Study On The Glycerol-Skeleton Antitumor Lipid Prodrug Pharmacosomes

Malignant tumor was the most common disease and the frequently encountered disease to threaten human healthy. However, the use of many common clinically relevant chemotherapeutics is often limited due to insufficient delivery to the tumor and dose-limiting systemic toxicities. Therefore, therapeutics that specifically target tumor cells and are nontoxic to normal cells are required. Antitumor targeting prodrug delivery system has become the hot spot of the research.Phospholipase A₂ (PLA₂) has elevated expression in tumor. Glycerolpholipid and derivative could be hydrolyzed at the sn-2 position by PLA₂ in tumor.5-fluorouracil and zidovudine were selected as the model drugs in this paper. Phospholipase A2 (PLA2) sensitive prodrug of antitumor ether lipid prodrug was designed in this paper, and pharmacosomes composed of glycerol-skeleton lipid prodrug were prepared. Characteristics and regularities of prodrug pharmacosomes in vitro and in vivo were determined. The main contents were described in details as follows.1. Synthesis and characteristics of glycerol-skeleton lipid prodrug.A prodrug of glycerol-skeleton lipid prodrug was designed and synthesized, that was 1-octadecyl-2-fluorouracil-N-acetyl-3-zidovudine phosphoryl glycerol (OFZPG). And its structure was identified by 1H NMR, 13C NMR, IR and MS. The critical micelle concentration (CMC) of the prodrug was measured by conductometry, that was 3.2×10^-4 mol/L. The hydrophobic interaction were the key factors when OFZPG self-assemblied in the water. Meanwhile, the formation and characterization of its langmuir monolayers in water were investigated. It showed the prodrug had suitable amphiphilicity.2. Preparation and characteristics of glycerol-skeleton lipid prodrug pharmacosomes.A kind of highly dispersed homogeneous suspension system with high concentration was prepared by tetrahydrofuran (THF) injection method. The shape and size of OFZPG pharmacosomes were evaluated by transmission electron microscope (TEM) and dynamic light scattering instrument. OFZPG pharmacosomes were spheroidal. The mean apparent particle size of OFZPG pharmacosomes were about 75.2 nm . The surface Zeta potential was -30.4 mV. 3. Physical stability of glycerol-skeleton lipid prodrug pharmacosomes.Physical stability was investigated through heating, high pressure, centrifugation (≤10000 rpm) and storing at room temperature. The results indicated that the shape of OFZPG pharmacosomes were almost not changed. However, the content of OFZPG decreased obviously and the size of OFZPG pharmacosomes slightly decreased as for the heating and high pressure. OFZPG pharmacosomes were stable to a great extent under the condition of high speed centrifugation and storing at room temperature.4. Chemical stability of glycerol-skeleton lipid prodrug pharmacosomes.Chemical stability of OFZPG pharmacosomes in the buffer solutions of different pH, plasma of different animals and tissue homogenates of mice were all investigated by HPLC. OFZPG pharmacosomes were hydrolyzed quickly in the buffer solution of pH 2.0 and 9.0, but kept stable for a long period in the neutral and weak acid surrounding with t1/2 more than 693h and 231h, respectively. However, the hydrolysis rate of OFZPG in the PLA2 solution of pH 6.5 and 7.4 were 81.5 and 69.3 h. The hydrolysis of OFZPG in the plasma of animals was different. The hydrolysis rate of OFZPG in the plasma of mice was faster, which was 1.8 h; while, the hydrolysis rate of OFZPG in the plasma of humans and dogs were slower, which were 21.5 h and 28.8 h, respectively. The degradation rate of OFZPG in liver homogenates of mice was very fast, and the t1/2 was 1.5 h.5. Pharmacokinetics and tissue distribution of glycerol-skeleton lipid prodrug pharmacosomes.After single bolus of i.v. administration to mormal Kunming mice, OFZPG pharmacosomes were eliminated quickly from blood circulation to the major tissues, such as liver and lung. It demostrated that the pharmacosomes could target to the macrophage cells-rich tissues. The distributon t_1/2 and the elimination t1/2 were 5.16 min and 105.13 min, respectively.6. Pharmacodynamics of glycerol-skeleton lipid prodrug pharmacosomes.Antitumor activity of OFZPG pharmacosomes was investigated, which demonstrated the IC₅₀ in the three human colon cancer cells (COLO205,HT-29,HCT-116) was 4.6,12.2,12.7μmol/L respectively, and it was better than that of 5-FU. The results indicated that the prodrug could degrade to the active compound efficiently, which could play an important role in pharmacodynamic action.After i.v. administration of Hepatoma (H₂₂) tumor to Kunming mice successively and the evaluation index were the body weight, tumor weight and tumor volume. The results showed that the high dose of OFZPG pharmacosomes (15 mg/kg) had significant inhibition to tumor, and the tumor inhibition ratio was 41.47%, but whose dose was lower than 1/10 (mol/mol) of 5-FU, and which has comparative therapeutic effect to of 5-FU (tumor inhibition ratio : 59.91%).In general, highly dispersed, homogeneous and stable pharmacosomes of 1-octadecyl, 2-fluorouracil-N-acetyl, 3-zidovudine phosphoryl glycerol (OFZPG) were prepared in this paper. A nano-size, ordered structure formed under the action of hydrophobic interaction was proved. OFZPG pharmacosomes were uptaked by monocyte macrophage quickly in mice. OFZPG pharmacosomes played an important role in the antitumor activity.