Global coagulation function assessed by rotational thromboelastometry predicts coagulation-steady state in individual hemophilia A patients receiving emicizumab prophylaxis

Predictive parameters for spontaneous joint bleeding during emicizumab prophylaxis

ABSTRACT

Emicizumab is approved for prophylaxis of patients with hemophilia A (HA). Despite its efficacy in reducing bleeding, some patients on emicizumab still experience hemarthrosis, but no tool is yet available to identify those at a higher risk of spontaneous joint bleeding. This study aimed to evaluate whether laboratory measurements (global coagulation assays and emicizumab concentration) and/or arthropathy scores can distinguish patients at higher risk of spontaneous joint bleeding while on emicizumab prophylaxis. A thrombin generation assay was performed upon the addition of tissue factor and synthetic phospholipids. Nonactivated thromboelastography was performed on citrated whole blood. Emicizumab concentrations were measured using a modified 1-stage factor VIII assay. The degree of hemophilic arthropathy was assessed using the Hemophilia Joint Health Score and Hemophilia Early Arthropathy Detection with Ultrasound (HEAD-US) score. A Cox proportional hazards model was used to evaluate the association between variables and bleeding. The predictive power of these variables was investigated using receiver operating characteristic (ROC) analysis. Forty patients with severe HA, with or without inhibitors, on emicizumab prophylaxis were enrolled in an observational cohort study. Ten of 40 developed spontaneous joint bleeding. None of the laboratory parameters were able to distinguish patients with a higher risk of spontaneous joint bleeding. ROC analysis showed that during emicizumab prophylaxis, only the presence of synovitis and a higher HEAD-US score were associated with spontaneous joint bleeding (area under the curve, 0.84). A greater degree of arthropathy and the presence of synovitis could help predict the risk of spontaneous joint bleeding in patients with HA on emicizumab prophylaxis.

Low-dose emicizumab prophylaxis in patients with severe hemophilia A: a retrospective study bringing new hope for our patients

BACKGROUND

Low-dose emicizumab can potentially offer a cost-effective treatment option in persons with hemophilia A, especially in developing countries.

OBJECTIVES

To compare the efficacy and safety of low-dose emicizumab with those on low-dose factor (F)VIII prophylaxis via chart review.

METHODS

After ethics approval, chart data of 2 groups of patients were reviewed: group 1 (low-dose emicizumab, n = 10; 3 mg/kg monthly without a loading dose) and group 2 (low-dose FVIII prophylaxis, n = 10; 10-20 IU/kg of FVIII concentrates twice a week). Outcomes were target joints, annual bleeding rate, annual joint bleeding rate, Hemophilia Joint Health Score, nonactivated thromboelastometry-rotational thromboelastometry clotting time, plasma emicizumab levels, and direct costs of treatment.

RESULTS

All outcome measures were significantly better in the low-dose emicizumab group than in the low-dose FVIII prophylaxis group. For nonactivated thromboelastometry-rotational thromboelastometry, median values after 6 months in the low-dose emicizumab group were comparable with values seen in patients with mild hemophilia, while the values in the low-dose FVIII prophylaxis group were similar to those of patients with moderate hemophilia. The direct cost of low-dose emicizumab was found to be approximately US $6000 and that for low-dose recombinant FVIII prophylaxis used in our study was US $6282 (the cost may range from US $3432 to $7920 depending on the type of factor) when compared to approximately US $15 000 for standard-dose emicizumab.

CONCLUSION

Low-dose emicizumab offers a cost-effective treatment option and can improve access in developing countries. These findings need to be confirmed in a larger and better-controlled study.

The role of viscoelastic hemostatic assays for postpartum hemorrhage management and bedside intrapartum care

Viscoelastic hemostatic assays are point-of-care devices that assess coagulation and fibrinolysis in whole blood samples. These technologies provide numeric and visual information of clot initiation, clot strength, and clot lysis under low-shear conditions, and have been used in a variety of clinical settings and subpopulations, including trauma, cardiac surgery, and obstetrics. Emerging data indicate that these devices are useful for detecting important coagulation defects during major postpartum hemorrhage (especially low plasma fibrinogen concentration [hypofibrinogenemia]) and informing clinical decision-making for blood product use. Data from observational studies suggest that, compared with traditional formulaic approaches to transfusion management, targeted or goal-directed transfusion approaches using data from viscoelastic hemostatic assays are associated with reduced hemorrhage-related morbidity and lower blood product requirement. Viscoelastic hemostatic assays can also be used to identify and treat coagulation defects in patients with inherited or acquired coagulation disorders, such as factor XI deficiency or immune-mediated thrombocytopenia, and to assess hemostatic profiles of patients prescribed anticoagulant medications to mitigate the risk of epidural hematoma after neuraxial anesthesia and postpartum hemorrhage after delivery.

Hemostatic Profile of Intrauterine Growth-Restricted Neonates: Assessment with the Use of NATEM Assay in Cord Blood Samples

BACKGROUND

Intrauterine growth restriction (IUGR) is associated with hemorrhagic and thrombotic complications during the perinatal period. Thrombocytopenia, platelet dysfunction, and prolonged standard coagulation tests are observed in this population. The aim of this study is to examine the hemostatic profile of IUGR neonates with the use of a non-activated assay (NATEM) in cord blood samples.

METHODS

During an 18 month period, a NATEM ROTEM assay was performed on cord blood samples of 101 IUGR neonates. A total of 189 appropriate for gestational age (AGA) neonates were used as a control group. The NATEM variables recorded include the following: clotting time (CT); clot formation time (CFT); clot amplitude at 5, 10, and 20 min (A5, A10, A20); α-angle (a°); maximum clot firmness (MCF); lysis index at 30 and 60 min (LI30, LI60); and maximum clot elasticity (MCE).

RESULTS

IUGR neonates demonstrate a hypocoagulable state, with lower A5, A10, A2, MCF, and MCE values when compared to AGA. Using multiple linear regression, we determined IUGR as an independent factor influencing all NATEM parameters (except CT and LI30) exhibiting a hypocoagulable and hypofibrinolytic profile. Platelet count was positively correlated with A5, A10, A20, MCF, alpha angle, and MCE, and negatively correlated with CFT.

CONCLUSION

IUGR neonates appear with lower clot strength and elasticity and prolonged clot kinetics, as illustrated by ROTEM variables.

ROTEM could be useful for lupus anticoagulant hypoprothrombinemia syndrome

BACKGROUND

Lupus anticoagulant-hypoprothrombinemia syndrome (LAHPS) is a rare disease caused by acquired factor II (FII) deficiency and lupus anticoagulant. Patients with LAHPS typically present with thrombosis and bleeding. However, little information is available on the evaluation of coagulation potential in patients with LAHPS. We examined global coagulation potentials in patients with LAHPS during the clinical course in this study.

METHODS

Coagulation potentials in two pediatric patients with LAHPS were assessed by measuring clotting time (CT) and clot formation time using Ca2+-triggered rotational thromboelastometry (ROTEM), CT and maximum coagulation velocity using clot waveform analysis (CWA), and lag time and peak thrombin using the thrombin generation assay (TGA). The day of admission was defined as day 0.

RESULTS

In case 1, the bleeding symptoms disappeared by day 5. However, the TGA and CWA results were markedly lower than normal, although FII activity (FII:C) returned to within the normal range by day 14. In contrast, ROTEM revealed a recovery to near-normal levels (day 14). All coagulation parameters (day 80) were within normal ranges. In case 2, coagulation potential was severely depressed until day 12, although FII:C returned to normal levels. Bleeding symptoms disappeared on day 19, and the ROTEM data revealed that the parameters were close to the normal range. The coagulation parameters in all assays were normalized on day 75.

CONCLUSIONS

Recovery of coagulation potential in patients with LAHPS was slower than the recovery of FII:C. Moreover, ROTEM appeared to be clinically useful for assessing coagulation potential in patients with LAHPS.

Expert opinion paper on the treatment of hemophilia a with emicizumab

INTRODUCTION

Prophylaxis with emicizumab, a bispecific monoclonal antibody that mimics FVIII function, has shown encouraging results in clinical trials in terms of efficacy and safety. However, current experience is limited, and many areas of concern to clinicians have yet to be reviewed.

AREAS COVERED

This paper reviews the experience of hemophilia A patients treated with emicizumab based on the results of clinical trials and real-life studies. The authors place special emphasis on issues such as the management of these patients in situations of hemorrhage and/or surgical interventions, joint health or laboratory monitoring.

EXPERT OPINION

Treatment with emicizumab has been shown to improve joint health and reduce bleeding, of particular interest to patients with inhibitors and high bleeding rates. However, there are still concerns about its administration in neonates and previously untreated patients due to limited reported experience. Laboratory monitoring is not strictly necessary due to the stable pharmacokinetics emicizumab has been shown to exhibit, however, tests that globally assess hemostasis may be useful especially in cases of bleeding or surgery. The authors are also of the opinion that prophylaxis before minor surgery is not necessary and that major surgeries can be safely performed with additional prophylactic coagulation factor.Trial registration ClinicalTrials.gov identifier: NCT04431726..

Pharmacodynamics Monitoring of Emicizumab in Patients with Hemophilia A

BACKGROUND

 Emicizumab is a bispecific antibody mimicking coagulation factor VIII (FVIII) employed to treat patients with hemophilia A (PwHA) regardless of FVIII inhibitor status. The identification of biological markers reflecting the hemostatic competence of patients under emicizumab therapy would have a great clinical value. Unfortunately, emicizumab over-corrects standard coagulation assays, precluding their use for evaluating the hemostatic correction achieved in vivo. Here, we investigated whether global coagulation assays (GCA) would allow monitoring the biological response to non-factor replacement therapy with emicizumab.

MATERIALS AND METHODS

 Six adults PwHA received a weekly dose of emicizumab of 3 mg/kg during weeks (W) 1 4 and 1.5 mg/kg from W5 onwards. Response to treatment was monitored weekly by emicizumab plasma concentration, thrombin generation (TG), and fibrin clot formation (FCF) and structure. TG and FCF results were compared to patient baseline, FVIII replacement, and healthy donors.

RESULTS

 TG and FCF significantly increased in PwHA after the loading period, reaching a plateau that lasted until the end of monitoring. Similarly, fibrin clot network became denser with thinner fibrin fibers. However, TG contrary to FCF remained at the lower limits of reference values. Remarkably, despite having similar plateau concentrations of emicizumab some patients showed markedly different degrees of TG and FCF improvement.

CONCLUSION

 Our study enriches the knowledge on the use of GCA to monitor non-factor replacement therapy, indicating that TG and FCF could act as direct markers of emicizumab biological activity. GCA allow to capture and visualize the individually variable response to emicizumab, leading a step forward to the personalization of patient treatment.

The Use of Bypassing Treatment Strategies in Hemophilia and Their Effect on Laboratory Testing

Factor VIII and IX inhibitors in congenital hemophilia A and B, respectively, neutralize the infused coagulation factor concentrate rendering them ineffective. Bypassing agents (BPAs) that circumvent the block imposed by the inhibitors are used for the prevention and management of bleeding. Activated prothrombin complex concentrate was the original BPA, recombinant activated factor VII was then introduced, and more recently nonfactor agents that target the procoagulant and anticoagulant systems have been developed and are in clinical use (e.g., emicizumab, a bispecific antibody for hemophilia A). Other BPAs are in clinical trials (e.g., fitusiran targets antithrombin, concizumab and marstacimab target tissue factor pathway inhibitor, and SerpinPC targets activated protein C). The BPAs have a varied effect on coagulation assays, and as more patients are exposed to these agents, it is important to be aware of the effects. Herein, we present an overview of the effect of BPAs on routine and specialized coagulation assays including thrombin generation and viscoelastic assays.

Clot Waveform Analysis for Monitoring Hemostasis

Clot waveform analysis (CWA) is a recently developed global coagulation assessment, based on the continuous observation of changes in light transmittance, absorbance, or light scattering that occurs as fibrin formed in a plasma sample during routine clotting tests such as activated partial thromboplastin time (aPTT) and prothrombin time (PT). CWA can utilize qualitative waveform patterns as well as sensitive quantitative parameters and can be used as a simple method to assess global hemostasis, and can be applied to various challenging clinical situations. Although not all coagulation analyzers currently in use are able to provide CWA, the number of analyzers available to do so is increasing, as the usefulness of this process has become more widely recognized. CWA can be based on the coagulation mechanism of aPTT, an intrinsic trigger, and this has been reported in many studies, including diagnosis and treatment of patients with hemophilia, disseminated intravascular coagulation, and monitoring of anticoagulants and thrombosis. CWA using trace amounts of tissue factors also has the potential to expand the applications of this technology. Recently, there have been reports of the combined evaluation of fibrinolytic dynamics. Among the existing global coagulation assays, CWA may prove to be the easiest to standardize in clinical practice. However, more extensive testing using standardized methods in various clinical settings is needed to determine the true role of CWA in the evaluation of hemostasis and thrombosis in the future.

Study protocol for assessment of the coagulation potential of concomitantly used factor VIII concentrates in patients with haemophilia A with emicizumab prophylaxis (CAGUYAMA Study): a multicentre open-label non-randomised clinical trial

INTRODUCTION

Emicizumab prophylaxis substantially reduces bleeding episodes in patients with haemophilia A (HA). The haemostatic efficacy of emicizumab in patients with HA is estimated as approximately 15% based on mimic activity of factor (F) VIII. Although it has been proven effective in preventing bleeding, its haemostatic effect during breakthrough bleeding or surgery is considered insufficient. Therefore, haemostatic management of emicizumab-treated patients with HA without inhibitors frequently requires FVIII replacement therapy. In haemostatic management of emicizumab-treated patients with HA, conventional FVIII dosage calculations are used in clinical practice without considering the coagulant effects of emicizumab.

METHODS AND ANALYSIS

In the CAGUYAMA study, 100 patients with HA without inhibitors will be enrolled for a maximum duration of 1 year, and samples of 30 events following the concomitant use of FVIII concentrates (30±5 U/kg) with emicizumab will be collected. An 'event' is defined as obtaining blood samples at preadministration and postadministration of FVIII concentrates during a breakthrough bleeding or a surgical procedure. Global coagulation assays will be used to measure the coagulation potential of the obtained samples. Clot waveform analysis (CWA) is used to identify the primary end-point, that is, the degree of improvement in the maximum coagulation rate at preadministration and post-administration of fixed-dose FVIII concentrations. The parameter obtained from CWA, which is triggered by an optimally diluted mixture of prothrombin time reagent and activated partial thromboplastin time reagent, is reported to be an excellent marker for assessing the degree of improvement of the coagulation potential in emicizumab-treated plasmas.

ETHICS AND DISSEMINATION

The CAGUYAMA study was approved by the Japan-Certified Review Board of Nara Medical University (Approval ID; nara0031). The study results will be communicated through publication in international scientific journals and presentations at (inter)national conferences.

TRIAL REGISTRATION NUMBER

jRCTs051210137.

Clinical pharmacology of emicizumab for the treatment of hemophilia A

INTRODUCTION

Emicizumab is a humanized bispecific antibody approved for the routine prophylaxis of bleeding episodes in patients with hemophilia A (PwHA) regardless of the presence of factor VIII (FVIII) inhibitors. It mimics the cofactor function of missing activated FVIII by bridging activated factor IX and factor X, thereby restoring hemostasis.

AREAS COVERED

This review covers the clinical pharmacology of emicizumab and the translation of its pharmacokinetics (PK) and pharmacodynamics (PD) to clinical efficacy and safety. The PK of emicizumab is linear, with an approximately 1-month half-life. Once-weekly to every-4-week subcutaneous (SC) administrations maintain effective trough concentrations throughout the dosing intervals, associated with a coagulation potential analogous to that in patients with mild hemophilia A. In combination with activated prothrombin complex concentrate, and to a lesser extent with recombinant activated factor VII, emicizumab exerts a synergistic effect, whereas combination with FVIII may result in a non-additive coagulation potential at normal FVIII activity.

EXPERT OPINION

The translation of emicizumab PK/PD into clinical effects was demonstrated in several phase III studies, which showed remarkable bleed control and a favorable safety profile in PwHA. These emicizumab attributes, together with the convenience of use (infrequent SC injections), offer a novel paradigm for the management of PwHA.

Antithrombotic Treatment in Patients With Hemophilia: an EHA-ISTH-EAHAD-ESO Clinical Practice Guidance

Cardiovascular disease is an emerging medical issue in patients with hemophilia (PWH) and its prevalence is increasing up to 15% in PWH in the United States. Atrial fibrillation, acute and chronic coronary syndromes, venous thromboembolism, and cerebral thrombosis are frequent thrombotic or prothrombotic situations, which require a careful approach to fine-tune the delicate balance between thrombosis and hemostasis in PWH when using both procoagulant and anticoagulant treatments. Generally, PWH could be considered as being naturally anticoagulated when clotting factors are <20 IU/dL, but specific recommendations in patients with very low levels according to the different clinical situations are lacking and mainly based on the anecdotal series. For PWH with baseline clotting factor levels >20 IU/dL in need for any form of antithrombotic therapy, usually treatment without additional clotting factor prophylaxis could be used, but careful monitoring for bleeding is recommended. For antiplatelet treatment, this threshold could be lower with single-antiplatelet agent, but again factor level should be at least 20 IU/dL for dual antiplatelet treatment. In this complex growing scenario, the European Hematology Association in collaboration with the International Society on Thrombosis and Haemostasis, the European Association for Hemophilia and Allied Disorders, the European Stroke Organization, and a representative of the European Society of Cardiology Working Group on Thrombosis has produced this current guidance document to provide clinical practice recommendations for health care providers who care for PWH.

Successful living donor liver transplantation in a patient with hemophilia A and factor VIII inhibitor: a case report with perioperative recommendations

Liver transplantation in patients with end-stage liver disease and coexisting hemophilia A has been described. Controversy exists over perioperative management of patients with factor VIII inhibitor predisposing patients to hemorrhage. We describe the case of a 58-year-old man with a history of hemophilia A and factor VIII inhibitor, eradicated with rituximab prior to living donor liver transplantation without recurrence of inhibitor. We also provide perioperative management recommendations from our successful multidisciplinary approach.

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.

The Utility of NATEM Assay in Predicting Bleeding Risk in Critically Ill Neonates

We aimed to investigate the hemostatic status of diseased neonates using nonactivated rotational thromboelastometry (ROTEM) assay (NATEM) assay and, in addition, to evaluate the discriminative power of NATEM parameters in predicting the risk of bleeding in critically ill neonates and compare it to that of EXTEM (extrinsically activated ROTEM) parameters. This cohort study included 158 consecutive, critically ill neonates with presumed sepsis, perinatal hypoxia, or respiratory distress syndrome. The EXTEM and NATEM assays were performed on the first day of disease onset. The neonatal bleeding assessment tool was used to record and assess clinical bleeding events on the day of ROTEM analysis. Several EXTEM and NATEM ROTEM parameters differed between neonates with and without clinical bleeding events, indicating a hypo-coagulable state in neonates with clinical bleeding. NATEM parameters had comparable predictive performance for clinical bleeding events with EXTEM parameters for clotting time, clot formation time (CFT), A10 (clot amplitude at 10minutes), maximum clot firmness, lysis index at 60minutes, and maximum clot elasticity (p>0.05). However, NATEM A20, A30, and α angle demonstrated better predictive ability than EXTEM A20, A30, and α angle, respectively (p<0.05). A NATEM CFT value ≥147seconds presented 95.2% sensitivity (95% confidence interval [CI]: 76.1-99.8%) and 65.6% specificity (95% CI: 57.1-73.5%) to detect neonates with clinical bleeding, while a NATEM A10 value ≤42mm had 80.8% sensitivity (95% CI: 71.8-85.9%) and 76.0% specificity (95% CI: 52.8-91.7%) to detect neonates with clinical bleeding events. The NATEM assay has shown remarkable sensitivity in predicting bleeding in critically ill neonates, exceeding EXTEM performance in some selected parameters. The incorporation of NATEM test parameters in predictive models for neonatal hemorrhage seems promising.

High levels of factor VIII activity in patients with acquired hemophilia A in remission are associated with unusually low coagulation potentials

BACKGROUND

Elevated factor VIII activity (FVIII:C) is often observed in patients with acquired hemophilia A (PwAHA) in remission. However, comprehensive coagulation potentials in this patient group remain to be investigated.

AIM

To evaluate comprehensive coagulation potentials in PwAHA.

METHODS

We investigated coagulation function in eleven PwAHA with high FVIII:C (> 150 IU/dL) using thrombin generation assay (TGA) and/or rotational thromboelastometry (ROTEM), and compared findings with results obtained from contrived samples generated by spiking recombinant FVIII.

RESULTS

The median FVIII:C and FVIII inhibitor titers during remission in enrolled PwAHA were 206 IU/dL and 0.44 BU/mL, respectively. In all patients, lag time and time to peak were either prolonged or normal compared to contrived samples corresponding to their FVIII:C. However, higher values of peak thrombin and endogenous thrombin potentials compared to contrived samples were observed in two patients. ROTEM parameters were within normal ranges in all cases. One patient (FVIII:C 171 IU/dL) developed venous thrombosis and pulmonary embolism, but TGA parameters showed low or normal coagulation potential compared to contrived samples corresponding to his FVIII:C.

CONCLUSION

PwAHA with high FVIII:C could exhibit lower coagulation potentials than those corresponding to their FVIII:C.

Current and future therapies for haemophilia-Beyond factor replacement therapies

Some non-factor products that work by facilitating the coagulation pathway (emicizumab) and blocking the anticoagulant pathway (fitusiran, concizumab and marstacimab) for patients with haemophilia (H) have been developed, and clinical trials using these products are currently ongoing. Prophylaxis using non-factor products by subcutaneous administration provides marked reductions of bleeding episodes in patients with HA or HB, regardless of the presence of inhibitor. Emicizumab has already been approved globally. Emicizumab alters the phenotype of patients with HA from severe to mild by maintaining trough levels of equivalent factor VIII activity (15-20 iu/dl). Phase 3 clinical trials and long-term observations assessing emicizumab revealed tolerable safety and efficacy. However, thrombotic events have occurred in patients receiving these non-factor products. Furthermore, monitoring of the haemostatic function of these products with concomitant therapy is also required in clinical practice. These products have promising haemostatic efficiency, but wider clinical experience is needed to provide optimal therapeutic strategies in the future.

Two pediatric cases of severe hemophilia A in which emicizumab prophylaxis failed to prevent traumatic extra-articular hemorrhage

Emicizumab reduces bleeding episodes in patients with severe hemophilia A (PwHA). Little information is available on hemostatic management of severe traumatic hemorrhages in emicizumab-treated pediatric PwHA. We assessed therapeutic efficacy and global coagulation potentials in two pediatric cases of emicizumab-treated pediatric PwHA with intracranial or retroperitoneal/iliopsoas hemorrhage. A modified clot waveform analysis (CWA) triggered by mixtures of tissue factor and ellagic acid was used to assess coagulant potentials, and maximum coagulant velocity (Ad|min1|) was calculated. One patient with intracranial hemorrhage was treated with continuous infusions of recombinant factor VIII (rFVIII) at a dose of 4-4.6 IU/kg/hr for 9 days, followed by bolus infusion at 66 IU/kg/day for 2 days and 33 IU/kg/day for an additional 2 days. The Ad|min1| was increased from 5.5 (at baseline) to 7.0-8.1 under concomitant treatment and maintained within or near normal range (IQR; 6.9-7.7). The other patient with retroperitoneal/iliopsoas hemorrhage received bolus infusions of rFVIII at 50 IU/kg/day for 20 days and every-other-day infusion of rFVIII for 8 days. The Ad|min1| was increased from 5.2 (at baseline) to 5.8-6.8 under concomitant treatment and maintained within the normal range. We successfully managed a treatment plan for severe traumatic bleeding in emicizumab-treated pediatric PwHA using modified CWA.

Heterogeneous coagulant potential of emicizumab in neonatal factor VIII-deficient plasma

BACKGROUND

Emicizumab prophylaxis reduces bleeding in hemophilia A (HA) patients. However, there are few data on emicizumab treatment in neonates with HA (neonate-HA), and the procoagulant effects of emicizumab in these patients are unknown.

AIM

To investigate the coagulation activity of emicizumab in vitro in a plasma model of neonate-HA.

METHODS

Plasmas from 84 neonates with non-HA were enrolled. However, due to the limited plasma volumes in some cases, 50 plasmas were assigned to two different assay groups. To prepare the neonate-HA model, plasma was first preincubated with an antifactor (F) VIII A2 monoclonal antibody (mAb). After further incubation with emicizumab, global coagulation activity was measured: adjusted maximum coagulation velocity (Ad|min1|) in clot waveform analysis (CWA) and peak thrombin in thrombin generation assay (TGA).

RESULTS

Because the addition of anti-FVIII mAb to 22 of 43 samples showed little decrease in Ad|min1|, the remaining 21 samples were analyzed by CWA. The addition of emicizumab increased Ad|min1| in 18 of the 19 cases (effective group) but not in the remaining 3 cases (noneffective group). Similarly, TGA found that emicizumab (effective group) improved peak thrombin in seven of the nine samples tested, but two cases did not respond (noneffective group). Although the effective group had lower levels of FX, there was no significant difference between the effective and noneffective groups in terms of FIX, protein S, protein C, antithrombin, and fibrinogen.

CONCLUSIONS

The in vitro coagulant potentials of emicizumab in the neonate-HA model were more heterogeneous than those recorded in the adult-HA model.

Assessment of agreement between EXTEM and NATEM thromboelastometry measurement assays in critically ill neonates

OBJECTIVES

To investigate the agreement between the EXTEM and NATEM measurements.

METHODS

In this retrospective observational study, EXTEM and NATEM analyses were performed on blood samples from 162 ill neonates, providing 324 paired measurements. The agreement between EXTEM and NATEM measurements was evaluated by the nonparametric spearman's rank correlation to assess the correlation between the paired measurements, by the Bland-Altman analysis for the graphical presentation of the agreement, and by the Deming regression model to assess the significance of the agreement. The agreement between the two methods for the detection of bleeding events was determined by kappa statistic.

RESULTS

Strong correlations were found between EXTEM and NATEM measurements for A10, MCF. The Bland-Altman plots showed good agreement for A10, MCF, LI60, and alpha angle parameters, while CT showed a nearly linear slope indicating that bias increased with the mean. The highest agreement for bleeding events was found for the A10 parameter (κ = 0.70, p < .001), while the lowest for the CT parameter (κ = 0.36, p = .94).

CONCLUSIONS

NATEM parameters that reflect clot firmness and fibrinolytic activity are strongly correlated with the corresponding EXTEM measurements with a good agreement between them, indicating that these two methods could be used interchangeably.

Coagulation dysfunction of severe burn patients: A potential cause of death

BACKGROUND

Research on coagulation dysfunction following burns is controversial. This study aimed to describe the coagulation changes in severe burn patients by examining coagulation parameters.

METHODS

Patients with third-degree total body surface area (TBSA) burns of ≥30% were enrolled between 2017 and 2020. Platelet (PLT) count and coagulation indexes (including APTT, INR, FIB, DD, and AT Ⅲ) were measured at admission and once weekly for 8 weeks, and statistical analysis was performed. The patient medical profiles were reviewed to extract demographic and clinical data, including TBSA, third-degree TBSA, and inhalation injury. The total intravenous fluids and transfusions of crystalloids, fresh frozen plasma (FFP), and red blood cells (RBC) were calculated during the forty-eight-hour period. The number of sepsis cases was recorded.

RESULTS

We enrolled 104 patients , and while the overall coagulation trend fluctuated, inflection points appeared around one week and demonstrated hypercoagulability. INR was significantly higher in the non-survival group than in the survivors' group from admission to three weeks after burn (all p<0.01). From post-injury week 1 to post-injury week 3, the APTT in the non-survival group was greater than in the survival group, but the non-survival group's PLT count was lower than that in the survival group (all p<0.05). At two and three weeks after burns, the FIB levels in the non-survival group were significantly lower than those of the survival group (both p<0.01). The prevalence of inhalation injury and the proportion of sepsis cases were significantly higher in the non-survival group than in the survival group ( p ＜ 0.05, p ＜ 0.001, respectively). At the time of death, APTT, INR, and FDP levels were significantly higher in the non-survival group in the survivor group, and FIB, ATIII, and PLT were significantly lower than in the survivor group (all p<0.01). On the day of death, nine of the 12 dead patients had disseminated intravascular coagulation (DIC).

CONCLUSIONS

Coagulation dysfunction was most prominent in severe burn patients 1 week after injury and presented as hypercoagulability. Large-area burn injury, large amounts of fluid resuscitation, inhalation injury, and sepsis may all contribute to coagulation dysfunction, which can further develop into DIC and even death in severe burns patients.

A case of a young boy with hyper-fibrinolysis associated with natural fibrin precipitates suspected to have occurred through a novel coagulation and fibrinolysis mechanism

An 8-year-old Japanese boy with no underlying disease presented with severe intramuscular hematoma of the hip, and was admitted for a disseminated intravascular coagulation-like state with fibrinolytic dominance. Laboratory examinations revealed severe hyper-fibrinolysis with elevated markers, markedly shortened euglobulin clot lysis time, mildly decreased prothrombin, and severely decreased fibrinogen and factor XIII. Natural fibrin precipitates rapidly appeared in citrate-treated, ethylene-diamine-tetra-acetic-treated, and heparin-treated samples, but not in argatroban-treated samples, indicating that the mechanism of thrombin and fibrin formation was Ca²⁺-independent. The precipitates were physically similar to thrombin-triggered plasma fibrin. A global coagulation assay revealed that thrombin generation potentials were normal throughout the clinical course, whereas plasmin generation was already detected before initiation of fibrin formation in the acute phase. This phenomenon disappeared with time. Changes in coagulation abnormalities and nature of fibrinolysis paralleled those seen in specific markers for streptococcal infections. Streptokinase was possibly involved in this disease, as SDS-polyacrylamide gel electrophoresis revealed that plasmin derived from streptokinase-plasminogen complex proteolyzed the prothrombin to approximately 35-kDa α-thrombin consisting of the A-B single chain, which was identified by NH₂-terminal sequence analysis. The involvement of streptokinase-plasminogen-prothrombin caused by streptococcal infection may be one mechanism that produces marked hyper-fibrinolysis associated with natural fibrin precipitates.

The Non-Activated Thromboelastometry (NATEM) Assay's Application among Adults and Neonatal/Pediatric Population: A Systematic Review

The non-activated thromboelastometry (NATEM) assay is a point-of-care assay that can provide a comprehensive insight into the actual hemostatic mechanism. However, there are very limited data about its use in clinical practice. The aim of this study was to systematically review the literature for any data regarding the use of NATEM in several clinical settings. A systematic review of PubMed and Scopus databases was conducted through 20 January 2022 for studies evaluating the use of the NATEM assay in different clinical settings. The literature search yielded a total of 47 publications, 30 of which met the eligibility criteria for this review. Evaluation of NATEM’s detecting ability for hemostasis disorders is limited in the literature. The results of the included studies indicate that NATEM seems to be a sensitive method for the detection of hyperfibrinolysis and may have an advantage in the diagnosis of hemostatic disorders. It could be more informative than the other ROTEM assays for detecting changes in coagulation parameters in patients who receive anticoagulants. However, the reported outcomes are highly varying among the included studies. NATEM has a high sensitivity to detect hypo- or hypercoagulability and provides a detailed insight into the whole hemostatic process from clot formation to clot breakdown. It could be a useful technique in variable fields of medicine, not only in adults, but also in pediatric and neonatal populations, to guide different hemostatic treatments and predict coagulation disorders or mortality/morbidity; this issue remains to be further investigated.

Regression Analysis to Estimate the Factor VIII Activity of Patients with Hemophilia A Without Inhibitor who Received Emicizumab Therapy

BACKGROUND

 Emicizumab, a bispecific monoclonal antibody for hemophilia A (HA), has strong pharmacodynamic effects in several coagulation assays resulting in dosing difficulties with Factor VIII (FVIII) concentrates during bleeding emergencies.

MATERIALS AND METHODS

Single and multiple regression models were studied to estimate FVIII activity using 27 archived plasma samples from three patients with HA without inhibitor under emicizumab treatment. Explanatory variables were FVIII chromogenic assay (CSA), Ad|min1|, Ad|min2|, the number of seconds of APTT, and the FVIII one-stage assay (OSA), which were measured without idiotype antibodies. The response variable was FVIII OSA measured with idiotype antibodies.

RESULTS

In the simple linear model, the FVIII CSA regression coefficient was 1.04 and the intercept was -14.55 (r² = 0.95; p < 0.001). In the multiple regression model, FVIII OSA and FVIII CSA were selected based on the Akaike Information Criterion, with regression coefficients of 1.74 and 1.15, respectively, and an intercept of -92.03 (r² = 0.96, p < 0.001).

CONCLUSIONS

The regression models can estimate the FVIII:C levels in patients with HA receiving emicizumab and would be useful in a bleeding emergency and/or surgery.

Assessment of global coagulation function under treatment with emicizumab concomitantly with bypassing agents in haemophilia A with inhibitor (UNEBI Study): multicentre open-label non-randomised clinical trial

INTRODUCTION

Subcutaneous emicizumab prophylaxis substantially reduces bleeding episodes in patients with haemophilia A (PwHA) and factor VIII inhibitor. However, thrombotic events occurred in some PwHA with inhibitor who had received high cumulative doses of activated prothrombin complex concentrates at their breakthrough bleeds, when they were also given prophylactic emicizumab. After that, although the recommended guidance was proposed for bypassing agents (BPAs) therapy under emicizumab prophylaxis for haemostatic management, detailed investigation(s) is(are) required to elucidate the safe and appropriate dose of BPAs to use concomitantly with emicizumab prophylaxis.

METHODS AND ANALYSIS

In the UNEBI Study, 60 PwHA with inhibitor will be enrolled for a maximum duration of 3 years, and samples of 20 events following concomitant use of BPAs with emicizumab will be collected. An 'event' is defined as obtaining blood samples before and after administration of BPA when a breakthrough bleed or a surgical procedure occurs. The coagulation potential in the obtained samples will be measured by global coagulation assays. The primary endpoint is the degree of improvement in the maximum coagulation rate by clot waveform analysis (CWA) before and after administration of fixed-dose BPAs. This parameter obtained from CWA, which is triggered with an optimally diluted mixture of prothrombin time/activated partial thromboplastin time-reagents, is reported to be an excellent marker for assessing the degree of improvement in coagulation potential in emicizumab-treated plasma.

ETHICS AND DISSEMINATION

The UNEBI Study was approved by the Japan Certified Review Board of Nara Medical University. The results of the study will be communicated through publication in international scientific journals and presentations at (inter)national conferences.

TRIAL REGISTRATION NUMBER

jRCTs051190119.

Comparisons of global coagulation potential and bleeding episodes in emicizumab-treated hemophilia A patients and mild hemophilia A patients

Emicizumab reduces bleeding events in patients with severe hemophilia A (HA). The coagulation potential of emicizumab at a clinical dose appears to correspond to about 15 IU/dL of factor VIII activity (FVIII:C), the equivalent of converting from a severe to mild phenotype. However, the clinical and laboratory characteristics of HA patients receiving emicizumab (Emi-PwHA) compared with patients with mild HA (PwMHA) remain to be determined. We reviewed clinical data from Emi-PwHA (n = 63) and PwMHA (n = 15) and evaluated comprehensive coagulation function using Ca²⁺-triggered rotational thromboelastometry (ROTEM) and ellagic acid/tissue factor-triggered clot waveform analysis (modified CWA). The median FVIII:C in PwMHA was 13.0 (IQR 8.5-17.0) IU/dL. Bleeding patterns in both groups were similar and classified into three categories: (1) spontaneous bleeding, post-traumatic, (2) bleeding within 1-2 days, and (3) delayed bleeding after 1-2 weeks. The coagulation potential in Emi-PwHA with and without breakthrough bleeds was comparable. Furthermore, coagulation function in Emi-PwHA was equivalent to PwMHA, although time between treatment and hospitalization for breakthrough bleeds in PwMHA appeared to be longer than those in Emi-PwHA. The coagulation potential and bleeding patterns appeared to be similar in Emi-PwHA and PwMHA, indicating that emicizumab-driven coagulation potential reflected mild HA.

Hemostatic rebalance in neonatal intrahepatic cholestasis with citrin deficiency

BACKGROUND

Neonatal intrahepatic cholestasis with citrin deficiency (NICCD) results in coagulopathy due to decreased levels of vitamin (V)K-dependent clotting factors, similar to biliary atresia (BA). However, the involvement of VK-independent coagulant and anticoagulant factor(s) remains unknown. We examined relationships between coagulant and anticoagulant potential before and after nutritional treatment in NICCD.

METHODS

Three cases (aged 12, 21, and 45 days) with NICCD-associated coagulopathy were evaluated with standard coagulation/anticoagulation tests and comprehensive coagulation assays, rotational thromboelastometry, and protein C/protein S (PC/PS) pathway function assay (ThromboPath^® ), before and after nutritional treatment.

RESULTS

In all cases, activated partial thromboplastin time and prothrombin time were significantly prolonged, which is associated with very low levels of VK-independent fibrinogen and antithrombin. The initiation of nutritional treatment of medium-chain triglycerides oil improved these levels within the normal range, although low levels of other clotting factors were modestly increased. Whole blood- rotational thromboelastometry analysis revealed near-normal coagulation potential, even before treatment, comparable to healthy adults, and supportive of their non-bleeding symptoms. The introduction of nutritional treatment had further improved comprehensive coagulation potential. The global PC/PS-pathway function assay demonstrated the absence of the features of this function associated with the pathogenesis of NICCD. Compared to BA, the plasma levels of fibrinogen and antithrombin in all cases were markedly low, whilst those after treatment improved, especially to similar level of BA.

CONCLUSIONS

Neonatal intrahepatic cholestasis with citrin deficiency has the characteristic of rebalancing hemostatic mechanisms associated with coagulant and anticoagulant potential involving low levels of fibrinogen and antithrombin, suggesting a pathophysiological coagulopathy distinct from BA.

Coagulation potential in pediatric patients with immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is the most prevalent primary chronic glomerular disease in children. Understanding the changes in coagulability caused by IgAN is important for clarifying pathophysiology and choice of treatment. The coagulation potential in patients with IgAN remains to be investigated, however. We aimed to assess comprehensive coagulation potential in pediatric patients with IgAN and explore its relationship with pathological disease severity.

METHODS

Fourteen children with IgAN diagnosed by renal biopsy, who were admitted at Nara Medical University Hospital between 2015 and 2020, were analyzed. Rotational thromboelastometry was used to evaluate coagulation potential. Values of rotational thromboelastometry parameters in patients with IgAN were compared with those in control children.

RESULTS

In patients with IgAN (aged median 9.5 year), clotting time plus clot formation time (CT + CFT) was shortened (P = 0.003) and α angle was greater (P < 0.001) than those in controls, indicating a hypercoagulable state. The rate of mesangial hypercellularity of glomeruli correlated with CT + CFT, α, and maximum clot firmness (MCF) (r_s = -0.79, 0.56, and 0.37). The rate of cellular/fibrocellular crescent of glomeruli correlated with CT + CFT, α, and MCF (r_s = -0.41, 0.60, and 0.50). Patients with mesangial hypercellularity ≥80% of glomeruli showed reduced CT + CFT and increased α angle (P = 0.007 and 0.03). Patients with cellular/fibrocellular crescent ≥10% of glomeruli showed decreased CT + CFT and increased α angle (both P = 0.02).

CONCLUSIONS

The hypercoagulable state in pediatric patients with IgAN may be associated with the pathological severity of their disease.

Bispecific antibodies for the treatment of hemophilia A

INTRODUCTION

Emicizumab is a bispecific antibody exerting cofactor function of FVIIIa irrespective of the presence of FVIII inhibitors. Long-term data of phase 1/2 and phase 3 studies have been accumulated. Various questions such as indicated patients, ITI, application to PUPs, hemostatic treatment including surgeries, and emicizumab-related morbidity remain to be solved.

AREAS COVERED

The review describes the mode of action, data from pre-/post-marketing and ongoing clinical studies according to PubMed search and our own works.

EXPERT OPINION

For patients with a persistent inhibitor, emicizumab is a definite therapeutic option, although the possibility of BPAs-associated thromboembolic/TMA events raises concerns. The use of ITI together with emicizumab prophylaxis is being examined in clinical trials. For non-inhibitor, especially pediatric patients, emicizumab prophylaxis can be an option. Outcome assessment 'beyond ABR' such as joint health, physical/mental activity, QOL is required. Furthermore, continuous data collection for emicizumab-related adverse events and morbidity would be recommended.

Emicizumab prophylaxis: Prospective longitudinal real-world follow-up and monitoring

INTRODUCTION

Real-world data on prophylaxis of severe haemophilia A (HA) patients treated by emicizumab are scarce.

AIM

To study the efficacy and safety of longitudinal emicizumab prophylaxis and assess laboratory monitoring correlations in a large patient cohort.

METHODS

HA patients with and without FVIII inhibitors, initiating emicizumab prophylaxis, were prospectively enrolled. Bleeding, adverse events and surgeries were documented. FVIII inhibitors, emicizumab levels and thrombin generation (TG) were sequentially measured.

RESULTS

A total of 107 patients, including 58 children (whose median (IQR) age was 6 (1-11) years) with severe HA, composed the study cohort. Twenty-nine per cent (31/107) of our HA patients had FVIII inhibitors. Patients were followed for a median of 67 weeks (up to 144 weeks). Fifty-three patients, whose median follow-up was 53 weeks, experienced zero bleeds. Most bleeds (94%) among children were trauma-related, whereas 61% of adults sustained spontaneous joint bleeds. Four patients experienced major bleeds, with a fatal outcome in one infant, who also presented with central venous line thrombosis. No other serious adverse events were encountered. Seven patients have decided to stop emicizumab treatment for various reasons. Emicizumab plasma levels increased after emicizumab prophylaxis initiation, and values were maintained during follow-up, in all but one patient, suspected of anti-drug antibodies. A significant reduction of FVIII inhibitor levels was noted among inhibitor patients. TG was increased and sustained yet could not prognosticate bleeding risk.

CONCLUSION

Emicizumab prophylaxis was mostly well tolerated, although 50% of patients experienced breakthrough bleeds. Routine TG monitoring is not obligatory, and further studies are warranted in selected patient populations.

Ex Vivo Prediction of Comprehensive Coagulation Potential Using Simulated Blood Concentrations of Emicizumab in Patients with Acquired Hemophilia A

INTRODUCTION

 Emicizumab prophylaxis improves coagulation function in congenital hemophilia A, regardless of inhibitor presence. We recently reported that emicizumab enhanced the coagulant potentials, ex vivo, in plasmas from patients with acquired hemophilia A (PwAHAs) at diagnosis. However, coagulant effects of emicizumab in PwAHAs during the clinical course remain unclear.

AIM

 To assess ex vivo coagulant effects of emicizumab in PwAHAs during the clinical course.

METHODS/RESULTS

 Blood samples were obtained from 14 PwAHAs on (median) days 0 and 6 during a severe-bleeding phase, and days 27 and 59 during a reduced-bleeding phase with elevated endogenous factor VIII (FVIII) and decreased inhibitor titers. If administered a single dose of 3 or 6 mg/kg, or two doses at 6 mg/kg followed by 3 mg/kg, estimated plasma emicizumab concentrations (10/5/2.5, 20/10/5, and 30/15/7.5 µg/mL on days 0-7/30/60, respectively) could be used to represent potential changes, based on the half-life (T _1/2: ∼30 days). Emicizumab concentrations that covered maximum plasma concentrations of each dosage were used for spiking on day 0. Ex vivo addition of estimated emicizumab to PwAHA's plasma containing endogenous FVIII and/or inhibitor, without and with recombinant (r)FVIIa administration during immunosuppressive therapy, increased the calculated Ad|min1| values, assessed by clot waveform analysis, and their coagulant potentials were below normal levels. Rotational thromboelastometry revealed that ex vivo emicizumab addition resulted in the further improvement of coagulant potentials in whole bloods when combined with rFVIIa administration.

CONCLUSION

 Based on ex vivo and in vitro data, emicizumab has the potential to be effective in clinical situations for PwAHAs.

Outcome measures in Haemophilia: Beyond ABR (Annualized Bleeding Rate)

Options for management of haemophilia are increasing rapidly with completely novel therapeutic approaches that cannot be compared using traditional factor assays. In addition, as prophylaxis regimens have improved, bleeding rates have decreased, and consequently, it is difficult to show an impact of novel therapies on rates of spontaneous bleeding. There is currently an urgent need for a panel of outcome measures to compare therapies that are dissimilar in many essential ways. Conventional objective outcome measures including joint physical examination and joint imaging continue to hold a central importance. Factor assays are essential for evaluation of products derived from native factor genes, but are not applicable to some extended half-life factors or non-factor bypassing agents. Global assays including thrombin generation and chromogenic assays of factor X activation are under investigation for their usefulness in haemophilia assessment. Bleeding rate is a conventional subjective patient-reported outcome that, while decreasing in frequency, is indispensable as an outcome given that the primary manifestation of haemophilia is bleeding. Other patient-reported outcomes such as pain intensity and interference, health-related quality of life and activities and participation are increasingly important to distinguish superior outcomes in comparative trials. This review of outcome measures for haemophilia presents examples of existing outcome measures with an emphasis on their strengths and limitations.

Management of patients with severe haemophilia a without inhibitors on prophylaxis with emicizumab: AICE recommendations with focus on emergency in collaboration with SIBioC, SIMEU, SIMEUP, SIPMeL and SISET

INTRODUCTION

The factor VIII (FVIII)-mimetic bispecific monoclonal antibody, emicizumab, previously approved for prophylaxis in haemophilia A with inhibitors, has been recently licensed in several countries also in patients with severe haemophilia A (PWSHA) without inhibitors. The introduction of this innovative agent requires the development of specific pathways at Haemophilia Treatment Centres (HTC), particularly regarding laboratory testing and treatment of breakthrough bleeds and invasive procedures/surgeries, even more critical when patients are managed by non-specialist professionals. Limited literature data and clinical experience in PWSHA without inhibitors on emicizumab are currently available.

AIM

To promote awareness and overcome these challenges, the Italian Association of Haemophilia Centres (AICE) issued a guidance on the management of PWSHA without inhibitors on emicizumab prophylaxis, focused on emergency and shared with other National Scientific Societies in the field.

METHODS

The document, drafted by an AICE expert panel and approved through online consultation, was further revised by a multidisciplinary working group, including members of 5 haemostasis, laboratory and emergency scientific societies. The final version was approved by the Council of each society.

RESULTS

General recommendations about use of FVIII concentrates for the treatment of bleeding or haemostatic coverage of invasive procedures/surgeries and laboratory monitoring in PWSHA without inhibitors on emicizumab are provided. Specific issues of the management in the emergency room are focused, highlighting the need for direct involvement or formalized supervision by specialist HTC physicians.

CONCLUSIONS

This guidance provides a reference pathway to be implemented in the different healthcare organizations, especially for the challenging emergency management in this setting.

Emicizumab treatment: Impact on coagulation tests and biological monitoring of haemostasis according to clinical situations (BIMHO group proposals)

Emicizumab, a bispecific humanised monoclonal antibody restoring to some extent the function of activated FVIII deficient in haemophilia A, represents a major therapeutic advance in the management of haemophilia A patients. No dosage adjustment is required, which leads to a major change for patients used to regular biological monitoring which is particularly burdensome in the case of substitution therapy. In some circumstances, such as before an invasive procedure or in case of bleeding, biological monitoring will be necessary and emicizumab's interference with haemostasis tests, particularly those based on an activated partial thromboplastin times (aPTT), must be known to best interpret the tests and to select the most appropriate methods to guide therapy. The normalisation of aPTT in patients treated with emicizumab is not sufficient to consider haemostasis as normalised. In the event of administration of FVIII to a patient receiving emicizumab, the determination of FVIII should use a chromogenic method using non-human reagents. Coagulation global tests have been proposed to evaluate the biological response when using bypassing agents in patients treated with emicizumab, but the usefulness must be confirmed. The French group BIMHO presents proposals for biological monitoring of a patient treated with emicizumab according to clinical situations.

Substitution therapy

Emicizumab is a bispecific antibody that recognizes FIX(a)/FX, and mimics FVIIIa cofactor activity. Due to its unique characteristics including longer half-life and subcutaneous injectability, treatment for haemophilia A dramatically improved regardless of the presence of FVIII inhibitor. Protection from pathological change in joints, avoidance of inhibitor development and intra-cranial haemorrhage could be expected by introduction of emicizumab in early childhood. Applications in mild/moderate patients should be also considered. Clinical assessment tool should be standardized; however, since there are limitations to conventional ABR-based assessment. Laboratory monitoring is another practical issue due to the mode of action of emicizumab. Chromogenic assays and global assays could be utilized. The other emicizumab-related practical issue is immune tolerance induction for the inhibitor patients, since ITI remains the only effective means to inhibitor eradication. With the recently introduced Atlanta protocol, emicizumab prophylaxis is given in combination with 50-100 IU/kg FVIII three times a week. A single manuscript has been published, and multiple clinical trials are open to address the efficacy of this strategy. Whether the Atlanta protocol will be fully embraced is yet to be seen, but there is widespread consensus about attempts to tolerize every haemophilia A patient with an inhibitor.

Bispecific Antibodies and Advances in Non-Gene Therapy Options in Hemophilia

Regular prophylaxis has markedly improved the treatment for patients with hemophilia A, especially after the introduction of highly purified factor VIII (FVIII) concentrates. However, frequent intravenous infusions and the development of FVIII inhibitors remain as unsolved difficulties. To overcome these unmet needs, a bispecific antibody mimicking activated FVIII has been developed in Japan. This bispecific antibody, emicizumab, recognizes activated factor IX (FIXa) and activated factor X (FXa), and promotes FIXa-catalyzed activation of FX in the absence of FVIII. Emicizumab initially reacts with FIXa generated by the action of factor VIIa/tissue factor complexes. Subsequently, thrombin generation is enhanced in the presence of higher amounts of FIXa derived from FXIa-dependent mechanisms. Hence, emicizumab-driven FXa and thrombin generation is maintained by a FXI activation loop in the intrinsic coagulation pathway. Reactions downstream of emicizumab are regulated by natural anticoagulants including activated protein C, antithrombin, and tissue factor pathway inhibitor. Phase 3 studies (HAVEN 1-4 and HOHOEMI studies) demonstrated a remarkable reduction in bleeding rates together with a high percentage of patients with zero treated bleeds irrespective of the presence of inhibitors. In general, emicizumab proved to be well tolerated, although isolated thromboembolic and thrombotic microangiopathic complications were observed in the HAVEN 1 studies, and 3 out of a total of 400 patients developed neutralizing antidrug antibodies. In addition, several questions remain to be discussed with respect to open-use clinical practice, including when to start treatment, how to monitor therapy, and optimum dosage for surgical procedures and immune tolerance induction.

An anti-factor IXa/factor X bispecific antibody, emicizumab, improves ex vivo coagulant potentials in plasma from patients with acquired hemophilia A

INTRODUCTION

Acquired hemophilia A (AHA) is caused by autoantibodies against factor (F)VIII, and is characterized by severe, spontaneous bleeding, which can be life-threatening. Emicizumab, an anti-FIXa/FX bispecific antibody, significantly reduces bleeding events in congenital hemophilia A (HA) with and without inhibitors. The known pathophysiological mechanisms and current preclinical data in HA suggest that emicizumab could provide effective treatment for AHA, but the coagulation activities of emicizumab in these patients remain unknown.

AIM

To evaluate the coagulant effects of emicizumab in plasma from AHA patients.

METHODS AND RESULTS

Tissue factor-triggered thrombin generation assays using normal plasma preincubated with anti-FVIII monoclonal antibodies recognizing different epitopes demonstrated that 20 µg/mL emicizumab recovered the depressed peak levels of thrombin generation to 46% to 72%. Further studies were devised, therefore, to simulate the clinical course in AHA patients, including during the acute phase for severe bleeding requiring FVIII-bypassing therapy, and during the subacute/chronic phase with less bleeding. Various concentrations of emicizumab were used to represent the potential changes in plasma levels based on the half-life of the antibody (~30 days). The ex vivo addition of emicizumab to plasma samples from AHA patients (n = 16) increased peak thrombin in all cases, irrespective of the inhibitor epitope specificity. Thrombin generation at 20 and 100 µg/mL emicizumab was restored to (median) 43.9% and 92.2%, respectively. Differences were evident in some cases, however, and recovery rates appeared likely to be greater in patients with type 2 inhibitor than those with type 1.

CONCLUSION

Emicizumab improved ex vivo coagulation potential in plasma from AHA patients.

Emicizumab improves the stability and structure of fibrin clot derived from factor VIII-deficient plasma, similar to the addition of factor VIII

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.

Successful Perioperative Combination of High-Dose FVIII Therapy Followed by Emicizumab in a Patient with Hemophilia A with Inhibitors

We managed perioperative hemostasis for a 72-year-old man with hemophilia A and low inhibitor titers (3 BU/mL), who underwent osteosynthesis for supracondylar fracture of the left humerus. He was treated perioperatively using the combination of high doses of factor VIII (FVIII) with recombinant human Factor VIII Fc fusion protein (rFVIIIFc), followed by emicizumab. On the day of surgery (day 0), he was administered bolus infusion of 150 IU/kg rFVIIIFc, followed by continuous infusion at a dose of 4 IU/kg/h. Emicizumab, 3 mg/kg, was injected subcutaneously once a week, on days 5, 12, 19, and 26. Inhibitors were detected on day 6 at a titer of 4 BU/mL and FVIII:C decreased to below assay sensitivity limits on day 10. The rate of increase in inhibitor titers was high, with inhibitors increasing to 343.4 BU/mL on day 14. The transition of thrombin production by thrombin generation assay (TGA) showed temporary decrease in thrombin production on day 7, although it was restored by day 10, i.e., five days after commencement of emicizumab therapy. Rotational thromboelastometry displayed consistent results with TGA, showing that clotting time was prolonged and the alpha angle decreased to less than measurable levels on day 6, although they were improved by day 10. There were no bleeding-related events or other adverse events throughout the perioperative period. In conclusion, emicizumab was effective for the management of perioperative hemostasis after development of an anamnestic response in a patient with hemophilia A with inhibitors. Combination therapy with high doses of FVIII followed by emicizumab could be a workable alternative for patients with hemophilia A with inhibitors.