Aptamer-based sample purification for mass spectrometric quantification of trastuzumab in human serum

In this study, we developed a simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay to quantify trastuzumab in human serum using aptamers for sample purification. Trastuzumab was extracted from serum samples using the capture probe based on its aptamer CH1S-3, followed by reduction, alkylation, trypsin digestion, and quantification using LC-MS/MS. Additionally, a unique peptide, FTISADTSK, was employed as a surrogate peptide and quantified, and *FTISADTSK (13C915N-labeled phenylalanine) was used as an internal standard to minimize variability in detection among the samples. The detection range for this method was 0.5-250 mu g/mL, with a high correlation coefficient (r2 > 0.99). The intra-and inter-day precision (%CV, the coefficient of variation) of the quality control samples was less than 12.7%, and the accuracy (%bias) was below 8.64%. After optimization and verification, this assay was used to determine trastuzumab levels in clinical human serum samples. The results indicated that the trastuzumab concentrations had an approximate 4-fold difference among ten patients (range: 11.80-41.90 mu g/mL). This study provides a novel approach for the ac-curate and quantitative monitoring of the mAb-trastuzumab.

Automated summary

In this study, a simple and accurate LC-MS/MS assay was developed to quantify trastuzumab in human serum using aptamers for sample purification. The method involved extraction of trastuzumab from serum samples, followed by reduction, alkylation, trypsin digestion, and quantification using LC-MS/MS. The assay provided a novel approach for accurate and quantitative monitoring of mAb-trastuzumab.