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A new and more efficient synthesis of combretastatin A-3 (2a) was completed (8.4% overall yield) starting from methyl gallate and isovanillin with aldehyde 5 and phosphonium salt 8 as key intermediates. Conversion of combretastatin A-3 (2a) to a series of diphosphate prodrugs (10a-l) was readily achieved. Both the diphosphate sodium (10a) and potassium salts (10c) displayed aqueous solubility in excess of 220 mg/ml at room temperature and good cancer cell line inhibitory activity.
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Drug treatment for cancer is now widely utilized and in selected neoplasms offers the opportunity for prolonged remission or even cure. Knowledge of the clinical pharmacology of these agents is critically important to successful therapy. Severe and potentially fatal toxicity may occur unless these agents are administered with meticulous attention to details by physicians experienced in their use. Knowledge of functional impairment of organs responsible for the metabolic breakdown or excretion of these agents and awareness of drug-drug interactions are essential in guiding selection and dosage. The late complications that may result are particularly relevant in patients who achieve prolonged remission or cure and in those for whom these agents are used for benign disorders.
The thesis is composed of two parts, the first part is concerned with experiments in rats, the second part confirms the findings in human beings. After administration of oxytetracycline, chloramphenicol and cyclophosphamide, respectively, to rats an approximately dose-dependent decrease in the pancreatic secretion of proteins and enzyme activities was demonstrable in vivo under exogenous stimulation. The exocrine pancreatic function was studied in humans by performing a secretin-pancreocymin test before and after treatment with oxytetracycline or chloramphenicol and before and after massive-dose therapy with cyclophosphamide or combined cytotoxic treatment (as outlined by De Vita). The investigations further included an examination of the exocrine pancreatic function in subjects on maintenance therapy with cyclophosphamide or busulfan and a comparison with the exocrine pancreatic function in a group of controls. In the oxytetracycline-treated humans there was a depression of the amylase and lipase activities in the duodenal secretion. Administration of chloramphenicol produced a decrease in the amylase output only. In the patients on massive-dose or continued therapy with cyclophosphamide the pancreatic function remained essentially unchanged. In contrast, cytotoxic combination treatment resulted in decreased activities of amylase and lipase. After maintenance treatment with busulfan a reduction of the trypsin and amylase activities was detectable. The volume and electrolyte outputs were found to remain essentially unchanged in all investigations. An impairment in enzyme synthesis is suggested as the major cause of the observed changes of pancreatic secretion after antibiotic and cytotoxic treatment.
Therapeutic drug monitoring of antineoplastic agents must be considered in terms of cytotoxicity to stem cells and toxicity of normal tissues. The dose-limiting toxicity which is myelosuppression is believed to be a necessary effect for maximal antitumour effect. The areas in which therapeutic drug monitoring can play a role include: predicting patients at risk of toxicity, e.g. high dose methotrexate therapy; low bioavailability, e.g. oral 6-mercaptopurine; identifying patients at risk of treatment failure, e.g. methotrexate clearance in acute lymphoblastic leukemia. Although therapeutic drug monitoring is not clinically useful at present, the potential role it can play is illustrated for cytosine arabinoside, adriamycin and cyclophosphamide. Two problems encountered with drug monitoring of antineoplastic disease are tumour heterogeneity manifested by clonal, nutritional and physical characteristics and the common practice of combination chemotherapy. These problems must be addressed in order to make therapeutic drug monitoring a practical tool in cancer chemotherapy. Future applications of therapeutic drug monitoring will require more studies to define therapeutic ranges for single agents, patient-to-patient variation, course-to-course variation and the effects of drug combinations on pharmacokinetic profiles of the drugs used.
Simultaneous analysis of common antineoplastic agents potentially hazardous to healthcare workers is of much interest for the evaluation of the overall health risk to these workers. Such analysis could be applied to both air and surface monitoring samples to provide a broader indication of risk to combinations of these agents. It was determined that the ability to simultaneously evaluate five frequently used, potentially hazardous agents was sufficient for general evaluation of exposures to healthcare workers. The approach used to select the five agents was to obtain a list of the agents used most frequently in both a cancer hospital and an outpatient cancer treatment center, then review the list to determine which agents were potentially more hazardous to human health. From these reviews, it was decided to attempt to develop an analytical method able to detect and quantify the presence of 5-fluorouracil, ifosfamide, cyclophosphamide, doxorubicin HCl, and paclitaxel. A reverse-phase high performance liquid chromatograph (HPLC) with a Waters Symmetry C8 column and a UV wavelength of 195 nm was selected for method development. The mobile phase was 22.75 percent acetonitrile in water buffered to a pH of 6.0. The HPLC analytical method developed is able to detect all five agents of interest, and at minimum detectable concentrations of 0.5-microgram/mL for each of the five agents.
Six alkylating antineoplastic drugs (Cyclophosphamide, Chlorambacil, Busulfan, Melphalan. Streptozotocin and Lomustine) and two reference compounds (methyl methanesulphonate and N-methyl-N'-nitro-N-nitrosoguanidine) were investigated in the SOS Chromotest using the Escherichia coli strain PQ37 (wilde-type) and derived strain (PQ243), which carries the same markers as PQ37 and additionally tagA alkA. As a measure of the SOS induced activity induction factors of sflA::lacZ expression were determined. The strain PQ243 was more sensitive towards all compounds inducing SOS DNA repair then the strain PQ37 Cyclophosphamide was detected as negative in the strain PQ243 in the presence of an exogenous metabolic activation system. Lomustine was inactive both in the mutant strain and in the wild-type strain in the presence of S9 mix fraction as well as in the absence of it. Melphalan and Busulfan (without or with S9 mix) were shown to be positive exclusively in the strain PQ243. Based on these results, we discuss the usefulness of the strain PQ243 in the monitoring of the genotoxicity of drugs and in the genetic analysis of their mode of action.
The antineoplastic agent fotemustine is shown to be a base-pair mutagen to Salmonella. Activity is more marked in the uvrB-proficient strain G46 than in the repair-deficient strain TA1535. This is consistent with its ability to cross-link DNA. Potent activity as a somatic and germ-cell mutagen to Drosophila was also observed. A potent clastogenic response was given by fotemustine in the mouse bone marrow following either oral gavage or intraperitoneal injection of a single dose of 5 mg/kg. In each of these respects it is shown to be indistinguishable from the structurally related antineoplastic agent and human carcinogen MeCCNU. It is concluded that fotemustine should be regarded as having clear potential to induce cancer in humans. Based on these data, including the preponderance of chromosome breakages over recessive lethal mutations in Drosophila, an estimated rodent carcinogenic potency (TD50) of between 15-150 mg/kg is suggested for fotemustine.
The design of many antineoplastic agents has been based on atom or group replacement in normal metabolites. New dimensions are being added to this approach by the synthesis of transition state, bisubstrate and "suicide" inhibitors. These provide greater potency and in some cases selectivity. Leads for differential sensitivity of viral infected cells are appearing (5'-amino-5-iodo-3',5'-dideoxy-uridine, AIU). Equally important has been the development of repository and precursor forms of active drugs along with structures having altered physical and metabolic properties. In the future combination therapy may include drugs whose intrinsic antitumor activity is relatively low but which in combination provide the means of potentiating the antitumor activity of other agents (THU, deoxycoformycin, pyrazofurin). Finally, the potential for developing macromolecular "drugs" such as therapeutic enzymes and peptide hormone analogs must be viewed as a whole new area for drug design.
Neutrophil depletion has a beneficial effect on ischemic myocardium and skeletal muscle upon reperfusion. Antineoplastic agents reduce blood neutrophils effectively, and lead to neutrophil depletion. The purpose of this study was to investigate the effects of four antineoplastic agents in low doses (cyclophosphamide, cisplatinum, mitomycin-C, and 5-fluorouracil) on ischemia-reperfusion injury, using an epigastric island skin-flap model in rats. Fifty male Sprague-Dawley rats, weighing 250-300 g, were randomly divided into five groups, each consisting of 10 rats: control, cyclophosphamide, cisplatinum, mitomycin-C, and 5-fluorouracil groups. Epigastric island skin flaps (measuring 3.5 x 4 cm) were raised and subjected to 10 h of in situ ischemia, followed by 7-day reperfusion and evaluation. Treatment with antineoplastic agents (cyclophosphamide, cisplatinum, mitomycin-C, and 5-fluorouracil) was used to introduce neutropenia. Complete blood counts, cutaneous bleeding time, and skin-flap survival were evaluated. Additionally, levels of malonyldialdehyde (MDA), nitric oxide (NO), glutathione (GSH), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) were measured from extracted skin tissue. Numbers of leukocytes and platelets were decreased in all experimental groups. However, neutropenia and thrombocytopenia were not seen. Cutaneous bleeding activity was prolonged in all experimental groups, but not above the normal value. MDA and NO levels were found to be lower in all four antineoplastic agent groups than in the control group, while GSH, GSH-Px, and SOD enzyme activities were significantly higher (P < 0.05). However, MDA and NO levels were significantly decreased in the cyclophosphamide and 5-fluorouracil groups, as compared to the cisplatinum and mitomycin-C groups (P < 0.01). Also, GSH, GSH-Px, and SOD enzyme activities were significantly increased in the cyclophosphamide and 5-fluorouracil groups, compared to the other two antineoplastic agent groups (P < 0.01). We conclude that antineoplastic agents have beneficial effects on ischemia-reperfusion injuries when their doses are carefully adjusted, by decreasing the number of leukocytes and platelets, and altering the activity of free oxygen radicals.
PURPOSE: to review the neurotoxicity associated with antineoplastic agents. METHODS: four hundred articles, abstracts and book chapters were selected for review. One hundred and ninety (articles, book chapters and abstracts) were identified as representative of the important aspects of neurotoxicity to be presented in this review. RESULTS: in general the dose, schedule and route of administration significantly determine the incidence and outcome of antineoplastic agents neurotoxicity. An updated and detailed review of neurotoxicity is provided with special attention to vinca alkaloids, cisplatin and biologic response modifiers. The neurotoxic side effects of some of the new approaches in cancer therapy and some of the investigational agents are discussed. Guidelines for the prevention and management of this toxicity are presented. In addition, suggestions are made in regard to the preclinical and clinical screening of new agents for neurotoxicity. CONCLUSION: quality of life issues have become a focal point in many clinical trials. Neurotoxicity associated with antineoplastic therapy clearly has an impact on the short and long term quality of the life of cancer patients. A better understanding of this toxicity requires developing reliable and predictive models to screen new agents prior to their introduction into clinical trials; a more detailed and uniform grading system; and the prospective evaluation of neurotoxicity in clinical trials of new antineoplastic agents.