The present invention relates to modified cDNA sequences coding for vitamin K-dependent polypeptides, in particular human Factor VII, human Factor VIIa, human Factor IX and human protein C and their derivatives with improved stability and extended plasma half life, recombinant expression vectors containing such cDNA sequences, host cells transformed with such recombinant expression vectors, recombinant polypeptides and derivatives which do have biological activities of the unmodified wild type protein but having improved stability and processes for the manufacture of such recombinant proteins and their derivatives. The invention also covers a transfer vector for use in human gene therapy, which comprises such modified DNA sequences.