Fused pyrazine mono-n-oxides as bioreductive drugs. II cytotoxicity in human cells and oncogenicity in a rodent transformation assay (original) (raw)
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The experimental development of bioreductive drugs and their role in cancer therapy
Cancer and Metastasis Reviews, 1993
Bioreductive drugs undergo metabolic reduction to generate cytotoxic metabolites. This process is facilitated by bioreductive enzymes and the lower oxygen conditions present in solid tumours compared to normal tissues. Because of this specificity, bioreductive drugs have enormous potential to contribute to modern cancer therapy. Examples undergoing clinical trials include N-oxides such as tirapazamine, aziridinylnitroimidazoles RSU 1069/RBU 6145 and quinones such as indoloquinone EO9. Other novel structures are also under study. Here we review the experimental development of bioreductive drugs and their role in cancer therapy.
Bioorganic & Medicinal Chemistry, 2006
Hypoxic cells which are common feature of solid tumors are resistant to both anticancer drugs and radiation therapy. Thus, the identification of drugs with the selective toxicity toward hypoxic cells is an important target in anticancer chemotherapy. Tirapazamine has been shown to be an efficient and selective cytotoxin after bioreductive activation in hypoxic cells which is thought to be due to the presence of the 1,4-di-N-oxide. A new series of quinoxaline 1,4-di-N-oxides and fused quinoxaline di-N-oxides were synthesized and evaluated for hypoxic-cytotoxic activity on EAC cell line. Compound 10a was the most potent cytotoxin IC 50 0.9 lg/mL, potency 75 lg/mL, and was approximately 15 times more selective cytotoxin (HCR > 111) than 3-aminoquinoxaline-2-carbonitrile which has been used as a standard (HCR > 7.5). Compounds 4 and 3a,b were more selective than the standard. In addition, antitumor activity against Hepg2 (liver) and U251 (brain) human cell lines was evaluated, compounds 9c and 8a were the most active against Hepg2 with IC 50 values 1.9 and 2.9 lg/mL, respectively, however, all the tested compounds were nontoxic against U251 cell line.
International Journal of Radiation Oncology*Biology*Physics, 1994
Purpose: To study the reduction of RB90740 (I), a fused pyrazine mono-N-oxide that has an oxic:hypoxic cytotoxicity ratioof 10 in a range of murine and human tumor cells in vitro. Methods and Materials: Reduction of 1 has been initiated radiolytically and photochemically in aqueous solution and the products isolated and characterized by high performance liquid chromatography (HPLC). Results: Radiolytic reduction of 1 leads to the formation of the 2-electron reduced product, 2. The stoichiometry of the reduction is pH dependent, increasing from 1 to 2 with increasing pH, but independent of the presence of formate or 2-methyl2-propanol in the reduction mixture. A dimerization product, 3, is also found, which is produced in greater yields at lower pH (< 6). Photochemical reduction of 1 to 2 was also found to be facile. Photolysis of 1 also leads to a deoxyribonucleic acid cleavage reaction. Conclusion: Since 2 is not cytotoxic towards hypoxic cells at concentrations at which 1 is toxic, a probable candidate as the cytotoxic species under hypoxic conditions is the l-electron reduced intermediate species.
Journal of Medicinal Chemistry, 2004
Tirapazamine (TPZ, 1,2,4-benzotriazin-3-amine 1,4-dioxide) is a bioreductive hypoxia-selective cytotoxin, currently in phase II/III clinical trials in combination with radiotherapy and with cisplatin-based chemotherapy. We have prepared a series of 1,2,4-benzotriazine 1,4-dioxide (BTO) analogues of TPZ where a DNA-targeting chromophore is attached at the 3-position via a flexible linker. DNA binding affinity was modified through variation of the chromophore or the pK a of the linker chain. The association constants (K DNA ) for calf thymus DNA ranged from 1 × 10 2 to 5.6 × 10 5 M -1 (ionic strength of 0.01 M). DNA binding affinity was dependent on the presence of a positive charge, either in the linker chain or in the chromophore, and (for a series of 4-acridine carboxamide chromophore analogues) correlated strongly with linker chain pK a . The efficacy of these BTOs in killing aerobic and hypoxic mouse SCCVII tumor cells in vitro was determined by clonogenic survival. Cytotoxicity was measured as the concentration required to reduce plating efficiency to 10% of controls (C 10 ), and the hypoxic cytotoxicity ratio (HCR) for each BTO was calculated as C 10 (aerobic)/C 10 (hypoxic). BTOs bearing a positive charge showed increased hypoxic cytotoxicity (1.5-56-fold) compared to TPZ and mostly modest HCRs (8-51), but some excellent (>167 and 400) values. There was a strong correlation between K DNA and hypoxic cytotoxicity but no correlation between K DNA and HCR. Cytotoxicity in HT-29 human colon carcinoma cells, determined using IC 50 assays, showed similar relationships with a correlation between K DNA and hypoxic cytotoxicity but no correlation between K DNA and HCR. In this cell line, a higher proportion of compounds (7 of 11) had HCRs greater than or equal to that of TPZ. The data confirm that DNA targeting is a useful concept for increasing potency while maintaining hypoxic selectivity and provide a direction for the further development of DNA-targeted analogues of TPZ. Scheme 1 a a Reagents: (a) Et3N, DCM; (b) (CF3CO)2O, DCM; (c) CF3CO3H, DCM; (d) NH4OH, MeOH; (e) acid 22-27, CDI, DMF; then 21, DCM.
Hypoxia-Selective Agents Derived from Quinoxaline 1,4-Di-N-oxides
Journal of Medicinal Chemistry, 1995
Hypoxic cells, which are a common feature of solid tumors, but not normal tissues, are resistant to both anticancer drugs and radiation therapy. Thus the identification of drugs with selective toxicity toward hypoxic cells is a n important objective in anticancer chemotherapy. The benzotriazine di-N-oxide (SR 4233, Tirapazamine) has been shown to be a n efficient and selective cytotoxin for hypoxic cells. Since the bioreductive activation of Tirapazamine is thought to be due to the presence of the l,4-di-N-oxide moiety, a series of 3-aminoquinoxaline-2-carbonitrile 1,Cdi-N-oxides with a range of electron-donating and -withdrawing substituents in the 6and/or 7-positions has been synthesized and evaluated for toxicity to hypoxic cells.
Cancer research, 1981
The cytotoxicities of a number of antineoplastic agents to oxygenated and hypoxic EMT6 mouse mammary tumor cells in culture were examined. Based on the relative sensitivities of cells under aerobic and hypoxic conditions, drugs were placed into three categories. Drugs that were preferentially toxic to cells under oxygenated conditions were classified as type 1 agents; this group includes bleomycin, procarbazine, streptonigrin, actinomycin D, and vincristine. Type 2 agents were those preferentially toxic to cells under hypoxic conditions. These include mitomycin C and Adriamycin. On the basis of other published reports, the glucose analogs, 5-thio-D-glucose and 2-deoxy-D-glucose, and the radiosensitizers, misonidazole and metronidazole, can also be placed in this category. Several antineoplastic agents showed no major preferential toxicity to cells under the conditions of oxygenation or hypoxia used in these experiments and were placed in a third class. This group (type 3) includes 1...
Toxicology in Vitro, 2012
In vitro toxicity screening can reduce the attrition rate of drug candidates in the pharmaceutical industry in the early development process. The focus in this study is to compare the sensitivity for cytotoxicity of a time-resolved fluoro metric oxygen probe with that of a fluoro metric Alamar Blue™ (AB) assay. Both assays measure mitochondrial activity by either oxygen consumption (LUX-A65 N-1 (MitoXpress, Luxcel) probe) or NADH/FADH conversion (AB). Both assays were carried out with increasing concentrations of 109 reference compounds using rat H4IIE and human HepG2 hepatocytes at incubation periods of 24, 48 and 72 h. Prior to this study, the influence on medium with either glucose or galactose was studied to analyze the rate of glycolysis and oxygen consumption, which latter process may be impaired in hepatoma cells. Inhibitors of oxygen consumption in combination with a glucose uptake inhibitor showed the largest consumption rate differences in the presence of 5 mM of glucose. The choice for the 109 reference compounds was based on the so-called Multicentre Evaluation for In vitro Cytotoxicity (MEIC) and on diverse drug categories. For 59 toxic reference compounds, an evaluation for both assays was carried up to 10 À3 M. Toxicity was demonstrated with MitoXpress for 23 (39%) and 36 (61%) compounds in H4IIE and HepG2 cells, respectively, and with AB for 44 (75%) and 40 (68%) compounds. For 50 more pharmaceutical drugs more physiological concentrations were used up to 3.16 Â 10 À5 M, and only 19 (38%) of these compounds appeared to be toxic in both assays. In conclusion, overall 63 (58%) and 60 (55%) compounds showed toxic effects with the MitoXpress and AB assays on rat H4IIE and human HepG2 hepatocytes, respectively. AB assays were more sensitive with respect to H4IIE cells and MitoXpress assays with respect to HepG2 cells. At all tested time intervals, MitoXpress showed its sensitivity, while AB is more sensitive at 48 and 72 h. With AB more toxic compounds were identified, whereas MitoXpress was more sensitive for a few compounds. A species specific difference was clearly found with digoxin, a human specific potassium channel inhibitor. Thus both assays are valuable identifiers of early toxicity with discrimination in time, compounds and species.
Tricyclic [1,2,4]Triazine 1,4-Dioxides As Hypoxia Selective Cytotoxins
Journal of Medicinal Chemistry, 2008
A series of novel tricyclic triazine-di-N-oxides (TTOs) related to tirapazamine have been designed and prepared. A wide range of structural arrangements with cycloalkyl, oxygen-and nitrogencontaining saturated rings fused to the triazine core, coupled with various side chains linked to either hemisphere, resulted in TTO analogues that displayed hypoxia-selective cytotoxicity in vitro. Optimal rates of hypoxic metabolism and tissue diffusion coefficients were achieved with fused cycloalkyl rings in combination with both the 3-aminoalkyl or 3-alkyl substituents linked to weakly basic soluble amines. The selection was further refined using pharmacokinetic/pharmacodynamic model predictions of the in vivo hypoxic potency (AUC req ) and selectivity (HCD) with 12 TTO analogues predicted to be active in vivo, subject to the achievement of adequate plasma pharmacokinetics.
A series of novel tricyclic triazine-di-N-oxides (TTOs) related to tirapazamine have been designed and prepared. A wide range of structural arrangements with cycloalkyl, oxygen-, and nitrogen-containing saturated rings fused to the triazine core, coupled with various side chains linked to either hemisphere, resulted in TTO analogues that displayed hypoxia-selective cytotoxicity in vitro. Optimal rates of hypoxic metabolism and tissue diffusion coefficients were achieved with fused cycloalkyl rings in combination with both the 3-aminoalkyl or 3-alkyl substituents linked to weakly basic soluble amines. The selection was further refined using pharmacokinetic/pharmacodynamic model predictions of the in vivo hypoxic potency (AUC req ) and selectivity (HCD) with 12 TTO analogues predicted to be active in vivo, subject to the achievement of adequate plasma pharmacokinetics. a Abbreviations: TPZ, Tirapazamine; BTO, 1,2,4-benzotriazine 1,4dioxide; HCR, hypoxic cytotoxicity ratio; EVT, extravascular transport; E(1), one-electron reduction potential; PK/PD, pharmacokinetic/pharmacodynamic; D, tissue diffusion coefficient; MCL, multicellular layer; kmet, firstorder rate constant for bioreductive metabolism; SAR, structure-activity relationships; 9-BBN, 9-borabicyclo[3.3.1]nonane; P 7.4, octanol/water coefficient at pH 7.4; CT 10, area under concentration-time curve providing 10% surviving fraction; M 10, amount of BTO metabolized for 10% surviving fraction; X 1/2, calculated penetration half-distance into hypoxic tissue; SF, surviving fraction; LCK, log cell kill; AUC req, area under the plasma concentration-time curve required to give 1 log of cell kill of hypoxic cells in HT29 tumors; HCD, hypoxic cytotoxicity differential.
Molecules, 2019
Despite major advancements in the development of various chemotherapeutic agents, treatment for lung cancer remains costly, ineffective, toxic to normal non-cancerous cells, and still hampered by a high level of remissions. A novel cohort of quinoxaline derivatives designed to possess a wide spectrum of biological activities was synthesized with promising targeted and selective anticancer drug activity. Hence, this study was aimed at determining in vitro anticancer activity effects of a newly synthesized class of 3-(quinoxaline-3-yl) prop-2-ynyl quinoxaline derivatives on A549 lung cancer cells. An assessment of the quinoxaline derivatives ferric reducing power, free radical scavenging activity, cytotoxic activity, and ability to induce reactive oxygen species (ROS) production was performed using the Ferric Reducing Antioxidant Power (FRAP), 2,2-diphenyl-1-picryl-hydrazyl (DPPH), 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and 2',7'-dichlorodihydrofluorescein diacetate (H 2 DCFDA) assays, respectively. The ability of the quinoxaline derivatives to induce apoptosis in A549 cells was assessed using the Acridine Orange/Ethidium Bromide (AO/EB) and Annexin V-FITC/Dead Cell Assay. Of the four quinoxaline derivatives tested, 3-(quinoxaline-3-yl) prop-2-ynyl methanosulphate (LA-39B) and 3-(quinoxaline-3-yl) prop-2-yn-1-ol (LA-55) displayed a dose-dependent reducing power, free-radical scavenging activity, inhibition of cell viability, and stimulation of ROS production which was accompanied by induction of apoptosis in A549 lung cancer cells. None of the quinoxaline derivatives induced cell death or ROS production in non-cancerous Raw 267.4 macrophage cells. Cytotoxicity was observed in A549 lung cancer, HeLa cervical cancer, and MCF-7 breast cancer cells albeit inhibition was more pronounced in A549 cells. The results of the study suggest that 3-(quinoxaline-3-yl) prop-2-ynyl methanosulphate and 3-(quinoxaline-3-yl) prop-2-yn-1-ol induce apoptotic cell death in A549 lung cancer cells.