Emicizumab for hemophilia A with factor VIII inhibitors

Induction of factor VIII tolerance by hemophilia gene transfer to eradicate factor VIII inhibitors

ABSTRACT

Patients with hemophilia A can develop antifactor antibodies to factor VIII. The incidence is ∼30%, and such patients suffer worse morbidity and mortality. The only proven method to eradicate these inhibitors is via immune tolerance induction therapy, which consists of infusing factor VIII concentrates at regular intervals. This approach is effective ∼65% of the time, leaving at least a third of patients who develop inhibitors with this lifelong problem. Although emicizumab has greatly improved the quality of life of inhibitor patients, eradicating the inhibitor remains an important treatment goal. Animal models have shown the potential for gene therapy to induce tolerance. A recent abstract describing a study in humans demonstrated the potential for successful tolerance induction. This article will describe the rationale for using gene therapy to induce tolerance and provide this author's viewpoint on the importance and possible historic significance of attempting to eradicate inhibitors with this approach.

A retrospective single-center study on the effectiveness and tolerability of emicizumab in patients with hemophilia a with and without inhibitors

BACKGROUND

Hemophilia A (HA) is an X-linked disorder due to deficient/defective coagulation factor VIII (FVIII), which causes excessive bleeding either traumatic or spontaneous. Frequent FVIII replacement is complicated by the development of inhibitors. The bispecific monoclonal antibody emicizumab, offers a novel approach by bridging activated factors IXa and X for effective hemostasis.

RESEARCH DESIGN AND METHODS

This retrospective study analyzed emicizumab treatment outcomes in 73 patients with severe HA at a tertiary care center in Jammu and Kashmir, India. Data included demographic profiles, bleeding rates, joint health scores, and adverse events (AEs).

RESULTS

Emicizumab demonstrated significant efficacy and safety in the study with median patient age of 14 years, with 17/73 patients having FVIII inhibitors. It resulted in a 100% reduction in annualized bleeding rate (ABR) for patients with inhibitors (from 20.7 to 0.0) and a 99.5% reduction for those without inhibitors (from 7.7 to 0.04). All inhibitor-negative patients showed ABR improvements and significant reduction in joint bleeds and resolution of all target joints. Tolerability was favorable with only one patient reporting a non-significant AE.

CONCLUSIONS

Emicizumab prophylaxis effectively reduces ABRs and enhances joint health in severe HA patients, irrespective of inhibitor presence, providing a convenient, well-tolerated alternative to FVIII therapy.

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.

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.

The role of emicizumab in acquired hemophilia A

Acquired hemophilia is a rare bleeding disorder that predominantly affects older people with potential underlying comorbidities, including cardiovascular and thrombotic risk factors. The current standard therapies with hemostatic agents for acute bleeding and immunosuppression often require inpatient management, are not approved for routine bleeding prophylaxis, and contribute to the high mortality in this population. Emicizumab is a factor VIII (FVIII) mimetic approved for bleeding prophylaxis in congenital hemophilia A with and without FVIII inhibitors. Given subcutaneously, it may allow easier outpatient bleeding prophylaxis and reduce intensity of immunosuppression. This article summarizes the currently available data on the efficacy and safety of emicizumab in acquired hemophilia A.

Hemophilia A: Emicizumab monitoring and impact on coagulation testing

Hemophilia A is an X-linked recessive bleeding disorder characterized by absent or ineffective coagulation factor VIII, a condition that could result in a severe and potentially life-threatening bleed. Although the current standard of care involves prophylactic replacement therapy of factor VIII, the development of neutralizing anti-factor VIII alloantibody inhibitors often complicates such therapeutic treatment. Emicizumab (Hemlibra®), a novel recombinant therapeutic agent for patients with hemophilia A, is a humanized asymmetric bispecific IgG4 monoclonal antibody designed to mimic activated factor VIII by bridging factor IXa and factor X thus effecting hemostasis. Importantly, this drug eliminates the need for factor VIII and complications associated with inhibitor generation. Emicizumab has been approved for use in several countries including the United States and Japan for prophylaxis of bleeding episodes in hemophilia A with and without FVIII inhibitors. Therapy is also approved in the European Union for routine prophylaxis of bleeds in hemophilia A with inhibitors or severe hemophilia A without inhibitors. Unfortunately, emicizumab therapy presents unique challenges for routine and specialty coagulation tests currently used to monitor hemophilia A. In this review, hemophilia A is presented, the biochemistry of factor VIII is discussed, and the impact of the therapeutic agent emicizumab is highlighted.

Changing paradigms of hemophilia care across larger specialized treatment centers in the European region

Introduction:

In early 2021, the European Collaborative Haemophilia Network (ECHN) conducted a survey to determine whether the paradigms of care across the European region have changed with the introduction of novel therapies for people with hemophilia.

Methods:

We conducted a survey in 19 ECHN centers from 17 countries in the European region. The aim was to track recent changes in the hemophilia treatment landscape, determine the impact of these changes on hemophilia treatment centers and comprehensive care centers in the region, and to look into the future of care as applied to people with hemophilia. The survey was structured to include three key areas: demographics and organization; current challenges and opportunities; and future directions.

Discussion:

Our survey provides a snapshot of the current approach to hemophilia treatment that highlights a move toward preventive, rather than reactive care, but that also raises a number of key concerns related to costs and accessibility (particularly as related to novel therapies), time limitations for clinical research, and ongoing issues regarding human resources (particularly in terms of new doctors entering the field) and availability of laboratory resources as the use of novel therapies (some with unique modes of action and unusual adverse events, some with specialized monitoring requirements) becomes commonplace.

Conclusion:

While our survey suggests that specialized care will continue to play a central role in the management of hemophilia, the standards and protocols, as well as the centers themselves, will have to continue to evolve if they are to continue to provide the highest level of care. To meet this requirement, there is a clear need for engaging, ongoing education programs for healthcare professionals working in the field of hemophilia that can be adjusted to the changing landscape of hemophilia therapy and monitoring.

AKATSUKI study: a prospective, multicentre, phase IV study evaluating the safety of emicizumab under and immediately after immune tolerance induction therapy in persons with congenital haemophilia A with factor VIII inhibitors

INTRODUCTION

For persons with haemophilia A with factor (F) VIII inhibitors (PwHAwI), immune tolerance induction (ITI) therapy is indicated for inhibitor eradication; however, since PwHAwI on ITI were excluded from the emicizumab clinical development programme, there are limited safety data for emicizumab treatment under/immediately after ITI in PwHAwI. Accordingly, there is a need to collect safety and efficacy data on this concomitant treatment strategy. The AKATSUKI study aims to evaluate the safety of emicizumab under/immediately after ITI in PwHAwI; here we report details of the study protocol.

METHODS AND ANALYSIS

AKATSUKI is an open-label, non-randomised, interventional, multicentre study. Twenty participants with congenital HA with FVIII inhibitors will be enrolled from 17 sites across Japan. Emicizumab will be administered subcutaneously, with an initial loading dose of 3 mg/kg once per week (QW) for the first 4 weeks, followed by a maintenance dose of 1.5 mg/kg QW, 3 mg/kg once every 2 weeks or 6 mg/kg once every 4 weeks. For ITI therapy, 50 IU/kg FVIII will be administered three times per week. For extended half-life FVIII, a dosing frequency of twice per week will be permitted. The primary endpoint is a comprehensive safety evaluation of adverse events (mainly thromboembolic events) and abnormal laboratory values over time. Secondary endpoints are the number of bleeds requiring coagulation factor treatment, the number of participants achieving a partially successful ITI response, FVIII inhibitor titres under/immediately after ITI, quality of life and time to achieve a negative FVIII inhibitor result (<0.6 BU/mL) and partial success in PwHAwI starting ITI after study enrolment.

CONCLUSIONS

AKATSUKI will evaluate the safety of emicizumab administered under/immediately after ITI, providing reference data to inform treatment strategies in PwHAwI.

ETHICS AND DISSEMINATION

The results of this study will be published in a peer-reviewed international journal and presented at national and/or international medical scientific conferences; the major findings of this study will be published on the jRCT registry website (https://jrct.niph.go.jp).

TRIAL REGISTRATION NUMBER

jRCTs041200037.

Design of an international investigator-initiated study on MOdern Treatment of Inhibitor-positiVe pATiEnts with haemophilia A (MOTIVATE)

Background:

Inhibitor development is the most serious treatment-related complication of replacement coagulation factor VIII (FVIII) therapy for patients with haemophilia A. Immune tolerance induction (ITI), which involves intensive and prolonged treatment with plasma-derived or recombinant FVIII, is the only clinically proven strategy for eradication of inhibitors. The bispecific antibody emicizumab is approved for use in patients with and without inhibitors to prevent bleeding but does not eliminate inhibitors. MOTIVATE (www.motivate-study.com) aims to capture different approaches to the treatment and management of patients with haemophilia A and inhibitors, document current ITI approaches from real-world clinical experience, and evaluate the efficacy and safety of ITI, emicizumab prophylaxis and ITI with emicizumab prophylaxis.

Methods:

The investigator-initiated MOTIVATE study [ClinicalTrials.gov identifier: NCT04023019; EudraCT 2019-003427-38] will investigate in real-life clinical practice the management of patients with haemophilia A of any severity who have developed inhibitors to FVIII. All treatment is at the investigator’s discretion. The following treatment approaches will be evaluated: Group 1 – ITI with Nuwiq^®, octanate^® or wilate^® and aPCC/rFVIIa if needed to treat bleeding episodes (BEs) or during surgery or for prophylaxis; Group 2 – ITI with Nuwiq^®, octanate^® or wilate^® and emicizumab prophylaxis and aPCC/rFVIIa if needed to treat BEs or during surgery; Group 3 – routine prophylaxis with emicizumab, aPCC or rFVIIa without ITI and aPCC/rFVIIa if needed to treat BEs or during surgery. Patients will not be randomised to a treatment group and may change groups during the study.

Conclusions:

It is planned to enrol 120 patients who will be followed for up to 5 years. Optional sub-studies will explore factors that may influence ITI results as well as the impact of different treatment approaches on important aspects of patient health, including joint and bone health and the risk of thrombotic events.

Spinal epidural hematoma in a child with hemophilia A with high titer inhibitors and follow-up with prophylactic emicizumab: case report and literature review

Hemorrhage in the central nervous system is the most severe and debilitating manifestation affecting patients with hemophilia A. The spinal epidural space is the most unusual and clinically challenging site of central nervous system hemorrhage in hemophilia A. These patients often show insidious neurological signs and symptoms that delay diagnosis and treatment. We share our experience treating a 4-year-old male patient with severe hemophilia A and high titer inhibitors with a spontaneous spinal epidural hematoma. The patient presented initially with intense headache and neck pain. After blood tests and imaging studies, bypassing agent therapy with recombinant-activated factor VII was used until discharge; this was later replaced with emicizumab. After 18 months, the patient is without neurological sequelae and has not experienced subsequent bleeding episodes. We review the available literature and discuss the relevance of emicizumab compared with standard therapies in the context of spontaneous spinal epidural hematoma.

Practical considerations for nonfactor-replacement therapies in the treatment of haemophilia with inhibitors

New therapeutic agents for haemophilia with inhibitors that are in development or already licensed are expected to provide transformative treatment options. Many of these new therapies are not based on simply replacing the missing factor; new strategies include bispecific antibody technology that mimics factor VIII coagulation function (emicizumab), and inhibition of anticoagulant proteins such as tissue factor pathway inhibitor (eg PF-06741086) and antithrombin (eg fitusiran). These agents are administered subcutaneously and should significantly reduce treatment burden and increase the ability to deliver prophylaxis for patients. Limited real-world data and validated practical guidance on these recently licensed/upcoming treatments resulted in the authors convening to discuss recommendations on their use. Emicizumab is currently the only licenced nonfactor therapy; thus, our recommendations focus on this product. Target candidates for emicizumab prophylaxis are difficult-to-treat patients with haemophilia A and inhibitors and/or venous access issues, frequent bleeds and target joints. In case of breakthrough bleeding while receiving emicizumab, patients still require treatment with bypassing agents; the adjunct treatment of choice is recombinant activated factor VII. This treatment is also recommended to prevent bleeds in patients with inhibitors undergoing surgery. Our recommendations on suitable laboratory assays and monitoring new products, as well as the benefit of patient-reported outcomes (such as pain and physical activity levels), are included. We also briefly discuss future treatment options for patients with haemophilia B and inhibitors. Although these nonfactor treatments offer great promise, further data and real-world evidence are needed.

Role of Small Intestine and Gut Microbiome in Plant-Based Oral Tolerance for Hemophilia

Fusion proteins, which consist of factor VIII or factor IX and the transmucosal carrier cholera toxin subunit B, expressed in chloroplasts and bioencapsulated within plant cells, initiate tolerogenic immune responses in the intestine when administered orally. This approach induces regulatory T cells (Treg), which suppress inhibitory antibody formation directed at hemophilia proteins induced by intravenous replacement therapy in hemophilia A and B mice. Further analyses of Treg CD4+ lymphocyte sub-populations in hemophilia B mice reveal a marked increase in the frequency of CD4+CD25-FoxP3-LAP+ T cells (but not of CD4+CD25+FoxP3+ T cells) in the lamina propria of the small but not large intestine. The adoptive transfer of very small numbers of CD4+CD25-LAP+ Treg isolated from the spleen of tolerized mice was superior in suppression of antibodies directed against FIX when compared to CD4+CD25+ T cells. Thus, tolerance induction by oral delivery of antigens bioencapsulated in plant cells occurs via the unique immune system of the small intestine, and suppression of antibody formation is primarily carried out by induced latency-associated peptide (LAP) expressing Treg that likely migrate to the spleen. Tolerogenic antigen presentation in the small intestine requires partial enzymatic degradation of plant cell wall by commensal bacteria in order to release the antigen. Microbiome analysis of hemophilia B mice showed marked differences between small and large intestine. Remarkably, bacterial species known to produce a broad spectrum of enzymes involved in degradation of plant cell wall components were found in the small intestine, in particular in the duodenum. These were highly distinct from populations of cell wall degrading bacteria found in the large intestine. Therefore, FIX antigen presentation and Treg induction by the immune system of the small intestine relies on activity of a distinct microbiome that can potentially be augmented to further enhance this approach.

Evaluation of the Pharmacokinetics, Pharmacodynamics, and Safety of a Single Dose of Emicizumab in Healthy Chinese Subjects

This phase 1, open‐label, single‐center study evaluated the pharmacokinetics (PK), pharmacodynamics, safety, and tolerability of single‐dose emicizumab in healthy Chinese males. Overall, 16 subjects received a single subcutaneous dose of 1‐mg/kg emicizumab. Blood samples were obtained before dosing on day 1 and at regular intervals over 16 weeks after dosing for PK evaluation. A single 1‐mg/kg subcutaneous dose of emicizumab was safe and well tolerated in healthy Chinese male subjects in the study. Mean (± standard deviation) area under the concentration‐time curve from time 0 to infinity and maximum concentration were 287 ± 74.2 μg⋅d/mL and 7.11 ± 1.77 μg/mL, respectively, with a terminal half‐life of 26.7 (±4.3) days. Emicizumab administration did not show significant impact on pharmacodynamic markers tested, which mostly remained stable throughout the study. One subject tested positive for antidrug antibody, with no impact on his PK or safety profile. Compared with results from healthy Japanese and Caucasian subjects receiving the same dose in previous clinical trials, the current results further indicated the absence of difference of emicizumab PK profile across Chinese, Japanese, and Caucasian subjects, validating the use of similar therapeutic doses in Asian and non‐Asian populations.

[Therapeutic antibodies in hemostasis. From the past to the future]

L’hémostase est un processus complexe qui implique de nombreux acteurs cellulaires et moléculaires. En pathologie, les thromboses d’une part, et les pathologies hémorragiques constitutionnelles dominées par l’hémophilie d’autre part, ont bénéficié ces dernières années du développement d’anticorps thérapeutiques qui révolutionnent aujourd’hui la prise en charge des malades.

Emicizumab for the treatment of haemophilia A: a narrative review

One of the most serious complications of the treatment of severe haemophilia A is the development of alloantibodies against exogenous factor VIII (FVIII). Inhibitors render factor replacement therapy ineffective, exposing patients to a remarkably high risk of morbidity and mortality. Besides the well-known bypassing agents (i.e. activated prothrombin complex concentrate and recombinant activated factor VII) used to treat or prevent bleeding in haemophilia patients with inhibitors, there is growing interest in newer haemostatic therapies that are not based on the replacement of the deficient FVIII. This review will focus on the most interesting among these innovative therapies, emicizumab, and will provide an update on its current stage of clinical development.

The evolution of recombinant factor replacement for hemophilia

Hemophilia A and Hemophilia B are the most common of the severe bleeding disorders and are caused by a deficiency in blood clotting factor VIII or factor IX respectively. Factor replacement therapy has been the cornerstone of treatment to treat life threatening bleeds and prevent joint disease. The treatment of hemophilia has evolved tremendously over the past five decades from fresh frozen plasma as the only available therapy to more specific plasma-derived and recombinant-derived factor replacement. Now due to innovations in bioengineering, there are even more efficacious factor replacement options available to patients. Here we review these recent advancements and their impact on the treatment and management of hemophilia.

Emicizumab: Review of the literature and critical appraisal

INTRODUCTION

Emicizumab-kywh (ACE910) is a recombinant, humanized, asymmetric bispecific antibody that functions to bring activated FIX (FIXa) and zymogen FX into an appropriate steric conformation to medicate the activation of FX to FXa thereby mimicking the cofactor function of FVIIIa.

AIM

The objective of this manuscript was to review the development and potential role for emicizumab in the treatment of patients with haemophilia A with and without inhibitors.

METHODS

A Cochrane Library and PubMed (MEDLINE) search focusing on emicizumab in haemophilia was conducted.

RESULTS

In total, 37 citations were retrieved and serve as the database for the literature reviewed herein. Once-weekly subcutaneous injection of emicizumab at three dose levels has been shown to be effective as prophylaxis to prevent bleeding in a majority haemophilia A patients with inhibitors to FVIII. Likewise, prevention of bleeding was also observed in more than two thirds of patients without inhibitors to FVIII. One antidrug antibody to emicizumab has been reported in over 600 treated patients, two have developed thromboembolic events and three thrombotic microangiopathy. These thrombotic complications have occurred in conjunction with FVIII-bypassing agents, and none have been observed following recommendations from the manufacturer regarding concomitant use of bypassing agents. The median annual treated bleeding rates were decreased in patients with as well as those without an inhibitor to FVIII.

CONCLUSION

The principal advantage of emicizumab is subcutaneous administration and effectiveness irrespective of the presence of inhibitors. Emicizumab could conceivably represent a new epoch in the treatment of people with haemophilia A.