Study On Tissue Distribution Of Lyophilized 2-methoxyestradiol Liposome In Rats

2-methoxyestradiol (2-ME) is an orally active, well-tolerated compound that has antiproliferative, antiangiogenic and anti-inflammatory properties. 2-ME attacks tumor cells through multiple mechanisms of action, and modest antitumor activity has been demonstrated across most clinical studies. Due to its poor gastrointestinal absorption, rapid metabolic deactivation and rapid removal from plasma, high oral or intraperitoneal doses of 2-ME were necessary to reduce the growth of tumors. In order to overcome the disadvantages, the intravenous injection formulation of liposomes loaded with 2-methoxyestradiol has been investigated. The aim of the study was to evaluate tissue distribution of this preparation in Sprague-Dawley rats in comparison to 2-ME solution, and demonstrate its tissue targetability by the use of some pharmacokinetic parameters.1. The establishment of analytical method of 2-ME in biological matrixA simple, rapid and accurate HPLC method based on fluorescence detection for the quantitative determination of 2-ME in tissue and plasma samples using letrozole as the internal standard, has been developed and validated. Sample preparation was achieved by liquid-liquid extraction with ethyl acetate. 2-ME was separated on an Agilent Eclipse XDB-C18 column (150 mm×4.6 mm, 5μm) with a mobile phase consisting of potassium dihydrogen phosphate-acetonitrile-triethylamine (55:45:0.3, v/v/v, pH 3.0) at a flow rate of 1.0 ml/min and the excitation wavelength and emission wavelength of the fluorescence detector were set at 285 nm and 325 nm, respectively. There were good linear relationships for 2-ME with the ranges in different tissue and plasma samples. The intra-day and inter-day precision of quality control samples were less than 11.40%. The average recovery of extraction was 82.08%. Biological samples were stable in room temperature or 4℃, and in freezing for 14 days or after three freeze/thaw cycles.2. The study on tissue distribution of 2-ME in ratsThe concentration of 2-ME in different tissues of rats are determined after tail intravenous injection of 2-ME liposome and 2-ME solution by using HPLC described as above. The results are analyzed in order to evaluate the targeting efficiency of the liposome. The research on tissue distribution showed that the liposome can increase the lung targeting efficiency obviously. The overall targeting efficiency (TE^C) of the 2-ME liposome was enhanced from 33.92% to 87.83% in the lung. These results indicated that 2-ME liposome could mainly deliver the drug to the lung and make the drug accumulate in the lung, which changed the disposition behavior in vivo, decreased the toxic and side effects on other tissues3. The Pharmacokinetics study of 2-ME in lung tissue of ratsFollowing a single intravenous administration with 2-ME liposome and 2-ME solution with the dose of 10 mg/kg to rats, the lung samples were collected at different time points after dosing. The concentrations of 2-ME in lung tissue homogenate were determined by HPLC method described as above. Pharmacokinetic parameter calculation and pharmacokinetic model were carried out using the 3p97 Pharmacokinetics software. It was shown that the lung tissue concentration-time data was fit to a single compartment pharmacokinetic model in rats after i.v. administration. Based on the parameters of t_1/2, AUC, MRT and CL, 2-ME liposome contributed to extend internal circulation time and increase targeting.