Liposome composition for improved intracellular delivery of a therapeutic agent

Abstract

A liposomal composition and a method of using the same for achieving intracellular delivery of a liposome-entrapped agent is described. The liposomes are composed of a pH sensitive lipid and include a targeting ligand to direct the liposomes to a target cell. The liposomes also include a stabilizing component, such a polymer-derivatized lipid, where the polymer is attached to the lipid by a releasable linkage. Administration of the liposomes results in cellular internalization and destabilization of the liposome for intracellular delivery of the entrapped agent.

1 . A liposome composition for intracellular delivery of a therapeutic agent, comprising liposomes consisting essentially of (i) a pH-sensitive lipid; (ii) between 1-20 mole percent of a lipid derivatized with a hydrophilic polymer, said polymer attached to said lipid by a bond effective to release the hydrophilic polymer in response to an existing or an induced physiologic condition; (iii) a targeting ligand; and (iv) an entrapped therapeutic agent; 
 wherein said composition is adapted to bind to a target cell and to release said entrapped agent to achieve at least a two-fold increase in intracellular concentration of the agent, when compared to intracellular concentration of the agent delivered by similar liposomes lacking said releasable bond and/or said targeting ligand.    
   
   
       2 . The composition of  claim 1 , wherein said pH-sensitive lipid is dioleoylphosphatidylethanolmaine (DOPE).  
   
   
       3 . The composition of  claim 1 , wherein said liposomes further include a stabilizing component.  
   
   
       4 . The composition of  claim 3 , wherein said stabilizing component is cholesteryl hemisuccinate (CHEMS).  
   
   
       5 . The composition of  claim 1 , wherein said lipid derivatized polymer is phosphatidylethanolamine derivatized with polyethyleneglycol.  
   
   
       6 . The composition of  claim 1 , wherein said targeting ligand an antibody or an antibody fragment.  
   
   
       7 . The composition of  claim 6 , wherein said antibody fragment is selected from the group consisting of anti-CD19, anti-CD20, anti-CD22.  
   
   
       8 . The composition of  claim 1 , wherein said releasable bond contains a disulfide bond.  
   
   
       9 . The composition of  claim 8 , wherein said disulfide bond is in a dithiobenzyl bond.  
   
   
       10 . A method for increasing intracellular cytotoxicity of a liposome-entrapped agent, comprising 
 providing liposomes consisting essentially of (i) a pH-sensitive lipid; (ii) between 1-20 mole percent of a lipid derivatized with a hydrophilic polymer, said polymer attached to said lipid by a bond effective to release the hydrophilic polymer in response to an existing or an induced physiologic condition; (iii) a targeting ligand; and (iv) an entrapped therapeutic agent;    administering said liposomes to achieve (i) cleavage of the releasable bond, thereby releasing said hydrophilic polymer chain; (ii) binding of said ligand to a target cell, where said binding occurs prior to or subsequent to said cleavage; and (iii) internalization of said liposome by said target cell;    whereby said administering is effective to achieve at least a two-fold higher intracellular cytotoxicity of said agent, relative to intracellular concentration of the agent delivered by similar liposomes lacking said releasable bond and/or said targeting ligand.    
   
   
       11 . The method of  claim 10 , wherein cleavage of said releasable bond after said administering is achieved by naturally-occurring blood components.  
   
   
       12 . The method of  claim 10 , wherein said pH-sensitive lipid is dioleoylphosphatidylethanolmaine (DOPE).  
   
   
       13 . The method of  claim 10 , wherein said liposomes further include a stabilizing component.  
   
   
       14 . The method of  claim 13 , wherein said stabilizing component is cholesteryl hemisuccinate (CHEMS).  
   
   
       15 . The method of  claim 10 , wherein said lipid derivatized polymer is phosphatidylethanolamine derivatized with polyethyleneglycol.  
   
   
       16 . The method of  claim 10 , wherein said targeting ligand an antibody or an antibody fragment.  
   
   
       17 . The method of  claim 16 , wherein said antibody fragment is selected from the group consisting of anti-CD19, anti-CD20, anti-CD22.  
   
   
       18 . The method of  claim 10 , wherein said releasable bond contains a disulfide linkage.  
   
   
       19 . The method of  claim 19 , wherein said disulfide linkage is a dithiobenzyl bond.  
   
   
       20 . A method for increasing accumulation of a therapeutic agent into cellular nuclei, comprising 
 providing liposomes consisting essentially of (i) a pH-sensitive lipid; (ii) between 1-20 mole percent of a lipid derivatized with a hydrophilic polymer, said polymer attached to said lipid by a bond effective to release the hydrophilic polymer in response to an existing or an induced physiologic condition; (iii) a targeting ligand; and (iv) an entrapped therapeutic agent;    administering said liposomes to achieve (i) cleavage of the releasable bond, thereby releasing said hydrophilic polymer chain; (ii) binding of said ligand to a target cell, where said binding occurs prior to or subsequent to said cleavage; and (iii) internalization of said liposome by said target cell;    whereby said administering is effective to achieve at least a two-fold higher accumulation of said agent in the nucleus of the target cell, when compared to intracellular concentration of the agent delivered by similar liposomes lacking said releasable bond and/or said targeting ligand.    
   
   
       21 . The method of  claim 20 , wherein cleavage of said releasable bond after said administering is achieved by naturally-occurring blood components.  
   
   
       22 . The method of  claim 20 , wherein said pH-sensitive lipid is dioleoylphosphatidylethanolmaine (DOPE).  
   
   
       23 . The method of  claim 20 , wherein said liposomes further include a stabilizing component.  
   
   
       24 . The method of  claim 23 , wherein said stabilizing component is cholesteryl hemisuccinate (CHEMS).  
   
   
       25 . The method of  claim 20 , wherein said lipid derivatized polymer is phosphatidylethanolamine derivatized with polyethyleneglycol.  
   
   
       26 . The method of  claim 20 , wherein said targeting ligand an antibody or an antibody fragment.  
   
   
       27 . The method of  claim 26 , wherein said antibody fragment is selected from the group consisting of anti-CD19, anti-CD20, anti-CD22.  
   
   
       28 . The method of  claim 20 , wherein said releasable bond contains a disulfide linkage.  
   
   
       29 . The method of  claim 28 , wherein said disulfide linkage is in a dithiobenzyl bond.