Drug-to-Antibody Ratio (DAR) by UV/Vis Spectroscopy

UV/Vis spectroscopy is a simple and convenient method to determine protein concentrations as well as the average number of drugs that are conjugated to the antibody in an antibody–drug conjugate (ADC). Using the measured absorbances of the ADC and the extinction coefficients of the antibody and the drug, the average drug-to-antibody ratio (DAR) can be determined.