A multicenter, open-label phase 3 study of emicizumab prophylaxis in children with hemophilia A with inhibitors

Pediatric Rare Diseases Development in the Pharmaceutical Industry: An International Consortium for Innovation and Quality in Pharmaceutical Development, Clinical Pharmacology Leadership Group-Pediatrics Working Group, Rare Diseases Subteam Whitepaper Examining the Current Landscape and Recommendations for the Future

Many new opportunities surround rare pediatric disease drug development, thanks to key advances in regulatory thinking and in the scientific community. As rare disease drug development brings challenges to the developers in terms of limited understanding of natural history, heterogeneity in drug response, as well as difficulty recruiting patients in pivotal trials, there has never been a greater need for quantitative integration. To understand how International Consortium for Innovation and Quality in Pharmaceutical Development (IQ) member companies approach pediatric rare disease drug development, the rare pediatric subteam of the Clinical Pharmacology Leadership Group (CPLG) sponsored Pediatrics Working Group conducted a baseline survey to assess the four main pillars of this quantitative innovation, namely, biomarkers and surrogate end points, statistical methodologies, model-informed drug development, as well as public-private partnerships. The survey was administered by IQ and yielded 13 evaluable responders from represented companies. This article presents the key findings from this baseline identifying survey, highlighting the key blind spots, and providing insightful expert opinions to address those gaps. In summary, we call an urgent attention to the community on the opportunities to enhance integration and within-industry learnings from this analysis on aspects related to platform studies, end-to-end quantitative integration, and sharing of trial-level placebo data for better understanding of disease progression and more efficient trial designs. We collectively hope that these findings will stimulate discussion and debate around cross-industry sharing and collaboration to better delineate principles and further enhance the efficiency of rare pediatric disease drug development.

Joint health and pain in the changing hemophilia treatment landscape

INTRODUCTION

Hemophilia is an inherited bleeding disorder. Bleeding, and in particular joint hemorrhage results in chronic arthropathy and disability. Acute and chronic pain are frequent and limit activity and participation and result in decreased health-related quality of life. Remarkable progress has been made in the diagnosis and treatment of hemophilia but bleeding continues to prove recalcitrant to currently available treatments and joint disease remains problematic. Physiotherapy and pain management are mainstays of current multidisciplinary integrated care of people with hemophilia (PWH). The focus of this review is on preservation of joint health in the era of new and innovative therapies.

AREAS COVERED

A search of the PubMed Central was conducted on 1 February 2024 using the MeSH Major Topic terms identified as keywords for the manuscript. This review will highlight what is known and unknown about joint bleeding and arthropathy, including insights on pain as a related complication.

EXPERT OPINION

Recent advances in therapeutic interventions aimed at promoting healthy joints in PWH will be discussed, including both the pharmacological treatment landscape and related strategies to promote joint health.

Shifting Paradigms and Arising Concerns in Severe Hemophilia A Treatment

The management of hemophilia A has undergone a remarkable revolution, in line with technological advancement. In the recent past, the primary concern associated with Factor VIII (FVIII) concentrates was the risk of infections, which is now almost resolved by advanced blood screening and viral inactivation methods. Improving patients' compliance with prophylaxis has become a key focus, as it can lead to improved health outcomes and reduced health care costs in the long term. Recent bioengineering research is directed toward prolonging the recombinant FVIII (rFVIII) coagulant activity and synthesising higher FVIII yields. As an outcome, B-domain deleted, polyethylene glycolated, single-chain, Fc-fused rFVIII, and rFVIIIFc-von Willebrand Factor-XTEN are available for patients. Moreover, emicizumab, a bispecific antibody, is commercially available, whereas fitusiran and tissue factor pathway inhibitor are in clinical trial stages as alternative strategies for patients with inhibitors. With these advancements, noninfectious complications, such as inhibitor development, allergic reactions, and thrombosis, are emerging concerns requiring careful management. In addition, the recent approval of gene therapy is a major milestone toward a permanent cure for hemophilia A. The vast array of treatment options at our disposal today empowers patients and providers alike, to tailor therapeutic regimens to the unique needs of each individual. Despite significant progress in modern treatment options, these highly effective therapies are markedly more expensive than conventional replacement therapy, limiting their access for patients in developing countries.

Reduced doses of emicizumab achieve good efficacy: Results from a national-wide multicentre real-world study in China

INTRODUCTION

Reduced doses of emicizumab improve the affordability among patients in developing countries. However, the relationship between variant dose selection and efficacy in the real world of China is still unclear.

AIM

This study aimed to investigate the efficacy and safety of emicizumab especially in those on reduced dose regimens in a real-world setting.

METHODS

We carried out a multicentre study from 28 hospitals between June 2019 and June 2023 in China and retrospectively analysed the characteristics including demographics, diagnosis, treatment, bleeding episodes, and surgical procedures.

RESULTS

In total, 127 patients with haemophilia A, including 42 with inhibitors, were followed for a median duration of 16.0 (IQR: 9.0-30.0) months. Median age at emicizumab initiation was 2.0 (IQR: 1.0-4.0) years. Median (IQR) consumption for loading and maintenance was 12.0 (8.0-12.0) and 4.2 (3.0-6.0) mg/kg/4 weeks, respectively. While on emicizumab, 67 (52.8%) patients had no bleeds, whereas 60 (47.2%) patients had any bleeds, including 26 with treated bleeds. Compared to previous treatments, patients on emicizumab had significantly decreased annualized bleeding rate, annualized joint bleeding rate, target joints and intracerebral haemorrhage. Different dosages had similar efficacy except the proportion of patients with treated spontaneous bleeds and target joints. Adverse events were reported in 12 (9.4%) patients. Postoperative excessive bleeding occurred following two of nine procedures.

CONCLUSION

This is the largest study describing patients with HA receiving emicizumab prophylaxis on variant dose regimens in China. We confirmed that nonstandard dose is efficacious and can be considered where full-dose emicizumab is ill affordable.

Transitioning from emicizumab prophylaxis to valoctocogene roxaparvovec gene therapy: A simulation study for individuals with severe haemophilia A

INTRODUCTION

Valoctocogene roxaparvovec, a gene therapy evaluated in the phase 3 GENEr8-1 trial, supports endogenous factor VIII (FVIII) production to prevent bleeding in people with severe haemophilia A. Individuals receiving emicizumab, an antibody mimicking the function of activated FVIII, were excluded from GENEr8-1 enrolment since emicizumab was an investigational therapy at the time of trial initiation.

AIM

Utilize pharmacokinetic simulations to provide guidance on best practices for maintaining haemostatic control while transitioning from emicizumab prophylaxis to valoctocogene roxaparvovec.

METHODS

To estimate bleeding risk at weekly intervals following valoctocogene roxaparvovec infusion, a published emicizumab pharmacokinetic model was used to simulate emicizumab concentrations and merged with FVIII activity time-course data for participants in GENEr8-1. The analysis investigated three approved emicizumab dosing regimens for two transition scenarios that varied whether the last dose of emicizumab was administered on the same day or 4 weeks after valoctocogene roxaparvovec infusion.

RESULTS

Simulations demonstrated administering the last emicizumab dose the day of valoctocogene roxaparvovec infusion and 4 weeks after offered similar levels of haemostatic control, and bleeding risk was similar for all emicizumab dosing regimens. An algorithm was developed to provide guidance for discontinuation of emicizumab. Theoretical cases based on GENEr8-1 participants are presented to illustrate how decisions may vary among individuals.

CONCLUSION

Pharmacokinetic simulations demonstrated no clinically meaningful difference in bleeding risk caused by decaying emicizumab levels and rising gene therapy-derived endogenous FVIII for all examined emicizumab doses and dosing regimens. Therefore, multiple approaches can safely transition individuals from emicizumab prophylaxis to valoctocogene roxaparvovec.

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.

Single centre experience of the use of emicizumab in previously untreated and minimally treated patients under 18 months of age

Emicizumab has revolutionised haemophilia A treatment landscape and significantly reduced treatment burden, particularly in the paediatric population. We conducted a retrospective study, focused on infants aged ≤18 months with severe haemophilia A. The study included 16 patients, with a median age of 8.2 months and median treatment duration of 61.6 weeks. Before commencing emicizumab, six patients were minimally treated with ≤5 exposure days while 10 were previously untreated patients. Notably, all patients had no inhibitors at baseline, and none developed new inhibitors during the study period. Emicizumab was well tolerated, with no observed side effects or major bleeding events.

Emicizumab promotes factor Xa generation on endothelial cells

BACKGROUND

Until recently, the treatment of hemophilia A relied on factor (F)VIII replacement. However, up to one-third of patients with severe hemophilia A develop neutralizing alloantibodies that render replacement therapies ineffective. The development of emicizumab, a bispecific antibody that partially mimics FVIIIa, has revolutionized the treatment of these patients. However, the use of an activated prothrombin complex concentrate [FEIBA (Takeda)] to treat breakthrough bleeding in patients on emicizumab has been associated with thrombotic complications including a unique microangiopathy.

OBJECTIVES

We hypothesized that the thrombotic complications observed with the combination of emicizumab and FEIBA might be due to excessive expression of procoagulant activity on the surface of endothelial cells.

METHODS

We examined the ability of emicizumab to promote FX activation on endothelial cells using 2 cell culture models.

RESULTS

We found that endothelial cells readily support emicizumab-mediated activation of FX by FIXa. The level of FXa generation depends on the concentration of available FIXa. The addition of FEIBA to emicizumab increased FXa generation in a dose-dependent manner on endothelial cells in both models. The rate of FXa generation was further enhanced by endothelial cell activation. However, unlike emicizumab, we found limited FXa generation in the presence of FVIII(a), which followed a significant lag time and was not dependent on FIXa concentration under these conditions.

CONCLUSION

Emicizumab promotes FXa generation on the surface of endothelial cells, which is markedly enhanced in the presence of FEIBA. These findings demonstrate a potential mechanism for the thrombotic complications seen with the combined use of emicizumab and FEIBA.

Emicizumab prophylaxis in people with hemophilia A and inhibitors: a systematic review and meta-analysis

BACKGROUND

Until recently, the treatment of people with hemophilia A and inhibitors (PwHAi) was based on the use of bypassing agents (BPA). However, the advent of emicizumab as prophylaxis has demonstrated promising results.

OBJECTIVES

We aimed to compare the bleeding endpoints between PwHAi on BPA and those on emicizumab prophylaxis.

DESIGN AND SETTING

Systematic review of interventions and meta-analysis conducted at the Universidade Federal de Goiás, Goiânia, Goiás, Brazil.

METHODS

The CENTRAL, MEDLINE, Scopus, and LILACS databases were searched on February 21, 2023. Two authors conducted the literature search, publication selection, and data extraction. The selected publications evaluated the bleeding endpoints between PwHAi on emicizumab prophylaxis and those on BPA prophylaxis. The risk of bias was evaluated according to the Joanna Briggs Institute criteria. A meta-analysis was performed to determine the annualized bleeding rate (ABR) for treated bleeds.

RESULTS

Five publications (56 PwHAi) were selected from the 543 retrieved records. Overall, bleeding endpoints were lower during emicizumab prophylaxis than during BPA prophylaxis. All the publications had at least one risk of bias. The only common parameter for the meta-analysis was the ABR for treated bleeds. During emicizumab prophylaxis, the ABR for treated bleeds was lower than during BPA prophylaxis (standard mean difference: -1.58; 95% confidence interval -2.50, -0.66, P = 0.0008; I2 = 68.4%, P = 0.0031).

CONCLUSION

Emicizumab was superior to BPA in bleeding prophylaxis in PwHAi. However, both the small population size and potential risk of bias should be considered when evaluating these results.

SYSTEMATIC REVIEW REGISTRATION

CRD42021278726, https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=278726.

The effects of emicizumab on in vitro coagulation and fibrinolysis parameters in patients with disseminated intravascular coagulation with and without addition of anti-FVIII antibody

BACKGROUND

Emicizumab (Emi) is used as haemostatic prophylaxis for patients with haemophilia A (PwHA). Disseminated intravascular coagulation (DIC) is a condition characterized by persistent systemic activation of coagulation, but there is yet no information on coagulation and fibrinolysis potentials in Emi-treated PwHA with DIC.

AIM

To examine the effect of Emi on coagulation and fibrinolysis potentials in HA-model DIC plasmas.

METHODS

Plasma from a patient with sepsis-DIC (seven patients) was treated with anti-factor (F)VIII monoclonal antibody (HA-model DIC plasma) and incubated with Emi (50 µg/mL). The plasma was then assessed using clot-fibrinolysis waveform analysis (CFWA). Coagulation and fibrinolysis parameters were expressed as ratios relative to normal plasma (|min1|-ratio and |FL-min1|-ratio, respectively).

PATIENTS AND RESULTS

In case 1, coagulant potential was slightly high and fibrinolytic potential was extremely low, presenting a coagulant-dominant state (|min1|-ratio/|FL-min1|-ratio: 1.1/.38). In cases 2-5, fibrinolytic potential was not suppressed, but there were marked hypercoagulant potentials, indicating relative coagulant-dominant states. In case 6, coagulant and fibrinolytic potentials were increased but well balanced (|min1|-ratio/|FL-min1|-ratio: 1.38/1.28). In case 7, both potentials were severely deteriorated in not only CFWA but also the thrombin/plasmin generation assay. The addition of Emi into the HA-model DIC plasmas increased |min1|-ratio values in all cases, but the coagulant potentials did not exceed the initial ones (DIC plasma before treatment with anti-FVIII antibody).

CONCLUSIONS

The presence of Emi in the HA-model DIC plasma improved coagulation potentials, but did not increase coagulation potentials beyond those of DIC plasma in non-HA states.

Emicizumab is well tolerated and effective in people with congenital hemophilia A regardless of age, severity of disease, or inhibitor status: a scoping review

Background

With the treatment landscape continually evolving, it is vital that the hemophilia community have an overview of all published data for approved therapies, such as emicizumab, to support shared decision making.

Objectives

To bring together the clinical and real-world data for emicizumab use in people with congenital hemophilia A, regardless of age, disease severity, or factor VIII inhibitor status. Key focus areas were safety, efficacy, and quality of life (QoL).

Methods

This scoping review used citation databases (PubMed, Embase, and the Cochrane Library) and manual searches of abstract books. Publications reporting original data for emicizumab in people with hemophilia A, published in English after December 2014, and reporting select endpoints were included. This narrative synthesis focused on zero bleeds, treated annualized bleeding rate (ABR), adverse events, and QoL measures.

Results

Overall, 97 publications were included (cut-off: August 9, 2022). Treated ABR remained low (calculated mean and median treated ABRs ranged between 0.7-1.3 and 0.0-1.4, respectively), and the median percentage of people with zero treated bleeds was 66.7%. The proportion of people experiencing treatment-related adverse events ranged from 0.0% to 60.0%; most were injection-site reactions. Across 37 publications reporting on safety and enrolling >2300 individuals, 11 thrombotic events and 4 thrombotic microangiopathies were reported. Data from well-established tools show QoL benefits with emicizumab.

Conclusion

This scoping review consolidates the global published experience for emicizumab in people with hemophilia A and supports the fact that emicizumab has an acceptable safety profile, is effective and efficacious in bleed prevention, and is associated with improvements in QoL.

Bleeding control improves after switching to emicizumab: Real-world experience of 177 children in the PedNet registry

INTRODUCTION

Despite the rapid uptake of emicizumab in the paediatric haemophilia A (HA) population, real-world data on the safety and efficacy is limited.

AIM

To report on bleeding and safety in paediatric patients receiving emicizumab prophylaxis.

METHODS

Data were extracted from the multicentre prospective observational PedNet Registry (NCT02979119). Children with haemophilia A, and ≥50 FVIII exposures or inhibitors present receiving emicizumab maintenance therapy were analysed. Data were summarized as medians with interquartile range (IQR, P25-P75). Mean (95% confidence interval (CI)), annualized (joint) bleeding rate (A(J)BR) during emicizumab and ≤2 years before emicizumab prophylaxis were modelled and compared using negative binomial regression.

RESULTS

Total of 177 patients started emicizumab at median 8.6 years (IQR 4.8-13.1), most had no FVIII inhibitors (64%). Follow up before emicizumab was median: 1.68 years (IQR: 1.24-1.90) and during emicizumab: 1.32 years (IQR: .94-2.11). In patients without inhibitors, mean ABR reduced after starting emicizumab from 2.41 (CI 1.98-2.95) to 1.11 (CI .90-1.36, p < .001), while AJBR reduced from.74 (CI .56-.98) to.31 (CI .21-.46, p < .001). Concordantly, in patients with inhibitors, mean ABR reduced from 5.08 (CI 4.08-6.38) to .75 (CI .56-1.01, p < .001), while AJBR reduced from 1.90 (CI 1.42-2.58) to .34 (CI .21-.56, p < .001). Five emicizumab-related adverse events were reported (3% of the cohort), including one patient with antidrug antibodies.

CONCLUSION

This study showed improved bleeding control compared to previous treatment and a favourable safety profile during emicizumab therapy in paediatric haemophilia A patients.

Activated protein C resistance in the copresence of emicizumab and activated prothrombin complex concentrates

Background

Venous thromboembolic events have been reported in persons with hemophilia A who received emicizumab and activated prothrombin complex concentrate (APCC) concomitantly, but the relevant mechanism(s) remains unclear. We speculated that activated protein C (APC) and antithrombin (AT) resistance might be associated with these adverse events.

Objectives

To investigate APC and AT resistance in factor (F)VIII-deficient (FVIIIdef) plasma in the presence of emicizumab and APCC.

Methods

In pooled normal plasma or FVIIIdef plasma samples mixed with emicizumab (50 μg/mL) and FVIII-bypassing agents, including recombinant FVIIa (2.2 μg/mL), APCC (1.3 IU/mL), or plasma-derived FVIIa/FX (1.5 μg/mL), the suppression effect of AT (0-2.4 μM) and APC (0-16 nM) was assessed by tissue factor-triggered thrombin generation assay. The APC effects in FVIIIdef plasma with the copresence of emicizumab, FII (1.3 μM), and/or FIXa (280 pM) were also examined.

Results

The AT resistance in emicizumab and each bypassing agent was not observed. Moreover, APC dose-dependent suppression effect was observed in pooled normal plasma or FVIIIdef plasma mixed with emicizumab and recombinant FVIIa or plasma-derived FVIIa/FX. However, APC-catalyzed inactivation had little effect on thrombin generation assay potential in FVIIIdef plasma spiked with emicizumab and APCC. The addition of FIXa to emicizumab in FVIIIdef plasma could lead to partial APC resistance. Furthermore, FVIIIdef plasma spiked with emicizumab, FIXa, and FII was markedly resistant to APC-mediated inactivation.

Conclusion

FII and FIXa in APCCs were key clotting factors for APC resistance in FVIIIdef plasma supplemented with emicizumab and APCCs. The APC resistance in persons with hemophilia A receiving emicizumab and APCC may contribute to venous thromboembolic events.

Emicizumab: the hemophilia A game-changer

In hemophilia, the unmet needs regarding adherence to prophylaxis and lack of effective long-term prophylaxis regimens, especially in patients with inhibitors, led to the production of emicizumab, the first non-factor medicine for subcutaneous administration in patients with severe and moderate hemophilia A with or without factor VIII inhibitors. This review describes the research steps behind the development of this game-changing medication as well as its success in the prophylaxis of bleeding episodes, as witnessed by the results of pivotal clinical trials but also by real-life use in the frame of a still expanding global market. We also discuss potential and actual adverse events and the nuances related to clinical use, such as laboratory monitoring, development of neutralizing antidrug antibodies, risk of thrombosis/hypercoagulability and role in the management of surgical operations. The potential of emicizumab to prevent bleeding in other congenital and acquired coagulation disorders is also outlined.

Emicizumab prophylaxis in infants with hemophilia A (HAVEN 7): primary analysis of a phase 3b open-label trial

ABSTRACT

Subcutaneous emicizumab enables prophylaxis for people with hemophilia A (HA) from birth, potentially reducing risk of bleeding and intracranial hemorrhage (ICH). HAVEN 7 (NCT04431726) is the first clinical trial of emicizumab dedicated to infants, designed to investigate the efficacy, safety, pharmacokinetics, and pharmacodynamics of emicizumab in those aged ≤12 months with severe HA without factor VIII (FVIII) inhibitors. Participants in this phase 3b trial received emicizumab 3 mg/kg maintenance dose every 2 weeks for 52 weeks and are continuing emicizumab during the 7-year long-term follow-up. Efficacy end points included annualized bleed rate (ABR): treated, all, treated spontaneous, and treated joint bleeds. Safety end points included adverse events (AEs), thromboembolic events (TEs), thrombotic microangiopathies (TMAs), and immunogenicity (anti-emicizumab antibodies [ADAs] and FVIII inhibitors). At primary analysis, 55 male participants had received emicizumab (median treatment duration: 100.3; range, 52-118 weeks). Median age at informed consent was 4.0 months (range, 9 days to 11 months 30 days). Model-based ABR for treated bleeds was 0.4 (95% confidence interval, 0.30-0.63), with 54.5% of participants (n = 30) having zero treated bleeds. No ICH occurred. All 42 treated bleeds in 25 participants (45.5%) were traumatic. Nine participants (16.4%) had ≥1 emicizumab-related AE (all grade 1 injection-site reactions). No AE led to treatment changes. No deaths, TEs, or TMAs occurred. No participant tested positive for ADAs. Two participants were confirmed positive for FVIII inhibitors. This primary analysis of HAVEN 7 indicates that emicizumab is efficacious and well tolerated in infants with severe HA without FVIII inhibitors.

FRONTIER1: a partially randomized phase 2 study assessing the safety, pharmacokinetics, and pharmacodynamics of Mim8, a factor VIIIa mimetic

BACKGROUND

Mim8 (denecimig) is a factor VIII (FVIII) mimetic bispecific antibody in development for the treatment of hemophilia. Data from the phase 1 part of FRONTIER1 (EudraCT: 2019-000465-20, NCT04204408, and NN7769-4513) suggested that Mim8 was well tolerated in healthy participants and exhibited pharmacokinetic (PK) properties consistent with dose proportionality.

OBJECTIVES

The partially randomized, phase 2, multiple ascending dose (MAD) part of FRONTIER1 aimed to evaluate the safety, PK, pharmacodynamics (PD), and exploratory efficacy of Mim8 in participants with hemophilia A with or without FVIII inhibitors.

METHODS

The MAD part of FRONTIER1 consisted of 42 participants, assigned to 5 cohorts, with participants in cohorts 3 and 4 randomized 1:1 to dosing weekly or every 4 weeks, respectively. Four of the 42 participants (9.5%) had FVIII inhibitors prior to study enrolment. The primary endpoint was treatment-emergent adverse events (TEAEs). PK and PD were evaluated by Mim8 plasma concentration and thrombin generation, respectively. Exploratory efficacy was assessed via the number of treated bleeds. Safety and PD parameters were also evaluated from an exploratory cohort treated with emicizumab.

RESULTS

Mim8 was well tolerated, with 1 serious TEAE (anxiety-related chest pain) deemed unrelated to Mim8. There was no dose dependency on the number, causality, type, or severity of TEAEs. PK/PD properties supported weekly to monthly dosing approaches, and few participants experienced treated bleeds beyond the lowest dose cohort (1 in cohorts 2 and 3, and 3 in cohort 5).

CONCLUSION

These data support the continued clinical development of Mim8, and FRONTIER1 has proceeded onto an extension phase.

Emicizumab prophylaxis in infants: Single-centre experience

The hallmark of haemophilia A (HA) therapy is prophylaxis, aimed at spontaneous bleeding prevention. Emicizumab provides a viable alternative to intravenous factor replacement therapy. However, data on its use in infants are limited. This single-centre open arm prospective study reports on emicizumab prophylaxis in infants. We included severe HA patients under 1 year who started emicizumab prophylaxis since 2018, with longitudinal follow-up. The study collected data on demographics, clinical and laboratory variables, the occurrence of bleeding events, surgeries and treatment outcomes. Of the 27 enrolled infants, whose median age at prophylaxis initiation was 7 months, 24 primarily choose to start emicizumab therapy (3/27 switched from FVIII prophylaxis due to development of FVIII inhibitors). The median age for prophylaxis initiation decreased to 3 months in 2023. Following emicizumab initiation, the median calculated ABR decreased, and no intracranial haemorrhages were observed. Thrombin generation showed a significant improvement in peak height and endogenous thrombin potential at steady state after a loading period. Our study highlights a shift towards early prophylaxis in the era of non-replacement therapies. It underscores the need for continuous evaluation and refinement of treatment approaches, emphasizing personalized care and diligent monitoring in the evolving field of paediatric haemophilia care.

The importance and evolution of bleeding disorder registries

Registries are excellent sources of data to address questions that are typically not evaluated in randomized clinical trials, including natural history, disease prevalence, treatment approaches and adverse events, and models of care. Global and regional registries can provide data to identify differences in outcomes and in haemophilia care between countries, economic settings, and regions, while facilitating research and data sharing. In this manuscript, we highlight five bleeding disorder registries: Country registries from Australia and China, Paediatric Network on Haemophilia Management (PedNet) data on children who have received emicizumab, data from the European Haemophilia Safety Surveillance (EUHASS) system, and data on women and girls with haemophilia from the World Federation of Haemophilia (WFH) registries. Data from these and other bleeding disorder registries have been and will continue to be used to advance patient care, understand treatment patterns and adverse reactions, and identify areas of increased need and focus.

Management of Urgent Bleeding in Patients with Hemophilia A: Focus on the Use of Emicizumab

Management of patients with hemophilia A (HA) requires the knowledge and experience of specialized health care professionals. However, these patients may need to be attended in emergencies, outside the referral hospital, where health care professionals do not know about hemophilia and/or new innovative treatments. This study aimed to develop a simple and practical algorithm that could be used in emergency situations by nonspecialized treaters in HA and bleeding with or without factor VIII (FVIII) inhibitors under emicizumab prophylaxis. A group of experts agreed on a simple algorithm, easy to operate, adapted from previous international guidelines, and based on their clinical experience. The proposed algorithm starts with identifying the patient, confirming the diagnosis of HA, prophylaxis with emicizumab, and/or use of other treatments. After stabilizing the patient and stratifying the bleeding risk, the patient is managed according to the presence/absence of FVIII inhibitors. Patients without FVIII inhibitors should receive FVIII concentrate. Dose and follow-up depend on bleeding localization and severity. Patients with FVIII inhibitors should preferably receive recombinant activated factor VII as bypass agent. A basic coagulation assay, FVIII assessment, and FVIII inhibitors detection assays are necessary in an emergency. However, these tests should be interpreted with caution and appropriately chosen, as emicizumab may alter the results. The management of patients with HA is challenging in emergency situations, especially if they are treated with new agents. Nonspecialized in coagulopathies health care professionals have limited understanding of the disease, highlighting the need for an algorithm to assist them in making informed decisions.

Benefits and risks of non-factor therapies: Redefining haemophilia treatment goals in the era of new technologies

INTRODUCTION

Over the last decades progress in haemophilia treatment has been remarkable and prophylaxis with clotting factor concentrates in haemophilia A and B has been established as the standard of care in individuals with haemophilia and a severe bleeding phenotype. Besides clotting factor products with prolonged half-life non-factor therapies were developed which enable prophylaxis via subcutaneous administration. Factor VIIIa mimetics like emicizumab facilitate the coagulation pathway and are used in routine clinical practice for indivdiduals with haemophilia A. Rebalancing therapeutic agents like fitusiran, concizumab, marstacimab and serpin PC block the anticoagulant pathway and clinical trials using these products in individuals with haemophilia A and B are ongoing.

AIM AND METHODS

A narrative review to asess the benefits and risks of non-factor therapies taking in to account re-defined haemophilia treatment goals.

RESULTS

Prophylaxis for prevention of bleeds using non-factor products by subcutaneous administration is effective and results in reductions of bleeding episodes in individuals with haemophilia A or B with and without inhibitors. The treatment with emicizumab showed tolerable safety both in clinical trials and long-term real-world observations with few thrombotic events. In some clinical trials with rebalancing therapies (fitusiran and concizumab) thrombotic events occurred. Monitoring of the haemostatic function of novel therapies especially with concomitant haemostatic treatment is not yet established.

CONCLUSION

With the advent of novel therapeutic agents including factor concentrates with ultra-long half-life and improved FVIIIa mimetics aimed at raising the bar of protection into the non-hemophilic range redefinition of haemophilia treatment goals is eagerly needed.

Expert Opinions on the Management of Hemophilia A in India: The Role of Emicizumab

Hemophilia A (HA) is a genetic disorder of hemostasis associated with a deficiency or reduced activity of clotting factor VIII (FVIII). This disorder remains unacceptably underdiagnosed in India. Early diagnosis and appropriate management of HA can substantially prevent morbidity and mortality. Currently, HA is managed with regular replacement therapy using standard or extended half-life FVIII concentrates or non-factor drug products. The challenges associated with FVIII concentrates include plateauing of drug effect, issues with its administration and adherence to treatment, breakthrough bleeds, and the development of inhibiting antibodies against administered clotting factors. Emicizumab is a bispecific antibody, launched in India in April 2019, for managing patients with HA. To investigate the role of emicizumab in Indian patients with HA, opinions were sought from 13 eminent hematologists and experts from India on the effectiveness of emicizumab in preventing all bleeds, spontaneous bleeds, perioperative bleeds, and intracranial hemorrhage; resolving target joints; and reducing the rate of hospitalizations and fatality associated with HA in children and adults, with or without inhibitors. The benefits of emicizumab over traditional FVIII concentrates include the subcutaneous route of delivery, less frequent dosing, and a lack of inhibitor development, in addition to providing sustained hemostasis without in-depth monitoring. It is a safe and effective management option for all HA patients, especially for patients with certain archetypes, such as those with inhibitors, those with high annualized bleed rates, those living far away from hemophilia care centers, pediatric patients and infants with intravenous access challenges, and those with a history of life-threatening bleeding events.

Haemophilia in the era of novel therapies: Where do inhibitors feature in the new landscape?

INTRODUCTION

The advent of therapeutic recombinant factor VIII (FVIII) and factor IX (FIX) protein infusions revolutionized the care of persons with haemophilia in the 1990s. It kicked off an era with the increasing use of prophylactic factor infusions for patients and transformed conversations around the ideal trough activity levels as well as the ultimate goals in tailored, individualized care. Our knowledge surrounding the immunologic basis of inhibitor development and treatment derives from a time when patients were receiving frequent factor infusions and focused on immune tolerance induction following inhibitor development.

DISCUSSION

More recently, care was revolutionized again in haemophilia A with the approval of emicizumab, a bispecific antibody mimicking activated FVIII function, to prevent bleeding. The use of emicizumab prophylaxis has resulted in a significantly slower accumulation of factor exposure days and continued effective prophylaxis in the case of inhibitor development. While emicizumab is effective at reducing the frequency of bleeding events in patients with haemophilia A, management of breakthrough bleeds, trauma, and surgeries still requires additional treatment. Ensuring that FVIII is a therapeutic option, particularly for life-threatening bleeding events and major surgeries is critical to optimizing the care of persons with haemophilia A. Other novel non-factor concentrate therapies, including rebalancing agents, will dramatically change the landscape for persons with haemophilia B with inhibitors.

CONCLUSION

This review discusses the changing landscape regarding the timing of inhibitor development and management strategies after inhibitor development, stressing the importance of education across the community to continue to vigilantly monitor for inhibitors and be prepared to treat persons with inhibitors.

Safety of recombinant activated factor VII for treatment of breakthrough bleeds in patients with congenital haemophilia A and inhibitors receiving emicizumab prophylaxis: Review of the real-world evidence

BACKGROUND

Emicizumab is used as a subcutaneous prophylaxis for prevention of bleeding episodes in patients with haemophilia A (HA) with and without inhibitors. While low bleeding rates were observed in clinical trials, patients still experience breakthrough bleeds (BTBs) with emicizumab in the real-world. Current guidelines recommend use of recombinant activated factor VII (rFVIIa) for treatment of BTBs in patients with inhibitors. Due to thrombotic events observed in the HAVEN 1 study, activated prothrombin complex concentrate (aPCC) should be used with caution.

OBJECTIVES

The objective of this review is to identify and discuss real-world data on the frequency of BTBs and the safety of concomitant rFVIIa use in patients with inhibitors on emicizumab prophylaxis.

METHODS

A search of the following databases was conducted on 15 July 2022: BIOSIS Previews® , Current Contents Search® , Embase® , MEDLINE® . Search terms included 'real world', 'haemophilia A', and 'emicizumab'.

RESULTS AND CONCLUSIONS

Eleven relevant publications were identified (seven original research articles and four congress abstracts). The frequency of BTBs specifically for HA patients with inhibitors was described in three publications with 5%-56% patients on emicizumab reporting ≥1 bleeding episode. Treatment of these BTBs appeared to be managed according to relevant guidelines. Importantly, no thrombotic complications occurred during concomitant rFVIIa use. Due to the nature of real-world studies, direct comparison of the results between studies is limited. However, real-world data show that BTBs in inhibitor patients during emicizumab prophylaxis can be safely treated with rFVIIa.

Emicizumab is efficacious in people with hemophilia A with comorbidities aged ≥50 years: analysis of 4 phase III trials

Background

The treatment of older people with hemophilia A (HA) can be complicated by comorbidities.

Objectives

This post hoc analysis evaluates the efficacy and safety of emicizumab in people with HA aged ≥50 years with cardiovascular (CV) risk factors or HIV and/or hepatitis C virus (HCV) infection.

Methods

The HAVEN 1 (NCT02622321), HAVEN 3 (NCT02847637), HAVEN 4 (NCT03020160), and STASEY (NCT03191799) studies enrolled adults/adolescents with severe HA. Participants were categorized as having a comorbidity if they had any CV risk factors (including history of CV disease, hypertension, diabetes, hyperlipidemia, prior stroke, or obesity), HIV, and/or HCV infection. Efficacy and safety outcomes were compared by age (<50 vs ≥50 years).

Results

Of 504 participants at data cutoff, 408 were aged <50 years and 96 were aged ≥50 years. In people with HA aged <50 years, 26.7% had ≥1 CV risk factor and 29.4% had HIV and/or HCV infection. In people with HA aged ≥50 years, 72.9% had ≥1 CV risk factor and 74.0% had HIV and/or HCV infection. The mean (95% CI) annualized bleed rate for treated bleeds was 1.29 (0.07-6.06) for people with HA aged <50 years and 1.82 (0.19-6.93) for people with HA aged ≥50 years. No significant differences in annualized bleed rates were observed for those with comorbidities compared with those without. Safety outcomes were similar regardless of age.

Conclusion

This pooled analysis suggests that emicizumab efficacy and safety in people with HA aged ≥50 years with CV and HIV/HCV comorbidities were consistent with those in people with HA aged <50 years enrolled in the HAVEN 1, 3, and 4 and STASEY studies.

Nothing short of a revolution: Novel extended half-life factor VIII replacement products and non-replacement agents reshape the treatment landscape in hemophilia A

Hemophilia A, an X-linked genetic disorder, is characterized by a deficiency or dysfunction of clotting Factor VIII. The treatment landscape has substantially changed by introducing novel extended half-life factor VIII (EHL-FVIII) replacement therapies such as efanesoctocog Alfa and non-factor replacement therapy such as emicizumab. These agents signal a shift from treatments requiring multiple weekly infusions to advanced therapies with long half-lives, offering superior protection against bleeding and improving patient adherence and quality of life. While EHL-FVIII treatment might lead to inhibitor development in some patients, non-factor replacement therapy carries thrombotic risks. Therefore, ongoing research and the generation of robust clinical evidence remain vital to guide the selection of optimal and cost-effective first-line therapies for hemophilia A patients.

Non-clotting factor therapies for preventing bleeds in people with congenital hemophilia A or B

BACKGROUND

Management of congenital hemophilia A and B is by prophylactic or on-demand replacement therapy with clotting factor concentrates. The effects of newer non-clotting factor therapies such as emicizumab, concizumab, marstacimab, and fitusiran compared with existing standards of care are yet to be systematically reviewed.

OBJECTIVES

To assess the effects (clinical, economic, patient-reported, and adverse outcomes) of non-clotting factor therapies for preventing bleeding and bleeding-related complications in people with congenital hemophilia A or B compared with prophylaxis with clotting factor therapies, bypassing agents, placebo, or no prophylaxis.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, electronic databases, conference proceedings, and reference lists of relevant articles and reviews. The date of the last search was 16 August 2023.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating people with congenital hemophilia A or B with and without inhibitors, who were treated with non-clotting factor therapies to prevent bleeds.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed studies for eligibility, assessed risk of bias, and extracted data for the primary outcomes (bleeding rates, health-related quality of life (HRQoL), adverse events) and secondary outcomes (joint health, pain scores, and economic outcomes). We assessed the mean difference (MD), risk ratio (RR), 95% confidence interval (CI) of effect estimates, and evaluated the certainty of the evidence using GRADE.

MAIN RESULTS

Six RCTs (including 397 males aged 12 to 75 years) were eligible for inclusion. Prophylaxis versus on-demand therapy in people with inhibitors Four trials (189 participants) compared emicizumab, fitusiran, and concizumab with on-demand therapy in people with inhibitors. Prophylaxis using emicizumab likely reduced annualized bleeding rates (ABR) for all bleeds (MD -22.80, 95% CI -37.39 to -8.21), treated bleeds (MD -20.40, 95% CI -35.19 to -5.61), and annualized spontaneous bleeds (MD -15.50, 95% CI -24.06 to -6.94), but did not significantly reduce annualized joint and target joint bleeding rates (AjBR and AtjBR) (1 trial; 53 participants; moderate-certainty evidence). Fitusiran also likely reduced ABR for all bleeds (MD -28.80, 95% CI -40.07 to -17.53), treated bleeds (MD -16.80, 95% CI -25.80 to -7.80), joint bleeds (MD -12.50, 95% CI -19.91 to -5.09), and spontaneous bleeds (MD -14.80, 95% CI -24.90 to -4.71; 1 trial; 57 participants; moderate-certainty evidence). No evidence was available on the effect of bleed prophylaxis using fitusiran versus on-demand therapy on AtjBR. Concizumab may reduce ABR for all bleeds (MD -12.31, 95% CI -19.17 to -5.45), treated bleeds (MD -10.10, 95% CI -17.74 to -2.46), joint bleeds (MD -9.55, 95% CI -13.55 to -5.55), and spontaneous bleeds (MD -11.96, 95% CI -19.89 to -4.03; 2 trials; 78 participants; very low-certainty evidence), but not target joint bleeds (MD -1.00, 95% CI -3.26 to 1.26). Emicizumab prophylaxis resulted in an 11.31-fold increase, fitusiran in a 12.5-fold increase, and concizumab in a 1.59-fold increase in the proportion of participants with no bleeds. HRQoL measured using the Haemophilia Quality of Life Questionnaire for Adults (Haem-A-QoL) physical and total health scores was improved with emicizumab, fitusiran, and concizumab prophylaxis (low-certainty evidence). Non-serious adverse events were higher with non-clotting factor therapies versus on-demand therapy, with injection site reactions being the most frequently reported adverse events. Transient antidrug antibodies were reported for fitusiran and concizumab. Prophylaxis versus on-demand therapy in people without inhibitors Two trials (208 participants) compared emicizumab and fitusiran with on-demand therapy in people without inhibitors. One trial assessed two doses of emicizumab (1.5 mg/kg weekly and 3.0 mg/kg bi-weekly). Fitusiran 80 mg monthly, emicizumab 1.5 mg/kg/week, and emicizumab 3.0 mg/kg bi-weekly all likely resulted in a large reduction in ABR for all bleeds, all treated bleeds, and joint bleeds. AtjBR was not reduced with either of the emicizumab dosing regimens. The effect of fitusiran prophylaxis on target joint bleeds was not assessed. Spontaneous bleeds were likely reduced with fitusiran (MD -20.21, 95% CI -32.12 to -8.30) and emicizumab 3.0 mg/kg bi-weekly (MD -15.30, 95% CI -30.46 to -0.14), but not with emicizumab 1.5 mg/kg/week (MD -14.60, 95% CI -29.78 to 0.58). The percentage of participants with zero bleeds was higher following emicizumab 1.5 mg/kg/week (50% versus 0%), emicizumab 3.0 mg/kg bi-weekly (40% versus 0%), and fitusiran prophylaxis (40% versus 5%) compared with on-demand therapy. Emicizumab 1.5 mg/kg/week did not improve Haem-A-QoL physical and total health scores, EQ-5D-5L VAS, or utility index scores (low-certainty evidence) when compared with on-demand therapy at 25 weeks. Emicizumab 3.0 mg/kg bi-weekly may improve HRQoL measured by the Haem-A-QoL physical health score (MD -15.97, 95% CI -29.14 to -2.80) and EQ-5D-5L VAS (MD 9.15, 95% CI 2.05 to 16.25; 1 trial; 43 participants; low-certainty evidence). Fitusiran may result in improved HRQoL shown as a reduction in Haem-A-QoL total score (MD -7.06, 95% CI -11.50 to -2.62) and physical health score (MD -19.75, 95% CI -25.76 to -11.94; 1 trial; 103 participants; low-certainty evidence). The risk of serious adverse events in participants without inhibitors also likely did not differ following prophylaxis with either emicizumab or fitusiran versus on-demand therapy (moderate-certainty evidence). Transient antidrug antibodies were reported in 4% (3/80) participants to fitusiran, with no observed effect on antithrombin lowering. A comparison of the different dosing regimens of emicizumab identified no differences in bleeding, safety, or patient-reported outcomes. No case of treatment-related cancer or mortality was reported in any study group. None of the included studies assessed our secondary outcomes of joint health, clinical joint function, and economic outcomes. None of the included studies evaluated marstacimab.

AUTHORS' CONCLUSIONS

Evidence from RCTs shows that prophylaxis using non-clotting factor therapies compared with on-demand treatment may reduce bleeding events, increase the percentage of individuals with zero bleeds, increase the incidence of non-serious adverse events, and improve HRQoL. Comparative assessments with other prophylaxis regimens, assessment of long-term joint outcomes, and assessment of economic outcomes will improve evidence-based decision-making for the use of these therapies in bleed prevention.

[Efficacy and safety of prophylaxis with emicizumab in hemophilia A: A study of 13 patients]

INTRODUCTION

Emicizumab is the first non-replacement therapy for prophylaxis in severe hemophilia A.

AIMS

The principal aim of this study is to describe the results of our patients in prophylaxis with emicizumab, according to the usual clinical practice.

MATERIAL AND METHODS

Follow-up of 13 patients from the start of prophylaxis, recording of bleeding, surgeries, adverse reactions and the need or not for factor therapy. Plasma levels were measured at follow-up visits, the technique was coagulative in one stage, modified by 1:20 dilution.

RESULTS

Median plasma levels were 52.2mg [30.7-71.9]. Prophylaxis was safe and effective; only one spontaneous haemorrhage was recorded over time and no treatment was required. There were no thromboembolic events or serious hypersensitivity, anaphylaxis or anaphylactoid reactions. The incidence of injection site reactions was 8%. Perioperative management in minor interventions was carried out without adjuvant factorial therapy, in 2 major surgeries a dose of plasmatic FVIII concentrate was required in the patient with hemophilia A without inhibitor and FVII in the patient with inhibitor, and it was sufficient to stop the bleeding.

CONCLUSION

This study demonstrated emicizumab pharmacokinetics and its half life ensure optimal levels with prophylaxis treatment at doses established in the technical data sheet.

Emicizumab-mediated hemostatic function assessed by thrombin generation assay in an in vitro model of factor VIII-depleted thrombophilia plasma

Patients with hemophilia A (PwHA) may have concurrent deficiency of representative anticoagulant proteins, protein (P)C, PS, and antithrombin (AT), which reduces bleeding frequency. However, emicizumab-driven hemostasis in PwHA with such thrombophilic potential remains unclarified. This study investigated the influence of natural anticoagulants on emicizumab-driven coagulation in HA model plasma. Various concentrations of PS and AT were added to PS-deficient plasma and AT-deficient plasma in the presence of anti-FVIII antibody (FVIIIAb; 10BU/mL). PC-deficient plasma was mixed with normal plasma at various concentrations in the presence of FVIIIAb. Emicizumab (50 µg/mL) was added to these thrombophilic HA model plasmas, prior to tissue factor/ellagic acid-triggered thrombin generation assays. Co-presence of emicizumab increased peak thrombin values (PeakTh) dependent on PS, AT, and PC concentrations. Maximum coagulation potentials in the PS-reduced HA model plasmas remained normal in the presence of emicizumab. PeakTh were close to normal in the presence of 50%AT irrespective of emicizumab, but were higher than normal in the presence of 25%AT. Addition of recombinant FVIIa (corresponding to an administered dose of 90 μg/kg) enhanced coagulation potential to normal levels. Our findings provide novel information on hemostatic regulation in emicizumab-treated PwHA with a possible thrombophilic disposition.

Effectiveness of emicizumab in preventing bleeding events in severe and moderate hemophilia A: A single-center experience in Bangladesh

Emicizumab is a monoclonal antibody that bridges activated factor IX (FIX) and factor X (FX) to replace the function of missing activated factor VIII (FVIII) in hemophilia A patients irrespective of FVIII inhibitor status. This study assessed the effectiveness of emicizumab in preventing bleeding episodes in patients with hemophilia A. This observational study included patients with moderate to severe hemophilia A who were undergoing episodic FVIII replacement therapy. The primary endpoint was the difference in annualized bleeding rates (ABR) and the secondary endpoint was the difference in Hemophilia Joint Health Score (HJHS) before and after emicizumab prophylaxis. A total of 30 male hemophilia patients were included, the mean age was 16.7 (SD: ±8.1) years, and most of them had moderate hemophilia A [63.3%]. Before prophylaxis, the median ABR was 48 (interquartile range [IQR]: 35-60), and 93.3% of patients had ABR greater than eight, whereas after prophylaxis the median ABR decreased significantly (median [IQR]: 0 [0.0-0.4], p < 0.001), and 56.7% had zero bleeds. ABR was not significantly different in patient with and without FVIII inhibitors. The HJHS scores significantly improved after prophylaxis (10 vs. 2.5, p < 0.001). The bleeding events were reduced significantly (23 vs. 0.0, p < 0.001), and zero new target joints were reported after prophylaxis. Most of the patients [93.3%] did not face any serious adverse events after prophylaxis. Emicizumab prophylaxis was associated with a significantly lower rate of bleeding events among participants with hemophilia A, regardless of inhibitor status.

A bispecific antibody NXT007 exerts a hemostatic activity in hemophilia A monkeys enough to keep a nonhemophilic state

BACKGROUND

Emicizumab, a factor (F) VIIIa-function mimetic bispecific antibody (BsAb) to FIXa and FX, has become an indispensable treatment option for people with hemophilia A (PwHA). However, a small proportion of PwHA still experience bleeds even under emicizumab prophylaxis, as observed in the long-term outcomes of clinical studies. A more potent BsAb may be desirable for such patients.

OBJECTIVES

To identify a potent BsAb to FIXa and FX, NXT007, surpassing emicizumab by in vitro and in vivo evaluation.

METHODS

New pairs of light chains for emicizumab's heavy chains were screened from phage libraries, and subsequent antibody optimization was performed. For in vitro evaluation, thrombin generation assays were performed with hemophilia A plasma. In vivo hemostatic activity was evaluated in a nonhuman primate model of acquired hemophilia A.

RESULTS

NXT007 exhibited an in vitro thrombin generation activity comparable to the international standard activity of FVIII (100 IU/dL), much higher than emicizumab, when triggered by tissue factor. NXT007 also demonstrated a potent in vivo hemostatic activity at approximately 30-fold lower plasma concentrations than emicizumab's historical data. In terms of dose shift between NXT007 and emicizumab, the in vitro and in vivo results were concordant. Regarding pharmacokinetics, NXT007 showed lower in vivo clearance than those shown by typical monoclonal antibodies, suggesting that the Fc engineering to enhance FcRn binding worked well.

CONCLUSION

NXT007, a potent BsAb, was successfully created. Nonclinical results suggest that NXT007 would have a potential to keep a nonhemophilic range of coagulation potential in PwHA or to realize more convenient dosing regimens than emicizumab.

Long-term outcomes with emicizumab in hemophilia A without inhibitors: results from the HAVEN 3 and 4 studies

Background

Emicizumab, a bispecific monoclonal antibody, bridges activated factor (F) IX and FX, mimicking the function of missing or deficient activated FVIII in people with hemophilia A (HA).

Objectives

To evaluate the long-term efficacy and safety of emicizumab prophylaxis in people with HA without FVIII inhibitors in the HAVEN 3 and 4 studies.

Methods

HAVEN 3 and 4 were phase 3 open-label studies. Participants received emicizumab maintenance doses of 1.5 mg/kg every week or 3 mg/kg every 2 weeks (HAVEN 3), or 6 mg/kg every 4 weeks (HAVEN 4). Long-term efficacy and safety were assessed.

Results

A total of 151 and 40 individuals without FVIII inhibitors received emicizumab in HAVEN 3 and 4, respectively. At the last patient, last visit dates (May 12, 2022 [HAVEN 3] and June 29, 2022 [HAVEN 4]), the median (range) duration of emicizumab exposure across the 2 studies was 248.1 (6.1-287.1) weeks. The mean (95% CI) annualized bleed rate for treated bleeds was 2.0 (0.23-7.15) for weeks 1 to 24, decreasing to 0.9 (0.01-5.28) by weeks 217 to 240. Overall, 188 (98.4%) participants experienced ≥1 adverse event (AE), with 185 treatment-related AEs in 71 (37.2%) participants. Forty-four (23.0%) participants reported a serious AE. Two thromboembolic events were reported, which were deemed unrelated to emicizumab by the investigator. No thrombotic microangiopathies were reported.

Conclusion

With nearly 5 years of emicizumab exposure across the HAVEN 3 and 4 studies in people with HA without inhibitors, these data indicate continued bleed control with no new safety signals observed during long-term follow-up.

Determinants of bleeding before and during immune tolerance in 222 boys with severe hemophilia A and inhibitors >5 BU

ABSTRACT

Prevention of bleeding and its consequences is the main goal of hemophilia treatment and determines treatment choices for patients who develop inhibitors. To assess bleeding before and during immune tolerance induction (ITI) and its association with ITI regimen and inhibitor titer, we selected and analyzed data on patients receiving high-titer inhibitors from the international prospective PedNet cohort study. In total, 222 patients with severe hemophilia A and inhibitor titers of >5 Bethesda units (BU) were followed from the first positive to the first negative inhibitor result (median overall follow-up, 1.7 years). Mean annual (joint) bleeding rates (AJBR) and 95% confidence intervals (CIs) were compared according to treatment and inhibitor titer using multivariable negative binomial regression. Before ITI, 115 patients showed an ABR of 6.1 (5.0-7.4) and an AJBR 2.6 (2.1-3.2). Bleeding was independent of inhibitor titer. During ITI, 202 patients had an ABR of 4.4 (3.9-5.1) and an AJBR of 1.7 (1.5-2.0). AJBR during ITI increased with inhibitor titer (hazard ratio [HR] for ≥200 BU vs 5 to 39 BU [4.9; CI, 3.2-7.4]) and decreased with daily ITI infusions (HR, 0.4; CI, 0.3-0.6) or activated prothrombin complex concentrate prophylaxis (HR, 0.4; CI, 0.2-0.8), whereas ITI dose and recombinant activated factor VII prophylaxis did not independently affect bleeding. These data provide evidence for a protective effect of repeated FVIII infusions (ITI) on bleeding in patients who have developed inhibitors; these data should be used to plan ITI and/or serve as a comparator for prophylaxis with nonreplacement therapy.

Pharmacokinetics and coagulation biomarkers in children and adults with hemophilia A receiving emicizumab prophylaxis every 1, 2, or 4 weeks

Background

Emicizumab is a bispecific antibody that bridges activated factor (F)IX and FX, mimicking the function of missing activated FVIII and thus improving hemostasis in people with hemophilia A. The efficacy and safety of emicizumab were demonstrated in 4 phase III clinical trials (HAVEN 1-4).

Objectives

Here, we describe pharmacokinetics (PKs), pharmacodynamics (PDs), and exploratory safety biomarkers in HAVEN 1 to 4.

Methods

Participants received emicizumab at a loading dose of 3 mg/kg weekly for 4 weeks, followed by maintenance doses of 1.5 mg/kg weekly, 3 mg/kg every 2 weeks, or 6 mg/kg every 4 weeks. PKs, PDs, and safety biomarkers were assessed in samples collected at regular intervals during the trials.

Results

Emicizumab plasma trough concentrations increased during the loading dose period, reaching a mean of 52.9 μg/mL (SD, 13.6 μg/mL) at week 5, and were sustained at 42.1 to 52.3 μg/mL thereafter with maintenance dosing. Activated partial thromboplastin time shortened following the first emicizumab dose. Mean FVIII-like activity and thrombin generation peak height increased to 25.2 IU/dL (SD, 6.9 IU/dL) and 115.2 nM (SD, 42.5 nM) at week 5, with levels sustained at 17 to 23 IU/dL and >116 nM thereafter, respectively. Emicizumab did not notably affect FIX or FX plasma antigen levels, prothrombin time, or concentrations of exploratory safety markers of coagulation activation (D-dimer, prothrombin fragment 1 + 2, and fibrinogen).

Conclusion

In HAVEN 1 to 4, emicizumab demonstrated sustained PKs and PDs and improved coagulation parameters without affecting safety biomarkers.

Global Hemostatic Methods to Tailor Treatment With Bypassing Agents in Hemophilia A With Inhibitors- A Single-Center, Pilot Study

For patients with hemophilia A and high-titer inhibitors treated with bypassing agents there are no reliable methods to assess treatment effect. We investigated the utility of global hemostatic methods in assessing treatment with bypassing agents (rFVIIa or activated prothrombin complex [aPCC]). All patients with hemophilia A and inhibitors followed at the Coagulation Unit or the Pediatric Coagulation Unit at Karolinska University Hospital aged 6 years and above were eligible for this noninterventional study. Baseline plasma samples were spiked with bypassing agents in increasing concentrations (aPCC 50 U/kg, 100 U/kg, 150 U/kg, and rFVIIa 90 μg/kg and 270 μg/kg) in vitro. For patients treated with factor concentrates or bypassing agents follow-up samples were collected (in vivo tests). The samples were analyzed using overall hemostatic potential (OHP), and calibrated automated thrombogram, Calibrated Automated Thrombogram (CAT). Nine patients with hemophilia A with inhibitors were included. Spiking with rFVIIa normalized the coagulation potential in 6/8 samples, in 3 only with high dose. Only one sample did not improve adequately after spiking with aPCC. The improvement in hemostasis was reliably shown by both CAT and OHP. The baseline potential was, however, more often measurable by OHP compared to CAT. Factor concentrate had been administered to 5 patients normalizing the hemostatic potential in vivo in 2 (without spiking). The hemostatic improvement induced by spiking with rFVIIa or aPCC is shown by OHP and CAT, but the results have to be evaluated in larger cohorts.

Hybrid human-porcine factor VIII proteins partially escape the inhibitory effects of anti-factor VIII inhibitor alloantibodies having A2 or C2 domain specificity

INTRODUCTION

Porcine factor (pF)VIII has low cross-reactivity with anti-human (h)FVIII inhibitor alloantibodies. Clinical trials of pFVIII in congenital haemophilia A patients with inhibitor (PwHA-I) are in progress. Most polyclonal anti-hFVIII inhibitors recognize its A2 and/or C2 domain(s), and recombinant human-porcine hybrid (hp)FVIII proteins may escape neutralization by these inhibitors.

AIM

To evaluate the ability of hpFVIII to limit the anti-FVIII activity of inhibitor alloantibodies.

METHODS

Three hybrid proteins were created by substituting the hFVIII A2, C2 domain or both with the corresponding domains of pFVIII [termed hp(A2), hp(C2) and hp(A2/C2), respectively]. The reactivity of these hybrids was assessed by one-stage clotting assays (OSA), thrombin generation assays (TGA) and rotational thromboelastometry (ROTEM) by adding them to FVIII-deficient samples.

RESULTS

OSA demonstrated that the hybrid proteins avoided neutralization by anti-FVIII A2 or C2 monoclonal antibodies (mAb) and polyclonal inhibitor-antibodies (polyAb) from PwHA-I. In TGA, thrombin generation with hp(A2) and hp(A2/C2) was not attenuated in the presence of patient IgG recognizing anti-A2 domain. In contrast, that with hFVIII and hp(C2) was suppressed by this IgG to levels equivalent to those of FVIII-deficient plasma. With anti-A2/C2 polyAb, the activity of hp(A2/C2) was unaffected. ROTEM demonstrated that the addition of hp(A2) or hp(A2/C2) to anti-A2 polyAb shortened clot times/clot formation times, whilst hFVIII or hp(C2) were ineffective. Similarly with anti-A2/C2 polyAb, hp(A2/C2) restored coagulation potential to a greater extent than hp(A2) and hp(C2).

CONCLUSION

Hybrid FVIII proteins containing porcine FVIII A2 and/or C2 domain(s) could support effective therapy in PwHA-I by avoiding neutralization.

Thrombin generation on vascular cells in the presence of factor VIII and/or emicizumab

BACKGROUND

The effect of factor VIII (FVIII) or emicizumab on thrombin generation is usually assessed in assays using synthetic phospholipids. Here, we assessed thrombin generation at the surface of human arterial cells (aortic endothelial cells [hAECs] and aortic vascular smooth muscle cells [hVSMCs]).

OBJECTIVES

To explore the capacity of hAECs (resting or stimulated) and hVSMCs to support thrombin generation by FVIII or emicizumab.

METHODS

Primary hVSMCs and hAECs were analyzed for tissue factor (TF)-activity and antigen, phosphatidylserine (PS)-exposure, tissue factor pathway inhibitor (TFPI)-content and thrombomodulin expression. Cells were incubated with FVIII-deficient plasma spiked with FVIII, emicizumab, activated prothrombin complex concentrate (APCC) or combinations thereof.

RESULTS

TF activity and PS-exposure were present on both hVSMCs and hAECs. In contrast, thrombomodulin and TFPI were expressed on hAECs, while virtually lacking on hVSMCs, confirming the procoagulant nature of hVSMCs. Tumor necrosis factor α-mediated stimulation of hAECs increased not only TF antigen, TF activity, and PS-exposure but also TFPI and thrombomodulin expression. As expected, FVIII and emicizumab promoted thrombin generation on nonstimulated hAECs and hVSMCs, with more thrombin being generated on hVSMCs. Unexpectedly, FVIII and emicizumab increased thrombin generation to a lesser extent on stimulated hAECs compared with nonstimulated hAECs. Finally, adding emicizumab to FVIII did not further increase thrombin generation, whereas the addition of emicizumab to APCC resulted in exaggerated thrombin generation.

CONCLUSION

Tumor necrosis factor stimulation of hAECs increases both pro- and anticoagulant activity. Unexpectedly, the increased anticoagulant activity is sufficient to limit both FVIII- and emicizumab-induced thrombin generation. This protective effect disappears when emicizumab is combined with APCC.

Association of physical activity with bleeding events and safety in patients with haemophilia A starting emicizumab prophylaxis: an interim analysis of the TSUBASA study

INTRODUCTION

Little information exists on the relationship between bleeding outcomes and physical activity in patients with haemophilia A (PwHA).

AIM

This interim analysis of the TSUBASA study (UMIN-CTR ID: UMIN000037448) evaluated the association of physical activity with bleeding and safety in PwHA starting emicizumab.

METHODS

PwHA without factor VIII inhibitors were recruited. Physical activity and bleed data were obtained using an electronic patient-reported outcome application and wearable activity tracker. Adverse events (AEs) were documented.

RESULTS

At data cut-off (31-May-2021), 107 PwHA were enrolled, with a median (range) age of 35 (0-73) years. Physical activity data were obtained for 74 participants. Of these, 47 (63.5%) recorded a total of 396 exercise events. The most common exercise events were walking (32.4%), cycling (14.9%), and football (5.4%). Two (0.5%) exercise events in the same individual were associated with bleeding (running, weight training). The safety analysis population consisted of 106 participants treated with emicizumab (median observation period: 241.5 days). Twenty-one (19.8%) participants experienced a total of 39 AEs. Five (4.7%) experienced a serious AE, none of which was emicizumab-related, and three (2.8%) experienced an adverse drug reaction.

CONCLUSIONS

PwHA receiving emicizumab in the TSUBASA study experienced minimal bleeding associated with physical activity.

TRIAL REGISTRATION

Trial registration: UMIN-CTR ID: UMIN000037448.

Emicizumab Prophylaxis in Patients with Severe Hemophilia A: Insights from A Resource Limited Country

METHODS

In this prospective study, severe HA patients were recruited from January 2022 to June 2023. Inhibitor positive and inhibitor negative patients with annual bleeding rate (ABR) 8 or greater and past histories of bleeding like intra-cranial, intra-abdominal, and pseudo-tumors were included. Emicizumab loading dose was 3 mg/kg in the first 4 weeks, and the maintenance dose was started at week 5 at 6 mg/kg/month. Patients' detailed bleeding history and demographics were recorded. The five-level EuroQol five-dimensional questionnaire (EQ-5D-5L) was used to evaluate patients' HRQoL. Furthermore, Hemophilia Joint Health Score (HJHS) and Functional Independence score in Hemophilia (FISH) were applied for the assessment of joints at different time points. Results were analyzed by SPSS version 21.

RESULTS

A total of 36 HA male patients with the mean age of 19.7 ± 14.42 years were recruited in the study; among them, 19 patients were inhibitor positive, while 17 were negative. Patients clinically presented with bleeding symptoms which included: hemarthrosis 95%, GI bleeding 13.8%, and bruises and gums bleeding 13.8%. Significant reduction was observed in the bleeding episodes after the therapeutic intervention, and joints assessment and Euro-Quality-of-life Visual Analog Scale showed a significant improvement in health after treatment. Similarly, there was a remarkable reduction in bleeding episodes and improved quality of life among HA patients. The ABR decreased from 53.6% episodes per year prior to treatment to 2.4% during Emicizumab therapy. Prior to initiating Emicizumab therapy, participants exhibited an average FISH score of 16 and HJHS score of 10, indicating moderate limitations due to joint-related issues. After treatment, the mean FISH score improved to 9 and HJHS score to 4 reflecting a substantial enhancement in participants' ability to perform daily activities (P < 0.057).

CONCLUSION

Our results showed that HA patients on prophylactic treatment with Emicizumab were less restricted and had improved quality of life due to marked decrease in bleeding episodes which resulted in improved health and social lives. In addition, it was well tolerated, and no participant discontinued treatment because of adverse events.

NXT007-mediated hemostatic potential is suppressed by activated protein C-catalyzed inactivation of activated factor V

Background

Activated protein C (APC) inactivates activated factor (F) V (FVa) and FVIIIa. NXT007, an emicizumab-based engineered therapeutic bispecific antibody, enhances the coagulation potential of FVIII-deficient plasma (FVIIIdef-plasma) to near normal levels. However, little is known about the effect of APC-induced inactivation in NXT007-mediated hemostatic function.

Objectives

To investigate the contribution of APC-mediated reactions to NXT007-driven hemostasis.

Methods

In pooled normal plasma (PNP) or FVIIIdef-plasma spiked with NXT007 (10 μg/mL), effects of APC (0-16 nM) were measured using a thrombin generation assay (TGA). The direct effects of APC on cofactor activity of NXT007 or FVIIIa in a FXa generation assay were also measured. The FVdef-plasma and FV Leiden plasma (FVLeiden plasma) were preincubated with 2 anti-FVIII monoclonal antibodies (termed FVIII-depleted), and the APC effect in the presence of NXT007 in FVIII-depleted FVdef-plasma with the addition of exogenous FV (7.5-30 nM) or FVIII-depleted FVLeiden plasma was investigated.

Results

The APC dose-dependent suppression effect in TGA of FVIIIdef-plasma spiked with NXT007 was similar to that of PNP. FXa generation with NXT007 was not impaired by the addition of APC, suggesting that the APC-induced reaction in TGA with NXT007 was attributed to the direct inactivation of FVa. The addition of APC to FVIII-depleted FVdef-plasma, along with NXT007 and various FV concentrations, showed a similar attenuation to PNP. The NXT007-driven thrombin generation in FVIII-depleted FVLeiden plasma was suppressed by APC, similar to the reaction in native FVLeiden plasma.

Conclusion

NXT007 did not impair APC-mediated downregulation of FVa in FVIIIdef-plasmas, regardless of the presence of FV mutation with APC resistance.

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..

Longitudinal dynamic changes in factor VIII inhibitor titers in patients with hemophilia A and inhibitors receiving emicizumab prophylaxis

Emicizumab prophylaxis dramatically reduces bleeding events in patients with hemophilia A (PwHA) with or without factor VIII (FVIII) inhibitors. However, long-term dynamic changes in FVIII inhibitor titers during emicizumab prophylaxis remain to be investigated. We conducted a retrospective follow-up study of FVIII inhibitor titers after initiation of emicizumab prophylaxis in 25 PwHA carrying current or historical FVIII inhibitors. Nineteen PwHA had FVIII inhibitors at initiation of emicizumab prophylaxis (age: median 22 [range 4-60] years and inhibitor titer: 30 [1.0-1450] BU/mL). In 17 of the 19 patients, the inhibitor titers markedly decreased to a median of 1.2 (< 0.6-58) BU/mL at a median follow-up of 71 (38-111) months. In two patients, titers were slightly elevated after initiation of emicizumab but decreased in the long term. The remaining six patients had negative inhibitor status (< 0.6 BU/mL) when switched to emicizumab from FVIII prophylaxis. Five patients maintained negative titers. One patient had inhibitor recurrence, with a peak titer of 1.6 BU/mL that decreased to 0.9 BU/mL. In most cases, FVIII inhibitor titers can be expected to decrease spontaneously during emicizumab prophylaxis, but regular follow-up is necessary to manage breakthrough bleeds.

Emicizumab prophylaxis for people with hemophilia A: Waste estimation and the Brazilian perspective

Costs of hemophilia A treatment are increasing. Waste of clotting products should be avoided. To estimate the first-year waste of emicizumab prophylaxis for people with hemophilia A and inhibitors (PwHAi) who failed immune tolerance induction (ITI), in Brazil. We evaluated the manufacturer and the Brazilian Ministry of Health (MoH) protocol-recommended regimens in a budget impact model. The loading dose consisted of 3.0 mg/kg/Q1W for 4 weeks, for both recommendations. The manufacturer maintenance regimens comprised 1.5 mg/kg/Q1W, 3.0 mg/kg/Q2W, and 6.0 mg/kg/Q4W. The MoH protocol maintenance regimen encompassed a hybrid Q1W/Q2W administration, depending on the body weight. The Q4W regimen was not recommended by the MoH protocol. Analyses were performed to estimate waste given its expense based on the World Health Organization body weight range (percentiles [P] 15, 50, and 85). The first-year emicizumab waste was estimated individually and for the disclosed PwHAi who failed ITI (n = 114). The highest emicizumab waste was estimated for the lowest body weights and the Q1W regimen. The Q4W regimen resulted in the lowest emicizumab waste, followed by the MoH protocol regimen. The total reconstituted costs estimated for the PwHAi who failed ITI according to the hybrid MoH protocol ranged from US$32,858,777 (P15) to US$47,186,858 (P85), with emicizumab waste ranging from 7.9 % (US$2,594,515) to 3.7 % (US$1,738,750), respectively. Lost resources due to current protocols for emicizumab prophylaxis for PwHAi who failed ITI in Brazil are considerable. Waste was more pronounced due to lower body weight and shorter administration intervals.

Real-world data on the use of emicizumab in patients with haemophilia A with and without inhibitors in Singapore

Introduction

Emicizumab is a bispecific monoclonal antibody that mimics the function of factor VIII by binding to factor IXa and factor X to achieve haemostasis in haemophilia A. The long half-life and subcutaneous mode of administration makes emicizumab a compelling treatment option for bleeding prophylaxis. There is still limited real-world data on its use and management considerations, especially during surgical procedures. The objective of the study is to describe the real-world experience of emicizumab in a cohort of adult and paediatric haemophilia A patients in Singapore, including its use in the periprocedural setting.

Method

This was an observational study conducted at the 2 main haemophilia treatment centres in Singapore. All haemophilia A patients who commenced treatment with emicizumab before 1 July 2022 were recruited.

Results

A total of 18 patients with haemophilia A were included in this study. Ten (55.6%) patients had active inhibitors. The median annual bleeding rate for all patients before emicizumab use was 4.5 events (interquartile range [IQR] 2.8-8.3) compared with 0 events (IQR 0-0) after emicizumab was commenced (P=0). There were no adverse events of venous or arterial thrombosis, thrombotic microangiopathy, or death. A total of 6 procedures in 5 patients were performed during the study period with no major bleeding complications.

Conclusion

Emicizumab effectively protects against bleeding in haemophilia A patients with and without inhibitors, including in children less than 12 years old. More studies are required to address clinical nuances, such as periprocedural management and the role of immune tolerance in patients with inhibitors on emicizumab.

Emergent data influences the risk/benefit assessment of hemophilia gene therapy using recombinant adeno-associated virus

After decades of investigation, gene therapy has received regulatory approval to treat hemophilia. However, since gene therapy investigations were initially conceived, other avenues of treatment have revolutionized the care of hemophilia. Emergent data is showing that gene therapy may not be as beneficial as hoped and more toxic than planned. At a minimum, a reassessment of risk/benefit estimate of gene therapy for hemophilia is needed.

Emicizumab use in females with moderate or mild hemophilia A without factor VIII inhibitors who warrant prophylaxis

Background

Hemophilia A (HA) is predominantly associated with males due to X-linked inheritance. Males and females with HA have shared unmet medical needs, highlighting the necessity for comprehensive care irrespective of sex.

Objectives

This analysis investigated the efficacy and safety of emicizumab prophylaxis in 3 females with HA.

Methods

HAVEN 6 (NCT04158648) is a phase III study of emicizumab in people with non-severe HA without factor (F)VIII inhibitors warranting prophylaxis per investigator assessment, and the study methodology has been reported previously. Female-specific endpoints included menstruation-related quality of life and menstruation heaviness.

Results

HAVEN 6 enrolled 3 females aged ≥18 years and within reproductive age (n = 2 mild HA; n = 1 moderate HA; n = 2 receiving prior FVIII prophylaxis; n = 1 receiving prior episodic FVIII). Participants presented with diverse bleeding phenotypes at baseline: 2 had no bleeds in the 24 weeks prior to enrollment, while 1 had an annualized bleed rate for all bleeds of 208.6. On-study annualized bleed rates for all bleeds were 0, 2.8, and 11.6, respectively. The 2 evaluable participants indicated improved menstruation-related quality of life vs baseline. Two participants experienced 3 grade 1/2 treatment-related adverse events; no new safety signals were identified. All 3 participants preferred emicizumab over their previous treatment and reported a better score for treatment burden and preoccupation domains of the Comprehensive Assessment Tool of Challenges in Hemophilia questionnaire.

Conclusion

Overall, results were consistent with those reported in the male population enrolled in the HAVEN 6 study, suggesting efficacy and a favorable safety profile for emicizumab in females with non-severe HA warranting prophylaxis.

Inhibitor development according to concentrate in severe hemophilia: reporting on 1392 Previously Untreated Patients from Europe and Canada

Background

Clotting factor concentrates have been the mainstay of severe hemophilia treatment over the last 50 years. Differences in risk of neutralizing antibody (inhibitor) formation according to concentrate used remain clinically relevant.

Objectives

To assess inhibitor development according to type of clotting factor concentrate in previously untreated patients (PUPs) with severe hemophilia A and B.

Methods

The European Haemophilia Safety Surveillance (EUHASS) and Canadian Bleeding Disorders Registry (CBDR) have been monitoring adverse events overall and according to concentrate for 11 and 8 years, respectively. Inhibitors were reported quarterly, and PUPs completed 50 exposure days without inhibitor development annually. Cumulative inhibitor incidences and 95% confidence intervals (CIs) were compared without adjustment for other risk factors.

Results

Fifty-six European and 23 Canadian centers reported inhibitor development in 312 of 1219 (26%; CI, 23%-28%) PUPs with severe hemophilia A and 14 of 173 (8%; CI, 5%-13%) PUPs with severe hemophilia B. Inhibitor development was lower on plasma-derived factor (F)VIII (pdFVIII, 20%; CI, 14%-26%) than on standard half-life recombinant FVIII (SHL-rFVIII, 27%; CI, 24%-30% and odds ratio, 0.67; CI, 0.45%-0.98%; P = .04). Extended half-life recombinant FVIII (EHL-rFVIII, 22%; CI, 12%-36%) showed an intermediate inhibitor rate, while inhibitor rates for Advate (26%; CI, 22%-31%) and Kogenate/Helixate (30%; CI, 24%-36%) overlapped. For other SHL-rFVIII concentrates, inhibitor rates varied from 3% to 43%. Inhibitor development was similar for pdFIX (11%; CI, 3%-25%), SHL-rFIX (8%; CI, 3%-15%), and EHL-rFIX (7%; CI, 1%-22%).

Conclusion

While confirming expected rates of inhibitors in PUPs, inhibitor development was lower in pdFVIII than in SHL-rFVIII. Preliminary data suggest variation in inhibitor development among different SHL-rFVIII and EHL-rFVIII concentrates.