Factor VIII with a 237 amino acid B-domain has an extended half-life in F8-knockout mice.

Essentials Factor (F)VIII with an intermediate-length B-domain showed higher levels in murine gene therapy. FVIII with different B-domain lengths were analysed. FVIII variants with B-domains between 186 and 240 amino acids (aa) have extended half-life in mice. Reduced cell binding of FVIII with a 237aa B-domain may explain the extended half-life. SUMMARY: Background Factor VIII consists of the A1-domain, A2-domain, B-domain, A3-domain, C1-domain, and C2-domain. FVIII with an intermediate-length B-domain of 226 amino acids (aa) has previously been evaluated in murine gene therapy studies. Objective To characterize FVIII with intermediate-length B-domains in vitro and in vivo in F8-knockout (KO) mice. Methods and results FVIII molecules with B-domains of 186-240aa had longer half-lives in F8-KO mice than FVIII molecules with shorter or longer B-domains. FVIII with a B-domain containing the 225 N-terminal aa fused to the 12 C-terminal aa of the wild-type B-domain (FVIII-237) had a 1.6-fold extended half-life in F8-KO mice as compared with FVIII with a 21aa B-domain (FVIII-21). The in vitro and in vivo activity of FVIII-237 were comparable to those of FVIII-21, as was binding to von Willebrand factor. Cell binding to LDL receptor-related protein 1 (LRP-1)-expressing cells was markedly reduced for FVIII-237 as compared with FVIII-21, whereas the affinity for LRP-1 was not reduced in surface plasmon resonance (SPR) studies. FVIII-21 cell binding and internalization could be inhibited by a fragment consisting of the 226 N-terminal aa of the FVIII B-domain, and SPR analysis suggested that this B-domain fragment might bind with weak affinity to FVIII-21. Conclusion Reduced cell binding of FVIII-237 might explain the observed extended half-life in F8-KO mice. This may contribute to the increased FVIII levels measured in murine gene therapy studies using FVIII constructs with similar B-domain lengths.

Preclinical pharmacokinetics and biodistribution of subcutaneously administered glycoPEGylated recombinant factor VIII (N8-GP) and development of a human pharmacokinetic prediction model.

Essentials N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous (SC) FVIII dosing might reduce the treatment burden of prophylaxis. SC N8-GP has a favorable PK profile in animal models and disappears from skin injection sites. Combined animal (SC) and clinical (IV) data suggest that daily SC dosing may provide prophylaxis. SUMMARY: Background N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous administration of FVIII may reduce the treatment burden of prophylaxis; however, standard FVIII products have low bioavailability after subcutaneous dosing in animals. Objective To evaluate the pharmacokinetics, effectiveness and local distribution of subcutaneously administered N8-GP in preclinical models and predict the human pharmacokinetic (PK) profile. Methods The pharmacokinetics of subcutaneously administered N8-GP were evaluated in FVIII knockout (F8-KO) mice and cynomolgus monkeys; a human PK prediction model in hemophilia A patients was developed. The hemostatic effect was evaluated in a tail vein bleeding model in F8-KO mice. The injection-site distribution and absorption of subcutaneously administered N8-GP were assessed in F8-KO mice by the use of temporal fluorescence imaging and immunohistochemistry. Results Subcutaneously administered N8-GP had a bioavailability, a first-order absorption rate and a half-life, respectively, of 24%, 0.094 h-1 and 14 h in F8-KO mice, and 26%, 0.33 h-1 and 15 h in cynomolgus monkeys. A dose-dependent effect of subcutaneously administered N8-GP on blood loss was observed in mice. A minimal amount of N8-GP was detected at the injection site 48-72 h after single or multiple dose(s) in F8-KO mice. Subcutaneously administered N8-GP was localized to the skin around the injection site, with time-dependent disappearance from the depot. PK modeling predicted that subcutaneously administered N8-GP at a daily dose of 12.5 IU kg-1 will provide FVIII trough levels of 2.5-10% in 95% of patients with severe hemophilia A. Conclusions Subcutaneously administered N8-GP may provide effective hemophilia A prophylaxis. A phase I clinical trial is underway to investigate this possibility.

High-affinity von Willebrand factor binding does not affect the anatomical or hepatocellular distribution of factor VIII in rats.

UNLABELLED: Essentials Von Willebrand factor (VWF) stabilizes factor VIII (FVIII) and prevents its premature clearance. Rat anatomical and hepatocellular distribution studies assessed the VWF effect on FVIII clearance. Hepatocytes and liver sinusoidal endothelial cells play a key role in FVIII clearance. Anatomical and hepatocellular distribution of FVIII is independent of high-affinity VWF binding. ABSTRACT: Background Von Willebrand factor (VWF) stabilizes factor VIII in the circulation and prevents its premature clearance. Objective To study the effects of VWF on FVIII clearance in rats with endogenous VWF. Methods Anatomical and hepatocellular distribution studies were performed in rats following intravenous administration of glycoiodinated recombinant FVIII (rFVIII) and a FVIII variant, FVIII-Y1680F, lacking high-affinity VWF binding. Radioactivity was quantified in organs, and in distinct liver cell populations. The role of VWF binding was also studied by immunohistochemical staining of rat livers perfused ex vivo with rFVIII alone or with a FVIII-binding VWF fragment. Results The liver was the predominant organ of rFVIII distribution, and a radioactivity peak was also observed in the intestines, suggesting FVIII secretion to the bile by hepatocytes. In the liver, ~60% of recovered radioactivity was associated with hepatocytes, 32% with liver sinusoidal endothelial cells (LSECs), and 9% with Kupffer cells (KCs). When calculated per cell, 1.5-fold to 3-fold more radioactivity was associated with LSECs than with hepatocytes. The importance of hepatocytes and LSECs was confirmed by immunohistochemical staining; strong staining was seen in LSECs, and less intense, punctate staining in hepatocytes. Minor staining in KCs was observed. Comparable anatomical and hepatocellular distributions were observed with rFVIII and FVIII-Y1680F, and the presence of the VWF fragment, D'D3A1, did not change the FVIII staining pattern in intact livers. Conclusions The present data support FVIII clearance via the liver, with hepatocytes and LSECs playing a key role. High-affinity VWF binding did not alter the anatomical or hepatocellular distribution of FVIII.

Pharmacokinetics and pharmacodynamics of a new recombinant FVIII (N8) in haemophilia A mice.

N8 is a new recombinant factor VIII (rFVIII) compound produced and formulated without human- or animal-derived protein. The aims of the present studies were to evaluate the pharmacokinetics and pharmacodynamics properties of N8 and to compare with a commercially available rFVIII product (Advate(®)) in haemophilia A mice. The pharmacokinetics were evaluated after single i.v. administration of 80, 120 and 280 IU kg(-1) of N8 and Advate(®) and measurements of FVIII blood concentrations as a function of time. The efficacy and dose response curves of N8 and Advate(®) (1-200 IU kg(-1)) were evaluated in a tail bleeding model. Furthermore, the effects in a newly developed haemophilia knee joint haemarthrosis model were investigated. No significant differences were found in the pharmacokinetic parameters between N8 and Advate(®). The clearances were 11 ± 1 vs. 10 ± 2 mL h(-1) kg(-1) (P = 0.14) and the half-lives 7.2 ± 0.9 vs. 7.7 ± 1.4 h (P = 0.31) after administration of N8 and Advate(®) respectively. Dose-independent pharmacokinetics was shown, and comparable efficacy and potency were shown between N8 and Advate(®) in the tail bleeding model. Both compounds normalized the bleeding at the dose of 200 IU kg(-1), and for blood loss ED(50) values of 27 IU kg(-1) (N8) and 28 IU/kg (Advate(®)) were found (P = 0.97). In the haemarthrosis model, treatment with N8 and Advate(®) at 200 IU kg(-1) reduced the mean increase in the joint diameter significantly from 1.23 ± 0.19 to 0.32 ± 0.08 mm (P < 0.01) and 0.25 ± 0.08 mm (P < 0.001) respectively. Pharmacokinetics and pharmacodynamics of N8 and Advate(®) were comparable after i.v. administration to haemophilia A mice.

Pharmacokinetics and ex vivo whole blood clot formation of a new recombinant FVIII (N8) in haemophilia A dogs.

N8, a new recombinant factor VIII (rFVIII) compound developed for the treatment of haemophilia A, is produced in Chinese hamster ovary (CHO) cells and formulated without human- or animal-derived materials. The aim of the present study was to compare the pharmacokinetics (PK) and the procoagulant effect, measured by ex vivo whole blood clot formation, of N8 and a commercial rFVIII in a cross-over study in haemophilia A dogs. N8 and Advate® (100 IU kg⁻¹) were administered intravenously to three haemophilia A dogs. Blood was sampled between 0 and 120 h postdose and FVIII:C analysed. PK parameters maximum plasma concentration, area under the curve, half-life (t(½)), clearance, mean residence time (MRT) and volume of distribution and incremental recovery were calculated. Whole blood clotting time (WBCT) and thromboelastography (TEG®) were used to determine the haemostatic potential. No adverse reactions were observed with N8 or Advate ®. N8 and Advate® exhibited similar PK parameters, with t(½) 7.7-11 h and MRT 11-14 h. Both rFVIII compounds corrected the prolonged WBCT (> 48 min) to the range of normal dogs (8-12 min), i.e. N8 to 7.5-10.5 min and Advate® to 7.5-11.5 min. N8 and Advate® also normalized the whole blood clot formation according to TEG®. The native whole blood clotting assays (WBCT, TEG®) appeared to be more sensitive to low concentrations of FVIII than assays in citrated plasma samples. In conclusion, comparison of N8 and Advate ® in haemophilia A dogs revealed similar safety, similar PK and similar effects in whole blood clot formation assays.

In vivo clearance and metabolism of recombinant activated factor VII (rFVIIa) and its complexes with plasma protease inhibitors in the liver.

INTRODUCTION: Recombinant activated factor VII (rFVIIa, NovoSeven®) is injected intravenously for the treatment of haemophilia patients with inhibitory antibodies. In plasma, rFVIIa forms complexes with protease inhibitors, primarily antithrombin III (ATIII). The liver is believed to be involved in clearance of rFVIIa, however, it is not known whether the liver is also involved for the clearance of the rFVIIa-ATIII complex. In this study, we explored the fate of intravenously injected rFVIIa from plasma to the hepatic lysosomes. MATERIALS AND METHODS: A novel method using magnetic chromatography was used to isolate catabolic organelle (CO) fractions from mouse liver following injection of superparamagnetic dextran (SPD)-coated iron oxide particles and rFVIIa. The effect of co-circulating SPD particles on rFVIIa pharmacokinetic (PK) parameters was evaluated by ELISA. Cryo-immuno transmission electron microscopy (TEM) was used to study hepatic distribution of SPD particles and rFVIIa. The isolated hepatic CO fractions were characterized using Western Blotting (WB). RESULTS: Cryo-immuno TEM of the liver confirmed hepatic co-localisation of SPD particles and rFVIIa in identical endosomes and lysosomes of both hepatocytes and Kupffer cells. SPD particles did not affect the PK parameters of rFVIIa. WB analysis of plasma and CO fractions detected rFVIIa as the full-length protein and also in high molecular weight (HMW) complexes with ATIII and α-2 macroglobulin (α-2M). CONCLUSIONS: Following injection, both hepatocytes and Kupffer cells appeared to be involved in the hepatic clearance and metabolism of both full-length rFVIIa and rFVIIa in complex with at least two plasma protease inhibitors; ATIII and α-2M.

Effect of ketoprofen and its enantiomers on the renal disposition of methotrexate in the isolated perfused rat kidney.

Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to inhibit the renal tubular secretion of methotrexate. However, the relative contribution of the active S- and inactive R-enantiomers is unknown. This study examined the effect of racemic ketoprofen and its enantiomers on the renal disposition of methotrexate in the isolated perfused rat kidney (IPK). Nineteen kidneys were divided between a control and three treatment groups. Controls were perfused with methotrexate alone (25 micrograms mL-1, n = 5) over three 30-min periods. Treatment groups were perfused with methotrexate (25 micrograms m-1) for the first period, followed by a second period of methotrexate (25 micrograms mL-1) plus R- (n = 5), S- (n = 5) or RS-ketoprofen (n = 4) at 25 micrograms mL-1, and a third period of methotrexate (25 micrograms mL-1) plus R-, S- or RS-ketoprofen (50 micrograms mL-1). Perfusate and urine were collected over 10-min intervals. Methotrexate was measured by HPLC and its binding in perfusate by ultrafiltration. The clearance ratio (CR) for methotrexate was obtained by dividing the renal clearance by the product of its fraction unbound and the glomerular filtration rate. During control experiments, there was no significant change in the CR over 90 min. R-, S- and RS-ketoprofen at 50 micrograms mL-1 reduced the CR of methotrexate significantly, but there was no difference between the three groups. While the enantiomers of ketoprofen reduced the renal excretion of methotrexate, the interaction was not enantioselective.