Current Choices and Management of Treatment in Persons with Severe Hemophilia A without Inhibitors: A Mini-Delphi Consensus

BACKGROUND

Regular treatment to prevent bleeding and consequent joint deterioration (prophylaxis) is the standard of care for persons with severe hemophilia A, traditionally based on intravenous infusions of the deficient clotting FVIII concentrates (CFCs). In recent years, extended half-life (EHL) CFCs and the non-replacement agent emicizumab, subcutaneously administered, have reduced the treatment burden.

METHODS

To compare and integrate the opinions on the different therapies available, eight hemophilia specialists were involved in drafting items of interest and relative statements through the Estimate-Talk-Estimate (ETE) method ("mini-Delphi"), in this way reaching consensus.

RESULTS

Eighteen items were identified, then harmonized to 10, and a statement was generated for each. These statements highlight the importance of personalized prophylaxis regimens. CFCs, particularly EHL products, seem more suitable for this, despite the challenging intravenous (i.v.) administration. Limited real-world experience, particularly in some clinical settings, and the lack of evidence on long-term safety and efficacy of non-replacement agents, require careful individual risk/benefit assessment and multidisciplinary data collection.

CONCLUSIONS

The increased treatment options extend the opportunities of personalized prophylaxis, the mainstay of modern management of hemophilia. Close, long-term clinical and laboratory follow-up of patients using newer therapeutic approaches by specialized hemophilia treatment centers is needed.

Comparisons of global coagulation potential and bleeding episodes in emicizumab-treated hemophilia A patients and mild hemophilia A patients

Emicizumab reduces bleeding events in patients with severe hemophilia A (HA). The coagulation potential of emicizumab at a clinical dose appears to correspond to about 15 IU/dL of factor VIII activity (FVIII:C), the equivalent of converting from a severe to mild phenotype. However, the clinical and laboratory characteristics of HA patients receiving emicizumab (Emi-PwHA) compared with patients with mild HA (PwMHA) remain to be determined. We reviewed clinical data from Emi-PwHA (n = 63) and PwMHA (n = 15) and evaluated comprehensive coagulation function using Ca²⁺-triggered rotational thromboelastometry (ROTEM) and ellagic acid/tissue factor-triggered clot waveform analysis (modified CWA). The median FVIII:C in PwMHA was 13.0 (IQR 8.5-17.0) IU/dL. Bleeding patterns in both groups were similar and classified into three categories: (1) spontaneous bleeding, post-traumatic, (2) bleeding within 1-2 days, and (3) delayed bleeding after 1-2 weeks. The coagulation potential in Emi-PwHA with and without breakthrough bleeds was comparable. Furthermore, coagulation function in Emi-PwHA was equivalent to PwMHA, although time between treatment and hospitalization for breakthrough bleeds in PwMHA appeared to be longer than those in Emi-PwHA. The coagulation potential and bleeding patterns appeared to be similar in Emi-PwHA and PwMHA, indicating that emicizumab-driven coagulation potential reflected mild HA.

Early real-world experience with emicizumab and concomitant factor VIII replacement products in adult males with Hemophilia A without inhibitors

AIMS

To assess real-world use of emicizumab in adult people with hemophilia A (PwHA) without inhibitors including healthcare resource utilization (HCRU) and costs.

MATERIALS AND METHODS

Adult, male PwHA without inhibitors initiating emicizumab (index date) were identified using IBM MarketScan after 4 October 2016. Patients were required to have continuous health insurance coverage for ≥180 days prior to and ≥90 days after index date and have ≥90 days of continuous use of emicizumab. Patients were followed until treatment gap, disenrollment, or end of data. Results were reported overall and among a subgroup with prior factor VIII (FVIII) prophylaxis. Emicizumab use, concomitant FVIII treatment use, HCRU, and costs were assessed separately over baseline, the emicizumab induction period, emicizumab maintenance period, and annualized.

RESULTS

Among the 71 emicizumab patients (FVIII prophylaxis subgroup: 52) included in the study, the mean age was 35 (subgroup: 34) years and mean follow-up was 12 (subgroup: 11.1) months. At baseline, the annualized mean total healthcare cost was $532,948 (subgroup: $645,727). After emicizumab initiation, per-patient-per-month (PPPM) HCRU was higher in the emicizumab induction period compared to the maintenance period with higher monthly FVIII fills/in-office administrations (0.37 vs 0.17), non-FVIII outpatient visits (2.23 vs 1.55), and emergency department visits (0.06 vs 0.03). The FVIII prophylaxis subgroup yielded similar HCRU trends. Hemophilia treatment costs accounted for over 95% of total healthcare costs. The annualized mean cost was $50,491 (subgroup: $61,512) for concomitant FVIII treatment and $777,171 (subgroup: $793,168) for emicizumab and concomitant FVIII treatment for the first year of emicizumab treatment.

CONCLUSION

This study represented experience with emicizumab after the approval for PwHA without inhibitors. The study cohort may not be representative of all PwHA taking emicizumab. The findings highlight the continued burden of treatment and healthcare cost for PwHA without inhibitors despite advances in treatment options.

Emicizumab in pediatric hemophilia: Bleeding and surgical outcomes from a single-center retrospective study

Real-world data describing emicizumab prophylaxis in pediatric hemophilia A is limited with current literature providing a heterogenous approach to procedural management. We performed a retrospective review on the 28 patients who have been treated with emicizumab prophylaxis at Texas Children's Hospital from 2018 to 2021. After starting emicizumab, the mean annualized bleeding rate reduced from 3.61 to 0.44. Seven surgical procedures were performed in the cohort, and all treated with pre- and postoperative factor replacement resulting in one minor bleeding event. We demonstrate a successful experience with emicizumab prophylaxis and safe perioperative approach with a focus on minimizing postoperative bleeding.

Real-world experience on the tolerability and safety of emicizumab prophylaxis in paediatric patients with severe haemophilia A with and without FVIII inhibitors

BACKGROUND

Emicizumab is a bispecific monoclonal antibody that bridges activated factor (F) IX and FX, and maintains haemostasis in patients with haemophilia A (PwHA). As a novel agent, many questions remain unanswered about the loss of emicizumab efficacy due to anti-drug antibody (ADA) development, the incidence of inhibitor recurrence in previously tolerized patients, and the risk of de novo inhibitor development.

AIM

To present real-world experience regarding tolerability, side effects, and outcomes of adverse events of emicizumab prophylaxis in paediatric PwHA.

METHODS

Data on tolerability, compliance, adverse events, and laboratory results of paediatric patients receiving emicizumab prophylaxis, treated at the Haemophilia Comprehensive Care Centre, at Birmingham Children's Hospital between March 2018 and June 2021, were collected.

RESULTS

Our results showed that out of 52 patients, four experienced minor adverse events, two developed headaches, one developed abdominal pain and nausea, and one developed injection site reactions. Moreover, four patients experienced major adverse events, including severe headaches, major bleeding events, development of ADAs, and recurrence of inhibitors. Emicizumab prophylaxis was discontinued in three patients (5.7% of the cohort) due to adverse events. In addition, emicizumab was discontinued in one patient because of poor compliance. No adverse events were reported in previously untreated/minimally treated patients, represented by four patients in our cohort.

CONCLUSIONS

The real-world experience of emicizumab prophylaxis in our cohort showed that emicizumab was safe and well tolerated in paediatric PwHA with and without inhibitors. Long-term assessment is crucial to monitor major adverse events, recurrence of inhibitors, and development of ADAs.

B cell-activating factor modulates the factor VIII immune response in hemophilia A

Inhibitors of factor VIII (FVIII) remain the most challenging complication of FVIII protein replacement therapy in hemophilia A (HA). Understanding the mechanisms that guide FVIII-specific B cell development could help identify therapeutic targets. The B cell-activating factor (BAFF) cytokine family is a key regulator of B cell differentiation in normal homeostasis and immune disorders. Thus, we used patient samples and mouse models to investigate the potential role of BAFF in modulating FVIII inhibitors. BAFF levels were elevated in pediatric and adult HA inhibitor patients and decreased to levels similar to those of noninhibitor controls after successful immune tolerance induction (ITI). Moreover, elevations in BAFF levels were seen in patients who failed to achieve FVIII tolerance with anti-CD20 antibody-mediated B cell depletion. In naive HA mice, prophylactic anti-BAFF antibody therapy prior to FVIII immunization prevented inhibitor formation and this tolerance was maintained despite FVIII exposure after immune reconstitution. In preimmunized HA mice, combination therapy with anti-CD20 and anti-BAFF antibodies dramatically reduced FVIII inhibitors via inhibition of FVIII-specific plasma cells. Our data suggest that BAFF may regulate the generation and maintenance of FVIII inhibitors and/or anti-FVIII B cells. Finally, anti-CD20/anti-BAFF combination therapy may be clinically useful for ITI.

Prophylaxis in children with haemophilia in an evolving treatment landscape

INTRODUCTION

For children with haemophilia, early initiation of prophylaxis is crucial to prevent life-threatening bleeds and maintain joint health throughout life. Options for prophylaxis have recently increased from replacement therapy with standard or extended half-life coagulation factor products to include other haemostasis products, such as the non-replacement therapy emicizumab.

AIM

To review key factors that determine the choice of prophylaxis in young children.

METHODS

Key clinical questions on the implementation of prophylaxis for haemophilia in children were identified and PubMed was searched for evidence supporting guidance on the implementation of prophylaxis.

RESULTS

The results of the literature search and the practical experience of the authors were used to build consensus on when to start prophylaxis, the pros and cons of the products available to guide the choice of product, and practical aspects of starting prophylaxis to guide the choice of regimen.

CONCLUSIONS

In this era of increasing therapeutic choices, available information about the range of treatment options must be considered when initiating prophylaxis in young children. Parents or care givers must be sufficiently informed to allow informed shared decision making. Although plentiful data and clinical experience have been gathered on prophylaxis with clotting factor replacement therapy, its use in young children brings practical challenges, such as the need for intravenous administration. In contrast, our relatively brief experience and limited data with subcutaneously administered non-replacement therapy (i.e., emicizumab) in this patient group imply that starting emicizumab prophylaxis in young children requires careful consideration, despite the more convenient route of administration.

Advances in the management of haemophilia: emerging treatments and their mechanisms

Mainstay haemophilia treatment, namely intravenous factor replacement, poses several clinical challenges including frequent injections due to the short half-life of recombinant factors, intravenous administration (which is particularly challenging in those with difficult venous access), and the risk of inhibitor development. These impact negatively upon quality of life and treatment compliance, highlighting the need for improved therapies. Several novel pharmacological therapies developed for haemophilia aim to rebalance the clotting cascade and potentially circumvent the aforementioned challenges. These therapies utilise a range of different mechanisms, namely: the extension of the circulating half-life of standard recombinant factors; the mimicking of factor VIII cofactor activity; rebalancing of coagulation through targeting of natural anticoagulants such as antithrombin and tissue factor pathway inhibitor; and inducing the production of endogenous factors with gene therapy. These therapies carry the potential of revolutionising haemophilia treatment by alleviating the current challenges presented by mainstay factor replacement. This review will provide an overview of the key trial findings related to novel therapies based on the mechanisms described above.

Predictors of the outcome of immune tolerance induction in patients with haemophilia A and inhibitors: The Brazilian Immune Tolerance (BrazIT) Study protocol

The development of inhibitors is the main complication of haemophilia A (HA) treatment. Immune tolerance induction (ITI) is the treatment of choice for inhibitor eradication. We describe the methodology of the Brazilian Immune Tolerance Induction (BrazIT) Study, aimed to identify clinical, genetic, and immune biomarkers associated with response to ITI and inhibitor recurrence. This cohort study includes people with HA (PwHA) and inhibitors (a) who require bypassing agents to treat and/or prevent bleeding, and (b) who are at any stage of ITI treatment. Patients are included in each haemophilia treatment centre (HTC). Factor VIII (FVIII) and inhibitor assessments are performed at local laboratories of each HTC. The ITI regimen followed the national protocol of the Brazilian Ministry of Health. All PwHA starts with low-dose ITI (50 IU/kg three times weekly); high-dose regimen (100 IU/kg daily) is used if there is lack of response to the low-dose ITI. Outcomes are classified as total or partial success, and failure. Standardized case report forms with clinical, laboratory, and treatment data are collected from medical files and interviews. Blood samples are collected for genetic and immune biomarkers at the time of inclusion in the study and at the end of ITI. The study is ongoing and, currently, 202/250 (80.8%) PwHA from 15 HTCs have been included. BrazIT Study is the largest cohort of PwHA and inhibitor under treatment with the same ITI regimen reported to date. This study is likely to contribute with novel predictors of ITI response.

An update of the current pharmacotherapeutic armamentarium for hemophilia A

INTRODUCTION

For several decades, we have seen unprecedented advances in novel therapy development for hemophilia A. These advances address the unmet need of replacement therapy, and they include the development of recombinant products with improved pharmacokinetics, subcutaneously administered products, and those with better efficacy and safety profiles in hemophilia A management.

AREAS COVERED

In this update of hemophilia A treatment, the author summarizes data from completed standard half-life FVIII products, extended half-life FVIII products and FVIII mimetic studies. All products have an acceptable safety profile. The standard half-life products, EHL-FVIII products and emicizumab are efficacious in the prevention and treatment of bleeds and for EHL-FVIII in the perisurgical setting.

EXPERT OPINION

Advances in pharmacotherapy for hemophilia A have been characterized by changing care goals from supportive care to eliminating infections, preventing inhibitors, and more recently achieving zero bleeds in many patients. While gene therapy has the potential for functional cure in hemophilia A, it has many limitations which need to be addressed. Therefore, pharmacotherapy is likely to remain the mainstay in the management of hemophilia A and promises to get better with currently available therapies. Evolving factor and non-factor replacement therapies may also improve current unmet needs in hemophilia A management.

Concomitant use of bypassing agents with emicizumab for people with haemophilia A and inhibitors undergoing surgery

INTRODUCTION

Surgery in people with haemophilia and factor VIII inhibitors is typically managed with perioperative administration of haemostatic agents to prevent or control the occurrence of bleeding events. Practical experience of surgery in patients with inhibitors who are receiving treatment with emicizumab is growing; however, the novelty of the situation means that standardised guidelines are lacking with regard to the concomitant administration of haemostatic agents, including dose and laboratory monitoring.

AIM

To review approaches to haemostatic management during major and minor invasive procedures in patients with haemophilia A and inhibitors, and to provide recommendations for controlling bleeding events.

METHODS

A search was conducted, limited to the past 4 years (January 2016-April 2020), pertaining to published evidence of surgery for patients receiving emicizumab. Publications identified from the search were manually reviewed to determine studies and case reports relevant for inclusion.

RESULTS

Identified literature and practical experience of the authors were used to build a consensus of practical recommendations for the concomitant administration of haemostatic agents during the perioperative period for elective surgery in patients with inhibitors who are receiving emicizumab.

CONCLUSIONS

The current evidence base indicates that surgery can be successfully performed in patients with inhibitors who are receiving emicizumab and that bypassing agents can be used concomitantly. Data from prospective studies are required to further support recommendations for haemostatic management of surgery in patients receiving emicizumab.

Management of children with hemophilia A: How emicizumab has changed the landscape

The key to having a good quality of life for an adult with hemophilia rests largely on how he or she was managed as children. With effective prophylaxis, young men can begin their adult life with excellent joint function and few, if any, other sequelae from their disease. Unfortunately, this outcome is not always (nor often) attained because of the limitations of the mainstay of treatment, which is factor replacement therapy. In resource-rich countries with an adequate supply of factor concentrates, the treatment burden and formation of inhibitors limit the potential for an ideal outcome, whereas in much of the world, factor concentrates are too expensive to even be an option. The novel agent, emicizumab, which has become available in numerous countries around the world, is reshaping how one approaches the treatment of children with hemophilia A. This Forum Article, based on a State-of-the-Art lecture given at the 2020 International Society on Thrombosis and Haemostasis Virtual Meeting, presents an approach including clinically applicable algorithms for treating children with hemophilia A in the new era with emicizumab.

Real-world cost estimates of initiating emicizumab in US patients with haemophilia A

INTRODUCTION

Emicizumab is the first approved non-factor therapy for haemophilia A. It provides superior prophylactic bleeding control compared to other products in both patients with and patients without inhibitors. However, there is no real-world data about the monetary consequences of starting emicizumab.

AIM

To examine the estimated costs of starting emicizumab in a cohort of real-world haemophilia A patients with and without inhibitors.

METHODS

The cost of haemostatic therapy for 6 months before and after initiating emicizumab for participants in a multicentre observational study was calculated based on the type of product and dosing that was used for prophylaxis and treating breakthrough bleeds, the number of treated bleeds and the participant weight.

RESULTS

Ninety-two patients were included, 18 with an active inhibitor. The median age was 8.7 years. The median total cost for all patients decreased from $176,720 to $128,099 (p = .04) after initiating emicizumab, largely because of decrease in the total cost of high-cost outliers. The cost of prophylaxis and the total cost of bleeds also significantly decreased after starting emicizumab, both for patient with and patients without inhibitors.

CONCLUSIONS

Starting or switching to prophylaxis with emicizumab results in decreased costs for the treatment of patients with haemophilia A. This real-world data could inform on payer decisions as well as future cost-effective analysis.

The effectiveness and value of emicizumab and valoctocogene roxaparvovec for the management of hemophilia A without inhibitors

DISCLOSURES: Funding for this summary was contributed by Arnold Ventures, California Health Care Foundation, The Donaghue Foundation, Harvard Pilgrim Health Care, and Kaiser Foundation Health Plan to the Institute for Clinical and Economic Review (ICER), an independent organization that evaluates the evidence on the value of health care interventions. ICER's annual policy summit is supported by dues from AbbVie, Aetna, America's Health Insurance Plans, Anthem, Alnylam, AstraZeneca, Biogen, Blue Shield of CA, Boehringer-Ingelheim, Cambia Health Services, CVS, Editas, Evolve Pharmacy, Express Scripts, Genentech/Roche, GlaxoSmithKline, Harvard Pilgrim, Health Care Service Corporation, HealthFirst, Health Partners, Humana, Johnson & Johnson (Janssen), Kaiser Permanente, LEO Pharma, Mallinckrodt, Merck, Novartis, National Pharmaceutical Council, Pfizer, Premera, Prime Therapeutics, Regeneron, Sanofi, Spark Therapeutics, uniQure, and United Healthcare. Agboola, Rind, Herron-Smith, and Pearson are employed by ICER. Walton and Quach, through the University of Illinois at Chicago, received funding from ICER for development of the economic model described in this report.

Real-world case series and summary of current literature of infants and toddlers with severe hemophilia A with inhibitor on prophylaxis with emicizumab

Emicizumab is a recombinant, humanized, and a bispecific monoclonal antibody that bridges activated factor (F) IX and FX in place of FVIII to restore hemostasis in persons with hemophilia A (PHA). Data on the efficacy and safety of emicizumab in young children is limited. Immunologic naivety, physiologically decreased production of vitamin K dependent proteins, specifically FIX, and enhanced clearance of emicizumab in infants may support decreased emicizumab effectiveness. We report on the facilitation of care rendered by using emicizumab in young PHA with inhibitors and extend data on the efficacy and safety in PHA < 3 years.

Emicizumab in tolerized patients with hemophilia A with inhibitors: A single-institution pediatric cohort assessing inhibitor status

Background

The majority of patients with hemophilia A with inhibitors who undergo immune tolerance induction (ITI) achieve successful tolerance and transition to factor VIII (FVIII) prophylaxis. A portion of these patients have switched to emicizumab for bleeding prevention. However, the risk of inhibitor relapse on emicizumab is unclear.

Objective

To evaluate the inhibitor status of patients with hemophilia A and inhibitors who achieved successful/partial tolerance after ITI and transitioned from FVIII prophylaxis to emicizumab.

Methods

This is a single-institution, retrospective review of pediatric patients with severe hemophilia A who have completed ITI with FVIII and switched to emicizumab.

Results/Conclusions

Seven successfully tolerized and five partially tolerized patients were identified. Three patients continued intermittent FVIII infusions on emicizumab at 50-70 IU/kg twice weekly, once weekly, or every other week due to concerns for inhibitor relapse or loss of recent FVIII tolerance by the treating provider. Eleven of 12 patients (92%) maintained negative inhibitor titers at a mean follow-up of 14.2 ± 6.1 months. One individual had an inhibitor relapse with a peak titer of 2.5 BU/mL. Five of the 11 patients (45%) with negative inhibitor titers had detectable nonneutralizing anti-FVIII IgG4 antibodies, but none of the patients had detectable IgG1 antibodies. There were no inhibitor recurrences in a subset of six patients after FVIII re-exposure for bleeding events or surgery. Given that the presence of an inhibitor significantly impacts factor product choice for bleeding management, ongoing inhibitor monitoring in tolerized patients with hemophilia A who transition to emicizumab is strongly recommended.

Management of patients with severe haemophilia a without inhibitors on prophylaxis with emicizumab: AICE recommendations with focus on emergency in collaboration with SIBioC, SIMEU, SIMEUP, SIPMeL and SISET

INTRODUCTION

The factor VIII (FVIII)-mimetic bispecific monoclonal antibody, emicizumab, previously approved for prophylaxis in haemophilia A with inhibitors, has been recently licensed in several countries also in patients with severe haemophilia A (PWSHA) without inhibitors. The introduction of this innovative agent requires the development of specific pathways at Haemophilia Treatment Centres (HTC), particularly regarding laboratory testing and treatment of breakthrough bleeds and invasive procedures/surgeries, even more critical when patients are managed by non-specialist professionals. Limited literature data and clinical experience in PWSHA without inhibitors on emicizumab are currently available.

AIM

To promote awareness and overcome these challenges, the Italian Association of Haemophilia Centres (AICE) issued a guidance on the management of PWSHA without inhibitors on emicizumab prophylaxis, focused on emergency and shared with other National Scientific Societies in the field.

METHODS

The document, drafted by an AICE expert panel and approved through online consultation, was further revised by a multidisciplinary working group, including members of 5 haemostasis, laboratory and emergency scientific societies. The final version was approved by the Council of each society.

RESULTS

General recommendations about use of FVIII concentrates for the treatment of bleeding or haemostatic coverage of invasive procedures/surgeries and laboratory monitoring in PWSHA without inhibitors on emicizumab are provided. Specific issues of the management in the emergency room are focused, highlighting the need for direct involvement or formalized supervision by specialist HTC physicians.

CONCLUSIONS

This guidance provides a reference pathway to be implemented in the different healthcare organizations, especially for the challenging emergency management in this setting.