The prevalence and risk factors of inhibitor development of FVIII in previously treated patients with hemophilia A

Incidence and treatment-related risk factors of inhibitor development after intensive FVIII replacement for major orthopaedic surgery in previous treated haemophilia A

INTRODUCTION

Haemophilia A (HA) is an X-linked recessive bleeding disorder caused by lack or deficiency of coagulation factor VIII.

AIM

The aim of this study is to determine the incidence and treatment-related risk factors of inhibitor development after intensive FVIII replacement for major orthopaedic surgery in previous treated persons with HA.

METHODS

A total of 151 HA who underwent 221 major orthopaedic surgical procedures after intensive FVIII treatment were reviewed. The results of inhibitor tests were collected. Potential clinical risk factors for inhibitor development were analyzed.

RESULTS

111 people were diagnosed with severe HA. Thirty-seven persons (24.5%) had history of previous intensive FVIII treatment for surgical procedure. They received a mean perioperative cumulative FVIII of 498 iu/kg within first week after surgery. Seven cases (4.6%) developed an inhibitor post-operatively in our study. Surgical procedure for pseudotumor and the group of persons who experienced postoperative complications had the higher incidence of inhibitor development (9.5%, 13.3% respectively). Only previous history for intensive FVIII exposure was considered as a significant predictor for postoperative inhibitor development after multivariate logistic regression analysis (OR: 29.5, P = 0.002).

CONCLUSION

The incidence of inhibitor development in previously treated persons with HA undergoing major orthopaedic surgery was 4.6% and the history of previous intensive FVIII treatment for surgery was associated with higher risk of inhibitor development.

Comprehensive domain-specific analysis and immunoglobulin G profiling of anti-factor VIII antibodies using a bead-based multiplex immunoassay

BACKGROUND

Antibodies against factor (F)VIII are a major complication in the treatment of patients with severe hemophilia A. The Nijmegen-Bethesda assay (NBA) is the gold standard for detection of neutralizing antibodies (inhibitors), whereas both inhibitors and nonneutralizing antibodies can be detected by immunoassays such as enzyme-linked immunosorbent assay (ELISA) and multiplex bead-based assays.

OBJECTIVES

Evaluation of an in-house Luminex bead-based assay (LumiTope) compared with a commercially available ELISA and NBA.

METHODS

The LumiTope method comprised full-length and B-domain-deleted FVIII as well as 9 purified FVIII single or multidomains. The respective proteins were coupled to magnetic beads to detect domain-specific immunoglobulin (IgG; IgG1-4) anti-FVIII antibodies in a large cohort of patients with hemophilia A with and without inhibitors.

RESULTS

Overall, LumiTope assay had a high sensitivity (94.9%) and specificity (91.2%), particularly in patients with low-titer inhibitors compared with ELISA (sensitivity of 72.2% vs 27.7%). IgG4 was the most abundant IgG subclass in NBA-positive patients. NBA-positive and -negative patients showed different domain profiles. Patients with genetic variants in the heavy chain predominantly exhibited antibodies specific to this chain, while those with a light-chain variant showed a more diverse distribution of antibody specificities. Patients with an intron 22 inversion resembled those with a light-chain defect, with a majority of antibodies targeting the light chain.

CONCLUSION

LumiTope assay provides a sensitive and specific method for not only detection but also domain specification of anti-FVIII-antibodies. Implementation of bead-based assays could improve antibody detection, profiling, and comparability of results and complement NBA.

Association between interleukin-2 (rs2069762) gene polymorphism and FVIII inhibitor development in Indonesian patients with severe hemophilia A

BACKGROUND Factor VIII (FVIII) inhibitors in hemophilia A (HA) patients render FVIII replacement therapy ineffective. Although its development cause is unclear, it has been classified into therapeutic and genetic-related etiologies. Single nucleotide polymorphisms (SNPs) in several cytokine genes, including interleukin (IL)-2, could increase the risk of FVIII inhibitor development. This study aimed to evaluate the association between IL-2 (rs2069762) gene SNP and FVIII inhibitor development in Indonesian patients with severe HA. METHODS The IL-2 (rs2069762) gene SNP was examined in 119 HA patients. The presence of FVIII inhibitors was quantified using an enzyme-linked immunosorbent assay, with a titer of <0.28 ng/ml considered negative. Patients were divided into two groups: 59 with FVIII inhibitors (positive group) and 60 without inhibitors (negative group). The genotype of the subjects was determined using peripheral blood mononuclear cells and tetra-primer amplification refractory mutation system-polymerase chain reaction. RESULTS There was no association between IL-2 (rs2069762) gene polymorphism and FVIII inhibitor development on genotypes (p = 0.138) and allele frequencies (p = 0.780). CONCLUSIONS IL-2 (rs2069762) gene polymorphism is not a risk factor in the development of FVIII inhibitors in Indonesian patients with severe HA. Thus, further polymorphism studies in other cytokine genes are required to gain a comprehensive understanding of the FVIII inhibitor development.

Cost-utility analysis of emicizumab for the treatment of severe hemophilia A patients in Canada

INTRODUCTION

EHL FVIII products and emicizumab provide clinicians with other prophylactic options for treating hemophilia A, however, it is unclear if emicizumab is a cost-saving option. The objective of this study is to estimate the health and economic effects of using prophylactic EHL FVIII, SHL FVIII, and emicizumab in severe haemophilia A patients.

MATERIALS AND METHODS

A state-transition Markov model evaluated the cost-effectiveness of prophylactic SHL FVIII, EHL FVIII, and emicizumab in a cohort of 2-year-old male patients over a lifetime horizon in the form of a cost-utility analysis using a Canadian provincial ministry of health payer perspective. The transition probabilities, costs, and utilities were obtained from literature and the Canadian Bleeding Disorders Registry. Probabilistic sensitivity and scenario analyses were performed to test the robustness of the model.

RESULTS

The base-case analysis, over a lifetime horizon, resulted in a total cost and utilities per person for SHL FVIII, EHL FVIII, and emicizumab of $27.2 million (M), $36.7 M, and $26.2 M, respectively, and 31.30, 31.16, and 31.61 quality-adjusted life years, respectively. Emicizumab treatment resulted in 29 and 16 less bleeds in a lifetime compared to SHL FVIII and EHL FVIII, respectively. Probabilistic sensitivity analysis showed that emicizumab was cost-saving 100% of the time compared to SHL FVIII and EHL FVIII.

CONCLUSION

The cost-utility analysis showed that emicizumab is more effective and may be less costly than FVIII for Canadian haemophilia A patients, conditional on drug cost assumptions. Our model indicates that emicizumab may be a potentially favourable treatment option for minimising healthcare costs and providing higher effectiveness.

Breakthrough bleeding episodes in pediatric severe hemophilia a patients with and without inhibitors receiving emicizumab prophylaxis: a single-center retrospective review

Emicizumab has been widely used for prophylaxis in patients with hemophilia A (HA) of all ages, with or without factor VIII inhibitors. Data on emicizumab efficacy are certainly significant; however, protection against bleeding is not absolute, and the breakthrough bleeding risk can be approximately equivalent to that of patients with mild HA. This single-center retrospective review aimed to present the rate and management of breakthrough bleeding events in pediatric HA patients with and without inhibitors who are on emicizumab prophylaxis. Fifty-one pediatric patients on emicizumab prophylaxis that were followed up at Birmingham Children's Hospital between March 1, 2018, and May 15, 2021, were included in the current study. Our results showed that 56.8% (29/51) experienced no bleeding events, and 80.3% (41/51) had no major treated bleeds during the follow-up period. A total of 29.4% (15/51) had minor bleeds that resolved spontaneously or with antifibrinolytics. Overall, 19.6% (10/51) of the patients received additional FVIII to prevent or treat breakthrough bleeding. One patient had a major bleeding event in the form of hematuria. However, it resolved without treatment. Both major and minor bleeding episodes occurred in 7.8% (4/51) of patients. None of the patients with inhibitors (5/51) developed breakthrough bleeding. Only a few, mostly minor, breakthrough bleeding episodes were reported in our cohort. The balance between bleeding control and the risk of inhibitor development after episodic factor administration should be considered. Therefore, careful decisions should be made in managing bleeding events.Supplemental data for this article is available online at.

F8 gene mutation spectrum in severe hemophilia A with inhibitors: A large cohort data analysis from a single center in China

Introduction

Type of F8 gene mutation is the most important risk factor for inhibitor development in people with severe hemophilia A. However, there are few large cohort studies on the F8 mutation spectrum of people with severe hemophilia A with inhibitors.

Objective

This was the first large cohort study in children with severe hemophilia A with inhibitors from China that aimed to analyze the association between F8 variant types and inhibitor status.

Methods

The single‐center retrospective cohort study was conducted on children with severe hemophilia A with inhibitors admitted from January 2015 to December 2021. The clinical data were collected, and F8 genetic tests were performed.

Results

Among the 203 patients investigated, a mutation in F8 was identified in 196 cases. Most patients had deleterious mutations (153; 75.4%), including 82 cases of intron 22 inversions (40.4%); 40 cases of nonsense mutations (19.7%), with 15 cases in the light chain and 25 cases in the heavy chain; and 31 cases of large deletions or insertions (15.3%), with 29 cases involving more than one exon and 2 cases involving one exon. The large deletions or insertions encompassing multiple exons and nonsense mutations residing in the light chain were associated with not only the progression to a high‐titer inhibitor (P < .05) but also higher peak inhibitor titer (P < .05).

Conclusion

The F8 gene deleterious mutations, including intron 22 inversions, nonsense mutations, and large deletions or insertions, constitute the main mutation types in people with severe hemophilia A with inhibitors in China, with the latter mutation types (large deletions or insertions in multiple exons, and nonsense mutations in the light chain) signifying for a higher peak titer of inhibitor.

New Inhibitors in the Ageing Population: A Retrospective, Observational, Cohort Study of New Inhibitors in Older People with Hemophilia

INTRODUCTION

 A second peak of inhibitors has been reported in patients with severe hemophilia A (HA) aged >50 years in the United Kingdom. The reason for this suggested breakdown of tolerance in the aging population is unclear, as is the potential impact of regular exposure to the deficient factor by prophylaxis at higher age. No data on hemophilia B (HB) have ever been reported.

AIM

 The ADVANCE Working Group investigated the incidence of late-onset inhibitors and the use of prophylaxis in patients with HA and HB aged ≥40 years.

METHODS

 A retrospective, observational, cohort, survey-based study of all patients aged ≥40 years with HA or HB treated at an ADVANCE hemophilia treatment center.

RESULTS

 Information on 3,095 people aged ≥40 years with HA or HB was collected. Of the 2,562 patients with severe HA, the majority (73% across all age groups) received prophylaxis. In patients with severe HA, the inhibitor incidence per 1,000 treatment years was 2.37 (age 40-49), 1.25 (age 50-59), and 1.45 (age 60 + ). Overall, the inhibitor incidence was greatest in those with moderate HA (5.77 [age 40-49], 6.59 [age 50-59], and 4.69 [age 60 + ]) and the majority of inhibitor cases were preceded by a potential immune system challenge. No inhibitors in patients with HB were reported.

CONCLUSION

 Our data do not identify a second peak of inhibitor development in older patients with hemophilia. Prophylaxis may be beneficial in older patients with severe, and possibly moderate HA, to retain a tolerant state at a higher age.