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.

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.

This study is an international, multicenter, open-label, single arm, prospective clinical trial and will evaluate the efficacy of prophylactic emicizumab administered on a scheduled basis to prevent bleeds in patients with acquired hemophilia A (AHA).

INTRODUCTION: Emicizumab is an effective new treatment option for people with hemophilia A (PwHA). The approved dosing regimens are based on body weight, without the necessity for laboratory monitoring. This assumes a clear dose-concentration-response relationship, with acceptable variability due to factors other than body weight. To investigate this assumption, a systematic review on the pharmacokinetics (PK) and associated efficacy of emicizumab in humans was conducted. METHODS: The EMBASE, Pubmed and CENTRAL databases were systematically searched to November 2020 to identify studies on the PK data of emicizumab in humans. Data on the study, population, PK and efficacy (annualized bleeding rate of treated [joint] bleeds) were extracted and synthesized, and exposure effects modeling was performed using non-linear least squares regression in a maximum effect (Emax) model. RESULTS: The 15 included studies reported on data for 140 volunteers and 467 PwHA, including children (0 to <12 years) and adolescents and adults (≥12 years), both with and without factor VIII (FVIII) inhibitors. Emicizumab demonstrated dose-linear PK. The interindividual variability of trough concentrations was moderate (32%) and was similar across various subgroups, such as FVIII inhibitor status, age group and dosing interval. The control of bleeds did not further improve above emicizumab concentrations of 30 µg/mL, potentially enabling lower dosing in a substantial proportion of PwHA. CONCLUSION: This review supports body weight-based dosing, although individualized monitoring of emicizumab concentrations may allow for more cost-effective dosing.

BACKGROUND: Emicizumab (ACE910) bridges activated factor IX and factor X to restore the function of activated factor VIII, which is deficient in persons with hemophilia A. This phase 3, multicenter trial assessed once-weekly subcutaneous emicizumab prophylaxis in persons with hemophilia A with factor VIII inhibitors. METHODS: We enrolled participants who were 12 years of age or older. Those who had previously received episodic treatment with bypassing agents were randomly assigned in a 2:1 ratio to emicizumab prophylaxis (group A) or no prophylaxis (group B). The primary end point was the difference in bleeding rates between group A and group B. Participants who had previously received prophylactic treatment with bypassing agents received emicizumab prophylaxis in group C. RESULTS: A total of 109 male participants with hemophilia A with inhibitors were enrolled. The annualized bleeding rate was 2.9 events (95% confidence interval [CI], 1.7 to 5.0) among participants who were randomly assigned to emicizumab prophylaxis (group A, 35 participants) versus 23.3 events (95% CI, 12.3 to 43.9) among those assigned to no prophylaxis (group B, 18 participants), representing a significant difference of 87% in favor of emicizumab prophylaxis (P<0.001). A total of 22 participants in group A (63%) had zero bleeding events, as compared with 1 participant (6%) in group B. Among 24 participants in group C who had participated in a noninterventional study, emicizumab prophylaxis resulted in a bleeding rate that was significantly lower by 79% than the rate with previous bypassing-agent prophylaxis (P<0.001). Overall, 198 adverse events were reported in 103 participants receiving emicizumab prophylaxis; the most frequent events were injection-site reactions (in 15% of participants). Thrombotic microangiopathy and thrombosis were reported in 2 participants each (in the primary analysis) who had received multiple infusions of activated prothrombin complex concentrate for breakthrough bleeding. No antidrug antibodies were detected. CONCLUSIONS: Emicizumab prophylaxis was associated with a significantly lower rate of bleeding events than no prophylaxis among participants with hemophilia A with inhibitors. (Funded by F. Hoffmann-La Roche and Chugai Pharmaceutical; HAVEN 1 ClinicalTrials.gov number, NCT02622321 .).

Haemophilia A is an X-linked hereditary bleeding disorder resulting from a deficiency or dysfunction of endogenous coagulation factor VIII (FVIII). Persons with haemophilia A (PwHA) suffer from spontaneous or provoked bleeding, predominantly into major joints, which eventually lead to painful and chronic disabling arthropathy. The primary goal in clinical management of haemophilia A is prevention of bleeding by self-administration of FVIII concentrates via intravenous injections. Prophylaxis with FVIII concentrates has effectively reduced treated bleeds from an annual average of 20-30 to 1-4. However, in approximately 30% of PwHA anti-FVIII antibodies (known as inhibitors) develop that interfere with FVIII replacement therapy. PwHA who develop inhibitors require alternative suboptimal therapy with (costly) bypassing agents (BPA). The first approved non-factor therapy is the bispecific, FVIII-mimicking antibody, emicizumab (Hemlibra®), which came available in the Netherlands in July 2018. Emicizumab is a humanized, bispecific antibody connecting factor IX and factor X enabling the activation of FX and subsequent thrombin generation. Emicizumab has shown to be highly effective prophylaxis in PwHA by achieving a complete eradication of treated bleeds in around 80% of PwHA (n = 374) during the second 24-week interval of treatment. Furter advantages of emicizumab are the subcutaneous administration and less frequent dosing intervals every 1, 2 or 4 weeks due to a long half-life (t ½: 28 days). Despite many PwHA are candidate for prophylaxis with emicizumab, cost limit widespread access. Currently, emicizumab is approved by F. Hoffmann-La Roche® with a loading dose of 3 mg/kg/week for four weeks and a maintenance dose of 1.5 mg/kg/week, 3 mg/kg/2 weeks or 6 mg/kg/4 weeks. These dose regimens were based on a pharmacometric approach instead of a dose finding study, and targeted a trough concentration (Ctrough) of 45 µg/ml by using pharmacokinetic (PK)simulations. Meanwhile long-term bleed data from the phase III and IV studies by the pharmaceutical company were included in pharmacokinetic (PK) and pharmacodynamic (PD) modelling studies, and the effective Ctrough was suggested at 30 µg/ml. Although this Ctrough of 30 µg/ml is substantially lower than the previous Ctrough (45 µg/ml), the dose regimens were not adjusted. Conventional dosing leads to mean concentrations of 55 µg/ml with two thirds of the observations between 40 and 70 µg/ml (i.e., SD of ±15 µg/ml). Emicizumab has been approved based on fixed body-weight-based dosing and therefore the concentration target might have been kept higher to avoid lower effectivity due to inter-patient variability. However, reduced dosing of emicizumab, either by extending the dosing interval or lowering the dose, without sacrificing its efficacy has been reported in small case series. Therefore, the investigators hypothesized that lower dosing of emicizumab targeted at Ctrough 30 μg/mL, is equally as effective and less costly in preventing bleeds as conventional dosing of emicizumab, and designed the DosEmi study to investigate the hypothesis in a large prospective cohort of adult and paediatric PwHA.

Patients with AHA who are eligible will receive two loading doses of the study drug, emicizumab (6mg/kg on day 1 and 3 mg/kg on day 2) followed by once weekly subcutaneous emicizumab (1.5 mg/kg). Immunosuppression will be given concurrently as per investigator discretion. The primary endpoint (bleed rate) will be assessed after 12 weeks on study drug. If partial remission of the AHA has not been achieved, an additional 12 weeks of study drug may be given. A historical cohort and a study conducted in parallel in Germany (NCT04188639) will serve as control groups for evaluation of secondary endpoints provided the study cohort are comparable.

BACKGROUND: Emicizumab is approved to prevent bleeding in patients with congenital haemophilia A with or without inhibitors. However, no randomized trials addressed the efficacy of emicizumab in acquired haemophilia A (AHA). AIMS: To report the clinical and biochemical response of emicizumab in AHA. METHODS: This single-centre retrospective study included seven adults with AHA between November 2020 and May 2022. We collected patient characteristics, laboratory coagulation parameters, the use of haemostatic agents, bleeds and thrombotic events. Treatment was monitored using chromogenic FVIII assays. The assay with human reagents assesses both the emicizumab FVIII-like-activity and native patient FVIII-activity. The assay with bovine reagents only measures the patients' native FVIII-activity as emicizumab does not bind to bovine reagents. RESULTS: Patients presented with spontaneous hematoma (n = 7), intramuscular bleeding (n = 2), haematuria (n = 2) and/or gastro-intestinal bleeding (n = 2). Six patients had major bleedings. At diagnosis, APTT was prolonged (91 seconds, IQR 73-103), FVIII activity was 0% (IQR 0-1) and FVIII inhibitor 182 BU/mL (IQR 104-228). Emicizumab was administered weekly (3 mg/kg) for 4 weeks, and thereafter every 2 weeks until regression of the inhibitor. Three patients received activated FVIIa (cumulative dose of 1.7 mg/kg, IQR 1.2-2.2). All bleedings were controlled after treatment initiation, without further bleeds. After starting emicizumab, FVIII-like activity reached ≥5% at 12 days (IQR 7-14), whereas recovery of the intrinsic FVIII-activity ≥5% occurred at 128 days (IQR 88-173), coinciding with the disappearance of the FVIII inhibitor. There were no safety issues. CONCLUSION: In this AHA case series, no new clinically relevant bleeds were observed after initiation of emicizumab in conjunction with standard immunosuppressive therapy.

Este artículo no tiene resumen

INTRODUCTION: Hemophilia is a serious bleeding disorder characterized by repeated bleeding episodes into joints and muscles which can lead to permanent disabilities. Treatment with factor replacement therapy has proven to be effective at preventing these complications; however, it can lead to formation of neutralizing antibodies termed inhibitors which significantly complicate the management of the disorder. These inhibitor patients suffer from increased morbidity and mortality and there has been a major unmet need for novel therapeutic approaches. Recently, one such therapy, emicizumab, has been licensed in the United States. Areas covered: This manuscript contains a detailed discussion of the mechanism of action, the clinical trial development program as well as a review of the benefits and risks of this novel agent. In addition, practical considerations for the use of the agent are also described. Expert commentary: Emicizumab represents a new class of medication for the treatment of hemophilia A which in the past has relied on factor replacement therapy and bypassing agent (alternative factor) therapy. Emicizumab fulfills two major unmet needs in patients with hemophilia who have FVIII inhibitors. First, it provides for a much more effective therapy for the prevention of bleeding and second it substantially reduces the treatment burden.