Incidence Of Inhibitor Formation Research Articles

Pharmacokinetics Of Recombinant Factor IX Fc Fusion Protein (rFIXFc) In Pediatric Subjects With Hemophilia B: An Interim Analysis Of The Kids B-LONG Study

IntroductionProphylaxis with factor IX (FIX) is the optimal treatment for patients with hemophilia B; however, due to the short half-life of currently available FIX products, frequent injections may be required to prevent bleeding episodes. To prolong half-life and reduce injection frequency, a long-acting recombinant FIX Fc fusion protein (rFIXFc) consisting of one rFIX molecule covalently linked to the Fc domain of immunoglobulin G1 (IgG1) was developed. In a phase 3 study in adults and adolescents, rFIXFc had a 2.43-fold increase in half-life and 50% reduction in clearance (CL) compared with FIX (BeneFIX®) (J Thromb Haemost. 2013;11[2]:241). The Kids B-LONG study (NCT01440946) was designed to evaluate the pharmacokinetics (PK), safety, and efficacy of rFIXFc prophylaxis in previously treated pediatric subjects with hemophilia B. The objective of this planned interim analysis was to determine the PK parameters of rFIXFc in subjects enrolled in Kids B-LONG and compare these parameters to their pre-study FIX PK parameters. MethodsThis multicenter, open-label, phase 3 study is currently enrolling previously treated subjects aged<12 years with severe hemophilia B (≤2 IU/dL endogenous FIX), at least 50 exposure days (EDs) to FIX products, and no inhibitors to FIX. Subjects are stratified into two age cohorts (<6 and 6 to<12 years of age). A weekly prophylactic regimen of 50-60 IU/kg of rFIXFc is administered to all subjects, with subsequent dose and interval adjustments based upon PK data and bleeding frequency. Subjects will continue treatment until they achieve 50 EDs. The primary endpoint is the incidence of inhibitor formation. A sequential PK analysis is performed to compare the PK parameters of rFIXFc with that of pre-study FIX products. PK sampling of pre-study FIX occurs at baseline prior to first dose of FIX (50 IU/kg) and at 5 additional time points through 48 hours. PK sampling of rFIXFc occurs prior to first dose of 50 IU/kg rFIXFc and at 7 additional time points through 168 hours following the first dose; a washout period of 96 hours is required before the first dose of both pre-study FIX and rFIXFc. Plasma FIX activity is measured using the one-stage clotting assay calibrated against a commercially available FIX plasma standard and the FIX activity-over-time profiles are analyzed by non-compartmental analysis (NCA) using the PK data analysis software Phoenix™ WinNonlin 6.2.1.51. A data cut-off date of 23 April 2013 was used to report PK data in this interim analysis. ResultsAt the time of this interim analysis, 24 subjects were enrolled and had received at least one dose of pre-study FIX and/or rFIXFc. Of 18 subjects with evaluable PK profiles, 15 had complete PK profiles for both pre-study FIX (BeneFIX®, Haemosolvex®, or Alphanine®) and rFIXFc. A comparison of PK parameters for rFIXFc versus FIX for both age cohorts is presented in Table 1. rFIXFc had a more than 3-fold prolongation in half-life and a more than 60% reduction in CL compared to the FIX products.Table 1PK of FIX products and rFIXFc in pediatric subjects (Geometric mean [95% CI])Half-life (hr)CL (mL/dL/kg)IR (IU/dL per IU/kg)Vss (mL/kg)< 6 yrsFIX (pre-study) n=518.1 (15.6 - 20.9)11.8 (9.27 - 15.0)0.525 (0.447 - 0.617)293 (247 - 348)rFIXFc (on-study) n=663.6 (42.1 – 96.2)4.36 (3.56 – 5.34)0.593 (0.494 - 0.711)344 (276 - 429)rFIXFc/FIX Ratio n=43.70 (2.56 - 5.34)0.385 (0.280 - 0.529)1.13 (0.981 - 1.31)1.21 (1.18 - 1.25)6 to<12 yrsFIX (pre-study) n=1317.8 (16.0 – 19.8)8.76 (7.35 - 10.5)0.638 (0.502 - 0.812)217 (165 - 286)rFIXFc (on-study) n=1370.4 (61.0 - 81.3)3.51 (3.01 – 4.09)0.718 (0.612 - 0.841)290 (237 - 354)rFIXFc/FIX Ratio n=113.99 (3.36 - 4.74)0.386 (0.322 - 0.462)1.16 (0.942 - 1.42)1.31 (0.992 - 1.74) ConclusionIn comparison to currently available FIX products, rFIXFc had a prolonged half-life and reduced CL in pediatric subjects, which was similar to previous observations in adults and adolescents. The final analysis of the Kids B-LONG study will provide further PK information and evaluate the safety and efficacy of rFIXFc in children. Disclosures:Fischer:Biogen Idec, Baxter, Novo Nordisk, Bayer: Membership on an entity's Board of Directors or advisory committees; Baxter, Bayer, Novo Nordisk, Pfizer: Research Funding. Kulkarni:Biogen Idec, Novo Nordisk, Baxter : Membership on an entity's Board of Directors or advisory committees. Ragni:Biogen Idec: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb, Smith Kline Glaxo, Tacere Benitec: Consultancy; Baxter, Bayer, Biogen Idec, Bristol Myers Squibb, CSL Behring, Merck, Novo Nordisk, Pfizer, Smith Kline Glaxo: Research Funding. Rangarajan:Baxter, Pfizer: Research Funding; Biogen Idec : Membership on an entity's Board of Directors or advisory committees. Dong:Biogen Idec: Employment, Equity Ownership. Li:Biogen Idec: Employment, Equity Ownership. Jiang:Biogen Idec: Employment, Equity Ownership. Nugent:Biogen Idec: Employment, Equity Ownership. Pierce:Biogen Idec: Employment, Equity Ownership. Allen:Biogen Idec: Employment, Equity Ownership.

Pharmacokinetics, Coagulation Factor Consumption, and Product Efficacy in Patients Crossing Over from Full-Length FVIII to B-Domain Deleted R-FVIII and Back to Full-Length FVIII.

Introduction: Treatment with B-domain deleted recombinant factor VIII (BDD-rFVIII) has proven to be effective and safe both in clinical trials and post marketing surveillance studies. However, intermittent concerns have been raised regarding the pharmacokinetic performance, efficacy and incidence of inhibitor formation with the BDD-rFVIII product.Aims: The objective of the present study was to perform a retrospective survey of half-life measurements, clinical efficacy and safety in patients with severe Haemophilia A, when switching treatment from full-length FVIII (FL-FVIII) to BDD- rFVIII and then back to full-length FVIII. We hypothesized that the biological half-life of FVIII would be equal regardless of the product used. Furthermore, we hypothesized that the total factor consumption and bleeding frequency would be indistinguishable irrespective of product used. Finally, we report on safety as evaluated by development of inhibitors and clinical outcome following surgery.Methods: Patients treated with BDD-rFVIII (between 1998 and 2008) were identified from an in-house database. Data collected included annual half-life (T/2) and recovery times (K values), total coagulation factor consumption, and number of bleeds per year as measures of clinical efficacy. Safety data consisted of surgical outcome data and incidence of inhibitor formation. The information was extracted from electronic databases and verified by a review of patients' clinical notes. The outcome data was non-parametric, hence, paired analysis was performed using Wilcoxon signed rank test and Friedman ANOVA. Data is given as a median value and range. P-value < 0.05 was set as level of statistical significance.Results: In total, 70 patients received BDD-rFVIII on at least one occasion. Following a specified list of criteria, evaluable data was obtainable for 15 males, all with verified severe Haemophilia A (FVIII:C <1%). The average age was 10.2 years (median 10, range 4–17). The median duration on BDD-rFVIII was 30 months (range 20–54). Using the one-way non-parametric ANOVA, no statistically significant difference was detected between the half-life and recovery times recorded during the switch from FL-FVIII (T/2 median 9.15 hours, range 6.4–22; K median 2.7, range 2.0–3.4) to BDD-rFVIII (T/2 median 9.7, range 4.7–16.8; K median 1.8, range 1.0–3.5) and back to FL-FVIII (T/2 median 9.0, range 5.0–19.5; K median 2.0, range 1.6–2.8). Furthermore, there was no significant difference in coagulation factor usage (BDD-rFVIII median 4803 iu/kg/year, range 659–11304; FL-FVIII median 5349, range 1691–10146), nor number of reported bleeds (BDDrFVIII median 6, range 0–24; FL-FVIII median 5.0, range 0–17). None of the 15 patients developed an inhibitor on BDD-rFVIII. Of the total 70 patients, 11 received BDD-rFVIII to cover surgical procedures (8 minor, 3 major interventions). There were no reports of excess bleeding.Conclusions: In this retrospective survey, BDD-rFVIII was found to be equivalent to other FVIII products in terms of half-life measurements, clinical efficacy and safety.

Safety and efficacy of KOGENATE® Bayer in previously untreated patients (PUPs) and minimally treated patients (MTPs)

Safety and efficacy of KOGENATE Bayer (Kogenate FS), a second-generation full-length recombinant factor VIII formulated with sucrose as stabilizer and produced without the addition of human albumin during purification and the final formulation, was assessed in a prospective, international clinical trial including 31 previously untreated patients (PUPs) and minimally treated patients (MTPs) with severe haemophilia A in home therapy and surgery. Factor VIII inhibitor development was monitored and mutation type profiles were analysed. As of 30 June 2000, the patients received a total of 2.729 infusions (mean 88; range 6-274) for bleeding episodes, surgery or prophylactic treatment. No unexpected drug-related adverse events were observed. Four patients developed an inhibitor after 3-12 exposure days (EDs). One patient successfully underwent immune tolerance treatment; inhibitors in two patients disappeared spontaneously with on-demand treatment, while the inhibitor titre remains low in one patient. Twenty-nine patients (93%) with more than 20 EDs can be regarded as at low risk for inhibitor development. In conclusion, KOGENATE Bayer is efficacious and well-tolerated for treatment of children with severe haemophilia A. The incidence of inhibitor formation is not different to that observed with other recombinant or plasma-derived products.

Continuous Infusion of Recombinant Factor VIIa: Continue or not?

The development of a neutralizing inhibitor in a hemophilia patient represents the most serious complication of factor replacement therapy today. Among patients with hemophilia A and B, the incidence of inhibitor formation is 18-32% and 2-3%, respectively. The propensity for inhibitor development in either disorder is a function of the underlying molecular defect as well as other inherited and treatmentrelated factors. Multidomain deletions, gene rearrangements, and missense mutations, molecular events associated with the absence of circulating factor VIII or IX, engender the greatest risk (2-4). Some inhibitors are transient or can be abolished by repeated and frequent exposure to the congenitally missing coagulation factor, a process that has been termed immune tolerance induction. However, in a subset of patients, particularly those with a high titer or longstanding inhibitor, tolerance cannot be achieved and alternative measures to achieve hemostasis become necessary. Patients with high titer inhibitors (> 5 BU) are routinely treated with

Neoantigens and antibodies to factor VIII

It is well known that 10–20% of severe haemophiliacs are likely to develop inhibitors to factor VIII, usually soon after the commencement of therapy. Two recent inhibitor outbreaks have occurred in patients treated for a number of years on switching to a product subjected to additional virus inactivation. Hence the incidence of inhibitor formation may be affected by the type of product used for treatment and the potential for processing to result in ‘neoantigens’. Examination of the parts of factor VIII interacting with inhibiting antibodies, and the effect of various therapies on these, can teach us something about the mechanisms involved in antibody formation. However, the development of pre-clinical assays to assess products and processes for neoantigen formation should allow the prevention of inhibitor outbreaks. This review summarizes current in vitro and in vivo approaches to this problem, concluding that most available assays are inadequate for this purpose, with competitive immunoassay and phospholipid binding providing the most hopeful route forward.