High-resolution separation of monoclonal antibodies mixtures and their charge variants by an alternative and generic CZE method.

The determination of mAb critical quality attributes (CQA) is crucial for their successful application in health diseases. A generic CZE method was developed for the high-resolution separation of various mAb charge variants, which are often recognized as important CQA. A dynamic coating of the capillary was obtained with polyethylene oxide (PEO), whereas Bis-Tris allowed the analysis of mAbs under native conditions at pH 7.0. The effect of PEO and Bis-Tris concentrations, as well as the nature of the acidic counter ion on the method performance was systematically studied. The %RSD on migration times was below 5% on three different CE instruments using the optimized method. Additional charge variants (in particular acidic variants) were resolved for 10 out of 17 mAbs compared to a reference CZE approach involving the use of ε-amino-caproic acid (EACA), triethylenetetramine (TETA), and hydroxypropylmethyl cellulose (HPMC). The amount of basic and acidic charge variants of 17 Food and Drug Administration (FDA) approved mAbs covering a wide range of physico-chemical properties, e.g., pI between 8.0 and 9.4 and different hydrophobicity, were mainly comprised between 5-15% and 15-30%, respectively. It is noteworthy that applications for the quality control in hospitals as well as for the combination of the immune checkpoint inhibitors nivolumab and ipilimumab were presented.

Development and validation of a functional cell-based neutralizing antibody assay for ipilimumab.

Ipilimumab is the first US FDA-approved immune checkpoint-blocking antibody drug to harness the patient's own immune cells. One of the postmarketing requirements is to develop a cell-based neutralizing antibody assay. Here, we share some of the most challenging aspects encountered during the assay development: new cell line construction; an unexpected inhibition of T-cell activation by low concentrations of ipilimumab; and two issues caused by sample pretreatment with acid dissociation to overcome drug interference: instability of neutralizing antibody positive control at low pH, and incompatibility of commonly used acid dissociation buffers in the cell assay. After troubleshooting and optimization, we successfully validated the assay and used the assay to test clinical samples to date.