group), 22 children with relapsed INS (relapse-group), and 15 control pediatric patients using rotational thromboelastometry (ROTEM®). In the initial-group, blood samples were obtained before (week 0) and 1-4 weeks after initiation of corticosteroid therapy. EXTEM and FIBTEM were used to assess coagulation and fibrinolysis, respectively. Clot time (CT), clot formation time (CFT), maximum clot firmness (MCF), and α-angle were determined as coagulation parameters, and lysis index at 30 and 60 min (LI30 and LI60, respectively) were assessed as fibrinolytic parameters. Results: CT was significantly shortened, and MCF and α-angle were significantly greater than controls at week 0 and week 1 both in the initial-group and the relapse-group. MCF correlated with serum albumin (r = 0.70, p < 0.001) and fibrinogen level (r = 0.68, p < 0.001). The fibrinolytic parameters (LI30 and LI60) in the initial-group were stable and higher than those in controls at all time points (p < 0.01). Conclusions: We have shown that the hypofibrinolytic defect did not improve with effective NS treatment at the early 4-week time-point. Additionally, a likely pre-thrombotic state was evident in the period before initial onset and 1 week after corticosteroid therapy in pediatric INS.博士（医学）・乙第1522号・令和4年3月15日© 2021. The Author(s), under exclusive licence to International Pediatric Nephrology Association.This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s00467-021-05366-4.発行元が定める登録猶予期間終了の後、本文を登録予定（2023.01

凝固初期相における活性型凝固第Ⅶ因子/組織因子依存性の活性型凝固第Ⅹ因子生成に対する活性型凝固第Ⅷ因子の働き

Factor VIIa/tissue factor (FVIIa/TF) initiates blood coagulation by promoting FXa generation (extrinsic-Xa). Subsequent generation of intrinsic FXa (intrinsic-Xa) amplifies thrombin formation. Previous studies suggested that FVIIa/TF activates FVIII rapidly in immediate coagulation reactions, and FVIIa/TF/FXa activates FVIII prior to thrombin-dependent feedback. We investigated FVIII/FVIIa/TF/FXa relationships in early coagulation mechanisms. Total FXa generated by FVIIa/TF and FVIIa/TF-activated FVIII (FVIIIaVIIa/TF) was 22.6 ± 1.7 nM (1 min); total FXa with FVIIa-inhibitor was 3.4 ± 0.7 nM, whereas FXa generated by FVIIa/TF or FVIII/TF was 10.4 ± 1.1 or 0.74 ± 0.14 nM, respectively. Little Xa was generated by FVIII alone, suggesting that intrinsic-Xa mechanisms were mediated by FVIIIaVIIa/TF and FVIII/TF in the initiation phase. Intrinsic-Xa was delayed somewhat by von Willebrand factor (VWF). FVIII activation by FXa with FVIIa/TF was comparable to activation with Glu-Gly-Arg-inactivated-FVIIa/TF. TF counteracted the inhibitory effects of VWF on FXa-induced FVIII activation mediated by Arg372 cleavage. The FVIII-C2 domain bound to cytoplasmic domain-deleted TF (TF¹⁻²⁴³), and VWF blocked this binding by > 80%, indicating an overlap between VWF- and TF1-243-binding site(s) on C2. Overall, these data suggest that FVIII-associated intrinsic-Xa, governed by both FVIIa/TF-induced and FXa-induced FVIII activation mediated by FVIII-TF interactions, together with FVIIa-dependent extrinsic-Xa mechanisms, may be central to the initiation phase of coagulation.博士（医学）・乙第1429号・令和元年6月26日© Japanese Society of Hematology 2019This is a post-peer-review, pre-copyedit version of an article published in International journal of hematology. The final authenticated version is available online at: http://dx.doi.org/10.1007/s12185-019-02611-3