Antibody–drug conjugates (ADCs) represent a promising class of therapeutics that exploit the high target specificity of antibodies for efficient delivery of cytotoxic or therapeutic agents. While most approved ADCs are used in oncology, their application to other diseases is also feasible. The development of ADCs requires reliable linker chemistry and site-specific antibody modification [1].
We previously established the CCAP method, which uses Fc-affinity peptides for site-specific modification [2,3]; however, residual peptides remained on the antibody, partially impairing Fc functions. To address this limitation, we developed the tCAP method, which enables efficient introduction of an azido group at Lys248 of the Fc region without peptide remnants [4]. The azido-modified antibodies generated by tCAP can be readily conjugated to diverse DBCO-modified payloads via click chemistry, yielding homogeneous ADCs with a defined drug-to-antibody ratio of 2.0.
In this study, we present the preparation and characterization of ADCs produced using the tCAP method, and compare them with other site-specific modification strategies. Furthermore, we demonstrate in vivo tissue distribution of ADCs generated by conjugating payloads to our AccumBody antibodies—engineered for targeted delivery to organs such as the brain, intestine, and muscle—using mouse models. These findings highlight the utility of tCAP as a robust platform for the generation of next-generation ADCs with controlled conjugation and organ-specific delivery potential.
[1] K. Yamada, Y. Ito, ChemBioChem 2019, 20, 2729–2737.
[2] S. Kishimoto, et al., Bioconjug Chem 2019, 30, 698–702.
[3] S. Mori, et al., The Journal of Biochemistry 2021, 169, 35–42.
[4] H. Kawakami, et al., to be submitted.