ATR-FTIR spectroscopy coupled with multivariate analysis for monitoring degradation and secondary structure transitions in therapeutic peptide formulations.

Therapeutic peptides represent an important class of biomolecules with great clinical and economic significance, however their structural complexity and susceptibility to degradation pose significant analytical challenges. This study aimed to evaluate the applicability of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy in combination with multivariate data analysis as a rapid, non-destructive tool for monitoring structural changes and degradation in formulations containing semaglutide and liraglutide as model compounds. Spectral data allowed the detection of subtle conformational changes, particularly in the amide region I, which is directly related to the secondary structure. The application of principal component analysis (PCA) enabled the identification of clustering patterns and classification of samples under different stress conditions, while the analysis of loading and contribution line plots allowed recognition of the main spectral features contributing most to the variance. Despite the relatively short incubation times and using a dry film approach which may introduce conformational changes, clear changes associated with early and advanced phases of degradation were detected. ATR-FTIR results were complemented by liquid chromatography-high-resolution mass spectrometry (LC-HRMS), showing consistency between the spectroscopic, mass spectrometric and chromatographic data. As demonstrated in this proof-of-concept study, this integrated analytical approach indicates potential for application in stability monitoring, formulation studies, process control, and as part of a multi-analytical strategy for product authentication, particularly when structural alterations are expected. The results confirm the applicability of ATR-FTIR spectroscopy combined with multivariate data analysis as a powerful tool for rapid assessment of the behavior of peptide medicines under stress conditions.