A U.S. Patent for “Preparing Antibodies from CHO Cell Cultures for Conjugation” was awarded to Seattle Genetics on October 29th, 2019. The present invention is based in part on the observation that a CHO cell oxidizing enzyme, particularly QSOX1, can survive a seemingly rigorous antibody purification process to reduce subsequent conjugation efficiency of the antibody to a drug. Whether the oxidizing enzyme survives the purification procedure depends on which purification techniques are employed which can vary from one antibody to another. Learn More