Induction of immune tolerance with recombinant factor VIII in haemophilia A patients with inhibitors

We report on 11 patients (nine unrelated and a brother pair) with severe haemophilia A and factor VIII (FVIII) inhibitor, in whom immune tolerance (IIT) was induced with recombinant FVIII (r-FVIII). Their age ranged from 11 months to 47 years. The number of exposure days (ED) at inhibitor detection varied from 11 to 130. Nine of the 11 patients were high responders [>10 Bethesda units (BU)] with peak inhibitor levels ranging from 10 to 566 BU. The other two were low responders with peak levels between 0.7 and 2 BU. Before inhibitor detection, the patients had been receiving products of various purities. The IIT regimens were very heterogeneous, and the treatment schedule varied from a short period with 50 IU kg^–1 every 2 days, followed by 100 IU kg^–1 every 2 days and then 220 IU kg^–1 daily. The outcome was considered successful when the inhibitor level fell to 0.6 BU or lower after IIT treatment. The outcome overall was successful in nine out of 11 patients (81.8%), with the nine successful cases comprising seven of the nine high responders (77.8%) and the two low responders. Definite failure of IIT was observed in one high responder after two different IIT regimens. A second high responder is still on IIT treatment. All patients in whom IIT was successful are currently receiving r-FVIII on demand or prophylactically at various dosages. Despite the variability of the patient characteristics and the IIT schedules, this study demonstrates that r-FVIII represents an effective alternative for the eradication of inhibitors through IIT.     

Efficacy and inhibitor development in previously treated patients with haemophilia A switched to a B domain-deleted recombinant factor VIII

There have been recent reports of unexpected poor efficacy of a B-domain-deleted recombinant factor VIII (BDD-rFVIII) in haemophiliacs, and inhibitor development in previously treated patients (PTPs) switched to BDD-rFVIII. The results of a 6-month prospective study of 25 PTPs and of a retrospective survey of 94 PTPs, all switched to BDD-rFVIII, were used to evaluate efficacy and inhibitor development. The prospective study showed that 89% of 362 bleeds were controlled by one to two infusions, reproducing the efficacy profiles of other recombinant products (rFVIIIs). One patient, previously treated with plasma-derived FVIII only, developed a high titre inhibitor (30 BU) after 5 days of exposure. The retrospective survey, carried out in the total Italian PTP population switched to BDD-rFVIII, involved 19 PTPs at higher inhibitor risk due to previous exposure of < or = 50 days and 75 PTPs at lower inhibitor risk due to previous exposure of > 50 days. One patient developed an inhibitor: he was a high-risk, severe PTP previously exposed to another rFVIII for 3 days only. Among the entire low-risk population of severe Italian PTPs switched to BDD-rFVIII (25 in the prospective study, 49 in the retrospective cohort) only one developed an inhibitor (1.3%). These data indirectly support the views that BDD-rFVIII is equivalent to other rFVIIIs in term of efficacy and inhibitor development.     

Safety and efficacy of a sucrose-formulated recombinant factor VIII product for the treatment of previously treated patients with haemophilia A in China

The use of plasma-derived products has contributed to a high rate of blood-borne infections among haemophilia patients in China. Recombinant factor VIII (rFVIII) products that are manufactured without human or bovine albumin and include dedicated viral inactivation steps, hold a significant safety advantage over plasma products. However, there is little information published on the use of rFVIII products in non-caucasian populations. This is the first reported evaluation of the efficacy and safety of a rFVIII product in Chinese haemophiliacs. An open-label, non-randomized, prospective, multicentre trial enroled previously treated Chinese patients with haemophilia A. All treatments were administered using a sucrose-formulated rFVIII-FS (Kogenate((R))). Forty-nine patients received totals of 291 infusions (mean, 5.94/patient) and 742 140 IU rFVIII-FS (mean, 2550.3 IU/infusion). Of the 60 acute bleeding episodes that were treated, 90% were successfully managed with only one (81.7%) infusion or two (8.3%) infusions. Physicians reported haemostasis control for acute bleeds to be 'Excellent' or 'Improved' with rFVIII-FS therapy. No FVIII inhibitors were detected in any patient. Only one treatment-related adverse event was reported, which was mild dizziness that resolved spontaneously. rFVIII-FS was efficacious, safe and well tolerated in the treatment of previously treated patients with haemophilia A in China.     

Continuous infusion of recombinant factor VIII formulated with sucrose in surgery: Non‐interventional,observational study in patients with severe haemophilia A

In haemophilia A, continuous infusion (CI) of FVIII perioperatively provides a more constant FVIII level than conventional bolus injections, avoiding low trough levels that could increase bleeding risk. Due to the low number of surgical cases in clinical trials, especially in haemophilia, more information on the clinical practice of CI from observational studies is helpful. We aimed to evaluate the effectiveness and safety of CI with recombinant factor VIII formulated with sucrose (rFVIII‐FS) in a typical surgery practice setting. This was a non‐interventional study in 12 centres. Patients with severe haemophilia A who received rFVIII‐FS by CI during and after surgery were included in this study if they had more than 150 exposure days (EDs) to any FVIII product and had no history of inhibitors before CI. Patients were observed during the entire course of CI, with monitoring up to 3 months thereafter. Twenty‐five patients with 28 surgeries were included in the analysis. Median age was 51.7 (range 10–75). Most (75%; 21/25) patients underwent orthopaedic surgeries. The median dose of rFVIII‐FS consumed during CI was 376 IU kg^?1 (range 157.9–3605.6 IU kg^?1) with a greater median dose for orthopaedic surgeries (424.0 IU kg^?1) compared to non‐orthopaedic surgeries (278.5 IU kg^?1). 95% of all FVIII measurements (214/224) were on target. Efficacy and tolerability were rated as good/excellent in 89.3% (25/28) of surgeries. No inhibitors were observed during or after surgery. This study demonstrates the effectiveness of CI with rFVIII‐FS during surgery in patients with severe haemophilia A in a clinical practice setting.     

Incidence of inhibitors in haemophilia A patients – a review of recent studies of recombinant and plasma-derived factor VIII concentrates

The development of inhibitors to factor VIII or IX is the most serious complication of haemophilia therapy. While early surveys revealed inhibitor prevalences of 3.6-25%, recent studies, especially those using recombinant DNA-derived products, have prompted speculation as to whether ultrapurified products may cause a higher incidence of inhibitors. Although studies of ultrapure rFVIII in previously treated patients have not shown an increased inhibitor risk, in previously untreated patients (PUPs) with severe haemophilia A (factor VIII < 2%), cumulative incidences of approximately 30% have been reported. The majority of these inhibitors are low responders; many have disappeared spontaneously despite continued treatment with the study product (i.e. transient inhibitors), and were most probably detected as a consequence of frequent inhibitor testing. The mutation causing haemophilia has recently been shown to be a significant risk factor for developing an inhibitor; mutations leading to the absence of endogenous factor VIII protein (for example, large multidomain deletions, nonsense mutations, isochromosomal intron 22 inversions) are associated with the highest risk of inhibitor development. Furthermore, recent prospective studies of plasma-derived products reveal inhibitor incidences (i.e. 21-52%) that are comparable to those obtained with recombinant products. When comparing the incidences of high-responder inhibitors (> 10 BU) among recent prospectively studied severe haemophilia A cohorts (i.e. 11-41%), differences between plasma-derived and recombinant products cannot be discerned. New studies of either recombinant or plasma-derived products should consider all known parameters influencing inhibitor formation, thereby facilitating meaningful comparisons of inhibitor risk.     

Forum on: the role of recombinant factor VIII in children with severe haemophilia A

Summary. The development of recombinant FVIII (rFVIII) products, fuelled by the need for improved safety of treatment arising from the dramatic widespread blood‐borne virus transmission in the 1970–1980s revolutionized the care of children with haemophilia A over the last two decades. The larger availability of perceived safer replacement therapy associated with the introduction of rFVIII products reassured the haemophilia community and there was a strong push in some Western countries to treat haemophilic children only with rFVIII. Moreover, this significantly contributed in the 1990s to the diffusion outside Northern Europe of prophylactic regimens implemented at an early age to prevent bleeding and the resultant joint damage (i.e. primary prophylaxis), together with the possibility of home treatment. These changes led to a substantial improvement of the quality of life of haemophilic children and of their families. The general agreement that primary prophylaxis represents the first‐choice treatment for haemophilic children has been recently supported by two randomized controlled trials carried out with rFVIII products, providing evidence on the efficacy of early prophylaxis over on‐demand treatment in preserving joint health in haemophilic children. However, the intensity and optimal modalities of implementation of prophylaxis in children, in particular with respect to the issue of the venous access, are still debated. A number of studies also supports the role of secondary prophylaxis in children, frequently used in countries in which primary prophylaxis was introduced more recently. With viral safety now less than an issue and with the more widespread use of prophylaxis able to prevent arthropathy, the most challenging complication of replacement therapy for children with haemophilia remains the risk of inhibitor development. Despite conflicting data, there is no evidence that the type of FVIII concentrate significantly influences the complex multifactorial process leading to anti‐FVIII alloantibodies, whereas other treatment‐related factors are likely to increase (early intensive treatments due to surgery or severe bleeds) or reduce (prophylaxis) the risk. Although the optimal regimen is still uncertain, eradication of anti‐FVIII antibodies by immune tolerance induction (ITI), usually with the same product administered at inhibitor detection, should be the first‐choice treatment for all patients with recent onset inhibitors. This issue applies particularly to children, as most patients undergo ITI at an early age, when inhibitors usually appear. The availability of a stable and long‐lasting venous access represents a leading problem also in this setting. These and other topics concerning rFVIII treatment of haemophilic children were discussed in a meeting held in Rome on 27 February 2008 and are summarized in this report.     

Stability, efficacy, and safety of continuously infused sucrose-formulated recombinant factor VIII (rFVIII-FS) during surgery in patients with severe haemophilia

Summary.  Bolus injection (BI) of sucrose-formulated recombinant factor VIII (rFVIII-FS) is an approved treatment for haemophilia patients undergoing major surgery. Continuous infusion (CI) during surgery has potential benefits by providing steady administration of replacement factor to the patient, avoiding high peaks and low troughs. We tested the stability of rFVIII-FS under CI conditions and conducted a single-centre, open-label, phase III study to evaluate the efficacy and safety of CI using rFVIII-FS in haemophilia A patients undergoing surgery. Patients received bolus rFVIII-FS to achieve ≥80% FVIII levels 30–60 min presurgery, followed by CI of rFVIII-FS at a rate calculated to maintain haemostatic factor levels until days 8–10 post surgery. The rate of infusion was adjusted according to daily calculations derived from the actual clearance. The stability of rFVIII-FS was found to be appropriate for CI for 7 days under the same conditions as clinical settings. Fourteen patients (mean age 37.8 years) receiving on-demand FVIII treatment without a history of inhibitors underwent 15 surgical procedures including joint replacements, synovectomies, multiple tooth extractions, and cholecystectomy. Bleeding was similar to that observed in non-haemophilia patients undergoing similar operations in the same department. Haemostasis during surgery was considered by the attending surgeons as 'excellent' or 'good' in all cases; study investigators rated all 15 cases as 'excellent' overall. There were no adverse events, including inhibitor formation, related to rFVIII-FS. rFVIII-FS was found to be suitable for use in CI in haemophilia A patients undergoing major surgery.     

Laboratory and clinical markers of HIV infection in a national haemophilia cohort treated with recombinant factor VIII concentrate

Over an interval of approximately six months beginning in October 1993, most haemophilia A patients in Canada were switched from a plasma-derived intermediate-purity factor VIII concentrate (ipVIII) to a recombinant factor VIII (rVIII). In order to determine the consequence of this change in therapy on progression of HIV infection, we gathered surveillance data on clinical status and CD4 and CD8 cell counts in those patients who were HIV seropositive at the time of switching concentrates. Data were recorded at the time of switchover, annually for 2 years thereafter, and retrospectively at a point 1 year prior to the switch. CD4 cells fell significantly over the study period. Multiple direct comparisons revealed that this decline was restricted to the time intervals which included the final year in which patients received intermediate-purity factor VIII concentrate (ipVIII). In the 2 year interval in which rVIII was used exclusively, there was a nonsignificant fall in CD4 cells. Changes in CD4 cells did not correlate with the intensity of exposure to either ipVIII or rVIII. CD8 cells did not fall significantly over the study period. There was no obvious reduction in the incidence of death or clinical progression over the 2 years in which rVIII was used. However, we are hopeful that the stabilizing trend in CD4 cell counts which followed the introduction of rVIII will be predictive of corresponding clinical stabilization over the coming years.     

Viral safety of a pasteurized, monoclonal antibody-purified factor VIII concentrate in previously untreated haemophilia A patients

The efficacy and viral safety of a pasteurized, immunoaffinity-purified procoagulant factor VIII protein (FVIII:C; Monoclate-P) was studied in two multicentre, prospective, open-label trials in 30 previously untreated patients, 18 with severe (< 1% FVIII:C activity), and 12 with moderate (1% to 5% FVIII:C activity) haemophilia A. Clinical assessments, performed at screening and regularly thereafter for 6 to > 24 months (maximum 34 months), showed that none of 24 assessable patients acquired illnesses consistent with monitored transfusion-transmissible diseases. No patients acquired hepatitis B surface antigen, or antibodies against hepatitis B core antigen, hepatitis C, or human immunodeficiency virus. Likewise, no patients acquired treatment-related hepatitis A antibodies or sustained elevations of alanine aminotransferase levels. The safety profile for Monoclate-P is brought about by a multi-step safety system that incorporates viral inactivation (through a combination of immunoaffinity chromatography and pasteurization) plus donor screening, plasma testing, and quality assurance. The inhibitor development rate (13% low titre, 10% high titre) was similar to that reported in the literature for other FVIII concentrates (24% to 52%). The most frequently reported adverse events were related to typical infant and childhood diseases. Monoclate-P was effective in all patients treated according to protocol, except in two, who developed inhibitors.     

Efficacy and safety of OBI‐1, an antihaemophilic factor VIII (recombinant), porcine sequence,in subjects with acquired haemophilia A

Acquired haemophilia A (AHA) is a rare bleeding disorder caused by autoantibodies against human factor VIII (hFVIII). OBI‐1 is an investigational, B‐domain deleted, recombinant FVIII, porcine sequence, with low cross‐reactivity to anti‐hFVIII antibodies. Efficacy can be monitored with FVIII activity levels in addition to clinical assessments. This prospective, open label, phase 2/3 study was designed to evaluate the efficacy of OBI‐1 treatment for bleeding episodes in subjects with AHA. After an initial dose of 200 U kg^?1, OBI‐1 was titrated to maintain target FVIII activity levels, in correlation with clinical assessments, throughout the treatment phase. All 28 subjects with AHA had a positive response to OBI‐1 treatment 24 h after initiation despite inhibition of FVIII activity levels immediately after infusion in 10 subjects with baseline anti‐porcine FVIII inhibitors. Control of the qualifying bleed was ultimately achieved in 24 of 28 subjects. No related serious adverse events, thrombotic events, allergic reactions or thrombocytopaenia occurred. The results of this study indicate that OBI‐1 is safe and effective in treating bleeding episodes in subjects with AHA. The ability to safely and effectively titrate dosing based on FVIII activity levels in this study demonstrates that OBI‐1 fulfils the unmet medical need to monitor the key coagulation parameter in AHA patients.     

Real-world safety and effectiveness of recombinant porcine sequence factor VIII in acquired haemophilia A: A non-interventional,post-authorization safety study

Introduction

Recombinant porcine factor VIII (rpFVIII, susoctocog alfa) is indicated for the treatment of bleeding episodes in adults with acquired haemophilia A (AHA).

Aim

To provide long-term real-world safety and effectiveness data for rpFVIII in the management of AHA bleeding episodes.

Methods

US PASS (NCT02610127) was a multicentre, uncontrolled, open-label, post-marketing safety surveillance study conducted in adults with AHA. Data were collected retrospectively or prospectively for 180 days after rpFVIII treatment. The primary outcome was the incidence of treatment-related serious adverse events (SAEs). Secondary outcomes included haemostatic effectiveness of rpFVIII and rpFVIII utilization.

Results

Fifty-three patients were enrolled from December 2015 to June 2019 (prospective, n = 30; retrospective, n = 23). Six patients experienced seven treatment-related SAEs (incidence 12.0%). The most common treatment-related SAE was FVIII inhibition (inhibiting antibodies to rpFVIII; incidence 8.0%, 95% CI: 2.2–19.2). Five patients reported seven thromboembolic events; one was an SAE and possibly related to rpFVIII. Of bleeding events treated with rpFVIII, 80.3% (57/71) of bleeds resolved with rpFVIII. The median (range) dose of rpFVIII per infusion was 50 (10–300) units/kg, with a median (range) of 6.0 (1–140) infusions and a median (range) time from bleed onset to bleed resolution of 14.0 (2.0–132.7) days.

Conclusion

In this real-world study of rpFVIII for AHA, no new safety signals were identified compared with previous clinical trial findings. Eighty percent of bleeds resolved with rpFVIII treatment.     

Recombinant factor IX (BAX326) in previously treated paediatric patients with haemophilia B: a prospective clinical trial

A newly developed recombinant factor IX (BAX326¹) was investigated for prophylactic use in paediatric patients aged <12 years with severe (FIX level <1%) or moderately severe (FIX level 1–2%) haemophilia B. The aim of this prospective clinical trial was to assess the safety, haemostatic efficacy and pharmacokinetic profile of BAX326 in previously treated paediatric patients. BAX326 was administered as prophylaxis twice a week for a period of 6 months, and on demand for treatment of bleeds. Safety was assessed by the occurrence of related AEs, thrombotic events and immunologic assessments. Efficacy was evaluated by annualized bleeding rate (ABR), and by treatment response rating (excellent, good, fair, none). PK was assessed over 72 h. None of the 23 treated paediatric subjects had treatment‐related SAEs or AEs. There were no thrombotic events, inhibitory or specific binding antibodies against FIX, rFurin or CHO protein. Twenty‐six bleeds (19 non‐joint vs. 7 joint bleeds) occurred (mean ABR 2.7 ± 3.14, median 2.0), of which 23 were injury‐related. Twenty subjects (87%) did not experience any bleeds of spontaneous aetiology. Haemostatic efficacy of BAX326 was excellent or good for >96% of bleeds (100% of minor, 88.9% of moderate and 100% of major bleeds); the majority (88.5%) resolved after 1–2 infusions. Longer T_1/2 and lower IR were observed in younger children (<6 years) compared to those aged 6 to 12 years. BAX326 administered as prophylactic treatment as well as for controlling bleeds is efficacious and safe in paediatric patients aged <12 years with haemophilia B.     

Human recombinant DNA-derived antihaemophilic factor (factor VIII) in the treatment of haemophilia A: conclusions of a 5-year study of home therapy

Fifty-eight previously treated haemophilic subjects were treated exclusively with the recombinant FVIII (rFVIII-KOGENATE®) produced by Bayer Corporation (Berkeley, CA) in an international multicentre prospective study of more than 5 years duration. Fifty-four of the 58 had severe haemophilia (< 2% FVIII) and four had moderate haemophilia (2–5% FVIII); 23/58 (40%) were seropositive for HIV, while 35/58 (60%) were HIV seronegative. Patients were monitored for safety and efficacy over a median period of 4.7 years (range 0.9–5.9 years) and received 17 922 infusions totalling 25.7 million units of rFVIII. Of 7107 bleeding episodes reported in home diaries, 5831 (82%) required only one treatment with rVIII. Twenty-five invasive surgical procedures in 17 patients, including eight joint replacements, were successfully accomplished and 13 serious bleeding episodes in eight patients were successfully treated. FVIII recovery performed on 885 occasions using 39 different lots of rFVIII showed mean incremental recovery of 2.48% IU^?1 kg^?1 (± 0.64). Adverse events were associated with 42 infusions (0.2%); none caused discontinuation of therapy. Immunological parameters remained stable in HIV-seronegative subjects treated with rFVIII; a small decrease in CD4 counts was noted in HIV-seropositive individuals (mean ? 37.2 cells mm–3 yr^?1). No de novo formation of inhibitors to FVIII was noted; and no clinical allergic reactions occurred to murine or hamster proteins. These conclusions from the longest monitored safety study ever performed for a haemophilia treatment product (with more than 5 years of observation) confirm previous interim study reports that rFVIII is well tolerated over the long-term, has biological activity comparable to that of plasma-derived FVIII, and is safe and efficacious for the treatment of haemophilia A.     

BAY 94‐9027, a PEGylated recombinant factor VIII,exhibits a prolonged half‐life and higher area under the curve in patients with severe haemophilia A: Comprehensive pharmacokinetic assessment from clinical studies

Introduction

Recombinant factor VIII (rFVIII) products with extended half‐lives, such as BAY 94‐9027, can potentially maintain higher FVIII levels for longer periods of time, thus providing improved bleeding protection vs standard‐acting FVIII products.

Aim

To characterize the pharmacokinetic (PK) profile of BAY 94‐9027 from phase 1, phase 2/3 (PROTECT VIII) and phase 3 (PROTECT VIII Kids) clinical trials in adults, adolescents and children with severe haemophilia A

Methods

Patients with severe haemophilia A (FVIII <1%) with >50 FVIII exposure days (EDs) and no history of inhibitors were included in the phase 1 (18–65 years, ≥150 EDs), PROTECT VIII (12–65 years, ≥150 EDs) and PROTECT VIII Kids (<12 years, >50 EDs) trials. PK parameters were assessed following a 25‐IU/kg or 60‐IU/kg BAY 94‐9027 dose in the phase 1 study after the first and repeated infusion, in PROTECT VIII after the first and repeated 60‐IU/kg infusion and in PROTECT VIII Kids after a single 60‐IU/kg infusion. The chromogenic assay was used to assess FVIII activity.

Results

Compared with sucrose‐formulated rFVIII, BAY 94‐9027 had reduced clearance that resulted in a ~1.4‐fold increase in half‐life and dose‐normalized area under the curve (AUC). The BAY 94‐9027 PK profile was comparable after single‐ and repeated‐dose administrations. Dose‐proportional increases were observed between 25‐ and 60‐IU/kg administrations. BAY 94‐9027 PK characteristics were age dependent, consistent with other FVIII products.

Conclusions

BAY 94‐9027 shows an extended half‐life and increased AUC vs standard‐acting FVIII products. These PK characteristics will result in higher FVIII levels for longer duration.