| More attention has been paid for development of peptide drugs in recent years. Lots of analogs of regulatory peptides were synthesized as the candidate of new drugs. Gonadotropin releasing hormone (GnRH) analogue (agonists and antagonists), which has been regards as potent drugs for sex hormone dependent diseases , especially for prostate cancer, was one of most important achievement in this field. They are suitable to be designed as sustained-release injectable products for their inactivation in gastrointestinal tract and short half life time.Multivesicular liposmes (MVL) is one of the drug delivery system with high encapsulation efficiency (EE) and sustained-release property, which was considered as a good carrier for water soluble drugs, especially for peptides and proteins. LXT-101, a novel GnRH analogue developed by our institute, was used as a model drug in present study.Firstly,interaction between lipid bilayers and LXT-101 molecules was determined via Zeta potential and fluorescence spectrum analysis. It is possible to prepare MVLs containing LXT-101 (DepoLXT-101) as for weak hydrophobic interaction between LXT-101 and phospholipid molecules. LXT-101 molecules will be adsorbed on interface of lipid-oil and affect the surface charge was neutralizated by which may decrease the stability of w/o/w multiple emulsions.The anionic MVL of LXT-101 (ADepoLXT-101) was obtained via anionic surfactant added in second aqueous phase to increase the surface charge. The EE of ADepoLXT-101 is more than 40% when the ADepoLXT-101 were prepared. In the morphology study,the spherical, smooth, and multivesicular characteristic of DepoLXT-101 particle with size of 8~12.1μm was observed. On the other hand, the cationic MVL of LXT-101 (ADepoLXT-101) was obtained via cationic lipid added in oil aqueous phase to eliminate the electrostastic interaction. The EE of CDepoLXT-101 is more than 40% when the CDepoLXT-101 were prepared. In the morphology study,the spherical, smooth, and multivesicular characteristic of DepoLXT-101 particle with mean size of 10μm was observed.The control of quality of analytical method was also studied. The RP-HPLC was established to determine the content of DepoLXT-101. The mean content of three batches of ADepoLXT-101 and CDepoLXT-101 were 2.5 and 1.95 mg.mL-1 respectively.An evaluation of release rate in vitro from three batches ADepoLXT-101 and CDepoLXT-101 were performed in saline solution at 37℃. For these formulations, most of encapsulated LXT-101 was released in a sustained manner over 7~11days. It can remarkably slow the release rate of drug from depot. The Ritgar-Pepps model was used to fitting the drug release profile. According to mean value of k 0.42, the in vitro release of DepoLXT-101 was mainly decided by Fick's diffusion. The effect of temperature on release of CDepoLXT-101 was also investigated and the results shown that no drug was released at 4℃under sink condition, while there are 40% drug released at 20℃and 70% drug released at 37℃after 7-day. It concluded that the formulation was stable at the 4℃storage condition and not able to be kept at 20℃for a long time.In vivo studies, rats were selected as modal animal to evaluate the pharmacokinetics and injection site injury of LXT-101 formulations. After administration via s.c. of LXT-101-glucose solution, ADepoLXT-101and CDepoLXT-101 with same dose, the MRT of three formulations were 4.6h, 3.7d and 3.4d respectively, AUC were 17152, 37470 and 30972.8h·ng·mL-1,Cmax were 3799.7, 427.0, 671.8ng·mL-1 respectively. LXT-101 from two type mutivesicular liposmes resulted in about 2.2 and 1.8-fold increase in bioavailability and 19.3 and 17.7-fold in MRT compared with the normal solution. The results of injection site injury test suggested that the CDepoLXT-101 had biocompatibility similar with saline injection. Cationic lipid did not increase the injury of injection site in a short term. |
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