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Journal of Natural Products Apr 2019A Rhizopus sp. culture containing an endosymbiont partner ( Burkholderia sp.) was obtained through a citizen-science-based soil-collection program. An extract prepared...
A Rhizopus sp. culture containing an endosymbiont partner ( Burkholderia sp.) was obtained through a citizen-science-based soil-collection program. An extract prepared from the pair of organisms exhibited strong inhibition of Ewing sarcoma cells and was selected for bioassay-guided fractionation. This led to the purification of rhizoxin (1), a potent antimitotic agent that inhibited microtubule polymerization, along with several new (2-5) and known (6) analogues of 1. The structures of 2-6 were established using a combination of NMR data analysis, while the configurations of the new stereocenters were determined using ROESY spectroscopy and comparison of GIAO-derived and experimental data for NMR chemical shift and J coupling values. Whereas compound 1 showed modest selectivity for Ewing sarcoma cell lines carrying the EWSR1/ FLI1 fusion gene, the other compounds were determined to be inactive. Chemically, compound 2 stands out from other rhizoxin analogues because it is the first member of this class that is reported to contain a one-carbon-smaller 15-membered macrolactone system. Through a combination of experimental and computational tests, we determined that 2 is likely formed via an acid-catalyzed Meinwald rearrangement from 1 because of the mild acidic culture environment created by the Rhizopus sp. isolate and its symbiont.
Topics: Burkholderia; Cell Line, Tumor; Drug Screening Assays, Antitumor; Humans; Macrocyclic Compounds; Macrolides; Molecular Structure; Rhizopus; Sarcoma, Ewing; Stress, Physiological; Structure-Activity Relationship; Symbiosis
PubMed: 30865445
DOI: 10.1021/acs.jnatprod.8b00974 -
Annals of Oncology : Official Journal... Mar 2000Rhizoxin (NSC 332598) is a novel macrolide antitumor antibiotic that inhibits microtubule assembly and also depolymerizes preformed microtubules. In preclinical... (Clinical Trial)
Clinical Trial
BACKGROUND
Rhizoxin (NSC 332598) is a novel macrolide antitumor antibiotic that inhibits microtubule assembly and also depolymerizes preformed microtubules. In preclinical evaluations, rhizoxin demonstrated broad antitumor activity in vitro and in vivo including both vincristine- and vindesine-resistant human lung cancers. Prolonged exposure schedules in xenograft models demonstrated optimal efficacy indicating schedule-dependent antitumor activity. The early phase I and II evaluations a five-minute bolus infusion schedule was studied, however, only modest anti-tumor activity was noted, possibly due to rapid systemic clearance. To overcome these limitations and to exploit the potential for schedule-dependent behavior of rhizoxin, the feasibility of administering rhizoxin as a 72-hour continuous intravenous (i.v.) infusion was evaluated.
PATIENTS AND METHODS
Patients with advanced solid malignancies were entered into this phase I study, in which both the infusion duration and dose of rhizoxin were increased. The starting dose was 0.2 mg/m2 over 12 hours administered every 3 weeks. In each successive dose level, the dose and infusion duration were incrementally increased in a stepwise fashion. Once a 72-hour i.v. infusion duration was reached, rhizoxin dose-escalations alone continued until a maximum tolerated dose (MTD) was determined.
RESULTS
Nineteen patients were entered into the study. Rhizoxin was administered at doses ranging from 0.2 mg/m2 i.v. over 12 hours to 2.4 mg/m2 i.v. over 72 hours every 3 weeks. The principal dose-limiting toxicities (DLT) were severe neutropenia and mucositis, and the incidence of DLT was unacceptably high at rhizoxin doses above 1.2 mg/m2, which was determined to be the MTD and dose recommended for phase II studies. At these dose levels, rhizoxin could not be detected in the plasma by a previously validated and sensitive high-performance liquid chromatography assay with a lower limit of detection of 1 ng/ml. No antitumor responses were observed.
CONCLUSIONS
Rhizoxin can be safely administered using a 72-hour i.v. infusion schedule. The toxicity profile is similar to that observed previously using brief infusion schedules. Using this protracted i.v. infusion schedule the maximum tolerated dose is 1.2 mg/m2/72 hours.
Topics: Adult; Aged; Antibiotics, Antineoplastic; Humans; In Vitro Techniques; Lactones; Macrolides; Middle Aged; Neoplasms; Neutropenia
PubMed: 10811501
DOI: 10.1023/a:1008398725442 -
Angewandte Chemie (International Ed. in... Jan 2019The new approach to the anticancer agent rhizoxin D described herein does not cohere with the conventional logic of metathesis, according to which macrocycles are best...
The new approach to the anticancer agent rhizoxin D described herein does not cohere with the conventional logic of metathesis, according to which macrocycles are best closed at a disubstituted olefinic site; rather, the trisubstituted C11-C12 alkene flanked by an allylic -OH group served as the pivot point for synthesis. This motif was attained in good yield and excellent selectivity by a sequence of alkyne metathesis, trans-hydrostannation and cross coupling. Because the exact same substructure is prominently featured in numerous other natural products, the underpinning strategy, though unusual, might bear more general relevance.
Topics: Biological Products; Lactones; Molecular Structure; Stereoisomerism
PubMed: 30431223
DOI: 10.1002/anie.201812096 -
Cancer Research Jul 1990Rhizoxin is an antitumor drug prepared from the fungus Rhizopus chinensis. It is an inhibitor of microtubule assembly and a potent competitive inhibitor of the binding...
Rhizoxin is an antitumor drug prepared from the fungus Rhizopus chinensis. It is an inhibitor of microtubule assembly and a potent competitive inhibitor of the binding of tubulin of ansamitocin P-3, a maytansine analogue. Rhizoxin also weakly inhibits vinblastine binding to tubulin. We have previously found that maytansine and vinblastine differ strikingly from each other in many ways, including their effects on tubulin sulfhydryl groups and on tubulin decay. Since the structure of rhizoxin is very different from that of vinblastine and only slightly resembles that of maytansine, we decided to compare its interaction with tubulin with those of the other two drugs, using systems which discriminate between the effects of the latter two drugs. We found that rhizoxin acts like maytansine in that it completely prevents formation of an intrachain cross-link in beta-tubulin by N,N'-ethylenebis(iodoacetamide), whereas vinblastine only partially inhibits this. Half-maximal inhibition of formation of this cross-link was observed at 2.5 microM rhizoxin. We found previously that the rate of binding of tubulin to the fluorescent probe bis(8-anilinonaphthalene 1-sulfonate) is a good indicator of tubulin decay and that vinblastine strongly inhibits this, whereas maytansine has no effect. We here report that rhizoxin acts like maytansine in that it has no effect on decay. Thus, despite the fact that its resemblance to maytansine is small, rhizoxin appears to interact with tubulin in very much the same way as does maytansine.
Topics: Animals; Antibiotics, Antineoplastic; Brain; Cattle; Colchicine; Cross-Linking Reagents; Ethylenediamines; Kinetics; Lactones; Macrolides; Maytansine; Molecular Structure; Mycotoxins; Podophyllotoxin; Tubulin; Vinblastine
PubMed: 2364385
DOI: No ID Found -
Pharmaceutical Research Mar 1995RS-1541 is a 13-O-palmitoyl derivative of rhizoxin, an inhibitor of tubulin polymerization. After intravenous administration of RS-1541 to mice bearing M5076 sarcoma,...
RS-1541 is a 13-O-palmitoyl derivative of rhizoxin, an inhibitor of tubulin polymerization. After intravenous administration of RS-1541 to mice bearing M5076 sarcoma, the maximal inhibitory effect of RS-1541 on DNA synthesis in the tumor was observed 24 h after administration, in agreement with the Cmax of rhizoxin produced from RS-1541, but not with the Cmax of RS-1541. The inhibitory effect after RS-1541 was much higher than that after rhizoxin itself. In the spleen, thymus and bone marrow, DNA synthesis was strongly inhibited by rhizoxin but not by RS-1541. After administration of RS-1541, no significant amounts of rhizoxin were detected in the tissues, except for the tumor. In acute toxicity tests, RS-1541 appeared to be less toxic than rhizoxin. These results indicate that RS-1541 possesses a high tumor-selective effect compared with rhizoxin, because of the selective production of rhizoxin in the tumor after administration of RS-1541.
Topics: Animals; Antibiotics, Antineoplastic; DNA, Neoplasm; Dose-Response Relationship, Drug; Female; Injections, Intravenous; Lactones; Macrolides; Male; Mice; Sarcoma, Experimental; Thymidine; Time Factors
PubMed: 7617523
DOI: 10.1023/a:1016248417492 -
European Journal of Pharmacology Jan 2003Our previous study revealed that rhizoxin...
Our previous study revealed that rhizoxin ([1S-[1R*,3R*,5S*,8R*(1R*,2S*,3E,5E,7E),10R*,11S*,13S*,14E,16S*,17S*]]-10-hydroxy-8-[2-methoxy-1,3,7-trimethyl-8-(2-methyl-4-oxazolyl)-3,5,7-octatrienyl]-11,16-dimethyl-4,7,12,18-tetraoxatetracyclo[15.3.1.03,5.011,13]heneicos-14-ene-6,19-dione) has a potent inhibitory effect on in vivo angiogenesis. However, little is known regarding the mechanism by which rhizoxin exhibits antiangiogenic activity. In this study, we examined its effects on the functions of endothelial cells associated with neovascular formation in vivo, using cultured vascular endothelial cells. Rhizoxin concentration-dependently inhibited the proliferation of bovine carotid artery endothelial cells, human umbilical vein endothelial cells and human dermal microvascular endothelial cells, the IC(50) values being 7, 5 and 0.4 nM, respectively. In addition, it reduced the extracellular plasminogen activator level in bovine vascular endothelial cells in the low nM range, and suppressed the migration of human dermal microvascular endothelial cells in the pM range. Furthermore, it blocked the tubular morphogenesis of human umbilical vein endothelial cells and human dermal microvascular endothelial cells on Matrigel in a concentration-dependent manner; the IC(50) values being 40 and 130 pM, respectively. These results suggest that rhizoxin exhibits antiangiogenic activity through the combined inhibition of some functions of endothelial cells responsible for induction of in vivo angiogenesis.
Topics: Angiogenesis Inhibitors; Animals; Antifungal Agents; Cattle; Cell Movement; Endothelium, Vascular; Humans; Lactones; Macrolides; Plasminogen Activators
PubMed: 12524138
DOI: 10.1016/s0014-2999(02)02853-4 -
Medicinal Research Reviews Sep 2015Although fungi produce highly structurally diverse metabolites, many of which have served as excellent sources of pharmaceuticals, no fungi-derived agent has been... (Review)
Review
Although fungi produce highly structurally diverse metabolites, many of which have served as excellent sources of pharmaceuticals, no fungi-derived agent has been approved as a cancer drug so far. This is despite a tremendous amount of research being aimed at the identification of fungal metabolites with promising anticancer activities. This review discusses the results of clinical testing of fungal metabolites and their synthetic derivatives, with the goal to evaluate how far we are from an approved cancer drug of fungal origin. Also, because in vivo studies in animal models are predictive of the efficacy and toxicity of a given compound in a clinical situation, literature describing animal cancer testing of compounds of fungal origin is reviewed as well. Agents showing the potential to advance to clinical trials are also identified. Finally, the technological challenges involved in the exploitation of fungal biodiversity and procurement of sufficient quantities of clinical candidates are discussed, and potential solutions that could be pursued by researchers are highlighted.
Topics: Androstadienes; Animals; Antineoplastic Agents; Aphidicolin; Biological Products; Clinical Trials as Topic; Cyclohexanes; Diketopiperazines; Disease Models, Animal; Drug Design; Drug Resistance, Neoplasm; Fatty Acids, Unsaturated; Female; Fungi; Humans; Macrolides; Male; Mice; Neoplasms; Polycyclic Sesquiterpenes; Sesquiterpenes; Trichothecenes; Wortmannin
PubMed: 25850821
DOI: 10.1002/med.21348 -
Applied and Environmental Microbiology May 2008The products synthesized from a hybrid polyketide synthase/nonribosomal peptide synthetase gene cluster in the genome of Pseudomonas fluorescens Pf-5 were identified...
The products synthesized from a hybrid polyketide synthase/nonribosomal peptide synthetase gene cluster in the genome of Pseudomonas fluorescens Pf-5 were identified using a genomics-guided strategy involving insertional mutagenesis and subsequent metabolite profiling. Five analogs of rhizoxin, a 16-member macrolide with antifungal, phytotoxic, and antitumor activities, were produced by Pf-5, but not by a mutant with an insertion in the gene cluster. The five rhizoxin analogs, one of which had not been described previously, were differentially toxic to two agriculturally important plant pathogens, Botrytis cinerea and Phytophthora ramorum. The rhizoxin analogs also caused swelling of rice roots, a symptom characteristic of rhizoxin itself, but were less toxic to pea and cucumber roots. Of the rhizoxin analogs produced by Pf-5, the predominant compound, WF-1360 F, and the newly described compound 22Z-WF-1360 F were most toxic against the two plant pathogens and three plant species. These rhizoxin analogs were tested against a panel of human cancer lines, and they exhibited potent but nonselective cytotoxicity. This study highlights the value of the genomic sequence of the soil bacterium P. fluorescens Pf-5 in providing leads for the discovery of novel metabolites with significant biological properties.
Topics: Antifungal Agents; Antineoplastic Agents; Botrytis; Cell Line, Tumor; Cucumis; Genomics; Humans; Inhibitory Concentration 50; Macrolides; Magnetic Resonance Spectroscopy; Microbial Sensitivity Tests; Molecular Structure; Multigene Family; Mutagenesis, Insertional; Oryza; Pisum sativum; Peptide Synthases; Phytophthora; Plant Roots; Polyketide Synthases; Pseudomonas fluorescens
PubMed: 18344330
DOI: 10.1128/AEM.02848-07 -
ChemMedChem Nov 2011
Topics: Amides; Antineoplastic Agents; Cell Line, Tumor; Drug Screening Assays, Antitumor; HeLa Cells; Human Umbilical Vein Endothelial Cells; Humans; Macrolides; Structure-Activity Relationship
PubMed: 21990089
DOI: 10.1002/cmdc.201100319 -
Biological & Pharmaceutical Bulletin Feb 1996The effects of i.v. formulations on the pharmacokinetics were examined for two antitumor agents with different lipophilicities: rhizoxin and palmitoyl-rhizoxin...
The effects of i.v. formulations on the pharmacokinetics were examined for two antitumor agents with different lipophilicities: rhizoxin and palmitoyl-rhizoxin (RS-1541). Blood disposition and tissue distributions in rats were evaluated using three formulations: polyethylene glycol 400 (PEG)/dimethylacetamide (DMA) solution, colloidal solution, and lipid emulsions composed of dioctanoyl decanoyl glycerol (ODO) and polyoxyethylene-(60)-hydrogenated castor oil (HCO-60). The effects of emulsion particle size on the pharmacokinetics were also investigated. Rhizoxin rapidly disappeared from the plasma and showed high distribution in the tissues, and in vitro rapidly degraded in the plasma independent of the formulations used. In in vitro plasma, rhizoxin was easily released from the emulsion particles. In contrast to rhizoxin, the pharmacokinetics of RS-1541 with greater lipophilicity changed considerably depending on the formulations. The emulsions showed high and sustained plasma concentrations for RS-1541. RS-1541 was stably incorporated in the emulsion droplets and protected from the degradation when it was applied as an emulsion. Tissue distributions of RS-1541 in rats after an injection as lipid emulsion were strongly affected by the emulsion particle size. Small size emulsions (100-110 nm) showed the highest plasma concentrations of RS-1541, though they were unable to suppress distributions of the drug in peripheral tissues. Emulsions larger than 200 nm (approx.) in size, on the contrary, effectively inhibited the drug from entering the bone marrow, small intestine and other non-reticuloendothelial system (non-RES) organs, where many cytotoxic compounds showed undesired toxicities. These results indicate that the lipid emulsions composed of ODO and HCO-60 could be a promising and effective DDS carrier for RS-1541, which is highly lipophilic and stabilized in the emulsions. This was not the case for rhizoxin, however, which was less lipophilic than palmitoyl analogue RS-1541. The work described herein has demonstrated that by properly selecting the particle size, these lipid emulsions can control the behavior of a drug in the body.
Topics: Animals; Antibiotics, Antineoplastic; Fat Emulsions, Intravenous; Lactones; Male; Particle Size; Rats; Rats, Wistar; Solubility; Tissue Distribution
PubMed: 8850317
DOI: 10.1248/bpb.19.252