Abstract 5741: siteDAR, complete antibody drug conjugate, ADC characterization

Abstract Antibody drug conjugate characterization currently extends to the global determination of the drug -to- antibody ratio (DAR). However, there can be confounding batch variability in pharmacological outcome from ADCs of the same drug, antibody, and DAR. Previously, DAR was obtained by quantifying the extent of modification of the intact antibody or its protein subunits. The coupling chemistry is used to infer which type of amino acids were modified but generally no specific sites of modification are identified and if identification is obtained, it is not quantitative. Borrowing the rigorously reproducible proteolytic digestion methods from multi-atribute mapping (MAM) used in monoclonal antibody manufacture, and compiling a comprehensive quantitative assignment of every abundant peptide in the ADC digest we can both calculate a DAR from the ion volume ratios and a quantitative map of the specific modified sites. This method, termed “siteDAR”, is applied here to both commercial Kadcyla® (ado-trastuzumab emtansine) and in-house preparations of ado-trastuzumab emtansine. We show that preparations of Kadcyla® with the same DAR can have significantly different quantitative maps of modification sites. We use siteDAR analysis in our ADC design cycle to characterize an ADC, and have developed an ADC synthesis method that was quantitatively verified, and had increased biosimilarity with commercially available Kadcyla®. siteDAR for commercial Kadcyla siteDAR for initial in-house Kadcyla Initial biosimilarity Citation Format: Warham L. Martin, Michael Senseney, Bhaskar Kusuma, Julien Dugal-Tessier, Nareshkumar Jain. siteDAR, complete antibody drug conjugate, ADC characterization abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5741.