Vinyl ether lipids with cleavable hydrophlic headgroups
A novel amphiphilic lipid compound having a cleavable, vinyl ether linked hydrophilic headgroup is described. Also described are liposomes containing the vinyl ether lipid compound, which may be triggered to release their contents and/or permeablize or fuse with target lipid membranes. The cleavable vinyl ether linkage allows the hydrophilic headgroup to be dissociated from the hydrophobic tailgroup(s) of the lipid compound to facilitate phase transitions in the lipid bilayer.
1. A vinyl ether lipid compound of the formula:
wherein one of either R 1 or R 2 is a hydrophilic headgroup and the other of R 1 or R 2 is hydrogen, a second hydrophilic headgroup, or a crosslinker joining at least one other molecule of the vinyl ether compound at the R 1 or R 2 position;
R 4 is hydrogen or an electron donating group; and
R 3 is cholesterol, a cholesterol derivative, sphingosine, a sphingosine derivative or a group according to the formula:
wherein each R 5 is independently a hydrophobic group of the formula:
wherein X is O or S; n is an integer from 5 to 32 inclusive; y is an even integer from 2 to 12 inclusive; and y is less than or equal to n.
2. The compound according to claim 1 wherein R 4 is selected from the group consisting of C 1 –C 6 alkoxy, furan, thiophene, methoxyphenyl, dimethoxyphenyl and trimethoxyphenyl.
3. The compound according to claim 1 wherein the hydrophilic headgroup is selected from the group consisting of poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol), poly(ethylenimine), N,N-di(aminoethyl)carbamoyloxyethyl-, choline, monosaccharide, disaccharide, ethanolamine, phosphatidylcholine, phosphatidylethanolamine, cardiolipin, and phosphatidylmonosaccharides and phosphatidyldisaccharides.
4. The compound of claim 3 , wherein the hydrophilic headgroup is poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol) or poly(ethylenimine), N,N-di(aminoethyl)carbamoyloxyethyl-.
5. The compound of claim 3 , wherein the hydrophilic headgroup is poly(ethylene glycol) or C 1 –C 6 alkoxy poly(ethylene glycol) and the poly(ethylene glycol) moiety has an average of 1 to about 300 ethylene glycol units.
6. The compound according to claim 5 wherein the poly(ethylene glycol) moiety has an average of between about 10 and 150 ethylene glycol units.
7. The compound according to claim 1 wherein either R 1 or R 2 is poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol) or poly(ethylenimine) or N,N-di(aminoethyl)carbamoyloxyethyl- and the other of R 1 or R 2 is hydrogen; and R 3 is selected from the group consisting of cholesterol, a cholesterol derivative and a group of the formula:
wherein each R 5 is independently a hydrophobic group of the formula:
wherein X is O; n is an integer from 5 to 32 inclusive; y is an even integer from 2 to 12 inclusive; and y is less than or equal to n.
8. A vinyl ether lipid compound of the formula:
wherein one of either R 1 or R 2 is a hydrophilic headgroup and the other of R 1 or R 2 is hydrogen, a second hydrophilic headgroup, or a crosslinker joining at least one other molecule of the vinyl ether compound at the R 1 or R 2 position;
R 3 is an organic hydrophobic moiety; and
R 4 is selected from the group consisting of C 1 –C 6 alkoxy, furan, thiophene, methoxyphenyl, dimethoxyphenyl and trimethoxyphenyl.
9. The compound according to claim 8 wherein the hydrophilic headgroup is selected from the group consisting of poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol), poly(ethylenimine), N,N-di(aminoethyl)carbamoyloxyethyl-, choline, monosaccharide, disaccharide, ethanolamine, phosphatidylcholine, phosphatidylethanolamine, cardiolipin, and phosphatidylmonosaccharides and phosphatidyldisaccharides.
10. The compound of claim 9 , wherein the hydrophilic headgroup is poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol) or poly(ethylenimine), N,N-di(aminoethyl)carbamoyloxyethyl-.
11. The compound of claim 10 , wherein the hydrophilic headgroup is poly(ethylene glycol) or C 1 –C 6 alkoxy poly(ethylene glycol) and the poly(ethylene glycol) moiety has an average of 1 to about 300 ethylene glycol units.
12. The compound according to claim 11 wherein the poly(ethylene glycol) moiety has an average of between about 10 and 150 ethylene glycol units.
13. The compound according to claim 8 wherein either R 1 or R 2 is poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol) or poly(ethylenimine) or N,N-di(aminoethyl)carbamoyloxyethyl- and the other of R 1 or R 2 is hydrogen; and R 3 is selected from the group consisting of cholesterol, a cholesterol derivative and a group of the formula:
wherein each R 5 is independently a hydrophobic group of the formula:
wherein X is O; n is an integer from 5 to 32 inclusive; y is an even integer from 2 to 12 inclusive; and y is less than or equal to n.
14. A vinyl ether lipid compound of the formula:
wherein each of R 1 or R 2 is independently a hydrophilic headgroup selected from the group consisting of poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol), poly(ethylenimine), N,N-di(aminoethyl)carbamoyloxyethyl-, choline, monosaccharide, disaccharide, ethanolamine, phosphatidylcholine, phosphatidylethanolamine, cardiolipin, and phosphatidylmonosaccharides and phosphatidyldisaccharides;
R 3 is an organic hydrophobic moiety; and
R 4 is an electron donating group.
15. The compound according to claim 14 wherein R 3 is selected from the group consisting of cholesterol, a cholesterol derivative and a group of the formula:
wherein each R 5 is independently a hydrophobic group of the formula:
wherein X is O or S; n is an integer from 5 to 32 inclusive; y is an even integer from 2 to 12 inclusive; and y is less than or equal to n.
16. The compound according to claim 14 wherein R 4 is selected from the group consisting of C 1 –C 6 alkoxy, furan, thiophene, methoxyphenyl, dimethoxyphenyl and trimethoxyphenyl.
17. The compound according to claim 15 wherein R 4 is selected from the group consisting of C 1 –C 6 alkoxy, furan, thiophene, methoxyphenyl, dimethoxyphenyl and trimethoxyphenyl.
18. The compound according to claim 14 wherein said hydrophilic headgroups are selected from the group consisting of poly(ethylene glycol), C 1 –C 6 alkoxy poly(ethylene glycol) or poly(ethylenimine), N,N-di(aminoethyl)carbamoyloxyethyl-.
19. A lipid vesicle comprising at least two different species of lipid compounds, at least one of said lipid compounds being a vinyl ether lipid compound according to claim 1 .
20. A lipid vesicle comprising at least two different species of lipid compounds, at least one of said lipid compounds being a vinyl ether lipid compound according to claim 7 .
21. A lipid vesicle comprising at least two different species of lipid compounds, at least one of said lipid compounds being a vinyl ether lipid compound according to claim 8 .
22. A lipid vesicle comprising at least two different species of lipid compounds, at least one of said lipid compounds being a vinyl ether lipid compound according to claim 14 .
23. The lipid vesicle according to any of claims 19 – 22 wherein said vinyl ether lipid compound comprises between about 0.1% and about 20% of the total molar lipid concentration of said vesicle.
24. The lipid vesicle of any of claims 19 – 23 wherein said vinyl ether lipid compound comprises between about 1% and about 15% of the total molar lipid concentration of said vesicle.
25. A method of delivering a therapeutic or diagnostic agent to a predetermined in vivo tissue or to the interior of a living cell, comprising contacting said tissue or cell with a liposome encapsulating said agent, under acidic or oxidative conditions, said liposome comprising at least two different species of lipid compounds, at least one of said lipid compounds being a vinyl ether lipid compound according to any of claim 1 , 7 , 8 or 14 , said acidic or oxidative conditions being effective for cleaving said hydrophilic headgroup from said vinyl ether lipid compound.
26. A pharmaceutical composition comprising a therapeutic or diagnostic agent encapsulated in a lipid vesicle according to any of claims 19 – 22 in a pharmaceutically acceptable carrier.