Hemophilia in a Changing Treatment Landscape

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.

Real-World Amount of Clotting Factor Concentrates Dispensed and Annual Medical Expenditures for Japanese Patients with Hemophilia B

Introduction

Until extended half-life (EHL) factor IX (FIX) concentrates became available in Japan in 2010, patients with hemophilia B received intravenous FIX replacement therapy with standard half-life (SHL) FIX concentrates.

Purpose

To investigate the amount of factor dispensed and the associated medical expenditures for the treatment of hemophilia B in the real-world clinical setting in Japan.

Methods

This retrospective study comprised patients with hemophilia B (N=197) who had filled prescriptions for FIX concentrates reported in Japan's Medical Data Vision database from 2015 to 2019. Patients were included if they had 2 or more prescriptions for the same FIX concentrates within the first 6 months of the study period and the interval between prescriptions was at least 2 weeks.

Results

Since 2015, there was a decrease in the proportion of patients using SHL FIX concentrates and a corresponding increase in international units of dispensed EHL FIX concentrates. Median annualized dispensed dosages (IU/kg body weight) of EHL FIX concentrates were lower than for SHL concentrates for outpatient use only. Annual total health care expenditures per patient and annual expenditures for prescribed FIX concentrates increased each year during the study period. Following a switch from an SHL to an EHL concentrate, the median amount of prescribed FIX concentrate decreased slightly, although median total health care expenditures and FIX concentrate expenditures increased.

Conclusion

In the real-world setting in Japan, medical expenditures and the proportion of patients prescribed EHL FIX concentrates for the treatment of hemophilia B have increased.

Application of systems biology to identify pharmacological mechanisms of thrombotic microangiopathy evoked by combined activated prothrombin complex concentrate and emicizumab

Emicizumab is a bispecific monoclonal antibody that substitutes for the function of missing or deficient factor VIII (FVIII) in people with hemophilia A (PwHA). Long-term safety and efficacy of emicizumab have been demonstrated in several clinical trials. Nevertheless, in the first of these, three cases of thrombotic microangiopathy (TMA) occurred in PwHA treated with emicizumab receiving high doses of activated prothrombin complex concentrate (aPCC), a bypassing agent used for treating breakthrough bleeds when FVIII neutralizing antibodies (inhibitors) make FVIII replacement ineffective. The aim of the present work is to offer a method to elucidate the pathophysiological and pharmacological mechanisms involved in this treatment-induced TMA. Systems biology and machine learning-based Therapeutic Performance Mapping System is a validated in silico technology that allowed us to construct models of potential mechanisms behind induced TMA. Two drug combinations were modeled and assessed: emicizumab plus aPCC and emicizumab plus recombinant activated factor VII (another bypassing agent). Our models showed that both combinations were related to activation of the coagulation cascade. However, mechanisms involved mainly in platelet activation and possibly in complement activation were detected only for emicizumab plus aPCC, potentially explaining the occurrence of TMA only in this combination.

Bleeding events in people with congenital haemophilia A without factor VIII inhibitors receiving prophylactic factor VIII treatment: A systematic literature review

BACKGROUND

Evidence on bleeding rates in people with congenital haemophilia A (PwcHA) without inhibitors on factor VIII (FVIII) replacement products is inconsistent.

AIM

This systematic literature review assessed bleeding outcomes in PwcHA using FVIII-containing products as prophylactic treatment.

METHODS

A search was conducted using the bibliographic databases Medline, Embase and Cochrane Central Register of Controlled Trials on the Ovid platform. The search involved a bibliographic review of clinical trial studies, routine clinical care studies and registries and a search of ClinicalTrials.gov, EU Clinical Trials Register and conference abstracts.

RESULTS

The search yielded 5548 citations. A total of 58 publications were included for analysis. In 48 interventional studies, the pooled estimated mean (95% confidence interval [CI]) annualized bleeding rate (ABR), annualized joint bleeding rate (AJBR) and proportion of participants with zero bleeding events were 3.4 (3.0-3.7), 2.0 (1.6-2.5), and 38.5% (33.1-43.9), respectively. In 10 observational studies, the pooled estimated mean (95% CI) ABR, AJBR and proportion of participants with zero bleeding events were 4.8 (4.0-5.5), 2.6 (2.1-3.2), and 21.8% (19.9-47.5), respectively. A large variation in mean effect size for ABR, AJBR and zero bleeding event data across cohorts and cohort types was observed. Funnel plots indicated potential reporting bias for publications incorporating ABR and AJBR data across both interventional and observational studies.

CONCLUSION

This meta-analysis shows that PwcHA without inhibitors still have bleeds despite FVIII prophylaxis. Improved standardization on capturing and reporting bleeding outcomes is needed so that effective comparisons between treatments can be made.

Between Scylla and Charybdis: thrombosis in children with hemophilia

Thromboembolism is an infrequent complication in children with hemophilia that has been traditionally associated with the presence of a central venous access device. Novel rebalancing agents have shown promising results as prophylactic therapies to minimize the risk of bleeding but both thromboembolism and thrombotic microangiopathy have been reported as complications. The management of thrombosis in children with hemophilia is particularly challenging given the inherent risk of bleeding. In this paper, we present clinical vignettes to review the literature, highlight challenges, and describe our approach to managing thromboembolism in children with hemophilia.

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.

Nonreplacement therapy for hemophilia in low-income countries: experience from a prospective study in Ivory Coast

Background

Hemophilia management has fundamentally evolved over the last decades with the development of ground-breaking therapies. Because of their mode of action and biochemical properties, these innovative therapies that are available in developed countries could be readily implemented among people from low-income countries who are either not or inadequately treated with clotting factor concentrates (CFCs).

Objectives

We aimed at evaluating the impact of prophylaxis with emicizumab, a bispecific monoclonal antibody mimicking the FVIII activity administered subcutaneously, among boys with severe hemophilia A (HA) from the Ivory Coast, where access to CFCs is limited to humanitarian aid.

Methods

We prospectively collected data on the implementation and outcomes of prophylaxis with emicizumab, in 33 Ivorian boys aged 2 to 13 years with severe HA (with and without inhibitors). Bleeds, CFC consumption, quality of life and satisfaction of the patients and their parents were assessed.

Results

Overall, 12 months after initiating emicizumab, a 99% reduction in bleeding rates was observed, with a raise from 18% to 100% of boys having zero spontaneous joint bleeds. Three boys required a single FVIII infusion following a traumatic bleed. Health-related quality of life measures significantly improved, and perception of treatment efficacy was positively rated in children and parents. Acceptance, tolerance, and adherence were excellent. Emicizumab was instrumental in successfully implementing uninterrupted, highly efficacious, and well-tolerated prophylaxis in 72% of the Ivorian children aged ≤ 13 years identified with severe hemophilia A.

Conclusion

These data illustrate how innovative and disruptive nonreplacement therapies that are already accessible in developed countries could potentially provide equity in care by profoundly and rapidly modifying hemophilia burden with a magnified impact in low-income countries.

Current Understanding of Inherited Modifiers of FVIII Pharmacokinetic Variation

The inherited bleeding disorder hemophilia A involves the quantitative deficiency of the coagulation cofactor factor VIII (FVIII). Prophylactic treatment of severe hemophilia A patients with FVIII concentrates aims to reduce the frequency of spontaneous joint bleeding and requires personalized tailoring of dosing regimens to account for the substantial inter-individual variability of FVIII pharmacokinetics. The strong reproducibility of FVIII pharmacokinetic (PK) metrics between repeat analyses in the same individual suggests this trait is genetically regulated. While the influence of plasma von Willebrand factor antigen (VWF:Ag) levels, ABO blood group, and patient age on FVIII PK is well established, estimates suggest these factors account for less than 35% of the overall variability in FVIII PK. More recent studies have identified genetic determinants that modify FVIII clearance or half-life including VWF gene variants that impair VWF-FVIII binding resulting in the accelerated clearance of VWF-free FVIII. Additionally, variants in receptors that regulate the clearance of FVIII or the VWF-FVIII complex have been associated with FVIII PK. The characterization of genetic modifiers of FVIII PK will provide mechanistic insight into a subject of clinical significance and support the development of personalized treatment plans for patients with hemophilia A.

Co-administration of FVIII with IVIG reduces immune response to FVIII in hemophilia A mice

Hemophilia A is an X-linked recessive congenital bleeding disorder. Exogenous infusion of FVIII is the treatment of choice, and the development of immunoglobulins against FVIII (inhibitors) remains the major challenge in clinical management of the disease. Here, we investigated the effect of co-administration of FVIII with intravenous immunoglobulin (IVIG) on the development of inhibitors in previously untreated hemophilia A mice. A group of hemophilia A mice (C57BL/6^FVIII-/-) received weekly injections of recombinant human FVIII (rFVIII) for twelve consecutive weeks while a second group received co-injections of rFVIII + IVIG. An in-house enzyme-linked immunosorbent assay (ELISA) was designed to detect antibodies to rFVIII. Every mouse in the first group developed antibodies to rFVIII. In contrast, mice treated with rFVIII + IVIG showed significantly lower antibody titers. Interestingly, when co-administration of IVIG was discontinued after 12 weeks in some mice (rFVIII continued), these mice experienced an increase in antibody titer. In contrast, mice that continued to receive rFVIII + IVIG retained significantly lower titers. In conclusion, prophylactic rFVIII co-administration with IVIG modulated the immune response to FVIII and resulted in decreased anti-FVIII antibody titer. These findings suggest that co-injection therapy with IVIG could potentially be effective in the management of hemophilia A patients at risk of inhibitor development.

Post-procedural bleeding rate and haemostatic treatment use for dental procedures before and after the implementation of a standardized protocol for people with inherited bleeding disorders

INTRODUCTION

Persons with inherited bleeding disorders are at a substantial risk of bleeding following dental procedures.

AIM

To compare the outcomes and use of haemostatic treatment pre- and post-implementation of a standardized protocol for dental procedures at a Hemophilia Treatment Centre.

METHODS

We conducted a retrospective cohort study of outpatient and inpatient dental procedures and maxillofacial surgeries sustained by people with bleeding disorders treated at a comprehensive Hemophilia Treatment Centre (2013-2020), comparing patients' outcomes before and after the introduction of the protocol in 2018. The protocol, built using a multidisciplinary approach, suggested haemostatic treatment based on the invasiveness of the dental procedure and the proposed anaesthesia. Our primary outcome was the rate of procedural bleeding leading to medical or dental reintervention within 10 days. Secondary outcomes included the use of systemic haemostatic treatment and treatment-related adverse effects.

RESULTS

Overall, 137 dental procedures in 95 patients (median age: 29 years; 78% males; 74% haemophilia, 14% von Willebrand disease, 12% other disorders) were included. Seventeen procedural bleedings were reported (12.4%). Procedural bleeding occurred in 14.8% and 8.9% of patients in the control and intervention groups (p = .304). No major bleeding occurred. Tranexamic acid was used more consistently after protocol implementation (72.8% vs. 89.3%, p = .019), while factor concentrates use decreased (65.4% vs. 44.6%, p = .016), and desmopressin use remained constant (46.4% vs. 32.1%, p = .100). No treatment-related adverse effects were reported.

CONCLUSION

The use of a standardized protocol increased the use of tranexamic acid, with a nonstatistically significant reduction in procedural bleeding rate.

Factor-mimetic and rebalancing therapies in hemophilia A and B: the end of factor concentrates?

Hemophilia A (HA) and B are inherited bleeding disorders caused by a deficiency of factor VIII or factor IX, respectively. The current standard of care is the administration of recombinant or purified factor. However, this treatment strategy still results in a high economic and personal burden to patients, which is further exacerbated by the development of inhibitors—alloantibodies to factor. The treatment landscape is changing, with nonfactor therapeutics playing an increasing role in what we consider to be the standard of care. Emicizumab, a bispecific antibody that mimics the function of factor VIIIa, is the first such nonfactor therapy to gain US Food and Drug Administration approval and is rapidly changing the paradigm for HA treatment. Other therapies on the horizon seek to target anticoagulant proteins in the coagulation cascade, thus “rebalancing” a hemorrhagic tendency by introducing a thrombotic tendency. This intricate hemostatic balancing act promises great things for patients in need of more treatment options, but are these other therapies going to replace factor therapy? In light of the many challenges facing these therapies, should they be viewed as a replacement of our current standard of care? This review discusses the background, rationale, and potential of nonfactor therapies as well as the anticipated pitfalls and limitations. This is done in the context of a review of our current understanding of the many aspects of the coagulation system.

Musculoskeletal ultrasound in hemophilia: Results and recommendations from a global survey and consensus meeting

Introduction

For persons with hemophilia, optimization of joint outcomes is an important unmet need. The aim of this initiative was to determine use of ultrasound in evaluating arthropathy in persons with hemophilia, and to move toward consensus among hemophilia care providers regarding the preferred ultrasound protocols for global adaptation.

Methods

A global survey of hemophilia treatment centers was conducted that focused on understanding how and why ultrasound was being used and endeavored to move toward consensus definitions of both point‐of‐care musculoskeletal ultrasound (POC‐MSKUS) and full diagnostic ultrasound, terminology to describe structures being assessed by ultrasound, and how these assessments should be interpreted. Next, an in‐person meeting of an international group of hemophilia health care professionals and patient representatives was held, with the objective of achieving consensus regarding the acquisition and interpretation of POC‐MSKUS and full diagnostic ultrasound for use in the assessment of musculoskeletal (MSK) pathologies in persons with hemophilia.

Results

The recommendations were that clear definitions of the types of ultrasound examinations should be adopted and that a standardized ultrasound scoring/measurement system should be developed, tested, and implemented. The scoring/measurement system should be tiered to allow for a range of complexity yet maintain the ability for comparison across levels.

Conclusion

Ultrasound is an evolving technology increasingly used for the assessment of MSK outcomes in persons with hemophilia. As adoption increases globally for clinical care and research, it will become increasingly important to establish clear guidelines for image acquisition, interpretation, and reporting to ensure accuracy, consistency, and comparability across groups.

Pharmacoeconomic Analysis of Hemophilia Care in Romania

Hemophilia, a congenital X linked disease, has the serious burden of bleeding, requiring life-long replacement with coagulation factors (CF). In the present day, there is a continuously improving treatment for this condition. Objective: Our observational, cross-sectional study aims at finding out whether a prophylactic replacement with CF is affordable from the point of view of its cost-effectiveness in our country. Material and methods: A cohort of 122 persons with hemophilia were included in this patient-reported outcome survey, and they answered a questionnaire consisting of 56 items, focused on 4 domains—socio-demographic, medical, quality of health/life and cost/cost-effectiveness. Results and discussion: The markers for quality of health/life were correlated with the direct and indirect costs of care, comparing subgroup 1 of patients with prophylactic vs. subgroup 2 with on-demand replacement. Based on the incremental quality adjusted life years and the incremental costs, we calculated the incremental cost-effectiveness ratio (ICER) proving that prophylaxis is more cost-effective than on-demand replacement on a long time basis. Conclusions: The ICER is a threshold recommending the reimbursement of costs for a life-long prophylactic replacement in our country.

Patients with hemophilia A and inhibitors: prevention and evolving treatment paradigms

Introduction: Novel non-replacement therapies (e.g. emicizumab) have improved the management of patients with hemophilia A with and without inhibitors while introducing new challenges and increasing the complexity of clinical decision-making.Areas covered: Use of emicizumab can substantially delay initial exposure to FVIII thereby altering the natural history of inhibitor development, but it remains unclear whether later exposure to FVIII might modify the incidence of inhibitor development. Moreover, decisions regarding initiation of immune tolerance induction (ITI) therapy in patients with newly diagnosed inhibitors have become more complicated since emicizumab was introduced. Using emicizumab in lieu of ITI has implications such as precluding the use of FVIII for breakthrough bleeds and surgery, and possibly impacting on patients' future ability to receive gene therapy. Although bypassing agents are the mainstay of managing acute bleeds and surgery in inhibitor patients, their concomitant use with novel therapies can be difficult to manage/monitor. Evidence from the HAVEN clinical trials program suggests that minor surgeries in inhibitor patients can be performed with emicizumab alone, whereas major surgeries require the use of perioperative bypassing agents.Expert opinion: Until the long-term effects of non-replacement therapies become known, patients who develop inhibitors should continue to receive ITI.