The use of rituximab as an adjuvant for immune tolerance therapy in a hemophilia B boy with inhibitor and anaphylaxis to factor IX concentrate

Factor IX inhibitors in haemophilia B: A report of National Haemophilia Registry in China

INTRODUCTION

The development of inhibitors against factor FIX (FIX) is the most serious complication of FIX replacement therapy in haemophilia B (HB) patients. Currently, only few cohorts of HB inhibitor patients have been reported worldwide.

AIM

This Chinese nationwide study of HB inhibitor patients explored their risk factors for FIX inhibitor development and experience on their management.

METHODS

We retrospectively analysed patient characteristics, F9 genotypes, treatment strategies and outcomes of HB inhibitor patients registered to the Chinese National Registry and Patient Organization Registry.

RESULTS

Forty-four unique HB inhibitor patients were identified in 4485 unique HB patients registered by year 2021 to the two Registries. Inhibitor diagnosis were usually delayed and the low prevalence (.98%) may suggest some inhibitor patients were not identified. Their median age at inhibitor diagnosis was 7.5 (IQR, 3.0-14.8) years. Most patients (95.5%) had high-titre inhibitors. Allergic/Anaphylactic reactions occurred in 59.1% patients. Large deletions and nonsense mutations were the most common F9 mutation types in our FIX inhibitor patients. Patients with large F9 gene deletions were more likely to develop inhibitors (p = .0002), while those with missense mutations had a low risk (p < .0001). Thirteen (29.5%) patients received immune tolerance induction (ITI) therapy using low-dose prothrombin complex concentrate regimens. Twelve completed ITI with three (25.0%) achieving success. Nephrotic syndrome developed in two (16.7%) patients during ITI.

CONCLUSION

This study reports the largest Chinese cohort of HB inhibitor patients. Large deletions were most significantly associated with inhibitor development. Low-dose ITI might be feasible for FIX inhibitor eradication.

Real-world evidence on health resource use among patients with haemophilia and inhibitor exhibiting severe bleeding episodes

OBJECTIVE

This study aimed to explore real-world evidence on health resource use (HRU) spending on patients with haemophilia and inhibitor.

MATERIALS AND METHODS

Medical records from 1990 to 2019 of patients with haemophilia and inhibitor from three comprehensive haemophilia treatment centres were retrospectively retrieved.

RESULTS

In all, 31 patients with haemophilia (A = 30, B = 1) and inhibitor ≥5 BU were included. The mean initial inhibitor of 95.4 BU was detected at the mean age of 6.7 years. The mean number of annual hospitalisations was 3.9. A total of 795 bleeding episodes (major =125, minor =670) were evaluated. The treatment included bypassing agents or plasma exchange before administering high-dose factor VIII concentrate and intervention or surgery. Six patients succumbed to bleeding at the mean age of 17.2 years. Nineteen surviving patients experienced multiple morbidity except six patients with successful and partially successful immune tolerance induction (ITI). The mean (SD) annual total medical consumption for episodic treatment and successful ITI per patient with haemophilia A were 30,804 (81,332) USD and 55,531 (100,566) USD, respectively. Only episodic treatment was paid by the government budget for limited amounts of bypassing agents.

CONCLUSION

Management for patients with haemophilia and inhibitor exhibiting severe bleeding is challenging for medical personnel in countries having limited resources over decades. The real-world data will be used to negotiate with the government to increase budget for adequate bypassing agents or nonreplacement therapy and to include ITI in the national haemophilia treatment.

Allergy and inhibitors in hemophilia - a rare complication with potential novel solutions

INTRODUCTION

Hemophilia is a rare bleeding disorder caused by a deficiency of the plasma coagulation factors VIII and IX (hemophilia A [HA] and hemophilia B [HB], respectively). Replacement therapy with clotting factor concentrates is the mainstay of treatment. Unlike in patients with HB, anaphylaxis in patients with HA is extremely rare.

METHODS

A retrospective study of prospectively collected data on patients with hemophilia who experienced anaphylaxis was conducted in our center. Demographic and clinical data were collected, and laboratory workups that included thrombin generation were conducted.

RESULTS

Our first patient underwent successful immune tolerance induction (ITI) following the administration of rituximab. The second patient was transitioned to emicizumab. The third patient receives recombinant activated VIIa (rFVIIa) on demand. Thrombin generation was performed following current medical management protocols for supporting hemostasis.

DISCUSSION

Our case series illustrates the difficulty in managing patients with anaphylaxis to replacement therapy. In the era of novel therapies, such as emicizumab, the management of HA patients who experience anaphylaxis to replacement therapy is becoming easier and may obviate the need for ITI. Current treatment strategies for HB patients with such anaphylaxis, however, are limited to rFVIIa, and it continues to pose a challenge.

Successful second ITI with factor IX and combined immunosuppressive therapy. A patient with severe haemophilia B and recurrence of a factor IX inhibitor

Immune tolerance induction (ITI) in patients with haemophilia B and inhibitors may be complicated by anaphylactic reactions and nephrotic syndrome with lower success rates than in haemophilia A (25% vs. 50-90%). According to case reports, immunosuppressive therapy in addition to high doses of factor IX (FIX) appears to be promising. We report an 18-year-old patient with severe haemophilia B and a FIX inhibitor with a maximum titre of 2.6 Bethesda units and allergic skin reactions to FIX infusions. At 5 years of age, this patient already had a FIX inhibitor with allergic reactions to FIX and activated prothrombin complex concentrate. ITI at 11 years of age with high-dose FIX, dexamethasone, rituximab, mycophenolate mofetil and intravenous immunoglobulins had induced a sustained response until the current presentation. The patient was restarted on the same ITI regimen with aforementioned immunosuppressants, which were initiated one week before high-dose FIX. No allergic reactions, nephrotic syndrome or serious infection occurred during ITI. The FIX inhibitor was undetectable after five weeks of treatment and remained so until 19 months of follow-up.

Inhibitor eradication with rituximab in haemophilia: where do we stand?

Rituximab is a humanized chimeric anti-CD20 monoclonal antibody initially developed for the treatment of some haematological malignancies. Thanks to its ability to rapidly and specifically deplete B cells, it has also been used in a variety of autoimmune disorders, haematological or not. In this context, during the last decade several small case series have documented successful inhibitor eradication with rituximab, alone or in combination with other immunosuppressive agents, in patients with acquired haemophilia A refractory to standard therapy. In addition, a number of investigators have recently used this agent in patients with congenital haemophilia A or B and alloantibodies refractory to first-line treatment. This article critically reviews the current knowledge on the use of rituximab in acquired haemophilia or congenital haemophilia complicated by alloantibodies, also providing treatment algorithms for the management of these conditions.

Management of multiple drug allergies in children

Children with multiple drug allergies are likely to require treatment with one or more of the drugs to which they may have had a reaction, when there is no alternate effective drug available. Detailed review of their history and/or use of appropriate diagnostic studies will help determine the potential safety of readministering the desired drug as well as the method for its readministration, most likely in the form of a drug challenge or desensitization. A practical approach to the diagnosis and treatment of children with multiple drug allergies is described in this review.

Haemophilia B: current pharmacotherapy and future directions

INTRODUCTION

Hemophilia B is a rare hereditary hemorrhagic disorder characterized by deficiency of the clotting factor IX (FIX). Hemophilia B patients experience mild to severe bleeding complications according to the degree of FIX defect. Nowadays, the most challenging complication of individuals with hemophilia B is the development of alloantibodies, which render the standard replacement therapy with FIX concentrates ineffective, exposing them to a significantly increased morbidity and mortality.

AREAS COVERED

This review summarizes the most important events leading to the development of the current FIX products available for the treatment of hemophilia B patients. In addition, it focuses on the more recent advances in the production of new FIX molecules aimed at improving the clinical management of such patients.

EXPERT OPINION

Although the availability of plasma-derived FIX concentrates has greatly improved the clinical management of hemophilia B patients, the introduction of FIX products using recombinant DNA technology has represented the most significant therapeutic progress in hemophilia B therapy, ensuring an advanced level of safety. The development of rFIX products with extended half lives will further improve the therapeutic armamentarium for hemophilia B patients.

Immune tolerance induction in haemophilia: evidence and the way forward

Given the inhibitor-associated morbidity resulting from limited effective treatment options, antibody eradication is the ultimate goal of inhibitor management. The only clinically proven strategy for achieving antigen-specific tolerance to factor VIII is immune tolerance induction (ITI). First reported over 30 years ago, much of our current knowledge about ITI in haemophilia A and B was derived from small cohort studies and retrospective national and international ITI registries. More recently, prospective randomised ITI trials have been designed and initiated to answer outstanding questions related to the optimisation of current therapeutic strategy in haemophilia A. However, due to the low incidence of inhibitor development in haemophilia B compared to haemophilia A, there are few comparable data from which to develop a useful evidence-based approach to the prevention and eradication of FIX inhibitors. The lack of an effective strategy is particularly problematic given the even greater morbidity associated with the almost unique occurrence of allergic and anaphylactic reactions that often herald FIX antibody development, and further complicates attempts to eradicate FIX inhibitors. Ultimately, successful inhibitor prevention and eradication strategies for both diseases will emerge from the clinical translation of our evolving knowledge of immune stimulation and tolerance. This paper will discuss our current understanding of immune tolerance outcome and outcome predictors for haemophilia A and B; it will also review the current consensus recommendations for ITI, as well as the emerging scientific body of immunological knowledge that may significantly impact the therapeutic and preventative strategies of the future.