Exploitation of the size-exclusion effect of reversed-phase high performance liquid chromatography for the direct analysis of diethylene triamine pentaacetic acid in therapeutic monoclonal antibody formulations

Monoclonal antibodies (mAb) are being widely studied for the treatment of cancers and other diseases. The mAb is typically in a solution formulation and administered as an intravenous infusion. Ready-to-use solutions are favored for their clinical convenience but they can potentially suffer from a shorter shelf life due to accelerated rates of some forms of degradation such as oxidation, relative to lyophilized formulations. To improve stability, the chelating agent diethylene triamine pentaacetic acid (DTPA) is often used at very low concentrations in biologics formulations to prevent oxidation induced by metal ions. Because of its low concentration and susceptibility to changes in concentration during stability study or processing, the measurement of DTPA levels during formulation and process development is critical. In response to this need we developed a platform reversed-phase HPLC method that allows for the rapid and direct determination of DPTA concentrations which does not require the prior removal of mAbs in formulation samples. The method exploits the ⿿size exclusion effect⿿ of C18 columns with narrow pore sizes (90⿿120 ÿ) to elute large mAb at the void volume, enabling direct injections of mAb samples for quantitation of DTPA. The method was found to be suitable for the analysis of DTPA in the range of 2⿿20 μg/mL across multiple drug formulations containing different therapeutic mAb and antibody drug conjugates. The method was successfully validated for specificity, precision, accuracy, linearity, and robustness.