LC-MS Method for the Quantitation of Two Monoclonal Antibodies by Multiple Signature Peptides in Monkey Serum

Abstract

Evaluation of the in-vivo concentration of monoclonal antibody (mAb) mixtures is a challenging task. Here we report the application of an LC-MS bioanalytical method to quantify in monkey serum the Sym004, an equimolar mixture of two monoclonal antibodies, 992 mAb and 1024 mAb. This method has been assessed accordingly to industry standards and it is based on the determination of two specific signature peptides that report the single mAbs concentrations and on another one peptide, common to the two mAbs, that measures the total concentration of the two target proteins. It is shown that the total concentration is in agreement with the sum of the two measured single concentrations in spiked monkey serum samples. The consistency of the results will allow monitoring of the metabolic fate of different parts of the mAbs, at least in the central body compartment. This can then help to rationalize the design of the protein therapeutics modulating their stability accordingly.