N-GLYCAN SIALYLATION IS IMPORTANT FOR IN VIVO RECOVERY OF RECOMBINANT FACTOR IX

Coagulation Factor IX is a single chain glycoprotein (mol wt ~55,000) consisting of multiple structural domains that are important for procoagulant activity. Numerous posttranslational modifications are known to occur, but only gamma-carboxylation has been clearly shown to be essential for procoagulant activity. However, other post-translational modifications may be important for recovery of Factor IX in vivo following intravenous infusion. For example, Tyr155 is >90% sulfated in plasma derived Factor IX, compared to only 10-15% in recombinant Factor IX. Reduced sulfation has been proposed to explain the reduced in vivo recovery of recombinant Factor IX in several animal models as well as in humans. Unpublished work has also provided circumstantial evidence that improving recombinant Factor IX sulfation may correlate with improved in vivo recovery. The present study was undertaken to investigate the observation that low molecular weight forms of recombinant Factor IX could be produced in cell culture that appeared to have good in vitro procoagulant activity, but low in vivo recovery (bioavailability). N-Glycan Sialylation is Important for In Vivo Recovery of Recombinant Factor IX