Validation of a liquid chromatography-high-resolution mass spectrometry method to quantify peptide-related impurities...

With recent advances in quantitative high-resolution mass spectrometry (HRMS), there is growing interest in developing liquid chromatography (LC)-HRMS methods that can simultaneously quantify numerous critical impurities in a peptide or protein drug. This approach is attractive as it could reduce the total number of methods and instruments required during product development and quality control testing, while taking advantage of the technique's high specificity and sensitivity. To investigate the feasibility of this approach for peptide drugs, an LC-HRMS method was validated for the quantification of six peptide-related impurities in teriparatide, the 34-amino acid active ingredient in Forteo. External calibration curves were constructed to correlate the peak area ratio of impurity-to-teriparatide to a known impurity abundance. The method displayed good specificity, sensitivity, linearity, accuracy, repeatability, intermediate precision, and robustness. The lower limits of quantification were 0.02 % or 0.03 % of teriparatide, below the regulatory reporting threshold of 0.10 %. It was found that quantification using three isotopic peaks per peptide did not provide a significant benefit over quantification with one isotopic peak. The method was validated successfully without the impractical inclusion of an isotopically-labeled internal standard for each impurity. Future studies will be conducted to determine the method's longer-term reproducibility.