Discovery and Optimization of Novel Hydrogen Peroxide Activated Aromatic Nitrogen Mustard Derivatives as Highly Potent Anticancer Agents

Abstract

We describe several new aromatic nitrogen mustards with various aromatic substituents and boronic esters that can be activated with H2O2 to efficiently cross-link DNA. In vitro studies demonstrated the anticancer potential of these compounds at lower concentrations than those of other clinically used chemotherapeutics, such as melphalan and chlorambucil. In particular, compound 10, bearing an amino acid ester chain, is selectively cytotoxic toward breast cancer and leukemia cells that have inherently high levels of reactive oxygen species. Importantly, 10 was 10–14-fold more efficacious than melphalan and chlorambucil for triple-negative breast-cancer (TNBC) cells. Similarly, 10 is more toxic toward primary chronic-lymphocytic-leukemia cells than either chlorambucil or the lead compound, 9. The introduction of an amino acid side chain improved the solubility and permeability of 10. Furthermore, 10 inhibited the growth of TNBC tumors in xenografted mice without obvious signs of general toxicity, making this compound an ideal drug candidate for clinical development.

Enhanced Tumor Selectivity of 5-Fluorouracil Using a Reactive Oxygen Species-Activated Prodrug Approach

“…The γH2AX formation is a sensitive marker to visualize and quantify DNA double-strand breaks and the consequential cell apoptosis. 38,39 As shown in Figure 5A, upon treatment of compounds 1a,1b, the cells showed dramatical increases in γH2AX formation, which was consistent with the effect of their parent 5FU. In addition, we also evaluated the effects of prodrugs 1a,1b on the PARP1 and caspase 3 cleavage in MCF7 cells using Western blots assays ( Figure 5B).…”

Introduction of the α-ketoamide structure: en route to develop hydrogen peroxide responsive prodrugs

“…The structures of KAM prodrugs are illustrated in Scheme 1. It is speculated that the α-ketoamide moiety in KAM-1–KAM-4 acts as an electron-withdrawing group and shields the activity of nitrogen mustards 18,29–31. Upon the nucleophilic attack by H 2 O 2 anion and the following Baeyer–Villiger rearrangement,27 the promoiety finally hydrolyses into aniline nitrogen mustards with increased nitrogen electron density and restored DNA alkylating activity.…”

Prodrug strategies for targeted therapy triggered by reactive oxygen species

“…36 Following the study of the ROSactivated mechlorethamine prodrugs, the same group developed aromatic nitrogen mustard prodrugs such as 5 and 6 (Table 1). 37,38 The new prodrug strategy consisted of modifying the electronics of the aromatic ring by linking the promoiety to the nitrogen mustard via an electronwithdrawing carboxamide linker (5) or directly linking the effector boronic acid as the electron-withdrawing group (6). Because the electron density of the aromatic ring is decreased, the formation of the cytotoxic aziridinium intermediate is suppressed.…”

“…This prodrug showed impressive tumour growth inhibition in a breast cancer (MDA-MB-468) mouse xenograft model, achieving an in vivo proof-of-concept for the ROS-activated nitrogen mustard prodrug strategy. 38 QMs are well known cross-linking agents that Peng and coworkers exploited their use in the ROS-activated arylboronic acid prodrug strategy. They thoroughly evaluated the influence of the leaving group on the formation of QMs in prodrugs 8-10 (Table 1), 40,41 concluding that the solubility, the leaving group character, and the step-wise formation of the reactive QMs were fundamental for the efficiency of ICLs.…”