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

The underevaluated impacts of the therapeutic revolution of hemophilia on women and girls

The advent of new treatment options over the last decades has markedly improved the lives of male persons with hemophilia (PwH). However, this therapeutic revolution has not benefited women and girls with hemophilia (WGH) and symptomatic carriers of the disease to the same extent as their male counterparts. This inequity is primarily due to the exclusion of WGH from clinical trials and a failure to fully recognize their specific treatment needs. Additionally, the indirect impact of innovative therapies, when used for male PwH, on the lives of mothers, other relatives, and partners of these individuals has been largely overlooked until now. In addition to improving access of WGH and carriers to new hemostatic treatments and comprehensive hemophilia care, it is imperative to strive for alleviating the mental burden imposed on them by this chronic disease. The recently proposed concept of a "hemophilia-free mind," primarily focused on male PwH, should therefore also be applied to WGH, symptomatic carriers, and the predominantly female support network of PwH.

From a bispecific monoclonal antibody to gene therapy: A new era in the treatment of hemophilia A

The treatment of hemophilia A has progressed amazingly in recent years. Emicizumab, a bispecific-humanized monoclonal antibody, is able to improve coagulation by bridging activated factor IX and factor X. Emicizumab is administered subcutaneously and much less often compared to factor VIII products. It has low immunogenicity, does not require dose adjustment, and can be administered regardless of the presence of factor VIII inhibitors. Thrombin generation assays but not factor VIII activity are indicated to guide and monitor the treatment. Emicizumab has enabled the conversion of patients with severe forms into patients with milder forms of hemophilia A. It has reduced the number of bleeding episodes compared to both on-demand and prophylactic substitution therapy and has an excellent safety profile. Gene therapy can elevate factor VIII plasma levels for many years after a single treatment course, could offer long-term protection from bleeding episodes, and minimize or eliminate the need for substitutive treatment with factor VIII concentrates. Gene therapy can provoke an immune response, manifested by an increase in common liver enzymes, that require immunotherapy. Long term monitoring is necessary to identify possible adverse effects. Future objectives are: the development of an ideal viral vector, the possibility of its re-administration, the use of gene therapy in hemophiliac children, and determining whether it can be successfully used to induce immune tolerance to factor VIII ceteri paribus. The future will determine the place of each type of treatment and group of patients for which it is indicated.

Patient-centered pharmacovigilance: priority actions from the inherited bleeding disorders community

Pharmacovigilance, the science and practice of monitoring the effects of medicinals and their safety, is the responsibility of all stakeholders involved in the development, manufacture, regulation, distribution, prescription, and use of drugs and devices. The patient is the stakeholder most impacted by and the greatest source of information on safety issues. It is rare, however, for the patient to take a central role and exert leadership in the design and execution of pharmacovigilance. Patient organizations in the inherited bleeding disorders community are among the most established and empowered, particularly in the rare disorders. In this review, two of the largest bleeding disorders patient organizations, Hemophilia Federation of America (HFA) and National Hemophilia Foundation (NHF), offer insights into the priority actions required of all stakeholders to improve pharmacovigilance. The recent and ongoing increase in incidents raising safety concerns and a therapeutic landscape on the cusp of unprecedented expansion heighten the urgency of a recommitment to the primacy of patient safety and well-being in drug development and distribution.

Plain Language Summary

Patients at the center of product safety Every medical device and therapeutic product has potential benefits and harms. The pharmaceutical and biomedical companies that develop them must demonstrate that they are effective, and the safety risks are limited or manageable, for regulators to approve them for use and sale. After the product has been approved and people are using it in their daily lives, it is important to continue to collect information about any negative side effects or adverse events; this is called pharmacovigilance. Regulators, like the United States (US) Food and Drug Administration, the companies that sell and distribute the products, and healthcare professionals who prescribe them are all required to participate in collecting, reporting, analyzing, and communicating this information. The people with the most firsthand knowledge of the benefits and harms of the drug or device are the patients who use them. They have an important responsibility to learn how to recognize adverse events, how to report them, and to stay informed of any news about the product from the other partners in the pharmacovigilance network. Those partners have a crucial responsibility to provide clear, easy-to-understand information to patients about any new safety concerns that come to light. The community of people with inherited bleeding disorders has recently encountered problems with poor communication of product safety issues, prompting two large US patient organizations, National Hemophilia Foundation and Hemophilia Federation of America, to hold a Safety Summit with all the pharmacovigilance network partners. Together they developed recommendations to improve the collection and communication of information about product safety so that patients can make well-informed, timely decisions about their use of drugs and devices. This article presents these recommendations in the context of how pharmacovigilance is supposed to work and some of the challenges encountered by the community.

Kinetic analysis of ternary and binary binding modes of the bispecific antibody emicizumab

The binding properties of bispecific antibodies (bsAb) are crucial for their function, especially when two antigens are targeted on the same cell surface. Dynamic interactions between each of the antibody's arms and its cognate target cause the formation and decay of a biologically functional ternary complex. How association and dissociation processes work cooperatively, and how they influence the avidity of the ternary complex, is still poorly understood. Here, we present a biosensor assay for the simultaneous measurement of the binding kinetics of the therapeutic bsAb emicizumab (Hemlibra®) and its two targets, the blood coagulation factors IX and X (FIX, FX). We describe an automated workflow to characterize binary and ternary-binding modes, utilizing a Y-shaped DNA nanostructure to immobilize the antigens on a sensor and to emulate conditions on a cell or platelet surface by presenting the antigens with optimal accessibility for the bsAb flown over the sensor as analyte. We find that emicizumab binds FX much stronger than FIX (K_d = 0.05 µM vs. 5 µM, t_1/2 = 20 s vs. 1 s) with profound consequences on the avidity of the ternary complex, which is dominated by FX's binding properties and a hand-off mechanism from FX to FIX. Moreover, formation and decay of the ternary complex depend on the bsAb concentration during the association phase. Emicizumab's in-vivo mode of action and the catalytic activation of FX can be rationalized from the analyzed binding kinetics. The assay and workflow are well suited for the screening of bispecific binders in drug discovery and provide valuable new kinetic information.Abbreviations: bsAb: bispecific antibody; FVIII/FIX/FX: coagulation factors VIII/IX/X; SPR: surface plasmon resonance; k_on: association rate constant; k_off: dissociation rate constant; K_D: equilibrium dissociation constant; t_1/2: dissociation half-life.

The lived experience of a novel disruptive therapy in a group of men and boys with haemophilia A with inhibitors: Emi & Me

BACKGROUND

People with haemophilia A and inhibitors (PwHi) suffer more orthopaedic complications, bleeding and pain than those without inhibitors. The advent of emicizumab as a prophylactic treatment has led to a reduction in bleed frequency and a significant improvement in overall quality of life. No research to date has examined the nature of this improvement on treated individuals and their families.

AIMS

The Emi & Me study aims to capture the real-life experience of using emicizumab for PwHi and their families.

METHODS

Participants were recruited through treatment centres, social media and by word of mouth. Each participant and a family member, if available, took part in a semistructured qualitative interview. All interviews were recorded, transcribed verbatim and analysed thematically. All elements of the study were reviewed by local statutory authorities and informed consent was sought from all participants.

RESULTS

Fifteen PwHi, mean age 27.2 years (range 8-63 years), most with a family member, participated in a single qualitative interview online (n = 13), by telephone (n = 1) or in person (n = 1). Mean time on emicizumab was 2.26 years (range 1-5 years). Six major themes emerged: bleeds; pain; treatment burden; control; freedom (for both PwHi and family members) and missed potential. Emicizumab prophylaxis has delivered significant improvements in the lives of the participants. Despite these improvements, some participants felt that their pre-existing physical disabilities and the lack of physiotherapy provision had prevented them achieving similar improvements in their functional ability.

CONCLUSION

This study shows that in reducing bleeds, pain and treatment burden, emicizumab had given PwHi greater control over their condition, allowing a sense of freedom they had not experienced with factor VIII or bypassing agent prophylaxis. However, for emicizumab to be truly effective, there is a need to ensure the continued availability and accessibility of robust multidisciplinary support services. Without this, it is unlikely that PwHi will realize the life-changing potential offered either by emicizumab or any other novel treatment approach.

PATIENT OR PUBLIC CONTRIBUTION

A patient participant (who did not wish to be included as an author of the paper) was involved in the design of the study protocol and interview guide.

Bispecific antibodies for the treatment of hemophilia A

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Disruptive technology and hemophilia care: The multiple impacts of emicizumab

Emicizumab, a bispecific antibody mimicking the action of factor VIII (FVIII), is currently the first and only approved and increasingly accessible disruptive treatment option for hemophilia A, a disease so far mainly treated with frequent intravenous infusions of FVIII concentrates or bypassing agents in case of inhibitor development. Other disruptive treatments are expected to follow, such as agents that rebalance coagulation and gene therapy with the ambition of curing hemophilia. While these treatment options represent major achievements or expectations, their adoption and implementation should consider their multiple direct and indirect, immediate or delayed, consequences on hemophilia care globally. It is these multiple changes, present and future, already visible or hypothetical, that this article intends to review and explore.

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.

Mortality, life expectancy, and causes of death of persons with hemophilia in the Netherlands 2001-2018

BACKGROUND

Treatment of patients with hemophilia has advanced over the past decades, but it is unknown whether this has resulted in a normal life expectancy in the Netherlands.

OBJECTIVE

This observational cohort study aimed to assess all-cause and cause-specific mortality in patients with hemophilia in the Netherlands between 2001 and 2018 and to compare mortality and life expectancy with previous survival assessments from 1973 onward.

PATIENTS/METHODS

All 1066 patients with hemophilia who participated in a nationwide survey in 2001 were followed until July 2018.

RESULTS

Information on 1031 individuals (97%) was available, of whom 142 (14%) deceased during follow-up. Compared with the general Dutch male population, mortality of patients with hemophilia was still increased (standardized mortality ratio: 1.4, 95% confidence interval: 1.2-1.7). Intracranial bleeding and malignancies were the most common causes of death. Estimated median life expectancy of patients with hemophilia was 77 years, 6 years lower than the median life expectancy of the general Dutch male population (83 years). Over the past 45 years, death rates of patients with hemophilia have consistently decreased, approaching the survival experience of the general population. Over the past decades, mortality due to human immunodeficiency virus and hepatitis C virus infections has decreased, death due to intracranial hemorrhages has increased, and death due to ischemic heart disease has remained consistently low over time.

CONCLUSIONS

Survival in patients with hemophilia in the Netherlands has improved over time but is still lower than that of the general population.

Should emicizumab be used in patients with acquired hemophilia A?

Emicizumab is currently approved to prevent bleeding in patients with congenital hemophilia A with or without neutralizing antibodies (inhibitors) against factor VIII (FVIII). Here, we present a case-based discussion of its potential use in acquired hemophilia A (AHA), a severe bleeding disorder caused by autoantibodies against FVIII. State-of-the-art management is based on bypassing agents (recombinant factor VIIa, activated prothrombin complex concentrate) and recombinant porcine FVIII; immunosuppressive therapy (corticosteroids, rituximab, cyclophosphamide) is used to suppress autoantibody formation. Case reports and one series suggest that emicizumab can reduce the risk of bleeding and the requirement for hemostatic therapy until remission of AHA is achieved. Further, it may allow to postpone the start of immunosuppressive therapy or to use less intense regimens. However, the risk-benefit assessment of emicizumab in AHA is difficult because demographic and clinical characteristics are different compared with congenital hemophilia. Prospective clinical trials are needed before the use of emicizumab can be recommended in AHA.