151
|
Papadopoulou MV, Bloomer WD, Torti VR, Page JG. Investigational New Drug-Directed, 5-Day Repeat Dose Toxicity Study of 4-[3-(2-Nitro-1-Imidazolyl)-Propylamino]-7-Chloroquinoline Hydrochloride (NLCQ-1, NSC 709257) Administered with or without Taxol® in Sprague-Dawley Rats. Basic Clin Pharmacol Toxicol 2010; 106:497-504. [DOI: 10.1111/j.1742-7843.2009.00530.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
152
|
Gu Y, Atwell GJ, Wilson WR. Metabolism and excretion of the novel bioreductive prodrug PR-104 in mice, rats, dogs, and humans. Drug Metab Dispos 2009; 38:498-508. [PMID: 20019245 DOI: 10.1124/dmd.109.030973] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
PR-104 is the phosphate ester of a 3,5-dinitrobenzamide nitrogen mustard (PR-104A) that is reduced to active hydroxylamine and amine metabolites by reductases in tumors. In this study, we evaluate the excretion of [(3)H]PR-104 in mice and determine its metabolite profile in mice, rats, dogs, and humans after a single intravenous dose. Total radioactivity was rapidly and quantitatively excreted in mice, with cumulative excretion of 46% in urine and 50% in feces. The major urinary metabolites in mice were products from oxidative N-dealkylation and/or glutathione conjugation of the nitrogen mustard moiety, including subsequent mercapturic acid pathway metabolites. A similar metabolite profile was seen in mouse bile, mouse plasma, and rat urine and plasma. Dogs and humans also showed extensive thiol conjugation but little evidence of N-dealkylation. Humans, like rodents, showed appreciable reduced metabolites in plasma, but concentrations of the cytotoxic amine metabolite (PR-104M) were higher in mice than humans. The most conspicuous difference in metabolite profile was the much more extensive O-beta-glucuronidation of PR-104A in dogs and humans than in rodents. The structure of the O-beta-glucuronide (PR-104G) was confirmed by independent synthesis. Its urinary excretion was responsible for 13 +/- 2% of total dose in humans but only 0.8 +/- 0.1% in mice. Based on these metabolite profiles, biotransformation of PR-104 in rodents is markedly different from that in humans, suggesting that rodents may not be appropriate for modeling human biotransformation and toxicology of PR-104.
Collapse
Affiliation(s)
- Yongchuan Gu
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | | | | |
Collapse
|
153
|
Milbank JBJ, Stevenson RJ, Ware DC, Chang JYC, Tercel M, Ahn GO, Wilson WR, Denny WA. Synthesis and evaluation of stable bidentate transition metal complexes of 1-(chloromethyl)-5-hydroxy-3-(5,6,7-trimethoxyindol-2-ylcarbonyl)-2,3-dihydro-1H-pyrrolo[3,2-f]quinoline (seco-6-azaCBI-TMI) as hypoxia selective cytotoxins. J Med Chem 2009; 52:6822-34. [PMID: 19821576 DOI: 10.1021/jm9008746] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of metal complexes were prepared as potential prodrugs of the extremely toxic DNA minor groove alkylator 1-(chloromethyl)-5-hydroxy-3-[(5,6,7-trimethoxyindol-2-yl)carbonyl]-2,3-dihydro-1H-pyrrolo[3,2-f]quinoline (seco-6-azaCBI-TMI) and close analogues. The pyrrolo[3,2-f]quinoline cytotoxins were prepared from 2-methoxy-4-nitroaniline in a nine-step synthesis involving a Skraup construction of a quinoline intermediate, its appropriate functionalization, and a final radical cyclization. The metal complexes were prepared from these and the labile metal complex synthons [Co(cyclen)(OTf)(2)](+), [Cr(acac)(2)(H(2)O)(2)](+), and [Co(2)(Me(2)dtc)(5)](+). The cobalt complexes were considerably more stable than the free effectors and showed significant attenuation of the cytotoxicity of the latter, with IC(50) ratios (complex/effector) of 50- to 150-fold, and substantial hypoxic cell selectivity, with IC(50) ratios (oxic/hypoxic cells) of 20- to 40-fold. The cobalt complexes were also efficiently activated by ionizing radiation, with G values for loss of the compound close to the theoretical value for one-electron reduction of 0.68 micromol/J. This work extends earlier observations that cobalt cyclen complexes are suitable for both the bioreductive and radiolytic release of potent pyrrolo[3,2-f]quinoline effectors.
Collapse
Affiliation(s)
- Jared B J Milbank
- Auckland Cancer Society Research Centre, School of Medical Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | | | | | | | | | | | | | | |
Collapse
|
154
|
Jameson MB, Rischin D, Pegram M, Gutheil J, Patterson AV, Denny WA, Wilson WR. A phase I trial of PR-104, a nitrogen mustard prodrug activated by both hypoxia and aldo-keto reductase 1C3, in patients with solid tumors. Cancer Chemother Pharmacol 2009; 65:791-801. [DOI: 10.1007/s00280-009-1188-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 11/12/2009] [Indexed: 11/28/2022]
|
155
|
Cairns RA, Bennewith KL, Graves EE, Giaccia AJ, Chang DT, Denko NC. Pharmacologically increased tumor hypoxia can be measured by 18F-Fluoroazomycin arabinoside positron emission tomography and enhances tumor response to hypoxic cytotoxin PR-104. Clin Cancer Res 2009; 15:7170-4. [PMID: 19920111 DOI: 10.1158/1078-0432.ccr-09-1676] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
PURPOSE Solid tumors contain microenvironmental regions of hypoxia that present a barrier to traditional radiotherapy and chemotherapy, and this work describes a novel approach to circumvent hypoxia. We propose to overcome hypoxia by augmenting the effectiveness of drugs that are designed to specifically kill hypoxic tumor cells. EXPERIMENTAL DESIGN We have constructed RKO colorectal tumor cells that express a small RNA hairpin that specifically knocks down the hypoxia-inducible factor 1a (HIF1a) transcription factor. We have used these cells in vitro to determine the effect of HIF1 on cellular sensitivity to the hypoxic cytotoxin PR-104, and its role in cellular oxygen consumption in response to the pyruvate dehydrogenase kinase inhibitor dichloroacetate (DCA). We have further used these cells in vivo in xenografted tumors to determine the role of HIF1 in regulating tumor hypoxia in response to DCA using (18)F-fluoroazomycin arabinoside positron emission tomography, and its role in regulating tumor sensitivity to the combination of DCA and PR-104. RESULTS HIF1 does not affect cellular sensitivity to PR-104 in vitro. DCA transiently increases cellular oxygen consumption in vitro and increases the extent of tumor hypoxia in vivo as measured with (18)F-fluoroazomycin arabinoside positron emission tomography. Furthermore, we show that DCA-dependent alterations in hypoxia increase the antitumor activity of the next-generation hypoxic cytotoxin PR-104. CONCLUSIONS DCA interferes with the HIF-dependent "adaptive response," which limits mitochondrial oxygen consumption. This approach transiently increases tumor hypoxia and represents an important method to improve antitumor efficacy of hypoxia-targeted agents, without increasing toxicity to oxygenated normal tissue.
Collapse
Affiliation(s)
- Rob A Cairns
- Campbell Family Institute for Breast Cancer Research, Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario, Canada
| | | | | | | | | | | |
Collapse
|
156
|
Li XF, Sun X, Ma Y, Suehiro M, Zhang M, Russell J, Humm JL, Ling CC, O'Donoghue JA. Detection of hypoxia in microscopic tumors using 131I-labeled iodo-azomycin galactopyranoside (131I-IAZGP) digital autoradiography. Eur J Nucl Med Mol Imaging 2009; 37:339-48. [PMID: 19921184 DOI: 10.1007/s00259-009-1310-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Accepted: 10/21/2009] [Indexed: 12/17/2022]
Abstract
PURPOSE Previous studies have shown that tumors less than 1 mm diameter derived from HT29 colorectal cancer cells are extremely hypoxic when grown intraperitoneally or intradermally in nude mice, whereas those of greater size (approximately 1-4 mm diameter) are not significantly hypoxic. The object of this study was to determine if digital autoradiography using the radiolabeled hypoxia imaging tracer iodo-azomycin galactopyranoside ((131)I-IAZGP) could detect hypoxia in this model. METHODS Microscopic HT29 tumors were grown as disseminated peritoneal disease and intradermally in nude mice. Tumors ranged in size from a few hundred microns to several millimeters in diameter. Animals were intravenously administered (131)I-IAZGP and pimonidazole 2 h before sacrifice. Following sacrifice, the intratumoral distribution of (131)I-IAZGP was assessed by digital autoradiography and compared with immunofluorescence microscopic images of pimonidazole binding and carbonic anhydrase IX (CAIX) expression. RESULTS The distributions of (131)I-IAZGP, pimonidazole, and CAIX expression were similar. Tumors less than 1 mm diameter displayed high (131)I-IAZGP uptake; these tumors also stained strongly for pimonidazole and CAIX. Larger tumors (approximately 1-4 mm diameter) were not significantly hypoxic and had low (131)I-IAZGP accumulation. CONCLUSION (131)I-IAZGP can detect hypoxia in microscopic tumors. Microscopic tumors are useful models for the validation of hypoxia radiotracers, and digital autoradiography is an appropriate technique for studying the distribution of hypoxia radiotracers in microscopic tumors.
Collapse
Affiliation(s)
- Xiao-Feng Li
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
157
|
Lo WY, Balasubramanian A, Helsby NA. Hydrolysis of dinitrobenzamide phosphate prodrugs: the role of alkaline phosphatase. ACTA ACUST UNITED AC 2009; 24:1-16. [PMID: 19353998 DOI: 10.1515/dmdi.2009.24.1.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Phosphate prodrugs which undergo hydrolysis in vivo have been used to improve the solubility and pharmacokinetic properties of a number of drugs. Dinitrobenzamide mustards (DNBM) are examples of such drugs. We investigated the ability of purified alkaline phosphatase isoforms to dephosphorylate three DNBM phosphate prodrugs. In addition, the relative rate of dephosphorylation of these phosphate prodrugs in a number of tissues was determined. These phosphate prodrugs are indeed substrates for alkaline phosphatase, with time dependent formation of the hydrolysis product. Intestinal alkaline phosphatase (IAP) and placental alkaline phosphatase (PLAP) had the highest activity for these substrates and compound P2 was the most rapidly metabolised. Similarly, compound P2 had the shortest half life in mouse serum (t1/2 = 1.15 h) compared with P1 (t1/2 = 13.34 h) and P3 (t1/2 = 4.4 h). However, serum has very low dephosphorylase activity for these substrates compared with intestine and liver homogenates. In addition, there is little or no difference in the relative rate of dephosphorylation of each of the three compounds in mouse tissues in contrast to the pattern observed with purified alkaline phosphatase and mouse serum. Hence additional phosphatase enzymes may be involved in the metabolism of phosphate prodrugs in vivo.
Collapse
Affiliation(s)
- Wing-Yee Lo
- Department of Molecular Medicine and Pathology, University of Auckland, New Zealand
| | | | | |
Collapse
|
158
|
Dachs GU, Hunt MA, Syddall S, Singleton DC, Patterson AV. Bystander or no bystander for gene directed enzyme prodrug therapy. Molecules 2009; 14:4517-45. [PMID: 19924084 PMCID: PMC6255103 DOI: 10.3390/molecules14114517] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2009] [Revised: 11/03/2009] [Accepted: 11/05/2009] [Indexed: 12/12/2022] Open
Abstract
Gene directed enzyme prodrug therapy (GDEPT) of cancer aims to improve the selectivity of chemotherapy by gene transfer, thus enabling target cells to convert nontoxic prodrugs to cytotoxic drugs. A zone of cell kill around gene-modified cells due to transfer of toxic metabolites, known as the bystander effect, leads to tumour regression. Here we discuss the implications of either striving for a strong bystander effect to overcome poor gene transfer, or avoiding the bystander effect to reduce potential systemic effects, with the aid of three successful GDEPT systems. This review concentrates on bystander effects and drug development with regard to these enzyme prodrug combinations, namely herpes simplex virus thymidine kinase (HSV-TK) with ganciclovir (GCV), cytosine deaminase (CD) from bacteria or yeast with 5-fluorocytodine (5-FC), and bacterial nitroreductase (NfsB) with 5-(azaridin-1-yl)-2,4-dinitrobenzamide (CB1954), and their respective derivatives.
Collapse
Affiliation(s)
- Gabi U. Dachs
- Angiogenesis and Cancer Research Group, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mail: (M.A.H.)
| | - Michelle A. Hunt
- Angiogenesis and Cancer Research Group, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mail: (M.A.H.)
| | - Sophie Syddall
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; E-Mails: (S.S.); (D-C.S.); (A-V.P.)
| | - Dean C. Singleton
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; E-Mails: (S.S.); (D-C.S.); (A-V.P.)
| | - Adam V. Patterson
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; E-Mails: (S.S.); (D-C.S.); (A-V.P.)
| |
Collapse
|
159
|
Tercel M, Atwell GJ, Yang S, Stevenson RJ, Botting KJ, Boyd M, Smith E, Anderson RF, Denny WA, Wilson WR, Pruijn FB. Hypoxia-Activated Prodrugs: Substituent Effects on the Properties of Nitro seco-1,2,9,9a-Tetrahydrocyclopropa[c]benz[e]indol-4-one (nitroCBI) Prodrugs of DNA Minor Groove Alkylating Agents. J Med Chem 2009; 52:7258-72. [DOI: 10.1021/jm901202b] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Moana Tercel
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Graham J. Atwell
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Shangjin Yang
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Ralph J. Stevenson
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - K. Jane Botting
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Maruta Boyd
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Eileen Smith
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Robert F. Anderson
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - William A. Denny
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - William R. Wilson
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Frederik B. Pruijn
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| |
Collapse
|
160
|
Prosser GA, Copp JN, Syddall SP, Williams EM, Smaill JB, Wilson WR, Patterson AV, Ackerley DF. Discovery and evaluation of Escherichia coli nitroreductases that activate the anti-cancer prodrug CB1954. Biochem Pharmacol 2009; 79:678-87. [PMID: 19852945 DOI: 10.1016/j.bcp.2009.10.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Revised: 10/07/2009] [Accepted: 10/09/2009] [Indexed: 10/20/2022]
Abstract
Gene-directed enzyme prodrug therapy (GDEPT) aims to achieve highly selective tumor-cell killing through the use of tumor-tropic gene delivery vectors coupled with systemic administration of otherwise inert prodrugs. Nitroaromatic prodrugs such as CB1954 hold promise for GDEPT as they are readily reduced to potent DNA alkylating agents by bacterial nitroreductase enzymes (NTRs). Transfection with the nfsB gene from Escherichia coli can increase the sensitivity of tumor cells to CB1954 by greater than 1000-fold. However, poor catalytic efficiency limits the activation of CB1954 by NfsB at clinically relevant doses. A lack of flexible, high-throughput screening technology has hindered efforts to discover superior NTR candidates. Here we demonstrate how the SOS chromotest and complementary screening technologies can be used to evaluate novel enzymes that activate CB1954 and other bioreductive and/or genotoxic prodrugs. We identify the major E. coli NTR, NfsA, as 10-fold more efficient than NfsB in activating CB1954 as purified protein (k(cat)/K(m)) and when over-expressed in an E. coli nfsA(-)/nfsB(-) gene deleted strain. NfsA also confers sensitivity to CB1954 when expressed in HCT-116 human colon carcinoma cells, with similar efficiency to NfsB. In addition, we identify two novel E. coli NTRs, AzoR and NemA, that have not previously been characterized in the context of nitroaromatic prodrug activation.
Collapse
Affiliation(s)
- G A Prosser
- School of Biological Sciences, Victoria University of Wellington, Kelburn Parade, Wellington, New Zealand
| | | | | | | | | | | | | | | |
Collapse
|
161
|
Wilson WR, Stribbling SM, Pruijn FB, Syddall SP, Patterson AV, Liyanage HS, Smith E, Botting KJ, Tercel M. Nitro-chloromethylbenzindolines: hypoxia-activated prodrugs of potent adenine N3 DNA minor groove alkylators. Mol Cancer Ther 2009; 8:2903-13. [DOI: 10.1158/1535-7163.mct-09-0571] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
162
|
Rapid and sensitive ultra-high-pressure liquid chromatography–tandem mass spectrometry analysis of the novel anticancer agent PR-104 and its major metabolites in human plasma: Application to a pharmacokinetic study. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 877:3181-6. [DOI: 10.1016/j.jchromb.2009.08.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 08/07/2009] [Accepted: 08/09/2009] [Indexed: 11/20/2022]
|
163
|
Abstract
Anticancer prodrugs designed to target specifically tumor cells should increase therapeutic effectiveness and decrease systemic side effects in the treatment of cancer. Over the last 20 years, significant advances have been made in the development of anticancer prodrugs through the incorporation of triggers for reductive activation. Reductively activated prodrugs have been designed to target hypoxic tumor tissues, which are known to overexpress several endogenous reductive enzymes. In addition, exogenous reductive enzymes can be delivered to tumor cells through fusion with tumor-specific antibodies or overexpressed in tumor cells through gene delivery approaches. Many anticancer prodrugs have been designed to use both the endogenous and exogenous reductive enzymes for target-specific activation and these prodrugs often contain functional groups such as quinones, nitroaromatics, N-oxides, and metal complexes. Although no new agents have been approved for clinical use, several reductively activated prodrugs are in various stages of clinical trial. This review mainly focuses on the medicinal chemistry aspects of various classes of reductively activated prodrugs including design principles, structure-activity relationships, and mechanisms of activation and release of active drug molecules.
Collapse
Affiliation(s)
- Yu Chen
- Department of Pharmaceutical Chemistry, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | | |
Collapse
|
164
|
Le QTX, Moon J, Redman M, Williamson SK, Lara PN, Goldberg Z, Gaspar LE, Crowley JJ, Moore DF, Gandara DR. Phase II study of tirapazamine, cisplatin, and etoposide and concurrent thoracic radiotherapy for limited-stage small-cell lung cancer: SWOG 0222. J Clin Oncol 2009; 27:3014-9. [PMID: 19364954 PMCID: PMC2702233 DOI: 10.1200/jco.2008.21.3868] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 01/13/2009] [Indexed: 12/26/2022] Open
Abstract
PURPOSE A SWOG pilot study (S0004) showed that tirapazamine (TPZ) when combined with concurrent chemoradiotherapy yielded a promising median survival of 22 months in limited-stage small-cell lung cancer (LSCLC). We report results of the phase II study designed to confirm this result. PATIENTS AND METHODS The concurrent phase consisted of two cycles of cisplatin, etoposide, and once-daily radiation to 61 Gy. TPZ was given at 260 mg/m(2) on days 1, 29, and at 160 mg/m(2) on days 8, 10, 12, 36, 38, and 40. Consolidation consisted of two cycles of cisplatin and etoposide. Complete responders received prophylactic cranial irradiation. Results were considered promising if the median survival time was at least 21 months and of no further interest if < or = 14 months. RESULTS S0222 was closed early due to a report of excess toxicity for TPZ in a head and neck cancer trial elsewhere. Of planned 85 patients, 69 were accrued. In 68 assessable patients, 17 (25%) had grade 3 to 4 esophagitis and eight (12%) had grade 3 febrile neutropenia during the concurrent phase. There were three possible treatment-related deaths, two in concurrent phase (one progressive disease not otherwise specified within 30 days, one pericardial effusion) and one in consolidation phase (esophageal hemorrhage). At a median follow-up of 35 months, median progression-free survival was 11 months (95% CI, 10 to 13 months) and median overall survival was 21 months (95% CI, 17 to 33 months). CONCLUSION S0222 showed acceptable levels of toxicity and similar promising median survival as S0004. Further study of hypoxia-targeted therapy is warranted in LSCLC.
Collapse
|
165
|
Gu Y, Patterson AV, Atwell GJ, Chernikova SB, Brown JM, Thompson LH, Wilson WR. Roles of DNA repair and reductase activity in the cytotoxicity of the hypoxia-activated dinitrobenzamide mustard PR-104A. Mol Cancer Ther 2009; 8:1714-23. [PMID: 19509245 DOI: 10.1158/1535-7163.mct-08-1209] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PR-104 is a dinitrobenzamide mustard currently in clinical trial as a hypoxia-activated prodrug. Its major metabolite, PR-104A, is metabolized to the corresponding hydroxylamine (PR-104H) and amine (PR-104M), resulting in activation of the nitrogen mustard moiety. We characterize DNA damage responsible for cytotoxicity of PR-104A by comparing sensitivity of repair-defective hamster Chinese hamster ovary cell lines with their repair-competent counterparts. PR-104H showed a repair profile similar to the reference DNA cross-linking agents chlorambucil and mitomycin C, with marked hypersensitivity of XPF(-/-), ERCC1(-/-), and Rad51D(-/-) cells but not of XPD(-/-) or DNA-PK(CS)(-/-) cells. This pattern confirmed the expected dependence on the ERCC1-XPF endonuclease, implicated in unhooking DNA interstrand cross-links at blocked replication forks, and homologous recombination repair (HRR) in restarting collapsed forks. However, even under anoxia, the hypersensitivity of XPF(-/-), ERCC1(-/-), and Rad51D(-/-) cells to PR-104A itself was lower than for chlorambucil. To test whether this reflects inefficient PR-104A reduction, a soluble form of human NADPH:cytochrome P450 oxidoreductase was stably expressed in Rad51D(-/-) cells and their HRR-restored counterpart. This expression increased hypoxic metabolism of PR-104A to PR-104H and PR-104M as well as hypoxia-selective cytotoxicity of PR-104A and its dependence on HRR. We conclude that PR-104A cytotoxicity is primarily due to DNA interstrand cross-linking by its reduced metabolites, although under conditions of inefficient PR-104A reduction (low reductase expression or aerobic cells), a second mechanism contributes to cell killing. This study shows that hypoxia, reductase activity, and DNA interstrand cross-link repair proficiency are key variables that interact to determine PR-104A sensitivity.
Collapse
Affiliation(s)
- Yongchuan Gu
- Auckland Cancer Society Research Centre, The University of Auckland, Auckland, New Zealand
| | | | | | | | | | | | | |
Collapse
|
166
|
Ebbesen P, Pettersen EO, Gorr TA, Jobst G, Williams K, Kieninger J, Wenger RH, Pastorekova S, Dubois L, Lambin P, Wouters BG, Van Den Beucken T, Supuran CT, Poellinger L, Ratcliffe P, Kanopka A, Görlach A, Gasmann M, Harris AL, Maxwell P, Scozzafava A. Taking advantage of tumor cell adaptations to hypoxia for developing new tumor markers and treatment strategies. J Enzyme Inhib Med Chem 2009; 24 Suppl 1:1-39. [PMID: 19005871 DOI: 10.1080/14756360902784425] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cancer cells in hypoxic areas of solid tumors are to a large extent protected against the action of radiation as well as many chemotherapeutic drugs. There are, however, two different aspects of the problem caused by tumor hypoxia when cancer therapy is concerned: One is due to the chemical reactions that molecular oxygen enters into therapeutically targeted cells. This results in a direct chemical protection against therapy by the hypoxic microenvironment, which has little to do with cellular biological regulatory processes. This part of the protective effect of hypoxia has been known for more than half a century and has been studied extensively. However, in recent years there has been more focus on the other aspect of hypoxia, namely the effect of this microenvironmental condition on selecting cells with certain genetic prerequisites that are negative with respect to patient prognosis. There are adaptive mechanisms, where hypoxia induces regulatory cascades in cells resulting in a changed metabolism or changes in extracellular signaling. These processes may lead to changes in cellular intrinsic sensitivity to treatment irrespective of oxygenation and, furthermore, may also have consequences for tissue organization. Thus, the adaptive mechanisms induced by hypoxia itself may have a selective effect on cells, with a fine-tuned protection against damage and stress of many kinds. It therefore could be that the adaptive mechanisms may take advantage of for new tumor labeling/imaging and treatment strategies. One of the Achilles' heels of hypoxia research has always been the exact measurements of tissue oxygenation as well as the control of oxygenation in biological tumor models. Thus, development of technology that can ease this control is vital in order to study mechanisms and perform drug development under relevant conditions. An integrated EU Framework project 2004-2009, termed EUROXY, demonstrates several pathways involved in transcription and translation control of the hypoxic cell phenotype and evidence of cross-talk with responses to pH and redox changes. The carbonic anhydrase isoenzyme CA IX was selected for further studies due to its expression on the surface of many types of hypoxic tumors. The effort has led to marketable culture flasks with sensors and incubation equipment, and the synthesis of new drug candidates against new molecular targets. New labeling/imaging methods for cancer diagnosing and imaging of hypoxic cancer tissue are now being tested in xenograft models and are also in early clinical testing, while new potential anti-cancer drugs are undergoing tests using xenografted tumor cancers. The present article describes the above results in individual consortium partner presentations.
Collapse
Affiliation(s)
- Peter Ebbesen
- Laboratory for Stem Cell Research, Aalborg University, Aarhus, Denmark.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
167
|
Das BC, Madhukumar AV, Anguiano J, Mani S. Design, synthesis and biological evaluation of 2H-benzo[b][1,4] oxazine derivatives as hypoxia targeted compounds for cancer therapeutics. Bioorg Med Chem Lett 2009; 19:4204-6. [PMID: 19515559 DOI: 10.1016/j.bmcl.2009.05.110] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 05/25/2009] [Accepted: 05/27/2009] [Indexed: 11/28/2022]
Abstract
A small library of 2H-benzo[b][1,4] oxazine derivative was synthesized and their biological activity was tested on HepG2 cells under normoxic and hypoxic conditions. From preliminary screening, we found compound 10 and 11 specifically inhibit hypoxic cancer cell growth IC(50) 87+/-1.8microM and IC(50) 10+/-3.7microM while sparing 'normoxic' cells IC(50) >600M and >1mM (not applicable), respectively. We tested the effect of 10 on MTT, clonogenic and hypoxia induced genes. The MTT correlates with clonogenic assays and most importantly compound 10 down regulates hypoxia induces genes (HIF-1alpha, P21 and VEGF) appropriately. We are in the process to explore the molecular mechanism of action of oxazine derivative compounds on hypoxia tumor cells.
Collapse
Affiliation(s)
- Bhaskar C Das
- Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | | | | | | |
Collapse
|
168
|
Bischoff P, Altmeyer A, Dumont F. Radiosensitising agents for the radiotherapy of cancer: advances in traditional and hypoxia targeted radiosensitisers. Expert Opin Ther Pat 2009; 19:643-62. [DOI: 10.1517/13543770902824172] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
169
|
Singleton RS, Guise CP, Ferry DM, Pullen SM, Dorie MJ, Brown JM, Patterson AV, Wilson WR. DNA Cross-Links in Human Tumor Cells Exposed to the Prodrug PR-104A: Relationships to Hypoxia, Bioreductive Metabolism, and Cytotoxicity. Cancer Res 2009; 69:3884-91. [DOI: 10.1158/0008-5472.can-08-4023] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
170
|
Liu SC, Ahn GO, Kioi M, Dorie MJ, Patterson AV, Brown JM. Optimized clostridium-directed enzyme prodrug therapy improves the antitumor activity of the novel DNA cross-linking agent PR-104. Cancer Res 2008; 68:7995-8003. [PMID: 18829557 PMCID: PMC2596930 DOI: 10.1158/0008-5472.can-08-1698] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We have previously shown that spores of the nonpathogenic clostridial strain C. sporogenes genetically engineered to express the E. coli-derived cytosine deaminase gene are effective in converting systemically injected nontoxic 5-fluorocytosine into the toxic anticancer drug 5-fluorouracil, thereby producing tumor-specific antitumor activity. To improve the expression of E. coli-derived genes with this system, we first replaced the original fdP promoter in the vector with one of two powerful endogenous clostridial promoters: that of the thiolase gene (thlP) and that for the clostridial transcription factor abrB310 (abrBP). These substitutions improved protein expression levels of the prodrug-activating genes by 2- to 3-fold in comparison with fdP-driven expression. However, despite these strong promoters, we found much higher expression of the nitroreductase (NTR) protein in the E. coli host compared with the clostridial host, which we hypothesized could be the result of different codon use between the two organisms. To test this, we constructed new expression vectors with an artificially synthesized NTR gene using optimized clostridial codons (sNTR). Results from both enzymatic assays and Western blots of cell extracts from clostridial transformants harboring plasmid constructs of thlP-sNTR and abrBP-sNTR showed that the expression and activity of the NTR gene product was increased by approximately 20-fold compared with the original construct. In vivo studies with i.v. administered sNTR-expressing C. sporogenes spores in SiHa tumor-bearing mice showed significantly improved antitumor efficacy when combined with either 5-aziridinyl-2,4-dinitrobenzamide (CB1954) or the novel dinitrobenzamide mustard prodrug, PR-104.
Collapse
Affiliation(s)
- Shie-Chau Liu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California, USA
| | | | | | | | | | | |
Collapse
|
171
|
Abstract
Hypoxia, a condition of insufficient O2 to support metabolism, occurs when the vascular supply is interrupted, as in stroke or myocardial infarction, or when a tumor outgrows its vascular supply. When otherwise healthy tissues lose their O2 supply acutely, the cells usually die, whereas when cells gradually become hypoxic, they adapt by up-regulating the production of numerous proteins that promote their survival. These proteins slow the rate of growth, switch the mitochondria to glycolysis, stimulate growth of new vasculature, inhibit apoptosis, and promote metastatic spread. The consequence of these changes is that patients with hypoxic tumors invariably experience poor outcome to treatment. This has led the molecular imaging community to develop assays for hypoxia in patients, including regional measurements from O2 electrodes placed under CT guidance, several nuclear medicine approaches with imaging agents that accumulate with an inverse relationship to O2, MRI methods that measure either oxygenation directly or lactate production as a consequence of hypoxia, and optical methods with NIR and bioluminescence. The advantages and disadvantages of these approaches are reviewed, along with the individual strategies for validating different imaging methods. Ultimately the proof of value is in the clinical performance to predict outcome, select an appropriate cohort of patients to benefit from a hypoxia-directed treatment, or plan radiation fields that result in better local control. Hypoxia imaging in support of molecular medicine has become an important success story over the last decade and provides a model and some important lessons for development of new molecular imaging probes or techniques.
Collapse
Affiliation(s)
- Kenneth A Krohn
- Department of Radiology, University of Washington, Seattle, Washington 98195-6004, USA.
| | | | | |
Collapse
|
172
|
Lee NY, Le QT. New developments in radiation therapy for head and neck cancer: intensity-modulated radiation therapy and hypoxia targeting. Semin Oncol 2008; 35:236-50. [PMID: 18544439 DOI: 10.1053/j.seminoncol.2008.03.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Intensity-modulated radiation therapy (IMRT) has revolutionized radiation treatment for head and neck cancers (HNCs). When compared to the traditional techniques, IMRT has the unique ability to minimize the dose delivered to normal tissues without compromising tumor coverage. As a result, side effects from high-dose radiation have decreased and patient quality of life has improved. In addition to toxicity reduction, excellent clinical outcomes have been reported for IMRT. The first part of this review will focus on clinical results of IMRT for HNC. Tumor hypoxia, or the condition of low oxygen, is a key factor for tumor progression and treatment resistance. Hypoxia develops in solid tumors due to aberrant blood vessel formation, fluctuation in blood flow, and increasing oxygen demands for tumor growth. Because hypoxic tumor cells are more resistant to ionizing radiation, hypoxia has been a focus of clinical research in radiation therapy for half a decade. Interest for targeting tumor hypoxia has waxed and waned as promising treatments emerged from the laboratory, only to fail in the clinics. However, with the development of new technologies, the prospect of targeting tumor hypoxia is more tangible. The second half of the review will focus on approaches for assessing tumor hypoxia and on the strategies for targeting this important microenvironmental factor in HNC.
Collapse
Affiliation(s)
- Nancy Y Lee
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | | |
Collapse
|
173
|
Lee NY, Le QT. New developments in radiation therapy for head and neck cancer: intensity-modulated radiation therapy and hypoxia targeting. Semin Oncol 2008. [PMID: 18544439 DOI: 10.1053/j.seminoncol.2008.03.00332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Intensity-modulated radiation therapy (IMRT) has revolutionized radiation treatment for head and neck cancers (HNCs). When compared to the traditional techniques, IMRT has the unique ability to minimize the dose delivered to normal tissues without compromising tumor coverage. As a result, side effects from high-dose radiation have decreased and patient quality of life has improved. In addition to toxicity reduction, excellent clinical outcomes have been reported for IMRT. The first part of this review will focus on clinical results of IMRT for HNC. Tumor hypoxia, or the condition of low oxygen, is a key factor for tumor progression and treatment resistance. Hypoxia develops in solid tumors due to aberrant blood vessel formation, fluctuation in blood flow, and increasing oxygen demands for tumor growth. Because hypoxic tumor cells are more resistant to ionizing radiation, hypoxia has been a focus of clinical research in radiation therapy for half a decade. Interest for targeting tumor hypoxia has waxed and waned as promising treatments emerged from the laboratory, only to fail in the clinics. However, with the development of new technologies, the prospect of targeting tumor hypoxia is more tangible. The second half of the review will focus on approaches for assessing tumor hypoxia and on the strategies for targeting this important microenvironmental factor in HNC.
Collapse
Affiliation(s)
- Nancy Y Lee
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | | |
Collapse
|
174
|
Duan JX, Jiao H, Kaizerman J, Stanton T, Evans JW, Lan L, Lorente G, Banica M, Jung D, Wang J, Ma H, Li X, Yang Z, Hoffman RM, Ammons WS, Hart CP, Matteucci M. Potent and highly selective hypoxia-activated achiral phosphoramidate mustards as anticancer drugs. J Med Chem 2008; 51:2412-20. [PMID: 18257544 DOI: 10.1021/jm701028q] [Citation(s) in RCA: 176] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A series of achiral hypoxia-activated prodrugs were synthesized on the basis of the DNA cross-linking toxin of the prodrug, ifosfamide. The hypoxia-selective cytotoxicity of several of the compounds was improved over previously reported racemic mixtures of chiral bioreductive phosphoramidate prodrugs. Prodrugs activated by 2-nitroimidazole reduction demonstrated up to 400-fold enhanced cytotoxicity toward H460 cells in culture under hypoxia versus their potency under aerobic conditions. Compounds were further assessed for their stability to cytochrome P450 metabolism using a liver microsome assay. The 2-nitroimidazole containing lead compound 3b (TH-302) was selectively potent under hypoxia and stable to liver microsomes. It was active in an in vivo MIA PaCa-2 pancreatic cancer orthotopic xenograft model as a monotherapy and demonstrated dramatic efficacy when used in combination with gemcitabine, extending survival with one of eight animals tumor free at day-44. Compound 3b has emerged as a promising antitumor agent that shows excellent in vivo efficacy and is currently being evaluated in the clinic.
Collapse
Affiliation(s)
- Jian-Xin Duan
- Threshold Pharmaceuticals, 1300 Seaport Boulevard, Suite 500, Redwood City, California 94063, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
175
|
Pruijn FB, Patel K, Hay MP, Wilson WR, Hicks KO. Prediction of Tumour Tissue Diffusion Coefficients of Hypoxia-Activated Prodrugs from Physicochemical Parameters. Aust J Chem 2008. [DOI: 10.1071/ch08240] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The therapeutic activity of anticancer agents depends critically on their ability to penetrate through tumour tissue to reach their target cells, a requirement that is especially important for hypoxia-activated prodrugs. Here we use multicellular layers (MCL) grown in vitro from HT29 colon carcinoma cells to measure tissue diffusion coefficients (Dmcl) of 67 structurally diverse benzotriazine di-N-oxides (analogues of the hypoxia-activated prodrug tirapazamine) plus four miscellaneous compounds. An algorithm was developed to predict Dmcl from physicochemical parameters (molecular weight, octanol/water partition coefficient at pH 7.4, number of hydrogen bond donors and acceptors); the fitted multivariate relationship had an explained variance (R2) of 0.907 and predictive power (Q2) of 0.879. Using a subset of nine compounds tested as a single cassette, the algorithm was shown to apply, with some adjustment of coefficients, to MCLs from three other tumour cell lines with differing cell packing densities (SiHa, HCT8-Ea, and HCT8-Ra). The demonstrated relationships provide tools for optimizing extravascular transport of anticancer agents during lead optimization.
Collapse
|
176
|
Abstract
The physiological differences between solid tumours and the healthy tissues and organs of the body are both an impediment to effective treatment and a potential basis for targeting strategies. In the present review, we outline the physiological features that distinguish tumours including hypoxia, acidity, and inhibited transport and describe the strategies being employed to exploit these differences in order to generate more selective and less toxic anticancer agents.
Collapse
|
177
|
Helsby NA, Goldthorpe MA, Tang MHY, Atwell GJ, Smith EM, Wilson WR, Tingle MD. Influence of mustard group structure on pathways of in vitro metabolism of anticancer N-(2-hydroxyethyl)-3,5-dinitrobenzamide 2-mustard prodrugs. Drug Metab Dispos 2007; 36:353-60. [PMID: 17998296 DOI: 10.1124/dmd.107.018739] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The dinitrobenzamide mustards are a class of bioreductive nitro-aromatic anticancer prodrugs, of which a phosphorylated analog (PR-104) is currently in clinical development. They are bioactivated by tumor reductases to form DNA cross-linking cytotoxins. However, their biotransformation in normal tissues has not been examined. Here we report the aerobic in vitro metabolism of three N-(2 hydroxyethyl)-3,5-dinitrobenzamide 2-mustards and the corresponding nonmustard analog in human, mouse, rat, and dog hepatic S9 preparations. These compounds have a range of mustard structures (-N(CH(2)CH(2)X)(2) where X = H, Cl, Br, or OSO(2)Me). Four metabolic routes were identified: reduction of either nitro group, N-dealkylation of the mustard, plus O-acetylation, and O-glucuronidation of the hydroxyethyl side chain. Reduction of the nitro group ortho to the mustard resulted in intramolecular alkylation and is considered to be an inactivation pathway, whereas reduction of the nitro group para to the mustard generated potential DNA cross-linking cytotoxins. N-Dealkylation inactivated the mustard moiety but may result in the formation of toxic acetaldehyde derivatives. Increasing the size of the nitrogen mustard leaving group abrogated the ortho-nitroreduction and N-dealkylation routes and thereby improved overall metabolic stability but had little effect on aerobic para-nitroreduction. All four compounds underwent O-glucuronidation of the hydroxyethyl side chain and further studies to elucidate the relative importance of this pathway in vivo are in progress.
Collapse
Affiliation(s)
- Nuala A Helsby
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
| | | | | | | | | | | | | |
Collapse
|
178
|
Singleton DC, Li D, Bai SY, Syddall SP, Smaill JB, Shen Y, Denny WA, Wilson WR, Patterson AV. The nitroreductase prodrug SN 28343 enhances the potency of systemically administered armed oncolytic adenovirus ONYX-411NTR. Cancer Gene Ther 2007; 14:953-67. [DOI: 10.1038/sj.cgt.7701088] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
179
|
Tang MHY, Helsby NA, Goldthorpe MA, Thompson KM, Al-Ali S, Tingle MD. Hepatic nitroreduction, toxicity and toxicokinetics of the anti-tumour prodrug CB 1954 in mouse and rat. Toxicology 2007; 240:70-85. [PMID: 17804142 DOI: 10.1016/j.tox.2007.07.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 07/19/2007] [Accepted: 07/19/2007] [Indexed: 11/22/2022]
Abstract
5-(Aziridin-1-yl)-2,4-dinitrobenzamide (CB 1954), a promising anti-tumour compound, is associated with clinical hepatotoxicity. We have previously demonstrated that human liver preparations are capable of endogenous 2- and 4-nitroreduction of CB 1954 to generate highly potent cytotoxins. The present study initially examined the in vitro metabolism of CB 1954 in S9 preparations of several non-clinical species and strains. The CD-1 nu/nu mouse and Sprague-Dawley rat were subsequently chosen for further assessment of in vivo metabolism and hepatotoxicity of CB 1954, as well as the mechanisms that may be involved. Animals were administered the maximum tolerated dose (MTD). At 562 micromol/kg, the mouse exhibited transaminase elevation and centrilobular hepatocyte injury. Moreover, thiol adducts as well as hepatic glutathione depletion paralleled temporally by maximal nitroreduction were observed. The rat had a much lower MTD of 40 micromol/kg and showed signs of gastro-intestinal disturbances. In contrast to mouse, peri-portal damage and biliary changes were observed in rat without any alterations in plasma biomarkers or hepatic glutathione levels. Immunohistochemical analysis did not reveal any correlation between the location of injury and expression of cytochrome P450 reductase and NAD(P)H quinone oxidoreductase 1, two enzymes implicated in the bioactivation of this drug. In conclusion, the present study showed that following administration of CB 1954 at the respective MTDs, hepatotoxicity was observed in both mouse and rat. However, the degree of sensitivity to the drug and the mechanisms of toxicity involved appear to be widely different between CD-1 nu/nu mice and Sprague-Dawley rats.
Collapse
Affiliation(s)
- Magdalene Huen Yin Tang
- Department of Pharmacology and Clinical Pharmacology, University of Auckland, Private Bag 92019, Auckland, New Zealand.
| | | | | | | | | | | |
Collapse
|
180
|
Hicks KO, Myint H, Patterson AV, Pruijn FB, Siim BG, Patel K, Wilson WR. Oxygen Dependence and Extravascular Transport of Hypoxia-Activated Prodrugs: Comparison of the Dinitrobenzamide Mustard PR-104A and Tirapazamine. Int J Radiat Oncol Biol Phys 2007; 69:560-71. [PMID: 17869669 DOI: 10.1016/j.ijrobp.2007.05.049] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2007] [Revised: 05/28/2007] [Accepted: 05/29/2007] [Indexed: 10/22/2022]
Abstract
PURPOSE To compare oxygen dependence and tissue transport properties of a new hypoxia-activated prodrug, PR-104A, with tirapazamine, and to evaluate the implications for antitumor activity when combined with radiotherapy. METHODS AND MATERIALS Oxygen dependence of cytotoxicity was measured by clonogenic assay in SiHa cell suspensions. Tissue transport parameters were determined using SiHa multicellular layers. Spatially resolved pharmacokinetic (PK) and pharmacodynamic (PD) models were developed to predict cell killing in SiHa tumors and tested by clonogenic assay 18 h after treatment with the corresponding phosphate ester, PR-104. RESULTS The K-value (oxygen concentration to halve cytotoxic potency) of PR-104A was 0.126 +/- 0.021 microM (10-fold lower than tirapazamine at 1.30 +/- 0.28 microM). The diffusion coefficient of PR-104A in multicellular layers (4.42 +/- 0.15 x 10(-7) cm2 s(-1)) was lower than that of tirapazamine (1.30 +/- 0.05 x 10(-6) cm2 s(-1)) but PK modeling predicted better penetration to hypoxic cells in tumors because of its slower metabolism. The tirapazamine PK/PD model successfully predicted the measured activity in combination with single-dose radiation against SiHa tumors, and the PR-104A model underpredicted the activity, which was greater for PR-104 than for tirapazamine (at equivalent host toxicity) both with radiation and as a single agent. CONCLUSION PR-104/PR-104A has different PK/PD properties from tirapazamine and superior activity with single-dose radiotherapy against SiHa xenografts. We have inferred that PR-104A is better able to kill cells at intermediate partial pressure of oxygen in tumors than implied by the PK/PD model, most likely because of a bystander effect resulting from diffusion of its activated metabolites from severely hypoxic zones.
Collapse
Affiliation(s)
- Kevin O Hicks
- Auckland Cancer Society Research Centre, University of Auckland School of Medical Sciences, Auckland, New Zealand.
| | | | | | | | | | | | | |
Collapse
|
181
|
Patel K, Lewiston D, Gu Y, Hicks KO, Wilson WR. Analysis of the hypoxia-activated dinitrobenzamide mustard phosphate pre-prodrug PR-104 and its alcohol metabolite PR-104A in plasma and tissues by liquid chromatography–mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 856:302-11. [PMID: 17644498 DOI: 10.1016/j.jchromb.2007.06.035] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 06/15/2007] [Accepted: 06/19/2007] [Indexed: 11/16/2022]
Abstract
PR-104 is a dinitrobenzamide mustard pre-prodrug that is activated by reduction to a cytotoxic hydroxylamine metabolite in hypoxic tumour cells; it has recently commenced Phase I clinical trial. Here, we report two validated methods for the determination of PR-104 and its alcohol hydrolysis product, PR-104A in plasma and tissues across species. A high pH LC/MS/MS method was optimised for rapid and sensitive analysis of both analytes in rat, dog and human plasma. This assay was linear over the concentration range 0.005-2.5 microg/ml for PR-104 and 0.05-25 microg/ml for PR-104A (0.005-2.5 microg/ml for rat). A second method, using a low pH LC separation, was designed to provide higher chromatographic resolution, facilitating identification of metabolites. Both methods were successfully applied to the plasma pharmacokinetics of PR-104 and PR-104A in rats. In addition, cytotoxic reduced metabolites of PR-104A were identified in human tumour xenografts by the higher chromatographic resolution method.
Collapse
Affiliation(s)
- Kashyap Patel
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Auckland, New Zealand
| | | | | | | | | |
Collapse
|
182
|
Guise CP, Wang AT, Theil A, Bridewell DJ, Wilson WR, Patterson AV. Identification of human reductases that activate the dinitrobenzamide mustard prodrug PR-104A: a role for NADPH:cytochrome P450 oxidoreductase under hypoxia. Biochem Pharmacol 2007; 74:810-20. [PMID: 17645874 DOI: 10.1016/j.bcp.2007.06.014] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 05/26/2007] [Accepted: 06/11/2007] [Indexed: 11/26/2022]
Abstract
Hypoxia is a common trait found in many solid tumours and thus represents a therapeutic target with considerable potential. PR-104, a hypoxia-activated prodrug currently in clinical trial, is a water-soluble phosphate ester which is converted in vivo to the corresponding alcohol, PR-104A. This 3,5-dinitrobenzamide-2-nitrogen mustard is activated by reduction to the corresponding 5-hydroxylamine (PR-104H) and 5-amine (PR-104M) in hypoxic cells. The clinical effectiveness of PR-104 will depend in part on the expression of reductases within tumours that can effect this reduction. Here, we evaluate the roles of NADPH:cytochrome P450 oxidoreductase (CYPOR; E.C.1.6.2.4) and NAD(P)H:quinone oxidoreductase (NQO1; E.C.1.6.99.2) as candidate PR-104A reductases. A weak correlation was observed between NQO1 activity and aerobic cytotoxicity in a panel of eight tumour cell lines. However, overexpression of human NQO1 did not increase cytotoxicity of PR-104A or the formation of PR-104H/M, showing that PR-104A is not a substrate for NQO1. Overexpression of human CYPOR did, however, increase the hypoxic cytotoxicity of PR-104A, and its metabolism to PR-104H and PR-104M, demonstrating it to be a PR-104A reductase. To assess the contribution of CYPOR to overall activation of PR-104A in hypoxic SiHa cells, a combination of siRNA transfection and antisense expression were used to suppress CYPOR protein by 91% (+/-3%), a phenotype which conferred 45% (+/-7%) decrease in cytotoxic potency of PR-104A. Regression analysis of all CYPOR depletion data was found to correlate with cytoprotection and metabolism (p<0.001). Residual PR-104A reductase activity could be inhibited by the flavoprotein inhibitor diphenyliodonium. We conclude that CYPOR is an important PR-104A reductase, but that other flavoenzymes also contribute to its activation in hypoxic SiHa cells.
Collapse
Affiliation(s)
- Chris P Guise
- Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland, New Zealand
| | | | | | | | | | | |
Collapse
|