Method for the reduction of host cell proteins in affinity chromatography

A method of reducing phospholipase B-like 2 (PLBL2) content in a sample comprising ocrelizumab and the PLBL2, the method comprising:

• a) contacting a protein A chromatography material with the sample;
• b) washing the protein A chromatography material with a high conductivity aqueous solution;
• and
• c) washing the protein A chromatography material, after the contacting step, with a low conductivity aqueous solution,
• wherein step b) occurs before or after step c),
• wherein the low conductivity aqueous solution has a conductivity value of 0.5 mS/cm or less, and
• wherein the high conductivity aqueous solution has a conductivity value of 20 mS/cm or higher.

A method for producing purified ocrelizumab comprising the steps of:

• a) contacting the sample comprising the ocrelizumab recombinantly expressed by a Chinese Hamster Ovary (CHO) cell and PLBL2 with a protein A chromatography material;
• b) washing the protein A chromatography material after the contacting step, with an aqueous solution having a conductivity value of 0.5 mS/cm or less;
• and
• c) recovering the ocrelizumab from the protein A chromatography material, and thereby producing the purified ocrelizumab.

A method of reducing phospholipase B-like 2 (PLBL2) content in a sample including ocrelizumab and PLBL2, the method comprising:

• contacting a protein A chromatography material with the sample;
• and
• washing the protein A chromatography material, after the contacting step, with a low conductivity aqueous solution,
• wherein the low conductivity aqueous solution has a pH from 7 to 9.5,
• wherein the low conductivity aqueous solution has a conductivity value of 0.5 mS/cm or less,
• wherein the low conductivity aqueous solution comprises from 0.5 mM to 6.5 mM Tris, and
• wherein the amount of PLBL2 in the sample after the washing step is reduced to an amount below 0.2 ng per mg of ocrelizumab.