Recombinant Factor IX-Fc Fusion Protein Research Articles

Efficacy of rFIXFc versus N9-GP Prophylaxis in Patients with Hemophilia B: Matching-Adjusted Indirect Comparison of B-LONG and PARADIGM 2 Trials.

For patients with hemophilia B, extended half-life factor IX (FIX) products are available for prophylaxis and for treating bleeds. Different methods are used to extend the half-lives of recombinant FIX Fc fusion protein (rFIXFc) and nonacog beta pegol (N9-GP). This affects their biodistribution and plasma FIX levels, although differences do not always correlate with clinical outcomes. A matching-adjusted indirect comparison (MAIC) of prophylaxis with rFIXFc and N9-GP was performed, based on licensed dosing in the European Union. Combined rFIXFc data from the weekly and individualized interval prophylaxis arms of the B-LONG clinical trial, and N9-GP data from the 40 IU/kg once-weekly prophylaxis arm of PARADIGM 2 were used in a MAIC. Individual patient data for rFIXFc (n=87) were matched to aggregated data for N9-GP (n=29). Estimated annualized bleeding rates (ABRs) for rFIXFc were recalculated using a Poisson regression model with adjustment for over-dispersion, and compared with ABRs reported for N9-GP, using incidence rate ratios (IRRs) with 95% confidence interval (CI). There was no evidence of significant differences in estimated ABRs between prophylaxis with rFIXFc and N9-GP. Analysis of pooled rFIXFc weekly and interval-adjusted dosing compared with N9-GP 40 IU/kg once weekly produced estimated ABRs of 2.59 versus 2.51 (IRR 1.03; 95% CI 0.56-1.89), as well as 1.34 versus 1.22 (IRR 1.10; 95% CI 0.42-2.91) and 1.13 versus 1.29 (IRR 0.88; 95% CI 0.47-1.63) for overall, spontaneous, and traumatic bleeding events, respectively. The study did not reveal any significant differences in the efficacy of rFIXFc and N9-GP prophylaxis. Given differences in trough levels (rFIXFc dosing was targeted to achieve a trough 1-3 IU/dL above baseline versus a reported estimated N9-GP mean trough of 27.3 IU/dL), interpreting plasma FIX levels as potential surrogate efficacy markers requires consideration of compound-specific pharmacokinetic profiles.

Real-World Effectiveness of rFIXFc Prophylaxis in Patients with HaemophiliaB Switched from Standard Half-Life Therapy in Three European Countries.

The current study describes real-world clinical outcomes and factor usage among patients with haemophiliaB switching from standard half-life factorIX (SHL FIX) treatment to recombinant factorIX Fc fusion protein (rFIXFc) prophylaxis in European treatment centres. This non-interventional, retrospective, multicentre chart review evaluated medical records from adult and paediatric patients with haemophiliaB in Denmark, Germany and the UK. Patients had documented SHL FIX treatment, on-demand or prophylaxis, for ≥ 6months before starting rFIXFc prophylaxis, and subsequent data for ≥ 6months afterwards (up to 24months). Primary endpoints included annualised bleeding rates (ABRs), prophylactic factor consumption and injection frequency. Data from 30 patients (24/30 [80.0%] with severe disease) showed overall mean (standard deviation, SD) ABRs of 4.7 (6.3) on SHL FIX treatment and 1.7 (2.3) after switching to rFIXFc prophylaxis. The reduction in mean (SD) ABRs was greater when switching from SHL FIX on-demand treatment (n = 6), with a decrease from 10.5 (9.9) to 2.6 (4.5), than when switching from SHL FIX prophylaxis (n = 24), with a decrease from 3.3 (4.3) to 1.5 (1.4). Among prior SHL FIX prophylaxis patients, switching to rFIXFc prophylaxis increased the proportion of those with zero bleeds from 21.7% to 45.8% during the 6months before and after switching, respectively. In the total population, five of six target joints (83.3%) present when patients started rFIXFc prophylaxis subsequently resolved. In patients switching from SHL FIX prophylaxis to rFIXFc prophylaxis, mean (SD) weekly injection frequency was reduced by 1.0 (0.7) and mean (SD) factor consumption was reduced by 27.7 (49.6) IU/kg/week. This study demonstrates the effectiveness of rFIXFc prophylaxis in real-world clinical practice. Improvements in both clinical effectiveness and factor usage associated with rFIXFc prophylaxis may potentially reduce patient burden and improve quality of life.

Fusion partners matter: Factor VIII light chain binding enables CD16-mediated recombinant Factor VIII-Fc fusion protein natural killer cell activation.

Abstract Recombinant Factor VIII-Fc fusion protein (rFVIIIFc) is an enhanced half-life therapeutic protein product used for the management of hemophilia A. Recent studies have demonstrated that rFVIIIFc interacts with multiple Fc gamma receptors (FcγR) resulting in the activation or inhibition of a wide variety of FcγR expressing immune cells. We demonstrated that rFVIIIFc activates natural killer (NK) cells via Fc mediated interactions with FcγRIIIA or CD16. Here, we used human NK cell lines and primary NK cells enriched from peripheral blood leukocytes to study rFVIIIFc-mediated NK cell activation. Following overnight incubation of NK cells with rFVIIIFc, we assessed cellular activation by measuring inflammatory cytokine secretion (IFNγ by ELISA) or cellular degranulation (flow cytometry-based surface LAMP1/CD107a). In some cases, we introduced specific blocking molecules (anti-FVIII, anti-Fc, or anti-CD16) into our assays to act as inhibitors of NK cell activation. We identified the FVIII light chain as playing a key role in the activation of CD16 +NK cells by rFVIIIFc. Using FVIII domain-specific inhibitors, we demonstrate that blocking C1 or C2 domain-mediated membrane binding potently inhibits rFVIIIFc-mediated CD16 +NK cell activation, while targeting FVIII heavy chain domains does not. Our results suggest FVIII light chain-mediated membrane binding results in tethering of the fusion protein to the cell surface and allows for Fc-CD16 interactions to proceed, resulting in NK cellular activation. This working model may help explain our previous results where we observed recombinant Factor IX-Fc fusion protein and rFVIIIFc exhibited different CD16-signaling properties despite having identical IgG1 Fc domains.

Major cardiac surgery with recombinant FIX Fc fusion protein replacement in hemophilia B: a case report

The introduction of extended factor IX (FIX) products has significantly facilitated the treatment of hemophilia B patients. However, optimal perioperative management remains a topic of hot debate, particularly in surgeries with high bleeding risk. For the first time, we report here a patient with mild hemophilia B and degenerative aneurysms of aortic root and ascending aorta undergoing elective Bentall’s operation with full cardiopulmonary bypass, who was successfully managed with eftrenonacog alfa (Alprolix®), a recombinant FIX Fc fusion protein (rFIXFc). rFIXFc could safely be monitored using the Pathromtin SL aPTT-reagent. No significant bleeding was noted intraoperatively despite systemic heparinization as well as postoperatively. Higher doses of rFIXFc were inevitable to reach target FIX levels intraoperatively, whereas in the post-surgery setting stable FIX concentrations were maintained with only few rFIXFc injections facilitating fast wound healing and remobilization of the patient.

Pharmacodynamics of eftrenonacog-alfa (rFIX-Fc) in severe hemophilia B patients: A real-life study

Eftrenonacog-alfa is a recombinant factor IX-Fc fusion protein increasingly prescribed in hemophilia B patients. We aimed to assess its pharmacodynamics (PD) in real-life setting via FIX activity measurement and thrombin generation assay (TGA).Sixty samples from 15 severe hemophilia B treated patients were collected at different time points. FIX activity was measured using product-specific one-stage clotting assay (reference method) and two chromogenic assays (CSA) (Biophen FIX and Rox FIX). TGA was triggered with 1 pM tissue factor. Five parameters were analyzed: lag time (LT), time to peak (TTP), peak height (PH), endogenous thrombin potential (ETP), and velocity. PD models were built to characterize their relationships with FIX activity, using mixed effects models.Mean trough FIX level was estimated at 4.64 (±1.50) IU/dl with a recovery at 0.78 (±0.16) IU/dl per 1 IU/kg injected dose. FIX activity ranged between 1 and 86 IU/dl with 21.5 IU/dl median value. Biophen FIX and Rox FIX allowed reliable measurements except in samples with FIX <20 IU/dl in which values were underestimated (delta >30%). PD models revealed that velocity was the most sensitive TGA parameter to FIX activity followed by PH, ETP, TTP and finally LT. Following FIX activity peak after eftrenonacog-alfa injection, velocity decreased first, followed by PH then ETP.Both CSA failed to accurately measure FIX in severe hemophilia B patients receiving eftrenonacog-alfa throughout the measuring range. TGA could be an additional valuable tool to evaluate hemostasis balance in treated patients.

Clinical Outcomes in Children with Hemophilia B Treated Long Term with rFIXFc: Interim Results of the B-YOND Extension Study

Background: Early prophylactic replacement of coagulation factor IX (FIX) improves clinical outcomes in children with hemophilia B; however, frequent intravenous infusions (2-3 times/week) are often required due to the short half-life of conventional FIX products. Recombinant FIX Fc fusion protein (rFIXFc), which is produced in a human cell line, binds the neonatal Fc receptor and utilizes the natural IgG recycling pathway to prolong the half-life of FIX.The phase 3 Kids B-LONG study (NCT01425723) demonstrated the safety, efficacy and prolonged half-life of once weekly recombinant factor IX Fc fusion protein (rFIXFc) in children aged Methods: Upon completing Kids B-LONG, eligible subjects could participate in one of 3 treatment groups in B-YOND: weekly prophylaxis (WP; 20-100 IU/kg every 7 days), individualized prophylaxis (IP; 100 IU/kg every 8-16 days), or modified prophylaxis (MP; for subjects not achieving optimal prophylactic dosing with individualized or weekly prophylaxis). Subjects could change treatment groups at the start of or at any time during the study; for efficacy analyses, data were summarized according to the treatment group in which they participated, for the time period they were in that treatment group. The primary endpoint was development of inhibitors (neutralizing antibodies; confirmed at a central laboratory per Nijmegen-modified Bethesda assay result ≥0.6 BU/mL observed twice within 2-4 weeks). Secondary outcomes included incidence of adverse events (AEs), annualized bleeding rate (ABR), and rFIXFc exposure days (EDs). Post hoc analyses of subjects9 prophylactic dose and dosing interval were performed to evaluate the stability of prophylactic dosing regimens over time. Results: At the time of the B-YOND interim data cut (17 October 2014), 23 subjects had completed Kids B-LONG; all enrolled in B-YOND ( Conclusions: These data confirm the long-term safety of rFIXFc and the maintenance of a low ABR in children treated with extended-interval prophylaxis. Disclosures Kulkarni:Kedrion: Membership on an entity9s Board of Directors or advisory committees; Pfizer: Membership on an entity9s Board of Directors or advisory committees; Novo Nordisk: Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bayer: Membership on an entity9s Board of Directors or advisory committees, Research Funding; Baxter: Membership on an entity9s Board of Directors or advisory committees, Research Funding; Biogen: Research Funding, Speakers Bureau; BPL: Membership on an entity9s Board of Directors or advisory committees. Nolan:Biogen and Sobi: Research Funding. Fischer:Baxalta/Baxter, Bayer, Pfizer, Novo Nordisk, and Biogen: Consultancy; Baxalta/Baxter, Bayer, Pfizer, and Novo Nordisk: Research Funding; Baxalta/Baxter, Bayer, Pfizer, Novo Nordisk, CSL Behring, and Octopharma: Speakers Bureau. Perry:Biogen: Consultancy, Honoraria; Novo Nordisk: Consultancy, Membership on an entity9s Board of Directors or advisory committees. Barnes:Bayer, Novo Nordisk, and Pfizer: Research Funding; Bayer, Baxter, and Novo Nordisk: Membership on an entity9s Board of Directors or advisory committees. Yuan:Biogen: Employment, Equity Ownership. Ramirez-Santiago:Biogen: Employment, Equity Ownership. Pierce:Biogen: Equity Ownership, Other: Former employee. Mei:Biogen: Employment, Equity Ownership.

Extended-Interval Prophylaxis with rFIXFc in Adults and Adolescents with Hemophilia B: Interim Results of the B-YOND Extension Study

Extended-Interval Prophylaxis with rFIXFc in Adults and Adolescents with Hemophilia B: Interim Results of the B-YOND Extension Study

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.

Recombinant factor IX-Fc fusion protein (rFIXFc) demonstrates safety and prolonged activity in a phase 1/2a study in hemophilia B patients

AbstractCurrent factor IX (FIX) products display a half-life (t1/2) of ∼ 18 hours, requiring frequent intravenous infusions for prophylaxis and treatment in patients with hemophilia B. This open-label, dose-escalation trial in previously treated adult subjects with hemophilia B examined the safety and pharmacokinetics of rFIXFc. rFIXFc is a recombinant fusion protein composed of FIX and the Fc domain of human IgG1, to extend circulating time. Fourteen subjects received a single dose of rFIXFc; 1 subject each received 1, 5, 12.5, or 25 IU/kg, and 5 subjects each received 50 or 100 IU/kg. rFIXFc was well tolerated, and most adverse events were mild or moderate in intensity. No inhibitors were detected in any subject. Dose-proportional increases in rFIXFc activity and Ag exposure were observed. With baseline subtraction, mean activity terminal t1/2 and mean residence time for rFIXFc were 56.7 and 71.8 hours, respectively. This is ∼ 3-fold longer than that reported for current rFIX products. The incremental recovery of rFIXFc was 0.93 IU/dL per IU/kg, similar to plasma-derived FIX. These results show that rFIXFc may offer a viable therapeutic approach to achieve prolonged hemostatic protection and less frequent dosing in patients with hemophilia B. The trial was registered at www.clinicaltrials.gov as NCT00716716.