Experience with a third generation recombinant factor VIII concentrate (Advate) for immune tolerance induction in patients with haemophilia A

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.

An update of the current pharmacotherapeutic armamentarium for hemophilia A

INTRODUCTION

For several decades, we have seen unprecedented advances in novel therapy development for hemophilia A. These advances address the unmet need of replacement therapy, and they include the development of recombinant products with improved pharmacokinetics, subcutaneously administered products, and those with better efficacy and safety profiles in hemophilia A management.

AREAS COVERED

In this update of hemophilia A treatment, the author summarizes data from completed standard half-life FVIII products, extended half-life FVIII products and FVIII mimetic studies. All products have an acceptable safety profile. The standard half-life products, EHL-FVIII products and emicizumab are efficacious in the prevention and treatment of bleeds and for EHL-FVIII in the perisurgical setting.

EXPERT OPINION

Advances in pharmacotherapy for hemophilia A have been characterized by changing care goals from supportive care to eliminating infections, preventing inhibitors, and more recently achieving zero bleeds in many patients. While gene therapy has the potential for functional cure in hemophilia A, it has many limitations which need to be addressed. Therefore, pharmacotherapy is likely to remain the mainstay in the management of hemophilia A and promises to get better with currently available therapies. Evolving factor and non-factor replacement therapies may also improve current unmet needs in hemophilia A management.

Immune tolerance induction with moroctocog-alpha (Refacto/Refacto AF) in a population of Italian haemophilia A patients with high-titre inhibitors: Data from REF.IT Registry

BACKGROUND

The appearance of inhibitors is the most serious complication in haemophilia A (HA) patients. The primary objective is their eradication. Up to date, immune tolerance induction (ITI) was the only therapeutic option to achieve this.

AIM

To assess the efficacy of moroctocog-alpha as an ITI regimen in a population of HA patients with high-titre inhibitors.

METHODS

The REF.IT Registry is a retrospective-prospective study that collected data on all patients with HA and high-titre inhibitors treated with moroctocog-alpha as an ITI regimen at twelve Italian Haemophilia Centres.

RESULTS

We enrolled 27 patients, 85.2% were children. All patients were high responders, 88.9% had severe HA. We found 69.3% of them had one or more risk factors for poor ITI prognosis, 14.8% were ITI rescue. Overall 59.3% achieved a complete/partial success (complete in 51.9%). ITI failed in 11 patients, 63.6% of them with poor-prognosis risk factors. Inhibitors appeared after a mean of 27 exposure days. Mean historical peak was 78.8 BU/mL. The primary ITIs started on average 20.2 months after the diagnosis. A partial or complete success after a mean of 15 months of treatment was achieved in 56.6% of the children while the same result was obtained by 75.0% adults after 22 months from ITI onset. Patients who were treated with high-dose moroctocog-alpha (200 UI/kg/day) were 63.0%.

CONCLUSION

Our Registry showed that the use of moroctocog-alpha in the setting of ITI was effective and safe also in a population of patients with high-titre inhibitors, presenting one or more risk factors for poor ITI prognosis.

Management of patients with long-term inhibitors: is immune tolerance an underestimated life-long solution?

Immune tolerance induction (ITI) is recognized as the first choice treatment in haemophilic patients with inhibitors, with the aim of restoring safe and effective standard factor VIII replacement and, particularly, prophylaxis in children. For the latter, literature data and clinical practice support the optimal cost utility ratio of ITI. Indeed, the high success rate, the low incidence of inhibitor recurrence after successful ITI and the possibility of preventing joint deterioration, enable one to predict a considerable long-term reduction of costs in the majority of treated patients. Therefore, in spite of high costs and open issues about optimal regimens, ITI is actually attempted in virtually all children with inhibitors. Few patients with long-standing inhibitors presently undergo ITI, particularly in the case of severe bleeding tendency. In this setting, uncertainties concerning management are amplified by the paucity of literature data and psychological reluctance by both patients and treaters due to the perceived poor prognosis and the demanding treatment (also in terms of costs). However, clinical data suggest that the role of age at ITI start and of time interval from inhibitor diagnosis, as predictors of ITI outcome, should be considered in a larger framework of proposed and more established prognostic factors. Moreover, optimising ITI management, particularly with respect to inhibitor titre at ITI start and avoidance of adverse events or interruption of treatment, may also contribute to improve outcomes. Although the economic constraints of the present era significantly affect resources for such a high-cost treatment, the individual cost-utility ratio (bleeding tendency and risk of fatal bleeding, arthropathy and need for orthopaedic surgery, comorbidities, quality of life) should be assessed carefully to determine whether ITI is a suitable option and thus not preclude adults from the opportunity of inhibitor eradication.

Immune tolerance induction in haemophilia A patients with inhibitors by treatment with recombinant factor VIII: a retrospective non-interventional study

Immune tolerance induction (ITI) can overcome inhibitory factor VIII (FVIII) antibodies in haemophilia A patients receiving FVIII replacement therapy. The objective was to evaluate the use of sucrose-formulated, full-length recombinant FVIII (rFVIII-FS) for ITI therapy. Patients (<8 years at ITI start) with severe haemophilia A and a peak inhibitor titre >5 Bethesda units (BU) who underwent ITI with any rFVIII-FS dose for ≥ 9 months (or until success) were eligible for this retrospective study. Efficacy analyses included descriptions of ITI treatment regimens and outcomes; ITI success was determined solely at the discretion of the investigator. Safety analyses included assessment of adverse events. Of 51 enrolled patients, 32 [high dose (≥ 85 IU kg(-1) day(-1)), n = 21; low dose, n = 11] were eligible for analysis. ITI was successful in 69% (22/32) of patients (high dose, 66.7%; low dose, 72.7%) after a median of 1.4 years (range, 0.1-3.6 years). Influencing factors for ITI success were start of ITI <1 year after inhibitor detection and an inhibitor titre <10 BU at ITI start. All patients successfully tolerized with ITI continued to receive rFVIII-FS prophylaxis as maintenance therapy, with no inhibitor recurrence from the end of ITI until study enrolment. Use of rFVIII-FS for ITI was effective and well tolerated; success rates were similar to those in published studies.

Immune tolerance induction for patients with severe hemophilia A: a critical literature review

The development of inhibitors that neutralize the function of clotting factor VIII (FVIII) is currently the most challenging complication associated with the treatment of hemophilia A as it increases the disease-related morbidity and mortality. Immune tolerance induction (ITI) is the only documented strategy to eradicate persistent inhibitors in severe hemophilia A patients. Several studies have been conducted so far to identify patient- and treatment-related factors associated with greater ITI success. The currently available literature on ITI in hemophilia A will be critically reviewed in this article. In particular, we will focus on the role of the type of FVIII product on ITI outcome by analyzing the clinical and experimental data.

Phenotypic correction of hemophilia A in sheep by postnatal intraperitoneal transplantation of FVIII-expressing MSC

We recently re-established a line of sheep that accurately mimics the clinical symptoms and genetics of severe hemophilia A (HA). Here, we tested a novel, nonablative transplantation therapy in two pediatric HA animals. Paternal mesenchymal stem cells (MSC) were transduced with a porcine FVIII-encoding lentivector and transplanted via the intraperitoneal route without preconditioning. At the time of transplantation, these animals had received multiple human FVIII treatments for various spontaneous bleeds and had developed debilitating hemarthroses, which produced severe defects in posture and gait. Transplantation of transduced MSC resolved all existent hemarthroses, and spontaneous bleeds ceased. Damaged joints recovered fully; the animals regained normal posture and gait and resumed normal activity. Despite achieving factor-independence, a sharp rise in pre-existent Bethesda titers occurred following transplantation, decreasing the effectiveness and duration of therapy. Postmortem examination revealed widespread engraftment, with MSC present within the lung, liver, intestine, and thymus, but particularly within joints affected at the time of transplantation, suggesting MSC homed to sites of ongoing injury/inflammation to release FVIII, explaining the dramatic improvement in hemarthrotic joints. In summary, this novel, nonablative MSC transplantation was straightforward, safe, and converted life-threatening, debilitating HA to a moderate phenotype in a large animal model.