The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Marcel B. Bally - One of the best experts on this subject based on the ideXlab platform.
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the role of the transition metal copper and the ionophore a23187 in the development of irinophore c
Pharmaceutical Research, 2011Co-Authors: Nilesh Patankar, Marcel B. Bally, Euan Ramsay, Malathi Anantha, Dawn WaterhouseAbstract:Purpose A liposomal Irinotecan formulation referred to as Irinophore C relies on the ability of copper to complex Irinotecan within the liposome. It is currently being evaluated for critical drug-loading parameters. Studies presented here were designed to determine the optimum copper concentration required for the effective encapsulation and retention of Irinotecan into liposomes.
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a novel liposomal Irinotecan formulation with significant anti tumour activity use of the divalent cation ionophore a23187 and copper containing liposomes to improve drug retention
European Journal of Pharmaceutics and Biopharmaceutics, 2008Co-Authors: Euan Ramsay, Murray S. Webb, Marcel B. Bally, Jehan Alnajim, Malathi Anantha, Jason Zastre, Dawn Waterhouse, Hong YanAbstract:We determined whether the method used to encapsulate Irinotecan into 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/Chol; 55:45 mol%) liposomes influenced: (i) Irinotecan release rate and (ii) therapeutic efficacy. DSPC/Chol (55:45 mol%) liposomes were prepared with: (i) unbuffered CuSO4; (ii) buffered (pH 7.5) CuSO4; (iii) unbuffered MnSO4 and the ionophore A23187 (exchanges internal metal2+ with external 2H+ to establish and maintain a transmembrane pH gradient); and (iv) unbuffered CuSO4 and ionophore A23187. All formulations exhibited >98% Irinotecan encapsulation (0.2 drug-to-lipid molar ratio; 10 min incubation at 50 degrees C). Following a single intravenous injection (100mg/kg Irinotecan) into Balb/c mice, the unbuffered CuSO4 plus A23187 formulation mediated a half-life of Irinotecan release of 44.4h; a >or=4-fold increase compared to the other liposome formulations. This surprising observation demonstrated that the CuSO4 plus A23187 formulation enhanced Irinotecan retention compared to the MnSO4 plus A23187 formulation, indicating the importance of the divalent metal. A single dose of the CuSO4 plus A23187 formulation (50mg/kg Irinotecan) mediated an 18-fold increase in median T-C (the difference in days for treated and control subcutaneous human LS 180 adenocarcinoma xenografts to increase their initial volume by 400%) when compared to a comparable dose of Camptosar. Improved Irinotecan retention was associated with increased therapeutic activity.
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a novel liposomal Irinotecan formulation with significant anti tumour activity use of the divalent cation ionophore a23187 and copper containing liposomes to improve drug retention
European Journal of Pharmaceutics and Biopharmaceutics, 2008Co-Authors: Euan Ramsay, Murray S. Webb, Marcel B. Bally, Jehan Alnajim, Malathi Anantha, Jason Zastre, Dawn WaterhouseAbstract:We determined whether the method used to encapsulate Irinotecan into 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/Chol; 55:45 mol%) liposomes influenced: (i) Irinotecan release rate and (ii) therapeutic efficacy. DSPC/Chol (55:45 mol%) liposomes were prepared with: (i) unbuffered CuSO4; (ii) buffered (pH 7.5) CuSO4; (iii) unbuffered MnSO4 and the ionophore A23187 (exchanges internal metal2+ with external 2H+ to establish and maintain a transmembrane pH gradient); and (iv) unbuffered CuSO4 and ionophore A23187. All formulations exhibited >98% Irinotecan encapsulation (0.2 drug-to-lipid molar ratio; 10 min incubation at 50 °C). Following a single intravenous injection (100 mg/kg Irinotecan) into Balb/c mice, the unbuffered CuSO4 plus A23187 formulation mediated a half-life of Irinotecan release of 44.4 h; a 4-fold increase compared to the other liposome formulations. This surprising observation demonstrated that the CuSO4 plus A23187 formulation enhanced Irinotecan retention compared to the MnSO4 plus A23187 formulation, indicating the importance of the divalent metal. A single dose of the CuSO4 plus A23187 formulation (50 mg/kg Irinotecan) mediated an 18-fold increase in median T − C (the difference in days for treated and control subcutaneous human LS 180 adenocarcinoma xenografts to increase their initial volume by 400%) when compared to a comparable dose of Camptosar®. Improved Irinotecan retention was associated with increased therapeutic activity.
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Coencapsulation of Irinotecan and floxuridine into low cholesterol-containing liposomes that coordinate drug release in vivo.
Biochimica et Biophysica Acta, 2006Co-Authors: Paul Tardi, Ryan C. Gallagher, Sharon Johnstone, Natashia Harasym, Murray S. Webb, Marcel B. Bally, Lawrence D MayerAbstract:A liposomal delivery system that coordinates the release of Irinotecan and floxuridine in vivo has been developed. The encapsulation of floxuridine was achieved through passive entrapment while Irinotecan was actively loaded using a novel copper gluconate/triethanolamine based procedure. Coordinating the release rates of both drugs was achieved by altering the cholesterol content of distearoylphosphatidylcholine (DSPC)/distearoylphosphatidylglycerol (DSPG) based formulations. The liposomal retention of floxuridine in plasma after intravenous injection was dramatically improved by decreasing the cholesterol content of the formulation below 20 mol%. In the case of Irinotecan, the opposite trend was observed where increasing cholesterol content enhanced drug retention. Liposomes composed of DSPC/DSPG/Chol (7:2:1, mole ratio) containing co-encapsulated Irinotecan and floxuridine at a 1:1 molar ratio exhibited matched leakage rates for the two agents so that the 1:1 ratio was maintained after intravenous administration to mice. The encapsulation of Irinotecan was optimal when copper gluconate/triethanolamine (pH 7.4) was used as the intraliposomal buffer. The efficiency of Irinotecan loading was approximately 80% with a starting drug to lipid molar ratio of 0.1/1. Leakage of floxuridine from the liposomes during Irinotecan loading at 50 °C complicated the ability to readily achieve the target 1:1 Irinotecan/floxuridine ratio inside the formulation. As a result, a procedure for the simultaneous encapsulation of Irinotecan and floxuridine was developed. This co-encapsulation method has the advantage over sequential loading in that extrusion can be performed in the absence of chemotherapeutic agents and the drug/drug ratios in the final formulation can be more precisely controlled.
Celine Gongora - One of the best experts on this subject based on the ideXlab platform.
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abstract 975 sorafenib overcomes Irinotecan resistance in colorectal cancer by inhibiting the abcg2 drug efflux pump
Cancer Research, 2013Co-Authors: Thibault Mazard, Maguy Del Rio, Annick Causse, Joelle Simony, Wilhem Leconet, Marta Jarlier, Pierre Martineau, Marc Ychou, Bruno Robert, Celine GongoraAbstract:Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Background: Despite recent advances in the treatment of colorectal cancer, tumor resistance is a frequent cause of chemotherapy failure. Thus, new treatment options are needed to improve survival of patients with Irinotecan-refractory colorectal cancers, particularly those bearing KRAS mutations that preclude the use of anti-EGFR therapies. In this study, we investigated whether sorafenib could reverse Irinotecan resistance, thereby enhancing the therapeutic efficacy of routinely used Irinotecan-based chemotherapy. Materials and methods: We used both in vitro (the HCT116, SW48, SW620 and HT29 colon adenocarcinoma cell lines and four SN-38 resistant HCT-116 and SW48 clones) and in vivo models (nude mice xenografted with SN-38 resistant HCT116 cells) to test the efficacy of sorafenib alone or in combination with Irinotecan, or its active metabolite SN-38. Results: Sorafenib improved the anti-tumoral activity of Irinotecan in vitro, in both parental and SN-38 resistant colon adenocarcinoma cell lines independently of their KRAS status, as well as in vivo, in xenografted mice. By inhibiting the drug-efflux pump ABCG2, sorafenib favors Irinotecan intracellular accumulation and enhances its toxicity. Conclusion: Our results show that sorafenib can suppress resistance to Irinotecan and suggest that sorafenib could be used to overcome resistance to Irinotecan-based chemotherapies in colorectal cancer, particularly in KRAS mutated tumors. Citation Format: Thibault Mazard, Annick Causse, Joelle Simony, Wilhem Leconet, Marta Jarlier, Marc Ychou, Maguy Del Rio, Pierre Martineau, Bruno Robert, Celine Gongora. Sorafenib overcomes Irinotecan resistance in colorectal cancer by inhibiting the ABCG2 drug-efflux pump. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 975. doi:10.1158/1538-7445.AM2013-975
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abstract 1902 sorafenib overcome Irinotecan resistance in colorectal cancer
Cancer Research, 2012Co-Authors: Thibault Mazard, Maguy Del Rio, Annick Causse, Wilhem Leconet, Eric Assenat, Pierre Martineau, Marc Ychou, Bruno Robert, Celine GongoraAbstract:Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Despite recent advances in the treatment of colon cancer, tumor resistance is a frequent cause of chemotherapy failure. In the last decade, several studies have shown that cetuximab, an anti-EGFR monoclonal antibody, can overcome acquired resistance to Irinotecan chemotherapy, but only in KRAS non mutant tumors. Thus, new treatment options are needed to improve survival in patients with Irinotecan refractory and KRAS mutated colorectal cancer. In this study, we examined if treatment with sorafenib, a potent inhibitor of Raf kinase and VEGF receptor, could reverse the resistant phenotype in tumor, thereby enhancing the therapeutic efficacy of currently used Irinotecan treatment. We used both in vitro and in vivo models to test the efficacy of sorafenib either as a single agent or in combination with Irinotecan. We have first tested these different combinations on seven colorectal cancer cell lines displaying different molecular characteristics (mutated or not for KRAS, BRAF, p53 and PIK3CA). We have shown that sorafenib, as a single agent, showed antitumor properties and the effects were more pronounced when it was used in combination with the active metabolite of Irinotecan, SN38. Then we have tested these treatments on SN38-resistant clones derived from the colon adenocarcinoma HCT-116 (KRAS mut) and SW48 (KRAS WT) cell lines, that show various levels (6 to 60 fold) of resistance to SN-38 as compared to the corresponding parental cells. Sorafenib has improved the anti-tumoral activity of SN-38 on all the SN38 resistant clones in vitro. Moreover, sorafenib sensitized tumor cells derived from both SN38-sensitive and -resistant HCT116 cells to Irinotecan treatment in xenograft models. Signalling pathways involved in this effect have been identified on xenografts using the proteome profiler array. Altogether, our results show for the first time that sorafenib can inhibit resistance to Irinotecan and suggest that sorafenib could be used to overcome resistance to Irinotecan-based chemotherapies in colorectal cancer, particularly in KRAS mutated tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1902. doi:1538-7445.AM2012-1902
Ajit Bharti - One of the best experts on this subject based on the ideXlab platform.
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ctdsp1 inhibitor rabeprazole regulates dna pkcs dependent topoisomerase i degradation and Irinotecan drug resistance in colorectal cancer
PLOS ONE, 2020Co-Authors: H Matsuoka, Koji Ando, Emma J Swayze, Elizabeth C Unan, Joseph Mathew, Yasuo Tsuda, Yuichiro Nakashima, Hiroshi Saeki, Eiji Oki, Ajit BhartiAbstract:Irinotecan specifically targets topoisomerase I (topoI), and is used to treat various solid tumors, but only 13-32% of patients respond to the therapy. Now, it is understood that the rapid rate of topoI degradation in response to Irinotecan causes Irinotecan resistance. We have published that the deregulated DNA-PKcs kinase cascade ensures rapid degradation of topoI and is at the core of the drug resistance mechanism of topoI inhibitors, including Irinotecan. We also identified CTD small phosphatase 1 (CTDSP1) (a nuclear phosphatase) as a primary upstream regulator of DNA-PKcs in response to topoI inhibitors. Previous reports showed that rabeprazole, a proton pump inhibitor (PPI) inhibits CTDSP1 activity. The purpose of this study was to confirm the effects of rabeprazole on CTDSP1 activity and its impact on Irinotecan-based therapy in colon cancer. Using differentially expressing CTDSP1 cells, we demonstrated that CTDSP1 contributes to the Irinotecan sensitivity by preventing topoI degradation. Retrospective analysis of patients receiving Irinotecan with or without rabeprazole has shown the effects of CTDSP1 on Irinotecan response. These results indicate that CTDSP1 promotes sensitivity to Irinotecan and rabeprazole prevents this effect, resulting in drug resistance. To ensure the best chance at effective treatment, rabeprazole may not be a suitable PPI for cancer patients treated with Irinotecan.
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ctdsp1 inhibitor rabeprazole regulates dna pkcs dependent topoisomerase i degradation and Irinotecan drug resistance in colorectal cancer
bioRxiv, 2020Co-Authors: H Matsuoka, Koji Ando, Emma J Swayze, Elizabeth C Unan, Joseph Mathew, Yasuo Tsuda, Yuichiro Nakashima, Hiroshi Saeki, Eiji Oki, Ajit BhartiAbstract:Irinotecan specifically targets topoisomerase I (topoI), and is used to treat various solid tumors, but only 13-32% of patients respond to the therapy. Now, it is understood that the rapid rate of topoI degradation in response to Irinotecan causes Irinotecan resistance. We have published that the deregulated DNA-PKcs kinase cascade ensures rapid degradation of topoI and is at the core of the drug resistance mechanism of topoI inhibitors, including Irinotecan. We also identified CTD small phosphatase 1 (CTDSP1) (a nuclear phosphatase) as a primary upstream regulator of DNA-PKcs in response to topoI inhibitors. Previous reports showed that rabeprazole, a proton pump inhibitor (PPI) inhibits CTDSP1 activity. The purpose of this study was to confirm the effects of rabeprazole on CTDSP1 activity and its impact on colon cancer. Using HCT116?and HT29, with high and low CTDSP1 expression respectively and a retrospective analysis of patients receiving Irinotecan with or without rabeprazole have indicated the effect of CTDSP1?in Irinotecan response. These results indicate that CTDSP1 promotes sensitivity to Irinotecan and rabeprazole prevents this effect, resulting in drug resistance. To ensure the best chance at effective treatment, rabeprazole may not be a suitable PPI for cancer patients treated with Irinotecan.
Lawrence D Mayer - One of the best experts on this subject based on the ideXlab platform.
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role of copper gluconate triethanolamine in Irinotecan encapsulation inside the liposomes
International Journal of Pharmaceutics, 2007Co-Authors: Awa Dicko, Paul Tardi, Lawrence D MayerAbstract:A novel method for encapsulating Irinotecan into liposomes containing copper gluconate buffered to pH 7.0 with triethanolamine (TEA) has recently been developed. In the present study, the mechanism dictating drug encapsulation and retention inside those liposomes was investigated. Spectroscopic analyses revealed that Irinotecan interacted with copper gluconate/TEA in solution. Fourier transformed infrared (FT-IR) spectroscopy indicated a strengthening of the hydrogen bonds involving the hydroxyl groups when solutions of Irinotecan and copper gluconate/TEA are mixed at a 1:1 molar ratio. The intensity of the circular dichroism (CD) signal of copper gluconate/TEA increased in the presence of equimolar amounts of Irinotecan. The addition of Irinotecan to liposomes containing copper gluconate/TEA at 50 °C induced a shift of the absorption bands from 370 nm to 378 nm as well as a 60% quenching of the drug fluorescence at 440 nm suggesting the occurrence of Irinotecan self association. Irinotecan encapsulation was found to be kinetically and stoichiometrically correlated with the release of TEA from the liposomes. The results suggested that the encapsulation of Irinotecan was mediated by TEA in association with copper gluconate, leading to a final drug complex that is retained inside the liposomes. A neutral antiport exchange loading mechanism between Irinotecan and TEA is proposed.
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role of copper gluconate triethanolamine in Irinotecan encapsulation inside the liposomes
International Journal of Pharmaceutics, 2007Co-Authors: Awa Dicko, Paul Tardi, Lawrence D MayerAbstract:A novel method for encapsulating Irinotecan into liposomes containing copper gluconate buffered to pH 7.0 with triethanolamine (TEA) has recently been developed. In the present study, the mechanism dictating drug encapsulation and retention inside those liposomes was investigated. Spectroscopic analyses revealed that Irinotecan interacted with copper gluconate/TEA in solution. Fourier transformed infrared (FT-IR) spectroscopy indicated a strengthening of the hydrogen bonds involving the hydroxyl groups when solutions of Irinotecan and copper gluconate/TEA are mixed at a 1:1 molar ratio. The intensity of the circular dichroism (CD) signal of copper gluconate/TEA increased in the presence of equimolar amounts of Irinotecan. The addition of Irinotecan to liposomes containing copper gluconate/TEA at 50 °C induced a shift of the absorption bands from 370 nm to 378 nm as well as a 60% quenching of the drug fluorescence at 440 nm suggesting the occurrence of Irinotecan self association. Irinotecan encapsulation was found to be kinetically and stoichiometrically correlated with the release of TEA from the liposomes. The results suggested that the encapsulation of Irinotecan was mediated by TEA in association with copper gluconate, leading to a final drug complex that is retained inside the liposomes. A neutral antiport exchange loading mechanism between Irinotecan and TEA is proposed.
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role of copper gluconate triethanolamine in Irinotecan encapsulation inside the liposomes
International Journal of Pharmaceutics, 2007Co-Authors: Awa Dicko, Paul Tardi, Xiaowei Xie, Lawrence D MayerAbstract:A novel method for encapsulating Irinotecan into liposomes containing copper gluconate buffered to pH 7.0 with triethanolamine (TEA) has recently been developed. In the present study, the mechanism dictating drug encapsulation and retention inside those liposomes was investigated. Spectroscopic analyses revealed that Irinotecan interacted with copper gluconate/TEA in solution. Fourier transformed infrared (FT-IR) spectroscopy indicated a strengthening of the hydrogen bonds involving the hydroxyl groups when solutions of Irinotecan and copper gluconate/TEA are mixed at a 1:1 molar ratio. The intensity of the circular dichroism (CD) signal of copper gluconate/TEA increased in the presence of equimolar amounts of Irinotecan. The addition of Irinotecan to liposomes containing copper gluconate/TEA at 50 degrees C induced a shift of the absorption bands from 370 nm to 378 nm as well as a 60% quenching of the drug fluorescence at 440 nm suggesting the occurrence of Irinotecan self association. Irinotecan encapsulation was found to be kinetically and stoichiometrically correlated with the release of TEA from the liposomes. The results suggested that the encapsulation of Irinotecan was mediated by TEA in association with copper gluconate, leading to a final drug complex that is retained inside the liposomes. A neutral antiport exchange loading mechanism between Irinotecan and TEA is proposed.
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Coencapsulation of Irinotecan and floxuridine into low cholesterol-containing liposomes that coordinate drug release in vivo.
Biochimica et Biophysica Acta, 2006Co-Authors: Paul Tardi, Ryan C. Gallagher, Sharon Johnstone, Natashia Harasym, Murray S. Webb, Marcel B. Bally, Lawrence D MayerAbstract:A liposomal delivery system that coordinates the release of Irinotecan and floxuridine in vivo has been developed. The encapsulation of floxuridine was achieved through passive entrapment while Irinotecan was actively loaded using a novel copper gluconate/triethanolamine based procedure. Coordinating the release rates of both drugs was achieved by altering the cholesterol content of distearoylphosphatidylcholine (DSPC)/distearoylphosphatidylglycerol (DSPG) based formulations. The liposomal retention of floxuridine in plasma after intravenous injection was dramatically improved by decreasing the cholesterol content of the formulation below 20 mol%. In the case of Irinotecan, the opposite trend was observed where increasing cholesterol content enhanced drug retention. Liposomes composed of DSPC/DSPG/Chol (7:2:1, mole ratio) containing co-encapsulated Irinotecan and floxuridine at a 1:1 molar ratio exhibited matched leakage rates for the two agents so that the 1:1 ratio was maintained after intravenous administration to mice. The encapsulation of Irinotecan was optimal when copper gluconate/triethanolamine (pH 7.4) was used as the intraliposomal buffer. The efficiency of Irinotecan loading was approximately 80% with a starting drug to lipid molar ratio of 0.1/1. Leakage of floxuridine from the liposomes during Irinotecan loading at 50 °C complicated the ability to readily achieve the target 1:1 Irinotecan/floxuridine ratio inside the formulation. As a result, a procedure for the simultaneous encapsulation of Irinotecan and floxuridine was developed. This co-encapsulation method has the advantage over sequential loading in that extrusion can be performed in the absence of chemotherapeutic agents and the drug/drug ratios in the final formulation can be more precisely controlled.
Dawn Waterhouse - One of the best experts on this subject based on the ideXlab platform.
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the role of the transition metal copper and the ionophore a23187 in the development of irinophore c
Pharmaceutical Research, 2011Co-Authors: Nilesh Patankar, Marcel B. Bally, Euan Ramsay, Malathi Anantha, Dawn WaterhouseAbstract:Purpose A liposomal Irinotecan formulation referred to as Irinophore C relies on the ability of copper to complex Irinotecan within the liposome. It is currently being evaluated for critical drug-loading parameters. Studies presented here were designed to determine the optimum copper concentration required for the effective encapsulation and retention of Irinotecan into liposomes.
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a novel liposomal Irinotecan formulation with significant anti tumour activity use of the divalent cation ionophore a23187 and copper containing liposomes to improve drug retention
European Journal of Pharmaceutics and Biopharmaceutics, 2008Co-Authors: Euan Ramsay, Murray S. Webb, Marcel B. Bally, Jehan Alnajim, Malathi Anantha, Jason Zastre, Dawn WaterhouseAbstract:We determined whether the method used to encapsulate Irinotecan into 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/Chol; 55:45 mol%) liposomes influenced: (i) Irinotecan release rate and (ii) therapeutic efficacy. DSPC/Chol (55:45 mol%) liposomes were prepared with: (i) unbuffered CuSO4; (ii) buffered (pH 7.5) CuSO4; (iii) unbuffered MnSO4 and the ionophore A23187 (exchanges internal metal2+ with external 2H+ to establish and maintain a transmembrane pH gradient); and (iv) unbuffered CuSO4 and ionophore A23187. All formulations exhibited >98% Irinotecan encapsulation (0.2 drug-to-lipid molar ratio; 10 min incubation at 50 °C). Following a single intravenous injection (100 mg/kg Irinotecan) into Balb/c mice, the unbuffered CuSO4 plus A23187 formulation mediated a half-life of Irinotecan release of 44.4 h; a 4-fold increase compared to the other liposome formulations. This surprising observation demonstrated that the CuSO4 plus A23187 formulation enhanced Irinotecan retention compared to the MnSO4 plus A23187 formulation, indicating the importance of the divalent metal. A single dose of the CuSO4 plus A23187 formulation (50 mg/kg Irinotecan) mediated an 18-fold increase in median T − C (the difference in days for treated and control subcutaneous human LS 180 adenocarcinoma xenografts to increase their initial volume by 400%) when compared to a comparable dose of Camptosar®. Improved Irinotecan retention was associated with increased therapeutic activity.
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a novel liposomal Irinotecan formulation with significant anti tumour activity use of the divalent cation ionophore a23187 and copper containing liposomes to improve drug retention
European Journal of Pharmaceutics and Biopharmaceutics, 2008Co-Authors: Euan Ramsay, Murray S. Webb, Marcel B. Bally, Jehan Alnajim, Malathi Anantha, Jason Zastre, Dawn Waterhouse, Hong YanAbstract:We determined whether the method used to encapsulate Irinotecan into 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/Chol; 55:45 mol%) liposomes influenced: (i) Irinotecan release rate and (ii) therapeutic efficacy. DSPC/Chol (55:45 mol%) liposomes were prepared with: (i) unbuffered CuSO4; (ii) buffered (pH 7.5) CuSO4; (iii) unbuffered MnSO4 and the ionophore A23187 (exchanges internal metal2+ with external 2H+ to establish and maintain a transmembrane pH gradient); and (iv) unbuffered CuSO4 and ionophore A23187. All formulations exhibited >98% Irinotecan encapsulation (0.2 drug-to-lipid molar ratio; 10 min incubation at 50 degrees C). Following a single intravenous injection (100mg/kg Irinotecan) into Balb/c mice, the unbuffered CuSO4 plus A23187 formulation mediated a half-life of Irinotecan release of 44.4h; a >or=4-fold increase compared to the other liposome formulations. This surprising observation demonstrated that the CuSO4 plus A23187 formulation enhanced Irinotecan retention compared to the MnSO4 plus A23187 formulation, indicating the importance of the divalent metal. A single dose of the CuSO4 plus A23187 formulation (50mg/kg Irinotecan) mediated an 18-fold increase in median T-C (the difference in days for treated and control subcutaneous human LS 180 adenocarcinoma xenografts to increase their initial volume by 400%) when compared to a comparable dose of Camptosar. Improved Irinotecan retention was associated with increased therapeutic activity.
