Spla2 hydrolysable liposomes with improved storage stability

Optimization of Storage Stability of sPLA2 Hydrolysable Liposomes

[0159]Abstract

[0160]It has been observed that upon storage at 2-8° C. LiPlaCis (liposomal cisplatin) may have up to 30% leakage during the first couple of months. Leakage is most extensive during the first two months, and beyond this period only minor leakage occurs.

[0161]A factorial design was set up to test stability of LiPlacis at 2-8° C. Formulations were prepared with varying interior buffer composition, and homogenized at different pressures according to composite face design. 3 factors were tested at 3 levels:[0162]Interior NaCl concentration (0.9, 1.4, and 1.9%)[0163]Interior Sucrose concentration (0.5, and 10%)[0164]Homogenization pressure used during preparation (5000, 12500, and 20000 KPa).

[0165]Leakage from formulation was demonstrated to be influenced by all parameters tested. Increasing the sucrose and NaCl concentration on liposome interior and having low homogenization pressure during liposome preparation

[0199]Liposomal cisplatin formulations were prepared by film hydration followed by extrusion. Hydration solution was prepared with varying osmolyte concentrations. After extrusion the liposomes were dialyzed in different media. The formulations prepared had different osmotic gradient (difference in osmolarity between interior and exterior) as outlined in table 3. For comparison liposomal formulation of other chemotherapeutics were prepared as outlined in table 4. All Formulations were placed in refrigerator at 2-8° C., and samples were taken continually during storage.

[0200]Preparation of Liposomal Formulations

[0201]Phospholipids (DSPC / DSPG / DSPE-PEG2000, 70:25:5 mol %) were dissolved in 9:1 (v / v) chloroform / methanol. The solvent of the dissolved lipid mixtures were then evaporated in a 50° C. hot water bath until visual dryness, under a stream of nitrogen gas. The samples were further dried under vacuum overnight.

[0202]Hydration liquids (varying Salt and sucrose concentrations