Self-Immolative Carbamate Linkers for CD19-Budesonide Antibody–Drug Conjugates
Christopher C. Marvin, Adrian D. Hobson, Michael J. McPherson, Theresa A. Dunstan, Thomas R. Vargo, Martin E. Hayes, Margaret M. Fettis, Agnieszka K. Bischoff, Lu Wang, Lu Wang, Axel Hernández, Ying Jia, Jason Z. Oh, Yu Tian
Abstract
Antibody–drug conjugates consist of potent small-molecule payloads linked to a targeting antibody. Payloads must possess a viable functional group by which a linker for conjugation can be attached. Linker-attachment options remain limited for the connection to payloads via hydroxyl groups. A releasing group based on 2-aminopyridine was developed to enable stable attachment of para -aminobenzyl carbamate (PABC) linkers to the C21-hydroxyl group of budesonide, a glucocorticoid receptor agonist. Payload release involves a cascade of two self-immolative events that are initiated by the protease-mediated cleavage of the dipeptide–PABC bond. Budesonide release rates were determined for a series of payload–linker intermediates in buffered solution at pH 7.4 and 5.4, leading to the identification of 2-aminopyridine as the preferred releasing group. Addition of a poly(ethylene glycol) group improved linker hydrophilicity, thereby providing CD19-budesonide ADCs with suitable properties. ADC23 demonstrated targeted delivery of budesonide to CD19-expressing cells and inhibited B-cell activation in mice.