Environmental risk factors for inhibitor development in children with haemophilia A: a case-control study

Relationship between mutations in severe hemophilia A and risk of inhibitor development: A large single-center study

BACKGROUND

One of the major problems for patients with severe hemophilia A (HA) is the development of neutralizing antibodies against factor VIII. This study aimed to analyze the molecular and clinical profiles of patients with severe HA and to determine if certain genetic variants predispose to inhibitor development in these patients.

METHODS

A single-center study was conducted among patients with severe HA between March 20, 2000, and June 31, 2023. Demographic data and laboratory results of patients were collected. The inverse-shifting PCR (IS-PCR) technique was initially used to screen patients for intron 22 and 1 inversions (Inv-22 and Inv-1).

RESULTS

A total of 480 patients with severe HA (408 without inhibitors and 72 with inhibitors) were enrolled in this study. The median age of the patients at the time of diagnosis was 6 months (IQR: 3 months to 18 months). Inv-22 was observed in 199 (41.5 %) of the cases. Among those patients who developed inhibitors, 53 (73.6 %) were classified as high-titer and 19 (26.4 %) as low-titer. Inv-22, positive family history of inhibitor formation, and history of intense injections revealed a statistically significant association with the risk of inhibitor development.

CONCLUSION

The results of this study confirm the important role of different genetic variants, family history of inhibitor formation, and history of intense injections for the formation of inhibitors in patients with severe HA. This would allow us to stratify the patients which can have important clinical implications, especially in terms of their management and outcome.

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.

Primary prophylaxis in children with severe haemophilia A and B-Implementation over the last 20 years as illustrated in real-world data in the PedNet cohorts

INTRODUCTION

The prophylactic regimen in children with severe haemophilia is suggested in various publications and guidelines. Few data exist on its implementation in clinical practice.

AIM

To investigate the implementation of primary prophylaxis based on real-life data from PedNet during the last 20 years.

METHODS

All children from the PedNet cohort (n = 1260) with severe haemophilia A (SHA) or severe haemophilia B (SHB), FVIII/IX < .01 IU/mL, born between 2000 and 2009 (Cohort I; SHA n = 662; SHB n = 88) and 2010-2019 (Cohort II; SHA n = 598; SHB n = 94) were included.

RESULTS

In SHA, the median age at start of prophylaxis was 17.3 months (IQR; 12.5-26.1) in Cohort I which decreased to 13.1 months (IQR; 10.4-19.1) in Cohort II (p < .000). "Once-a-week" prophylaxis at start increased from 49% to 68% (SHA) and 38% to 70% (SHB). FVIII doses were reduced from median 43.5 (IQR; 34.6-49.0) to 30.9 IU/kg (IQR; 26.3-46.3), while dosing with FIX did not change. After 2010 approximately 60% of the patients with SHA and SHB started prophylaxis before any joint bleed. The number of CVADs needed in both cohorts was around 30%. Incidences of inhibitors were unchanged: SHA (∼31%) and SHB (∼10%). Sporadic cases were diagnosed significantly later (median 8.3 months; IQR; 3.7-11.9) and they had more joint bleeds before start of prophylaxis.

CONCLUSION

Primary prophylaxis nowadays starts at an earlier age: before any joint bleed (60% of patients with SHA and SHB). Approximately 70% started on a once-weekly schedule with significantly reduced doses in SHA but unchanged in SHB.

Haemophilia A: A Review of Clinical Manifestations, Treatment, Mutations, and the Development of Inhibitors

The purpose of this narrative review was to provide an overview that allows readers to improve their understanding of hemophilia A, which is considered a genetic disease with a high impact on the quality of life of people who suffer from it is considered one of the diseases with the highest cost for health systems (In Colombia it is part of the five diseases with the greatest economic impact). After this exhaustive review, we can see that the treatment of hemophilia is on the way to precision medicine, which involves genetic variables specific to each race and ethnicity, pharmacokinetics (PK), as well as environmental factors and lifestyle. Knowing the impact of each of these variables and their relationship with the efficacy of treatment (prophylaxis: regular infusion of the missing clotting factor VIII in order to prevent spontaneous bleeding) will allow for individualizing the medical behavior in a cost-effective way. For this is required to build more strong scientific evidence with statistical power that allows us to infer.

Serum TNF-α Level as a Possible Predictor of Inhibitor Levels in Severe Hemophilia A

BACKGROUND

The development of factor VIII (FVIII) inhibitor in patients with hemophilia A (PWHA) is a great challenge for hemophilia care. Both genetic and environmental factors led to complications in PWHA. The development of inhibitory antibodies is usually induced by the immune response. Tumor necrosis factor α (TNF-α), one of the cytokines, might contribute to its polymorphism. In this study, we investigated the clinical factors, level of serum TNF-α, and polymorphism of c.-308G > A TNF - α gene in inhibitor development in severe PWHA.

METHODS

A cross-sectional study was conducted among all PWHA in West Java province. The clinical parameters, FVIII, FVIII inhibitor, and serum TNF-α level were assessed. The genotyping of -380G > A TNF-α gene polymorphism was performed using polymerase chain reaction and Sanger sequencing.

RESULTS

Among the 258 PWHA, 216 (83.7%) were identified as severe PWHA. The FVIII inhibitor was identified in 90/216 (41.6%) of severe PWHA, consisting of 45 high-titer inhibitors (HTI) and 45 low-titer inhibitors (LTI). There was a significant correlation between serum TNF-α level and the development of HTI (p = 0.043). The cutoff point of serum TNF-α level, which can be used to differentiate between HTI and LTI, was 11.45 pg/mL. The frequency of FVIII replacement therapy was significant only in HTI of severe PWHA regarding serum TNF-α level (p = 0.028). There is no correlation between polymorphisms of -380G > A TNF-α gene and inhibitor development (p = 0.645).

CONCLUSIONS

The prevalence of FVIII inhibitor in severe PWHA in West Java, Indonesia, was 41.6%. The frequency of replacement therapy is a risk factor for inhibitor development. Serum TNF-α level might be used to differentiate between high and low inhibitor levels in severe hemophilia A, and this might support decision making regarding treatment options for inhibitor in severe hemophilia A.

Simoctocog Alfa (Nuwiq) in Previously Untreated Patients with Severe Haemophilia A: Final Results of the NuProtect Study

INTRODUCTION

 FVIII inhibitor development is the most serious contemporary treatment complication in haemophilia A, particularly in previously untreated patients (PUPs). No inhibitors developed in clinical trials in previously treated patients treated with simoctocog alfa (Nuwiq), a fourth-generation recombinant FVIII produced in a human cell line.

METHODS

 The NuProtect study investigated the immunogenicity of simoctocog alfa in PUPs. NuProtect was a prospective, multinational, open-label, non-controlled, phase III study. PUPs with severe haemophilia A (FVIII:C <1%) of any age and ethnicity were treated with simoctocog alfa for 100 exposure days or a maximum of 5 years. Patients were true PUPs without prior exposure to FVIII concentrates or blood components. Inhibitor titres were measured with the Nijmegen-modified Bethesda assay; cut-off for positivity was 0.6 BU mL-1 (≥0.6 to <5 low-titre, ≥5 high titre).

RESULTS

 A total of 108 PUPs with a median age at first treatment of 12.0 months (interquartile range: 8.0-23.5) were treated with simoctocog alfa. F8 mutation type was known for 102 patients (94.4%) of whom 90 (88.2%) had null F8 mutations and 12 (11.8%) had non-null mutations. Of 105 PUPs evaluable for inhibitor development, 28 (26.7%) developed inhibitors; 17 high titre (16.2%) and 11 low titre (10.5%). No PUPs with non-null F8 mutations developed inhibitors.

CONCLUSION

 In the NuProtect study, the rate of inhibitor development in PUPs with severe haemophilia A treated with simoctocog alfa was lower than the rate reported for hamster-cell-derived recombinant factor VIII products in other recent clinical trials. No inhibitors were reported in PUPs with non-null F8 mutations.

Treatment-related risk factors for inhibitor development in non-severe hemophilia A after 50 cumulative exposure days: A case-control study

BACKGROUND

Non-severe hemophilia A patients have a life-long inhibitor risk. Yet, no studies have analyzed risk factors for inhibitor development after 50 factor VIII (FVIII) exposure days (EDs).

OBJECTIVES

This case-control study investigated treatment-related risk factors for inhibitor development in non-severe hemophilia A and assessed whether these risk factors were different for early versus late inhibitor development.

PATIENTS/METHODS

Non-severe hemophilia A patients (FVIII:C 2%-40%) were selected from the INSIGHT study. Inhibitor-positive patients were defined as early (<50 EDs) or late (>50EDs) cases and matched to 1-4 inhibitor-negative controls by year of birth, cumulative number of EDs, and center/country. We investigated treatment intensity during the last 10 EDs prior to inhibitor development. Intensive treatment was defined as: surgery, peak treatment (10 consecutive EDs), and high mean FVIII dose (>45 IU/kg/ED). Odds ratios (OR) were calculated by logistic regression.

RESULTS

Of 2709 patients, we analyzed 63 early and 26 late cases and 195 and 71 respectively matched controls. Peak treatment was associated with early and late inhibitor risk (crude OR 1.8, 95% confidence interval [CI] 1.0-3.4; 4.0, 95%CI 1.1-14.3). This association was slightly less pronounced after adjustment for mean FVIII dose. High mean FVIII dose was also associated with early and late inhibitor risk (crude OR 2.8, 95%CI 1.5-5.1; 4.5, 95%CI 1.2-16.6). Surgery increased inhibitor risk for early cases. This was less pronounced for late cases.

CONCLUSIONS

Our findings suggest that intensive FVIII treatment remains a risk factor for inhibitor development in non-severe hemophilia A after more than 50 EDs. Therefore, persistent caution is required throughout the life-time treatment course.

Tailored prophylaxis in children with severe hemophilia: A four-year Iranian study

BACKGROUND

Prophylaxis the current standard care for patients with severe hemophilia should be planned to optimize the replacement therapy and minimize bleeding. We report our single-center experience of tailored prophylaxis in children affected by hemophilia A (HA) and hemophilia B (HB).

METHODS

This study was conducted on 55 patients, under 15 years, with HA (PWHA, n: 46) and HB (PWHB, n: 9) between 2015 and 2019. According to the phenotype, three prophylaxis regimens: 25-50 unit/kg once, twice, or three-times a week for PWHA, and two: 30-50 unit/kg once or twice a week for PWHB were administered. Following the occurrence of > 3 joint bleeding, or > 4 soft tissue bleeding, or one spontaneous major bleeding in the last 3 months, the prophylaxis regimen is changed. Annualized bleeding rate (ABR), annualized joint bleeding rate (AJBR), target joints development, inhibitor development, and hemophilia joint health score (HJHS) also were assessed.

RESULTS

A mean ± SD of 2520 ± 1045 IU/kg/yr coagulation factor (F) VIII was used to reduce ABR and AJBR from 1.02 ± 1.11 and 0.8 ± 1.3 (in the first year of the study) to 0.27 ± 0.44 (P < 0.001) and 0.19 ± 0.38 (P = 0.004) (at the end of the study) in PWHA, respectively. Furthermore, in PWHB, in the first year of the study, with using 2168 ± 1216 IU/kg coagulation FIX, ABR and AJBR were 0.19 ± 0.39 and 0.06 ± 0.1. At the end of the study, ABR and AJBR were 0.02 ± 0.05 (p = 0.156) and 0.01 ± 0.03 (p = 0.361), respectively. During the study period, the mean number of the target joints and mean HJHS were 0.25 ± 0.57 and 7.6 ± 2.1 for PWHA and 0 and 6.3 ± 1.8 for PWHB, respectively. Finally, 5 PWHA (11 %) did not need dose-escalation in their prophylaxis regimen, whereas 31 (67 %) and 10 (21 %) PWHA needed two and three infusions a week, respectively. In PWHB, 7 (78 %) and 2 (22 %) were adjusted to receive a once and twice weekly regimen, respectively.

CONCLUSION

Our results suggest that tailored prophylaxis is an effective strategy to reduce the rate of bleeding and optimize the replacement therapy in children with hemophilia.

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.

Concomitant Use of rFVIIa and Emicizumab in People with Hemophilia A with Inhibitors: Current Perspectives and Emerging Clinical Evidence

Emicizumab, a humanized, bi-specific, monoclonal antibody subcutaneously administered, mimicking the function of FVIIIa, represents a milestone in treatment of patients affected by hemophilia A complicated with inhibitors. The HAVEN 1 and 2 studies have clearly established its superiority compared to bypassing agents for routine prophylaxis in preventing or reducing bleeding episodes in adult and pediatric patients with inhibitors. However, its protection against bleeding is only partial, and concomitant use of a bypassing agent may be required with potential prothrombotic risk. The emicizumab Phase III trials (HAVEN 1, 2 and 4) have shown that the traditional bypassing agents, activated prothrombin complex concentrates or recombinant activated factor VII (rFVIIa), may be necessary for the treatment of breakthrough bleeds or surgery management. A post hoc analysis in particular has shown that the concomitant use of emicizumab and rFVIIa is safe and no thrombotic events have been described. The review describes the state of the art of the concomitant use of emicizumab and rFVIIa for treating acute bleeding and surgeries, its efficacy and safety and the lack of thrombotic events associated with this treatment modality. Data still derive mainly from HAVEN trials; however, the availability of emicizumab in clinical practice is progressively increasing the number of patients treated and no adverse events directly attributed to this agent have occurred. The availability of guidelines for the use and dosing of rFVIIa during emicizumab prophylaxis is useful in clinical practice for managing suspected or ongoing bleeding, emergency situations and elective invasive procedures. In the next years, careful prospective post-licensure surveillance to monitor safety of rFVIIa use during prophylaxis with emicizumab is highly recommended.

Tolerance to FVIII: Role of the Immune Metabolic Enzymes Indoleamine 2,3 Dyoxigenase-1 and Heme Oxygenase-1

The occurrence of neutralizing anti-FVIII antibodies is a major complication in the treatment of patients affected by hemophilia A. The immune response to FVIII is a complex, multi-factorial process that has been extensively studied for the past two decades. The reasons why only a proportion of hemophilic patients treated with FVIII concentrates develop a clinically significant immune response is incompletely understood. The "danger theory" has been proposed as a possible explanation to interpret the findings of some observational clinical studies highlighting the possible detrimental impact of inflammatory stimuli at the time of replacement therapy on inhibitor development. The host immune system is often challenged to react to FVIII under steady state or inflammatory conditions (e.g., bleeding, infections) although fine tuning of mechanisms of immune tolerance can control this reactivity and promote long-term unresponsiveness to the therapeutically administered factor. Recent studies have provided evidence that multiple interactions involving central and peripheral mechanisms of tolerance are integrated by the host immune system with the environmental conditions at the time of FVIII exposure and influence the balance between immunity and tolerance to FVIII. Here we review evidences showing the involvement of two key immunoregulatory oxygenase enzymes (IDO1, HO-1) that have been studied in hemophilia patients and pre-clinical models, showing that the ability of the host immune system to induce such regulatory proteins under inflammatory conditions can play important roles in the balance between immunity and tolerance to exogenous FVIII.

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

Background

Risk factors for the development of inhibitors in previously untreated patients (PUPs) have been reported; this is not the case in previously treated patients (PTPs) owing to fewer studies. Risk factors may differ for the development of PTP versus PUP inhibitors. We aimed to identify risk factors for PTP inhibitor development.

Methods

Participants were patients at a hemophilia treatment center in Korea with current or past history of factor VIII or factor IX alloantibodies. Observed inhibitors were classified as PUP or PTP inhibitors based on the cumulative number of exposure days. We compared the type and severity of hemophilia, mutation type, and family history of inhibitor between PUPs and PTPs. Events within 3 months before the first inhibitor detection, such as change of the factor concentrate used, short-term high exposure or continuous infusion of factor concentrate, history of surgery, infection, diagnosis of cancer, use of immunosuppressive or immunomodulator agents, and vaccination were compared between PUPs and PTPs.

Results

We observed 5 PUP inhibitors and 5 PTP inhibitors in 115 patients with hemophilia A. Events that might be related to the development of inhibitors within 3 months prior to the first inhibitor detection were observed in all 5 PTPs. On the contrary, no such events were observed in any PUPs. The observed events included a change in the factor concentrate used, subsequent chemotherapy, and short-term high exposure to factor concentrates for controlling hemorrhage and surgeries.

Conclusion

Our results suggest a greater role of nongenetic factors in PTP inhibitor development.

Clinicopathological parameters influencing inhibitor development in patients with hemophilia A receiving on-demand therapy

BACKGROUND

Development of inhibitors to transfused factor VIII in patients with hemophilia A continues to be a challenge for professionals involved in hemophilia care. The majority of patients in India receive 'on-demand' rather than prophylactic therapy. The present study was done to assess the prevalence of factor VIII inhibitors in patients with hemophilia A (PWHA) receiving 'on-demand' therapy in a North Indian population and to study the clinicopathological parameters influencing the development of inhibitors.

METHODS

The study group comprised of 300 PWHA. Detailed clinical parameters, treatment history, bleeding profile including family history were recorded. Diagnosis of hemophilia A was confirmed by relevant coagulation tests. Inhibitors were screened using mixing based studies followed by quantification by Bethesda assay and Nijmegen modified Bethesda assay. Samples were collected from five cities in North India where a free supply of factor VIII was available and effectively used in three of these cities.

RESULTS

In the 300 PWHA, disease phenotype was severe in 219 (73%), moderate in 62 (20.67%) and mild in 19 (6.34%), based on the factor VIII bioassay. Inhibitor prevalence was 9.6% (n = 29) and seen only in the severe phenotype. Inhibitor titers ranged from 0.8 to 108.8 BU/ml. A total of 12 PWHA had low and 17 had high titers. Correlation of various clinicopathological parameters in inhibitor-positive versus negative PWHA showed significant correlation with age at onset of disease, severity of disease, age at first exposure to treatment, annual factor intake (IU/kg/year), intense treatment episodes and bleeding manifestations like central nervous system bleed and hematuria. The total study sample had blood group B in 33.34% PWHA, followed by O (27.34%), A (24.34%) and AB (15%), however, in inhibitor-positive samples, significant inhibitor formation was associated with the ABO subtype A (19/29, 65.51%).

CONCLUSIONS

Factor VIII inhibitor prevalence in PWHA receiving 'on-demand' therapy was 9.6%. Clinicopathological correlates of inhibitor development in such PWHA have been analyzed in this novel study.

Prophylactic versus on-demand treatments for hemophilia: advantages and drawbacks

INTRODUCTION

Early long-term prophylaxis is the standard of care to prevent joint bleeding and chronic arthropathy in patients with severe hemophilia. Areas covered: Despite the obvious prophylaxis advantages upon the clinical outcomes, there are still several drawbacks to be addressed for the optimal patients' compliance. Frequency of treatment due to short half-life of conventional FVIII and FIX concentrates, difficult venous access, adherence to the prescribed therapy and costs may represent significant critical issues. The development of inhibitors also makes replacement therapy ineffective, preventing patients from receiving long-term prophylaxis. This paper will review these drawbacks and the tools to overcome these limitations, mainly thanks to the use of extended half-life products and the development of novel non-conventional therapeutic approaches. Expert commentary: The use of extended half-life products may help in reducing the burden of the frequent intravenous administration and in better tailoring an individualized prophylaxis. The development of novel therapeutic approaches, like the bi-specific antibody mimicking the coagulation function of FVIII or inhibition of anticoagulant proteins may facilitate prophylaxis treatment not only in patients with inhibitors, but also in severe hemophilia patients without inhibitors. Exciting opportunities are emerging for improving prophylaxis in hemophilia.

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.

Modified Primary Prophylaxis in Previously Untreated Patients With Severe Hemophilia A in Iran

BACKGROUND

Recently the low-dose tailoring method of primary prophylaxis has been introduced for previously untreated patients with hemophilia A.

OBJECTIVE

To evaluate the efficacy and safety of low-dose tailoring method of primary prophylaxis in previously untreated patients with severe hemophilia A.

MATERIALS AND METHODS

In this pre-post interventional study, 33 patients with severe hemophilia A who were previously untreated and affiliated to universities in the capital city and southern Iran were evaluated during 2014 to 2015. Modified primary continuous prophylaxis was used for patients with age below 3 years old, after first and before the second episodes of obvious clinical bleeding in large joints or large soft tissue hematoma or large amount of bleeding. Prophylaxis was started by 25 IU/kg once per week and increased to twice or 3 times a week according to defined bleeding events.

RESULTS

The median age at diagnosis and age of starting prophylaxis were: 4 months (at birth, 22 mo) and 12 months (1 to 35 mo), respectively. Mean annual bleeding rate of patients after prophylaxis was 1.08±2.21 episodes per year. None of the patients had inhibitors before therapy. Inhibitor was present in 5 patients (15.1%) after prophylaxis.

CONCLUSIONS

It seems that modified primary continuous prophylaxis has been successful in reducing bleeding episodes in children with severe hemophilia A and in the texture of lower cost it can improve quality of life of these patients, especially in developing countries where financial resources are limited.

Timing and severity of inhibitor development in recombinant versus plasma-derived factor VIII concentrates: a SIPPET analysis

Essentials Recombinant factor VIII (rFVIII) was contrasted with plasma-derived FVIII (pdFVIII). In previously untreated patients with hemophilia A, rFVIII led to more inhibitors than pdFVIII. Inhibitors with rFVIII developed earlier, and the peak rate was higher than with pdFVIII. Inhibitors with rFVIII were more severe (higher titre) than with pdFVIII.

SUMMARY

Background The development of neutralizing antibodies (inhibitors) against factor VIII (FVIII) is the most severe complication in the early phases of treatment of severe hemophilia A. Recently, a randomized trial, the Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET) demonstrated a 2-fold higher risk of inhibitor development in children treated with recombinant FVIII (rFVIII) products than with plasma-derived FVIII (pdFVIII) during the first 50 exposure days (EDs). Objective/Methods In this post-hoc SIPPET analysis we evaluated the rate of inhibitor incidence over time by every 5 EDs (from 0 to 50 EDs) in patients treated with different classes of FVIII product, made possible by a frequent testing regime. Results The highest rate of inhibitor development occurred in the first 10 EDs, with a large contrast between rFVIII and pdFVIII during the first 5 EDs: hazard ratio 3.14 (95% confidence interval [CI], 1.01-9.74) for all inhibitors and 4.19 (95% CI, 1.18-14.8) for high-titer inhibitors. For patients treated with pdFVIII, the peak of inhibitor development occurred later (6-10 EDs) and lasted for a shorter time. Conclusion These results emphasize the high immunologic vulnerability of patients during the earliest exposure to FVIII concentrates, with the strongest response to recombinant FVIII products.

Partnering to change the world for people with haemophilia: 6(th) Haemophilia Global Summit, Prague, Czech Republic, 24-26(th) September 2015

The 6(th) Haemophilia Global Summit was held in Prague, Czech Republic, in September 2015. The programme was designed by an independent Scientific Steering Committee of haemophilia experts and aimed to share optimal management strategies for haemophilia at all life stages, explore recent potential advances in the management of haemophilia A and B and discuss challenges in haemophilia care. In this supplement from the meeting, Dan Hart reviews the lessons that can be learnt from cost-constrained environments with regard to improving care for people with haemophilia globally. Sébastien Lobet discusses the importance of physical activity for optimising care and Roseline d'Oiron and Jan Blatný consider the role of real-world data in understanding the effect of treatment in a clinical setting over the long term and the true impact of treatment on the day-to-day life of the patient. Gili Kenet addresses the current challenges relating to the optimal management of prophylaxis, and Gerry Dolan and Cedric Hermans discuss the value of pharmacokinetic (PK) parameters in informing treatment decisions. Cedric Hermans and Valérie Libotte explore the importance of considering social and occupational development factors as an integral part of haemophilia care, and Jan Astermark reviews key strategies to predict and prevent inhibitor development.

Different impact of factor VIII products on inhibitor development?

Inhibitors are the most serious side effect of haemophilia treatment; they occur in 25–30 % of all patients with severe haemophilia A. Over the last 2 decades, conflicting data on the impact of clotting products have been published.

Due to small studies of selected cases, appreciation of the impact of any particular product has been difficult. Moreover, the emphasis on inhibitor testing has led to increased detection of low-titre inhibitors (to >10 %), while the percentage of high-titre inhibitors is still around 20 %.

Other non-genetic risk factors, such as dosing and intensive treatment, are able to increase individual inhibitor risk. Early prophylaxis might reduce inhibitor risk. Well-defined large PUP studies including products should be considered. This can only be achieved in collaboration with all stakeholders.

In conclusion, while the impact of FVIII products on inhibitor development is large, presently the actual impact of any specific product is unclear.

Aspects of prophylactic treatment of hemophilia

Retrospective and prospective studies unambiguously show that prophylactic treatment of severe hemophilia A or B should be started as primary prophylaxis at 1–2 years’ of age and ideally before the first joint bleed. The dose and dose frequency should be individually tailored depending on the goal of treatment, venous access and the bleeding phenotype. The circumstances during the first exposures of factor VIII concentrates in hemophilia A may have an impact on the risk of developing inhibitors. Enhanced half-life products, in particular in hemophilia B, will facilitate treatment in patients with difficult venous access but also in achieving a higher trough level. Evidence accumulate that prophylactic treatment is beneficial also in adults and in patients with inhibitors.

Combination therapy for inhibitor reversal in haemophilia A using monoclonal anti-CD20 and rapamycin

Development of antibodies (inhibitors) against coagulation factor VIII (FVIII) is a major complication of intravenous replacement therapy in haemophilia A (HA). Current immune tolerance induction (ITI) regimens are not universally effective. Rituximab, a B cell-depleting antibody against CD20, has shown mixed results for inhibitor reversal in patients. This study aims to develop a combinatorial therapy for inhibitor reversal in HA, using anti-murine CD20 (anti-mCD20) antibody and rapamycin, which targets both B and T cell responses. Additionally, it extensively characterises the role of the IgG backbone in B cell depletion by anti-CD20 antibodies. For this, inhibitors were generated in BALB/c-HA mice by weekly IV injection of FVIII. Subsequently, anti-mCD20 (18B12) with IgG2a or IgG1 backbone was injected IV in two doses three weeks apart and B cell depletion and recovery was characterised. Rapamycin was administered orally 3x/week (for 1 month) while continuing FVIII injections. Altering the IgG backbone of anti-mCD20 from IgG2a to IgG1 reduced overall depletion of B cells (including memory B cells), and marginal zone, B-10, and B-1b cells were specifically unaffected. While neither antibody was effective alone, in combination with rapamycin, anti-mCD20 IgG2a but not IgG1 was able to reverse inhibitors in HA mice. This regimen was particularly effective for starting titres of ~10 BU. Although IgG1 anti-mCD20 spared potentially tolerogenic B cell subsets, IgG2a directed sustained hyporesponsiveness when administered in conjunction with rapamycin. This regimen represents a promising treatment for inhibitor reversal in HA, as both of these compounds have been extensively used in human patients.

Key insights to understand the immunogenicity of FVIII products

The treatment of haemophilia has made significant progress in recent decades, and patients are now being treated safely with great clotting products. However, inhibitor development remains the largest problem, particularly in children. Consequently, the haemostasis that was obtained with traditional clotting factors is not being achieved. Moreover, inhibitor complications translate into adult life and there are an increasing number of situations where adult patients with an inhibitor require major surgery but the clinician is faced with the knowledge that required haemostasis levels are difficult to achieve. Therefore, it is of upmost importance to consider factors relating to inhibitor development, and to determine how inhibitors can be prevented and/or eliminated. Of the various factors at play with regard to inhibitor development, it is important to consider the immunogenicity of factor VIII (FVIII) products, and this topic is the focus of the current paper.

Rationale for individualizing haemophilia care

Owing to the heterogeneity in the clinical phenotype of haemophilia A and B, it is now recognized that disease severity (based on factor VIII/IX activity) may no longer be the most appropriate guide for treatment and that a 'one-size-fits-all' approach is unlikely to achieve optimal therapy. Based on the present literature and consensus views of a group of experts in the field, this article highlights key gaps in the understanding of the diverse relationships between bleeding phenotype and factors such as joint health, genetic susceptibility, laboratory parameters, quality of life and management of pain. Early prophylaxis is a potential 'gold standard' therapy and issues surrounding inhibitor development, variations in its clinical use and long-term outcomes are discussed. Comprehensive treatment should be individualized for all patients (including those with mild or moderate haemophilia and carriers). Wherever possible all patients should be given prophylaxis. However, adult patients with a milder haemophilia phenotype may be candidates for ceasing prophylaxis and switching to on-demand treatment. Regardless, all treatment (on-demand and prophylaxis) should be tailored towards both the patient's personal needs and their clinical profile. In addition, as the associations between risk factors (psychosocial, condition-related and treatment-related) and clinical features are unique to each patient, an individualized approach is required to enable patients to alter their behaviour in response to them. The practical methodologies needed to reach this goal of individualized haemophilia care, and the health economic implications of this strategy, are ongoing topics for discussion.

Tailoring hemostatic therapies to lower inhibitor development in previously untreated patients with severe hemophilia A

After technological progress provided safer therapeutic products for patients with hemophilia A, the development of alloantibodies (inhibitors) neutralizing the coagulant activity of infused factor VIII (FVIII) remains the most serious complication of replacement therapy, predisposing patients to greater morbidity and causing higher treatment costs. The pathogenesis of inhibitors, which develop at a high rate in previously untreated children with severe hemophilia A, is multifactorial, resulting from complex interactions between genetic and environmental factors. Among non-genetic determinants, a key role is played by treatment-related factors, including the source of FVIII product (i.e., plasma derived or recombinant) and the mode of replacement therapy delivery (i.e., intensity, prophylaxis vs. on demand). We review the potential interventions on these modifiable factors that may help to lower the rate of inhibitor development. In addition, interest is currently directed toward the potential for lesser immunogenicity of novel hemostatic agents designed to decrease the dosing frequency or avoid/delay the need of FVIII replacement therapy.

Human von Willebrand factor/factor VIII concentrates in the management of pediatric patients with von Willebrand disease/hemophilia A

Several plasma-derived intermediate and high-purity concentrates containing von Willebrand factor (VWF) and factor VIII (FVIII) are currently available. The main role of these products in the management of the pediatric population is represented by the replacement therapy in patients with severe or intermediate forms of von Willebrand disease, in whom other treatments are ineffective or contraindicated. Another important role of VWF/FVIII concentrates in children may be their use in immune tolerance induction (ITI) protocols. ITI is particularly recommended for hemophilia A children who have developed an inhibitor against FVIII, currently the most serious complication of substitutive treatment in hemophilia. Although recombinant concentrates may represent the preferred option in children with hemophilia A, VWF/FVIII concentrates may offer an advantage in rescuing patients who failed previous ITI.

Whole-exome sequencing to identify genetic risk variants underlying inhibitor development in severe hemophilia A patients

The development of neutralizing antibodies (inhibitors) against coagulation factor VIII (FVIII) is the most problematic and costly complication of FVIII replacement therapy that affects up to 30% of previously untreated patients with severe hemophilia A. The development of inhibitors is a multifactorial complication involving environmental and genetic factors. Among the latter, F8 gene mutations, ethnicity, family history of inhibitors, and polymorphisms affecting genes involved in the immune response have been previously investigated. To identify novel genetic elements underling the risk of inhibitor development in patients with severe hemophilia A, we applied whole-exome sequencing (WES) and data analysis in a selected group of 26 Italian patients with (n = 17) and without (n = 9) inhibitors. WES revealed several rare, damaging variants in immunoregulatory genes as novel candidate mutations. A case-control association analysis using Cochran-Armitage and Fisher's exact statistical tests identified 1364 statistically significant variants. Hierarchical clustering of these genetic variants showed 2 distinct patterns of homozygous variants with a protective or harmful role in inhibitor development. When looking solely at coding variants, a total of 28 nonsynonymous variants were identified and replicated in 53 inhibitor-positive and 174 inhibitor-negative Italian severe hemophilia A patients using a TaqMan genotyping assay. The genotyping results revealed 10 variants showing estimated odds ratios in the same direction as in the discovery phase and confirmed the association of the rs3754689 missense variant (OR 0.58; 95% CI 0.36-0.94; P = .028) in a highly conserved haplotype region surrounding the LCT locus on chromosome 2q21 with inhibitor development.

Non-genetic risk factors and their influence on the management of patients in the clinic

The development of inhibitors is the most serious iatrogenic complication affecting patients with haemophilia. This complication is associated with impaired vital or functional prognosis, reduced quality of life and increased cost of treatment. The reasons why some patients develop antibodies to factor replacement and others do not remain unclear. It is however clear that inhibitor development results from a complex multifactorial interaction between genetic and non-genetic risk factors. Environmental influences implicated in increasing the risk of inhibitor formation can be viewed as modifiable risk factors. Therefore, identification of the non-genetic risk factors may offer the possibility of personalising haemophilia therapy by modifying treatment strategies in high-risk patients in the critical early phase of factor VIII exposure. In this article, we review the non-genetic factors reported as well as the potential impact of danger signals and the different scores for inhibitor development risk stratification.

The role of previously untreated patient studies in understanding the development of FVIII inhibitors

Development of inhibitors against factor VIII (FVIII), the major complication of haemophilia A treatment today, is influenced by multiple factors. Genetic (F8 mutation, family history, ethnicity, polymorphisms in immune modulating genes) and non-genetic (intensive exposure to FVIII, presence of pro-inflammatory signals as might occur with large bleeds, infections, surgery, or other immune stimulants [e.g. vaccines]) risk factors as well as their complex inter-relationships contribute to the inhibitor risk profile of haemophilia patients, particularly in the previously untreated patient (PUP) population. Studies in PUPs have been fundamental to furthering the understanding of FVIII inhibitor development, as well as discovering previously unappreciated risk factors. The multi-factorial nature of inhibitor development makes it difficult to ascertain the contribution of FVIII products in inhibitor development through individual PUP studies. Sufficiently powered studies of large cohorts may overcome these limitations but interpretations should be conducted cautiously. Proper design and implementation of PUP safety studies will become even more important with the introduction of new molecules, such as extended half-life or human cell-line derived FVIII that propose reduced immunogenicity. Despite these difficulties, carefully performed clinical studies in PUPs may provide important insights into the natural history of the immune response to FVIII and may suggest targets for intervention to reduce immunogenicity.

Diagnostic evaluation of our patients with hemophilia A: 17-year experience

AIM

Hemophilia A is a rare inherited bleeding disorder resulting from factor VIII deficiency and is a group of diseases characterized by intra-articular and intramuscular bleeding. In this study, we aimed to retrospectively evaluate the treatment outcomes, demographic and clinical characteristics of our patients who were treated and followed up for last 17 years in our pediatric hematology unit with a diagnosis of Hemophilia A.

MATERIAL AND METHODS

The medical records of 83 patients who were diagnosed with Hemophilia A and followed up between 1997 and 2014 in our hospital's pediatric hematology clinic were reviewed retrospectively. The demographic data, prophylaxis state, development of inhibitors and clinical characteristics of the patients were evaluated.

RESULTS

When the complaints at presentation were examined, it was found that 27 (32%) patients had hemarthrosis, 24 (29%) patients had ecchymosis and hematoma, 13 (16%) patients had prolonged bleeding after trauma or cut, 10 (12%) patients had gingival, mouth or nose bleeding, 4 (5%) patients had prolonged bleeding after circumcision, 4 (5%) patients had gastrointestinal bleeding, 1 (1%) patient had hematuria. Fifty (60%) patients were considered severe hemophilia A, 20 (24%) patients were considered moderate hemophilia A and 13 (16%) patients were considered mild hemophilia A according to factor activity. Among severe hemophilia A patients, primary prophylaxis was being administered in 2 (2%) patients and secondary prophylaxis was being administered in 40 (48%) patients. Inhibitor positivity was found in 8 (10%) of these patients. It is found that hemophilic artropathy developed in 17 patients and 8 of these 17 patients had undergone radioisotope synovectomy.

CONCLUSIONS

Treatment of severe bleeding in hemophilia A patients should be performed in hospital and the presence of inhibitor must be investigated in cases of uncontrolled bleeding where adequate doses of factor concentrates have been administered for treatment. In order to decrease the development of inhibitor, prophlaxis should be suggested to patients rather than repetetive treatment when bleeding occurs. The radioactive synovectomy should not be overlooked in countries like ours in which factors can not be used adequately.

Various regimens for prophylactic treatment of patients with haemophilia

Haemophilia prophylaxis is superior to on-demand treatment to prevent joint damage. 'High-dose prophylaxis' as used in Sweden is more effective in preventing arthropathy than an 'intermediate-dose regimen' (the Netherlands) and the Canadian tailored primary prophylaxis. Prophylaxis may reduce the risk of developing inhibitors. There is no difference in inhibitor risk between plasma derived and recombinant factor VIII (rFVIII) products but the Rodin study showed increased risk with second-generation rFVIII products. MRI is a new and very sensitive tool to detect the symptoms of early arthropathy but some results (soft tissue changes in 'bleed-free joints') still need to be investigated. Ultrasound is a very helpful method to aid diagnosis especially during the acute phase of a bleed. The risk of infection with central venous access remains a matter of debate. A fully implanted central venous access device (CVAD) has a significant lower risk of infection compared to external CVADs. Patient's age under 6 yr and inhibitor presence are additional risk factors for infections. The role of arteriovenous fistulae needs to be investigated because significant complications have been reported. Disease-specific quality of life instruments are complementary to generic instruments evaluating QoL in patients with haemophilia and have become important health outcome measures.

Improved prediction of inhibitor development in previously untreated patients with severe haemophilia A

Treatment of previously untreated patients (PUPs) with severe haemophilia A is complicated by the formation of inhibitors. Prediction of PUPs with high risk is important to allow altering treatment with the intention to reduce the occurrence of inhibitors. An unselected multicentre cohort of 825 PUPs with severe haemophilia A (FVIII<0.01 IU mL(-1) ) was used. Patients were followed until 50 exposure days (EDs) or inhibitor development. All predictors of the existing prediction model including three new potential predictors were studied using multivariable logistic regression. Model performance was quantified [area under the curve (AUC), calibration plot] and internal validation (bootstrapping) was performed. A nomogram for clinical application was developed. Of the 825 patients, 225 (28%) developed inhibitors. The predictors family history of inhibitors, F8 gene mutation and an interaction variable of dose and number of EDs of intensive treatment were independently associated with inhibitor development. Age and reason for first treatment were not associated with inhibitor development. The AUC was 0.69 (95% CI 0.65-0.72) and calibration was good. An improved prediction model for inhibitor development and a nomogram for clinical use were developed in a cohort of 825 PUPs with severe haemophilia A. Clinical applicability was improved by combining dose and duration of intensive treatment, allowing the assessment of the effects of treatment decisions on inhibitor risk and potentially modify treatment.

Current management of the hemophilic child: a demanding interlocutor. Quality of life and adequate cost-efficacy analysis

Hemophilias are the most known inherited bleeding disorders. The challenges in the management of hemophilic children are different from those in adults: prophylaxis regimen removed the hallmark of crippling disease with lifelong disabilities; individualized regimens are being implemented in order to overcome venous access problems. Presently, at least in high-income countries, advances in treatment of hemophilia resulted in continuous improvement of the patients' quality of life and life expectancy. Inhibitors remain the most severe complication of hemophilia therapy. The treatment' compliance is the key to achieve a successful management. The patient, his family, the medical and psychological team are the players of a comprehensive care system. The current management of hemophilic children is the example of huge resource investments enabling long-term benefits in particular quality of life as a primary objective of the healthcare process.