Impact of Choice of Treatment for Bleeding Episodes on Inhibitor Outcome in Patients With Mild/Moderate Hemophilia A and Inhibitors

The incidence and treatment of bleeding episodes in non-severe haemophilia A patients with inhibitors

The development of an inhibitory antibody in non-severe haemophilia A patients may aggravate the bleeding phenotype considerably. Effective treatment of bleeding episodes may be challenging, with ensuing severe complications. At present, evidence is scarce for optimal treatment of bleeding episodes in this patient group. The aim of this study was to describe the incidence and the treatment of bleeding episodes in inhibitor patients in a population-based unselected cohort of non-severe haemophilia A patients with clinically relevant inhibitors. Data were available for 100 of the 107 non-severe haemophilia A patients (factor VIII (FVIII) baseline, 2–40 lU/dl) from 29 centres in Europe and one centre in Australia who had developed a clinically relevant inhibitor between 1980 and 2011. The majority (89 %) of the patients were treated during the inhibitor period for bleeding episodes or a surgical intervention: 66 % needed treatment for bleeding episodes, at a median annual bleeding rate (ABR) of 1.1 (interquartile range (IQR) 0.1–2.5) and a median total of 2 (IQR 1–6) bleeding episodes. Compared to the median ABR before inhibitor development of 0.095 bleeds per year (IQR 0.02–0.42), the increase in ABR is more than a 10-fold. More than 90 % of the bleeding episodes were treated with only one type of product, most frequently (51 %) FVIII concentrates. This study provides the incidence of bleeding episodes and treatment choices in non-severe haemophilia A patients with inhibitors. The 10-fold increase to a median ABR of 1.1 episodes per year emphasizes the impact of inhibitor development for non-severe haemophilia A patients.

Molecular simulation studies of human coagulation factor VIII C domain-mediated membrane binding

The C-terminal C domains of activated coagulation factor VIII (FVIIIa) are essential to membrane binding of this crucial coagulation cofactor protein. To provide an overall membrane binding mechanism for FVIII, we performed simulations of membrane binding through coarsegrained molecular dynamics simulations of the C1 and C2 domain, and the combined C-domains (C1+C2). We found that the C1 and C2 domain have different membrane binding properties. The C1 domain uses hydrophobic spikes 3 and 4, of its total of four spikes, as major loops to bind the membrane, whereas all four of its hydrophobic loops of the C2 domain appear essential for membrane binding. Interestingly, in the C1+C2 system, we observed cooperative binding of the C1 and C2 domains such that all four C2 domain spikes bound first, after which all four loops of the C1 domain inserted into the membrane, while the net binding energy was higher than that of the sum of the isolated C domains. Several residues, mutations of which are known to cause haemophilia A, were identified as key residues for membrane binding. In addition to these known residues, we identified residues from the C1 and C2 domains, which are involved in the membrane binding process, that have not been reported before as a cause for haemophilia A, but which contribute to overall membrane binding and which are likely candidates for novel causative missense mutations in haemophilia A.

Rituximab as first-line treatment for the management of adult patients with non-severe hemophilia A and inhibitors

BACKGROUND

The role of immunosuppression in the management of patients with congenital hemophilia and inhibitors is uncertain. The use of rituximab has been limited to case reports and case series. In most reports, rituximab was used as second-line or third-line treatment following failure of conventional immune tolerance induction therapy, and more commonly in pediatric patients.

OBJECTIVES

The objective of this study was to describe our experience with rituximab for the eradication of factor VIII inhibitors in adult patients with non-severe hemophilia A.

PATIENTS

We retrospectively reviewed the medical records of adult patients with non-severe hemophilia A and a diagnosis of FVIII inhibitor treated with rituximab (four weekly doses of 375 mg m(-2) ) as first-line treatment at our hemophilia center.

RESULTS

We identified nine consecutive adult patients with hemophilia A (moderate, n = 5; mild, n = 4) at our institution between 2000 and 2013, with a median age of 54 years (range, 24-77 years) at the time of inhibitor diagnosis. No patient received concomitant immune tolerance induction therapy. All nine patients had successful eradication of FVIII inhibitors. The median time from the first dose of rituximab to a clinical response was 95 days (range, 12-278 days). The median follow-up was 56 months (range, 13-139 months). Following inhibitor eradication, eight patients were rechallenged with FVIII concentrates. Two patients developed inhibitor recurrence associated with surgery.

CONCLUSION

This case series demonstrates that rituximab is a useful first-line treatment to achieve sustained inhibitor eradication in adult patients with non-severe hemophilia A.

How I treat inhibitors in haemophilia

The management of patients with inhibitors is the greatest challenge facing haemophilia health professionals. Immune tolerance induction (ITI) can be successful in eliminating the inhibitor in the majority of patients, provided it is started soon after the inhibitor develops and the titre of the inhibitor is <10 BU at commencement of ITI. Acute bleeding is treated using one of two bypassing agents, which exhibit similar efficacy and safety. Surgery in inhibitor patients is challenging and should only be carried out in experienced centres.

F8 and F9 mutations in US haemophilia patients: correlation with history of inhibitor and race/ethnicity

Both genetic and treatment-related risk factors contribute to the development of inhibitors in haemophilia. An inhibitor surveillance system piloted at 12 US sites has the goal of assessing risk factors through prospective data collection. This report examines the relationship of genotype and race/ethnicity to history of inhibitor in a large cohort of US haemophilia patients. Mutation analysis was performed on 676 haemophilia A (HA) and 153 haemophilia B (HB) patients by sequencing, Multiplex Ligation-dependent Probe Amplification, and PCR for inversions in F8 introns 22 (inv22) and 1 (inv1). Two HB patients with deletions had history of inhibitor. In severe HA, frequency of history of inhibitor was: large deletion 57.1%, splice site 35.7%, inv22 26.8%, nonsense 24.5%, frameshift 12.9%, inv1 11.1% and missense 9.5%. In HA, 19.6% of 321 White non-Hispanics (Whites), 37.1% of 35 Black non-Hispanics (Blacks) and 46.9% of 32 Hispanics had history of inhibitor (P = 0.0003). Mutation types and novel mutation rates were similar across ethnicities. When F8 haplotypes were constructed, Whites and Hispanics showed only H1 and H2. Within H1, history of inhibitor was 12.4% in Whites, 40.0% in Blacks (P = 0.009) and 32.4% in Hispanics (P = 0.002). Inhibitor frequency is confirmed to vary by mutation type and race in a large US population. White patients with history of inhibitor did not exhibit rare F8 haplotypes. F8 gene analysis did not reveal a cause for the higher inhibitor frequencies in Black and Hispanic patients.

Mild haemophilia: a disease with many faces and many unexpected pitfalls

SUMMARY

Despite major advances in diagnosis and treatment, the management of patients with mild haemophilia (MH) remains a major challenge. Mild haemophilia is defined by factor levels between 0.05 and 0.40 IU mL(-1). The bleeding associated with mild haemophilia is most frequently episodic, occurring during surgery or following trauma. Spontaneous bleeding is rare. Diagnosis is sometimes delayed because of insensitivity of screening clotting assays or discrepancies in factor VIII activity as measured by different assays. The treatment of choice in mild haemophilia A is desmopressin, which typically induces a 2-6-fold increase of factor VIII over baseline. However, desmopressin has its limitations in this setting such as the occurrence of tachyphylaxis and failure to respond in an undetermined proportion of patients. Factors underlying poor biological response or magnitude of response to desmopressin are incompletely understood. Inhibitor development in mild haemophilia is particularly distressing. This complication arises at an older age in this patient group because of infrequent need for factor VIII replacement. Inhibitors in mild haemophilia patients often cross-react with endogenous factor VIII resulting in severe spontaneous bleeding frequently in a postoperative setting. Intensive perioperative use of factor VIII and some specific mutations induce a particularly high risk for inhibitor development, but risk factors are incompletely understood. For reasons of the older age of the patients, treatment of bleeding with bypassing agents may cause major thrombotic complications. Data on therapeutic options for inhibitor eradication in patients with mild haemophilia are particularly scarce. With increased life-expectancy for all haemophilia patients, the group of elderly patients with mild haemophilia requiring major surgery will further increase. Prevention of inhibitors, particularly in this patient group, should be a major topic of interest in both clinic and research.

Molecular and phenotypic determinants of the response to desmopressin in adult patients with mild hemophilia A

BACKGROUND

The relationship of the biologic response to desmopressin with the F8 mutation and physiological characteristics has been poorly investigated in patients with mild hemophilia A.

OBJECTIVES

We prospectively assessed the molecular and phenotypic determinants of the biologic response to desmopressin in a cohort of 50 patients with mild hemophilia A.

METHODS

Up to 24 h after desmopressin, blood samples were serially obtained and factor (F)VIII and von Willebrand factor (VWF) measured. The promoter region, all exons and exon-intron boundaries of the F8 gene were screened using denaturing high-performance liquid chromatography (DHPLC). Direct sequencing was done when DHPLC screening was normal. Genomic DNA was also sequenced for exons 18-21, 24 and 27 of VWF.

RESULTS

Mean basal FVIII:C was 19 +/- 9 IU dL(-1) (range 6-37) and the median postdesmopressin peak increase was 2.5-fold (range 1.1-7.1). Eleven patients with a cross-reacting material positive (CRM(+)) phenotype had similar basal levels and relative increases of FVIII:C to the remaining patients with low FVIII:Ag. Using multivariate regression, FVIII:C half-life was positively related to basal and peak VWF:Ag levels (P = 0.008) and patient age (P = 0.004). Eleven patients had evidence of reduced FVIII survival. While 27 different gene mutations were identified in 41 patients, nine patients had no detectable mutation. These patients had significantly smaller peaks and smaller relative increase of postdesmopressin FVIII:C (median FVIII:C 26 IU dL(-1) vs. 54 IU dL(-1); P < 0.001; fold 1.8 +/- 0.6 vs. 2.9 +/- 0.8; P = 0.002).

CONCLUSIONS

In this cohort of patients with mild hemophilia A, a poor biologic response to desmopressin was frequently associated with the absence of detectable F8 mutations.

Thrombin generation and platelet activation induced by rFVIIa (NovoSeven) and NN1731 in a reconstituted cell-based model mimicking haemophilia conditions

Replacement therapy with factor VIII (FVIII) and factor IX (FIX) is routinely used in haemophilia patients with haemophilia A and B, respectively, while recombinant activated FVII (rFVIIa) has proven to induce haemostasis in haemophilia patients with inhibitors. To evaluate the effect of therapeutic intervention in patients with residual factor activities, the effects of increasing concentrations of rFVIIa or NN1731 on thrombin generation and platelet activation were measured in a cell-based model system mimicking severe, moderate and mild haemophilia A or B. Purified monocytes stimulated to express tissue factor and non-activated platelets from peripheral blood of healthy donors were incubated with a mixture of purified human coagulation factors in the absence or presence of increasing concentrations of FVIII or FIX. Sub-samples were analysed for thrombin activity and platelet activation measured as exposure of P-selectin by flow cytometry. Dose-dependent increases in thrombin generation and platelet activation were observed following increasing concentrations of rFVIIa or NN1731 in both haemophilia A- and B-like conditions. At 25 nm rFVIIa, which nears the peak levels in patient plasma after 90 microg kg(-1) intravenous dosing, the effects on maximum thrombin generation rate (maxTG) at 1-10% FVIII were comparable to those at 100% and 200% FVIII in the absence of rFVIIa. Normalization of maxTG required 500 nm rFVIIa and 25 nm NN1731 or 25-100 nm rFVIIa and 5 nm NN1731 in severe or moderate/mild haemophilia A and haemophilia B, respectively. This suggests that NN1731 holds its promise as a future bypassing agent for haemophilia patients with and without inhibitors.

Optimising immune tolerance induction strategies in the management of haemophilia patients with inhibitors: a cost-minimisation analysis

BACKGROUND

The objective of this study was to model the economic impact of optimal dosing of immune tolerance induction (ITI) in haemophilia patients with inhibitors. Evidence based research suggests that, in the right patient population characterised by ITI risk status, the use of high-dose ITI regimen in 'poor risk' patients, and the low-dose regimen in 'good risk' patients, would be the cost effective strategy. The model also explored the impact of anamnestic response (AR), a phenomenon which worsens patients' ITI risks.

METHOD

A cost-minimisation technique was used to compare the cost of managing inhibitor patients whose bleeds were managed pre-ITI with an immunogenic bypassing agent, activated prothrombin complex concentrate (APCC), with patients previously on a non-immunogenic product, recombinant activated factor VII (rFVIIa). Patients were subsequently offered a low-dose or high-dose ITI regime depending on their ITI risk status. The study perspective was that of the United Kingdom NHS, hence, all resources used were based on UK costs.

RESULTS

The model estimated the mean cost of managing inhibitor patients from detection of titres through ITI to be 959,250.39 pound sterling and 770,834.17 pound sterling in the APCC and rFVIIa treatment options, respectively. Meanwhile, the costs per effectively tolerised patients were 1,505,279 pound sterling and 1,196,706 pound sterling for APCC and rFVIIa treated patients, respectively. Of the incremental cost in the APCC-treated patients in the model, 129,367 pound sterling (68%) represents additional ITI cost attributable to anamnestic response to earlier treatment with an immunogenic bypassing agent (APCC).

CONCLUSION

The study concludes that decreasing factor VIII usage during ITI, through the identification and management of 'good risk' ITI patients with low-dose protocol, while managing 'poor risk' patients with high-dose regimen, will significantly lower the cost of ITI. Furthermore, avoiding AR prior to ITI by using non-immunogenic bypassing agents to manage spontaneous bleeds also has the potential for significant cost savings.

A systematic approach to controlling problem bleeds in patients with severe congenital haemophilia A and high-titre inhibitors

The presence of inhibitory antibodies to clotting factors complicates the treatment of bleeding in haemophilia patients. For patients with high-titre inhibitors, bypassing agents are essential to haemostatic management. To determine optimal treatment practices, an international panel of physicians convened to develop a systematic treatment approach for problem bleeds (i.e. bleeds that are unresponsive to initial therapy with a single agent within a reasonable amount of time) in haemophilia patients with inhibitors.

AIM

The goal of this panel was to develop a consensus algorithm that would aid physicians in considering a variety of treatment approaches to optimize patient care by preventing extensive therapy with inadequate treatments that may lead to suboptimal patient outcomes and unnecessary costs.

METHODS

Consensus opinions were analyzed for clinical preferences at different time periods, depending on patient response to treatment. Decision-making points were defined based on the type of bleed: every 8-12 h for the first 24 h, then every 24 h thereafter for limb-threatening bleeds; every 2-4 h for 2-7 days for life-threatening bleeds.

RESULTS

The resultant consensus guidelines provide a generalized methodology to guide the treatment of problem bleeds in patients with severe haemophilia A and inhibitors, and emphasize changing treatment at the first sign of an inadequate haemostatic response. The treatment algorithms apply to both paediatric and adult patients, although the differences between the two groups were reviewed.

CONCLUSION

These guidelines are focused on optimising the timing of treatment decisions, which may lead to faster responses and improved outcomes.

International workshop on immune tolerance induction: consensus recommendations

Although immune tolerance induction (ITI) has been used for 30 years to eliminate inhibitors and restore normal factor pharmacokinetics in patients with hemophilia, there is a paucity of scientific evidence to guide therapeutic decision-making. In an effort to provide direction for physicians and hemophilia treatment center staff members, an international panel of hemophilia opinion leaders met to develop consensus recommendations for ITI in patients with severe and mild hemophilia A and hemophilia B. These recommendations draw on the available published literature and the collective clinical experience of the group and are rated based on the level of supporting evidence.

Immune tolerance therapy for factor VIII inhibitors: moving from empiricism to an evidence-based approach

Currently, the only proven strategy for achieving antigen-specific tolerance to factor VIII (FVIII) is immune tolerance induction (ITI) therapy. This paper discusses our current knowledge of the host and treatment factors, as well as supportive care initiatives, known or suspected to influence the outcome of ITI in the treatment of inhibitors arising in patients with severe hemophilia A. Among these, questions surrounding the choice of therapeutic product and/or dosing regimen generate the most controversy, given the lack of a definitive evidence-based approach to either. Furthermore, the potential for central venous access device (CVAD) and intercurrent bleeding complications to impact the ultimate success of ITI remains unclear. The ongoing clinical trials designed to further clarify several of these polarizing issues are reviewed. This paper also explores the current and future role of immune modulation in possible salvage, ancillary or primary alternative tolerance induction strategies. The special cases of low titer/ responding inhibitors and inhibitors developing in mild hemophilia A patients are considered. Finally, this paper summarizes the currently recommended approach to ITI and makes the case for a move from empiric therapeutics to a risk-stratified evidence-based approach to FVIII inhibitor eradication.

Rituximab treatment of mild haemophilia A with inhibitors: a proposed treatment protocol

Inhibitors are an uncommon complication of mild haemophilia A but represent a severe disease, typically with high titre inhibitors and an associated high rate of bleeding. We present data from three patients with MHAI who were successfully treated with Rituximab alone and unequivocally prove that such inhibitors respond to this agent. A treatment protocol is suggested.

Continuous infusion of coagulation factors: current opinion

PURPOSE OF REVIEW

To review the most recent reports on continuous infusion of coagulation factors, focusing on the current issues relating to this mode of therapy.

RECENT FINDINGS

Continuous infusion has been extensively used as an alternative to intermittent bolus factor replacement since the 1990s. To date, more than 100 reports comprising more than 800 continuous infusion treatments in various clinical situations have been published, with an increase in the current utilization of recombinant coagulation factors. An excellent hemostatic efficacy of continuous infusion has been reported. Continuous infusion protocols, however, still vary widely in terms of the different hemostatic levels targeted, dosage regimens, modes of continuous infusion and duration of therapy, which obviously result in variations in the cost-effectiveness reported by different centers.

SUMMARY

Continuous infusion has been shown to be a safe and cost-effective mode of replacement for treatment of hemophilia. The lack of evidence-based information on the hemostatic levels to be maintained in specific clinical situations, and recent concerns regarding the development of inhibitors, particularly in patients with mild hemophilia treated with continuous infusion, need to be addressed by prospective, randomized studies that compare traditional intermittent injections and the continuous infusion mode of factor replacement.