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Kahalalide F is a novel antitumor agent isolated from the marine mollusk Elysia rufescens; it has shown highly selective in vitro activity against androgen-independent prostate tumors. The purpose of this study was to develop a stable parenteral formulation of kahalalide F to be used in early clinical trials. Solubility and stability of kahalalide F were studied as a function of polysorbate 80 (0.1%-0.5% w/v) and citric acid monohydrate (15-15 mM) concentrations using an experimental design approach. Stabilities of kahalalide F lyophilized products containing crystalline (mannitol) or amorphous (sucrose) bulking agents were studied at +5 degrees C and +30 degrees C +/- 60% relative humidity (RH) in the dark. Lyophilized products were characterized by infrared (IR) spectroscopy and differential scanning calorimetry (DSC). Recovery studies after reconstitution of kahalalide F lyophilized product and further dilution in infusion fluid were carried out to select an optimal reconstitution vehicle. It was found that a combination of polysorbate 80 and citric acid monohydrate is necessary to solubilize kahalalide F. Lyophilized products were considerably less stable with increasing polysorbate 80 and citric acid monohydrate concentrations, with polysorbate 80 being the major effector. A combination of 0.1% w/v polysorbate 80 and 5 mM citric acid monohydrate was selected for further investigation. Lyophilized products containing sucrose as a hulking agent were more stable compared to the products containing mannitol. The glass transition temperature of the sucrose-based product was determined to be + 46 degrees C. The amorphous state of the product was confirmed by IR analysis. A solution composed of Cremophor EL, ethanol, and water for injection (5%/5%/90% v/v/v CEW, kept kahalalide F in solution after reconstitution andfurther dilution with 0.9% w/v sodium chloride (normal saline) to 1.5 microg/m. A stable lyophilized formulation was presented containing 100 microg of kahalalide F, 100 mg sucrose, 2.1 mg citric acid monohydrate, and 2mg polysorbate 80 to be reconstituted with a vehicle composed of 5%/5%/90% v/v/v CEW and to be diluted further using normal saline.

The aim of this study was to gain insight into the relation between the physical characteristics of particles formed by a plasmid and a synthetic cationic polymer (poly(2-dimethylamino)ethyl methacrylate, PDMAEMA) and their transfection efficiency.The PDMAEMA-plasmid particles were characterized by dynamic light scattering (size) and electrophoretic mobility measurements (charge). The transfection efficiency was evaluated in cell culture (COS-7 cells) using a pCMV-lacZ plasmid coding for beta-galactosidase as a reporter gene.It was shown that the optimal transfection efficiency was found at a PDMAEMA-plasmid ratio of 3 (w/w), yielding stable and rather homogeneous particles (diameter 0.15 micron) with a narrow size distribution and a slightly positive charge. Particles prepared at lower weight ratios, showed a reduced transfection efficiency and were unstable in time as demonstrated by DLS measurements. Like other cationic polymers, PDMAEMA is slightly cytotoxic. This activity was partially masked by complexing the polymer with DNA. Interestingly, the transfection efficiency of the particles was not affected by the presence of serum proteins.PDMAEMA is an interesting vector for the design of in vivo and ex vivo gene transfection systems.

The thermal behavior of water in liposome dispersions and in liposome dispersions containing mannitol at subzero temperatures was investigated with differential scanning calorimetry (DSC). The cooling curves from 20 down to -60 degrees C for a liposome dispersion (bilayer composition PL100H/DCP), monitored at cooling rates of 5 and 10 degrees C/min, showed several heat flows related to water crystallization. All lipid-containing dispersions showed water crystallization at temperatures below -40 degrees C. The magnitude of this heat flow strongly depended on the experimental variables. Cooling rate, particle size, lipid concentration, and location and nature of the cryoprotectant all influenced the water crystallization behavior as shown in the DSC cooling curve. Different fractions of water--presumably related to their location in the dispersion--could be distinguished. It is concluded that DSC provides a valuable tool for the detection of changes in the physical state of water in liposome dispersions during freezing/thawing. The insights gained from these DSC studies may make it possible to select--on the basis of rational considerations rather than by trial and error--optimum conditions for the cryopreservation of liposomes containing water-soluble drugs.