The 40th Annual Meeting of the Japanese Society for the Study of Xenobiotics

As a key protective mechanism of the central nervous system (CNS), the blood-brain barrier (BBB) effectively prevents the invasion of neurotoxic substances and blood-borne pathogens through selective permeability. However, this physiological characteristic also significantly limits the bioavailability of therapeutic drugs in the CNS when administered systemically, posing a major challenge in treating neurological diseases. Our team established novel dosing strategies via intrathecal (IT) catheterization in a rat model to enhance drug delivery to the CNS while significantly reducing physiological interference.

Understanding and characterizing the major released payload-related species is crucial for supporting lead optimization, bioanalytical method development, and ADME and DDI studies of ADCs.The objective of this study was to establish a quadrupole-orbitrap HRMS-based workflow for rapid screening and characterizing the payload-related species released from ADC after incubating with in vitro plasma, S9 fraction, lysosome, and tumor cells.

In the development of ADC/PDC drugs, linker design and optimization are crucial. The stability of the linker-payload needs to be independently assessed within various in vitro biological incubation systems(e.g., plasma, lysosomes, cathepsin B, β-glucuronidase) without coupling to an antibody or peptide at the early screening stage. Maleimide is widely used as a linker for the conjugation of antibodies or peptides due to its rapid reactivity with thiol groups (-SH) under mild conditions. However, challenges emerge when assessing the stability of linker-payloads containing maleimide groups in in vitro biological matrices.

The present study aims to establish a HepG2 cell model that overexpresses the human PXR gene and CYP3A promoter, facilitating the rapid identification of PXR agonists during the early stages of the preclinical phase.

Antibody-drug conjugates (ADCs) exert cytotoxic effects through binding to cell surface antigens, internalization via endocytosis, and subsequent payload release within endosomal/lysosomal compartments. This study aimed to develop in vitro platforms for evaluating ADC payload release mechanisms, particularly enzyme-mediated linker cleavage.