Abstract
Purpose
To determine whether entrapped transition metals could mediate the active encapsulation of the anticancer drug irinotecan into preformed liposomes. Further, to establish that metal complexation could stabilize liposomal irinotecan in the therapeutically active lactone conformation.
Materials and Methods
Irinotecan was added to preformed 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/chol) liposomes prepared in CuSO4, ZnSO4, MnSO4, or CoSO4 solutions, and drug encapsulation was determined over time. The roles of the transmembrane pH gradient and internal pH were evaluated. TLC and HPLC were used to monitor drug stability and liposome morphology was assessed by cryo-TEM.
Results
Irinotecan was rapidly and efficiently loaded into preformed liposomes prepared in unbuffered (∼pH 3.5) 300 mM CuSO4 or ZnSO4. For Cu-containing liposomes, results suggested that irinotecan loading occurred when the interior pH and the exterior pH were matched; however, addition of nigericin to collapse any residual transmembrane pH gradient inhibited irinotecan loading. Greater than 90% of the encapsulated drug was in its active lactone form and cryo-TEM analysis indicated dark intravesicular electron-dense spots.
Conclusion
Irinotecan is stably entrapped in the active lactone conformation within preformed copper-containing liposomes as a result of metal–drug complexation.
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References
Y. H. Hsiang, H. Y. Wu, and L. F. Liu. Topoisomerases: novel therapeutic targets in cancer chemotherapy. Biochem. Pharmacol. 37:1801–1802 (1988).
Y. H. Hsiang and L. F. Liu. Identification of mammalian DNA topoisomerase I as an intracellular target of the anticancer drug camptothecin. Cancer Res. 48:1722–1726 (1988).
Y. H. Hsiang, M. G. Lihou, and L. F. Liu. Arrest of replication forks by drug-stabilized topoisomerase I-DNA cleavable complexes as a mechanism of cell killing by camptothecin. Cancer Res. 49:5077–5082 (1989).
L. Saltz. Irinotecan-based combinations for the adjuvant treatment of stage III colon cancer. Oncology (Willist. Park N. Y.) 14:47–50 (2000).
L. B. Saltz, J. V. Cox, C. Blanke, L. S. Rosen, L. Fehrenbacher, M. J. Moore, J. A. Maroun, S. P. Ackland, P. K. Locker, N. Pirotta, G. L. Elfring, and L. L. Miller. Irinotecan plus fluorouracil and leucovorin for metastatic colorectal cancer. Irinotecan Study Group. N. Engl. J. Med. 343:905–914 (2000).
K. Noda, Y. Nishiwaki, M. Kawahara, S. Negoro, T. Sugiura, A. Yokoyama, M. Fukuoka, K. Mori, K. Watanabe, T. Tamura, S. Yamamoto, and N. Saijo. Irinotecan plus cisplatin compared with etoposide plus cisplatin for extensive small-cell lung cancer. N. Engl. J. Med. 346:85–91 (2002).
K. Sai, N. Kaniwa, S. Ozawa, and J. Sawada. An analytical method for irinotecan (CPT-11) and its metabolites using a high-performance liquid chromatography: parallel detection with fluorescence and mass spectrometry. Biomed. Chromatogr. 16:209–218 (2002).
Y. Kawato, M. Aonuma, Y. Hirota, H. Kuga, and K. Sato. Intracellular roles of SN-38, a metabolite of the camptothecin derivative CPT-11, in the antitumor effect of CPT-11. Cancer Res. 51:4187–4191 (1991).
F. Lavelle, M. C. Bissery, S. Andre, F. Roquet, and J. F. Riou. Preclinical evaluation of CPT-11 and its active metabolite SN-38. Semin. Oncol. 23:11–20 (1996).
T. G. Burke and D. Bom. Camptothecin design and delivery approaches for elevating anti-topoisomerase I activities in vivo. Ann. N. Y. Acad. Sci. 922:36–45 (2000).
T. G. Burke and Z. Mi. The structural basis of camptothecin interactions with human serum albumin: impact on drug stability. J. Med. Chem. 37:40–46 (1994).
V. Knight, E. S. Kleinerman, J. C. Waldrep, B. C. Giovanella, B. E. Gilbert, and N. V. Koshkina. 9-Nitrocamptothecin liposome aerosol treatment of human cancer subcutaneous xenografts and pulmonary cancer metastases in mice. Ann. N. Y. Acad. Sci. 922:151–163 (2000).
V. Peikov, S. Ugwu, M. Parmar, A. Zhang, and I. Ahmad. pH-dependent association of SN-38 with lipid bilayers of a novel liposomal formulation. Int. J. Pharm. 299:92-99 (2005).
S. S. Daoud, M. I. Fetouh, and B. C. Giovanella. Antitumor effect of liposome-incorporated camptothecin in human malignant xenografts. Anticancer Drugs 6:83–93 (1995).
P. Tardi, E. Choice, D. Masin, T. Redelmeier, M. Bally, and T. D. Madden. Liposomal encapsulation of topotecan enhances anticancer efficacy in murine and human xenograft models. Cancer Res. 60:3389–3393 (2000).
C. L. Messerer, E. C. Ramsay, D. Waterhouse, R. Ng, E. M. Simms, N. Harasym, P. Tardi, L. D. Mayer, and M. B. Bally. Liposomal irinotecan: formulation development and therapeutic assessment in murine xenograft models of colorectal cancer. Clin. Cancer Res. 10(19):6638–6649 (2004).
J. J. Liu, R. L. Hong, W. F. Cheng, K. Hong, F. H. Chang, and Y. L. Tseng. Simple and efficient liposomal encapsulation of topotecan by ammonium sulfate gradient: stability, pharmacokinetic and therapeutic evaluation. Anticancer Drugs 13:709–717 (2002).
S. A. Abraham, K. Edwards, G. Karlsson, N. Hudon, L. D. Mayer, and M. B. Bally. An evaluation of transmembrane ion gradient-mediated encapsulation of topotecan within liposomes. J. Control. Release 96:449–461 (2004).
G. Haran, R. Cohen, L. K. Bar, and Y. Barenholz. Transmembrane ammonium sulfate gradients in liposomes produce efficient and stable entrapment of amphipathic weak bases. Biochim. Biophys. Acta 1151:201–215 (1993).
D. B. Fenske, K. F. Wong, E. Maurer, N. Maurer, J. M. Leenhouts, N. Boman, L. Amankwa, and P. R. Cullis. Ionophore-mediated uptake of ciprofloxacin and vincristine into large unilamellar vesicles exhibiting transmembrane ion gradients. Biochim. Biophys. Acta 1414:188–204 (1998).
S. A. Abraham, K. Edwards, G. Karlsson, S. MacIntosh, L. D. Mayer, C. McKenzie, and M. B. Bally. Formation of transition metal-doxorubicin complexes inside liposomes. Biochim. Biophys. Acta 1565:41–54 (2002).
N. Farrell. Biomedical uses and applications of inorganic chemistry. An overview. Coord. Chem. Rev. 232:1–4 (2002).
N. Farrell. Metal complexes as drugs and chemotherapeutic agents. In J. A. McCleverty, and T. J. Meyer (eds.), Comprehensive Coordination Chemistry. II. Applications of Coordination Chemistry, vol. 9, Elsevier, Amsterdam, 2003, pp. 809–840.
Z. Guo and P. J. Sadler. Metals in medicine. Angew. Chem., Int. Ed. 38:1512–1531 (1999).
V. Sharma and D. Piwnica-Worms. Metal complexes for therapy and diagnosis of drug resistance. Chem. Rev. 99:2545–2560 (1999).
J. Kuwahara, T. Suzuki, K. Funakoshi, and Y. Sugiura. Photosensitive DNA cleavage and phage inactivation by copper(II)-camptothecin. Biochemistry 25:1216–1221 (1986).
M. J. Hope, M. B. Bally, G. Webb, and P. R. Cullis. Production of large unilamellar vesicles by a rapid extrusion procedure. Characterization of size distribution, trapped volume and ability to maintain a membrane potential. Biochim. Biophys. Acta, Biomembr. 812:55–65 (1985).
P. R. Harrigan, K. F. Wong, T. E. Redelmeier, J. J. Wheeler, and P. R. Cullis. Accumulation of doxorubicin and other lipophilic amines into large unilamellar vesicles in response to transmembrane pH gradients. Biochim. Biophys. Acta 1149:329–338 (1993).
N. Dos Santos, K. A. Cox, C. A. McKenzie, F. van Baarda, R. C. Gallagher, G. Karlsson, K. Edwards, L. D. Mayer, C. Allen, and M. B. Bally. pH gradient loading of anthracyclines into cholesterol-free liposomes: enhancing drug loading rates through use of ethanol. Biochim. Biophys. Acta 1661:47–60 (2004).
D. F. Chollet, L. Goumaz, A. Renard, G. Montay, L. Vernillet, V. Arnera, and D. J. Mazzo. Simultaneous determination of the lactone and carboxylate forms of the camptothecin derivative CPT-11 and its metabolite SN-38 in plasma by high-performance liquid chromatography. J. Chromatogr., B, Biomed. Sci. Appl. 718:163–175 (1998).
D. W. Deamer, R. C. Prince, and A. R. Crofts. The response of fluorescent amines to pH gradients across liposome membranes. Biochim. Biophys. Acta 274:323–335 (1972).
D. L. Daleke, K. Hong, and D. Papahadjopoulos. Endocytosis of liposomes by macrophages: binding, acidification and leakage of liposomes monitored by a new fluorescence assay. Biochim. Biophys. Acta 1024:352–366 (1990).
L. L. Jung and W. C. Zamboni. Cellular, pharmacokinetic, and pharmacodynamic aspects of response to camptothecins: can we improve it? Drug Resist. Updat. 4:273–288 (2001).
J. Fassberg and V. J. Stella. A kinetic and mechanistic study of the hydrolysis of camptothecin and some analogues. J. Pharm. Sci. 81:676–684 (1992).
V. Brezova, M. Valko, M. Breza, H. Morris, J. Telser, D. Dvoranova, K. Kaiserova, L. Varecka, M. Mazur, and D. Leibfritz. Role of radicals and singlet oxygen in photoactivated DNA cleavage by the anticancer drug camptothecin: an electron paramagnetic resonance study. J. Phys. Chem. B 107:2415–2425 (2003).
A. S. Taggar, J. Alnajim, M. Anantha, A. Thomas, M. Webb, E. Ramsay, M. B. Bally. Copper-topotecan complexation mediates drug accumulation into liposomes. J. Control.Release 114(1):78–88 (2006).
Acknowledgment
This research was supported by the Canadian Institutes of Health Research (CIHR).
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Ramsay, E., Alnajim, J., Anantha, M. et al. Transition Metal-Mediated Liposomal Encapsulation of Irinotecan (CPT-11) Stabilizes the Drug in the Therapeutically Active Lactone Conformation. Pharm Res 23, 2799–2808 (2006). https://doi.org/10.1007/s11095-006-9111-5
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DOI: https://doi.org/10.1007/s11095-006-9111-5