Delivery Of SN-38 Research Articles

Preparation of pegylated nano-liposomal formulation containing SN-38: In vitro characterization and in vivo biodistribution in mice

7-Ethyl-10-hydroxy-camptothecin (SN-38), a metabolite of irinotecan x HCl, is poorly soluble in aqueous solutions and practically insoluble in most physiologically compatible and pharmaceutically acceptable solvents. Formulation of SN-38 in concentrated pharmaceutical delivery systems for parenteral administration is thus very difficult. Due to their biocompatibility and low toxicity, liposomes were considered for the delivery of SN-38. In this study, pegylated liposomes with distearoylphosphatidylcholine, distearoylphosphatidylethanolamine containing SN-38 were prepared and their characteristics, such as particle size, encapsulation efficiency, in vitro drug release and biodistribution, were investigated. The particle size of liposomes was in the range of 150--200 nm. The encapsulation efficiency and in vitro release rate of pegylated liposomes was higher than those of non-pegylated liposomes. As expected, the distribution of pegylated liposomes in body organs such as liver, kidney, spleen and lung was considerably lower than that of non-pegylated liposomes. Also, their blood concentration was at least 50 % higher than that of non-pegylated liposomes.

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Potential Oral Delivery of 7-Ethyl-10-Hydroxy-Camptothecin (SN-38) using Poly(amidoamine) Dendrimers

To investigate potential application of poly(amidoamine) (PAMAM) dendrimers for improving the delivery of SN-38. Complexes of SN-38 with generation 4 amine terminated PAMAM dendrimers were synthesized with varying amounts of drug. Stability of the complexes as well as influence of complexation on permeability across and cellular uptake by Caco-2 cells was evaluated. The complexes were stable at pH 7.4 and drug was released at pH 5. A tenfold increase in permeability and more than hundredfold increase in cellular uptake of the complexes with respect to free SN-38 was observed. Studies suggest that complexation with PAMAM dendrimers has the potential to improve the oral bioavailability of SN-38.

Novel Delivery of SN38 Markedly Inhibits Tumor Growth in Xenografts, Including a Camptothecin-11–Refractory Model

Clinical development of SN38, the active metabolite of camptothecin-11 (CPT-11), has been hampered due to its poor solubility. We have developed a novel polymer-drug conjugate, EZN-2208, made by linking SN38 with a multiarm polyethylene glycol via a glycine linker. The in vitro cytotoxicity of EZN-2208 was tested using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. The therapeutic efficacy of EZN-2208 was evaluated in various xenografts, including an in vivo-selected CPT-11-refractory model. Tumor and blood concentration of EZN-2208, CPT-11, and SN38 was determined by high-performance liquid chromatography. In vitro, EZN-2208 was 10- to 245-fold more potent than CPT-11 in a panel of human tumor cell lines. In xenograft models of MX-1 breast, MiaPaCa-2 pancreatic, or HT-29 colon carcinoma, treatment with either a single dose or multiple injections of EZN-2208 was more efficacious (and in some cases produced tumor eradication for >16 weeks) compared with CPT-11 at their respective maximum tolerated doses or corresponding dose levels (P < 0.01). Most interestingly, EZN-2208 showed marked antitumor activity in animals that developed resistance to an 8-day course of CPT-11 treatment, as well as outperformed CPT-11 as second-round therapy in mice initially sensitive to CPT-11. EZN-2208 had prolonged circulation in the blood compared with CPT-11, resulting in high tumor exposure. This resulted in higher and longer-lasting tumor exposure of free SN38 in mice given EZN-2208 compared with those given CPT-11. Preclinical data suggest that EZN-2208 may be a promising anticancer agent in a wide variety of clinical settings, including tumors refractory to CPT-11 treatment.