Preparation of a lipid blend and a phospholipid suspension containing the lipid blend

Abstract

The present invention describes processes for the preparation of a lipid blend and a uniform filterable phospholipid suspension containing the lipid blend, such suspension being useful as an ultrasound contrast agent.

What is claimed as new and desired to be secured by Letter Patent of United States is:  
     
         1 . A process for preparing a phospholipid suspension, comprising: 
 (1) contacting a lipid blend with a non-aqueous solvent, whereby the lipid blend substantially dissolves in the non-aqueous solvent; and,    (2) contacting the solution from step (1) with an aqueous solution to form a lipid suspension.    
     
     
         2 . A process according to    claim 1   , wherein the non-aqueous solvent is selected from propylene glycol, ethylene glycol, and polyethylene glycol 300.  
     
     
         3 . A process according to    claim 2   , wherein the non-aqueous solvent is propylene glycol.  
     
     
         4 . A process according to    claim 2   , wherein the lipid blend, comprises: 
 (a) 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine;    (b) 1,2-dipalmitoyl-sn-glycero-3-phosphotidic, mono sodium salt; and,    (c) N-(methoxypolyethylene glycol 5000 carbamoyl)-1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine, mono sodium salt.    
     
     
         5 . A process according to    claim 2   , wherein the non-aqueous solvent is heated to a temperature of about 30 to 70° C. prior to contacting with the lipid blend.  
     
     
         6 . A process according to    claim 5   , wherein the non-aqueous solvent is heated to a temperature of about 50 to 55° C. prior to contacting with the lipid blend.  
     
     
         7 . A process according to    claim 2   , wherein the ratio of lipid blend to non-aqueous solvent is from about 5 mg of lipid blend per mL of non-aqueous solvent to about 15 mg/mL.  
     
     
         8 . A process according to    claim 7   , wherein the ratio of lipid blend to non-aqueous solvent is about 10 mg/mL.  
     
     
         9 . A process according to    claim 2   , wherein in step (2), the aqueous solution is selected from water, saline, a saline/glycerin mixture, and a saline/glycerin/non-aqueous solvent mixture.  
     
     
         10 . A process according to    claim 9   , wherein the aqueous solution is a saline and glycerin mixture.  
     
     
         11 . A process according to    claim 9   , wherein the aqueous solution is a saline, glycerin, and propylene glycol mixture.  
     
     
         12 . A process according to    claim 11   , wherein 6.8 mg/mL of sodium chloride are present, 0.1 mL/mL of glycerin are present, 0.1 mL/mL of propylene glycol are present, and about 0.75 to 1.0 mg/mL of the lipid blend are present.  
     
     
         13 . A process according to    claim 12   , wherein 0.75 mg/mL of lipid blend are present.  
     
     
         14 . A process according to    claim 12   , wherein 1.0 mg/mL of lipid blend are present.  
     
     
         15 . A process according to    claim 2   , wherein in step (2), the aqueous solution is heated to a temperature of about 45 to 60° C. prior to contacting with the solution from step (1).  
     
     
         16 . A process according to    claim 15   , wherein the aqueous solution is heated to a temperature of about 50 to 55° C. prior to contacting with the solution from step (1).  
     
     
         17 . A process according to    claim 1   , wherein the process further comprises: 
 (3) heating the lipid suspension from step (2) to a temperature about equal to or above the highest gel to liquid crystalline phase transition temperature of the lipids present in the suspension.    
     
     
         18 . A process according to    claim 17   , wherein in step (3), the lipid suspension is heated to a temperature of at least about 67° C.  
     
     
         19 . A process according to    claim 17   , wherein the process further comprises: 
 (4) filtering the lipid suspension through a sterilizing filter.    
     
     
         20 . A process according to    claim 19   , wherein in step (4), the filtration is performed using two sterilizing filter cartridges.  
     
     
         21 . A process according to    claim 20   , wherein in step (4), the sterilizing filter cartridges are at a temperature of from about 70 to 80° C.  
     
     
         22 . A process according to    claim 21   , wherein in step (4), 0.2 μm hydrophilic filters are used.  
     
     
         23 . A process according to    claim 19   , wherein the process further comprises: 
 (5) dispensing the filtered solution from step (4) into a vial.    
     
     
         24 . A process according to    claim 23   , wherein the process further comprises: 
 (6) exchanging the headspace gas of the vial from step (5) with a perfluorocarbon gas.    
     
     
         25 . A process according to    claim 24   , wherein the perfluorocarbon gas is perfluoropropane.  
     
     
         26 . A process according to    claim 25   , wherein exchange of headspace gas is performed using a lyophilizing chamber.  
     
     
         27 . A process according to    claim 24   , wherein the process further comprises: 
 (7) sterilizing the vial from step (6).    
     
     
         28 . A process according to    claim 27   , wherein in step (7), the vial is sterilized at about 126-130° C. for 1 to 10 minutes.  
     
     
         29 . A process for preparing a lipid blend, comprising: 
 (a) contacting at least two lipids with a first non-aqueous solvent;    (b) concentrating the solution to a thick gel;    (c) contacting the thick gel with a second non-aqueous solvent; and,    (d) collecting the resulting solids.    
     
     
         30 . A process according to    claim 29   , wherein in step (a), the lipids are: 
 (i) 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine;    (ii) 1,2-dipalmitoyl-sn-glycero-3-phosphotidic, mono sodium salt; and,    (iii) N-(methoxypolyethylene glycol 5000 carbamoyl)-1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine, mono sodium salt.    
     
     
         31 . A process according to    claim 30   , wherein in step (a), the first non-aqueous solvent is a mixture of methanol and toluene.  
     
     
         32 . A process according to    claim 30   , wherein in step (c), the second non-aqueous solvent is a methyl t-butyl ether.  
     
     
         33 . A process according to    claim 30   , wherein in step (a), the solution is warmed to a temperature sufficient to complete dissolution of the lipids into the solvent.  
     
     
         34 . A process according to    claim 33   , wherein in step (a), the solution is warmed to about 25 to 75° C.  
     
     
         35 . A process according to    claim 30   , wherein in step (d), the solids collected are washed with methyl t-butyl ether and dried in vacuo.  
     
     
         36 . A phospholipid suspension, comprising: 
 (a) a lipid blend in an amount of about 0.75-1.0 mg/mL of suspension;    (b) sodium chloride in an amount of about 6.8 mg/mL of suspension;    (c) glycerin in an amount of about 0.1 mL/mL of suspension;    (d) propylene glycol in an amount of about 0.1 mL/mL of suspension; and    (e) water;    wherein the suspension is prepared by the process, comprising:    (1) contacting a lipid blend with a non-aqueous solvent, whereby the lipid blend substantially dissolves in the non-aqueous solvent;    (2) contacting the solution from step (1) with an aqueous solution to form a lipid suspension;    (3) heating the lipid suspension from step (2) to a temperature about equal to or above the highest gel to liquid crystalline phase transition temperature of the lipids present in the suspension; and,    (4) filtering the lipid suspension through a sterilizing filter.    
     
     
         37 . A phospholipid suspension according to    claim 36   , wherein the lipid blend, comprises: 
 (a) 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine;    (b) 1,2-dipalmitoyl-sn-glycero-3-phosphotidic, mono sodium salt; and,    (c) N-(methoxypolyethylene glycol 5000 carbamoyl)-1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine, mono sodium salt.    
     
     
         38 . A phospholipid suspension according to    claim 37   , wherein the non-aqueous solvent is heated to a temperature of about 50 to 55° C. prior to contacting with the lipid blend.  
     
     
         39 . A phospholipid suspension according to    claim 37   , wherein the ratio of lipid blend to non-aqueous solvent is about 10 mg/mL.  
     
     
         40 . A phospholipid suspension according to    claim 37   , wherein the aqueous solution is a saline, glycerin, and propylene glycol mixture.  
     
     
         41 . A phospholipid suspension according to    claim 40   , wherein 0.75 mg/mL of lipid blend are present.  
     
     
         42 . A phospholipid suspension according to    claim 37   , wherein the aqueous solution is heated to a temperature of about 50 to 55° C. prior to contacting with the solution from step (1).  
     
     
         43 . A phospholipid suspension according to    claim 37   , wherein in step (3), the lipid suspension is heated to a temperature of at least about 67° C.  
     
     
         44 . A phospholipid suspension according to    claim 43   , wherein in step (4), two 0.2 μm hydrophilic filters are used.