Studies On Epirubicin Liposomes

Epirubicin (EPI), the 4’ epimere of doxorubicin (DOX), synthesized by an Italian scientist Arcamone via a semisynthesis method, is a member of the anthracycline family of antibiotics, which has shown significant anticancer activity against a variety of cancer, such as acute leukemia, malignant lymphoma, breast cancer, bronchiogenic cancer, ovarian cancer, and so on. However, in chemotherapy, EPI produce early transient electrocardiographic changes and a progressive cardiomyopathy. This cardiomyopathy is severe and leads to progressive congestive heart failure that is dose-dependent, cumulative and irreversible. A number of investigations have shown that DOX entrapped in liposomes reduces non-specific toxicity and maintains or enhances anticancer effects in animal systems. Considering that EPI has a somewhat similar chemical structure with its parent compound, it is therefore thought that liposomal entrapment of EPI could enhance its activity and reduce its toxicity.HPLC analysis method for EPI vitro sample was established and testified to be valid. The solubility and oil-water partition coefficient of EPI in solution with different pH value at 25/37℃was determined. The solubility and coefficient was showed pH-dependent. With increasing of pH, the solubility dropped and the coefficient rose.Three liposome formulations were prepared and investigated: HSPC: Chol (L-EPI, 5:4, molar ratio), HSPC: Chol: DSPG (D-EPI, 5:4:1, molar ratio) and HSPC: Chol: DSPG: 2000PEG-DSPE (S-EPI, 5:4:1:0.3, molar ratio), in terms of physico-chemical property, in vitro macrophage uptake, pharmacokinetics, biodistribution and in vito toxicity. The threee kinds of small unilamellar liposomes were prepared by the modified thin-film hydration method with extrusion through polycarbonate filters, epirubicin was remote loaded into liposomes by the transmembrane ammonium sulfate gradient method. Based on the results of single fator experiments, with the evaluation index of encapsulation efficiency and drug loading amount, EPI liposomes were optimized by employing a three-factor, three-level Box-Behnken experimental design. To improve the storage stability, the liposomes were freeze dried and the cryoprotectants were screened and sucrose was used as cryoprotectant.Studies of the physico-chemical property of liposomes showed that the liposomes were round or oval shaped with a Nicomp particle size distribution of 100 nm. The entrapment efficiency of EPI liposomes was 95.1%. Macrophages were used to evaluate in vitro the cellar uptake of epirubicin-loaded liposomes. The following decreasing uptake amount order was observed: L-EPI>D-EPI>S-EPI. D-EPI showed a relatively low level of uptake, probably due to the steric hindrance provided by glycerol head group on DSPG protecting from the direct recognization by cell membrane receptors. With the presence of serum, the uptake for all the liposome formulation was increased for the activation of complement system.In pharmacokinetics study, S-EPI showed significant prolonged circulating time and reduced clearance. The following increasing area under the concentration vs time curve (AUC) order was observed between the various liposome formulations: L-EPKD-EPKS-EPI. The biodistribution study indicated that S-EPI decreased the drug disposition in liver, spleen, lung and heart, increased in kidney with respect to the other liposomes. The encouraging property of S-EPI in terms of prolonging circulating time and reduce heart toxicity might describe a promising perspective towards clinical application, and all the results would support further research into liposome-base drug carrier.To assess the toxicity after receiving EPI liposomes, systemic and cardiac toxicity experiment were conducted. The results showed that liposomal encapsulation could significantly improve the severe cardiotoxicity arising from simultaneous administration of EPI. Liposomal EPI would be a promising anticancer formulation with lower cardiotoxicity for clinical application.