Tumor-targeted delivery of 6-Diazo-5-oxo-L-norleucine(DON) using substituted acetylated lysine prodrugs

6-Diazo-5-oxo-L-norleucine (DON) is a glutamine antagonist with robust anticancer efficacy, yet its therapeutic potential was hampered by its biodistribution and toxicity to normal tissues, specifically gastrointestinal tissues which are highly glutamine-dependent. DON acts as an irreversible inhibitor of many glutamine utilizing enzymes critical for the synthesis of nucleic acids/ proteins and the generation of α-ketoglutarate for energy metabolism. The anticancer and autoimmune activities of DON has been shown repeatedly in both preclinical and clinical studies.
Herein we describe the synthesis of a series of tumor-targeted DON prodrugs that were designed to circulate intact and inert in plasma and be cleaved to DON preferentially in tumor cells. Our best prodrug 1 showed stability in plasma, liver and intestinal homogenates, yet was readily cleaved to DON in tumor cells. When directly compared to DON, prodrug 1 exhibited a 27-fold enhanced tumor cell-to-plasma ratio.