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- Brophy, D F, et al.
(författare)
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Monitoring rFVIIa 90 μg kg(-1) dosing in haemophiliacs: comparing laboratory response using various whole blood assays over 6 h.
- 2011
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Ingår i: Haemophilia. - : Wiley. - 1351-8216. ; 17:5, s. 949-957
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Tidskriftsartikel (refereegranskat)abstract
- Summary. Recombinant FVIIa is a haemostatic agent administered to patients with severe FVIII or FIX deficiency with inhibitors. Although rFVIIa is effective at stopping bleeding, a reliable assay to monitor its effect is lacking. To characterize the pharmacokinetics and global coagulation effects of rFVIIa for 6 h following a IV dose of 90 μg kg(-1) . Ten non-bleeding subjects with severe FVIII or FIX deficiency were infused with a single-dose of rFVIIa 90 μg kg(-1) body weight and blood was collected before and at 0.5, 1, 2, 4 and 6 h postdose. Global haemostasis was characterized throughout the study utilizing whole blood analyses (Hemodyne HAS, TEG, ROTEM). The clearance and half-life of factor FVII:C was estimated as 39.0 ± 8.8 mL h(-1) kg(-1) and 2.1 ± 0.2 h respectively. There was good inter-assay agreement with respect to clot initiation parameters (R, CT and FOT) and these parameters all fell to a mean of approximately 9 min following rFVIIa dosing. The platelet contractile force (PCF) and clot elastic modulus (CEM) were positively correlated to FVII:C (P < 0.0001), and these parameters were dynamic throughout the 6-h period. The MA and MCF did not correlate to FVII:C nor did they significantly change during the study. Prothrombin F1 + 2 significantly increased following rFVIIa dosing (P < 0.001), but remained steady throughout the study. There was no change in D-dimer concentrations over time. The FOT, R and CT characterized clot initiation following rFVIIa dosing. The PCF and CEM were correlated to FVII:C and characterized the dynamics of platelet function and clot strength over the rFVIIa dosing interval. The clinical significance of these findings needs additional study.
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| 2. |
- Agersø, H, et al.
(författare)
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Recombinant human factor VIIa (rFVIIa) cleared principally by antithrombin following IV administration in haemophilia patients.
- 2011
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 9:2, s. 333-338
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The objective of the present study was to evaluate the pharmacokinetics and the clearance pathways of rFVIIa after intravenous administration to haemophilia patients. Methods: Ten severe haemophilia patients were included in the study; all patients were intravenously administered a clinical relevant dose of 90 μg/kg (1.8 nmol/kg) rFVIIa. Blood samples were collected consecutively to describe the pharmacokinetics of rFVIIa. All samples were analysed using three different assays: a clot assay to measure the activity (FVIIa:C), an enzyme immunoassay (EIA) to measure the antigen levels (FVII:Ag), and a EIA (FVIIa-AT) to measure the FVIIa antithrombin III (AT) complex. Pharmacokinetic parameters were evaluated both by use of standard non-compartmental methods and by use of mixed effects methods. A population pharmacokinetic model was used to simultaneously model all three datasets. The total body clearance of rFVIIa:C was estimated to be 38 mL/h/kg. The rFVII:AT complex formation was responsible for 65% of the total rFVIIa:C clearance. The initial and the terminal half-life of rFVIIa:C was estimated to be 0.6 and 2.6 hours, respectively. The formation of rFVII-AT complex were able to explain the difference observed between the rFVIIa:C and the rFVII:Ag concentration. The non-compartmental analysis resulted in almost identical parameters.
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| 3. |
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| 5. |
- Lauritzen, B, et al.
(författare)
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Recombinant human factor VIIa and a factor VIIa-analogue reduces heparin and low molecular weight heparin (LMWH)-induced bleeding in rats
- 2008
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 6:5, s. 804-811
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Tidskriftsartikel (refereegranskat)abstract
- Background: Heparin and low molecular weight heparin (LMWH) are widely used for prevention and treatment of thromboemobolic events, but may occasionally cause uncontrollable bleeding. Heparin can readily be antagonized with protamine, but this is less effective against LMWH. Objectives: To test the effects of rFVIIa or an analogue of rFVIIa, NN1731, on heparin- and LMWH-induced bleeding in rats. Methods: Initially the doses of heparin and tinzaparin (a LMWH) were determined by dose-titration. Following pretreatment with heparin or tinzaparin in rats, tail-transection was performed, and the effect of rFVIIa and NN1731 on the bleeding was observed. Results: rFVIIa (5, 10 and 20 mg kg(-1)) reduced bleeding time and blood loss caused by heparin- and tinzaparin-induced bleeding, using doses of 200 IU kg(-1) (n = 8) and 500 IU kg(-1) (n = 9), respectively. Similarly, 10 mg kg(-1) NN1731 significantly reduced both heparin- and tinzaparin-induced bleeding to the normal level. Following severe anticoagulation with 1800 IU kg(-1) tinzaparin, 10 mg kg(-1) NN1731 reduced and normalized the bleeding, while the effect of 20 mg kg(-1) rFVIIa failed to reach statistical significance. These data are consistent with the hypothesis that rFVIIa/NN1731 are capable of generating sufficient thrombin locally on the surface of activated platelets to induce hemostasis in the presence of heparin/LMWH. Conclusions: This study suggests that rFVIIa and NN1731 may have the potential to control bleedings caused by heparin or LMWH.
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| 6. |
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| 7. |
- Bowyer, A. E., et al.
(författare)
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Measuring factor IX activity of nonacog beta pegol with commercially available one-stage clotting and chromogenic assay kits : A two-center study
- 2016
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 14:7, s. 1428-1435
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Tidskriftsartikel (refereegranskat)abstract
- Essentials: Validated assays are required to precisely measure factor IX (FIX) activity in FIX products. N9-GP and two other FIX products were assessed in various coagulation assay systems at two sites. Large variations in FIX activity measurements were observed for N9-GP using some assays. One-stage and chromogenic assays accurately measuring FIX activity for N9-GP were identified. Summary: Background: Measurement of factor IX activity (FIX:C) with activated partial thromboplastin time-based one-stage clotting assays is associated with a large degree of interlaboratory variation in samples containing glycoPEGylated recombinant FIX (rFIX), i.e. nonacog beta pegol (N9-GP). Validation and qualification of specific assays and conditions are necessary for the accurate assessment of FIX:C in samples containing N9-GP. Objectives: To assess the accuracy of various one-stage clotting and chromogenic assays for measuring FIX:C in samples containing N9-GP as compared with samples containing rFIX or plasma-derived FIX (pdFIX) across two laboratory sites. Methods: FIX:C, in severe hemophilia B plasma spiked with a range of concentrations (from very low, i.e. 0.03 IU mL-1, to high, i.e. 0.90 IU mL-1) of N9-GP, rFIX (BeneFIX), and pdFIX (Mononine), was determined at two laboratory sites with 10 commercially available one-stage clotting assays and two chromogenic FIX:C assays. Assays were performed with a plasma calibrator and different analyzers. Results: A high degree of variation in FIX:C measurement was observed for one-stage clotting assays for N9-GP as compared with rFIX or pdFIX. Acceptable N9-GP recovery was observed in the low-concentration to high-concentration samples tested with one-stage clotting assays using SynthAFax or DG Synth, or with chromogenic FIX:C assays. Similar patterns of FIX:C measurement were observed at both laboratory sites, with minor differences probably being attributable to the use of different analyzers. Conclusions: These results suggest that, of the reagents tested, FIX:C in N9-GP-containing plasma samples can be most accurately measured with one-stage clotting assays using SynthAFax or DG Synth, or with chromogenic FIX:C assays.
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| 8. |
- Ostergaard, Henrik, et al.
(författare)
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Prolonged half-life and preserved enzymatic properties of factor IX selectively PEGylated on native N-glycans in the activation peptide
- 2011
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 118:8, s. 2333-2341
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Tidskriftsartikel (refereegranskat)abstract
- Current management of hemophilia B entails multiple weekly infusions of factor IX (FIX) to prevent bleeding episodes. In an attempt to make a longer acting recombinant FIX (rFIX), we have explored a new releasable protraction concept using the native N-glycans in the activation peptide as sites for attachment of polyethylene glycol (PEG). Release of the activation peptide by physiologic activators converted glycoPEGylated rFIX (N9-GP) to native rFIXa and proceeded with normal kinetics for FXIa, while the Km for activation by FVIIa-tissue factor (TF) was increased by 2-fold. Consistent with minimal perturbation of rFIX by the attached PEG, N9-GP retained 73%-100% specific activity in plasma and whole-blood-based assays and showed efficacy comparable with rFIX in stopping acute bleeds in hemophilia B mice. In animal models N9-GP exhibited up to 2-fold increased in vivo recovery and a markedly prolonged half-life in mini-pig (76 hours) and hemophilia B dog (113 hours) compared with rFIX (16 hours). The extended circulation time of N9-GP was reflected in prolonged correction of coagulation parameters in hemophilia B dog and duration of effect in hemophilia B mice. Collectively, these results suggest that N9-GP has the potential to offer efficacious prophylactic and acute treatment of hemophilia B patients at a reduced dosing frequency. (Blood. 2011; 118(8): 2333-2341)
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