The present invention relates to using a versatile synthetic approach to generate a new class of ester, amido, or
carbamate prodrugs of highly potent, but systemically too toxic,
platinum-
acridine anticancer agents. The new hybrids contain a hydroxyl group, which has been masked with a cleavable lipophilic acyl
moiety. Both butanoic (butyric) and bulkier 2-propanepentanoic (valproic) esters were introduced to these compounds. The goal of this design was to improve the
drug-like properties of the
pharmacophore (e. g., log D) without compromising its
DNA-mediated
cell kill potential. Two distinct pathways by which the target compounds undergo effective
ester hydrolysis, the proposed activating step, have been confirmed:
platinum-mediated, self-immolative ester cleavage in a low-
chloride environment (LC-ESMS, NMR
spectroscopy) and enzymatic cleavage by human
carboxylesterase-2 (hCES-2) (LC-ESMS). Several of the new compounds show excellent stability, reduced
systemic toxicity, and favorable activation profiles while maintaining submicromolar
cytotoxicity in various cancers, such as
lung adenocarcinoma cell lines (A549, NCI-H1435). The results suggest that the novel dual-mode
prodrug concept may have the potential to hasten the preclinical development of
platinum-acridines.