Inhibitors in Severe Hemophilia A: 25-Year Experience in Slovakia

Determinants of successful immune tolerance induction in hemophilia A: systematic review and meta-analysis

Background

Immune tolerance induction (ITI) aims to eradicate anti-factor VIII (FVIII) antibodies (inhibitors) in persons with hemophilia A. However, this burdensome treatment fails in 10% to 40%. To estimate the chance of ITI success in clinical decision making, it is important to identify the predictors of ITI success.

Objectives

We performed a systematic review and meta-analysis to summarize the current evidence on determinants of ITI outcome in persons with hemophilia A.

Methods

A literature search was conducted to identify randomized controlled trials, cohort, or case-control studies reporting on the predictors for ITI outcome in persons with hemophilia A. The main outcome was ITI success. Methodological quality was assessed using an adapted Joanna Briggs Institute checklist, rating as high if ≥11 of 13 criteria were met. Pooled odds ratios (ORs) for ITI success were calculated for each determinant. ITI success was defined as negative inhibitor titer (<0.6 BU/mL), FVIII recovery ≥66% of expected, and FVIII half-life ≥6 hours in 16 (59.3%) studies.

Results

We included 27 studies, involving 1,734 participants. Methodological quality of 6 (22.2%) studies (418 participants) was rated as high. Twenty different determinants were assessed. Historical peak titer ≤100 BU/mL (compared with >100 BU/mL, OR, 1.7; 95% CI, 1.4-2.1), pre-ITI titer ≤10 BU/mL (compared with >10 BU/mL, OR, 1.8; 95% CI, 1.4-2.3), and peak titer during ITI ≤100 BU/mL (compared with >100 BU/mL, OR, 2.7; 95% CI, 1.9-3.8) were associated with a higher chance of ITI success.

Conclusion

Our results suggest that determinants related to the inhibitor titer are associated with ITI success.

Clinical Care of Bone Health in Patients on the Immune Tolerance Induction's Protocols With an Immunosuppressive Agent for Inhibitor Eradication in Hemophilia

Nowadays, the development of factor VIII and IX inhibitors in patients with hemophilia is considered as the most challenging in the treatment of hemophilia. Immune tolerance induction (ITI) therapy is an approach for eradication of inhibitors. Some ITI protocols are routinely in use for the eradication of inhibitors in patients with hemophilia. Moreover, such a therapeutic regimen may facilitate the tendency to reduced bone density in patients with inhibitor. This study scheduled to investigate whether that predisposing role of ITI protocols with an immunosuppressive agent has considered or not. By a literature review, published ITI protocols in hemophilia with inhibitors were evaluated. Among them, 51 papers found and studied thoroughly. None of them had performed the bone mineral examination in patients with hemophilia and inhibitor under treatment. Since there are 2 coexisting facilitating factors in these protocols, considering the bone mineral density study for patients with inhibitor who are undergoing ITI protocols with an immunosuppressive agent is recommended.

Epidemiological Challenges in Rare Bleeding Disorders: FVIII Inhibitor Incidence in Haemophilia A Patients-A Known Issue of Unknown Origin

There is a broad range of factor products approved in Germany for haemophilia A treatment. Since the introduction of recombinant coagulation factor VIII (FVIII) products in the 1990s, there has been substantial debate whether there is a difference in inhibitor incidence between single FVIII products or product classes. Neither haemophilia registries nor clinical studies, including a randomised controlled clinical trial, provided a consistent and definite answer. The reasons were mainly related to methodological challenges in conducting controlled studies in a rare disease. In this analysis, the most relevant epidemiological challenges and main problems were examined, including study bias, potential overlap of individual studies and advanced development of therapy and methods in the course of time. Meta-analyses on two levels showed that therapies using recombinant products resulted in different event rates when compared to plasma-derived products. These results are accompanied by substantial study heterogeneity evidenced by Cochran's Q tests. Only three studies have been identified that meet the standards of current clinical guidance. To finally resolve this ongoing and disputable safety issue of replacement therapy, collaboration among registry owners, academia and regulators must be fostered.

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.

Quantitative HLA-class-II/factor VIII (FVIII) peptidomic variation in dendritic cells correlates with the immunogenic potential of therapeutic FVIII proteins in hemophilia A

BACKGROUND

Plasma-derived (pd) or recombinant (r) therapeutic factor VIII proteins (FVIIIs) are infused to arrest/prevent bleeding in patients with hemophilia A (PWHA). However, FVIIIs are neutralized if anti-FVIII-antibodies (inhibitors) develop. Accumulating evidence suggests that pdFVIIIs with von Willebrand factor (VWF) are less immunogenic than rFVIIIs and that distinct rFVIIIs are differentially immunogenic. Since inhibitor development is T-helper-cell-dependent, human leukocyte antigen (HLA)-class-II (HLAcII) molecules constitute an important early determinant.

OBJECTIVES

Use dendritic cell (DC)-protein processing/presentation assays with mass-spectrometric and peptide-proteomic analyses to quantify the DP-bound, DQ-bound, and DR-bound FVIII-derived peptides in individual HLAcII repertoires and compare the immunogenic potential of six distinct FVIIIs based on their measured peptide counts.

PATIENTS/METHODS

Monocyte-derived DCs from normal donors and/or PWHA were cultured with either: Mix-rFVIII, a VWF-free equimolar mixture of a full-length (FL)-rFVIII [Advate® (Takeda)] and four distinct B-domain-deleted (BDD)-rFVIIIs [Xyntha® (Pfizer), NovoEight® (Novo-Nordisk), Nuwiq® (Octapharma), and Afstyla® (CSL Behring GmBH)]; a pdFVIII + pdVWF [Beriate® (CSL Behring GmBH)]; Advate ± pdVWF; Afstyla ± pdVWF; and Xyntha + pdVWF.

RESULTS

We showed that (i) Beriate had a significantly lower immunogenic potential than Advate ± pdVWF, Afstyla - pdVWF, and Mix-rFVIII; (ii) distinct FVIIIs differed significantly in their immunogenic potential in that, in addition to (i), Afstyla + pdVWF had a significantly lower immunogenic potential than Beriate, while the immunogenic potential of Beriate was not significantly different from that of Xyntha + pdVWF; and (iii) rFVIIIs with pdVWF had significantly lower immunogenic potentials than the same rFVIIIs without pdVWF.

CONCLUSIONS

Our results provide HLAcII peptidomic level explanations for several important clinical observations/issues including the differential immunogenicity of distinct FVIIIs and the role of HLAcII genetics in inhibitor development.

The inhibitors - a challenge for the management of patients with hereditary haemophilia A

INTRODUCTION

Our research strategy was aimed at evaluating the possible implication of the type of factor VIII product administered as substitution treatment to haemophilia A patients in the occurrence of inhibitors and their consequences on the management.

METHODS

Scientific articles from July 2015 to July 2017 were searched using the PubMed and PubMed Central databases. The used search terms included "haemophilia A", "inhibitors", "plasma-derived factor VIII" and "recombinant factor VIII".

RESULTS

The risk factors for inhibitors occurrence may be patients-related (genetic and nongenetic) and treatment-related. The possibility of a correlation between the increased purity of factor VIII given as substitution treatment and the occurrence of inhibitors is discussed in the light of literature data. Plasma-derived factor VIII is less immunogenic, but not entirely safe from the point of view of the possibility of transmitting biological agents. It is obvious that there is not enough plasma-derived factor VIII for the planet's needs. Recombinant factor VIII products have revolutionized the treatment of patients with haemophilia A over the past 3 decades by the disappearance of transfusion-related infections and their complications. They are safer in terms of pathogens and the new long-acting factor VIII products are based on recombinant DNA technology.

CONCLUSION

Plasma-derived or recombinant factor VIII products must co-exist on the market for the benefit of haemophilic patients. Future solutions could be: less immunogenic factor VIII products, nonfactor replacement strategies, or bispecific antibody that mimics the function of coagulation factor VIII.

Product type and other environmental risk factors for inhibitor development in severe hemophilia A

The development of FVIII inhibitory antibodies is currently the most challenging complication of treatment, affecting ~30% of severe hemophilia A patients. These inhibitors inactivate FVIII, rendering the treatment ineffective, causing disability and increasing morbidity and mortality. Inhibitor development results from a complex multicausal immune response involving both genetic and environmental risk factors. One of the most important modifiable risk factors is the source of FVIII products, eg, plasma-derived or recombinant FVIII. Other environmental risk factors, such as age at first treatment, regimen, and intensity of treatment, could contribute to inhibitor development. Severe bleeds, surgery, concomitant infections, or vaccinations may all be events initiating danger signaling resulting in an immune reaction towards administered FVIII. All in all, the etiology of inhibitor development still remains unclear. The risk factors have been stratified into genetic and environmental, but there are no definitive data to determine the impact of each of them.