Evaluation of Factors Influencing Antibody Reduction for Development of Antibody Drug Conjugates

Reduction/alkylation is one of the leading strategies for the development of antibody drug conjugates (ADCs). Precise control of the reduction process would not only yield a defined number of free thiols per antibody but also result in development of more homogenous conjugates. In the present study, we investigated the effect of various dithiothreitol (DTT) concentrations, temperature conditions, and DTT exposure times on antibody reduction. After antibody reduction, the Ellman's test and SDS-PAGE analysis were used to evaluate free thiols produced and confirm the reduction process, respectively. DTT concentration seems to be a potential factor in the reduction process. Concentrations of 0.1, 1, 5, 10, 20, 50, and 100 mM DTT at 37°C for 30 minutes resulted in approximately 0.4, 1.2, 5.4, 7, 8, 8, and 8 thiols per antibody, respectively. Optimized site-specific conjugation can provide better process control and reproducibility for the development of disulfide-based ADCs.