Materials and methods for removing endotoxins from protein preparations

1. A method comprising: (i) adding allantoin in a supersaturating amount to a protein preparation comprising a desired protein and an amount of at least one endotoxin as a contaminant; (ii) removing solids from the protein preparation to provide a sample for further purification by void exclusion chromatography using a packed particle bed of electropositive particles in a column, the packed particle bed having an interparticle volume; (iii) applying a sample volume of the sample to the packed particle bed, wherein the electropositive particles support void exclusion chromatography, and wherein the sample volume is not greater than the interparticle volume, and (iv) eluting a purified sample comprising the desired protein and a reduced amount of the at least one endotoxin, wherein the eluted desired protein resides in a buffer to which the column was equilibrated, independently from a buffer content of the sample applied to the column.

2. The method of claim 1 , wherein the supersaturating amount of allantoin comprises an amount selected from the group consisting of: (i) about 10%, (ii) about 5%, (ii) from about 0.6 to about 6%, (iii) from about 6% to about 10%, (iv) from about 10% to about 15%, (v) from about 15 to about 20%, (vi) from about 20 to about 50%, and (vii) greater than 50%, wherein the amount is provided as weight/volume.

3. The method of claim 1 , wherein removing the solids comprises one selected from the group consisting of sedimentation, centrifugation, filtration, and combinations thereof.

4. The method of claim 1 , wherein a pH or salt concentration of the protein preparation is adjusted before, during, or after the adding step.

5. The method of claim 1 , wherein a pH or salt concentration of the protein preparation is adjusted before the applying step.

6. The method of claim 1 , wherein the sample volume is less than the interparticle volume of the packed particle bed such that the sample volume relative to the packed bed is one selected from the group consisting of:

(i) less than about 40%, (ii) less than about 35%, (iii) less than about 30%, (iv) less than about 20%, (v) less than about 10%, (vi) less than about 5%, (vii) less than about 2%, and (viii) less than about 1%.

7. The method of claim 1 , wherein the sample volume applied to the bed is less than the interparticle volume by an increment consisting of one selected from the group of 99% of the interparticle volume, 95% of the interparticle volume, 90% of the interparticle volume, 80% of the interparticle volume, 70% of the interparticle volume, 60% of the interparticle volume, 50% of the interparticle volume, 25% of the interparticle volume, 10% of the interparticle volume, 5% of the interparticle volume, 2% of the interparticle volume, 1% of the interparticle volume, and intermediate volume percent thereof.

8. The method of claim 1 , wherein the packed particle bed comprises an anion exchange media and before the applying step, the method further comprises equilibrating the packed particle bed of the anion exchange media with the buffer, wherein the buffer is selected to prevent the desired protein from substantially binding to the anion exchange media.

9. The method of claim 8 , wherein preventing the desired protein from substantially binding to the anion exchange media comprises providing the buffer having a sufficiently low pH.

10. The method of claim 8 , wherein preventing the desired protein from substantially binding to the anion exchange media comprises providing the buffer having a sufficiently high salt concentration.

11. The method of claim 9 , wherein the buffer has a pH comprising one selected from the group consisting of (i) about 7, (ii) about 8, (iii) about 6, and (iv) a range from about 6 to about 8.

12. The method of claim 9 , wherein the buffer comprises a sodium chloride concentration comprising one selected from the group consisting of (i) about 0 mM, (ii) about 50 mM, (iii) about 150 mM, and (iv) a range from about 0 mM to about 150 mM.

13. The method of claim 1 , wherein the electropositive particles comprise an anion exchange chromatography media comprising a positively charged quaternary amine.

14. The method of claim 1 , wherein the applying of (iii) and/or the eluting of (iv) is performed at a linear flow rate comprising a non-zero linear flow rate selected from the group consisting of (i) about 300 cm/hr or less, (ii) about 200 cm/hr or less, (iii) about 100 cm/hr or less, and (iv) about 50 cm/hr or less.

15. The method of claim 1 , wherein the reduced amount of the at least one endotoxin in the purified sample is an amount reduced by 99% or more compared to the amount of the at least one endotoxin in (i), or is an amount less than 1 EU/ml.

16. A method comprising: (i) providing a sample comprising a protein preparation comprising a desired protein and an amount of endotoxin, the sample having a sample volume and being suitable for void exclusion chromatography on a packed particle bed of electropositive particles in a column, wherein the electropositive particles support void exclusion chromatography, the packed particle bed having an interparticle volume, and wherein the sample volume is not greater than the interparticle volume; (ii) applying the sample to the packed particle bed, and (iii) eluting a purified sample comprising the desired protein and a reduced amount of the endotoxin.

17. The method of claim 16 , wherein the reduced amount of endotoxin is an amount reduced by 99% or more compared to the amount of endotoxin in (i), or is an amount less than 1 EU/ml.

18. The method of claim 1 or 16 , wherein the desired protein comprises an antibody or an antibody fragment.