Development of ASGR-Mediated Hepatocyte-Targeting Cytotoxic Drug Conjugates with CTSB-Cleavable Linkers Incorporating Succinimide and Succinic Acid Monoamide

The ASGR-mediated endocytosis has been successfully applied
to
the hepatocyte-targeted delivery of therapeutic oligonucleotides via
glycoconjugates. However, few studies have explored the conjugated
small molecules due to the challenge of cleaving suitable linkers
for the release of active small molecules, which is especially different
from GalNAc-ONs cleaved by the deoxyribonuclease II in the lysosome.
In this study, GalNAc-MMAE conjugates linked by CTSB-cleavable linkers
were designed and synthesized. A comprehensive approach revealed that
the conjugates were endocytosed by ASGR and subsequently hydrolyzed
by CTSB, releasing MMAE. The optimized conjugate with a succinic acid
monoamide as the fragment of the linker demonstrated favorable plasma
stability, excellent biodistribution, and significant antitumor activities in vivo with weight gain at the effective dose in an orthotopic
hepatocellular carcinoma mouse model. This research provides a strategy
for developing anti-HCC therapeutic agents using GalNAc drug conjugates
with CTSB-cleavable linkers to release active small molecules.