Clinical safety surveillance study of the safety and efficacy of long-term home treatment with ReFacto® utilizing a computer-aided diary: a Nordic multicentre study

Summary.  A Nordic multicentre, open-label, non-interventional postmarketing surveillance study was carried out during a period of 24 months evaluating safety and efficacy of ReFacto as prophylactic or on-demand replacement therapy in patients with haemophilia A treated by self-medication. Fifty-seven patients were enrolled and studied for safety; efficacy was evaluated in 39 patients who received ReFacto for 24 months and recorded sufficient diary data on a hand-held computer. The compliance of using the device was good in small children, variable in adults and poor in teenagers. The fact that the overall compliance was low constituted a limitation of the number of patients with reliable diary data. Overall safety was rated as excellent or good by the clinicians for all patients at all visits and overall efficacy at 24 months evaluated to be excellent (74%) or good (26%). It was noticed that ≥50% of patients/parents reported no absences from school or work owing to bleeding episodes during the study period. Among patients on regular prophylaxis, 6 of the 30 patients (20%) receiving ReFacto experienced no bleeding episodes. A median of four bleeding episodes occurred during the 24-month study period, and 93% of the episodes were resolved with ≤2 ReFacto infusions. In the 7 on-demand patients, there was a median of 18 bleeding episodes, 87% of which resolved with ≤2 ReFacto infusions. Interestingly, 42% of the ReFacto infusions taken by the patients classified to the on-demand group were registered as prophylactic treatment. In conclusion, ReFacto demonstrated good safety and efficacy in prophylaxis as well as treatment of bleeding episodes.     

B-domain deleted recombinant factor VIII preparations are bioequivalent to a monoclonal antibody purified plasma-derived factor VIII concentrate: a randomized, three-way crossover study

BACKGROUND: Deletion of the B-domain of recombinant blood coagulation factor VIII (BDDrFVIII) increases the manufacturing yield of the product but does not impair in vitro or in vivo functionality. BDDrFVIII (ReFacto) has been developed with the additional benefit of being formulated without human albumin. OBJECTIVE: The primary objective of this three-way crossover-design study was to compare the pharmacokinetic (PK) parameters of two BDDrFVIII formulations (one reconstituted with 5 mL of sterile water, the other reconstituted with 4 mL sodium chloride 0.9% USP) with those of a plasma-derived, full-length FVIII preparation (Hemofil M) in patients with haemophilia A to determine bioequivalence. METHODS: A series of blood samples were collected over a period of 48 h after i.v. administration of each of the FVIII preparations. Plasma FVIII activity was determined using a validated chromogenic substrate assay. Plasma FVIII activity vs. time curves was characterized for a standard set of PK parameter estimates. Two parameter estimates, the maximum plasma concentration (Cmax) and the area under plasma concentration vs. time curves (AUCs), were used to evaluate bioequivalence. The two preparations were considered bioequivalent if the 90% confidence intervals for the ratio of geometric means for Cmax and AUCs fell within the bioequivalence window of 80% to 125%. RESULTS/CONCLUSION: Results show that each BDDrFVIII formulation is bioequivalent to Hemofil M and the two formulations of BDDrFVIII are bioequivalent to each other.     

Successful use of ReFacto continuous infusion in two paediatric patients with severe haemophilia A undergoing orthopaedic surgery

In this report we describe the successful use of B-domain-deleted recombinant factor VIII (ReFacto) administered by continuous infusion during orthopaedic procedures in two children with severe haemophilia A. Both patients underwent ankle synovectomy and in patient 2, a medial patello-femoral ligament repair was performed in the same operative session. Patient 2 developed septic arthritis A in his knee joint and arthroscopic joint irrigation and debridement was performed 2 weeks after the initial procedure. Surgical cover was initiated with a bolus dose of ReFacto 50 IU kg(-1) followed by continuous infusion at 3.3-4.8 IU kg(-1) h(-1) which was maintained for up to 9 days postoperatively. Patient 2 received an additional bolus dose of 15 IU kg(-1) during the infusion period. All procedures were performed without haemostatic complications and long-term orthopaedic outcomes were good in both patients.     

Continuous infusion of B-domain deleted recombinant factor VIII (ReFacto) in patients with haemophilia A undergoing surgery: clinical experience

This retrospective, open-label, non-comparative study evaluated continuous infusion of recombinant factor VIII (ReFacto), B-domain deleted recombinant FVIII (BDDrFVIII), in patients with haemophilia A undergoing surgery and requiring >5 consecutive days of treatment. Sixteen patients from eight centres underwent a total of 20 procedures. Haemostatic outcome was assessed as 'excellent' or 'good' in 75% of procedures, and target FVIII:C levels were maintained throughout the continuous infusion period. The reported volume of blood loss during surgery was also within the normal range for non-haemophilic patients for the type of surgery performed. Red blood cell transfusions were required to balance excessive blood loss during BDDrFVIII continuous infusion in eight (40%) procedures (seven patients), five with bleeding or requiring volume replacement and three to treat anaemia secondary to blood loss. Non-serious adverse events considered by investigators as possibly or probably related to BDDrFVIII continuous infusion were infrequent (n = 5) considering the duration of treatment (n =239 cumulative days of continuous infusion), and all of these were mild-to-moderate in severity. No thromboembolic complications were reported except for one case of thrombophlebitis occurring at the infusion site. Only two patients (four events) experienced serious adverse bleeding; BDDrFVIII was otherwise well-tolerated. These data show that continuous infusion of BDDrFVIII provides reliable haemostasis and is an effective and well-tolerated regimen for patients with haemophilia A undergoing surgery.     

ReFacto and Advate: a single-dose, randomized, two-period crossover pharmacokinetics study in subjects with haemophilia A.

ReFacto is a recombinant B-domain-deleted, monoclonal antibody-purified, solvent-detergent-treated factor VIII (BDDrFVIII) with no albumin added to the final formulation. Although ReFacto has been shown to be bioequivalent to a plasma-derived FVIII product (Hemophil-M) in a randomized, crossover pharmacokinetic (PK) study, the comparability of ReFacto with the full-length (complete sequence) recombinant FVIII (FLrFVIII, Advate) product has not been previously examined in this manner. The primary objective of this study was to compare the PKs of ReFacto with those of Advate in patients with severe haemophilia A. This was a third-party unblinded, randomized, multicentre, two-period crossover PKs study of ReFacto and Advate in subjects with severe haemophilia A (FVIII:C < or =1%). Blood samples were collected over a 48-h period after i.v. administration of each of the FVIII products. FVIII:C was determined using the chromogenic substrate assay (CSA) in a central laboratory. The plasma FVIII:C PK parameters of ReFacto and Advate were determined using non-compartmental analysis. Bioequivalence was assessed on maximum plasma concentration (C(max)) and the area under the plasma concentration vs. time curves (AUCs) using an anova. The two products were judged to be equivalent if the 90% confidence limits of the ratio of the geometric mean values of C(max) and AUCs fell within the interval of 80-125%. Results from this PKs comparison of two different rFVIII products, using chromogenic substrate assay to measure FVIII:C, showed that ReFacto and Advate are bioequivalent to each other.     

An improved manufacturing process for Xyntha/ReFacto AF

Summary. ReFacto^® Antihemophilic Factor is a second‐generation antihaemophilia A product manufactured using a process that includes therapeutic grade human serum albumin (HSA) in the cell culture medium, but is formulated without HSA as a stabilizer. Even though this second‐generation antihaemophilia product has a good safety profile, a programme was implemented to eliminate all animal‐ and human‐derived raw materials from the production process, thus producing a third‐generation product. To that end, HSA has been removed from the master and working cell banks and from the culture medium. The hybridoma‐derived monoclonal antibody formerly used in the purification process has been replaced by a chemically synthesized affinity peptide, and a virus‐retaining filtration step has been added to enhance the clearance of large viruses, such as retroviruses. The purification process has been validated for the removal of a panel of model viruses and provides significant clearance of all viruses tested. Host cell‐ and process‐derived impurity removal validations also were conducted, including host cell DNA and protein, in addition to the affinity peptide. Compared with the product manufactured according to the original process, these changes had no detectable effect on the structural integrity, stability or clinical efficacy of this antihaemophilia A product. The product produced by the improved manufacturing process is named Xyntha?/ReFacto AF.     

Immune Tolerance Therapy in Patients with Acquired Hemophilia

Acquired hemophilia is a rare disorder with an estimated annual incidence of 0.2-1 cases per million individuals. The etiology of the disorder remains obscure, although approximately half of all cases are associated with other underlying conditions. In acquired hemophilia, the severe hemorrhagic diathesis is caused by the development of autoantibodies directed against a clotting factor, most commonly factor VIII. These autoantibodies inhibit normal coagulation and lead to bleeding complications, which can be life-threatening in a high percentage of cases. Prompt diagnosis and appropriate management of the disorder enable effective control; the short- and long-term aims of therapy are to terminate the acute bleed and eliminate or reduce the inhibitor, respectively. Immune tolerance therapy has been shown to successfully eradicate or suppress inhibitors in patients with congenital hemophilia A and may be applicable to patients with acquired hemophilia. Here we present preliminary data on the use of immune tolerance therapy in patients with acquired hemophilia and discuss possible treatment strategies.     

Performance of recalibrated ReFacto® laboratory standard in the measurement of FVIII plasma concentration via the chromogenic and one-stage assays after infusion of recalibrated ReFacto® (B-domain deleted recombinant factor VIII)

Summary.  The use of ReFacto Laboratory Standard ( RLS ) in the one-stage clotting assay was proposed to reduce the underestimation of factor VIII (FVIII) plasma concentration after the infusion of 'ReFacto^®' (B-domain deleted recombinant FVIII) in haemophilia A patients. Both ReFacto^® and RLS were recently recalibrated, with the resulting materials containing approximately 20% more protein than the previous products. The aim of this study was to evaluate the performance of recalibrated RLS in the measurement of FVIII plasma concentration after the infusion of recalibrated ReFacto^®. In 13 severe haemophilia A patients, 25 IU kg⁻¹ of ReFacto ^® were injected intravenously. Venous blood samples were collected at 0.25, 0.5, 1, 3, 6, 9, 24, 28 and 32 h after the end of the infusion. Pharmacokinetic parameters were measured for the chromogenic and one-stage assays using International Plasma Standard (IPS) and RLS for both assays and assuming a non-compartmental drug disposition. Comparisons among assays and standards were performed using anova . Pharmacokinetic estimates obtained with the chromogenic method were in agreement with those published in the literature. The one-stage method was confirmed to be more sensitive to lower plasma concentrations of FVIII. The measured maximum plasma concentration ( C _max ) was slightly higher than theoretical values and independent of the assay used. C _max , area under the curve ( AUC) and volume of distribution at steady state ( V _ss ) presented non-significant differences among the methods and standards used. The clinical utility of RLS in the evaluation of FVIII concentration after the infusion of ReFacto^® seems to be reduced since recalibration of the product.