Phenazine 5,10-dioxide analogues as drugs against acute myeloid leukaemia. -Preclinical documentation for lead selection
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Background: Acute Myeloid Leukaemia (AML) is a form of cancer that is associated with low survival rates, and where the current treatment is impaired by low tolerance and severe side-effects. Thus, novel treatments are needed to increase the life-expectancy of AMLpatients. The phenazine 5,10-dioxide compound, iodinin, has shown promising cytotoxic effects against AML cell lines in previous research. Iodinin itself has low solubility in aqueous media, and it was necessary to develop analogues with improved drug properties, which can be tested in animal models for toxicity and efficacy. Methods: The cytotoxicity of the analogues IM 5, IM 20, IM 56 and IM 69 was investigated by performing viability assays on OCI-AML-3 and MOLM-13 AML cell lines and comparing the results to previously obtained results for the normal cell lines rat kidney epithelial (NRK) and cardiac myeloblast (H9c2). The generation of reactive oxygen species (ROS), by a fluorescent reporter (DCF), was also investigated for MOLM-13 and H9c2 cells. Furthermore, key factors in ROS signalling were investigated by western blot. The physiochemical properties were studied by a screening assay for membrane permeability and in silicoprediction of properties important for permeability and biodistribution and linked to the biological activity of the analogues. Results: The analogue IM 56 showed increased cytotoxicity towards AML cell lines compared to the parent compound IM 5. It was also less toxic towards normal cell lines compared to the most frequently used AML drug, the anthracycline Daunorubicin. The difference in biological activities of the analogues is supported by their difference in membrane permeability. The analogues increase the generation of ROS in MOLM-13 cells. Except for the analogue IM 20, no such increase could be detected in H9c2 cells. Conclusion: The analogue IM 56 was chosen for further drug development, due to its enhanced effect against AML cell lines relative to normal cell lines. It increases cell death in MOLM-13 cells, most likely due to generation of ROS. IM 56 is thus a promising candidate for in vivo pre-clinical studies.