Determination of Drug-to-Antibody Ratio of ADCs

The drug-to-antibody ratio (DAR) refers to the number of small toxic molecules per antibody in the antibody-drug conjugates (ADCs). DAR can directly affect safety and efficacy because it determines the amount of "payload" that can be delivered to tumor cells. ADCs vary in DAR due to the heterogeneity of ADCs and their dissociation of small molecules in vivo. It is necessary to determine the DAR of ADCs. This chapter describes some methods for the DAR analysis, including reversed phase high performance liquid chromatography (RP-HPLC), hydrophobic interaction chromatography (HIC) and liquid chromatography-mass spectrometry (LC-MS).