Novel Phenazine 5,10-Dioxides Release ^•OH in Simulated Hypoxia and Induce Reduction of Tumour Volume In Vivo

Abstract

Phenazine 5,10-dioxides (PDOs) are a new class of bioreductive cytotoxins, which could act towards tumours containing hypoxic regions. The PDOs selective-hypoxic bioreduction was probed in vitro; however, the mechanism of action has not been completely explained. Besides, PDOs in vivo antitumour activities have not been demonstrated hitherto. We study the mechanism of hypoxic/normoxic cytotoxicity of PDO representative members. Electron spin resonance is used to confirm •OH production, alkaline comet assay to determine genotoxicity, and gel electrophoresis and flow cytometry to analyze DNA fragmentation and cell cycle distribution. Chemically induced rat breast tumours are employed to evaluate in vivo activities. For the most selective cytotoxin, 7(8)-bromo-2-hydroxyphenazine 5,10-dioxide (PDO1), exclusive hypoxic •OH production is evidenced, while for the unselective ones, •OH is produced in both conditions (normoxia and simulated hypoxia). In normoxia (Caco-2 cells), PDO1 induces cell-cycle arrest and DNA fragmentation but does not significantly induce apoptosis neither at IC50 nor IC80. No difference in the comet-assay scores are observed in normoxia and simulated hypoxia being the unselective 2-amino-7(8)-bromophenazine 5,10-dioxide (PDO2) the most genotoxic. The in vivo efficacy with the absence of systemic toxicity of PDO1 and PDO2 is checked out. Results from this study highlight the potential of PDOs as new therapeutics for cancer.

Selective Hypoxia‐Cytotoxin 7‐Fluoro‐2‐Aminophenazine 5,10‐Dioxide: Toward “Candidate‐to‐Drug” Stage in the Drug‐Development Pipeline

“…In reference to the predicted ADMET properties we analyzed human intestinal absorption (HIA), Caco‐2 permeability, ability to be substrate or inhibit P‐glycoprotein, renal organic cation transporter (OCT2) inhibition, ability to be substrate or inhibit CYP450s, human ether‐a‐go‐go‐related gene (hERG) inhibition, in vitro mutagenicity, and in vivo clastogenicity and effects as carcinogen. On the other hand, we predicted the aqueous solubility (LogS) due to the solubility problems observed previously with this kind of compounds (Table ) . Concerning to the absorption and distribution aspects, the predicted parameters, i. e. HIA and Caco‐2 permeability, indicated that 1 could be orally administered (Table ).…”

“…Due to the aqueous solubility limitations observed previously with some phenazine dioxides and the predicted medium LogS for 1 (Table ), we studied the solubilization of 1 using a mixture of sterile physiological saline:polysorbate 80 (Tween TM 80) (4:1, v/v) as an alternative formulation to improve the bioavailability and adequate tumor‐biodistribution. Tween 80 has been widely used in biochemical applications including solubilizing proteins and emulsifying and dispersing substances and drugs in medicinal and food products .…”

“…Reports about the in vivo anti‐tumoral performance of phenazine 5,10‐dioxides have been scarce. We confirmed for C the ability to reduce tumor‐size when it was administered intraperitoneally (ip) . However, the most potent phenazine 1 has not yet been evaluated in vivo .…”

Hypoxia-activated prodrugs and redox-responsive nanocarriers

“…61 However, it does not show any obvious hypoxia-selective effects as the free radicals generated by phenazine 5,10-dioxides could not induce apoptosis in Caco-2 cells. 62 Moreover, several novel derivatives of phenazine 5,10dioxides have been synthesized to investigate the inhibition rate between DNA and topoisomerase II, showing cytotoxicity in V79 cells in both hypoxic and normoxic environments. 63 Some of these derivatives illustrated cytotoxicity but did not exhibit hypoxia specificity.…”

N-andO-Reaction of 2-Amino and 2-Hydroxyphenazine 5,10-Dioxide Via Microwave Irradiation

“…1-4 in Figure 1a). [4][5][6][7][8][9][10][11] Furthermore, recently phenazine dioxides with improve DNA interaction capacity features an increased planar -conjugation or flexible moieties that add to DNAstacking. 12,13 12 used conventional conditions by heating the phenol or amine intermediate in acetonitrile in presence of potassium carbonate as base.…”