In vitro/in vivo degradation analysis of trastuzumab by combining specific capture on HER2 mimotope peptide modified material and LC-QTOF-MS

Degradation analysis of therapeutic mAb is of high interest for critical quality attributes assessment and biotransformation studies. However, some obstacles, including low in vivo concentrations of mAb and complex biological matrices containing IgGs, could seriously interfere with mAb bioanalysis. In this study, a bioanalytical platform was developed for studying in vitro/in vivo modifications of trastuzumab, in which specific capture on mimotope peptide modified material was combined with trypsin digestion and LC-QTOF-MS analysis. It is worth noting that this material exhibits high specificity, suitable dynamic binding capacity, very little non-specific protein adsorption, and thus provides good enrichment and quantification performances for trastuzumab from patient serums. In particular, this bioanalytical platform was successfully applied to the dynamic monitoring of modifications of trastuzumab, such as deamidation, isomerization, oxidation and cyclization. Except for the faster deamidation of LC-Asn-30 and HC-Asn-387/392/393 under serum incubation, similar degradation trends for other sites were observed in phosphate buffer and spiked serum. Differences of peptide modification degrees of trastuzumab in patient serums were also observed. The novel platform exhibited superior specificity than Protein A/G/L based analytical methods, lower cost and higher stability than antigen or anti-idiotypic antibody based analytical methods, ensuring the evaluation of modification sites.