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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 -
Annals of Oncology : Official Journal... Nov 1992Rhizoxin is a 16-membered antifungal macrocyclic lactone isolated from the plant pathogenic fungus Rhizopus chinensis. The compound binds to tubulin, preventing...
Rhizoxin is a 16-membered antifungal macrocyclic lactone isolated from the plant pathogenic fungus Rhizopus chinensis. The compound binds to tubulin, preventing microtubule formation, and inhibiting mitosis. It possesses antitumour activity in vivo against various preclinical murine models, both leukaemias and solid tumours model, as well as in vincristine- and doxorubicin-resistant leukaemia lines. In the present study, cytotoxic activity was observed in human tumour cell lines in vitro at very low concentrations (+/- 10(-10) M) particularly against melanoma, colon, renal, non-small cell and small cell lung cancer. In vivo antitumour activity was demonstrated in murine P388 and L1210 murine leukaemias, solid tumour models B16 melanoma and M5076 sarcoma, and in 5 out of 9 human solid tumour xenografts: LOX melanoma, MX-1 breast cancer, non-small cell lung cancer A549, and small cell lung cancers LXFS 605 and LXFS 650. The absence of cross-resistance to vinca alkaloids was confirmed in vivo against the vincristine-resistant P388 leukaemia subline and the vincristine-resistant human small cell lung cancer LXFS 650. In addition, the antitumour activity of rhizoxin was improved by prolonged or repeated drug administration indicating a schedule dependency. In animal toxicology studies, transient changes in erythrocyte and leukocyte numbers, local phlebitis, diarrhea, and spermatogenic arrest were observed. The LD10 value of rhizoxin after a single intravenous injection was 2.8 mg/kg (8.4 mg/m2). One-tenth of the mouse equivalent LD10 (0.84 mg/m2), the starting dose for clinical phase I studies, was considered to be safe in rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Antibiotics, Antineoplastic; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Screening Assays, Antitumor; Humans; Injections, Intraperitoneal; Injections, Intravenous; Lactones; Lethal Dose 50; Macrolides; Male; Mice; Mice, Nude; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Rats, Wistar; Tumor Cells, Cultured
PubMed: 1450065
DOI: 10.1093/oxfordjournals.annonc.a058334 -
British Journal of Cancer Feb 1996To test the anti-tumour activity of rhizoxin in recurrent and/or metastatic squamous cell head and neck cancer, we performed a phase II study. Eligibility required... (Clinical Trial)
Clinical Trial
To test the anti-tumour activity of rhizoxin in recurrent and/or metastatic squamous cell head and neck cancer, we performed a phase II study. Eligibility required histologically proven squamous cell head and neck cancer. Patients could only have received one prior chemotherapy. Patients were entered if WHO PS was < or = 2 and organ functions were normal. Treatment consisted of rhizoxin 1.5-2.0 mg m-2 i.v. bolus injection once every 3 weeks. Thirty-two patients entered the study. All were eligible, 31 were evaluable for toxicity and 25 for response. Toxicity mainly consisted of pain at the tumour site and leucocytopenia. Mild asthenia and stomatitis were also observed. Two objective partial responses, lasting 7.5 and 3.5 months, were seen. Rhizoxin at this dose and schedule has minor activity in recurrent and/or metastatic squamous cell head and neck cancer.
Topics: Adult; Aged; Antibiotics, Antineoplastic; Carcinoma, Squamous Cell; Female; Head and Neck Neoplasms; Humans; Lactones; Macrolides; Male; Middle Aged
PubMed: 8562350
DOI: 10.1038/bjc.1996.69 -
Frontiers in Fungal Biology 2022Mucoralean fungi from the genus are common inhabitants of terrestrial ecosystems, being some pathogens of animals and plants. In this study, we analyzed the symbiotic...
Mucoralean fungi from the genus are common inhabitants of terrestrial ecosystems, being some pathogens of animals and plants. In this study, we analyzed the symbiotic and toxinogenic potential of species derived from agricultural soils dedicated to the production of papaya ( L.) in Mexico. Four representative strains of soil-derived spp. were analyzed employing molecular, microscopic, and metabolic methods. The ITS phylogenies identified the fungi as HP499, HP475 and HP479, and HP487. We discovered that HP499 and HP475 harbor similar endofungal bacterial symbionts that belong to the genus ( sensu lato) and that none of the four fungi were associated with RmNV-20S and RmNV-23S. Intriguingly, the interaction between - showed different phenotypes from known - symbioses. Elimination of bacteria in HP475 did not cause a detrimental effect on fungal growth or asexual reproduction. Moreover, metabolic and molecular analyses confirmed that, unlike symbiotic HP499, HP475 does not produce rhizoxin, one of the best-characterized toxins produced by spp. The rhizoxin () biosynthetic gene cluster seems absent in this symbiotic bacterium. Our study highlights that the symbioses between and are more diverse than anticipated. Our findings contribute to expanding our understanding of the role bacterial symbionts have in the pathogenicity, biology and evolution of Mucorales.
PubMed: 37746220
DOI: 10.3389/ffunb.2022.893700 -
The Journal of Antibiotics Jan 1987The mode of action of rhizoxin (1a), a new antitumor macrolide, was investigated. Rhizoxin inhibited fusion of the male and the female pronuclei in fertilized sea urchin... (Comparative Study)
Comparative Study
The mode of action of rhizoxin (1a), a new antitumor macrolide, was investigated. Rhizoxin inhibited fusion of the male and the female pronuclei in fertilized sea urchin eggs and inhibited cilia formation in the deciliated sea urchin embryos. In vitro, polymerization of tubulin isolated from porcine brains was completely inhibited at a 1 X 10(-5) M concentration of rhizoxin, and tubulin which had been polymerized by incubation at 37 degrees C for 30 minutes was depolymerized by addition of 1 X 10(-5) M of the drug. Activity of rhizoxin against tubulin polymerization was compared with those of other anti-tubulin drugs such as colchicine, vinblastine and ansamitocin P-3. The homologues of rhizoxin, 1b-3b, also inhibited polymerization of the purified microtuble protein at almost the same extent as rhizoxin.
Topics: Animals; Antibiotics, Antineoplastic; Brain; Female; Lactones; Macrolides; Male; Microtubules; Mitosis; Rhizopus; Sea Urchins; Structure-Activity Relationship; Swine; Tubulin; Zygote
PubMed: 3606749
DOI: 10.7164/antibiotics.40.66 -
The Journal of Antibiotics Jan 1991Chemical modification of the side chain in rhizoxin, a potent antimitotic agent, was attempted in order to study structure-activity relationships and also to devise a...
Chemical modification of the side chain in rhizoxin, a potent antimitotic agent, was attempted in order to study structure-activity relationships and also to devise a probe for photoaffinity labeling of tubulin. An OsO4/NaIO4 oxidation gave a nor-rhizoxin 20-al (5) which was converted to 20-ol (6) by a NaBH3CN reduction. Starting from these two compounds as key intermediates, a series of Wittig reaction products 7-2, and of 20-O-acylates 13-21 were prepared and their anti-tubulin activity and cytotoxicity were determined. An aryl azide derivative 23 was synthesized as a photoaffinity analogue.
Topics: Animals; Antibiotics, Antineoplastic; Isomerism; Lactones; Leukemia P388; Macrolides; Molecular Conformation; Structure-Activity Relationship; Tubulin Modulators; Tumor Cells, Cultured
PubMed: 2001986
DOI: 10.7164/antibiotics.44.66 -
Proceedings of the National Academy of... Sep 2014The recent success of antibody-drug conjugates (ADCs) in the treatment of cancer has led to a revived interest in microtubule-destabilizing agents. Here, we determined...
The recent success of antibody-drug conjugates (ADCs) in the treatment of cancer has led to a revived interest in microtubule-destabilizing agents. Here, we determined the high-resolution crystal structure of the complex between tubulin and maytansine, which is part of an ADC that is approved by the US Food and Drug Administration (FDA) for the treatment of advanced breast cancer. We found that the drug binds to a site on β-tubulin that is distinct from the vinca domain and that blocks the formation of longitudinal tubulin interactions in microtubules. We also solved crystal structures of tubulin in complex with both a variant of rhizoxin and the phase 1 drug PM060184. Consistent with biochemical and mutagenesis data, we found that the two compounds bound to the same site as maytansine and that the structures revealed a common pharmacophore for the three ligands. Our results delineate a distinct molecular mechanism of action for the inhibition of microtubule assembly by clinically relevant agents. They further provide a structural basis for the rational design of potent microtubule-destabilizing agents, thus opening opportunities for the development of next-generation ADCs for the treatment of cancer.
Topics: Animals; Antibiotics, Antineoplastic; Antineoplastic Agents, Phytogenic; Binding Sites; Breast Neoplasms; Cattle; Clinical Trials, Phase I as Topic; Crystallography, X-Ray; Female; Humans; Macrolides; Maytansine; Microtubules; Polyketides; Pyrones; Tubulin; Tubulin Modulators
PubMed: 25114240
DOI: 10.1073/pnas.1408124111 -
Proceedings of the National Academy of... Sep 2014
Topics: Animals; Antibiotics, Antineoplastic; Antineoplastic Agents, Phytogenic; Female; Humans; Macrolides; Maytansine; Microtubules; Polyketides; Pyrones; Tubulin; Tubulin Modulators
PubMed: 25187564
DOI: 10.1073/pnas.1414572111 -
ELife Sep 2014The rice seedling blight fungus Rhizopus microsporus and its endosymbiont Burkholderia rhizoxinica form an unusual, highly specific alliance to produce the highly potent...
The rice seedling blight fungus Rhizopus microsporus and its endosymbiont Burkholderia rhizoxinica form an unusual, highly specific alliance to produce the highly potent antimitotic phytotoxin rhizoxin. Yet, it has remained a riddle how bacteria invade the fungal cells. Genome mining for potential symbiosis factors and functional analyses revealed that a type 2 secretion system (T2SS) of the bacterial endosymbiont is required for the formation of the endosymbiosis. Comparative proteome analyses show that the T2SS releases chitinolytic enzymes (chitinase, chitosanase) and chitin-binding proteins. The genes responsible for chitinolytic proteins and T2SS components are highly expressed during infection. Through targeted gene knock-outs, sporulation assays and microscopic investigations we found that chitinase is essential for bacteria to enter hyphae. Unprecedented snapshots of the traceless bacterial intrusion were obtained using cryo-electron microscopy. Beyond unveiling the pivotal role of chitinolytic enzymes in the active invasion of a fungus by bacteria, these findings grant unprecedented insight into the fungal cell wall penetration and symbiosis formation.
Topics: Burkholderia; Chitinases; Cryoelectron Microscopy; Electrophoresis, Gel, Two-Dimensional; Host-Pathogen Interactions; Hyphae; Macrolides; Microscopy, Confocal; Microscopy, Electron, Scanning; Mutation; Oryza; Plant Diseases; Proteome; Proteomics; Rhizopus; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Symbiosis
PubMed: 25182414
DOI: 10.7554/eLife.03007 -
Molecular Plant-microbe Interactions :... Mar 2015Two strains of Pseudomonas sp., Os17 and St29, were newly isolated from the rhizosphere of rice and potato, respectively, by screening for 2,4-diacetylphloroglucinol...
Two strains of Pseudomonas sp., Os17 and St29, were newly isolated from the rhizosphere of rice and potato, respectively, by screening for 2,4-diacetylphloroglucinol producers. These strains were found to be the same species and were the closest to but different from Pseudomonas protegens among the sequenced pseudomonads, based on 16S ribosomal RNA gene and whole-genome analyses. Strain Os17 was as effective a biocontrol agent as reported for P. protegens Cab57, whereas strain St29 was less effective. The whole-genome sequences of these strains were obtained: the genomes are organized into a single circular chromosome with 6,885,464 bp, 63.5% G+C content, and 6,195 coding sequences for strain Os17; and with 6,833,117 bp, 63.3% G+C content, and 6,217 coding sequences for strain St29. Comparative genome analysis of these strains revealed that the complete rhizoxin analog biosynthesis gene cluster (approximately 79 kb) found in the Os17 genome was absent from the St29 genome. In an rzxB mutant, which lacks the polyketide synthase essential for the production of rhizoxin analogs, the growth inhibition activity against fungal and oomycete pathogens and the plant protection efficacy were attenuated compared with those of wild-type Os17. These findings suggest that rhizoxin analogs are important biocontrol factors of this strain.
Topics: Anti-Bacterial Agents; Antibiosis; Bacillus; Bacterial Proteins; Base Sequence; Biological Control Agents; Cucumis sativus; Fusarium; Genes, Reporter; Genome, Bacterial; Macrolides; Molecular Sequence Data; Multigene Family; Phloroglucinol; Plant Diseases; Plant Roots; Polyketide Synthases; Pseudomonas; Pythium; Recombinant Fusion Proteins; Rhizosphere; Sequence Analysis, DNA; Species Specificity
PubMed: 25496595
DOI: 10.1094/MPMI-09-14-0294-FI