Antidotes for factor Xa inhibitors and methods of using the same

1. A two-chain polypeptide comprising a first chain comprising (1) amino acid residues 1-105 of SEQ ID NO. 20 or (2) a first peptide having at least 95% sequence identity to amino acid residues 1-105 of SEQ ID NO. 20 and a second chain comprising (i) amino acid residues 112-346 of SEQ ID NO. 20 or (ii) a second peptide having at least 95% sequence identity to amino acid residues 112-346 of SEQ ID NO. 20, wherein the two-chain polypeptide (a) has reduced catalytic activity compared to wild-type factor Xa, (b) is capable of binding to a factor Xa inhibitor, and (c) does not assemble into a prothrombinase complex, and wherein the second chain does not include a β-peptide of wild-type factor Xa (amino acid residues 430-448 of SEQ ID NO. 3).

2. A two-chain polypeptide comprising a first chain comprising (1) the amino acid sequence of SEQ ID NO. 14 or (2) a first peptide having at least 95% sequence identity to SEQ ID NO. 14 and a second chain comprising (i) the amino acid sequence of SEQ ID NO. 15 or (ii) a second peptide having at least 95% sequence identity to SEQ ID NO. 15, wherein the two-chain polypeptide (a) has reduced catalytic activity compared to wild-type factor Xa, (b) is capable of binding to a factor Xa inhibitor, and (c) does not assemble into a prothrombinase complex, and wherein the first chain further comprises a modification at an EGF 1 domain (amino acid residues 12-50 of SEQ ID NO. 14) or an EGF2 domain (amino acid residues 51-94 of SEQ ID NO. 14).

3. The two-chain polypeptide of claim 2 , wherein the modification is selected from the group consisting of a deletion of substantially all of the EGF1 domain, a deletion of substantially all of the EGF2 domain, and combinations thereof.

4. The two-chain polypeptide of claim 3 , wherein the deletion of substantially all of the EGF1 domain comprises deletion of at least about 50% of the EGF1 domain.

5. The two-chain polypeptide of claim 3 , wherein the deletion of substantially all of the EGF1 domain comprises deletion of at least about 80% of the EGF1 domain.

6. The two-chain polypeptide of claim 3 , wherein the deletion of substantially all of the EGF2 domain comprises deletion of at least about 50% of the EGF2 domain.

7. The two-chain polypeptide of claim 3 , wherein the deletion of substantially all of the EGF2 domain comprises deletion of at least about 80% of the EGF2 domain.

8. A two-chain polypeptide comprising a first chain comprising (1) the amino acid sequence of SEQ ID NO. 14 or (2) a first peptide having at least 95% sequence identity to SEQ ID NO. 14 and a second chain comprising (i) the amino acid sequence of SEQ ID NO. 15 or (ii) a second peptide having at least 95% sequence identity to SEQ ID NO. 15, wherein the two-chain polypeptide (a) has reduced catalytic activity compared to wild-type factor Xa, (b) is capable of binding to a factor Xa inhibitor, and (c) does not assemble into a prothrombinase complex, and wherein the second chain further comprises a modification at an autolysis loop (amino acid residues 132-142 of SEQ ID NO. 15).

9. The two-chain polypeptide of claim 8 , wherein the modification comprises mutating either Arg366 (amino acid residue 132 of SEQ ID NO. 15), Lys370 amino acid residue 136 of SEQ ID NO. 15), Arg372 (amino acid residue 138 of SEQ ID NO. 15), Arg376 (amino acid residue 142 of SEQ ID NO. 15) or combinations thereof to Gln (Q) or Ala (A).

10. A method of neutralizing or reversing anticoagulation in a subject undergoing anticoagulant therapy with a factor Xa inhibitor in need of cessation of anticoagulation or suffering from bleeding, comprising administering to the subject an effective amount of the two-chain polypeptide of claim 1 .

11. The method of claim 10 , wherein the factor Xa inhibitor is selected from the group consisting of fondaparinux, idraparinux, biotinylated idraparinux, enoxaparin, fragmin, NAP-5, rNAPc2, tissue factor pathway inhibitor, DX-9065a, YM-60828, YM-150, apixaban, rivaroxaban, PD-348292, otamixaban, edoxaban, LY517717, GSK913893, razaxaban, low molecular weight heparin and betrixaban,. or a pharmaceutically acceptable salt thereof, and combinations thereof.

12. The method of claim 10 , wherein the subject is experiencing a clinical major bleeding event selected from the group consisting of hemorrhage, bleeding into a vital organ, bleeding requiring re-operation or a new therapeutic procedure, and a bleeding index of equal to or more than 2.0 with an associated overt bleeding.

13. The method of claim 10 , wherein the composition is administered prior to a surgery.

14. A method for selectively binding and inhibiting an exogenously administered factor Xa inhibitor in a subject, comprising administering to the subject an effective amount of the two-chain polypeptide of claim 1 .

15. The method of claim 14 , wherein the factor Xa inhibitor is selected from the group consisting of fondaparinux, idraparinux, biotinylated idraparinux, enoxaparin, fragmin, NAP-5, rNAPc2, tissue factor pathway inhibitor, DX-9065a, YM-60828, YM-150, apixaban, rivaroxaban, PD-348292, otamixaban, edoxaban, LY517717, GSK913893, razaxaban, low molecular weight heparin and betrixaban,. or a pharmaceutically acceptable salt thereof, and combinations thereof.

16. The method of claim 14 , wherein the subject is experiencing a clinical major bleeding event selected from the group consisting of hemorrhage, bleeding into a vital organ, bleeding requiring re-operation or a new therapeutic procedure, and a bleeding index of equal to or more than 2.0 with an associated overt bleeding.

17. The method of claim 16 , wherein the composition is administered prior to a surgery.