1
|
Almeida A, Fernandes E, Sarmento B, Lúcio M. A Biophysical Insight of Camptothecin Biodistribution: Towards a Molecular Understanding of Its Pharmacokinetic Issues. Pharmaceutics 2021; 13:pharmaceutics13060869. [PMID: 34204692 PMCID: PMC8231504 DOI: 10.3390/pharmaceutics13060869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 05/27/2021] [Accepted: 06/04/2021] [Indexed: 12/02/2022] Open
Abstract
Camptothecin (CPT) is a potent anticancer drug, and its putative oral administration is envisioned although difficult due to physiological barriers that must be overcome. A comprehensive biophysical analysis of CPT interaction with biointerface models can be used to predict some pharmacokinetic issues after oral administration of this or other drugs. To that end, different models were used to mimic the phospholipid composition of normal, cancer, and blood–brain barrier endothelial cell membranes. The logD values obtained indicate that the drug is well distributed across membranes. CPT-membrane interaction studies also confirm the drug’s location at the membrane cooperative and interfacial regions. The drug can also permeate membranes at more ordered phases by altering phospholipid packing. The similar logD values obtained in membrane models mimicking cancer or normal cells imply that CPT has limited selectivity to its target. Furthermore, CPT binds strongly to serum albumin, leaving only 8.05% of free drug available to be distributed to the tissues. The strong interaction with plasma proteins, allied to the large distribution (VDSS = 5.75 ± 0.932 L·Kg−1) and tendency to bioaccumulate in off-target tissues, were predicted to be pharmacokinetic issues of CPT, implying the need to develop drug delivery systems to improve its biodistribution.
Collapse
Affiliation(s)
- Andreia Almeida
- INEB—Instituto Nacional de Engenharia Biomédica, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; (A.A.); (B.S.)
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Eduarda Fernandes
- CF-UM-UP, Centro de Física das Universidades do Minho e Porto, Departamento de Física da Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal;
| | - Bruno Sarmento
- INEB—Instituto Nacional de Engenharia Biomédica, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; (A.A.); (B.S.)
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- CESPU, Instituto de Investigação e Formação Avançada em Ciências e Tecnologias da Saúde, Rua Central da Gandra 137, 4585-116 Gandra, Portugal
| | - Marlene Lúcio
- CF-UM-UP, Centro de Física das Universidades do Minho e Porto, Departamento de Física da Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal;
- CBMA, Centro de Biologia Molecular e Ambiental, Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Correspondence:
| |
Collapse
|
2
|
Li F, Jiang T, Li Q, Ling X. Camptothecin (CPT) and its derivatives are known to target topoisomerase I (Top1) as their mechanism of action: did we miss something in CPT analogue molecular targets for treating human disease such as cancer? Am J Cancer Res 2017; 7:2350-2394. [PMID: 29312794 PMCID: PMC5752681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 11/07/2017] [Indexed: 06/07/2023] Open
Abstract
Camptothecin (CPT) was discovered from plant extracts more than 60 years ago. Since then, only two CPT analogues (irinotecan and topotecan) have been approved for cancer treatment, although several thousand CPT derivatives have been synthesized and many of them were actively studied in our research community over the past 6+ decades. In this review article, we briefly summarize: (1) the discovery and early development of CPTs, (2) the recognized CPT mechanism of action (MOA), (3) the synthesis of CPT and CPT analogues, and (4) the structure-activity relationship (SAR) of CPT and its analogues. Next, we provide evidence that certain CPT analogues can exert improved efficacy with low toxicity independently of topoisomerase I (Top1) inhibition; instead, these CPT analogues use novel MOAs by targeting important cancer survival-associated oncogenic proteins and/or by bypassing various treatment-resistant mechanisms. We then present a comprehensive review of the most advanced CPT analogues in clinical development, with the goal of resolving why no new CPTs have been FDA approved for cancer treatment, beyond irinotecan and topotecan. We argue that new CPT Top1 inhibitor drugs are unlikely being found to be significantly better than irinotecan and/or topotecan in terms of the overall antitumor activity and toxicity. The significance of CPT analogues that possess novel MOAs has not been sufficiently recognized so far. In our opinion, this is a research area with great potential to make a breakthrough for development of the next generation of CPT analogues that possess high efficacy (due to novel targets) and low toxicity (due to low inhibition of Top1 activity/function) for effective treatment of human disease, including cancer.
Collapse
Affiliation(s)
- Fengzhi Li
- Department of Pharmacology & Therapeutics, Roswell Park Cancer InstituteBuffalo, New York, USA
| | - Tao Jiang
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, School of Medicine and Pharmacy, Ocean University of ChinaQingdao, China
| | - Qingyong Li
- Collaborative Innovation Center of Yangtze River Region Green Pharmaceuticals, Zhejiang University of TechnologyHangzhou, China
| | - Xiang Ling
- Department of Pharmacology & Therapeutics, Roswell Park Cancer InstituteBuffalo, New York, USA
- Canget BioTekpharmaBuffalo, New York, USA
| |
Collapse
|
3
|
Caron WP, Morgan KP, Zamboni BA, Zamboni WC. A Review of Study Designs and Outcomes of Phase I Clinical Studies of Nanoparticle Agents Compared with Small-Molecule Anticancer Agents. Clin Cancer Res 2013; 19:3309-15. [DOI: 10.1158/1078-0432.ccr-12-3649] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
4
|
Venditto VJ, Simanek EE. Cancer therapies utilizing the camptothecins: a review of the in vivo literature. Mol Pharm 2010; 7:307-49. [PMID: 20108971 DOI: 10.1021/mp900243b] [Citation(s) in RCA: 271] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This review summarizes the in vivo assessment-preliminary, preclinical, and clinical-of chemotherapeutics derived from camptothecin or a derivative. Camptothecin is a naturally occurring, pentacyclic quinoline alkaloid that possesses high cytotoxic activity in a variety of cell lines. Major limitations of the drug, including poor solubility and hydrolysis under physiological conditions, prevent full clinical utilization. Camptothecin remains at equilibrium in an active lactone form and inactive hydrolyzed carboxylate form. The active lactone binds to DNA topoisomerase I cleavage complex, believed to be the single site of activity. Binding inhibits DNA religation, resulting in apoptosis. A series of small molecule camptothecin derivatives have been developed that increase solubility, lactone stability and bioavailability to varying levels of success. A number of macromolecular agents have also been described wherein camptothecin(s) are covalently appended or noncovalently associated with the goal of improving solubility and lactone stability, while taking advantage of the tumor physiology to deliver larger doses of drug to the tumor with lower systemic toxicity. With the increasing interest in drug delivery and polymer therapeutics, additional constructs are anticipated. The goal of this review is to summarize the relevant literature for others interested in the field of camptothecin-based therapeutics, specifically in the context of biodistribution, dosing regimens, and pharmacokinetics with the desire of providing a useful source of comparative data. To this end, only constructs where in vivo data is available are reported. The review includes published reports in English through mid-2009.
Collapse
Affiliation(s)
- Vincent J Venditto
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
| | | |
Collapse
|
5
|
Lynam E, Landfair DJ, Wiles ME. Camptothecin Analogue Efficacy In Vitro: Effect of Liposomal Encapsulation of GI147211C (NX211). Drug Deliv 2008. [DOI: 10.1080/107175499267165] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
|
6
|
|
7
|
Abstract
Among several drug delivery systems, liposomal encapsulated anti-cancer agents represent an advanced and versatile technology. Several formulations of liposomal anthracyclines are approved, e.g. for the treatment of metastatic breast cancer (pegylated and non-pegylated liposomal doxorubicin) or AIDS-related Kaposi's sarcoma (pegylated liposomal doxorubicin and liposomal daunorubicin). Meanwhile, virtually all anti-cancer drugs have been encapsulated in liposomes using different technologies. This review will summarize preclinical and clinical data of approved and exemplary emerging liposomal anti-cancer agents.
Collapse
Affiliation(s)
- Ralf-Dieter Hofheinz
- Onkologisches Zentrum, III. Medizinische Klinik, Fakultät für Klinische Medizin Mannheim, Universität Heidelberg, Mannheim, Germany.
| | | | | | | |
Collapse
|
8
|
Kuppens IELM, Beijnen J, Schellens JHM. Topoisomerase I Inhibitors in the Treatment of Gastrointestinal Cancer: From Intravenous to Oral Administration. Clin Colorectal Cancer 2004; 4:163-80. [PMID: 15377400 DOI: 10.3816/ccc.2004.n.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This article reviews the current status of the topoisomerase I (top I) inhibitors in the treatment of gastrointestinal (GI) malignancies. We focus on oral drug administration, the mode of administration that is generally preferred by patients with cancer. However, the great majority of the studies have been performed with intravenous (I.V.) administration. The most extensively investigated GI malignancy in phase I/II studies is colorectal cancer (CRC), for which I.V. irinotecan is currently approved in the United States and Europe. We discuss the activity and efficacy of irinotecan as a single agent in CRC and in combination regimens. Also, results obtained with monotherapy and in combination treatment in other GI malignancies such as esophageal, gastric, and pancreatic cancer are discussed. Few phase I studies have been performed with oral irinotecan and its clinical activity has not yet been fully determined. Several top I inhibitors are discussed, including topotecan, 9-aminocamptothecin, rubitecan, exatecan, and lurtotecan. None of these agents, given orally or intravenously, have shown activity in CRC similar to that of I.V. irinotecan. However, several agents show promising results in other GI malignancies, eg, rubitecan and exatecan in pancreatic cancer. A complicating factor in the oral administration of the top I inhibitors is the often encountered low and variable oral bioavailability. This can partly be explained by the high affinity for the drug efflux pumps BCRP (ABCG2) and P-glycoprotein, which are highly expressed in the epithelial apical membrane of the GI tract. A novel approach to improve the oral bioavailability of the top I inhibitors by temporary blockade of the drug transporter BCRP is described.
Collapse
Affiliation(s)
- Isa E L M Kuppens
- Department of Medical Oncology, Antoni van Leeuwenhoek Hospital/The Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | | | | |
Collapse
|
9
|
Giles FJ, Tallman MS, Garcia-Manero G, Cortes JE, Thomas DA, Wierda WG, Verstovsek S, Hamilton M, Barrett E, Albitar M, Kantarjian HM. Phase I and pharmacokinetic study of a low-clearance, unilamellar liposomal formulation of lurtotecan, a topoisomerase 1 inhibitor, in patients with advanced leukemia. Cancer 2004; 100:1449-58. [PMID: 15042679 DOI: 10.1002/cncr.20132] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND OSI-211 is a low-clearance, unilamellar liposomal formulation of a water-soluble camptothecin analogue, lurtotecan. OSI-211 has significant activity in severe combined immunodeficient mouse models of human leukemia. METHODS This study was conducted to define the dose-limiting toxicities (DLT) and pharmacokinetics of OSI-211 in patients with refractory myeloid leukemias. Patients with refractory acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or chronic myelogenous leukemia in blastic phase (CML-BP) were eligible. OSI-211 was given as an intravenous infusion over 30 minutes daily for 3 days. The starting dose was 1.5 mg/m2 per day (4.5 mg/m2 per course). The dose was escalated by 50% until Grade 2 toxicity was observed and then by 30-35% until the DLT was defined. Serial plasma and urine samples were collected, and drug levels were determined by high-performance liquid chromatography with fluorescence detection. RESULTS Twenty patients (18 patients [90%] with AML, and 1 patient each [5%] with MDS and CML-BP) were treated. Mucositis and diarrhea were considered to be the DLTs. The maximum tolerated dose was 3.7 mg/m2 per day. Fourteen of 18 evaluable patients (78%) with AML or MDS achieved transient bone marrow aplasia. The mean systemic clearance of lurtotecan in plasma was 0.946 +/- 1.53 L/hour/m2. Urinary recovery of lurtotecan was 6.66% +/- 5.26% (range, 1.05-18.4%). CONCLUSIONS Liposomal encapsulation of lurtotecan altered its metabolism significantly. There was no evident correlation between exposure, as measured by plasma pharmacokinetics of lurtotecan, and clinical response or toxicities. OSI-211 merits further study in hematologic malignancies.
Collapse
Affiliation(s)
- Francis J Giles
- Department of Leukemia, The University of Texas M D Anderson Cancer Center, Houston, Texas 77030-4095, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Tomkinson B, Bendele R, Giles FJ, Brown E, Gray A, Hart K, LeRay JD, Meyer D, Pelanne M, Emerson DL. OSI-211, a novel liposomal topoisomerase I inhibitor, is active in SCID mouse models of human AML and ALL. Leuk Res 2003; 27:1039-50. [PMID: 12859997 DOI: 10.1016/s0145-2126(03)00092-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OSI-211 (liposomal lurtotecan), was evaluated using several different dose schedules (1mg/kg, d1-5, 1.75 mg/kg d1, 3, 5 and 6 mg/kg d1, 8) in severe combined immunodeficient (SCID) mouse models of acute myelogenous leukemia (AML) and acute lymphocytic leukemia (ALL) with early treatment (ET, days 6-8) or late treatment (LT, days 15-19), examining early and advanced disease, respectively. Due to the aggressive nature of the Molt-4 model, the ET and LT were accelerated to day 3 or 4 and day 8 post-implant, respectively. For each model, 2 x 10(7) (KBM-3B) or 1 x 10(7) (Molt-4, HL-60 and CEM) leukemia cells were injected intravenously into the tail vein. Each control and test group consisted of eight animals. All three schedules (1mg/kg qd1-5, 1.75 mg/kg d1, 3, 5 and 6 mg/kg d1, 8) increased the life span of OSI-211 treated animals in each model, with a tendency toward improved efficacy with the 6 mg/kg d1, 8 schedule. As a result, the activity of the 6 mg/kg d1, 8 schedule is detailed for each model. ET significantly (P<0.005) increased survival in the KBM-3B model with 86% long-term survivors (LTS). Using PRC analysis, human beta-globin gene sequences in one or several tissues were amplified in all but 3 LTS, suggesting minimal residual disease in 26 of the 29 LTS. LT also significantly (P<0.005) improved average life span in the KBM-3B model, with an average ILS=196+/-11% and one LTS. Treatment of HL-60 leukemia animals significantly (P<0.005) increased life span, with an ILS=213+/-9% and two LTS for ET, and with an ILS=219+/-4% and no LTS for LT. Treatment of Molt-4 animals, the most aggressive leukemia model tested, significantly (P<0.005) increased life span, with an average ILS=181+/-3% and no LTS for ET and an average ILS=172+/-1% with no LTS for LT. In the CEM model, ET resulted in a significantly (P<0.005) improved ILS=244+/-24% with one LTS. In comparison to OSI-211, treatment with DaunoXome, the liposomal formulation of daunorubicin, a drug with clinical efficacy in AML and ALL, had no effect on survival in the KBM-3B, nor Molt-4 A4 leukemia models when administered at its maximum or near maximum tolerated doses of 3mg/kg d1, 8. These data demonstrate that OSI-211 has potent antileukemia activity in preclinical SCID mouse AML and ALL leukemia models, supporting the clinical investigation of OSI-211 for hematological malignancies.
Collapse
Affiliation(s)
- Blake Tomkinson
- OSI Pharmaceuticals, Inc, 2860 Wilderness Place, Boulder, CO 80301, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Soepenberg O, Sparreboom A, Verweij J. Clinical studies of camptothecin and derivatives. THE ALKALOIDS. CHEMISTRY AND BIOLOGY 2003; 60:1-50. [PMID: 14593855 DOI: 10.1016/s0099-9598(03)60001-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Otto Soepenberg
- Department of Medical Oncology, Erasmus MC-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands
| | | | | |
Collapse
|
12
|
Kehrer DFS, Bos AM, Verweij J, Groen HJ, Loos WJ, Sparreboom A, de Jonge MJA, Hamilton M, Cameron T, de Vries EGE. Phase I and pharmacologic study of liposomal lurtotecan, NX 211: urinary excretion predicts hematologic toxicity. J Clin Oncol 2002; 20:1222-31. [PMID: 11870164 DOI: 10.1200/jco.2002.20.5.1222] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE To determine the maximum-tolerated and recommended dose, toxicity profile, and pharmacokinetics of the liposomal topoisomerase I inhibitor lurtotecan (NX 211) administered as a 30-minute intravenous infusion once every 3 weeks in cancer patients. PATIENTS AND METHODS NX 211 was administered by peripheral infusion. Dose escalation decisions were based on all toxicities during the first cycle as well as pharmacokinetic parameters. Serial plasma, whole blood, and urine samples were collected for up to 96 hours after the end of infusion, and drug levels were determined by high-performance liquid chromatography. RESULTS Twenty-nine patients (16 women; median age, 56 years; range, 39 to 74 years) received 77 courses of NX 211 at dose levels of 0.4 (n = 3), 0.8 (n = 6), 1.6 (n = 3), 3.2 (n = 6), 3.8 (n = 6), and 4.3 mg/m(2) (n = 5). Neutropenia and thrombocytopenia were the dose-limiting toxicities and were not cumulative. Other toxicities were mild to moderate. Nine patients had stable disease while undergoing treatment. The systemic clearance of lurtotecan in plasma and whole blood was 0.82 +/- 0.78 L/h/m(2) and 1.15 +/- 0.96 L/h/m(2), respectively. Urinary recovery (Fu) of lurtotecan was 10.1% +/- 4.05% (range, 4.9% to 18.9%). In contrast to systemic exposure measures, the dose excreted in urine (ie, dose x Fu) was significantly related to the percent decrease in neutrophil and platelet counts at nadir (P <.00001). CONCLUSION The dose-limiting toxicities of NX 211 are neutropenia and thrombocytopenia. The recommended dose for phase II studies is 3.8 mg/m(2) once every 3 weeks. Pharmacologic data suggest a relationship between exposure to lurtotecan and NX 211-induced clinical effects.
Collapse
Affiliation(s)
- Diederik F S Kehrer
- Department of Medical Oncology, Rotterdam Cancer Institute, Daniel den Hoed Kliniek and University Hospital, Rotterdam, The Netherlands.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Schellens JHM, Heinrich B, Lehnert M, Gore ME, Kaye SB, Dombernowsky P, Paridaens R, van Oosterom AT, Verweij J, Loos WJ, Calvert H, Pavlidis N, Cortes-Funes H, Wanders J, Roelvink M, Sessa C, Selinger K, Wissel PS, Gamucci T, Hanauske AR. Population pharmacokinetic and dynamic analysis of the topoisomerase I inhibitor lurtotecan in phase II studies. Invest New Drugs 2002; 20:83-93. [PMID: 12003197 DOI: 10.1023/a:1014454821885] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Population pharmacokinetic-dynamic analysis was prospectively integrated in a broad phase II program of lurtotecan (GI147211), a novel camptothecin derived topoisomerase I inhibitor, to determine the population pharmacokinetic profile in a larger population, to estimate individual pharmacokinetic parameters and to investigate relationships with clinical outcome. A sparse sampling method was applied during course one, which involved two sampling time-points. A Bayesian algorithm was used to estimate individual pharmacokinetic parameters, in particular total plasma clearance (CL) and volume of distribution. In total, samples were collected of 109 (63%) of 173 patients. Pharmacokinetic-dynamic evaluation could be carried out successfully in 85 (78%) of the sampled patients. CL of lurtotecan showed substantial variability (mean 87 +/- 28 L/h) and was of the same magnitude as in the phase I studies where full pharmacokinetic curves were used. Residual variability in the population estimate of CL was 9.9%. No significant relationships were observed between exposure parameters and toxicity nor likelihood of tumor response, however the latter relationship may well have been obscured by the heterogeneity of the studied population. Prospective implementation of large scale population pharmacokinetic-dynamic analysis is feasible and important to establish whether interpatient variability in drug exposure is a major determinant of toxicity or activity.
Collapse
Affiliation(s)
- J H M Schellens
- Department of Medical Oncology, The Netherlands Cancer Institute, Amsterdam.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Abstract
Camptothecin analogues and derivatives appear to exert their antitumour activity by binding to topoisomerase I and have shown significant activity against a broad range of tumours. In general, camptothecins are not substrates for either the multidrug-resistance P-glycoprotein or the multidrug-resistance-associated protein (MRP). Because of manageable toxicity and encouraging activity against solid tumours, camptothecins offer promise in the clinical management of human tumours. This review illustrates the proposed mechanism(s) of action of camptothecins and presents a concise overview of current camptothecin therapy, including irinotecan and topotecan, and novel analogues undergoing clinical trails, such as exatecan (DX-8951f), IDEC-132 (9-aminocamptothecin), rubitecan (9-nitrocamptothecin), lurtotecan (GI-147211C), and the recently developed homocamptothecins diflomotecan (BN-80915) and BN-80927.
Collapse
Affiliation(s)
- Hulya Ulukan
- Division of Pharmaceutics, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210-1291, USA
| | | |
Collapse
|
15
|
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.
Collapse
Affiliation(s)
- L Zufía
- Pharmacy Department, University Hospital of Navarra, Pamplona, Spain
| | | | | |
Collapse
|
16
|
Abstract
The topoisomerase I inhibitors such as irinotecan and topotecan are active agents against small-cell lung cancer that are effective in treating not only chemotherapy-naïve tumors but also progressed-stage tumors after treatment with cisplatin-based regimens, because their mechanism of antitumor activity differs from that of the agents included in standard chemotherapy for small-cell lung cancer. Etoposide plus cisplatin or etoposide plus cisplatin alternating with cyclophosphamide, doxorubicin, and vincristine is considered the standard regimen for small-cell lung cancer. No new standard combination chemotherapy for small-cell lung cancer has been developed over the past decade. Irinotecan with cisplatin is now established as a new standard chemotherapy for extensive-stage small-cell lung cancer based on the results of the Japan Clinical Oncology Group trial. Of course, confirmation through phase III studies will be extremely important. The Japan Clinical Oncology Group is intensively investigating other irinotecan-containing regimens and the incorporation of irinotecan into treatment of patients with limited-stage small-cell lung cancer.
Collapse
Affiliation(s)
- Y Ohe
- Department of Internal Medicine, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan
| | | |
Collapse
|
17
|
Desjardins JP, Abbott EA, Emerson DL, Tomkinson BE, Leray JD, Brown EN, Hamilton M, Dihel L, Ptaszynski M, Bendele RA, Richardson FC. Biodistribution of NX211, liposomal lurtotecan, in tumor-bearing mice. Anticancer Drugs 2001; 12:235-45. [PMID: 11290871 DOI: 10.1097/00001813-200103000-00009] [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: 11/26/2022]
Abstract
Prolonging tumor exposure to topoisomerase I inhibitors has been correlated to enhance the efficacy of those agents. Lurtotecan, a water-soluble camptothecin analog, was formulated as a liposomal drug, NX211, to enhance the delivery of drug to tumors. Tumor-bearing mice were treated with either [14C]NX211 containing [14C]lurtotecan, [3H]NX211 containing [3H]phosphatidylcholine or [14C]lurtotecan, euthanized at selected times post-injection, and tissues, plasma, urine and feces were collected. These studies demonstrated that KB tumors of [14C]NX211-treated mice had approximately 70-fold greater concentrations of [14C]lurtotecan at 24 h, respectively, compared to concentrations of [14C]lurtotecan of the KB tumors of [14C]lurtotecan-treated mice. The area under curve (AUC) from 0 to 48 h of [14C]lurtotecan for the KB tumors of [14C]NX211-treated animals was over 17-fold greater than the AUC of [14C]lurtotecan for the tumors of [14C]lurtotecan-treated animals. Treatment with [3H]NX211 demonstrated that the lipid component continually accumulated over 24 h in the tissues. HPLC analysis of extracted material from tumors of [14C]NX211-treated mice showed that more than 95% of the radioactive material was intact [14C]lurtotecan. These findings are one of the keys justifying the development of a liposomal formulation of lurtotecan, which has the intent to increase tumor exposure and increase antitumor efficacy.
Collapse
Affiliation(s)
- J P Desjardins
- Gilead Sciences, Inc, 2860 Wilderness Place, Boulder, CO 80301, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Kehrer DF, Soepenberg O, Loos WJ, Verweij J, Sparreboom A. Modulation of camptothecin analogs in the treatment of cancer: a review. Anticancer Drugs 2001; 12:89-105. [PMID: 11261892 DOI: 10.1097/00001813-200102000-00002] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The topoisomerase I inhibitors reviewed in this paper are all semisynthetic analogs of camptothecin (CPT). Modulation of this intranuclear enzyme translates clinically in to antitumor activity against a broad spectrum of tumors and is therefore the subject of numerous investigations. We present preclinical and clinical data on CPT analogs that are already being used in clinical practice [i.e. topotecan and irinotecan (CPT-11)] or are currently in clinical development (e.g. 9-aminocamptothecin, 9-nitrocamptotecin, lurtotecan, DX 8951f and BN 80915), as well as drugs that are still only developed in a preclinical setting (silatecans, polymer-bound derivates). A variety of different strategies is being used to modulate the systemic delivery of this class of agents, frequently in order to increase antitumor activity and/or reduce experienced side effects. Three principal approaches are discussed, including: (i) pharmaceutical modulation of formulation vehicles, structural alterations and the search for more water-soluble prodrugs, (ii) modulation of routes of administration and considerations on infusion duration, and (iii) both pharmacodynamic and pharmacokinetic biomodulation.
Collapse
Affiliation(s)
- D F Kehrer
- Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek) and University Hospital, The Netherlands.
| | | | | | | | | |
Collapse
|
19
|
Gamucci T, Paridaens R, Heinrich B, Schellens JH, Pavlidis N, Verweij J, Sessa C, Kaye S, Roelvink M, Wanders J, Hanauske A. Activity and toxicity of GI147211 in breast, colorectal and non-small-cell lung cancer patients: an EORTC-ECSG phase II clinical study. Ann Oncol 2000; 11:793-7. [PMID: 10997805 DOI: 10.1023/a:1008373031714] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND GI147211 is a water-soluble synthetic analogue of camptothecin showing promising in vivo and in vitro antitumor activity and an acceptable toxicity profile. PATIENTS AND METHODS Between April 1995 and November 1996, 67 eligible patients with pretreated breast cancer (25 patients) and chemo-naïve colorectal (19 patients) and non-small-cell lung cancer (23 patients) were entered into three multicentric, non-randomized phase II trials. Treatment schedule consisted of intravenous GI1147211 administered at a dose of 1.2 mg/m2/day for five consecutive days every three weeks. RESULTS Hematological toxicity was common with grade 3-4 neutropenia in 54% of patients and neutropenic fever together or not associated with infection in 14.5% of patients. Grade 3-4 thrombocytopenia and grade 2-4 anemia were observed in 20% and in 68% of patients, respectively. Non-hematological toxicity was generally mild to moderate and consisted mainly of gastrointestinal toxicity, asthenia and alopecia. A dose-escalation to 1.5 mg/m2/d was feasible in 17 (25%) patients. The antitumor activity of GI1147211 was moderate in breast cancer patients (3 partial responses (PRs), response rate (RR) 13%) and minimal in non-small cell lung cancer patients (2 PRs, RR 9%). No objective responses were obtained in colorectal patients. CONCLUSIONS GI147211, at the dose and schedule employed in this study, showed an acceptable safety profile but a modest antitumor activity in the examined tumor types.
Collapse
Affiliation(s)
- T Gamucci
- Division of Medical Oncology 1, Regina Elena Cancer Institute, Rome, Italy.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Gelderblom HA, DE Jonge MJ, Sparreboom A, Verweij J. Oral topoisomerase 1 inhibitors in adult patients: present and future. Invest New Drugs 2000; 17:401-15. [PMID: 10759406 DOI: 10.1023/a:1006394610219] [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: 11/12/2022]
Abstract
The renewed interest in topoisomerase 1 inhibitors, based on new insights on the mechanism of action and the development of semi-synthetic derivates of camptothecin with a more favourable toxicity profile, has led to extensive preclinical and clinical research. Significant levels of anti-tumor activity in human tumor xenografts were seen especially with prolonged duration of exposure. Since oral drug delivery is a more convenient method for prolonged drug administration, and preferred by patients, further development of oral formulations seems attractive. Common concerns in the development of oral formulations are their sometimes low oral bioavailability and the frequently large intra- and interpatient variation in systemic exposure. Efforts to improve absorption and minimize intestinal metabolism/efflux of the oral chemotherapeutic agent using new formulas might lead to better bioavailability. Pharmacokinetic and pharmacodynamic evaluations have enabled guidance in recommendations of schedules. Given the interpatient variation in exposure it is interesting to note that flat dosing of topotecan resulted in the same systemic exposure compared with the more complex dosing per body surface area. In order to diminish the interpatient variation in exposure to 9-AC a limited sampling model for oral 9-AC was developed, enabling prediction of the systemic exposure for 9-AC and optimizing treatment for any given patient. Drug sequencing plays a key role in the combination topotecan/cisplatin and might be important for combination with other classes of drugs. Therefore, forthcoming phase 1 trials on combination therapy with oral topoisomerase 1 inhibitors should include studies on sequence dependence and pharmacokinetic analyses to evaluate any mutual interaction.
Collapse
Affiliation(s)
- H A Gelderblom
- Department of Medical Oncology, Rotterdam Cancer Institute, (Daniel den Hoed Kliniek) and Universit) Hospital Rotterdam, The Netherlands.
| | | | | | | |
Collapse
|
21
|
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%.
Collapse
Affiliation(s)
- W J Loos
- Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek), The Netherlands.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Stevenson JP, DeMaria D, Sludden J, Kaye SB, Paz-Ares L, Grochow LB, McDonald A, Selinger K, Wissel P, O'Dwyer PJ, Twelves C. Phase I/pharmacokinetic study of the topoisomerase I inhibitor GG211 administered as a 21-day continuous infusion. Ann Oncol 1999; 10:339-44. [PMID: 10355580 DOI: 10.1023/a:1008313011289] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Preclinical results support a prolonged schedule of administration for topoisomerase I inhibitors, and we have previously demonstrated the safety and activity of the novel water-soluble topoisomerase I inhibitor GG211 when given as a 72-hour continuous infusion to cancer patients. PATIENTS AND METHODS In a three-center international phase I trial, 38 patients received GG211 doses from 0.3 to 0.5 mg/m2/day by continuous intravenous infusions for seven, 14, and 21 days. Patients' median performance status was 1; nearly half had colorectal cancer, and 35 patients had prior chemotherapy. RESULTS The first patient cohort received 0.3 mg/m2/day for seven days with no significant toxicities. Subsequent cohorts received continuous infusions for 14 and 21 days at this dose level with only mild myelosuppression noted. Dose-escalation on the 21-day schedule was then performed. No dose-limiting toxicity occurred at the 0.4 mg/m2/day dose level. Thrombocytopenia was dose-limiting with 0.5 mg/m2/day dosing but was not cumulative. Other grade 3 4 toxicities included neutropenia, nausea, vomiting, diarrhea, and fatigue. Partial responses occurred with 21-day infusion in two patients with breast and ovarian cancer at the 0.3 and 0.4 mg/m2/day dose levels, respectively. Mean GG211 lactone Css ranged from 0.17 to 0.64 ng/ml. CONCLUSION The maximum tolerated dose of GG211 administered as a 21-day continuous infusion is 0.4 mg/m2/day with antitumor activity noted at tolerable doses.
Collapse
Affiliation(s)
- J P Stevenson
- University of Pennsylvania Cancer Center, Philadelphia, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
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.
Collapse
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.
| | | | | |
Collapse
|
24
|
Abstract
DNA topoisomerase I is a nuclear enzyme which catalyzes the conversion of the DNA topology by introducing single-strand breaks into the DNA molecule. This enzyme represents a novel and distinct molecule target for cancer therapy by antitopoisomerase drugs belonging to the campthotecin series of antineoplastics. As many tumors can acquire resistance to drug treatment and become refractary to the chemotherapy it is very important to investigate the mechanisms involved in such a drug resistance for circumventing the phenomenon. This article describes the role of topoisomerase I in cell functions and the methods used to assess its in vitro catalytic activity. It reviews the mechanisms of cytotoxicity of the most specific antitopoisomerase I drugs by considering also the phenomenon of drug resistance. Some factors useful to drive the future perspectives in the development of new topoisomerase I inhibitors are also evidenced and discussed.
Collapse
Affiliation(s)
- R E Parchment
- Division of Hematology-Oncology, The Barbara Ann Karmanos Cancer Institute, Wayne State University, 3900 John R., Detroit, MI, U.S.A
| | | |
Collapse
|
25
|
Topoisomerase I-targeting drugs. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1067-568x(98)80005-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
26
|
|
27
|
Abstract
This review presents a summary of preclinical and clinical data on the topoisomerase I (topo I) inhibitors that are under clinical development. To date, all of the topo I inhibitors that have been clinically evaluated are analogues of camptothecin, an extract of the Chinese tree Camptotheca acuminata. The therapeutic development of camptothecin was initially limited by its poor solubility and unpredictable toxicity. More recently, a number of water-soluble camptothecin analogues have undergone extensive evaluation and have demonstrated significant clinical activity. These include irinotecan (CPT-II), topotecan, and 9-aminocamptothecin (9-AC). Preliminary data are also reviewed on other camptothecin analogues (GG-211 and DX-8951f), on oral formulations, and on non-camptothecin topoisomerase I inhibitors. The topoisomerase I inhibitors have already demonstrated a broad spectrum of antitumour activity, most probably due to their unique mechanism of action and lack of clinical cross-resistance with existing antineoplastic compounds. The challenge for the next five years is to identify ways to integrate the topo I inhibitors into multidrug and multimodality therapies to achieve optimal antitumour effect, while keeping the side effects of these therapies manageable.
Collapse
Affiliation(s)
- M L Rothenberg
- Division of Medical Oncology, University of Texas Health Science Center at San Antonio, USA
| |
Collapse
|
28
|
Wang HK, Morris-Natschke SL, Lee KH. Recent advances in the discovery and development of topoisomerase inhibitors as antitumor agents. Med Res Rev 1997; 17:367-425. [PMID: 9211397 DOI: 10.1002/(sici)1098-1128(199707)17:4<367::aid-med3>3.0.co;2-u] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- H K Wang
- Natural Products Laboratory, School of Pharmacy, University of North Carolina, Chapel Hill 27599, USA
| | | | | |
Collapse
|
29
|
Gerrits CJ, de Jonge MJ, Schellens JH, Stoter G, Verweij J. Topoisomerase I inhibitors: the relevance of prolonged exposure for present clinical development. Br J Cancer 1997; 76:952-62. [PMID: 9328159 PMCID: PMC2228255 DOI: 10.1038/bjc.1997.491] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Topoisomerase I inhibitors constitute a new class of anti-cancer agents. Recently, topotecan and irinotecan were registered for clinical use in ovarian cancer and colorectal cancer respectively. Cytotoxicity of topoisomerase I inhibitors is S-phase specific, and in vitro and in vivo studies have suggested that, for efficacy, prolonged exposure might be more important than short-term exposure to high concentration. Clinical development of those topoisomerase I inhibitors that have reached this stage is also focused on schedules aiming to achieve prolonged exposure. In this review, we summarize all published preclinical studies on this topic for topoisomerase I inhibitors in clinical development, namely 20-S-camptothecin, 9-nitro-camptothecin, 9-amino-camptothecin, topotecan, irinotecan and GI147211. In addition, preliminary data on clinical studies concerning this topic are also reviewed. The data suggest that prolonged exposure may indeed be relevant for anti-tumour activity. However, the optimal schedule is yet to be determined. Finally, clinical data are yet too immature to draw definitive conclusions.
Collapse
Affiliation(s)
- C J Gerrits
- Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek) and University Hospital, The Netherlands
| | | | | | | | | |
Collapse
|
30
|
Gerrits CJ, Schellens JH, Creemers GJ, Wissel P, Planting AS, Pritchard JF, DePee S, de Boer-Dennert M, Harteveld M, Verweij J. The bioavailability of oral GI147211 (GG211), a new topoisomerase I inhibitor. Br J Cancer 1997; 76:946-51. [PMID: 9328158 PMCID: PMC2228077 DOI: 10.1038/bjc.1997.490] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Topoisomerase I inhibitors are new compounds of interest for cancer chemotherapy. We performed a study with GI147211, a new semisynthetic camptothecin analogue, to determine the absolute bioavailability of the drug given orally. Patients with a histologically confirmed diagnosis of a solid tumour refractory to standard forms of therapy were eligible for the study. GI147211 was given orally on day 1 and as a 30-min infusion daily on days 2-5. The treatment course was repeated every 3 weeks. In subsequent patient cohorts, the dose of the oral formulation was escalated from 1.5 mg m(-2) to 6.0 mg m(-2); the dose for i.v. administration was fixed at 1.2 mg m(-2). Plasma pharmacokinetics was performed on day 1 and 2 of the first course and on day 1 of the second course using a validated high-performance liquid chromatographic assay. Nineteen patients were entered into the study; one patient was not evaluable because the treatment course was stopped prematurely. Eighteen patients received a total of 47 treatment courses. The absolute bioavailability of GI147211 averaged 1.3 +/- 5.2%. Drug appeared quickly in plasma with a median Tmax at 0.5 h. Fasting or fed state had no significant influence on the bioavailability of GI147211. The terminal half-life after administration of oral GI147211 was 6.85 +/- 3.13 h, similar to the half-life after intravenous administration. The major toxicities were neutropenia and thrombocytopenia. Nadirs for neutropenia and thrombocytopenia occurred on day 8 and day 15 respectively. Other toxicities predominantly consisted of mild and infrequent nausea and vomiting, and fatigue. The oral administration of the drug is well tolerated. Oral administration of topoisomerase I inhibitor GI147211 results in a low bioavailability with relatively wide interpatient variation. The intravenous route of administration is advised for further development of this promising topoisomerase I inhibitor.
Collapse
Affiliation(s)
- C J Gerrits
- Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek) and University Hospital, The Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|