An update on the ‘danger theory’ in inhibitor development in hemophilia A

The spleen is the major site for the development and expansion of inhibitor producing-cells in hemophilia A mice upon FVIII infusion developing high-titer inhibitor

BACKGROUND

Hemophilia A (HA) is a hereditary bleeding disorder caused by defects in endogenous factor (F)VIII. Approximately 30 % of patients with severe HA treated with FVIII develop neutralizing antibodies (inhibitors) against FVIII, which render the therapy ineffective. The managements of HA patients with high-titter inhibitors are especially challenging. Therefore, it is important to understand the mechanism(s) of high-titer inhibitor development and dynamics of FVIII-specific plasma cells (FVIII-PCs).

AIMS

To identify the dynamics of FVIII-PCs and the lymphoid organs in which FVIII-PCs are localized during high-titer inhibitor formation.

METHODS AND RESULTS

When FVIII-KO mice were intravenously injected with recombinant (r)FVIII in combination with lipopolysaccharide (LPS), a marked enhancement of anti-FVIII antibody induction was observed with increasing FVIII-PCs, especially in the spleen. When splenectomized or congenitally asplenic FVIII-KO mice were treated with LPS + rFVIII, the serum inhibitor levels decreased by approximately 80 %. Furthermore, when splenocytes or bone marrow (BM) cells from inhibitor+ FVIII-KO mice treated with LPS + rFVIII were grafted into immune-deficient mice, anti-FVIII IgG was detected only in the serum of splenocyte-administered mice and FVIII-PCs were detected in the spleen but not in the BM. In addition, when splenocytes from inhibitor+ FVIII-KO mice were grafted into splenectomized immuno-deficient mice, inhibitor levels were significantly reduced in the serum.

CONCLUSION

The spleen is the major site responsible for the expansion and retention of FVIII-PCs in the presence of high-titer inhibitors.

Immunogenicity of Therapeutic Biological Modalities - Lessons from Hemophilia A Therapies

The introduction and development of biologics such as therapeutic proteins, gene-, and cell-based therapy have revolutionized the scope of treatment for many diseases. However, a significant portion of the patients develop unwanted immune reactions against these novel biological modalities, referred to as immunogenicity, and no longer benefit from the treatments. In the current review, using Hemophilia A (HA) therapy as an example, we will discuss the immunogenicity issue of multiple biological modalities. Currently, the number of therapeutic modalities that are approved or recently explored to treat HA, a hereditary bleeding disorder, is increasing rapidly. These include, but are not limited to, recombinant factor VIII proteins, PEGylated FVIII, FVIII Fc fusion protein, bispecific monoclonal antibodies, gene replacement therapy, gene editing therapy, and cell-based therapy. They offer the patients a broader range of more advanced and effective treatment options, yet immunogenicity remains the most critical complication in the management of this disorder. Recent advances in strategies to manage and mitigate immunogenicity will also be reviewed.

FVIII inhibitor surveillance in children with hemophilia A in Indonesia: a report from the Indonesian Pediatric Hematology-Oncology Working Group

Background

Factor VIII (FVIII) inhibitor diagnosis and surveillance in Indonesia are challenging owing to geographic conditions and the lack of laboratory facilities nationwide for inhibitor assays. This study aimed to determine the prevalence of FVIII inhibitors in children diagnosed with hemophilia A (HA) in Indonesia.

Methods

A cross-sectional study was conducted in 12 hospitals in eight provinces of Indonesia between 2020 and 2021. Factor VIII inhibitor screening was performed in a central hemostasis laboratory for all children with HA (≤18 yr) who had received a minimum of 10 exposure days to clotting factor concentrates. The FVIII inhibitor titer was determined using the Bethesda assay.

Results

Children (388) were enrolled in this study, including 219 (56.4%), 131 (33.8%), and 38 (9.4%) with severe, moderate, and mild HA, respectively. The prevalence of children who developed FVIII inhibitors was 37 out of 388 (9.6%). Factor VIII inhibitors were found in 25/219 (11.4%) severe, 11/131 (8.3%) moderate, and 1/38 (2.6%) children with mild HA. Thirteen children had low-titer inhibitors and 24 had high-titer inhibitors, with a median of 9.44 (1.48‒412.0) Bethesda Units. Among 13 children with low-titer inhibitors, eight underwent a confirmation test, of which five tested negative and were classified as transient. A significant difference in annual joint bleeding rate was found between patients with low and high inhibitor titers and those without inhibitors (P＜0.001).

Conclusion

Factor VIII inhibitor prevalence in Indonesia was relatively low. However, the risk factors that may contribute to FVIII inhibitor development among Indonesian patients require further study.

Hemophilia a patients with inhibitors: Mechanistic insights and novel therapeutic implications

The development of coagulation factor VIII (FVIII) inhibitory antibodies is a serious complication in hemophilia A (HA) patients after FVIII replacement therapy. Inhibitors render regular prophylaxis ineffective and increase the risk of morbidity and mortality. Immune tolerance induction (ITI) regimens have become the only clinically proven therapy for eradicating these inhibitors. However, this is a lengthy and costly strategy. For HA patients with high titer inhibitors, bypassing or new hemostatic agents must be used in clinical prophylaxis due to the ineffective ITI regimens. Since multiple genetic and environmental factors are involved in the pathogenesis of inhibitor generation, understanding the mechanisms by which inhibitors develop could help identify critical targets that can be exploited to prevent or eradicate inhibitors. In this review, we provide a comprehensive overview of the recent advances related to mechanistic insights into anti-FVIII antibody development and discuss novel therapeutic approaches for HA patients with inhibitors.

Risk factors for inhibitors in hemophilia A based on RNA-seq and DNA methylation

Background

The development of factor VIII (FVIII) inhibitor is a severe complication during replacement therapy for hemophilia A patients.

Objectives

We investigated the potential risk factors for FVIII inhibitor formation based on genome-wide RNA-sequencing and whole-genome bisulfite sequencing analysis.

Methods

RNA-sequencing and whole-genome bisulfite sequencing analysis were applied on 17 blood samples with F8 intron 22 inversion, including seven with inhibitors and 10 without.

Results

Altogether, 344 mRNA transcripts and 20 long noncoding RNAs (lncRNA) transcripts were differentially expressed. Among the differentially expressed transcripts, 200 mRNAs and 12 lncRNAs were upregulated, and 144 mRNAs and eight lncRNAs were downregulated. Gene ontology enrichment analysis of differentially expressed mRNAs showed that genes involved in immune stimulation, especially those for T-cell activation, were upregulated, whereas genes involved in negative immune response regulation were downregulated. Coexpression analysis revealed that the targeted upregulated genes of differentially expressed lncRNA were similarly closely related to immune activation, especially T-cell activation. Methylation analysis showed inhibitor patients exhibited a slightly lower methylation status in the CpG islands, 5' untranslated region, and exon regions (p < 0.01). Genes with differentially methylated regions were also related to T-cell activation.

Conclusions

There is an upregulation of genes involved in activation of the immune system in hemophilia A patients with inhibitors. The lncRNA and methylation modifications may play important roles in inhibitor production. These findings are potentially to reveal novel therapeutic targets for prevention and treatment of inhibitors.

Hemophilia A Gene Therapy: Current and Next-Generation Approaches

INTRODUCTION

: Hemophilia comprises a group of X-linked hemorrhagic disorders that result from a deficiency of coagulation factors. The disorder affects mainly males and leads to chronic pain, joint deformity, reduced mobility, and increased mortality. Current therapies require frequent administration of replacement clotting factors, but the emergence of alloantibodies (inhibitors) diminishes their efficacy. New therapies are being developed to produce the deficient clotting factors and prevent the emergence of inhibitors.

AREAS COVERED

: This article provides an update on the characteristics and disease pathophysiology of hemophilia A, as well as current treatments, with a special focus on ongoing clinical trials related to gene replacement therapies.

EXPERT OPINION

: Gene replacement therapies provide safe, durable, and stable transgene expression while avoiding the challenges of clotting factor replacement therapies in patients with hemophilia. Improving the specificity of the viral construct and decreasing the therapeutic dose are critical toward minimizing cellular stress, induction of the unfolded protein response, and the resulting loss of protein production in liver cells. Next-generation gene therapies incorporating chimeric DNA sequences in the transgene can increase clotting factor synthesis and secretion, and advance the efficacy, safety, and durability of gene replacement therapy for hemophilia A as well as other blood clotting disorders.

Efficacy, safety, and immunogenicity of rurioctocog alfa pegol for prophylactic treatment in previously treated patients with severe hemophilia A: a systematic review and meta-analysis of clinical trials

Background: Patients with severe hemophilia often present with painful joint and soft tissue bleeding which may restrict them from their daily activities. The current standard of care still relies on a regular prophylactic factor VIII (FVIII), which has a high daily treatment burden. Recently, rurioctocog alfa pegol, a third-generation recombinant FVIII with a modification in its polyethylene glycol (PEG) component, has been developed. Several trials have studied this synthetic drug as bleeding prophylaxis in severe hemophilia A. This study aims to evaluate the efficacy, safety, and immunogenicity of rurioctocog alfa pegol for previously treated patients with severe hemophilia A. Methods: This study was conducted in conformity with the PRISMA guidelines. Data were retrieved from PubMed, Scopus, Cochrane Library, Wiley Online Library, and CINAHL (via EBSCOhost). Study qualities were assessed using the Methodological Index for Non-Randomized Studies (MINORS) and Modified Jadad scales. Results: Four studies involving 517 previously treated severe hemophilia A patients were included in this study. The pooled mean of total annualized bleeding rate (ABR) and hemostatic efficacy was 2.59 (95% CI = 2.04-3.14) and 92% (95% CI = 85%-97%), respectively. Only 30 (2.3%) non-serious and one (1.4%) serious adverse events were considered related to rurioctocog alfa pegol treatment. At the end of the studies, no development of FVIII inhibitory antibodies was observed. None of the developed binding antibodies to FVIII, PEG-FVIII, or PEG was correlated to the treatment efficacy and safety. Conclusions: Despite the limited availability of direct comparison studies, our analyses indicate that rurioctocog alfa pegol could serve as a safe and effective alternative for bleeding prophylaxis in previously treated hemophilia A patients. Moreover, it appears to have low immunogenicity, which further increases the safety profile of the drug in such clinical conditions.

Efficacy, safety, and immunogenicity of rurioctocog alfa pegol for prophylactic treatment in previously treated patients with severe hemophilia A: a systematic review and meta-analysis of clinical trials

Background: Patients with severe hemophilia often present with painful joint and soft tissue bleeding which may restrict them from their daily activities. The current standard of care still relies on a regular prophylactic factor VIII (FVIII), which has a high daily treatment burden. Recently, rurioctocog alfa pegol, a third-generation recombinant FVIII with a modification in its polyethylene glycol (PEG) component, has been developed. Several trials have studied this synthetic drug as bleeding prophylaxis in severe hemophilia A. This study aims to evaluate the efficacy, safety, and immunogenicity of rurioctocog alfa pegol for previously treated patients with severe hemophilia A. Methods: This study was conducted in conformity with the PRISMA guidelines. Data were retrieved from PubMed, Scopus, Cochrane Library, Wiley Online Library, and CINAHL (via EBSCOhost). Study qualities were assessed using the Methodological Index for Non-Randomized Studies (MINORS) and Modified Jadad scales. Results: Four studies involving 517 previously treated severe hemophilia A patients were included in this study. The pooled mean of total annualized bleeding rate (ABR) and hemostatic efficacy was 2.59 (95% CI = 2.04-3.14) and 92% (95% CI = 85%-97%), respectively. Only 30 (2.3%) non-serious and one (1.4%) serious adverse events were considered related to rurioctocog alfa pegol treatment. At the end of the studies, no development of FVIII inhibitory antibodies was observed. None of the developed binding antibodies to FVIII, PEG-FVIII, or PEG was correlated to the treatment efficacy and safety. Conclusions: Despite the limited availability of direct comparison studies, our analyses indicate that rurioctocog alfa pegol could serve as a safe and effective alternative for bleeding prophylaxis in previously treated hemophilia A patients. Moreover, it appears to have low immunogenicity, which further increases the safety profile of the drug in such clinical conditions.

Efficacy safety and immunogenicity of rurioctocog alfa pegol for prophylactic treatment in previously treated patients with severe hemophilia A: a systematic review and meta-analysis of clinical trials

Background: Patients with severe hemophilia often present with painful joint and soft tissue bleeding which may restrict them from their daily activities. The current standard of care still relies on a regular prophylactic factor VIII (FVIII), which has a high daily treatment burden. Recently, rurioctocog alfa pegol, a third-generation recombinant FVIII with a modification in its polyethylene glycol (PEG) component, has been developed. Several trials have studied this synthetic drug as bleeding prophylaxis in severe hemophilia A. This study aims to evaluate the efficacy, safety, and immunogenicity of rurioctocog alfa pegol for previously treated patients with severe hemophilia A. Methods: This study was conducted in conformity with the PRISMA guidelines. Data were retrieved from PubMed, Scopus, Cochrane Library, Wiley Online Library, and CINAHL (via EBSCOhost). Study qualities were assessed using the Methodological Index for Non-Randomized Studies (MINORS) and Modified Jadad scales. Results: Four studies involving 517 previously treated severe hemophilia A patients were included in this study. The pooled mean of total annualized bleeding rate (ABR) and hemostatic efficacy was 2.59 (95% CI = 2.04-3.14) and 92% (95% CI = 85%-97%), respectively. Only 30 (2.3%) non-serious and one (1.4%) serious adverse events were considered related to rurioctocog alfa pegol treatment. At the end of the studies, no development of FVIII inhibitory antibodies was observed. None of the developed binding antibodies to FVIII, PEG-FVIII, or PEG was correlated to the treatment efficacy and safety. Conclusions: Despite the limited availability of direct comparison studies, our analyses indicate that rurioctocog alfa pegol could serve as a safe and effective alternative for bleeding prophylaxis in previously treated hemophilia A patients. Moreover, it appears to have low immunogenicity, which further increases the safety profile of the drug in such clinical conditions.

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.

Implanted subcutaneous versus intraperitoneal bioscaffold seeded with hepatocyte-like cells: functional evaluation

Background and objectives

The X-linked bleeding disorder, hemophilia A, is caused by defective production of factor VIII (FVIII). Hemophilic patients require regular FVIII infusions. Recombinant factor replacement poses the safest line of therapy. However, its main drawbacks are high expenses and the higher liability for formation of inhibitors. Recent studies confirmed the ability of bone marrow-derived stem cells to secrete FVIII. This study aims to generate bioscaffold from decellularized liver and subsequently seed it with trans-differentiated human stem cells into hepatic-like cells. This scaffold can then be implanted intraperitoneally or subcutaneously to provide FVIII.

Methods

After generation of the bioscaffold, seeding of discoid scaffolds with trans-differentiated human hepatocyte-like cells was performed. Then, the generated organoid was implanted into peritoneal cavity or subcutaneous tissue of experimental rats.

Results

Serum human FVIII was significantly increased in rats subjected to subcutaneous implantation compared intraperitoneal implantation. Immunostaining for detecting Cytokeratin 19 and human anti-globulin confirmed the presence of mature human hepatocytes that were significantly increased in subcutaneous implanted scaffold compared to the intraperitoneal one.

Conclusion

Implantation of decellularized bioscaffold seeded with trans-differentiated stem cells in rats was successful to establish production of FVIII. Subcutaneous implantation showed higher FVIII levels than intraperitoneal implantation.

A previously treated severe haemophilia A patient developed high-titre inhibitor after vaccinations

The factor VIII (FVIII)-neutralizing antibody (inhibitor) seen in 25%–30% of patients with severe haemophilia A (SHA). Vaccination is a non-genetic risk factor of inhibitor development as ‘danger signal’ which may provide a pro-inflammatory microenvironment to increase FVIII immunogenicity. We reported a previously treated SHA patient postponed the first vaccination to 15-month age received diphtheria-pertussis-tetanus intramuscularly. At 18-month age, the patient received Hepatitis A intramuscularly and Varicella Zoster Virus subcutaneously with 2 weeks interval and FVIII infusion was given <24 h prior for each. Successive bleedings occurred 1 week later with inefficacy of FVIII replacement. High-titre inhibitor was tested at 117 exposure days. This case suggested that continuous vaccinations in close proximity to FVIII could induce inhibitor. The relationship between vaccination and FVIII immunogenicity still needs to be revealed by further study.

Incidence of inhibitor development in PUPs with severe Haemophilia A in the CEE region between 2005 and 2015

INTRODUCTION

This study analyses real-world data on 144 previously untreated patients (PUPs) with severe Haemophilia A, from seven countries in Central and Eastern Europe (CEE: Bulgaria, Croatia, Czech Republic, Hungary, Latvia, Serbia, and Slovenia), over a period of 11 years. It analyses the risk factors associated with development of inhibitors to factor VIII concentrates.

METHODS

Cox proportional hazard models were used to estimate the hazard risk of factors possibly influencing the development of inhibitors. Patients were followed for up to 100 exposure days (EDs).

RESULTS

Cumulative inhibitor incidence at the time of 100 EDs was 18.7%, slightly lower than the 25-35% incidence reported in most studies. Of PUPs who developed inhibitors, a majority (56%) developed them within the first 20 EDs and 88% by the 50th ED. FVIII class (recombinant or plasma-derived) did not influence the inhibitors' incidence rate (p = 0.64). We found a significant protective effect of prophylaxis compared to on-demand treatment (p = 0.003). PUPs who had an intensive peak treatment during the first 50 EDs were at significantly higher risk for inhibitor development (HR (95% CI) 5.3 (2.3-12.5), p < 0.001).

CONCLUSION

Inhibitors are and will continue to be the most significant complication of haemophilia treatment with factor concentrates. This is particularly true for haemophilia A. In our cohort, we were able to show that the treatment regimen used during first 50EDs influenced significantly the inhibitor risk, but the class of the factor concentrate did not play an important role. Real world data will remain one of the important resources for improving our knowledge of haemophilia.