The Japanese Immune Tolerance Induction (J-ITI) study in haemophilia patients with inhibitor: Outcomes and successful predictors of ITI treatment.

INTRODUCTION: Immune tolerance induction (ITI) was the primary therapeutic approach to eradicate inhibitors in haemophilia patients. Several large ITI registries had been reported, but successful predictors of ITI outcome are still debated. No reports are available on large ITI studies in non-caucasian countries. AIM: We designed a retrospective cohort study of ITI in Japanese haemophilia patients with inhibitor. METHODS: Retrospective data were collected from 155 haemophilia (H)A (140 severe-type) and 7 HB (7 severe-type) patients treated at 45 institutions. ITI outcome was centrally reviewed. We defined "success" as undetectable inhibitor after 2 consecutive measurements. RESULTS: The ITI success rate was 71.2% for HA and 83.3% for HB. Cumulated success rates for HA achieving 50% and 75% were 0.7 and 2 years after treatment, respectively. Significant successful predictors in HA were low-responding inhibitors compared to high-responding inhibitors, shorter time to the start of ITI, and lower historical and treatment peak titres of inhibitor. Dose regimen (high dose; ≥90 IU/kg every day, low dose; ≤75 IU/kg, 3 d/wk) and the type of therapeutic product did not affect outcomes. The success rate of salvage ITI using von Willebrand factor-containing factor VIII was 50% (n = 6/12), and patient age at the start of salvage ITI was a significant predictor. The inhibitor recurred in 6 HA cases (3.9%). CONCLUSION: The results provided potentially important information for improving future success rates for ITI in inhibitor patients.

Role of red blood cells in the anemia-associated bleeding under high shear conditions.

BACKGROUND: Red blood cells (RBCs) contribute to hemostasis under blood-flow, and anemia might contribute to a hemorrhagic diathesis. The majority of current laboratory techniques to assess hemostasis do not consider the effects of RBCs. An assay to determine the role of RBCs in hemostasis could be beneficial for clinical management. OBJECTIVES: To investigate the influence of RBCs in hemostasis. METHODS: Hemostasis was investigated using a novel microchip flow-chamber system (T-TAS® ) in an anemic patient with von Willebrand disease. Subsequently, the effects of RBCs in total thrombus analysis system (T-TAS) were examined using reconstituted whole blood at various hematocrit levels. RESULTS: In vivo: When the patient was anemic and demonstrated persisted hemorrhagic symptoms despite the maintained adequate von Willebrand factor ristocetin cofactor activity levels, thrombus formation determined by T-TAS was delayed. However, transfusions of RBCs resolved bleeding symptom and, accordingly, the thrombus formation in T-TAS improved. In vitro: Thrombus formation determined by T-TAS at 1000 s-1 was dose-dependent on hematocrit (the time to reach 10 kPa (T10 ): 10.0 ± 0, 9.5 ± 1.4, 6.7 ± 2.4, 2.8 ± 1.6 min at hematocrits of 0%, 12.5%, 25% and 50%, respectively). Markedly defective thrombus formation (T10 >10 min) was confirmed at a hematocrit <25% at 2000 s-1 . CONCLUSION: Red blood cells play an essential role in hemostasis under high shear, and RBC transfusions could be effective for refractory bleeding in patients with anemia. T-TAS measurements appear to reflect the hemostatic consequences of diminished red cell numbers under blood-flow, and could provide a valuable means for monitoring patients.

Clot waveform analysis using CS-2000i™ distinguishes between very low and absent levels of factor VIII activity in patients with severe haemophilia A.

INTRODUCTION: A recently developed method to assess comprehensive coagulation function, clot waveform analysis (CWA), accurately detect low levels (<1 IU/dL) of factor VIII activity (FVIII:C) in haemophilia A patients (HA-pts). Improvements are needed, however, to differentiate patients with very low from absent levels of FVIII:C. AIM: We attempted to optimize CWA using the coagulation analyser CS-2000i™ to distinguish between very low levels and absent FVIII:C in severe HA-pts. METHODS AND RESULTS: Activated partial thrombin time (aPTT)-based clot waveforms were determined in FVIII-deficient plasmas mixed with various amounts of recombinant FVIII. Clot times (CT) were shortened, and maximum coagulation velocity (|min1|) and acceleration (|min2|) were increased in FVIII dose-dependently at levels ranging from 0.25 to 100 IU/dL. The lowest level of FVIII:C detected was 0.25 IU/dL. Plasma samples from modestly severe (MS-HA; 0.5-<1.0 IU/dL), very severe (VS-HA; 0.25-<0.5 IU/dL), extremely severe (ES-HA; <0.25 IU/dL) and inhibitor-positive HA-pts (HA-inh) were examined. The CT was markedly prolonged in all instances but showed significant differences between the different groups insufficiently. The |min1| and |min2| in HA-inh were lower compared to the other groups (P<.05). A new parameter (slope-|min1|) reflecting average coagulation acceleration was derived. This index (median) was lower in HA-inh (0.0042) compared to ES-HA (0.0068) and VS-HA (0.011) with greater significant differences (P<.01), and an index of <.005 reflected the total absence of FVIII in the presence of inhibitor. CONCLUSION: The slope-|min1| parameter could provide a useful index for evaluating very low and absent levels of FVIII and/or the development of FVIII inhibitor in HA-pts.

A phase III clinical trial of a mixture agent of plasma-derived factor VIIa and factor X (MC710) in haemophilia patients with inhibitors.

INTRODUCTION: MC710, a 1:10 protein weight ratio mixture of plasma-derived activated factor VII (FVIIa) and factor X (FX), is a novel bypassing agent for haemostasis in haemophilia patients with inhibitors. We evaluated the haemostatic efficacy and safety of one to two administrations of MC710 in 21 joint, muscle, and subcutaneous bleeding episodes in 14 male patients, in a multi-centre, open-label, non-randomized clinical trial. METHODS: Subjects were intravenously administered one or two doses of 60 or 120 µg kg-1 MC710 (as FVIIa) once or twice (to a maximum of 180 µg kg-1 ) over up to five bleeding episodes per subject. The haemostatic efficacy of MC710 was determined for each episode by investigator evaluation, using changes in visual analogue scale (VAS) for pain relief, and/or knee joint or muscle circumference for swelling reduction, and range of motion (ROM) for improvement of joint mobility. RESULTS: In 21 treatments for bleeding episodes, 19 were rated "excellent" or "effective" 8 h after the last treatment. VAS significantly decreased over time, and ROM significantly improved over time compared with the values before treatment. One mild adverse reaction, decreased blood potassium, and two serious adverse events, both knee joint bleeding, were observed within 1 week after first administration, with no significant effect on safety. Furthermore, diagnostic markers did not show any signs of disseminated intravascular coagulation (DIC). CONCLUSION: These results show that MC710 has sufficient haemostatic efficacy and safety, and can be used as a potential bypassing agent to control bleeding in haemophilia patients with inhibitors.

Comprehensive evaluation of haemostatic function in von Willebrand disease patients using a microchip-based flow chamber system.

The diagnosis of von Willebrand disease (VWD) is difficult due to the wide spectrum of clinical phenotypes associated with this disorder. We have analysed and characterized haemostatic function in VWD patients using a microchip-based flow chamber system. Microchips coated with either collagen [platelet (PL)-chip] or collagen/thromboplastin [atherome (AR)-chip] were used to evaluate platelet thrombus formation at 1000 s(-1) and fibrin-rich platelet thrombus formation at 240 s(-1) respectively. Blood samples from an asymptomatic patient with VWD type 1 [von Willebrand factor (VWF): RCo 3.2%; bleeding score (BS 2] displayed normal thrombus formation in both PL- and AR-chips, whereas blood from a symptomatic type 1 patient (VWF: RCo 14%, BS 9) had significantly delayed capillary occlusion. Nearly complete suppression of the flow pressure increase was observed in symptomatic patients with VWD type 2A (BS 13) and 2N (BS 27), whereas no flow pressure was found for the type 3 patient (BS 6). Fibrin-rich platelet thrombus formation was only weakly increased by the in vitro addition of factor VIII (FVIII) to blood samples from the type 3 patient, but was normalized by the addition of VWF/FVIII. The in vivo effects of treatment with desmopressin or VWF/FVIII for the symptomatic patients were analysed using two types of microchips. The PL-chip was highly sensitive for patients' VWF-mediated platelet functions, whereas the AR-chip allowed assessment of overall haemostatic ability, including sensitivity to both VWF and FVIII. The combined analysis with PL- and AR-chips may be potentially useful for the diagnosis of VWD based on clinical phenotypes, and for monitoring drug effects.

Occlusal-supporting ability of individual maxillary and mandibular teeth.

This study aimed to analyse occlusal force, area and pressure for individual maxillary and mandibular teeth by assessing their occlusal-supporting abilities. Ninety-nine subjects (49 men and 50 women; average age, 24·7 ± 3·4 years; range, 20-37 years) performed maximal voluntary clenching twice for 3 s in both the intercuspal position and the intercuspal position with sliding movement from edge-to-edge occlusion, with a pressure-sensitive sheet placed between the maxillary and mandibular dental arch. Occlusal force, area and pressure of individual teeth were calculated by colour development in the pressure-sensitive sheet with special analytical equipment and software. Occlusal contact condition of individual teeth was confirmed using the intra-occlusal record. All data were analysed using unpaired Student's t-test, Kruskal-Wallis test and Scheffe's test for multiple comparisons with a significance level of P < 0·05. The occlusal pressure in the intercuspal position with sliding movement from edge-to-edge occlusion was adopted as the representative occlusal-supporting ability for each individual tooth, although there were, in part, statistically significant differences in the effects of laterality, performance and gender. Overall, the occlusal pressure increased gradually from the central incisor, peaked at the canine or first premolar and decreased sharply-and significantly (P < 0·01)-towards the second molar. We conclude that the occlusal pressure of individual teeth can be used as an indicator of occlusal-supporting ability. This is therefore proposed as a possible suitable parameter for epidemiologic research, specifically for verifying the relationship between occlusal-supporting ability and status of residual periodontal ligament support.

Emicizumab, the bispecific antibody to factors IX/IXa and X/Xa, potentiates coagulation function in factor XI-deficient plasma in vitro.

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.

Common themes and challenges in hemophilia care: a multinational perspective.

OBJECTIVE: To identify ways that provision of hemophilia care can be maximized at the local level, irrespective of available resources or cultural or geographic challenges. METHODS: The SHIELD group used its multinational experience to share examples of local initiatives that have been employed to deliver optimal hemophilia care. RESULTS: The examples were reviewed and categorized into four key themes: guidelines and algorithms for delivery of care; collaboration with patients and allied groups for care and education; registries for the monitoring of treatment and outcomes and health care planning and delivery; and opportunities for personalization of care. These themes were then incorporated into a road map for collaborative care in hemophilia that reflected the contribution of best practice. DISCUSSION: Differing healthcare reimbursement systems, budgetary constraints, and geographical and cultural factors make it difficult for any country to fully deliver ideal care for people with hemophilia. The SHIELD approach for collaborative care provides illustrative examples of how four key themes can be used to optimize hemophilia care in any setting. ABBREVIATIONS: AHCDC: Association of Hemophilia Clinic Directors of Canada; AICE: Italian Association of Hemophilia Centres; ATHN: American Thrombosis and Hemostasis Network; EAHAD: European Association for Haemophilia and Allied Disorders; EHC: European Hemophilia Consortium; FIX: Coagulation Factor IX; FVIII: Coagulation Factor VIII; HAL: Haemophilia Activity List; HJHS: Haemophilia Joint Health Score; HTC: Hemophilia Treatment Centre; HTCCNC: Hemophilia Treatment Centre Collaborative Network of China; MASAC: Medical and Scientific Advisory Council; MDT: Multidisciplinary team; NHD: National Haemophilia Database; NHF: National Hemophilia Foundation; PK: Pharmacokinetics; POCUS: Point of care ultrasound; PWH: People with haemophilia; SHIELD: Supporting Hemophilia through International Education, Learning and Development; WFH: World Federation of Hemophilia.

Routine measurements of factor VIII activity and inhibitor titer in the presence of emicizumab utilizing anti-idiotype monoclonal antibodies.

Essentials Emicizumab (Emi) affects the APTT-based assays of factor (F)VIII activity and inhibitor titer. A mixture of two anti-Emi monoclonal antibodies (mAb) effectively neutralized the Emi activity. Anti-Emi mAbs completely eliminated the influence of Emi on FVIII activity and inhibitor titer. The inclusion of anti-Emi mAbs in routine FVIII assays would be useful for Emi-treated patients. SUMMARY: Background Emicizumab is an anti-factor (F)IXa/X bispecific monoclonal antibody (mAb), mimicking the factor (F)VIIIa cofactor activity. Emicizumab does not require activation by thrombin and its shortening effect on the activated partial prothrombin time (APTT) is more pronounced than that of factor (F)VIII. APTT-based FVIII activity (FVIII:C) and FVIII inhibiter titer measurements are influenced by the presence of emicizumab. Aim To establish a reliable APTT-based assay to measure FVIII in the presence of emicizumab. Methods Plasmas from hemophilia A (HA) patients without or with inhibitors were studied using one-stage FVIII:C and Bethesda inhibitor assays. Two recombinant anti-idiotype mAbs to emicizumab (anti-emicizumab mAbs) were prepared, rcAQ8 to anti-FIXa-Fab and rcAJ540 to anti-FX-Fab. Results The combined anti-idiotype mAbs (2000 nm each) eliminated the effects of emicizumab on APTTs of HA plasmas without or with inhibitor by competitive inhibition of antibody binding to FIX(a)/FX(a). Measurements of FVIII coagulation activity in HA plasmas without inhibitor were overestimated in the presence of emicizumab (1 µm = ~150 µg mL-1 ) at all reference levels of FVIII. The addition of anti-emicizumab mAbs to the assay mixtures completely neutralized the emicizumab and facilitated accurate determination of FVIII:C. Anti-FVIII inhibitor titers were undetectable in the presence of emicizumab in HA plasmas with inhibitor or normal plasmas mixed with anti-FVIII neutralizing antibodies. These effects of emicizumab were completely counteracted by the addition of the anti-idiotype mAbs, allowing accurate assessment of inhibitor titers. Conclusion The in vitro inclusion of anti-emicizumab mAbs in the standard one-stage coagulation assays prevented interference by emicizumab and enabled accurate measurements of FVIII:C and inhibitor titers.

Modified clot waveform analysis to measure plasma coagulation potential in the presence of the anti-factor IXa/factor X bispecific antibody emicizumab.

Essentials The activated partial prothrombin time (aPTT) cannot predict the activity of emicizumab (Emi). Adjusted clot waveform analyses using a prothrombin time (PT)/aPTT initiator were developed. Activity of Emi in the co-presence of factor VIII or bypassing agents was quantified. This assay is useful for assessing coagulation potential in Emi-treated hemophilia A. SUMMARY: Background Emicizumab is an anti-activated factor IX/FX bispecific antibody that mimics activated FVIII cofactor function. Emicizumab does not require activation by thrombin, and its effect on shortening the activated partial thromboplastin time (APTT) is much greater than that of FVIII. Therefore, the APTT has limited utility in hemophilia A (HA) patients treated with emicizumab. Aim To evaluate the global coagulation potential of emicizumab. Methods Clot waveform analysis (CWA) with prothrombin time (PT)/APTT mixed reagents was used to define hemostatic monitoring protocols in HA patients. A modified parameter, adjusted-|min1| (Ad|min1|), was developed. Maximum and minimum percentage transmittance were defined as 100% and 0% in the precoagulation and postcoagulation phases, respectively. Ad|min1| was calculated as an index of the maximum velocity of the coagulation process. Results Ad|min1| obtained with mixed-trigger reagent (PT/APTT/buffer, 1 : 15 : 135) in the presence of emicizumab optimally corresponded to the conversion rate estimated in animals; 0.2-0.4 IU dL-1 equivalent FVIII per 1 µg mL-1 emicizumab). Ex vivo addition of emicizumab to HA plasma with or without inhibitors resulted in concentration-dependent increases in Ad|min1|, with some individual variations. The addition of various concentrations of FVIII to HA plasma mixed with emicizumab resulted in dose-dependent increases in Ad|min1|. Similarly, mixtures of activated prothrombin complex concentrate and emicizumab added to HA plasma resulted in dose-dependent increases in Ad|min1|. In contrast, enhanced coagulation potential appeared to be better defined by the clot time than by Ad|min1| in experiments using recombinant activated FVII. Conclusion The PT/APTT reagent-triggered adjusted CWA could provide a useful means of assessing global coagulation potential in emicizumab-treated HA patients, with enhanced activity neither masking nor being masked by FVIII or bypassing agents.

Factor V C2 domain contains a major thrombin-binding site responsible for thrombin-catalyzed factor V activation.

Factor (F)V is converted into its active form, FVa, by limited proteolysis. Thrombin-catalyzed activation of FV is essential for its full cofactor activation. Previously, we reported that thrombin was bound to the C2 domain in the light chain of FVIII. As FV has a similar domain structure to FVIII, we focused on the FV C2 domain as a possible binding region for thrombin. Kinetic parameters, measured by surface plasmon resonance, revealed that the K(d) values of anhydro-thrombin for FV, FVa, and the FV C2 domain were 66, 240, and 670 nmol L(-1), respectively. FV activation was increased by approximately 9-fold by the addition of thrombin. In the presence of the FV C2 domain, this increase of the FV activation was inhibited. However, FV activation was not inhibited by the addition of the FVIII C2 domain. FV was cleaved into a 105-kDa heavy chain and a 71/74-kDa light chain by thrombin-catalyzed proteolysis at Arg709, Arg1018 and Arg1545. In the presence of the FV C2 domain, the cleavage was inhibited at all sites. Proteolysis was not affected by the addition of the FVIII C2 domain. These results indicated that the FV C2 domain contains a major binding site for thrombin and that this domain is necessary for the proteolysis at all cleavage sites. Furthermore, the present results also suggested that thrombin has an independent binding site for FV different from that for FVIII.

Assessing the clinical severity of type 1 von Willebrand disease patients with a microchip flow-chamber system.

BACKGROUND: The clinical phenotype of von Willebrand disease (VWD) is heterogeneous, and von Willebrand factor ristocetin cofactor activity (VWF:RCo) does not always reflect clinical severity, especially in VWD type 1. We have reported the potential of a microchip flow-chamber system (Total-Thrombus Formation Analysis System [T-TAS®]) for assessing physiologic hemostasis in VWD. Aim To evaluate the relationship between T-TAS, bleeding score (BS) and laboratory test results in type 1 VWD patients. METHODS: Microchips coated with collagen (platelet chip [PL-chip]) or collagen/thromboplastin (AR-chip) were used to assess platelet thrombus formation (PTF) at high shear rates or fibrin-rich PTF at low shear rates, respectively, in whole blood from 50 patients. The times needed for the flow pressure to increase by 10 kPa and 30 kPa (T10 and T30 ) from baseline were calculated from flow pressure curves. BS was determined by the use of a standardized questionnaire. RESULTS: PL-T10 values correlated with BS (R(2) ~ 0.45) better than VWF:RCo (R(2) ~ 0.36), irrespective of the flow rate, whereas AR-T10 showed only a weak correlation with BS (R(2) ~ 0.18). Patients with PL-T10 > 10 min or AR-T10 > 30 min had lower VWF levels and higher BS than those with PL-T10 ≤ 10 min or AR-T10 ≤ 30 min, and the greatest differences were observed with PL-T10. Clinical severity appeared to correlate best with PL-T10 > 8 min. BS was significantly higher in patients with VWF:RCo of < 10 IU dL(-1) than in those with VWF:RCo of 10 IU dL(-1) to < 25 IU dL(-1) and 25-40 IU dL(-1). In patients with VWF:RCo of < 10 IU dL(-1) , BS was significantly higher in those with PL-T10 > 8 min than in those with PL-T10 ≤ 8 min. CONCLUSION: T-TAS could be a useful technique for discriminating and predicting BS in VWD type 1 patients.