Fused aryl phenazine derivatives (benzo[a]phenazine, pyrido[a]phenazine, benzo[a]phenazine diones, tetrahydropyrido[a]phenazine (dermacozines), etc) are important heterocyclic compounds, which exhibit various pharmacological activities, prominently in cancer cell lines. These compounds significantly intercalate between DNA base pairs and inhibit the activities of topoisomerase I and II enzymes (Topo I and II). XR11576, XR5944, NC-190 and NC-182 belong to phenazine/fused aryl phenazine category and are under clinical studies. Several fused aryl phenazine dione compounds such as pyridazino[4,5-b]phenazine-5,12-diones, 6,11-dihydro-pyrido[2,3-b]phenazine-6,11-diones, 6,11-dihydrobenzo[2,3-b]phenazine-6,11-diones, tetrahydropyrido[a]phenazine, etc possessed anticancer activities on various cancer cell lines. Benzo[a]phenazine diimine and various other fused aryl phenazine compounds form coordination complex with the metal ions (Ru, Rh, Zn and Pt) that intercalate with the DNA and are used for the treatment of cancer. These molecules have influence on MDR cancer cells and serve as anticancer agents in MDR cancer cells. The structure activity relationship of the fused aryl phenazine derivatives revealed that the occurrence of four or more nitrogen atoms in the compounds has better anticancer activity than those molecules with less number of nitrogen atoms. Phenazine antibiotics derived from marine microbes are used for the treatment of microbial and worm diseases. Recent patents on these scaffolds showed that the benzo[a]phenazine derivatives have inhibitory activity on topoisomerase enzymes (Topo I and II) and that act as anticancer agents.

01 Apr 2009·Cancer Chemotherapy and PharmacologyQ4 · MEDICINE

Effect of phenazine compounds XR11576 and XR5944 on DNA topoisomerases

Q4 · MEDICINE

Article

Author: Peter Charlton ; Michael J. Tilby ; Prakash Mistry ; Elaine Willmore ; Caroline A. Austin ; Andrew G. Jobson

PURPOSEPrevious in vitro cleavage data showed that XR11576 and XR5944 stabilised topoisomerase I and topoisomerase II complexes on DNA in a dose-dependent fashion. However, some studies indicated a possible topoisomerase-independent mechanism of action for these drugs.METHODSThree methods, the TARDIS assay, immunoband depletion and the K(+)/SDS assay have been used to assess topoisomerase complex formation induced by XR11576 or XR5944 in human leukaemic K562 cells.RESULTSTARDIS and immunoband depletion assays demonstrated that XR11576 and XR5944 induced complex formation for both topoisomerase I and topoisomerase II (alpha and beta) in a dose- and time-dependent manner, following exposure times of 24 and 48 h at concentrations of 1 or 10 microM. The K(+)/SDS assay showed the formation of protein/DNA complexes after a 1 h exposure to 1 or 10 muM XR11576.CONCLUSIONOur data confirm that XR11576 or XR5944 can form topoisomerase complexes, after long periods of exposure.

01 Feb 2007·Anti-Cancer DrugsQ4 · MEDICINE

Mode of action of the novel phenazine anticancer agents XR11576 and XR5944

Q4 · MEDICINE

Article

Author: Thomas, Hilary ; Lewis, Louisa J. ; Coley, Helen M. ; Mistry, Prakash ; Charlton, Peter A.

The substituted phenazines XR11576 and XR5944 were originally described as dual topoisomerase-I/II poisons. Subsequent reports, however, indicated that the association of their cytotoxicity with cellular topoisomerases was not clear. We set out to study this further using human tumour cell lines, PEO1 ovarian cancer, MDA-MB-231 breast cancer and variants with acquired resistance to VP-16 and XR11576: PEO1VPR, MB-231VPR, MB-231-11576R and camptothecin: PEO1CamR. Cytotoxicity testing [3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide assay], DNA-protein crosslink formation, cell cycle analysis (flow cytometry) for DNA content, apoptosis (flow cytometry) for Annexin V and Western blotting for apoptotic factors. Cytotoxicity testing showed potent cytotoxicity with no cross-resistance to XR11576 or XR5944 in VP-16 or camptothecin-resistant lines. Importantly, we have shown for the first time that the activities of XR5944 and XR11576 are similar as MB-231-11576R cells were resistant to both agents and to a similar extent. XR5944 showed the greatest, albeit slower, interaction with DNA with high levels of DNA-protein crosslinks. Levels of apoptosis in XR5944-treated cells were significantly less than those in VP-16 or XR11576 treatments, suggestive of a more cytostatic rather than cytotoxic mode of action. Interestingly, XR5944 failed to give rise to a G2/M blockade, in contrast to VP-16 or XR11576. XR5944 and XR11576, in line with a dual topoisomerase-I/II-directed mechanism of action, retain potent activity in tumour cells with acquired resistance to VP-16 and camptothecin. Although these agents appear to behave differently from each other according to experimental conditions, this study suggests a substantial overlap in their mechanism(s) of action.

100 Deals associated with MLN-576

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Indication	Highest Phase	Country/Location	Organization	Date
Neoplasms	Phase 1	NL	-	-
Neoplasms	Phase 1	GB	-	-
Neoplasms	Phase 1	-	Millennium Pharmaceuticals, Inc.	-
Neoplasms	Phase 1	-	Celtic Pharma GP Ltd.	-

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