Methods for purification of arysulfatase A
The present invention provides, among other things, improved methods for purifying arylsulfatase A (ASA) protein produced recombinantly for enzyme replacement therapy. The present invention is, in part, based on the surprising discovery that recombinant ASA protein can be purified from unprocessed biological materials, such as, ASA-containing cell culture medium, using a process involving as few as four chromatography columns and only one step of post-chromatographic ultrafiltration/diafiltration.
1. A method of purifying recombinant arylsulfatase A (ASA) protein suitable for intrathecal administration, the method comprising
purifying recombinant arylsulfatase A (ASA) protein from an impure preparation by conducting two or more chromatography steps;
pooling eluate from the final chromatography step;
adjusting the pH of the pooled eluate to between 5.8 to 6.4; and
subjecting the pH-adjusted eluate to a single step of post chromatographic ultrafiltration and/or diafiltration, thereby exchanging the purified recombinant ASA protein directly into a saline-based formulation suitable for intrathecal administration comprising 154 mM NaCl or 0.9% saline without added buffers, and
wherein the method does not comprise more than one ultrafiltration and/or diafiltration step.
2. The method of claim 1 , wherein the pH is adjusted to 6.0.
3. The method of claim 1 , wherein the pH is adjusted using a buffer comprising sodium phosphate, sodium chloride and sodium citrate with pH 7.0.
4. The method of claim 3 , wherein the buffer comprises 0.1-0.5 M sodium phosphate, 0.5-2.5 M sodium chloride and 0.1-0.6 M sodium citrate with pH 7.0.
5. The method of claim 1 , wherein a viral filtration is performed before the step of ultrafiltration and diafiltration.
6. The method of claim 1 , wherein the step of ultrafiltration and/or diafiltration comprises only one diafiltration.
7. The method of claim 1 , wherein the ultrafiltration is tangential flow ultrafiltration.
8. The method of claim 1 , wherein the two or more chromatography steps comprise a cation-exchange chromatography.
9. The method of claim 1 , wherein the ultrafiltration is tangential flow ultrafiltration.
10. The method of claim 1 , wherein ultrafiltration uses a membrane filter comprising a pore size with a molecular weight cutoff of at least 10 kDA.
11. The method of claim 1 , wherein at least 75% of the recombinant ASA is retained in the impure preparation.
12. The method of claim 1 , wherein at least 75% of the recombinant ASA permeates the filter.
13. The method of claim 1 , wherein ultrafiltration comprises a polyethersulfone or cellulose membrane.
14. The method of claim 1 , wherein the recombinant ASA protein has an amino acid sequence at least 70% identical to SEQ ID NO:1.
15. The method of claim 1 , wherein the recombinant ASA protein has an amino acid sequence identical to SEQ ID NO:1.
16. The method of claim 1 , wherein the purified recombinant ASA protein contains less than 100 ng/mg HCP.
17. The method of claim 1 , wherein the purified recombinant ASA protein contains less than 100 pg/mg host cell DNA.
18. The method of claim 9 , wherein the cation-exchange chromatography is the last chromatography step and the eluate from the cation-exchange chromatography is pooled before adjusting the pH.
19. The method of claim 18 , wherein the two or more chromatography steps comprises conducting exchange chromatography, mixed-mode chromatography, and hydrophobic interaction chromatography prior to conducting the cation-exchange chromatography.
20. The method of claim 19 , wherein the anion-exchange chromatography comprises a TMAE resin.
21. The method of claim 19 , wherein the anion-exchange chromatography comprises using a column with a loading capacity greater than 4.5 g/L.
22. The method of claim 21 , wherein the loading capacity of the column is 5-20 g/L.
23. The method of claim 19 , wherein the mixed-mode chromatography is hydroxyapatite (HA) chromatography.
24. The method of claim 19 , wherein the hydrophobic interaction chromatography is phenyl chromatography.
25. The method of claim 1 , wherein the purified recombinant ASA protein is present in the final formulation at a concentration of 15-50 mg/ml.
26. The method of claim 1 , wherein the purified recombinant ASA protein is present in the final formulation at a concentration of 35-45 mg/ml.
27. The method of claim 1 , wherein the two or more chromatography steps comprises conducting anion-exchange chromatography, mixed-mode chromatography, hydrophobic interaction chromatography, and cation-exchange chromatography in succession.
28. The method of claim 1 , wherein the two or more chromatography steps comprises conducting anion-exchange chromatography, mixed-mode chromatography, hydrophobic interaction chromatography, and cation-exchange chromatography in that order.