Neutral-cationic lipid for nucleic acid and drug delivery

Abstract

A lipid represented by the formula: wherein each of R 1 and R 2 is an alkyl or alkenyl chain having between about 8 to about 24 carbon atoms; n=0-20; L is selected from the group consisting of (i) —X—(C═O)—Y—, (ii) —X—(C═O)—, and (iii) —X—CH 2 —, wherein X and Y are independently selected from oxygen, NH and a direct bond; and Z is a weakly basic moiety that has a pK of less than about 7.4 and greater than about 4.0 is described.

1 . A liposome composition comprising: 
 a lipid having the formula                          wherein each of R 1  and R 2  is an alkyl or alkenyl chain having between about 8 to about 24 carbon atoms;    n=0-20;    L is selected from the group consisting of: (i) —X—(C═O)—Y—, (ii) —X—(C═O)—, and (iii) —X—CH 2 —, wherein X and Y are independently selected from oxygen, NH, and a direct bond;    Z is a weakly basic moiety that has a pK of less than about 7.4 and greater than about 4.0.    
     
     
         2 . The composition of  claim 1 , wherein X is NH and Y is oxygen.  
     
     
         3 . The composition of  claim 1 , wherein L is a carbamate linkage, an ester linkage or a carbonate linkage.  
     
     
         4 . The composition of  claim 1 , wherein L is NH—(C═O)—O—.  
     
     
         5 . The composition of  claim 1 , wherein Z is an imidazole.  
     
     
         6 . The composition of  claim 1 , comprising between about 1 to about 80 mole percent of the lipid.  
     
     
         7 . The composition of  claim 1 , wherein Z is a moiety having a pK value between about 5.0 to about 6.5.  
     
     
         8 . The composition of  claim 1 , wherein each of R 1  and R 2  is an unbranched alkyl or alkenyl chain having between about 8 to about 24 carbon atoms.  
     
     
         9 . The composition of  claim 8 , wherein each of R 1  and R 2  is C 17 H 35 .  
     
     
         10 . The composition of  claim 1 , wherein n is between 1-10.  
     
     
         11 . The composition of  claim 1 , further comprising a therapeutic compound entrapped in the liposomes.  
     
     
         12 . The composition of  claim 11 , wherein the therapeutic agent is a nucleic acid.  
     
     
         13 . The composition of  claim 12 , wherein the nucleic acid is selected from the group consisting of DNA, RNA, and their complements.  
     
     
         14 . The composition of  claim 1 , further comprising a ligand for targeting the liposomes to a target site.  
     
     
         15 . The composition of  claim 14 , wherein the ligand has binding affinity for endothelial tumor cells and is internalized by the cells.  
     
     
         16 . The composition of  claim 15 , wherein the ligand is selected from the group consisting of E-selectin, Her-2, and FGF.  
     
     
         17 . The composition of  claim 1 , wherein the liposomes further comprise between about 5 to about 20 mole percent of a vesicle-forming lipid derivatized with a hydrophilic polymer chain.  
     
     
         18 . The composition of  claim 17 , wherein the hydrophilic polymer chain is polyethyleneglycol (PEG).  
     
     
         19 . A lipid having the formula:  
       
         
           
           
               
               
           
         
         wherein each of R 1  and R 2  is an alkyl or alkenyl chain having between about 8 to about 24 carbon atoms;  
         n=0-20;  
         L is selected from the group consisting of (i) —X—(C═O)—Y—CH 2 —, (ii) —X—(C═O)—, and (iii) —X—CH 2 —, wherein X and Y are independently selected from oxygen, NH and a direct bond; and  
         Z is a weakly basic moiety that has a pK of less than about 7.4 and greater than about 4.0.  
       
     
     
         20 . The lipid of  claim 19 , wherein X is NH and Y is oxygen.  
     
     
         21 . The lipid of  claim 19 , wherein L is a carbamate linkage, an ester linkage or a carbonate linkage.  
     
     
         22 . The lipid of  claim 19 , wherein L is NH—(C═O)—O—.  
     
     
         23 . The lipid of  claim 22 , wherein Z is an imidazole.  
     
     
         24 . The lipid of  claim 19 , wherein Z is a moiety having a pK value between about 5.0 to about 6.5.  
     
     
         25 . The lipid of  claim 19 , wherein each of R 1  and R 2  is an unbranched alkyl or alkenyl chain having between about 8 to about 24 carbon atoms.  
     
     
         26 . The lipid of  claim 23 , wherein each of R 1  and R 2  is C 17 H 35 .  
     
     
         27 . The lipid of  claim 19 , wherein n is between 1-10.  
     
     
         28 . A liposome comprising the lipid according to  claim 19 .  
     
     
         29 . A liposome comprising the lipid according to  claim 26 .  
     
     
         30 . A method for delivering a therapeutic agent to a subject, comprising: 
 preparing liposomes comprising a lipid having the formula                          wherein each of R 1  and R 2  is an alkyl or alkenyl chain having between about 8 to about 24 carbon atoms;    n=0-20;    L is selected from the group consisting of (i) —X—(C═O)—Y—, (ii) —X—(C═O)—, and (iii) —X—CH 2 —, wherein X and Y are independently selected from oxygen, NH, and a direct bond;    Z is a weakly basic moiety that has a pK of less than about 7.4 and greater than about 4.0; and    administering the liposomes to the subject.    
     
     
         31 . The method of  claim 30 , wherein the preparing comprises entrapping a nucleic acid in the liposomes.  
     
     
         32 . The method of  claim 31 , wherein the nucleic acid is DNA, RNA, or their complements.  
     
     
         33 . The method of  claim 30 , wherein the preparing further comprises entrapping a protein or a protein fragment in the liposomes.