Liposomes useful for drug delivery
The present invention provides liposome compositions containing substituted ammonium and/or polyanion, and optionally with a desired therapeutic or imaging entity. The present invention also provide methods of making the liposome compositions provided by the present invention.
1. An irinotecan liposome composition comprising irinotecan and a sulfated sugar encapsulated in a lipid vesicle, wherein the composition is obtainable by a process comprising the steps of:
(a) forming the lipid vesicle encapsulating the sulfated sugar and one or more substituted ammonium compounds selected from the group consisting of diethylammonium and triethylammonium in a lipid composition comprising one or more lipid components forming the lipid vesicle;
(b) contacting the lipid vesicle with irinotecan at a temperature above the phase transition temperature of the lipid vesicle, to load at least 85% of the irinotecan into the lipid vesicle; wherein at least about 70% of the irinotecan remains encapsulated in the lipid vesicle after 8 hours in the blood of a CD-1 mouse.
2. The irinotecan liposome composition of claim 1 , wherein the sulfated sugar has a pKa of 3 or less.
3. The irinotecan liposome composition of claim 1 , wherein the lipid vesicle comprises DSPC and cholesterol in a 3:2 molar ratio.
4. The irinotecan liposome composition of claim 1 , wherein the sulfated sugar is selected from the group consisting of sucrose hexasulfate, sucrose heptasulfate, and sucrose octasulfate.
5. The irinotecan liposome composition of claim 4 , wherein the sulfated sugar is sucrose octasulfate.
6. An irinotecan liposome composition comprising irinotecan and a sulfated sugar selected from the group consisting of sucrose hexasulfate, sucrose heptasulfate, and sucrose octasulfate encapsulated in a lipid vesicle, wherein the composition is obtained by a process comprising the steps of:
(a) forming the lipid vesicle encapsulating the sulfated sugar and one or more substituted ammonium compounds selected from the group consisting of: diethylammonium and triethylammonium in a lipid composition comprising one or more lipid components forming the lipid vesicle;
(b) contacting the lipid vesicle with irinotecan at a temperature above the phase transition temperature of the lipid vesicle, to load at least 85% of the irinotecan into the lipid vesicle.
7. The irinotecan liposome composition of claim 6 , wherein the sulfated sugar has a pKa of 3 or less.
8. The irinotecan liposome composition of claim 6 , wherein the lipid vesicle comprises DSPC and cholesterol in a 3:2 molar ratio.
9. The irinotecan liposome composition of claim 8 , wherein at least about 70% of the irinotecan remains encapsulated in the lipid vesicle after 8 hours in the blood of a CD-1 mouse.
10. The irinotecan liposome composition of claim 9 , wherein the lipid vesicle comprises DSPC and cholesterol in a 3:2 molar ratio and the sulfated sugar has a pKa of 3 or less.
11. An irinotecan liposome composition comprising liposomes encapsulating irinotecan and a sulfated sugar, wherein at least about 70% of the irinotecan remains encapsulated in the lipid vesicles after 8 hours in the blood of a CD-1 mouse.
12. The irinotecan liposome composition of claim 11 , wherein the amount of encapsulated irinotecan in the lipid vesicles is determined by a method comprising the steps of:
a) administering a radioactive labeled version of the irinotecan liposome composition to six-week-old female CD-1 mice by tail vein injection at a dose of 10 mg/kg (0.2 mg CPT-11/mouse);
b) anesthetizing and exsanguinating the mice eight hours later;
c) collecting the blood from the mice in step (b) into heparinized syringes (10-20 μl of 1000 U/mL heparin USP) and transferring into weighed tubes containing 0.4 mL of the phosphate-buffered physiological saline solution (PBS) containing 0.04% EDTA (Gibco BRL) and keeping on ice;
d) weighing the tubes to determine weights of the blood samples;
e) separating the blood cells by centrifugation at 9,000 g for 5 minutes, and saving supernatants containing PBS-diluted plasma for drug and liposome lipid assays;
f) quantifying irinotecan in the samples by the fluorometric assay, whereby liposome lipid is quantified by quenching-corrected radioactivity scintillation counting, using liposome and phospholipid-radioactivity standards counted in parallel with the plasma samples; and
g) calculating the percent of the drug remaining encapsulated by dividing the drug/radioactivity ratio in the plasma samples by the drug/radioactivity ratio of the injected liposomes, wherein the percent of injected lipid dose (% I.D.) remaining in the circulation was calculated assuming 100% of the injected bolus entered the circulation.
13. The irinotecan liposome composition of claim 11 , wherein the sulfated sugar has a pKa of 3 or less.
14. The irinotecan liposome composition of claim 13 , wherein the liposomes comprise DSPC and cholesterol in a 3:2 molar ratio.
15. A pharmaceutical composition comprising liposomes encapsulating irinotecan and sucrose hexasulfate.
16. The pharmaceutical composition of claim 15 , wherein the amount of encapsulated irinotecan in the lipid vesicles is determined by a method comprising the steps of:
a) administering a radioactive labeled version of the irinotecan liposome composition to six-week-old female CD-1 mice by tail vein injection at a dose of 10 mg/kg (0.2 mg CPT-11/mouse);
b) anesthetizing and exsanguinating the mice eight hours later;
c) collecting the blood from the mice in step (b) into heparinized syringes (10-20 μl of 1000 U/mL heparin USP) and transferring into weighed tubes containing 0.4 mL of the phosphate-buffered physiological saline solution (PBS) containing 0.04% EDTA (Gibco BRL) and keeping on ice;
d) weighing the tubes to determine weights of the blood samples;
e) separating the blood cells by centrifugation at 9,000 g for 5 minutes, and saving supernatants containing PBS-diluted plasma for drug and liposome lipid assays;
f) quantifying irinotecan in the samples by the fluorometric assay, whereby liposome lipid is quantified by quenching-corrected radioactivity scintillation counting, using liposome and phospholipid-radioactivity standards counted in parallel with the plasma samples; and
g) calculating the percent of the drug remaining encapsulated by dividing the drug/radioactivity ratio in the plasma samples by the drug/radioactivity ratio of the injected liposomes, wherein the percent of injected lipid dose (% I.D.) remaining in the circulation was calculated assuming 100% of the injected bolus entered the circulation.
17. A pharmaceutical composition comprising liposomes comprising DSPC and cholesterol in a 3:2 molar ratio, encapsulating irinotecan and a sulfated sugar having a pKa of 3 or less, wherein at least about 70% of the irinotecan remains encapsulated in the lipid vesicles after 8 hours in the blood of a CD-1 mouse.