Mass spectrometry techniques can be used to evaluate the stability of the linker, analyze free drugs, metabolites, different DAR components, and relative proportions. LC/MS, such as HIC or RP-HPLC coupled with mass spectrometry, has been used for ADC drug structure and composition analysis, to evaluate the stability of ADC linkers, to analyze DAR and coupling sites, and to determine the relative DAR components. Proportion and so on.
One of the challenges of mass spectrometry technology is that all substances have the same ionization efficiency as unconjugated antibodies, regardless of drug loading. Therefore, the premise of applying spectroscopy to the analysis of DAR conjugation is to assume that all materials have the same recovery and ionization. This is not always the case, as the coupling of the drug to the positively charged amine will result in a change in the charge and degree of hydrophobicity.
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