New prodrugs and analogs of the phenazine 5,10-dioxide natural products iodinin and myxin promote selective cytotoxicity towards human acute myeloid leukemia cells

Novel chemotherapeutic strategies for acute myeloid leukemia (AML) treatment are called for. We have recently demonstrated that the phenazine 5,10-dioxide natural products iodinin (3) and myxin (4) exhibit potent and hypoxia-selective cell death on MOLM-13 human AML cells, and that the N-oxide functionalities are pivotal for the cytotoxic activity. Very few structure-activity relationship studies dedicated to phenazine 5,10-dioxides exist on mammalian cell lines and the present work describes our efforts regarding in vitro lead optimizations of the natural compounds iodinin (3) and myxin (4). Prodrug strategies reveal carbamate side chains to be the optimal phenol-attached group. Derivatives with no oxygen-based substituent (-OH or -OCH3) in the 6th position of the phenazine skeleton upheld potency if alkyl or carbamate side chains were attached to the phenol in position 1. 7,8-Dihalogenated- and 7,8-dimethylated analogs of 1-hydroxyphenazine 5,10-dioxide (21) displayed increased cytotoxic potency in MOLM-13 cells compared to all the other compounds studied. On the other hand, dihalogenated compounds displayed high toxicity towards the cardiomyoblast H9c2 cell line, while MOLM-13 selectivity of the 7,8-dimethylated analogs were less affected. Further, a parallel artificial membrane permeability assay (PAMPA) demonstrated the majority of the synthesized compounds to penetrate cell membranes efficiently, which corresponded to their cytotoxic potency. This work enhances the understanding of the structural characteristics essential for the activity of phenazine 5,10-dioxides, rendering them promising chemotherapeutic agents.

Regulation of liver X receptor target genes by 22-functionalized oxysterols. Synthesis, in silico and in vitro evaluations

The endogenous oxysterol 22(R)-hydroxycholesterol (22RHC, 1) is an LXR agonist which upregulates genes of critical involvement in human cholesterol- and lipid metabolism. In contrast, its synthetic epimer 22(S)-hydroxycholesterol (22SHC, 8) has shown specific antagonistic effects in recent studies, avoiding unwanted side effects provided by potent LXR agonists. In terms of LXR modulation, the aim of this study was to compare 22SHC (8), 22RHC (1) and synthesized ligands with keto- and amide functionality in the 22nd position of the cholesterol scaffold. 22SHC (8) and 22RHC (1) performed as expected while 22-ketocholesterol (22KC, 10) revealed an attractive in vitro profile for further investigation in terms of anti-atherosclerotic properties as selective upregulation of the ATP-binding cassette transporter ABCA1 was observed. A new synthesized amide derivate, Fernholtz cyclohexylamide (13) was shown to reduce lipogenesis in a dose-responsive manner and abolish the effect of the potent LXR agonist T0901317 when administered simultaneously.

Synthesis, in vitro and in vivo biological evaluation of new oxysterols as modulators of the liver X receptors

Liver X Receptor (LXR) modulators have shown potential as drugs since they target genes affecting metabolism and fatty acid synthesis. LXR antagonists are of particular interest since they are able to reduce the synthesis of complex fatty acids and glucose uptake. Based on molecular modeling, five new cholesterol mimics were synthesized, where four contained a hydroxyl group in the 22-S-position. The new compounds were screened in vitro against several genes affecting lipid metabolism. The compound that performed best in vitro was a dimethylamide derivative of 22(S)-hydroxycholesterol and it was chosen for in vivo testing. However, the blood plasma analysis from the in vivo tests revealed a concentration lower than needed to give any response, indicating either rapid metabolism or low bioavailability.