Inhibitors and prophylaxis in paediatric haemophilia patients: Focus on the German experience

Management of Severe Hemophilia A: Low-Dose Prophylaxis vs. On-Demand Treatment

INTRODUCTION

Prophylactic clotting factor infusion regimens to prevent bleeding and joint deformity has become the standard of care in severe hemophilia A patients.

AIM

To assess low-dose factor prophylaxis in our population as an alternative approach to managing severe hemophilia A.

METHODS

A prospective cohort study that included 68 hemophilia A patients divided into two groups, i.e., Prophylaxis and on-demand. The two groups were compared for annualized bleeding rate (ABR), hospitalization, units of factor VIII (FVIII) infused, or plasma products transfused, i.e., fresh frozen plasma (FFP) and cryoprecipitate (CP), and development of FVIII inhibitors.

RESULTS

Of the 68 patients recruited in this study, 25 (36.7%) were in the prophylaxis group, and 43(63.3%) were in the on-demand group. The on-demand group presented a higher median-IQR ABR [8(20-3) vs. 5(10-1.5), p-value 0.024], several hospitalizations (39.7% vs. 0, p-value 0.001), and inhibitor development (9.3% vs. 0, p-value 0.289) compared to the prophylaxis group. The prophylaxis approach demonstrated a significant negative correlation of ABR with FVIII prophylaxis (r=-0484, p=value=0.014). Moreover, no hospitalizations or inhibitor development was observed in the prophylaxis group. The estimated annual consumption of FVIII was 328 IU/kg/year in the on-demand group and 1662.6 IU/kg/year in the prophylaxis group. However, a highly significant difference in plasma product utilization was observed between the two groups, i.e., p-value <0.001 and 0.038 for FFP and CP, respectively.

CONCLUSION

Low-dose factor prophylaxis resulted in improved outcomes compared to on-demand treatment in terms of ABR, joint bleeding, hospitalization, and the development of inhibitors. This treatment approach should be adopted as an economically feasible alternative to high-dose Prophylaxis in resource-constrained countries.

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.

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.

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.

Complement C3 is a novel modulator of the anti-factor VIII immune response

Development of neutralizing antibodies against therapeutic Factor VIII (FVIII) is the most serious complication of the treatment of hemophilia A. There is growing evidence to show the multifactorial origin of the anti-FVIII immune response, combining both genetic and environmental factors. While a role for the complement system on innate as well as adaptive immunity has been documented, the implication of complement activation on the onset of the anti-FVIII immune response is unknown. Here, using in vitro assays for FVIII endocytosis by human monocyte-derived dendritic cells and presentation to T cells, as well as in vivo complement depletion in FVIII-deficient mice, we show a novel role for complement C3 in enhancing the immune response against therapeutic FVIII. In vitro, complement C3 and its cleavage product C3b enhanced FVIII endocytosis by dendritic cells and presentation to a FVIII-specific CD4⁺ T-cell hybridoma. The C1 domain of FVIII had previously been shown to play an important role in FVIII endocytosis, and alanine substitutions of the K2092, F2093 and R2090 C1 residues drastically reduce FVIII uptake in vitro. Interestingly, complement activation rescued the endocytosis of the FVIII C1 domain triple mutant. In a mouse model of severe hemophilia A, transient complement C3 depletion by humanized cobra venom factor, which does not generate anaphylatoxin C5a, significantly reduced the primary anti-FVIII immune response, but did not affect anti-FVIII recall immune responses. Taken together, our results suggest an important adjuvant role for the complement cascade in the initiation of the immune response to therapeutic FVIII.

The prevalence of factor VIII and IX inhibitors among Saudi patients with hemophilia: Results from the Saudi national hemophilia screening program

Hemophilia A and B are X-linked diseases that predominantly affect male patients. Patients can develop coagulation factor inhibitors, which exponentially increases the treatment cost. However, the prevalence of factor VIII and IX inhibitors in Saudi Arabia is unclear.This study aimed to determine the Saudi prevalence of factor VIII and IX inhibitors.This 4-year, 7-center, cross-sectional study evaluated the Saudi prevalences of hemophilia A and B. We collected the patients' clinical data, evaluated their disease, and tested for factor inhibitors.We included 202 patients with hemophilia (median age at diagnosis: 0.13 years, range: birth-34.8 years). The patients included 198 male patients (98%), 148 patients with hemophilia A (73.3%), and 54 patients with hemophilia B (26.7%). The patients exhibited severe factor VIII activity (<1%; 121 patients; 5.2%), moderate activity (1-5%; 7 patients; 4.9%), and mild activity (14 patients; 9.9%). Among the patients with care-related data, most patients were treated for episodic bleeding (76.8%) or received prophylaxis (22.6%); 1 patient received both treatments. Among the patients with source-related data, the factor replacements were derived from plasma (48.4%), recombinant concentrates (22.9%), both sources (14.6%), or fresh frozen plasma (14.1%). Factor VIII inhibitors were observed in 43 (29.3%) of the 147 patients, and only 1 of the 54 patients developed factor IX inhibitors. Most patients who developed inhibitors had severe hemophilia (40/44; 90.9%), and inhibitors were also common among patients who received recombinant products (14/43; 32.6%).The Saudi prevalence of factor inhibitors was similar to those among other ethnic populations.

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.

Inhibitor development in previously untreated patients with severe haemophilia A: a nationwide multicentre study in Finland

INTRODUCTION

Currently the most serious treatment complication of haemophilia is the inhibitor development (ID), i.e. neutralizing antibody development.

AIM

This nationwide multicentre study in Finland evaluated the incidence and risk factors of ID in previously untreated patients (PUPs) with severe haemophilia A (FVIII:C < 0.01 IU mL(-1) ).

METHODS

We enrolled all PUPs (N = 62) born between June 1994 and May 2013 with at least 75 exposure days (EDs) to screen ID during follow-up extending to September 2013.

RESULTS

Thirteen ID (21% of 62) occurred; 10 (16% of 62) with high titre. Fifty-one patients (82%) were on primary prophylaxis (regular prophylaxis before the age of 2 and before the first joint bleed) from the median age of 11.4 months, 90% via a central venous access device. The initial product was rFVIII in 63% and pd-FVIII in 37%, moreover in 24% pd-FVIII was switched to rFVIII concentrate during the 75 EDs. Non-transient inhibitors developed in 9/51 (17.6%; 13.7% high titre) children with primary and in 4/11 (36.4%; 27.3% high titre) patients with secondary prophylaxis (P = 0.24). Overall, 74% had a high-risk genotype similarly distributed among the prophylaxis groups. The history of a major bleed enhanced ID (aHR, 4.0; 95% CI, 1.2-13.7), whereas FVIII treatment intensity or source and early implantation of ports did not increase ID risk.

CONCLUSION

The cumulative incidence of ID was low notwithstanding prevalent high-risk mutations. Despite patient-related risk factors, our management involving early intensive primary prophylaxis via ports helps to prevent bleeds and lower the incidence of inhibitors.

The growing number of hemophilia registries: Quantity vs. quality

Registries for rare diseases provide a tool for obtaining an overview of the clinical situation and can be used to discover points of improvement and to monitor long-term safety. Registries could also become a powerful tool to provide supporting information for marketing authorization. There is an urgent need for a pan-European or global strategy that supports consistent data. Therefore, transparency in data collection, harmonization of the database structures, and the convergence of scientific approaches are required.