Study Of Sustained-released VEC-5 PLGA Microspheres

AIDS is an infectious immune system disease caused by HIV virus infection. At present, there is no completely cure method for this disease. However, in the early stage of infection, proper medical treatment can delay disease and dramatically reduce the morbidity and mortality of patients infected by HIV. Highly active antiretroviral therapy(HAART) is the best treatment for HIV infection, but there are also problems such as drug resistance. Thus, the development of new treatments and novel drugs is urgently needed.VEC-5 is a small molecule inhibitor reported in 2013, which can interfere the formation of A3G-Vif-E3 complex. A3 G protein is antiviral host factor for a wide variety of retroviruses, while HIV-1 Vif overcomes the antiviral activity of A3 G by ubiquitinating the protein and preventing its incorporation to HIV-1 virus. The mechanism for the inhibition of HIV-1 replication by VEC-5 is clear, and its cell toxicity is relatively small. VEC-5 is a novel candidate drug with potential application value. But its physicochemical property, the pharmacokinetic parameters and tissue distribution characteristics in vivo, as well as the suitable formulation research and so on, have not been reported.In this study, an HPLC method with fluorescence detection was developed for the determination of VEC-5. The linearity of calibration plots was good(regression coefficients, 0.9999) for all the VEC-5 in the concentration range 0.25-4 μg/ml. The intra-day and inter-day precision expressed as RSD values was always less than 2%, and recoveries were between 98%-102%. Using this method, the solubility of VEC-5 in various solvents was determined. The results showed that VEC-5 is soluble in N-methylpyrrolidone, slightly soluble in dichloromethane, dimethylsulfoxide, acetone and acetonitrile, very slightly soluble in ethanol, tert-butanol and n-octanol, and almost insoluble in water. VEC-5 is highly hydrophobic and gives an octanol-water partition coefficient logP of higher than 4. The above results provide the fundamental information for the subsequent formulation work.In addition, the pharmacokinetic parameters and tissue distribution of VEC-5 in rats were investigated. VEC-5 was rapidly eliminated from the plasma after intravenous injection. Its half-life was about 133 min, mean residence time MRT(0-t) was about 149.59 min. Following the elimination, VEC-5 rapidly distributed into liver, lung, heart, kidney, spleen and other organ tissues. Due to high hydrophobicity, VEC-5 could accumulate in fat and rectum tissues. With the decreasing concentrations in plasma, the accumulated drug can re-release into the blood. As a result, a double-peak phenomenon occurred in the time concentration curve.Based on the physicochemical property and the pharmacokinetic characteristics of VEC-5, the preparation of sustained-released PLGA microspheres loaded with VEC-5 was studied. The VEC-5 PLGA microspheres were prepared using emulsion solvent evaporation technique. The optimized formulation and process parameters are as following: 15 mg/m L of PLGA(50: 50,0.95-1.2 η), oil/water(1% PVA) volume ratio of 1: 5, shear rate of 10000 r/min. The resultant PLGA microspheres displayed an average particle size of 3.35±0.03μm, and gave an encapsulation efficiency of 94.46% ±2.9. The cumulative release in vitro of VEC-5 in 8 weeks was about 70%.