Synthesis of Reblastatin, Autolytimycin, and Non-Benzoquinone Analogues: Potent Inhibitors of Heat Shock Protein 90 (original) (raw)
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BioMed Target Journal, 2023
Heat shock protein (HSP90) is a molecular chaperone involved in numerous physiological processes. The primary role of this is to assist in the process of protein folding and to restore misfolded proteins to their correct shape. Chaperones additionally inhibit protein breakdown and aggregation. HSP90 inhibitors possess a notable characteristic of obstructing many cancer-causing pathways by facilitating the breakdown of numerous oncogenic client proteins. Targeting HSP90 therapeutics has been recognized as a viable approach for treating cancer and inflammatory-associated disorders in clinical studies involving different forms of cancer. Inhibition of HSP90 using natural, synthetic, and semisynthetic chemicals has shown encouraging outcomes. HSP90 inhibitors have been extracted from several fungi, bacteria, and plant species. These naturally occurring chemicals play a crucial function in regulating HSP90 activity and can be utilized to develop innovative semi-synthetic or synthetic inhibitors. Over 120 clinical trials have been carried out to evaluate the effectiveness of HSP90 inhibitors as a supplementary therapy for different types of tumor cells. Presently, ongoing research is being carried out to acquire an understanding of innovative and more efficacious methods for treating cancer. Continuing in this research approach, we aim to investigate the discovery, biosynthesis, mechanism of action, and biological features of geldanamycin and its analogs.
Bioorganic & Medicinal Chemistry, 2013
Recent studies have shown that novobiocin (NB), a member of the coumermycin (CA) family of antibiotics with demonstrated DNA gyrase inhibitory activity, inhibits Heat shock protein 90 (HSP90) by binding weakly to a putative ATP-binding site within its C-terminus. To develop more potent HSP90 inhibitors that target this site and to define structure-activity relationships (SARs) for this class of compounds, we have synthesized twenty seven 3-amido-7-noviosylcoumarin analogues starting from NB and CA. These were evaluated for evidence of HSP90 inhibition using several biological assays including inhibition of cell proliferation and cell cycle arrest, induction of the heat shock response, inhibition of luciferase-refolding in vitro, and depletion of the HSP90 client protein c-erbB-2/HER-2/neu (HER2). This SAR study revealed that a substantial increase in biological activity can be achieved by introduction of an indole-2-carboxamide group in place of 4-hydroxy-isopentylbenzamido group at C-3 of NB in addition to removal/derivatization of the 4-hydroxyl group from the coumarin ring. Methylation of the 4-hydroxyl group in the coumarin moiety moderately increased biological activity as shown by compounds 11 and 13. Our most potent new analogue 19 demonstrated biological activities consistent with known HSP90binding agents, but with greater potency than NB.
Engineered Biosynthesis of Geldanamycin Analogs for Hsp90 Inhibition
Chemistry & Biology, 2004
dergo rapid degradation as a consequence of ubiquitination and subsequent catabolism by the proteosome. Zong-Qiang Tian, Greg O. Buchanan, The depletion of mature kinases results in a cytostatic Rika Regentin, Zhihao Hu, C.R. Hutchinson, effect or, in some cases, apoptosis and cell death. and Robert McDaniel* Thus, as a potential new target for cancer therapy, the Kosan Biosciences, Inc. discovery that Hsp90 and one or more of its protein 3832 Bay Center Place kinase cohorts are overproduced in several types of hu-Hayward, California 94545 man cancers has led to further interest in geldanamycin and its analogs [16, 17]. Many geldanamycin analogs have been produced by Summary replacement of the C-17 O-methoxy group with substituted amines [18, 19]. One such drug, 17-allylamino-17-Geldanamycin, a polyketide natural product, is of sigdemethoxygeldanamycin (17-AAG), is currently undernificant interest for development of new anticancer going phase I and II clinical trials [20]. Experience with drugs that target the protein chaperone Hsp90. While the behavior of geldanamycin and 17-AAG in animals the chemically reactive groups of geldanamycin have and humans has pointed to the need for more water been exploited to make a number of synthetic anasoluble and less hepatotoxic forms of this drug [21, 22].
Journal of Medicinal Chemistry, 2007
Heat shock protein 90 (Hsp90) is a molecular chaperone protein implicated in stabilizing the conformation and maintaining the function of many cell-signaling proteins. Many oncogenic proteins are more dependent on Hsp90 in maintaining their conformation, stability, and maturation than their normal counterparts. Furthermore, recent data show that Hsp90 exists in an activated form in malignant cells but in a latent inactive form in normal tissues, suggesting that inhibitors selective for the activated form could provide a high therapeutic index. Hence, Hsp90 is emerging as an exciting new target for the treatment of cancer. We now report on a novel series of 2-amino-6-halopurine Hsp90 inhibitors exemplified by 2-amino-6-chloro-9-(4-iodo-3,5-dimethylpyridin-2-ylmethyl)purine (30). These highly potent inhibitors (IC 50 of 30) 0.009 µM in a HER-2 degradation assay) also display excellent antiproliferative activity against various tumor cell lines (IC 50 of 30) 0.03 µM in MCF7 cells). Moreover, this class of inhibitors shows higher affinity for the activated form of Hsp90 compared to our earlier 8-sulfanylpurine Hsp90 inhibitor series. When administered orally to mice, these compounds exhibited potent tumor growth inhibition (>80%) in an N87 xenograft model, similar to that observed with 17-allylamino-17-desmethoxygeldanamycin (17-AAG), which is a compound currently in phase I/II clinical trials.
Bioorganic & Medicinal Chemistry Letters, 2008
Hsp90 is an attractive chemotherapeutic target because it is essential to maturation of multiple oncogenes. We describe the conformational significance of EH21A1-A4, phenolic derivatives of geldanamycin isolated from Streptomyces sp. Their native free structures are similar to the active form of geldanamycin bound to Hsp90 protein. Their conformational character is a probable reason for their high-affinity binding. Lack of toxic benzoquinone in EH21A1-A4 also adds to their potential as lead compounds for anti-tumor drugs.
Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2009
Rhabdomyosarcoma is a highly metastatic tumor, mostly observed in children and adolescence. When diagnosed at early stages it is mostly curable. However, in advanced or metastatic stages the 5-years survival rate is below 20%. Thus, new treatment strategies for this tumor are needed. In this paper we showed that HSP90 inhibitors, geldanamycin and its analogs, can profoundly affect proliferation of rhabdomyosarcoma cells. We also showed that blocking of HSP90 function induces apoptosis of tumor cells and downregulates expression of anti apoptotic protein AKT. Cells exposed to geldanamycin and its analogs exhibit strong reduction of MET receptor expression and subsequent inhibition of HGF-dependent tumor cells migration and invasion. Interestingly, at concentrations sufficient to block tumor cells growth and motility, the 17AEP-GA, 17AAG and 17DMAP-GA were not toxic or only slightly toxic toward normal hematopoietic, mesenchymal and endothelial cells. This could be due to low HSP90 ex...
Journal of Medicinal Chemistry, 2009
Inhibition of the protein chaperone Hsp90 is a promising new approach to cancer therapy. We describe the preparation of potent non-benzoquinone ansamycins. One of these analogues, generated by feeding 3-amino-5-chlorobenzoic acid to a genetically engineered strain of Streptomyces hygroscopicus, shows high accumulation and long residence time in tumor tissue, is well-tolerated upon intravenous dosing, and is highly efficacious in the COLO205 mouse tumor xenograft model.