The use of generic surrogate peptides for the quantitative analysis of human immunoglobulin G1 in pre-clinical species with high-resolution mass spectrometry.

In the present study, the application of a liquid chromatography high-resolution mass spectrometry (LC-HRMS) analytical assay for the quantitative analysis of a recombinant human immunoglobulin G1 (hIgG1) in rat serum is reported using three generic peptides GPSVFPLAPSSK (GPS), TTPPVLDSDGSFFLYSK (TTP), and VVSVLTVLHQDWLNGK (VVS). Moreover, the deamidation site of a fourth peptide FNWYVDGVEVHNAK (FNW) was identified and further excluded from the assay evaluation due to the inaccuracy of the quantitative results. The rat serum samples were spiked with a fully labeled hIgG1 as internal standard (ISTD). The digestion with trypsin was performed onto the pellet prior to peptide analysis by LC-HRMS using a quadrupole time of flight (QTOF) mass analyzer operating in selected reaction monitoring (SRM) mode with enhanced duty cycles (EDC). The assay linearity for the three investigated peptides was established for a hIgG1 (hIgG1A) from 1.00 to 1000 μg mL(-1) with a mean coefficient of determination (R (2)) higher than 0.9868. The inter-day accuracy and precision obtained in rat serum over 3 days were ≤11.4 and ≤10.5%, respectively. Short-term stability on the auto-sampler at 6 °C for 30 h, at RT for 48 h, and a 100-fold dilution factor were demonstrated. In addition, QC samples prepared in cynomolgus monkey serum and measured with the present method met the acceptance criteria of ±20.0 and ≤20.0% for all three peptides regarding accuracy and precision, respectively. The LC-HRMS method was applied to the analysis of samples from five individual cynomolgus monkeys dosed with a second hIgG1 (hIgG1B) and consistent data were obtained compared to the LC-MS/MS method (conventional triple quadrupole (QqQ) mass analyzer operating in SRM). The present data demonstrate that LC-HRMS can be used for the quantitative analysis of hIgG1 in both species and that quantification is not only limited to classical QqQ instruments.