Evaluation of protein impurities in Ademetionine 1,4-Butanedisulfonate

Ademetionine 1,4-Butanedisulfonate (SAMe) is widely used as a prescription drug to treat cholestasis associated with liver disease, and is also used to treat depression, Alzheimer's disease and other diseases. Currently, the main way to produce SAMe is by fermentation of S-adenosylmethionine synthetase（SAMS）. However, during the fermentation process, host cells produce contaminants unrelated to the treatment. Among them, host cell protein (HCP), which is co-purified with the drug, is the main impurity in the production process. HCP-induced antigenic reactions can lead to allergies or other adverse reactions and affect drug quality, efficacy, and safety. Enzyme-linked immunosorbent assay (ELISA) and mass spectrometry (MS) are currently used as the main analytical methods for measuring HCP. The ELISA method may ignore some HCPs with low immunogenicity, while mass spectrometry is primarily employed for the characterization of proteomes. Orthogonal methods can more effectively evaluate impurities in drugs. In this study, ELISA was initially utilized to quantify the content of Saccharomyces cerevisiae host protein in 11 batches of SAMe active pharmaceutical ingredient (API) from two suppliers, then the above APIs were qualitatively analyzed by MS method. Following the identification of surrogate peptide of SAMS, an Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry（UPLC-MS/MS）method was established and validated, the SAMS protein residues in 11 batches of samples were subsequently determined. The results demonstrated that the levels of Saccharomyces cerevisiae host protein and SAMS in the samples were both low, with values below 20 ppm and 1.19 ppm, respectively. The qualitative results also indicate that the types of peptide residues in the samples are more diverse than those of protein residues. Furthermore, residues of proteins and peptides can be detected in all samples, which underscores the importance of evaluating the HCP in API. This study employs a range of complementary detection methods to conduct a comprehensive and sensitive evaluation of total HCP and specific proteins in drugs, thereby guiding more informed assessments of the risks posed by HCP impurities in raw materials during pharmaceutical processes.