Quality of recombinant/therapeutic proteins produced by engineered cell lines is a concern shared by both manufacturers and regulatory agencies. New assays are needed to facilitate earlier and more rapid analysis of therapeutic protein quality. Cell culture supernatant contains secreted proteins that are indicative of the cellular condition and thus are potential indicators of recombinant protein quality. This study identified changes in secreted host cell proteins (HCP) from cell pools exhibiting varying levels of recombinant antibody expression as determined by quantitative…