Consensus-Based Expert Recommendations on the Management of Hemophilia A in the Gulf Region

BACKGROUND

Hemophilia A presents a significant health challenge in the Gulf region, where it has an especially high prevalence. There are several unmet needs associated with the management of hemophilia A in the region. The aim of this manuscript was to contextualize unmet management needs, provide recommendations to optimize care, and specify requirements for the establishment of gene therapy centers in the region.

SUMMARY

An expert panel was assembled comprising ten clinical hematologists from Kuwait, Oman, Saudi Arabia, and the UAE. The Delphi methodology was used to obtain a consensus on statements relating to several aspects of hemophilia A. A consensus was reached for all statements by means of an online, anonymized voting system. The consensus statements pertain to screening and diagnosis, treatment approaches, and requirements for the implementation of gene therapy.

KEY MESSAGES

There are significant challenges that hinder the optimal management of hemophilia A in the Gulf region. The consensus statements presented provide specific recommendations to improve diagnostic and treatment approaches, promote multidisciplinary care, and optimize regional data generation and reporting. These statements also delineate the requirements for the establishment of gene therapy centers for hemophilia A in the region.

A review of the rationale for gene therapy for hemophilia A with inhibitors: one-shot tolerance and treatment?

The therapeutic landscape for people living with hemophilia A (PwHA) has changed dramatically in recent years, but many clinical challenges remain, including the development of inhibitory antibodies directed against factor VIII (FVIII) that occur in approximately 30% of people with severe hemophilia A. Emicizumab, an FVIII mimetic bispecific monoclonal antibody, provides safe and effective bleeding prophylaxis for many PwHA, but clinicians still explore therapeutic strategies that result in immunologic tolerance to FVIII to enable effective treatment with FVIII for problematic bleeding events. This immune tolerance induction (ITI) to FVIII is typically accomplished through repeated long-term exposure to FVIII using a variety of protocols. Meanwhile, gene therapy has recently emerged as a novel ITI option that provides an intrinsic, consistent source of FVIII. As gene therapy and other therapies now expand therapeutic options for PwHA, we review the persistent unmet medical needs with respect to FVIII inhibitors and effective ITI in PwHA, the immunology of FVIII tolerization, the latest research on tolerization strategies, and the role of liver-directed gene therapy to mediate FVIII ITI.

Gene therapy for hemophilia, a clinical viewpoint

Gene therapy for hemophilia has been investigated for decades but no breakthroughs were made until Nathwani et al. achieved a significant and sustainable factor IX increase in hemophilia B patients in 2011. About eleven years later, in August 2022, the first hemophilia A gene therapy product was approved by the European Commission and hemophilia treatment entered a new era. This review does not focus on the newest advances but rather the practical aspects of gene therapy aiming to provide an overview for physicians who treat hemophiliacs who did not participate in the clinical trials. The current status of gene therapy, focusing particularly on products likely to be clinically available soon, are reviewed and summarized. Currently, possible limitations of gene therapy are pre-existing neutralizing antibodies toward the vector, liver health, age, and inhibitor status. Possible safety concerns include infusion reactions, liver damage, and adverse effects from immune suppressants or steroids. In summary, generally speaking, gene therapy is effective, at least for several years, but the exact effect may be unpredictable and intensive monitoring for several months is needed. It can also be considered safe with careful practice on selected patients. In its current form, gene therapy will not replace all hemophilia treatments. Advances in non-factor therapy will also improve hemophilia care greatly in the future. We envisage that gene therapy may be included in multiple novel therapies for hemophilia and benefit some hemophilia patients while novel non-factor therapies may benefit others, together fulfilling the unmet needs of all hemophilia patients.

Recombinant factor VIII Fc fusion protein for first-time immune tolerance induction: final results of the verITI-8 study

Inhibitor development remains a major challenge in factor VIII (FVIII) replacement therapy. verITI-8 is the first prospective study of a recombinant FVIII Fc fusion protein (rFVIIIFc; efmoroctocog alfa) for first-time immune tolerance induction (ITI) in males with severe hemophilia A and high-titer inhibitors (historical peak ≥5 Bethesda units [BU]/mL). In this single-arm, open-label, multicenter study, screening was followed by ITI (rFVIIIFc 200 IU/kg per day until tolerization or maximum of 48 weeks). Those who achieved ITI success entered a tapering period, returning to standard prophylaxis, and then entered follow-up. Primary end point was time to tolerization with rFVIIIFc defined by inhibitor titer <0.6 BU/mL, incremental recovery (IR) ≥66% of expected IR (IR ≥1.32 IU/dL per IU/kg), and half-life (t½) ≥7 hours within 48 weeks. Sixteen patients received ≥1 rFVIIIFc dose. Twelve (75%), 11 (69%), and 10 patients (63%), respectively, achieved negative inhibitor titers, an IR ≥66%, and a t½ ≥7 hours (ie, tolerance) within 48 weeks. Median times in weeks to achieve these markers of success were 7.4 (interquartile range [IQR], 2.2-17.8), 6.8 (IQR, 5.4-22.4), and 11.7 (IQR, 9.8-26.2), respectively. All patients experienced ≥1 treatment-emergent adverse event (TEAE), and 1 reported ≥1 related TEAE (injection site pain). Nine patients experienced ≥1 treatment-emergent serious AE. No thrombotic events, discontinuations because of AEs, or deaths were reported during the study. As the first extended half-life rFVIII with prospective data in ITI, rFVIIIFc offered short time to tolerization with durable responses in almost two-thirds of patients and was well tolerated. This trial was registered at www.clinicaltrials.gov as #NCT03093480.

Early immune tolerance induction is a unique predictor of favorable outcomes in hemophilia A children with intron 22 inversion and high-responding inhibitors

BACKGROUND

The predictors of immune tolerance induction (ITI) outcomes in hemophilia A (HA) patients with the same F8 genetic background have not yet been evaluated, although the F8 genotype is strongly associated with ITI response. This study aims to explore the predictors of ITI outcomes in the same F8 genetic background by focusing on intron 22 inversion (Inv22) patients with high-responding inhibitors.

METHODS

HA children with Inv22 and high-responding inhibitors who received low-dose ITI therapy over 24 months were included in this study. ITI outcomes were centrally assessed at the 24th month of treatment. The predictive ability of clinical variables to identify ITI success was determined using the receiver operating characteristic (ROC) curve, and the predictor of ITI outcomes was analyzed on the multivariable Cox model.

RESULTS

Among the 32 patients investigated, 23 (71.9 %) achieved success. In univariate analysis, interval time from inhibitor diagnosis to ITI start (interval-time) was significantly associated with ITI success (P = 0.001); however, inhibitor titers showed no significance (P > 0.05). The interval-time demonstrated a good predictive value for ITI success with the area under the ROC curve of 0.855 (P = 0.002), and the cutoff value was 25.8 months (sensitivity, 87.0 %; specificity, 88.9 %). In the multivariable Cox model which considered success rate and time to success, interval-time was the only independent predictor (<25.8 months vs. ≥25.8 months, P = 0.002).

CONCLUSIONS

The interval-time was first identified as a unique predictor of ITI outcomes in HA patients with high-responding inhibitors under the same F8 genetic background (Inv22). An interval-time of <25.8 months was associated with increased ITI success and reduced time to success.

Low-dose immune tolerance induction therapy in severe hemophilia a children in China: Starting earlier resulted in better inhibitor eradication outcomes

BACKGROUND

Shorter interval-time from inhibitor detection to starting immune tolerance induction (ITI) might predict better ITI outcomes for severe Hemophilia A (SHA) patients with high-risk-inhibitors. However, the prediction-impact of interval-time for these patients on low-dose ITI strategy remained unclear.

OBJECTIVES

To explore the relationship between interval-time and low-dose ITI outcomes in Chinese SHA children with high-risk-inhibitors.

METHODS

This was a single-center, retrospective study on SHA children with high-risk-inhibitors (each with immediate pre-ITI inhibitor titer>10 Bethesda Units/mL) undergoing low-dose ITI strategy for ≥24 months. ITI outcomes and their predictive factors were evaluated at the 24th month treatment for each patient. The predictive ability of interval-time on ITI success was determined using receiver operating characteristic (ROC) curve.

RESULTS

Among 47 patients investigated, 34 (72.3 %) achieved success. Independent predictor for ITI-outcome on multivariate analysis included the interval-time (p = 0.007) and peak inhibitor-titer (p = 0.011). Shorter interval-time predicted ITI success [cut-off value = 22.3 months, area under ROC-curve (AUC) = 0.701] and early-ITI success within 12 month (cut-off value = 9.4 months AUC = 0.704). Linear regression analysis suggested each month interval-time delay delayed success by 0.1552 month. Unlike the interval-time, peak inhibitor-titer had no success-predictive value in high-peak inhibitor-titer patients on ITI with immunosuppressants.

CONCLUSIONS

Interval-time represented a strong predictive value for outcomes in our low-dose ITI strategy for SHA patients with high-risk-inhibitors. Shorter interval-time was associated with higher success rate and earlier success achievement. The respective interval-time cut-off values were 22.3 months for ITI success and 9.4 months for early-success.

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.

Management of haemophilia A with inhibitors: A regional cross-talk

INTRODUCTION

The development of inhibitors with factor VIII (FVIII) replacement therapy is one of the most common and challenging complications of haemophilia A (HA) treatment, jeopardising treatment efficacy and predisposing patients to high risks of morbidity and mortality. The management of patients with inhibitors is particularly challenging in countries where resources are limited.

AIM

To provide a comprehensive summary of the management of HA with inhibitors while focusing on differences in practice between Western and non-Western countries and how resource scarcity can impact HA management, leading to suboptimal outcomes in patients with inhibitors.

METHODS

Summary of key evidence and regional expert opinion.

RESULTS

We address, particularly, the diagnosis of and testing for inhibitors, as well as the epidemiology of inhibitors, including incidence, prevalence and disease burden. Secondly, we provide an overview of the current treatment landscape in HA with inhibitors regarding the eradication of inhibitors with immune tolerance induction and the treatment and prevention of bleeding with bypassing agents, non-factor replacement agents and other experimental therapies. This is complemented with insights from the authors around the applicability of, and challenges associated with, such therapies in their settings of practice.

CONCLUSIONS

We conclude by proposing some key steps towards bridging the gaps in the management of HA with inhibitors in resource-limited countries, including: (1) the collection of quality data that can inform healthcare reforms and policies; (2) improving disease knowledge among healthcare practitioners and patients with the aim of standardising disease management across centres and (3) working towards promoting equal access to HA care and therapies for everyone.

Time between inhibitor detection and start of immune tolerance induction: Association with outcome in the BrazIT study

BACKGROUND

Immune tolerance induction (ITI) is the treatment of choice for eradication of anti-factor VIII (FVIII) neutralizing alloantibodies (inhibitors) in people with inherited hemophilia A and high-responding inhibitor (PwHA-HRi). The association between ITI outcome and time elapsed between inhibitor detection and start of ITI (∆tinhi-ITI ) is debatable.

OBJECTIVE

The aim of this study was to evaluate this association among a large cohort of severe PwHA-HRi.

METHODS

Severe (factor VIII activity level <1%) PwHA-HRi on ITI (n = 142) were enrolled in 15 hemophilia treatment centers. PwHA-HRi were treated according to the Brazilian ITI Protocol. ITI outcomes were defined as success (i.e., recovered responsiveness to exogenous FVIII) and failure (i.e., no responsiveness to exogenous FVIII and requirement of bypassing agents to control bleeding).

RESULTS

Median ages at inhibitor detection and at ITI start were 3.2 years (interquartile range [IQR], 1.6-8.1) and 6.9 years [IQR, 2.6-20.1), respectively. PwHA-HRi were stratified according to ∆tinhi-ITI quartiles: first (0.0-0.6 year), second (>0.6-1.7 year), third (>1.7-9.2 years), and fourth quartile (>9.2-24.5 years). The overall success rate was 65.5% (93/142), with no difference among first, second, third, and fourth quartiles (62.9%, 69.4%, 58.3%, and 71.4%, respectively) even after adjusting the analyses for potential confounders.

CONCLUSION

In conclusion, delayed ITI start is not associated with failure of ITI in PwHA-HRi. Therefore, ITI should be offered for these patients, regardless of the time elapsed between the detection of inhibitor and the ITI start.

Low-dose immune tolerance induction in children with severe hemophilia A with high-titer inhibitors: Type of factor 8 mutation and outcomes

Background

No studies evaluated the role of F8 mutations in outcomes for low-dose immune tolerance induction (ITI) in people with severe hemophilia A (SHA) with high-titer inhibitors.

Objectives

To explore the association between F8 mutation types and low-dose ITI outcomes in children with SHA with high-titer inhibitors.

Methods

Children SHA with high-titer inhibitors who received low-dose ITI therapy at least for 1 year were included in this study. Based on the risk of inhibitor development, F8 mutations were classified into a high-risk group and a non-high-risk group. Rapid tolerance and the final ITI outcomes were assessed at the 12th and 24th month of treatment, respectively, and the predictor of outcomes was analyzed.

Results

Of 104 children included, 101 had F8 mutations identified. The children with non-high-risk mutations presented a higher rate of rapid tolerance than those with high-risk mutations (61.0% vs. 29.2%; p = 0.006). Among 72 children beyond 24 months of ITI, 55 children (76.4%) achieved success, 3 (4.2%) achieved partial success, and 14 (19.4%) failed. The children in the non-high-risk group showed a higher success rate (86.8% vs. 43.8%; p = 0.001) and a shorter time to success (mean time, 9.3 months vs. 13.2 months; p = 0.04) compared to those in the high-risk group. In multivariable logistic regression, F8 mutations were an independent predictor of ITI success (non-high-risk group vs. high-risk group, adjusted odds ratio [OR], 20.3; 95% confidence interval [CI], 3.5-117.8), as was the interval from inhibitor diagnosis to ITI start (adjusted OR, 0.95; 95% CI, 0.90-0.99). They remained the significant predictors when success time was taken into account in a Cox model.

Conclusions

Types of F8 mutation were a key predictor of outcomes for low-dose ITI in children with SHA with high-titer inhibitors. It can help to stratify the prognosis and guide clinical decisions.

Final Results of the Prospective ADVATE® Immune Tolerance Induction Registry (PAIR) Study with Plasma- and Albumin-Free Recombinant Factor VIII

Introduction

Neutralizing antibodies to coagulation factor VIII (FVIII) remain a major complication associated with FVIII replacement therapy.

Aim

To assess safety and efficacy of immune tolerance induction (ITI) therapy with ADVATE^® (antihemophilic factor [recombinant] [rAHF]) in patients who participated in the Prospective ADVATE Immune Tolerance Induction Registry (PAIR) study.

Methods

The PAIR study was an international, multicenter, open-label, prospective, observational study in patients with hemophilia A and inhibitors, prescribed rAHF ITI therapy in clinical practice. The primary endpoint was adverse event (AE) reporting; the secondary endpoints included incidence of central venous access device-related complications and success rates of ITI therapy. Maintenance of immune tolerance was monitored for 12 months post-ITI therapy.

Results

Of 44 patients, 36 completed ITI therapy, including 31 completing the 12-month follow-up. Most patients received rAHF 90–130 IU/kg/day (59.1%) and a mean of 6.0 doses/week; the median duration of rAHF ITI therapy during the PAIR study was 600 days. Overall, 284 AEs were reported; 56 AEs were serious, of which none were considered rAHF-related. Of 228 nonserious AEs, 14 (in six patients) were deemed rAHF-related: increase of FVIII inhibitors titer due to anamnestic response, nausea, catheter site pain, pyrexia, urticaria, upper respiratory tract infection, arthralgia, and hemarthrosis. None were severe or led to ITI discontinuation. Eighteen patients experienced ≥1 central venous access device-related complication, and 21 of 36 completers achieved a negative inhibitor titer. The Kaplan–Meier estimate of success for achievement of first negative titer at 18 months of ITI therapy was 68.3% (95% confidence interval 51.8–83.6%) among completers. Of patients with partial or complete success post-ITI, 87% (20/23) maintained immune tolerance at 12-month follow-up.

Conclusion

Data suggest that rAHF ITI therapy in the PAIR study was effective, with no unexpected safety signals reported.

Predictors of inhibitor eradication by primary immune tolerance induction in severe haemophilia A with high responding inhibitors

BACKGROUND

Immune tolerance induction (ITI) is the only proven strategy to eradicate factor VIII inhibitors in patients with haemophilia A (HA).

AIM

To identify patients and treatment options with the highest chance of inhibitor eradication by primary ITI.

PATIENTS AND METHODS

In the frame of the Italian ITI Registry, carried out from 1995 to 2015 (last follow-up 2018), 137 primary ITI courses in severe HA patients (90/137 with poor prognosis) were analysed for predictors of outcome (complete/partial response or failure). Sixty-six of them (48%) were prospectively evaluated.

RESULTS

ITI was successful in 91/137 patients (66.4%) and 70 (51.1%) achieved complete response within 11 months (median). Historical peak titres ≤200 BU/ml (P = .033), inhibitor titres ≤5 BU/ml at ITI start (P = .001), peak titres ≤100 BU/ml during ITI (P < .001) and missense mutations and small insertions/deletions of FVIII gene (P = .027) predicted complete inhibitor eradication. A score that considers the cumulative number of these variables predicted complete response with positive predictive values up to .81 at ITI start and .91 during ITI, respectively. Patients who had no bleeding (OR, 3.45, 95% CI: 1.4-8.6) nor other adverse events (OR 2.6, 95%CI: 1.3-5.3) during ITI had higher chances of complete response. During the 120-month follow-up (median), 2/70 patients who had achieved complete response relapsed (2.9%).

CONCLUSIONS

This Registry, with a centralized review of outcomes, homogeneous data collection (half of which prospective) and long-term follow-up, provides insights for optimizing ITI, with a rationale for further studies in the currently evolving scenario of inhibitor management in HA patients.

Haemophilia

Haemophilia A and B are rare congenital, recessive X-linked disorders caused by lack or deficiency of clotting factor VIII (FVIII) or IX (FIX), respectively. The severity of the disease depends on the reduction of levels of FVIII or FIX, which are determined by the type of the causative mutation in the genes encoding the factors (F8 and F9, respectively). The hallmark clinical characteristic, especially in untreated severe forms, is bleeding (spontaneous or after trauma) into major joints such as ankles, knees and elbows, which can result in the development of arthropathy. Intracranial bleeds and bleeds into internal organs may be life-threatening. The median life expectancy was ~30 years until the 1960s, but improved understanding of the disorder and development of efficacious therapy based on prophylactic replacement of the missing factor has caused a paradigm shift, and today individuals with haemophilia can look forward to a virtually normal life expectancy and quality of life. Nevertheless, the potential development of inhibitory antibodies to infused factor is still a major hurdle to overcome in a substantial proportion of patients. Finally, gene therapy for both types of haemophilia has progressed remarkably and could soon become a reality.

The B-Natural study-The outcome of immune tolerance induction therapy in patients with severe haemophilia B

INTRODUCTION

Inhibitors develop less frequently in haemophilia B (HB) than haemophilia A (HA). However, when present, the success of tolerization by immune tolerance induction (ITI) therapy is lower and the risk of complications higher.

AIM

To evaluate the use and outcome of ITI in patients with HB and inhibitors.

METHODS

Subjects include singletons or siblings with a current/history of inhibitors enrolled in B-Natural-an observational study designed to increase understanding of clinical management of patients with HB. Patients were followed for 6 months and information on demographics, medical and social history, and treatment were recorded.

RESULTS

Twenty-nine patients with severe HB and inhibitors were enrolled in 24 centres. Twenty-two underwent one or more courses of ITI with or without immune suppression. Eight patients (36.4%) were successfully tolerized after the first course of ITI. One of these successes (12.5%) experienced allergic manifestations, whereas the corresponding number for the 10 treatment failures was five (50%). One of seven (14.2%) patients with large deletions and three of eight (37.5%) with nonsense mutations were tolerized at the first attempt, and all patients experiencing nephrosis either failed or were on-going. At study end, 11 (50%) were considered successfully tolerized after one or more ITI courses, three were unsuccessful, and eight were still undergoing treatment.

CONCLUSION

Our data underscore the possibilities and difficulties of achieving tolerization in patients with HB with inhibitors. The type of mutation and complications appear to correlate with ITI outcome, but more accurate definitions of successful ITI are warranted.

Origins, Development, Current Challenges and Future Directions with Activated Prothrombin Complex Concentrate for the Treatment of Patients with Congenital Haemophilia with Inhibitors

Congenital haemophilia A (HA) is caused by deficiency of coagulation factor VIII (FVIII) activity, leading to spontaneous or traumatic bleeding events. While FVIII replacement therapy can treat and prevent bleeds, approximately 30% of patients with severe HA develop inhibitor antibodies that render FVIII replacement therapy ineffective. The bypassing agents (BPAs), activated prothrombin complex concentrate (aPCC) and recombinant activated FVII, first approved in 1977 and 1996, respectively, act to generate thrombin independent of pathways that involve factors IX and VIII. Both may be used in patients with congenital haemophilia and inhibitors (PwHIs) for the treatment and prevention of acute bleeds and quickly became standard of care. However, individual patients respond differently to different agents. While both agents are approved for on-demand treatment and perioperative management for patients with congenital haemophilia with inhibitors, aPCC is currently the only BPA approved worldwide for prophylaxis in PwHI. Non-factor therapies (NFTs) have a mechanism of action distinct from BPAs and have reported higher efficacy rates as prophylactic regimens. Nonetheless, treatment challenges remain with NFTs, particularly regarding the potential for synergistic action on thrombin generation with concomitant use of other haemostatic agents, such as BPAs, for the treatment of breakthrough bleeds and in perioperative management. Concomitant use of NFTs with other haemostatic agents could increase the risk of adverse events such as thromboembolic events or thrombotic microangiopathy. This review focuses on the origins, development and on-going role of aPCC in the evolving treatment landscape in the management of PwHI.

Low-dose immune tolerance induction for children with hemophilia A with poor-risk high-titer inhibitors: A pilot study in China

BACKGROUND

Immune tolerance induction (ITI) therapy is currently unaffordable in China. Management of hemophilia A children with high-titer inhibitor is therefore a challenge.

AIM

To describe the ITI strategy using plasma-derived factor VIII/von Willebrand factor concentrate (pdFVIII/VWF) +/- immunosuppression and to report its efficacy in children with hemophilia A having poor-risk status for ITI success.

METHODS

A prospective pilot study on children with hemophilia A having poor-risk status (all with at least inhibitor titer > 10 BU pre-ITI initiation). Patients received ~50 IU/kg FVIII every other day using domestic intermediate purity pdFVIII/VWF products, either alone or in combination with rituximab +/- prednisone.

RESULTS

Sixteen patients with median age 2.9 (range, 2.2-13.2) years and median pre-ITI inhibitor titer 30.7 (range, 10.4-128) BU were enrolled. Analysis at median 14.7 (range, 12.4-22.6) months' follow-up showed a total response rate of 87.5%. This included success (achieving inhibitor < 0.6 BU) in 13 patients (81.3%) in a median of 8.8 (range, 3.2-11.8) months, and partial success (achieving inhibitor < 5 BU but > 0.6BU) in 1 (6.3%). Compared to the pre-ITI period, the mean bleeds/month during ITI was 0.51 (64.0% reduction), and joint bleeds/month was 0.34 (64.3% reduction). This low-dose ITI strategy cost less by 70% to 87% than that for the high-dose FVIII regimen. No severe adverse events were observed.

CONCLUSION

This low-dose ITI strategy of pdFVIII/VWF +/- immunosuppression achieved relatively satisfactory outcomes in children with hemophilia A inhibitor having poor-risk status. This low-dose regimen showed economic advantages and is therefore suitable for using in China. However, further study in a larger cohort with a longer follow-up time is needed.

Hemophilia A with inhibitor: Immune tolerance induction (ITI) in the mirror of time

Inhibitor (neutralizing antibodies) development remains the most significant complication in patients with severe congenital hemophilia A receiving exogenous factor VIII (FVIII). Although our understanding of the pathophysiology of inhibitor development has advanced, the knowledge gained has not yet translated into a robust decline in incidence, with the overall risk remaining at ∼30%. Immune Tolerance Induction (ITI) is the only current method to successfully eradicate an inhibitor and achieve long-term tolerance. Although current practice utilizes a wide variety of ITI regimens, identification of an optimal regimen has not emerged. Over the last decade, the number of replacement products available in hemophilia has greatly expanded. The cumulative evidence with each product for use in ITI is often lacking. Most recently emicizumab, a humanized monoclonal bi-specific antibody that substitutes for the scaffolding effect of FVIIIa was approved; this agent prevents bleeding in both inhibitor and non-inhibitor patients. The use of emicizumab will bring about a new era in care that will require clinicians to challenge current practice paradigms including use and administration of ITI. This review will summarize the main clinical ITI data and practices for patients with severe congenital hemophilia A with inhibitors (CHAwI) over the last four decades and will highlight current studies in the field, with attention to open questions.

The changing face of immune tolerance induction in haemophilia A with the advent of emicizumab

INTRODUCTION

As a result of the new treatment paradigm that the haemophilia community will face with the availability of novel (non-factor) therapies, an updated consensus on ITI recommendations and inhibitor management strategies is needed.

AIM

The Future of Immunotolerance Treatment (FIT) group was established to contemplate, determine and recommend the best management options for patients with haemophilia A and inhibitors.

DISCUSSION AND CONCLUSIONS

Despite the considerable success of emicizumab in the management of inhibitor patients, the FIT group still sees the importance of eradicating inhibitors. However, the availability of emicizumab and other non-factor therapies in the future might impact greatly on how ITI is undertaken. Theoretically, concomitant use of emicizumab and FVIII might allow emicizumab to effectively prevent bleeding with lower dose ITI regimens. This might allow for the greater adoption of low-dose/low-frequency FVIII ITI regimens, which may result in a reduced need for central venous access devices while still maintaining a reasonable likelihood of ITI success. The FIT group proposes a new management algorithm for current ITI (without emicizumab) and a hypothetical new approach with the availability of emicizumab. As there are no published data regarding the concomitant use of emicizumab and FVIII for ITI, the FIT Expert group encourages the undertaking of properly conducted prospective studies to explore these approaches further.

Inhibitors: A Need for Eradication?

The development of inhibitors against factor VIII (FVIII) concentrates represents a significant treatment complication for hemophilia. Immune tolerance induction (ITI) therapy eradicates inhibitors in 60-80% of patients, resulting in a normal FVIII response. This article, based on presentations at the 6th International Coagulation Meeting, held in Barcelona, Spain, in September 2017, provides an overview of management approaches for patients with inhibitors and briefly tabulates four cases of ITI therapy (first-line or rescue ITI therapy in pediatric and adult patients) with successful outcomes. Switching FVIII product from recombinant FVIII to plasma-derived FVIII/VWF concentrate may be helpful in eradicating inhibitors. The rate of decline of inhibitor titer in the initial stages of ITI therapy is a good indicator of the success or failure of therapy, although prognostic biomarkers are needed. The development of the bispecific monoclonal antibody emicizumab, which was recently shown to reduce bleeding in inhibitor patients, offers a potential alternative therapeutic option. However, the benefits of inhibitor eradication, including a wider choice of cheaper therapeutic products for preventing and treating bleeds, suggest that at least one attempt of ITI therapy should be offered to patients who develop inhibitors.

Inhibitors in haemophilia A and B: Management of bleeds, inhibitor eradication and strategies for difficult-to-treat patients

The standard therapy for patients with haemophilia is prophylactic treatment with replacement factor VIII (FVIII) or factor IX (FIX). Patients who develop inhibitors against FVIII/FIX face an increased risk of bleeding, and the likelihood of early development of progressive arthropathy, alongside higher treatment-related costs. Bypassing agents can be used to prevent and control bleeding, as well as the recently licensed prophylaxis, emicizumab, but their efficacy is less predictable than that of factor replacement therapy. Antibody eradication, by way of immune tolerance induction (ITI), is still the preferred management strategy for treating patients with inhibitors. This approach is successful in most patients, but some are difficult to tolerise and/or are unresponsive to ITI, and they represent the most complicated patients to treat. However, there are limited clinical data and guidelines available to help guide physicians in formulating the next treatment steps in these patients. This review summarises currently available treatment options for patients with inhibitors, focussing on ITI regimens and those ITI strategies that may be used in difficult-to-treat patients. Some alternative, non-ITI approaches for inhibitor management, are also proposed.

Optimizing bleed prevention throughout the lifespan: Womb to Tomb

The focus of care providers, patients and families is the ability to tailor care for persons with haemophilia (PWH) across the lifespan. Care requires knowledge of the bleeding disorder and age-related complications, risk of therapeutic interventions, and evaluation of individual characteristics that contribute to outcomes. The ultimate goal is to live a normal life without the burden of bleeding, for PWH and carriers. A wide range of therapeutic options is required to achieve personalized care. Over the last decade, substantial therapeutic advantages have been achieved in the treatment of haemophilia that include the development of a robust array of factor concentrates, novel haemostatic agents, and increased knowledge and awareness of disease associated outcomes and risk factors. Significant strides on the road to accessible gene therapy have been realized. This increased range of therapeutic modalities provides options for development and implementation of care plans for each patient at each stage of life that are more flexible compared to prior care regimens. Paradigms for management of haemophilia are changing. As a community, we must work together to use these resources wisely, to learn from outcomes with new therapies and diagnostic tools, to assure all patients can achieve improved care and outcomes regardless of disease state or country of origin.

Recombinant factor VIII Fc fusion protein for immune tolerance induction in patients with severe haemophilia A with inhibitors-A retrospective analysis

INTRODUCTION

Immune tolerance induction (ITI) is the gold standard for eradication of factor VIII inhibitors in severe haemophilia A; however, it usually requires treatment for extended periods with associated high burden on patients and healthcare resources.

AIM

Review outcomes of ITI with recombinant factor VIII Fc fusion protein (rFVIIIFc) in patients with severe haemophilia A and high-titre inhibitors.

METHODS

Multicentre retrospective chart review of severe haemophilia A patients treated with rFVIIIFc for ITI.

RESULTS

Of 19 patients, 7 were first-time ITI and 12 were rescue ITI. Of 7 first-time patients, 6 had at least 1 high-risk feature for ITI failure. Four of 7 first-time patients were tolerized in a median of 7.8 months. The remaining 3 patients continue on rFVIIIFc ITI. Of 12 rescue patients, 7 initially achieved a negative Bethesda titre (≤0.6) in a median of 3.3 months, 1 had a decrease in Bethesda titre and continues on rFVIIIFc ITI and 4 have not demonstrated a decrease in Bethesda titre. Of these 4, 3 continue on rFVIIIFc ITI and 1 switched to bypass therapy alone. Two initially responsive patients transitioned to other factors due to recurrence. Overall, 16 of 19 patients remain on rFVIIIFc (prophylaxis or ITI). For those still undergoing ITI, longer follow-up is needed to determine final outcomes. No adverse events reported.

CONCLUSIONS

Recombinant factor VIII Fc fusion protein demonstrated rapid time to tolerization in high-risk first-time ITI patients. For rescue ITI, rFVIIIFc showed therapeutic benefit in some patients who previously failed ITI with other products. These findings highlight the need to further evaluate the use of rFVIIIFc for ITI.

Partnering to change the world for people with haemophilia: 7th Haemophilia Global Summit, Madrid, Spain 22-24 September 2016

The 7th Haemophilia Global Summit was held in Madrid, Spain, in September 2016. With a programme designed, for the 6th consecutive year, by a Scientific Steering Committee of haemophilia experts, the aim of the summit was to share optimal management strategies for haemophilia at all life stages and to provide an opportunity for specialists from across the haemophilia multidisciplinary care team to engage in discussion and debate with leading international experts on current and future areas of research. Topics covered ranged from the optimisation of haemophilia management, emerging issues in clinical care, practical approaches and future perspectives, in addition to patient engagement and empowerment in modern haemophilia care.

Evolution of the Treatments for Hemophilia

Although hemophilia has been recognized for centuries as an inherited disorder primarily affecting males, advances in treatments have been very recent. Initial availability of plasma-derived therapies offered significant improvements in morbidity and mortality, but the transmission of viruses quickly negated the benefit of early factor replacement products. After developing successful viral inactivation methods and subsequently developing recombinant technology, the manufacturing of factor concentrates became much safer. Access to safer factor products allowed for a shift from the treatment of bleeds to prevention, called prophylaxis. Although dosing and interval vary, prevention of joint disease is now a realistic goal. Unfortunately, despite advances in the safety of therapy, some patients are unable to use factor replacement products because they develop antibodies, known as inhibitors. Eradication of inhibitors is possible in the majority of patients, but it is expensive and takes time. Management of acute bleeding may require significantly higher doses of factor replacement or the use of a bypassing agent. As a result, patients with inhibitors are at increased risk for sequelae, including joint disease, life-threatening bleeding, infectious complications with central vascular access devices, and thrombotic complications.

Estimating the potential cost of a high dose immune tolerance induction (ITI) therapy relative to the cost of a combined therapy of a low dose ITI therapy with bypassing agent prophylaxis

INTRODUCTION

The International Immune Tolerance Study (I-ITI) demonstrated comparable success rates between low (FVIII 50 IU/kg/TIW) and high dose (FVIII 200 IU/kg/day) regimens. While costlier, the high dose ITI regimen achieved shorter time-to-treatment success with fewer bleeding episodes compared to the low dose ITI regimen. Adding bypassing agent prophylaxis (BAP) to a low dose ITI regimen may reduce bleeding while still being less costly than high dose ITI.

AIM AND METHODS

An economic model was developed to compare high dose ITI to low dose ITI with BAP. All model inputs were derived from clinical trials. The I-ITI study indicated a median time to negative inhibitor titre of 4.6 and 9.2 months and average number of bleeds/patient of 4.2 and 9.9 for the high and low dose regimens respectively. Based on the BAP trials, aPCC (85 U/kg/TIW) and rFVIIa (90 μg/kg/day) achieved a 62% and 45% reduction in bleeding frequency respectively. Cost analysis was from a US third party payer perspective and limited to drug costs. One-way, two-way and probabilistic sensitivity analyses were performed.

RESULTS

Costs of low dose ITI with aPCC prophylaxis until negative inhibitor titre is achieved was 24.0% less compared to high dose ITI. Low dose ITI with rFVIIa prophylaxis cost 46.5% more compared to high dose ITI. Model results were robust in the majority of the sensitivity analyses.

CONCLUSION

A low dose ITI regimen with aPCC prophylaxis may be cost saving compared to a high dose ITI regimen with the potential to reduce morbidity by lowering the risk for breakthrough bleeds.

Successful immune tolerance induction using turoctocog alfa in an adult haemophilia A patient

We present here the first known case of successful immune tolerance induction (ITI) using recombinant factor VIII (rFVIII), turoctocog alfa, in a patient with severe haemophilia A. The 38-year-old patient with a long-standing inhibitor required urgent surgery for severe arthropathy. rFVIII was administered throughout the surgical period. Surgery was considered successful, but on day 7 after surgery, an increased level of FVIII inhibitors were detected. ITI was attempted immediately thereafter according to the Bonn protocol. Inhibitors were no longer detected on day 17; 13 months later, successful ITI was achieved. This case suggests that a long-time interval between inhibitor appearance and the start of ITI therapy may not necessarily indicate poor prognosis.

Achievements, challenges and unmet needs for haemophilia patients with inhibitors: Report from a symposium in Paris, France on 20 November 2014

Over the past 20 years, there have been many advances in haemophilia treatment that have allowed patients to take greater control of their disease. However, the development of factor VIII (FVIII) inhibitors is the greatest complication of the disease and a challenge in the treatment of haemophilia making management of bleeding episodes difficult and surgical procedures very challenging. A meeting to discuss the unmet needs of haemophilia patients with inhibitors was held in Paris on 20 November 2014. Topics discussed were genetic and non-genetic risk factors for the development of inhibitors, immunological aspects of inhibitor development, FVIII products and inhibitor development, generation and functional properties of engineered antigen-specific T regulatory cells, suppression of immune responses to FVIII, prophylaxis in haemophilia patients with inhibitors, epitope mapping of FVIII inhibitors, current controversies in immune tolerance induction therapy, surgery in haemophilia patients with inhibitors and future perspectives for the treatment of haemophilia patients with inhibitors. A summary of the key points discussed is presented in this paper.

Long-term course of anti-factor VIII antibody in patients with hemophilia A at a single center

Background

Immune tolerance induction (ITI) can reduce inhibitors against factor VIII concentrates by 70-80%. In this study, we elucidated the characteristics of inhibitors and attempted to determine the proper indications and timing for ITI.

Methods

Subjects included hemophilia A patients registered at the Korea Hemophilia Foundation from 1991 through 2014. Inhibitors were classified as persistent and transient. Patients were classified into groups according to peak inhibitor titer: low (<2 BU/mL), moderate (2 to <5 BU/mL), high (5 to <10 BU/mL), and very high titer (≥10 BU/mL).

Results

Overall, 350 (21.4%) of 1,634 hemophilia A patients developed inhibitors at least once. Of these, 100 (6.1%) and 250 (15.3%) patients developed persistent and transient inhibitors, respectively. For transient inhibitors, the median peak titer was 1.0 BU/mL, persistent for median of 11.0 months (10.0, 8.0, 13.0, and 19.0 months in the low, moderate, high, and very high titer transient inhibitor groups, respectively). Overall, 95.8% (215), 72.2% (17), 52.4% (21), and 21.7% (97) of patients in the low, moderate, high, and very high titer groups became inhibitor-negative spontaneously, without ITI.

Conclusion

Given the spontaneous disappearance of inhibitors and high cost of ITI, it is worthwhile to postpone ITI for 11 months unless the peak inhibitor titer is greater than 10 BU/mL.