- Toxoflavins and deazaflavins as the first reported selective small molecule inhibitors of tyrosyl-DNA phosphodiesterase II
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The recently discovered enzyme tyrosyl-DNA phosphodiesterase 2 (TDP2) has been implicated in the topoisomerase-mediated repair of DNA damage. In the clinical setting, it has been hypothesized that TDP2 may mediate drug resistance to topoisomerase II (topo II) inhibition by etoposide. Therefore, selective pharmacological inhibition of TDP2 is proposed as a novel approach to overcome intrinsic or acquired resistance to topo II-targeted drug therapy. Following a high-throughput screening (HTS) campaign, toxoflavins and deazaflavins were identified as the first reported sub-micromolar and selective inhibitors of this enzyme. Toxoflavin derivatives appeared to exhibit a clear structure-activity relationship (SAR) for TDP2 enzymatic inhibition. However, we observed a key redox liability of this series, and this, alongside early in vitro drug metabolism and pharmacokinetics (DMPK) issues, precluded further exploration. The deazaflavins were developed from a singleton HTS hit. This series showed distinct SAR and did not display redox activity; however low cell permeability proved to be a challenge.
- Raoof, Ali,Depledge, Paul,Hamilton, Niall M.,Hamilton, Nicola S.,Hitchin, James R.,Hopkins, Gemma V.,Jordan, Allan M.,Maguire, Laura A.,McGonagle, Alison E.,Mould, Daniel P.,Rushbrooke, Mathew,Small, Helen F.,Smith, Kate M.,Thomson, Graeme J.,Turlais, Fabrice,Waddell, Ian D.,Waszkowycz, Bohdan,Watson, Amanda J.,Ogilvie, Donald J.
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p. 6352 - 6370
(2013/09/23)
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- Investigation of 3-aryl-pyrimido[5,4-e][1,2,4]triazine-5,7-diones as small molecule antagonists of β-catenin/TCF transcription
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Nearly all colorectal cancers (CRCs) and varied subsets of other cancers have somatic mutations leading to β-catenin stabilization and increased β-catenin/TCF transcriptional activity. Inhibition of stabilized β-catenin in CRC cell lines arrests their growth and highlights the potential of this mechanism for novel cancer therapeutics. We have pursued efforts to develop small molecules that inhibit β-catenin/TCF transcriptional activity. We used xanthothricin, a known β-catenin/TCF antagonist of microbial origin, as a lead compound to synthesize related analogues with drug-like features such as low molecular weight and good metabolic stability. We studied a panel of six candidate Wnt/β-catenin/Tcf- regulated genes and found that two of them (Axin2, Lgr5) were reproducibly activated (9-10 fold) in rat intestinal epithelial cells (IEC-6) following β-catenin stabilization by Wnt-3a ligand treatment. Two previously reported β-catenin/TCF antagonists (calphostin C, xanthothricin) and XAV939 (tankyrase antagonist) inhibited Wnt-activated genes in a dose-dependent fashion. We found that four of our compounds also potently inhibited Wnt-mediated activation in the panel of target genes. We investigated the mechanism of action for one of these (8c) and demonstrated these novel small molecules inhibit β-catenin transcriptional activity by degrading β-catenin via a proteasome-dependent, but GSK3β-, APC-, AXIN2- and βTrCP-independent, pathway. The data indicate the compounds act at the level of β-catenin to inhibit Wnt/β-catenin/TCF function and highlight a robust strategy for assessing the activity of β-catenin/TCF antagonists.
- Zeller, J?rg,Turbiak, Anjanette J.,Powelson, Ian A.,Lee, Surin,Sun, Duxin,Showalter, H.D. Hollis,Fearon, Eric R.
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p. 5814 - 5820
(2013/10/22)
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- Microwave-assisted synthesis of 3-aryl-pyrimido[5,4-e][1,2,4]triazine-5, 7(1H,6H)-dione libraries: Derivatives of toxoflavin
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The parallel synthesis of a library of toxoflavin derivatives is described. The microwave-assisted approach involves the de novo generation of the heterocyclic scaffold and allows for facile introduction of a variety of fragments.
- Todorovic, Nick,Giacomelli, Andrew,Hassell, John A.,Frampton, Christopher S.,Capretta, Alfredo
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experimental part
p. 6037 - 6040
(2010/11/21)
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- The facile synthesis of 6-azapurines by transformation of toxoflavins (7-azapteridines)
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This paper describes a reliable and facile synthesis of 6-azapurines (1,5-dimethyl-1H imidazo[4,5-e][1,2,4]triazin-6(5H)-ones) by treatment of toxoflavins (7-azapteridines) with 10% aqueous sodium hydroxide at 5-25 °C along with a benzilic acid type rearr
- Nagamatsu, Tomohisa,Ma, Jun,Yoneda, Fumio
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body text
p. 849 - 854
(2010/10/03)
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