201
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Du W, Curran DP, Bevins RL, Zimmer SG, Zhang J, Burke TG. Synthesis and evaluation of a novel E-ring modified alpha-hydroxy keto ether analogue of camptothecin. Bioorg Med Chem 2002; 10:103-10. [PMID: 11738612 DOI: 10.1016/s0968-0896(01)00252-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The synthesis of a novel E-ring modified keto ether analogue of camptothecin and homocamptothecin by the cascade radical annulation route is reported. The analogue, Du1441, is an isomer of homocamptothecin, but includes the alpha-hydroxy carbonyl functionality that camptothecin possesses and homocamptothecin lacks. Despite these similarities, the new keto ether analogue is inactive in cell assays, and implications for the structure/activity relationship are discussed.
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Affiliation(s)
- Wu Du
- University of Pittsburgh, Department of Chemistry, Pittsburgh, PA 15260, USA
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202
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Boucaud M, Pinguet F, Poujol S, Romieu G, Cupissol D, Astre C, Culine S, Bressolle F. Salivary and plasma pharmacokinetics of topotecan in patients with metastatic epithelial ovarian cancer. Eur J Cancer 2001; 37:2357-64. [PMID: 11720828 DOI: 10.1016/s0959-8049(01)00312-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The comparative saliva/plasma pharmacokinetics of topotecan were investigated in 13 patients with metastatic epithelial ovarian cancer receiving topotecan (30-min intravenous (i.v.) infusion) on a five consecutive day schedule every 3 weeks. During the first and the second courses of treatment, each patient underwent pharmacokinetic evaluation. Quantitation of the total topotecan (lactone plus carboxylate form) was assessed by a highly specific high-performance liquid chromatographic (HPLC) method. Large patient-to-patient variations in the plasma and saliva concentrations were observed. Plasma and saliva pharmacokinetics could be described using a biexponential pattern. From the saliva data, the half-life of the terminal part of the curve was 2.64 h, it was of the same order of magnitude as the topotecan elimination half-life determined from the plasma data, 3.18 h. Topotecan concentrations were higher in the saliva than in the plasma, the saliva/plasma concentration ratio averaged 2.31 and the ratio area under the parotid saliva (AUC(s)) over plasma (AUC(p)) concentration-time curve (AUC(s)/AUC(p)) averaged 2.11. For each individual, a significant relationship was found between topotecan concentrations in the saliva and in the plasma, the coefficients of correlation ranged from 0.75 to 0.92 according to the patient. Myelosuppression, especially granulocytopenia was the most frequent toxicity encountered during the trial. The percent decrease in the leucocyte count, absolute neutrophil count and platelet count were related to the AUCp/day using sigmoidal E(max) models. The high values of the Hill constant found reflect the very steep AUC-haematoxicity relationship observed. In most cases, abdominal pain occurred in patients presenting high saliva concentrations. One patient with high salivary concentrations (mean S/P ratio=4.60) had grade 1 mucositis. In conclusion, the concentration of topotecan in saliva appeared to be useful as an indirect, non-invasive estimation of the levels of topotecan in the plasma; thus, saliva concentrations could be a good predictor of the behaviour of topotecan in the body.
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Affiliation(s)
- M Boucaud
- Onco-Pharmacology Department, Pharmacy Service, Centre Régional de Lutte contre le cancer, 34298 Montpellier Cedex 5, France
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203
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Abstract
DNA topoisomerases are essential enzymes that regulate the conformational changes in DNA topology by catalysing the concerted breakage and rejoining of DNA strands during normal cellular growth. Over the past few years there has been considerable pharmacological interest in these enzymes because inhibitors of DNA topoisomerases represent a major class of anticancer drugs. This review highlights topoisomerase-targeting drugs that have shown promising anticancer activities. The mechanisms by which those drugs interfere with the catalytic cycles of type I and type II DNA topoisomerases and the factors involved in the development of resistance to these drugs are discussed.
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Affiliation(s)
- Z Topcu
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Ege University, 35100 Izmir, Turkey.
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204
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Zufía L, Aldaz A, Giráldez J. Separation methods for camptothecin and related compounds. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2001; 764:141-59. [PMID: 11817025 DOI: 10.1016/s0378-4347(01)00319-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This paper reviews working procedures for the analytical determination of camptothecin and analogues. We give an overview of aspects such as the chemistry, structure-activity relationships, stability and mechanism of action of these antitumor compounds. The main body of the review describes separation techniques. Sample treatment and factors influencing high-performance liquid chromatography development are delineated. Published high-performance liquid chromatographic methods are summarized to demonstrate the variability and versatility of separation techniques and a critical evaluation of separation efficiency, detection sensitivity and specificity of these methods is reported.
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Affiliation(s)
- L Zufía
- Pharmacy Department, University Hospital of Navarra, Pamplona, Spain
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205
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Fan Y, Shi LM, Kohn KW, Pommier Y, Weinstein JN. Quantitative structure-antitumor activity relationships of camptothecin analogues: cluster analysis and genetic algorithm-based studies. J Med Chem 2001; 44:3254-63. [PMID: 11563924 DOI: 10.1021/jm0005151] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Topoisomerase 1 (top1) inhibitors are proving useful against a range of refractory tumors, and there is considerable interest in the development of additional top1 agents. Despite crystallographic studies, the binding site and ligand properties that lead to activity are poorly understood. Here we report a unique approach to quantitative structure-activity relationship (QSAR) analysis based on the National Cancer Institute's (NCI) drug databases. In 1990, the NCI established a drug discovery program in which compounds are tested for their ability to inhibit the growth of 60 different human cancer cell lines in culture. More than 70 000 compounds have been screened, and patterns of activity against the 60 cell lines have been found to encode rich information on mechanisms of drug action and drug resistance. Here, we use hierarchical clustering to define antitumor activity patterns in a data set of 167 tested camptothecins (CPTs) in the NCI drug database. The average pairwise Pearson correlation coefficient between activity patterns for the CPT set was 0.70. Coherence between chemical structures and their activity patterns was observed. QSAR studies were carried out using the mean 50% growth inhibitory concentrations (GI(50)) for 60 cell lines as the dependent variables. Different statistical methods, including stepwise linear regression, principal component regression (PCR), partial least-squares regression (PLS), and fully cross-validated genetic function approximation (GFA) were applied to construct quantitative structure-antitumor relationship models. For our data set, the GFA method performed better in terms of correlation coefficients and cross-validation analysis. A number of molecular descriptors were identified as being correlated with antitumor activity. Included were partial atomic charges and three interatomic distances that define the relative spatial dispositions of three significant atoms (the hydroxyl hydrogen of the E-ring, the lactone carbonyl oxygen of the E-ring, and the carbonyl oxygen of the D-ring). The cross-validated r(2) for the final GFA model was 0.783, indicating a predictive QSAR model.
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Affiliation(s)
- Y Fan
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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206
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Jung LL, Zamboni WC. Cellular, pharmacokinetic, and pharmacodynamic aspects of response to camptothecins: can we improve it? Drug Resist Updat 2001; 4:273-88. [PMID: 11998845 DOI: 10.1054/drup.2001.0222] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The camptothecins provide a novel class of effective anticancer agents that exert their action against DNA topoisomerase I. Members of the camptothecins include topotecan, irinotecan, 9-aminocamptothecin, and 9-nitrocamptothecin, which are analogs of the plant alkaloid 20(S)-camptothecin. These agents vary in their antitumor efficacy and toxicity. Several pharmacokinetic and pharmacodynamic factors including cellular efflux, modulation of topoisomerases I and II, lactone stability, alterations in metabolism, and drug-drug interactions, influence the antitumor response and toxicity of these agents. Preclinical studies suggest that protracted schedules of administration produce greater antitumor effect than bolus administration. However, the optimal treatment regimens and administration schedules of these agents have yet to be established in clinical studies.
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Affiliation(s)
- L L Jung
- University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA
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207
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Kumar V, Kang J, Hohl RJ. Improved dissolution and cytotoxicity of camptothecin incorporated into oxidized-cellulose microspheres prepared by spray drying. Pharm Dev Technol 2001; 6:459-67. [PMID: 11485187 DOI: 10.1081/pdt-100002254] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Oxidized celluloses (OC) containing 7, 13, and 20% carboxylic content (OC-7, OC-13, and OC-20, respectively) have been converted into aqueous colloidal dispersions and used to prepare microspheres of the antineoplastic agent camptothecin (CPT) by spray drying. Plasticizers used were glycerin, polyethylene glycol 400 (PEG-400), and polyethylene glycol 6000 (PEG-6000). Irrespective of the carboxyiic content of OC and the nature of plasticizer employed, the size of microspheres varied from 1.25+/-0.40 to 1.52+/-0.47 microm. The release studies in pH 7.4 buffer revealed the dissolution of CPT to be faster from the microsphere formulations than from physical mixtures and free CPT. The times to release 50% CPT (T-50%) from microspheres prepared using OC-7, OC-13, and OC-20 were about 31, 37, and 19 h, respectively. The in vitro cytotoxicity results indicated OC-20/CPT microspheres to be more effective than free CPT against human-derived RPMI-8402 lymphoid and THP-1 myeloid leukemia cell lines. The ED50 values for the OC-20/CPT microspheres and free CPT were 1 x 10(-5) and 0.25 x 10(-1) microg/mL, respectively, against the RPMI-8402 line and 0.5 x 10(-2) and 0.75 microg/mL, respectively, against the THP-1 line. The higher activity of OC-20/CPT microspheres compared to that of the free drug is attributed to increased dissolution of CPT from microspheres.
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Affiliation(s)
- V Kumar
- Pharmaceutics Division, College of Pharmacy, The University of Iowa, Iowa City 52242, USA.
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208
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Kim DK, Ryu DH, Lee JY, Lee N, Kim YW, Kim JS, Chang K, Im GJ, Kim TK, Choi WS. Synthesis and biological evaluation of novel A-ring modified hexacyclic camptothecin analogues. J Med Chem 2001; 44:1594-602. [PMID: 11334569 DOI: 10.1021/jm0004751] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Eleven A-ring modified hexacyclic analogues of camptothecin (CPT) containing a 1,4-oxazine ring were synthesized from 10-hydroxycamptothecin (11a) and 7-ethyl-10-hydroxycamptothecin (3) (SN-38) in four to five steps and were subjected to the biological tests such as cytotoxicity, topoisomerase I (Topo I) inhibitory activity, acetylcholinesterase (AChE) inhibition, and stability in human plasma. Four compounds 15a, 15b, 16a, and 16c were about 2-fold more potent than topotecan and as potent as CPT toward human cancer cell lines A549, H128, WiDr, MKN45, SK-OV-3, and SK-BR-3 in vitro, even though the most active compound 15b was slightly less potent than SN-38. The potency of Topo I inhibition of these compounds showed relatively good correlation with their cytotoxicity. Most of the compounds exhibited AChE inhibitory activity weaker (9 +/- 2 to 20 +/- 3%) than CPT (23 +/- 5%) or topotecan (20 +/- 4%) and similar to SN-38 (13 +/- 2%), indicating that they might have little effect on causing early diarrhea. The stability of lactone forms of these compounds in human plasma seemed to be much higher than that of CPT and similar to that of topotecan but lower than that of SN-38. Among the new hexacyclic CPT analogues, compound 15b showed higher antitumor activity against human tumor xenograft, WiDr, in nude mice compared to that of SN-38. The most promising compound 15b has been selected for further development.
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Affiliation(s)
- D K Kim
- Life Science Research Center, SK Chemicals, 600 Jungja-Dong, Changan-Ku, Suwon-Si, Kyungki-Do 440-745, Korea.
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209
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Abstract
By uncoupling the cleavage and ligation reactions of DNA oligonucleotides mediated by topoisomerase I, it has been possible to demonstrate modification of DNA oligonucleotide structure by the enzyme. These modifications indicate an unusual flexibility inherent in the behavior of topoisomerase I and may reflect some of the cellular roles played by the enzyme. The ability of individual camptothecin analogues to inhibit these modification processes differentially provides insight into the relative nature of the microenvironments present. To the extent that these enzyme-mediated structural modifications do constitute models of cellular roles for the enzyme, the observed differential inhibition also provides a potential strategy for assessing the function and importance of such modifications.
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Affiliation(s)
- S M Hecht
- Departments of Chemistry and Biology, University of Virginia, Charlottesville, Virginia 22901, USA.
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210
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Burke TG, Bom D. Camptothecin design and delivery approaches for elevating anti-topoisomerase I activities in vivo. Ann N Y Acad Sci 2001; 922:36-45. [PMID: 11193923 DOI: 10.1111/j.1749-6632.2000.tb07023.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The camptothecins as a class have exhibited unique dynamics and reactivity in vivo, with respect to both drug hydrolysis and blood protein interactions. These factors have confounded their pharmaceutical development and clinical implementation. Recent bench and clinical research alike indicates that the combination of medicinal chemical and drug delivery approaches has been and will continue to be highly valuable in improving the overall therapeutic indices of camptothecin-based anti-topoisomerase I therapies. In the future the development of camptothecin analogues that exhibit highly specific human albumin interactions will likely be avoided, and agents such as the highly lipophilic DB-67 analogue with improved tissue stability will be evaluated. Drug delivery scientists will also devise better ways of targeting camptothecin therapies to solid tumors by using carriers such as tumor-targeted long-circulating liposomes.
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Affiliation(s)
- T G Burke
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky Medical Center, Lexington, Kentucky, USA.
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211
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Kohn KW, Pommier Y. Molecular and biological determinants of the cytotoxic actions of camptothecins. Perspective for the development of new topoisomerase I inhibitors. Ann N Y Acad Sci 2001; 922:11-26. [PMID: 11193886 DOI: 10.1111/j.1749-6632.2000.tb07021.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Camptothecin, originally discovered in 1957 as an antitumor activity in plant extracts, has recently become one of the most promising leads to new anticancer drugs. After lingering for many years, interest in camptothecin was revitalized in 1985 upon discovery of its specific action on topoisomerase I. Detailed elucidation of action mechanisms at the molecular, cellular, and pharmacologic levels has made camptothecin and its congeners perhaps the best understood among clinical anticancer drugs. Promising chemical variants of camptothecin, and recently other chemical categories of topoisomerase I-targeted drugs, provide unusually rich opportunities for rational drug selection and design. This is made possible by current concepts based, for the most part, on a sound experimental foundation, which points the way towards optimally effective therapy.
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Affiliation(s)
- K W Kohn
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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212
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Verschraegen CF, Jaeckle K, Giovanella B, Knight V, Gilbert BE. Alternative administration of camptothecin analogues. Ann N Y Acad Sci 2001; 922:237-46. [PMID: 11193899 DOI: 10.1111/j.1749-6632.2000.tb07042.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The binding of camptothecin (CPT) to the DNA-topoisomerase complex is reversible, but it needs to be maintained for maximal inhibitory activity. It is also dependent on the chemical structure of CPT. The lactone form is thought to be necessary for the activity. In human serum, the equilibrium between lactone and carboxylate is in favor of the latter. For these reasons, alternative administration of CPT analogues is being evaluated. The ideal compound would remain in lactone form and would expose the host for long periods of time to its effects. Oral administration of irinotecan (CPT-11) and topotecan (TPT) is discussed by other investigators. We studied oral rubitecan and reported a low lactone to total drug area under the plasma concentration-time curve (AUCP) ratio (14.7%), with low plasma concentration over time despite repeated administrations and the presence of an enterohepatic cycle. Aerosolization of a liposomal formulation of rubitecan is currently under study. Six patients have been treated once a day for 5 days every 3 weeks. The dose was 6.7 micrograms/kg/day. Plasma levels are dose for dose higher than those after oral administration, but the ratio of lactone versus total drug is low. No toxicity was observed. The study will continue with increasing doses and lengths of administration. Intrathecal administration of topotecan has been studied in a phase I trial in children. Doses of 0.4 mg are tolerated without toxicity, and clinical responses have been seen in patients with refractory meningial carcinomatosis. Phase II studies are planned. Intraperitoneal (i.p.) administration of topotecan has been studied in a phase I trial as a 24-hour infusion in 5% dextrose at pH 3.5 every 21 days. Dose-limiting toxicity is 4 mg/m2. Toxic effects are neutropenia, anemia, emesis, fever, and pain. Five of 10 patients with ascites had symptomatic relief. Pharmacokinetic analysis demonstrates a second-order kinetics with elimination half-lives of 0.49 and 2.7 hours. The peritoneal to plasma AUC ratio was 31.2. Intramuscular, transdermal, and subcutaneous administrations have been extensively studied in the mouse.
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Affiliation(s)
- C F Verschraegen
- Section of Gynecologic and Medical Therapeutics and Department of Neurooncology, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 401, Houston, TX 77030, USA.
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213
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Demarquay D, Huchet M, Coulomb H, Lesueur-Ginot L, Lavergne O, Kasprzyk PG, Bailly C, Camara J, Bigg DC. The homocamptothecin BN 80915 is a highly potent orally active topoisomerase I poison. Anticancer Drugs 2001; 12:9-19. [PMID: 11272292 DOI: 10.1097/00001813-200101000-00003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BN 80915, a lead compound of the homocamptothecin (hCPT) family, has entered clinical trials. BN 80915 is a difluoro-hCPT where the six-membered alpha-hydroxylactone ring of camptothecin (CPT) is replaced by a seven-membered beta-hydroxylactone ring. Preclinical data reported here show that in spite of the modification to the crucial E-ring of CPTs, BN 80915 retains topoisomerase I poisoning activity as shown in living HT29 cells as well as in cell-free assays, where BN 80915 always performs better than SN-38 or TPT. In antiproliferative assays BN 80915 is also very potent as evidenced by IC50s values consistently lower than those of SN38 in sensitive cell lines as well as in their related multidrug-resistant lines overexpressing P-glycoprotein or multidrug resistance-associated protein. Furthermore, in human plasma, in contrast to CPT analogs, the hydrolysis of BN 80915 is slow, leading to improved plasma stability, and irreversible, thus avoiding toxicity related to the accumulation of active principle during excretion in the urinary tract. These findings may account for the good in vivo efficacy observed in PC3 xenograft experiments where BN 80915 administered orally at very low doses doubled the tumor growth delay in comparison to CPT-11 administered i.p. Altogether, these results strongly support further development of BN 80915.
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214
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Bom D, Curran DP, Kruszewski S, Zimmer SG, Thompson Strode J, Kohlhagen G, Du W, Chavan AJ, Fraley KA, Bingcang AL, Latus LJ, Pommier Y, Burke TG. The novel silatecan 7-tert-butyldimethylsilyl-10-hydroxycamptothecin displays high lipophilicity, improved human blood stability, and potent anticancer activity. J Med Chem 2000; 43:3970-80. [PMID: 11052802 DOI: 10.1021/jm000144o] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We describe the rational design and synthesis of B- and A, B-ring-modified camptothecins. The key alpha-hydroxy-delta-lactone pharmacophore in 7-tert-butyldimethylsilyl-10-hydroxycamptothecin (DB-67, 14) displays superior stability in human blood when compared with clinically relevant camptothecin analogues. In human blood 14 displayed a t(1/2) of 130 min and a percent lactone at equilibrium value of 30%. The tert-butyldimethylsilyl group renders the new agent 25-times more lipophilic than camptothecin, and 14 is readily incorporated, as its active lactone form, into cellular and liposomal bilayers. In addition, the dual 7-alkylsilyl and 10-hydroxy substitution in 14 enhances drug stability in the presence of human serum albumin. Thus, the net lipophilicity and the altered human serum albumin interactions together function to promote the enhanced blood stability. In vitro cytotoxicity assays using multiple different cell lines derived from eight distinct tumor types indicate that 14 is of comparable potency to camptothecin and 10-hydroxycamptothecin, as well as the FDA-approved camptothecin analogues topotecan and CPT-11. In addition, cell-free cleavage assays reveal that 14 is highly active and forms more stable top1 cleavage complexes than camptothecin or SN-38. The impressive blood stability and cytotoxicity profiles for 14 strongly suggest that it is an excellent candidate for additional in vivo pharmacological and efficacy studies.
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Affiliation(s)
- D Bom
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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215
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Dutcher JP, Novik Y, O'Boyle K, Marcoullis G, Secco C, Wiernik PH. 20th‐Century Advances in Drug Therapy in Oncology—Part II. J Clin Pharmacol 2000. [DOI: 10.1177/009127000004001002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Janice P. Dutcher
- Our Lady of Mercy Cancer Center, New York Medical College, Bronx, New York
| | - Yelena Novik
- Our Lady of Mercy Cancer Center, New York Medical College, Bronx, New York
| | - Kevin O'Boyle
- Our Lady of Mercy Cancer Center, New York Medical College, Bronx, New York
| | - George Marcoullis
- Our Lady of Mercy Cancer Center, New York Medical College, Bronx, New York
| | - Christiane Secco
- Our Lady of Mercy Cancer Center, New York Medical College, Bronx, New York
| | - Peter H. Wiernik
- Our Lady of Mercy Cancer Center, New York Medical College, Bronx, New York
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216
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Rodriguez-Galindo C, Radomski K, Stewart CF, Furman W, Santana VM, Houghton PJ. Clinical use of topoisomerase I inhibitors in anticancer treatment. MEDICAL AND PEDIATRIC ONCOLOGY 2000; 35:385-402. [PMID: 11025469 DOI: 10.1002/1096-911x(20001001)35:4<385::aid-mpo1>3.0.co;2-e] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The camptothecin analogs topotecan and irinotecan have shown to be among the most effective anticancer agents and, as S-phase specific agents, their antitumor effect is maximized when they are administered in protracted schedules. The documented activity as single agents in many adult and pediatric malignancies has been followed by their use in combination with other anticancer agents. These studies have shown promising results, and have placed topotecan and irinotecan in the first line treatment for some malignancies. However, studies to better determine the optimal schedules and sequence of combinations are needed.
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Affiliation(s)
- C Rodriguez-Galindo
- Department of Hematology-Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA.
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217
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Zhao H, Lee C, Sai P, Choe YH, Boro M, Pendri A, Guan S, Greenwald RB. 20-O-acylcamptothecin derivatives: evidence for lactone stabilization. J Org Chem 2000; 65:4601-6. [PMID: 10959865 DOI: 10.1021/jo000221n] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Convincing UV and NMR spectrophotometric evidence is presented which demonstrates that at physiological pH, 7.4, 20-O-acyl derivatives of camptothecin (CPT) are substantially more stable in the lactone form than the 20-OH parent. Additionally, it was determined by HPLC analysis that the lactone ring of a 20-O-ether derivative of CPT underwent endocyclic ring opening at pH > or =8.5, while the lactone ring of 20-O-acyl CPT derivatives remained unaffected. PEG (and other smaller alkyl) 20-O-acyl-CPT derivatives released native CPT at pH > 9.5, which arises from exocyclic cleavage, thus precluding isolation of any open CPT acyl PEG (or alkyl) carboxylate forms.
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Affiliation(s)
- H Zhao
- Enzon, Inc., Piscataway, New Jersey 08854-3969, USA
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218
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Loos WJ, Kehrer D, Brouwer E, Verweij J, de Bruijn P, Hamilton M, Gill S, Nooter K, Stoter G, Sparreboom A. Liposomal lurtotecan (NX211): determination of total drug levels in human plasma and urine by reversed-phase high-performance liquid chromatography. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2000; 738:155-63. [PMID: 10778937 DOI: 10.1016/s0378-4347(99)00513-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Lurtotecan (GI147211; LRT) is a semisynthetic and water-soluble analogue of the topoisomerase I inhibitor camptothecin. To determine whether the therapeutic efficacy of LRT in patients could be improved, the drug was encapsulated in liposomes (NX211; Gilead Sciences). In order to allow accurate description of the pharmacokinetic behavior of NX211 in cancer patients, we have developed sensitive RP-HPLC assays with fluorescence detection (lambdaex=378 nm; lambdaem=420 nm) for the determination of total LRT levels in human plasma and urine. Sample pretreatment involved deproteinization with 10% (w/v) aqueous perchloric acid-acetonitrile (2:1, v/v), and chromatographic separations were achieved on an Inertsil-ODS 80A analytical column. The lower limit of quantitation (LLQ) was established at 1.00 ng/ml in plasma (200-microl sample) and at 100 ng/ml in urine (200 microl of 40-fold diluted sample). The within-run and between-run precisions were <7.5%. LRT concentrations in urine of <100 ng/ml were determined by a modified procedure comprising a single solvent extraction with n-butanol-diethyl ether (3:4, v/v). In this assay, the fluorescence signal of LRT was increased 14-fold prior to detection by post-column exposure to UV light (254 nm) in a photochemical reaction unit. The LLQ of this assay was 0.500 ng/ml (150-microl sample) and the within-run and between-run precisions were <10%.
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Affiliation(s)
- W J Loos
- Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek), The Netherlands.
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219
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Subrahmanyam D, Sarma VM, Venkateswarlu A, Sastry TV, Kulakarni AP, Rao DS, Reddy KV. In vitro cytotoxicity of 5-aminosubstituted 20(S)-camptothecins. Part 1. Bioorg Med Chem 1999; 7:2013-20. [PMID: 10530950 DOI: 10.1016/s0968-0896(99)00130-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A number of 5-aminosubstituted 20(S)-camptothecin analogues were prepared via semi-synthesis starting from 20(S)-camptothecin and 9-methoxy 20(S)-camptothecin. In vitro anti-cancer activity of these analogues was determined using 60 human tumor cell line assay. Although water solubility of most of these compounds was improved compared to 20(S)-camptothecin, their anti-cancer activity was considerably diminished. However, only smaller substituents such as methylamine or hydroxylamine as present in 8s and 8t, respectively, showed good activity with improved water solubility.
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Affiliation(s)
- D Subrahmanyam
- Natural Products Division, Dr Reddy's Research Foundation, Miyapur, Hyderabad, AP, India
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220
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Herben VM, Rosing H, ten Bokkel Huinink WW, van Zomeren DM, Batchelor D, Doyle E, Beusenberg FD, Beijnen JH, Schellens JH. Oral topotecan: bioavailablity and effect of food co-administration. Br J Cancer 1999; 80:1380-6. [PMID: 10424739 PMCID: PMC2363072 DOI: 10.1038/sj.bjc.6690532] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The aims of the study were twofold: (1) to evaluate the effect of food on the relative oral bioavailability of topotecan gelatin capsules in patients with solid tumours, and (2) to determine the absolute bioavailability of oral topotecan with reference to the intravenous (i.v.) formulation. The study had a randomized two-period cross-over design. On day 1 of the first treatment course patients were administered 2.3 mg m(-2) day(-1) of oral topotecan with or without a high-fat breakfast. They crossed over to receive the alternate regimen on day 2. In the second course (3 weeks later) fasted patients received topotecan orally (2.3 mg m(-2) day(-1)) or i.v. (1.5 mg m(-3) day). They crossed over to receive the alternate regimen on day 2. On days 3-5 of both treatment courses patients received oral topotecan. Plasma pharmacokinetics were performed on days 1 and 2 of the first and second course using a high-performance liquid chromatographic assay. Eighteen patients were enrolled in the study. The ratio of the area under the curve to infinity during fasted and high-fat treatment was 0.93+/-0.23 (90% confidence interval (CI) 0.83-1.03). Maximal plasma concentrations of topotecan were similar after ingestion of the capsules with (10.6+/-4.4 ng ml(-1)) or without food (9.2+/-4.1 ng ml(-1)) (P = 0.130). The time needed to reach maximal plasma levels was significantly prolonged after food intake (median 3.1 h, range 2.8-6.1) compared to fasted conditions (2.0 h, range 1.1-8.1) (P = 0.013). The absolute bioavailability of topotecan averaged 42+/-13% (90% CI 37-47%). The apparent terminal half-life was significantly longer after administration of oral topotecan (3.9+/-1.0 h) than after i.v. administration (2.7+/-0.4 h) (P < 0.001). Topotecan demonstrates suitable bioavailability for oral treatment. Co-administration of the topotecan gelatin capsules with a high-fat breakfast leads to a small decrease in absorption rate but does not affect the extent of absorption.
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Affiliation(s)
- V M Herben
- Slotervaart Hospital/The Netherlands Cancer Institute, Department of Pharmacy and Pharmacology, Amsterdam
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221
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Subrahmanyam D, Venkateswarlu A, Venkateswara Rao K, Sastry TV, Vandana G, Kumar SA. Novel C-ring analogues of 20(S)-camptothecin-part-2: synthesis and in vitro cytotoxicity of 5-C-substituted 20(S)-camptothecin analogues. Bioorg Med Chem Lett 1999; 9:1633-8. [PMID: 10397491 DOI: 10.1016/s0960-894x(99)00268-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A series of 5-C-substituted 20(S)-camptothecin analogues were synthesised and evaluated their in vitro anti-cancer activity. Several of these analogues have showed excellent activity against human tumor cell lines.
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Affiliation(s)
- D Subrahmanyam
- Natural Products Division, Dr. Reddy's Research Foundation, Miyapur, Hyderabad, India
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222
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Rosing H, van Zomeren DM, Doyle E, ten Bokkel WW, Schellens JH, Bult A, Beijnen JH. Quantification of topotecan and its metabolite N-desmethyltopotecan in human plasma, urine and faeces by high-performance liquid chromatographic methods. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1999; 727:191-203. [PMID: 10360438 DOI: 10.1016/s0378-4347(99)00078-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Sensitive high-performance liquid chromatographic (HPLC) methods have been developed and validated for the simultaneous determination of the antitumor drug topotecan and its metabolite N-desmethyltopotecan in human plasma, urine and faeces. Both compounds are reversibly hydrolysed to their hydroxycarboxylate forms at physiologic pH. Separate HPLC systems have been developed for the determination of lactone and total (lactone plus hydroxycarboxylate forms) concentrations in plasma. The instability of the analytes in plasma requires immediate protein precipitation with ice-cold methanol. The lactone forms of the analytes were stable in the methanol extracts for at least 15 months when stored at -70 degrees C. For the determination of the total levels, the plasma extracts were acidified with 25 mM phosphoric acid to convert the compounds into their lactone forms quantitatively. The sample pretreatment procedure for urine included dilution in methanol while the faecal samples were homogenized in distilled water and then extracted twice with an acetonitrile-ammonium acetate mixture. Separation was achieved on reversed-phase columns (Zorbax SB-C18) and detection was performed fluorimetrically at 380/527 nm. Within-run and between-run precisions were less than 10% and average accuracies were between 90 and 110%. The methods were used in a mass balance study in patients with malignant solid tumors to determine the disposition and routes of elimination of topotecan and N-desmethyltopotecan.
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Affiliation(s)
- H Rosing
- Department of Pharmacy and Pharmacology, Slotervaart Hospital/The Netherlands Cancer Institute, Amsterdam.
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223
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Wang X, Zhou X, Hecht SM. Role of the 20-hydroxyl group in camptothecin binding by the topoisomerase I-DNA binary complex. Biochemistry 1999; 38:4374-81. [PMID: 10194356 DOI: 10.1021/bi982708k] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent findings concerning the structure of the covalent binary complex formed by DNA topisomerase I and its DNA substrate, as well as the nature of interactions with inhibitors that bind reversibly to this binary complex, have led to two proposed models for the binding of the prototype inhibitor camptothecin to the DNA-topisomerase I binary complex. While these models differ in many regards, they both suggest the involvement of the 20-OH group of camptothecin in a donor hydrogen bond with an enzyme side chain functional group. Presently, five analogues of camptothecin that differ only at C-20 have been evaluated for their ability to bind to the topoisomerase I-DNA binary complex and thereby inhibit enzyme function. Both 20-chloro- and 20-bromocamptothecin bound as well to the enzyme-DNA binary complex as 20-aminoCPT despite the absence of a substituent at C-20 capable of contributing a donor hydrogen bond.
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Affiliation(s)
- X Wang
- Department of Chemistry, University of Virginia, Charlottesville 22901, USA
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224
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Shenderova A, Burke TG, Schwendeman SP. The acidic microclimate in poly(lactide-co-glycolide) microspheres stabilizes camptothecins. Pharm Res 1999; 16:241-8. [PMID: 10100309 DOI: 10.1023/a:1018876308346] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE The camptothecin (CPT) analogue, 10-hydroxycamptothecin (10-HCPT) has been shown previously to remain in its acid-stable (and active) lactone form when encapsulated in poly(lactide-co-glycolide) (PLGA) microspheres (1). The purpose of this study was to determine the principal mechanism(s) of 10-HCPT stabilization. METHODS CPTs were encapsulated in PLGA 50:50 microspheres by standard solvent evaporation techniques. Microspheres were eroded in pH 7.4 buffer at 37 degrees C. The ratio of encapsulated lactone to carboxylate was determined by HPLC as a function of time, initial form of drug encapsulated, fraction of co-encapsulated Mg(OH)2, CPT lipophilicity, and drug loading. Two techniques were developed to assess the microclimate pH, including: i) measurement of H+ content of the dissolved microspheres in an 80:20 acetonitrile/H2O mixture and ii) confocal microscopy of an encapsulated pH-sensitive dye, fluorescein. RESULTS The encapsulated carboxylate converted rapidly to the lactone after exposure to the release media, indicating the lactone is favored at equilibrium in the microspheres. Upon co-encapsulation of Mg(OH)2, the trend was reversed, i.e., the lactone rapidly converted to the carboxylate form. Measurement of -log(hydronium ion activity) (paH*) of dissolved microspheres with pH-electrode and pH mapping with fluorescein revealed the presence of an acidic microclimate. From the measurements of H+ and water contents of particles hydrated for 3 days, a microclimate pH was estimated to be in the neighborhood of 1.8. The co-encapsulation of Mg(OH)2 could both increase the paH* reading and neutralize pH in various regions of the microsphere interior. Varying the drug lipophilicity and loading revealed that the precipitation of the lactone could also stabilize CPT. CONCLUSIONS PLGA microspheres prepared by the standard solvent evaporation techniques develop an acidic microclimate that stabilizes the lactone form of CPTs. This microclimate may be neutralized by co-encapsulating a base such as Mg(OH)2, as suggested by previous work with poly(ortho esters) (2).
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Affiliation(s)
- A Shenderova
- Division of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, Ohio State University, Columbus 43210, USA
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225
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Lavergne O, Lesueur-Ginot L, Pla Rodas F, Kasprzyk PG, Pommier J, Demarquay D, Prévost G, Ulibarri G, Rolland A, Schiano-Liberatore AM, Harnett J, Pons D, Camara J, Bigg DC. Homocamptothecins: synthesis and antitumor activity of novel E-ring-modified camptothecin analogues. J Med Chem 1998; 41:5410-9. [PMID: 9876111 DOI: 10.1021/jm980400l] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Homocamptothecin (hCPT), a camptothecin (CPT) analogue with a seven membered beta-hydroxylactone which combines enhanced plasma stability and potent topoisomerase I (Topo I)-mediated activity, is an attractive template for the elaboration of new anticancer agents. Like CPT, hCPT carries an asymmetric tertiary alcohol and displays stereoselective inhibition of Topo I. The preparation and biological screening of racemic hCPT analogues are described. The 10 hCPTs tested were better Topo I inhibitors than CPT. Fluorinated hCPTs 23c, d,f,g were found to have potent cytotoxic activity on A427 and PC-3 tumor cell lines. Their cytotoxicity remained high on the K562adr and MCF7mdr cell lines, which overexpress a functionally active P-glycoprotein. Fluorinated hCPTs were more efficacious in vivo than CPT on HT-29 xenografts. In this model, a tumor growth delay of 25 days was reached with hCPT 23g at a daily dose of 0.32 mg/kg, compared to 4 days with CPT at 0.625 mg/kg. Thus difluorinated hCPT 23g warrants further investigation as a novel Topo I inhibitor with high cytotoxicity toward tumor cells and promising in vivo efficacy.
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Affiliation(s)
- O Lavergne
- Institut Henri Beaufour, 5, avenue du Canada, F-91966 Les Ulis, France
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226
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Wang X, Short GF, Kingsbury WD, Johnson RK, Hecht SM. Effects of camptothecin analogues on DNA transformations mediated by calf thymus and human DNA topoisomerases I. Chem Res Toxicol 1998; 11:1352-60. [PMID: 9815197 DOI: 10.1021/tx9801110] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Camptothecin (CPT) and 10 structural analogues were studied to characterize their effects on specific rearrangements of DNA structure mediated by human and calf thymus DNA topoisomerases I. A 30 base pair DNA duplex containing a single high-efficiency topoisomerase cleavage site was incubated with each of the enzymes in the presence of the inhibitors. Individual inhibitors stabilized the covalent enzyme-DNA binary complex to different extents, as anticipated. However, for several of the inhibitors, the extent of ternary complex formation differed substantially for the human and calf thymus enzymes. In common with calf thymus topoisomerase I, the human enzyme was shown to mediate the rearrangement of branched, nicked, and gapped DNA substrates that constitute models for illegitimate recombination. However, some of these rearrangements proceeded with different rates and efficiencies in the presence of human topoisomerase I. When inhibition of three of the rearrangements by CPT analogues was studied, most of the analogues exhibited differential effects on a given transformation, depending on the source of the enzyme employed.
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Affiliation(s)
- X Wang
- Departments of Chemistry and Biology, University of Virginia, Charlottesville, Virginia 22901, USA
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227
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Takimoto CH, Wright J, Arbuck SG. Clinical applications of the camptothecins. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1400:107-19. [PMID: 9748525 DOI: 10.1016/s0167-4781(98)00130-4] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The camptothecin topoisomerase I-targeting agents are new class of antitumor drugs with demonstrated clinical activity in human malignancies, such as colorectal cancer and ovarian cancer. Currently, irinotecan and topotecan are the most widely used camptothecin analogs in clinical use and clinical trials are ongoing to better characterize their spectra of clinical activity, to determine their optimal schedules of administration and to define their use in combination with other chemotherapeutic agents. Newer camptothecin analogs in clinical development, such as 9-aminocamptothecin, 9-nitrocamptothecin, GI147211 and DX-8951f, are also being studied to determine if they have improved toxicity and efficacy profiles compared with existing analogs. Other potential clinical applications include the use of camptothecin derivatives as radiation sensitizers or as antiviral agents. The successful development of the camptothecins as antitumor agents highlights the importance of topoisomerase I as a target for cancer chemotherapy.
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Affiliation(s)
- C H Takimoto
- Developmental Therapeutics Department, Medicine Branch, Division of Clinical Sciences, National Cancer Institute, Building 8, Room 5101, Bethesda Naval Hospital, Bethesda, MD 20892, USA.
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228
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Abstract
Camptothecins (CPTs) are a unique class of chemotherapeutic agent which inhibit DNA synthesis by inhibiting topoisomerase I activity. Structure-activity studies on the original CPT alkaloid led to the development of the new analogues irinotecan (CPT-11), topotecan, and 9-aminocamptothecin, which have improved water solubility and lower toxicity. CPT analogues exhibit interesting pharmacokinetic/pharmacodynamic and metabolic properties that are of major research and clinical interest. This review describes the clinical pharmacology of these 3 CPT analogues. Specific areas such as absorption after extravascular administration, pharmacokinetic/pharmacodynamic variability, metabolism, and administration in special populations are discussed.
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Affiliation(s)
- L Iyer
- Committee on Clinical Pharmacology, University of Chicago, IL 60637, USA
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229
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Sugiyama Y, Kato Y, Chu X. Multiplicity of biliary excretion mechanisms for the camptothecin derivative irinotecan (CPT-11), its metabolite SN-38, and its glucuronide: role of canalicular multispecific organic anion transporter and P-glycoprotein. Cancer Chemother Pharmacol 1998; 42 Suppl:S44-9. [PMID: 9750028 DOI: 10.1007/s002800051078] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
A frequent dose-limiting effect of irinotecan (CPT-11) is its gastrointestinal toxicity (diarrhea), which is thought to be related to biliary excretion of CPT-11 and its metabolites. Accordingly, we have investigated the mechanism of biliary excretion of these compounds. In vivo pharmacokinetic studies revealed that the biliary excretion of the four anionic forms of CPT-11 and its metabolites was reduced in Eisai hyperbilirubinemic rats, which carry a mutation of the hepatic canalicular multispecific organic anion transporter (cMOAT) gene. The protein encoded by this gene is expressed on the bile canalicular membrane and is responsible for the transport of organic anions into bile. Detailed analysis using isolated liver bile canalicular membrane vesicles to identify transport systems showed that cMOAT is responsible for biliary excretion of the low-affinity component of the carboxylate form of CPT-11 and the high-affinity component of both the lactone and carboxylate forms of SN-38 glucuronide. The carboxylate form of SN-38 is transported by cMOAT alone. Transport of the high-affinity component of CPT-11 was inhibited by verapamil and PSC-833, but their effect on the transport of its low-affinity component was minimal. In addition, ATP dependence in the uptake of CPT-11 by membrane vesicles obtained from a P-glycoprotein (P-gp)-overexpressing cell line was observed. Thus P-gp may be responsible for transport of the high-affinity component of the carboxylate form of CPT-11.
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Affiliation(s)
- Y Sugiyama
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Japan
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230
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Wang X, Wang LK, Kingsbury WD, Johnson RK, Hecht SM. Differential effects of camptothecin derivatives on topoisomerase I-mediated DNA structure modification. Biochemistry 1998; 37:9399-408. [PMID: 9649322 DOI: 10.1021/bi980451k] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The effects of eleven camptothecin derivatives on calf thymus topoisomerase I-mediated cleavage of synthetic DNA duplex have revealed that the A ring of camptothecin is very important for its biochemical activity. Depending on the type, number, and location of substituents, highly active or inactive analogues were obtained. The persistence of CPT-induced topoisomerase I-DNA covalent binary complexes was investigated by using as substrates DNA containing several good topoisomerase I cleavage sites, or else a synthetic DNA duplex of defined structure with a single high-efficiency cleavage site. The ligation kinetics at a given topoisomerase I cleavage site were sometimes quite different in the presence of CPT derivatives whose structures were closely related. Even in the presence of a single CPT analogue, topoisomerase I-DNA covalent binary complexes underwent ligation with different kinetics, presumably reflecting a dependence on DNA sequences flanking the individual topoisomerase I cleavage sites. Individual camptothecin derivatives also exhibited a spectrum of inhibitory potentials in blocking the topoisomerase I-mediated rearrangement of branched, nicked, and gapped DNA duplex substrates; in some cases the potencies of inhibition observed in these assays for individual camptothecin analogues were quite different than those determined for stabilization of the unmodified DNA-topoisomerase I binary complex.
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Affiliation(s)
- X Wang
- Department of Chemistry, University of Virginia, Charlottesville 22901, USA
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231
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Fan Y, Weinstein JN, Kohn KW, Shi LM, Pommier Y. Molecular modeling studies of the DNA-topoisomerase I ternary cleavable complex with camptothecin. J Med Chem 1998; 41:2216-26. [PMID: 9632354 DOI: 10.1021/jm9605445] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The present studies provide a three-dimensional model for the postulated ternary cleavable complex of topoisomerase I (top1), DNA, and camptothecin (CPT). Molecular simulations were done using the AMBER force field. The results suggest that a ternary cleavable complex might be stabilized by several hydrogen bonds in the binding site. In this proposed "drug-stacking" model, CPT is pseudointercalated in the top1-linked DNA cleavage site and interacts with the protein near its catalytic tyrosine through hydrogen bonding and stacking. The structural model is consistent with the following experimental observations: (i) the N3 position of the 5' terminal purine of the cleaved DNA strand is readily alkylated by 7-chloromethyl 10,11-methylenedioxy CPT; (ii) CPT generally tolerates substituents at positions 7, 9, and 10 but is inactivated by additions at position 12; (iii) 10,11-methylenedioxy (MDO) CPT is much more potent than 10,11-dimethoxy (DMO) CPT; (iv) the lactone portion of CPT is essential for top1 inhibitory activity; (v) 20S derivatives of CPT are much more potent than the 20R analogues; (vi) a catalytic tyrosine hydroxyl in top1 covalently links to the 3' terminal base, T, of the cleaved DNA strand; and (vii) top1 mutation Asn722Ser leads to CPT resistance. A total of 18 camptothecin derivatives with different DNA cleavage potencies were docked into the hypothetical cleavable complex binding site to test and refine the model. These studies provide insight into a possible mechanism of top1 inhibition by CPT derivatives and suggest rational approaches for the design of new CPT derivatives.
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Affiliation(s)
- Y Fan
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, Building 37, Room 5D02, National Institutes of Health, Bethesda, Maryland 20892-4255, USA
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232
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Affiliation(s)
- S M Blaney
- Department of Pediatrics, Texas Children's Cancer Center, Baylor College of Medicine, Houston 77030, USA
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233
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Ahmed F, Vyas V, Saleem A, Li XG, Zamek R, Cornfield A, Haluska P, Ibrahim N, Rubin EH, Gupta E. High-performance liquid chromatographic quantitation of total and lactone 20(S)camptothecin in patients receiving oral 20(S)camptothecin. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1998; 707:227-33. [PMID: 9613954 DOI: 10.1016/s0378-4347(97)00615-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have developed a sensitive high-performance liquid chromatography (HPLC) assay to quantitate total and lactone forms of 20(S)camptothecin (CPT) in human plasma. Lactone and total CPT were extracted using solid-phase extraction and liquid-liquid extraction, respectively. The extracted lactone samples could be stored without immediate HPLC analysis. The two forms of CPT were quantitated by reversed-phase HPLC with fluorescence detection. The extraction efficiencies were about 100% and 92% for the total and lactone forms, respectively. The lower limit of quantitation was 5.74 nM for the two forms. The method was reproducible with a mean interday and intraday variability of 6% for total CPT and 4% and 6%. respectively, for lactone CPT. The assay could effectively quantitate lactone and total CPT in patients receiving single dose and multiple doses of oral CPT.
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Affiliation(s)
- F Ahmed
- UMDNJ--The Cancer Institute of New Jersey, New Brunswick 08901, USA
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234
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Yang D, Strode JT, Spielmann HP, Wang AHJ, Burke TG. DNA Interactions of Two Clinical Camptothecin Drugs Stabilize Their Active Lactone Forms. J Am Chem Soc 1998. [DOI: 10.1021/ja973433j] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Danzhou Yang
- Division of Medicinal Chemistry and Pharmaceutics College of Pharmacy Department of Biochemistry, College of Medicine Department of Chemistry, College of Arts and Sciences Markey Cancer Center, University of Kentucky Lexington, Kentucky 40506 Department of Cell & Structural Biology University of Illinois at Urbana−Champaign Urbana, Illinois 61801
| | - J. Thompson Strode
- Division of Medicinal Chemistry and Pharmaceutics College of Pharmacy Department of Biochemistry, College of Medicine Department of Chemistry, College of Arts and Sciences Markey Cancer Center, University of Kentucky Lexington, Kentucky 40506 Department of Cell & Structural Biology University of Illinois at Urbana−Champaign Urbana, Illinois 61801
| | - H. Peter Spielmann
- Division of Medicinal Chemistry and Pharmaceutics College of Pharmacy Department of Biochemistry, College of Medicine Department of Chemistry, College of Arts and Sciences Markey Cancer Center, University of Kentucky Lexington, Kentucky 40506 Department of Cell & Structural Biology University of Illinois at Urbana−Champaign Urbana, Illinois 61801
| | - Andrew H.-J. Wang
- Division of Medicinal Chemistry and Pharmaceutics College of Pharmacy Department of Biochemistry, College of Medicine Department of Chemistry, College of Arts and Sciences Markey Cancer Center, University of Kentucky Lexington, Kentucky 40506 Department of Cell & Structural Biology University of Illinois at Urbana−Champaign Urbana, Illinois 61801
| | - Thomas G. Burke
- Division of Medicinal Chemistry and Pharmaceutics College of Pharmacy Department of Biochemistry, College of Medicine Department of Chemistry, College of Arts and Sciences Markey Cancer Center, University of Kentucky Lexington, Kentucky 40506 Department of Cell & Structural Biology University of Illinois at Urbana−Champaign Urbana, Illinois 61801
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235
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Redinbo MR, Stewart L, Kuhn P, Champoux JJ, Hol WG. Crystal structures of human topoisomerase I in covalent and noncovalent complexes with DNA. Science 1998; 279:1504-13. [PMID: 9488644 DOI: 10.1126/science.279.5356.1504] [Citation(s) in RCA: 629] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Topoisomerases I promote the relaxation of DNA superhelical tension by introducing a transient single-stranded break in duplex DNA and are vital for the processes of replication, transcription, and recombination. The crystal structures at 2.1 and 2.5 angstrom resolution of reconstituted human topoisomerase I comprising the core and carboxyl-terminal domains in covalent and noncovalent complexes with 22-base pair DNA duplexes reveal an enzyme that "clamps" around essentially B-form DNA. The core domain and the first eight residues of the carboxyl-terminal domain of the enzyme, including the active-site nucleophile tyrosine-723, share significant structural similarity with the bacteriophage family of DNA integrases. A binding mode for the anticancer drug camptothecin is proposed on the basis of chemical and biochemical information combined with these three-dimensional structures of topoisomerase I-DNA complexes.
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Affiliation(s)
- M R Redinbo
- Biomolecular Structure Center and Department of Biological Structure, Box 357742, School of Medicine, University of Washington, Seattle, WA 98195, USA
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236
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Chourpa I, Millot JM, Sockalingum GD, Riou JF, Manfait M. Kinetics of lactone hydrolysis in antitumor drugs of camptothecin series as studied by fluorescence spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1379:353-66. [PMID: 9545598 DOI: 10.1016/s0304-4165(97)00115-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Potent antitumor activity exhibited by 20-S-camptothecin (CPT) and numerous derivatives is known to be lost upon opening of the alpha-hydroxy-lactone ring of these drugs, hydrolyzable at neutral and basic pH. To quantify in 'real time' the lactone hydrolysis reaction in CPTs under physiological conditions, we have applied a non-perturbing approach by fluorescence spectroscopy. CPT and a set of its derivatives (21-lactam-S-CPT, 10,11-(methylenedioxy)-CPT, CPT-11, SN-38, topotecan, tricyclic ketone-CPT) with antitumor activity varying from negligible to 10 times that of CPT have been studied. Prior to the kinetic measurements, the effects of substitutions, pH, polarity of molecular environment, lactone ring opening (lactone-carboxylate transition) have been investigated in terms of the UV-visible absorption and fluorescence emission spectra of CPTs. Then the determined parameters of the fluorescence emission spectra corresponding to the respective lactone and carboxylate forms have been used to estimate the residual lactone percentage as a function of time. The reproducibility of the obtained data demonstrates that the spectroscopic approach provides a satisfactory precision for this kind of measurements. For CPT at pH 7.3, the lactone half-life was 29.4 +/- 1.7 min and the lactone percentage at equilibrium was 20.9 +/- 0.3%. Within a series of derivatives with substitutions at quinoline rings, the lactone half-life varied from 29 to 32 min and the equilibrium lactone content varied from 15% to 23%. For each compound, even slight increase of pH from 7.1 to 7.3 or from 7.3 to 7.6 logically leads to a remarkable decrease of both lactone half-life and equilibrium lactone percentage.
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Affiliation(s)
- I Chourpa
- Laboratoire de Spectroscopie Biomoléculaire, IFR 53, UFR de Pharmacie, Université de Reims Champagne-Ardenne, France
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Rowinsky EK, Baker SD, Burks K, O'Reilly S, Donehower RC, Grochow LB. High-dose topotecan with granulocyte-colony stimulating factor in fluoropyrimidine-refractory colorectal cancer: a phase II and pharmacodynamic study. Ann Oncol 1998; 9:173-80. [PMID: 9553662 DOI: 10.1023/a:1008266630701] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
PURPOSE The premise for this study was that topotecan (TPT) resistance in preclinical studies is associated with low level expression of the p-glycoprotein (Pgp) multi-drug transporter conferred by the multi-drug resistant (MDR) phenotype, which might be overcome in clinical practice by administering moderately (2.3-fold) higher doses of TPT that have shown to be feasible with granulocyte colony-stimulating factor (G-CSF) support. This phase II study evaluated the anti-tumor activity of TPT administered at its highest possible solid tumor dose with G-SCF in patients with fluoropyrimidine-refractory advanced colorectal carcinoma. The study also sought to identify pharmacodynamic (PD) determinants of both activity and toxicity. PATIENTS AND METHODS TPT was administered as a 30-minute infusion daily for five days every three weeks at a dose of 3.5 mg/m2/day to patients with advance colorectal carcinoma who developed progressive disease either during treatment with fluoropyrimidine-based chemotherapy for advanced disease or within six months after receiving fluoropyrimidine-based adjuvant chemotherapy. This dose of TPT was previously determined to be the maximal tolerated dose (MTD) with G-CSF support in a phase I study involving solid tumor patients with similar risk factors for myelosuppression. Plasma sampling with performed during course 1 to characterize the pharmacokinetic (PK) and PD behavior of TPT. RESULTS Seventeen patients who received 89 courses of TPT and G-CSF were evaluable for toxicity; 16 patients were evaluable for anti-tumor response. Toxicity, particularly myelosuppression, was substantial. At the 3.5 mg/m2/day dose level, absolute neutrophil counts (ANC) were less than 500/microliters for longer than 5 days in 17% of courses involving seven of seventeen (41%) patients. Severe neutropenia associated with fever occurred in 12.3% of courses; and platelet counts below 25,000/microliters were noted in 26.9% of courses. These toxicities resulted in dose reductions in seven of 17 (41%) patients. Nevertheless, 90% of the planned total dose of TPT was administered. No major responses were observed, though minor activity was noted in several patients. Both the median time to progression and the median survival time were short--2.5 and 4 months respectively. Although interindividual variability in the disposition of total TPT was observed, the lack of objective responses precluded PD assessments related to disease activity. Total TPT exposure was significantly higher than drug exposure achieved in similar patients at an identical dose in a previous phase I study of TPT and G-CSF, which may explain why more severe myelosuppressive effects occurred in the present study. There were no PD relationships evident between relevant PK parameters and the percent decrements in platelets and ANC's during course 1, although patients with severe toxic effects (ANC below 500/microliters for more than five days and/or platelets < 25,000/microliters) had higher drug exposure than patients with less severe toxicity (P < 0.018 and P = 0.09, respectively). CONCLUSIONS Based on these results, the true response rate of TPT at its solid tumor MTD with G-CSF support is unlikely to approach 20%. Although a response rate of less than 20% might be viewed as significant in this disease setting and might be confirmed with sufficient statistical certainty by treating additional patients, the substantial toxicity, inconvenience, and cost associated with this high dose TPT/G-CSF regimen does not warrant the acceptance of a lower level of anti-tumor activity as a criterion for further development.
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Affiliation(s)
- E K Rowinsky
- Johns Hopkins Oncology Center, Baltimore, MD, USA
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239
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Wall ME, Wani MC. Chapter 13 History and Future Prospects of Camptothecin and Taxol. THE ALKALOIDS: CHEMISTRY AND BIOLOGY 1998. [DOI: 10.1016/s1099-4831(08)60051-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Josien H, Bom D, Curran DP, Zheng YH, Chou TC. 7-Silylcamptothecins (silatecans): A new family of camptothecin antitumor agents. Bioorg Med Chem Lett 1997. [DOI: 10.1016/s0960-894x(97)10181-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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241
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Shenderova A, Burke TG, Schwendeman SP. Stabilization of 10-hydroxycamptothecin in poly(lactide-co-glycolide) microsphere delivery vehicles. Pharm Res 1997; 14:1406-14. [PMID: 9358554 DOI: 10.1023/a:1012172722246] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE The purpose of this study was to investigate the potential of poly(lactide-co-glycolide) (PLGA) microspheres to stabilize and deliver the analogue of camptothecin, 10-hydroxycamptothecin (10-HCPT). METHODS 10-HCPT was encapsulated in PLGA 50:50 microspheres by using an oil-in-water emulsion-solvent evaporation method. The influence of encapsulation conditions (i.e., polymer molecular weight (Mw), polymer concentration, and carrier solvent composition) on the release of 10-HCPT from microspheres at 37 degrees C under perfect sink conditions was examined. Analysis of the drug stability in the microspheres was performed by two methods: i) by extraction of 10-HCPT from microspheres and ii) by sampling release media before lactone--carboxylate conversion could take place. RESULTS Microspheres made of low Mw polymer (inherent viscosity 0.15 dl/g) exhibited more continuous drug release than those prepared from polymers of higher Mw (i.v. = 0.58 and 1.07 dl/g). In addition, a high polymer concentration and the presence of cosolvent in the carrier solution to dissolve 10-HCPT were both necessary in the microsphere preparation in order to eliminate a large initial burst of the released 10-HCPT. An optimal microsphere formulation released 10-HCPT slowly and continuously for over two months with a relatively small initial burst of the released drug. Both analytical methods used to assess the stability of 10-HCPT revealed that the unreleased camptothecin analogue in the microspheres remained in its active lactone form (> 95%) over the entire 2-month duration of study. CONCLUSIONS PLGA carriers such as those described here may be clinically useful to stabilize and deliver camptothecins for the treatment of cancer.
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Affiliation(s)
- A Shenderova
- Division of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, Ohio State University, Columbus 43210, USA
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Lavergne O, Lesueur-Ginot L, Rodas FP, Bigg DC. BN 80245: An E-ring modified camptothecin with potent antiproliferative and topoisomerase I inhibitory activities. Bioorg Med Chem Lett 1997. [DOI: 10.1016/s0960-894x(97)00398-3] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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O'Reilly S, Rowinsky EK. Experimental chemotherapeutic agents for the treatment of colorectal carcinoma. Hematol Oncol Clin North Am 1997; 11:721-58. [PMID: 9257153 DOI: 10.1016/s0889-8588(05)70458-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Colorectal cancer is the third leading cause of cancer mortality for men and women in the United States. For the past 40 years fluorouracil has been the only agent with significant activity in this disease. More recently, advances in our understanding of the molecular biology of cancer have permitted the development of effective new agents for this disease. This article examines the current and future status of these new agents.
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Affiliation(s)
- S O'Reilly
- Division of Medical Oncology, Johns Hopkins Oncology Center, Baltimore, Maryland, USA
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244
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Loos WJ, Sparreboom A, Verweij J, Nooter K, Stoter G, Schellens JH. Determination of the lactone and lactone plus carboxylate forms of 9-aminocamptothecin in human plasma by sensitive high-performance liquid chromatography with fluorescence detection. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1997; 694:435-41. [PMID: 9252060 DOI: 10.1016/s0378-4347(97)00117-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Two sensitive reversed-phase high-performance liquid chromatographic fluorescence methods, with simple sample handling at the site of the patient, are described for the determination of the lactone and lactone plus carboxylate forms of 9-aminocamptothecin (9AC). For 9AC lactone, the sample preparation was a liquid-liquid extraction with acetonitrile-n-butyl chloride (1:4, v/v), whereas the sample preparation for 9AC total (lactone plus carboxylate) was a simple deproteinization with 5% perchloric acid-methanol (1:1, v/v), which results in the conversion of the carboxylate into the lactone form. The lower limits of quantitation were 50 pg/ml and 100 pg/ml for 9AC lactone and 9AC total, respectively. The within-run precisions at four tested concentrations were < or = 6.3% for 9AC lactone and < or = 5.3% for 9AC total. The between-run precisions were < or = 8.9% and < or = 5.6%, respectively. The assays were developed to enable pharmacological analysis of 9AC in a bioavailability and oral phase I study in patients with solid tumors.
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Affiliation(s)
- W J Loos
- Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek) and University Hospital Rotterdam, Netherlands
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Chourpa I, Beljebbar A, Sockalingum GD, Riou JF, Manfait M. Structure-activity relation in camptothecin antitumor drugs: why a detailed molecular characterisation of their lactone and carboxylate forms by Raman and SERS spectroscopies? BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1334:349-60. [PMID: 9101731 DOI: 10.1016/s0304-4165(96)00113-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Lactone and carboxylate forms of potent antitumor agents, camptothecins (CPTs) have been studied by Raman, Fourier-transform Raman (FT-Raman) and surface-enhanced Raman scattering (SERS) spectroscopy. Similarity of the Raman spectra of CPTs with corresponding FT-Raman spectra in the near-infrared allowed the latter to be compared with their SERS counterparts in order to analyse the interaction of the drugs with silver colloids. Different types of silver colloids (reduced with sodium borohydride or sodium citrate, with or without activation by anions) have been evaluated. Citrate-reduced colloid, activated with chloride anions (CAS) has been found to be the best compromise for SERS studies of both forms of CPTs. We suggest that in general CPTs are adsorbed on CAS via the nitrogen in ring B and are more inclined to a flat orientation than to a perpendicular one. However, probable interactions of substitution groups and/or of the COO- groups of hydrolysed CPTs with the CAS surface introduce some particularities in the adsorption patterns. As a result, SERS spectra are highly sensitive to hydrolysis and substitutions at distant rings of CPT and uniquely characteristic of each of the CPT derivatives. The pronounced hydrolysis-induced changes, similar in the Raman and SERS spectra of CPTs, involve similar vibrations in the spectra of different CPTs. Vibrational assignments, proposed for the main Raman and SERS bands of CPT and its derivatives (21-lactam-S-CPT, 10,11-(methylenedioxy)-CPT, CPT-11, SN-38 and topotecan) indicate that most of the bands which decreased upon lactone hydrolysis are those preferentially related to stretching modes of the quinoline rings A and B, and the bands which increased are those of the ring D stretching modes. Our data make the spectroscopic approach very promising for the further investigations of the molecular mechanisms of biological activity of CPTs.
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Affiliation(s)
- I Chourpa
- UFR de Pharmacie, Université de Reims Champagne-Ardenne, France
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Kawato Y, Terasawa H. 2 Recent Advances in the Medicinal Chemistry and Pharmacology of Camptothecin. PROGRESS IN MEDICINAL CHEMISTRY 1997. [DOI: 10.1016/s0079-6468(08)70105-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Abstract
The extracellular pH (pHe) of solid tumours is often lower than in normal tissues, and this may influence the uptake and/or activity of anti-cancer drugs. The cytotoxicity of mitoxantrone, paclitaxel and topotecan was therefore assessed at low pHe and after manipulation of intracellular pH (pHi) in murine EMT6 and in human MGH-U1 cells. The cytotoxic efficacy of all three agents was reduced at pHe 6.5 as compared with pHe 7.4. The ionophore nigericin and inhibitors of membrane-based ion exchange mechanisms that regulate pHi (5-[N-ethyl-N-isopropyl] amiloride, EIPA; 4,4-diisothiocyanstilbene 2,2-disulphonic acid, DIDS) were used to cause intracellular acidification. Combined use of the cytostatic drugs with pHi modifiers reduced their cytotoxicity under both physiological and low-pHe conditions. The uptake into cells of mitoxantrone (a weak base) was inhibited at pHe 6.5 as compared with pHe 7.4, and smaller effects of low pHe to inhibit uptake of topotecan were also observed. DNA analysis of cell cycle distribution revealed that intracellular acidification, as observed during incubation at low pHe and/or using pHi modifiers, resulted in accumulation of cells in G1 phase, where they may be more resistant to these drugs. Reduced uptake of weak bases (mitoxantrone) at low pHe and altered cell cycle kinetics upon acidification are the postulated causes of reduced cytotoxicity of the agents investigated.
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Affiliation(s)
- V Vukovic
- Department of Medicine, Ontario Cancer Institute and University of Toronto, Canada
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Natelson EA, Giovanella BC, Verschraegen CF, Fehir KM, De Ipolyi PD, Harris N, Stehlin JS. Phase I clinical and pharmacological studies of 20-(S)-camptothecin and 20-(S)-9-nitrocamptothecin as anticancer agents. Ann N Y Acad Sci 1996; 803:224-30. [PMID: 8993516 DOI: 10.1111/j.1749-6632.1996.tb26392.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Groups of 52 and 29 patients with refractory cancers received either native camptothecin (CPT) or 9-nitrocamptothecin (9NC), respectively, in Phase I clinical trials designed to determine the maximum tolerated dose, toxicity and potential efficacy of orally administered camptothecins. Favorable responses occurred with both compounds (11% after CPT, 24% after 9NC). Although both agents could be taken safely for extended periods, dose limiting toxicities were substantial. Diarrhea was the major clinical problem with CPT, and myelosuppression with 9NC. Both compounds could cause hemorrhagic cystitis. The antitumor activity demonstrated suggests that further investigation of orally administered camptothecin analogs is warranted.
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Affiliation(s)
- E A Natelson
- Stehlin Foundation for Cancer Research, St. Joseph Hospital, Houston, Texas 77003, USA
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Burke TG. Chemistry of the camptothecins in the bloodstream. Drug stabilization and optimization of activity. Ann N Y Acad Sci 1996; 803:29-31. [PMID: 8993497 DOI: 10.1111/j.1749-6632.1996.tb26373.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- T G Burke
- Division of Pharmaceutics, College of Pharmacy, Ohio State University, Columbus 43210, USA
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Feofanov AV, Baranov AV, Fleury F, Riou JF, Nabiev IR, Manfait M. DNA topoisomerase I changes the mode of interaction between camptothecin drugs and DNA as probed by UV-resonance Raman spectroscopy. FEBS Lett 1996; 396:289-92. [PMID: 8915005 DOI: 10.1016/0014-5793(96)01118-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Pronounced differences of interactions of camptothecin (CPT) and its derivative 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT11), inhibitors of DNA topoisomerase I, with oligonucleotides were found using UV resonance Raman spectroscopy. 30-mer oligonucleotides were derived from the sequences of the topoisomerase I-induced and CPT-enhanced cleavage sites in SV40 DNA. CPT induces well-defined alterations of the oligo structure, whereas CPT11 interacts with oligonucleotides more weakly and in another manner than CPT. Formation of cleavable ternary complexes between CPT11, topoisomerase I and oligonucleotides causes CPT11 to interact with oligonucleotides in the same fashion as was found for its parent compound CPT, and enhances this interaction as compared to CPT-oligonucleotide complexes. The data present evidence of molecular interactions of CPT11 with both other partners (topoisomerase I and oligonucleotide) of the ternary cleavable complex at the oligonucleotide-enzyme interface.
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Affiliation(s)
- A V Feofanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation
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