A novel B-domain O-glycoPEGylated FVIII (N8-GP) demonstrates full efficacy and prolonged effect in hemophilic mice models.

Frequent infusions of intravenous factor VIII (FVIII) are required to prevent bleeding associated with hemophilia A. To reduce the treatment burden, recombinant FVIII with a longer half-life was developed without changing the protein structure. FVIII-polyethylene glycol (PEG) conjugates were prepared using an enzymatic process coupling PEG (ranging from 10 to 80 kDa) selectively to a unique O-linked glycan in the FVIII B-domain. Binding to von Willebrand factor (VWF) was maintained for all conjugates. Upon cleavage by thrombin, the B-domain and the associated PEG were released, generating activated FVIII (FVIIIa) with the same primary structure and specific activity as native FVIIIa. In both FVIII- and VWF-deficient mice, the half-life was found to increase with the size of PEG. In vivo potency and efficacy of FVIII conjugated with a 40-kDa PEG (N8-GP) and unmodified FVIII were not different. N8-GP had a longer duration of effect in FVIII-deficient mouse models, approximately a twofold prolonged half-life in mice, rabbits, and cynomolgus monkeys; however, the prolongation was less pronounced in rats. Binding capacity of N8-GP on human monocyte-derived dendritic cells was reduced compared with unmodified FVIII, resulting in several-fold reduced cellular uptake. In conclusion, N8-GP has the potential to offer efficacious prevention and treatment of bleeds in hemophilia A at reduced dosing frequency.

Prolonged half-life of glycoPEGylated rFVIIa variants compared to native rFVIIa.

INTRODUCTION: Bleeding episodes in haemophilia patients with inhibitors are primarily treated with by-passing agents such as recombinant activated FVII (rFVIIa). Prophylactic treatment with rFVIIa has been shown to significantly reduce the number of bleeding episodes as compared to conventional on-demand haemostatic therapy, and a reduced dosing frequency could present an improved treatment option in inhibitor patients. MATERIALS AND METHODS: A series of glycoPEGylated rFVIIa derivatives (5-40K PEG) has been produced and their effect and pharmocokinetics have been investigated in several animal species. RESULTS: The glycoPEGylated rFVIIa derivatives exhibit significant prolongation of half-life in mice, dogs and pigs as measured by rFVIIa clot activity. The clearance of rFVIIa, rFVIIa-5K PEG, rFVIIa-10K PEG, rFVIIa-20K PEG and rFVIIa-40K PEG in minipigs were estimated to 59, 27, 22, 8.7 and 3.1 ml/h/kg, respectively. Across species a reduction in clearance as a function of the size of the attached PEG was observed. By allometric scaling, the compiled pharmacokinetics predicts a human half-life for rFVIIa-10K PEG and rFVIIa-40K PEG of approximately 7 and 12h, respectively. The rFVIIa-10K PEG and rFVIIa-40K PEG are efficacious in stopping a bleed in the haemophilia A mouse tail-bleeding model after intravenous administration. CONCLUSIONS: GlycoPEGylation of rFVIIa significantly increases the rFVIIa exposure in three animal models, glycoPEGylated rFVIIa compounds are effective in vivo and thus, represents a potential prophylactic treatment option for patients with inhibitors.

Prolonged effect of GlycoPEGylated rFVIIa (40k-PEG-rFVIIa) in rabbits correlates to activity in plasma.

The pharmacokinetics and pharmacodynamics of 40k-PEG-rFVIIa, a GlycoPEGylated derivative of recombinant wild-type FVIIa, were compared with rFVIIa in rabbits. The procoagulant effect was determined as the weight of the clot formed in a defined segment of a facial vein. A time course study was conducted where ligation was made 10 minutes, 12 or 24 hours after i.v. injection of equimolar doses of 40k-PEG-FVIIa or rFVIIa (2 mg/kg). This dose was selected based on a dose response study and a duration of effect study with rFVIIa. The clot weight increased with increasing doses of rFVIIa, and the duration of effect correlated with the plasma FVIIa clot activity. The plasma half-life of 40k-PEG-rFVIIa measured as FVIIa clot activity was found to be 25 hours, which was 5-6 times longer than rFVIIa. The aPTT and PT were reduced, and the measured increase in thrombin-antithrombin correlated to the effect on clot formation. Thus, the effect was similar at ligation 10 minutes after administration of 40k-PEG-rFVIIa or rFVIIa. At 12 hours, the effect of rFVIIa was absent while significant effect was seen 12 and 24 hours post dosing with 40k-PEG-rFVIIa. No consumption of platelets or fibrinogen was found and no thrombi formation was seen in histological examination of various organs. In conclusion, 40k-PEG-rFVIIa has shown prolonged duration of effect that correlated to various plasma markers and FVIIa clot activity. In perspective, the data support further clinical development of 40k-PEG-rFVIIa to potentially become a long-acting recombinant treatment option for prophylaxis in haemophilia patients with inhibitors.

Sequential autolytic processing activates the zymogen of Arg-gingipain.

Most proteases are synthesized as inactive precursors to protect the synthetic machinery of the cell and allow timing of activation. The mechanisms used to render latency are varied but tend to be conserved within protease families. Proteases belonging to the caspase family have a unique mechanism mediated by transitions of two surface loops, and on the basis of conservation of mechanism one would expect this to be preserved by caspase relatives. We have been able to express the full-length precursor of the Arg-specific caspase relative from the bacterium Porphyromonas gingivalis, Arg-gingipain-B, and we show that it contains N- and C-terminal extensions that render a low amount of latency, meaning that the zymogen is substantially active. Three sequential autolytic processing steps at the N and C terminus are required for full activity, and the N-propeptide may serve as an intramolecular chaperone rather than an inhibitory peptide. Each step in activation requires the previous step, and an affinity probe reveals that incremental activity enhancements are achieved in a stepwise manner.