Coagulation factor X polypeptides with modified activation properties
The present invention relates to modified cDNA sequences coding for human Factor X and their derivatives with improved stability and modified activation sequences, recombinant expression vectors containing such cDNA sequences, and host cells transformed with such recombinant expression vectors. The invention also relates to recombinant factor X polypeptides and derivatives which have biological activities of the unmodified wild type protein but with 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.
1. A modified biologically active recombinant factor X variant comprising a factor X polypeptide, wherein the factor X polypeptide comprises the factor X heavy chain sequence of SEQ ID NO: 2, with the addition of one or more cleavage sites for a protease inserted into the factor X heavy chain sequence between at least one set of amino acids selected from the group consisting of amino acids Ile235 and Val236, amino acids Val236 and Gly237 and amino acids Gly237 and Gly238, wherein the modified factor X variant is activated upon cleavage of the one or more inserted cleavage sites by the protease, and wherein the modified factor X variant has factor X clotting activity.
2. The modified biologically active recombinant factor X variant of claim 1 , wherein a protease that cleaves the one or more cleavage sites does not activate wild-type factor X.
3. The modified biologically active recombinant factor X variant of claim 1 , further comprising a factor X activation peptide that has been modified, wherein the modification renders the modified factor X variant comprising the modified factor X activation peptide resistant to cleavage and activation by proteases that cleave and activate wild-type factor X, wherein the modified factor X activation peptide comprises Ser183 to Arg234 of SEQ ID NQ: 2 with a mutation of at least one of amino acids Leu232 and Thr233.
4. The modified biologically active recombinant factor X variant of claim 1 , wherein the one or more inserted cleavage sites are for a serine protease.
5. The modified biologically active recombinant factor X variant of claim 4 , wherein the one or more inserted cleavage sites are for factor IIa, factor IXa, factor Xa, factor XIa, factor XIIa, activated protein C, elastase, or kallikrein.
6. The modified biologically active recombinant factor X variant of claim 1 , wherein the one or more inserted protease cleavage sites each encompass at least 3 amino acids.
7. A pharmaceutical composition comprising the modified biologically active recombinant factor X variant of claim 1 .
8. The modified biologically active recombinant factor X variant of claim 1 , wherein the one or more inserted cleavage sites are the only modification as compared to the wild-type factor X sequence.
9. The modified biologically active recombinant factor X variant of claim 1 , wherein the inserted protease cleavage site is between the factor X heavy chain amino acids Ile235 and Val236, wherein the factor X heavy chain amino acids Leu232 and Thr233 are each replaced with Asp, and wherein the inserted protease cleavage site and the Leu232Asp and Thr233Asp mutations are the only modifications as compared to the wild-type factor X sequence.