AN IMMUNOLIGAND ASSAY FOR QUANTITATION OF PROCESS SPECIFIC ESCHERICHIA-COLI HOST-CELL CONTAMINANT PROTEINS IN A RECOMBINANT BOVINE SOMATOTROPIN

We have developed a Threshold(TM) System immunoligand assay for the qu antitation of residual, process-specific, Escherichia coli host cell c ontaminant proteins (HCP) in somavubove (a normal sequence recombinant bovine somatotropin). The assay has a dynamic range of 2 to 160 ng/mL , with a limit of quantitation of 2 ng/mL. Daily analytical precision (CV) for six replicates of the designated somavubove laboratory standa rd is 3.0%. Cumulative analytical precision for multiple assay runs of this standard (a total of 69 laboratory standard replicates) is 8.4%. A conservative alert limit of 100 ng/mL has been assigned in order to assure analytical precision for each assay sample under conditions of stoichiometric antibody excess. Although the assay was designed for u se as a profile-release specification assay, it has also been used to validate removal of HCP by the proprietary somavubove purification pro cess. This use is consistent with regulatory guidelines related to ''w ell characterized'' recombinant biopharmaceutical proteins.