603997 Disclosed is a blood coagulation factor IX (FIX) with a FIX activation peptide region (AP region), wherein said AP region comprises a covalently coupled water-soluble hydrophilic polymer absent from biologically produced FIX, said covalently coupled water-soluble hydrophilic polymer being polysialic acid (PSA) attached to said FIX via Asn-157 and/or Asn-167 of said FIX. Further disclosed is a method for the preparation of a blood coagulation factor IX (FIX) with a FIX activation peptide region (AP region), wherein said AP region comprises a covalently coupled water-soluble hydrophilic polymer absent from biologically produced FIX, said covalently coupled water-soluble hydrophilic polymer being polysialic acid (PSA) attached to said FIX via Asn-157 and/or Asn-167 of said FIX, said method comprising the following steps: providing said FIX molecule comprising said FIX activation peptide region (AP region) covalently coupling said water-soluble hydrophilic polymer to said AP region and isolating said FIX with said covalently coupled water-soluble hydrophilic polymer in said AP region.
