Method for purifying transgenic factor VII/VIIA
An anti-Factor VII affinity ligand that is particularly useful for purifying recombinant human activated Factor VII from transgenic sources. The affinity ligand combined with other orthogonal chromatographic steps allows the preparation of a highly purified FVII solution fully activated free of aggregates with a low percentage of degraded or oxidized FVII forms.
1. A method for purifying human transgenic Factor VII (TgFVII) and/or human transgenic activated Factor VII (TgFVIIa) produced in milk of a transgenic female rabbit, comprising the steps of:
(a) affinity chromatography, comprising
(i) contacting the milk containing human TgFVII and/or human TgFVIIa with a ligand which is specific to human TgFVII and/or human TgFVIIa, under conditions allowing the human TgFVII and/or human TgFVIIa to bind the ligand, and
(ii) eluting human TgFVII and/or human TgFVIIa by disrupting the interaction with said ligand, wherein TgFVII and/or TgFVIIa activity is retained,
wherein the ligand is an antigen-binding protein directed to at least one human TgFVII or human TgFVIIa epitope, the ligand is devoid of light polypeptide chains, and the ligand is obtained from heavy immunoglobulin chains of Camelidae;
(b) chromatographic purification of the eluted human TgFVII and/or human TgFVIIa on an ion exchanger, under conditions wherein human TgFVII and/or human TgFVIIa are retained on the ion exchanger;
(c) chromatographic separation of the eluted human TgFVII and/or human TgFVIIa on pseudo-affinity resin, under conditions wherein human TgFVII and/or human TgFVIIa are retained on the pseudo-affinity resin; and
(d) chromatographic separation of the eluted human TgFVII and/or human TgFVIIa on a size exclusion support.
2. The method of claim 1 , wherein said ligand comprises two heavy polypeptide chains forming two complete antigen binding sites.
3. The method of claim 1 , wherein step (a) further comprises at least one washing step for removing unbound material and weakly bound material before step (ii) eluting the human TgFVII or human TgFVIIa from the ligand.
4. The method of claim 1 , further comprising preliminary steps, before step (a), of collecting and clarifying the milk.
5. The method of claim 4 , wherein the clarifying the milk step is performed by citrate salt addition, followed by filtration.
6. The method of claim 1 , further comprising at least one step of eliminating and/or inactivating viruses.
7. The method of claim 1 , further comprising steps of formulating, sterilizing and lyophilizing the purified human TgFVII and/or human TgFVIIa.
8. The method of claim 3 , wherein the at least one washing step is performed with a buffer comprising from 10% to 50% of a hydrophobic agent, the ionic strength of which ranges from 200 to 600 mM.
9. The method of claim 3 , wherein, eluting the human TgFVII and/or human TgFVIIa from the resin is performed with a buffer comprising from 20% to 70% of a hydrophobic agent, the ionic strength of which ranges from 500 to 2500 mM.
10. The method of claim 1 , wherein the resulting purified human transgenic FVII is activated, high purity human FVII, comprising a low percentage of degraded, proteolyzed or oxidized forms.
11. The method of claim 1 , wherein the method achieves a viral reduction factor superior to 3 log 10 , superior to 4 log 10 , or superior to 5 log 10 .
12. The method of claim 1 , wherein the ion exchanger is an anion exchanger.
13. The method of claim 1 , wherein the pseudo-affinity resin is hydroxyapatite.
14. The method of claim 6 , wherein the at least one step of eliminating and/or inactivating viruses comprises nanofiltration and/or solvent/detergent treatment.
15. The method of claim 1 , wherein the antigen-binding protein has a kinetic binding constant to the human TgFVII or human TgFVIIa epitope of Ka=2.58×10 8 and Kd=9.88×10 −9 .
16. The method of claim 1 , wherein the ligand has an affinity of from 1 to nM for the transgenic human TgFVII or human TgFVIIa.
17. The method of claim 1 , wherein the ligand is obtained from heavy immunoglobulin chains of Camelidae selected from the group consisting of Camelus bactrianus, Camelus dromedarius, Lama pacos, Lama glama and Lama vicugna.