Enhancement of haemostatic efficacy of plasma-derived FVIII by formulation with PEGylated liposomes.

We have shown previously that PEGylated liposomes (PEGLip) bind recombinant FVIII (rFVIII) with high affinity and specificity. This binding resulted in a significant extension of the biological activity of rFVIII as demonstrated in animal models and in clinical trials. In the present study we found that PEGLip bind plasma-derived factor VIII (pdFVIII). PEGLip binding did not affect potency or stability in vitro and did not alter levels of FVIII activity in vivo immediately after injection. However, formulation of pdFVIII with PEGLip led to several important improvements. Twenty-four and 30 hours after injection, FVIII activity levels were significantly higher in haemophilic mice injected with PEGLip-pdFVIII than in mice injected with standard pdFVIII. Half life, area under the curve and mean residence time were increased while clearance was decreased. In vivo efficacy was evaluated in a tail vein transection assay performed in haemophilic mice. Prophylactic treatment with PEGLip-pdFVIII was much more effective in prolonging survival in this assay than similar treatment with standard pdFVIII. These results suggest that formulation of pdFVIII with PEGLip has the potential to improve patient care by prolonging the biological efficacy of pdFVIII and reducing the frequency of FVIII infusions.