US 8,992,970 B2  88  87  Example 74  Drug Loading into Liposomes Containing 1.05 N  Diethylammonium Sucrose Octasulfate  Aqueous solution of 1.05 N diethylammonium sucrose  octasulfate (DEA-SOS) pH 6.0, osmolarity 727 mmol/kg,  was  prepared using ion-exchange/titration method of  Example 6 using neat diethylamine (99 .5% purity). The lipid  matrix of3 molar parts DSPC, 2 molar parts Cholesterol, and  0.015 molar parts PEG2000-DSPE, was formulated into lipo› somes (volume-weighted average size 92.4 nm) in the pres› ence of DEA-SOS solution, and CPT-11 was loaded in the  liposomes as various drug/lipid input ratios using the method  of Example 11. Non-encapsulated drug was removed by gel› chromatography, and the amount of encapsulated drug per  unit lipid ( drug/lipid output ratio) was determined. Encapsu› lation efficiency was calculated as% of drug/lipid output ratio  relative to input ratio. The results are shown in Table 40. The  loading achieved it’s maximum level of about 1.76 mo! drug  per mo! phospholipid (1.67-1.70 mo! drug/g total lipid),  which is in good agreement with the amount (1.78 mo!  diethylammonium/mol  phospholipid)  based  on  the  diethyammonium content of the liposomes, assuming stio› chiometric exchange of intraliposomal diethylammonium  ions for the drug molecules and estimated intraliposomal  entrapped volume of approximately 1.7 I/mo! phospholipid.  entrapped inside the liposomes is at a concentration that  exceeds the concentration of the irinotecan in the aqueous  medium.  2.  The liposomal composition of claim  1,  where irinotecan,  sucrose octasulfate, and substituted anmionium compound  are entrapped inside the liposomes and wherein the substi› tuted anmionium compound has a formula: R$_{1 }$-(R$_{2}$-)N+  (-R$_{3}$)-R$_{4}$ ,  wherein N is a an ammonium nitrogen atom,  each ofRi, R$_{2}$ ,  R$_{3}$ ,  and R$_{4 }$ is independently a hydrogen atom  or an organic group having each independently not more than  8 carbon atoms, and in totality not more than 18 carbon atoms  inclusive, wherein at least one of Ri, R$_{2}$ ,  R$_{3}$ ,  and R$_{4 }$ is an  organic group; wherein the organic group is independently  alkyl, alkylidene, heterocyclic alkyl, cycloalkyl, aryl, alkenyl,  cycloalkenyl, or a hydroxy-substituted derivative thereof,  optionally including S,  0,  or N atoms forming an ether, ester,  thioether, amine, or amide bond; and wherein at least three of  Ri, R$_{2}$ ,  R$_{3}$ ,  andR$_{4 }$ are the organic groups; or at least one of the  organic groups has a secondary or tertiary carbon atom  directly linked to the anmionium nitrogen atom.  3.  The liposomal composition of claim  2,  wherein the  substituted ammonium compound is selected from the group  consisting of isopropy lethylanmionium, isopropy lmethy !am› monium, diisopropylanmionium, tert-butylethylammonium,  dicyclo-hexylanmionium, morpholinium, pyridinium, pip› eridinium, pyrrolidinium, piperazinium, tert-butylammo› nium,  2-ammonio-2-methyl-propanol-1,2-ammonio-2-me› thyl-propandiol-1,3, tris-(hydroxyethyl)-anmioniomethane,  N,N’-diethyl-ethanolammonium, N,N’,N"-tris-(2-hydroxy- ethyl)ammonium,  N,N’-bis-(2-hydroxyethyl)ethylammo- nium, trimethyl-ammonium, triethylanmionium, diethylm› ethyl-ammonium,  diisopropylethylammonium,  triisopropylammonium, N-methyl-morpholinium, 1-(2-hy› droxyethyl)piperidinium, 1-methylpyrrolidinium, l ,4-dim- ethyl-piperazinium, tetramethylammonium, tetraethyl-am› monium, and tetrabutylammonium.  Unless indicated otherwise, the analytical data are pre› sented as the mean–standard error of triplicate runs. The rat  plasma pharmacokinetic data are the mean–standard error of  duplicate runs.  What is claimed is:  1.  A liposomal composition comprising liposomes in an  aqueous medium, the liposomes having an interior aqueous  space separated from the aqueous medium by a membrane  comprising 1,2-distearoyl-SN-phosphatidylcholine, choles› terol and N-(omega-methoxy-poly(ethylene glycol)-oxycar› bonyl)-1,2-distearoylphosphatidyl  ethanolamine,  and  entrapped inside the liposomes are either: 1) irinotecan and  sucrose octasulfate, or 2) irinotecan, sucrose octasulfate and a  substituted anmionium compound; wherein, the irinotecan  13.  The liposomal composition of claim  1,  wherein the  aqueous medium comprises hydroxyethylpiperazine-ethyl› sulfonate (HEPES) and NaCl.  12.  The liposomal composition of claim  1,  wherein the  irinotecan and the sucrose octasulfate are comprised in the  form of a salt.  11.  The liposomal composition of claim  1,  wherein the  relative amounts of the irinotecan and the sucrose octasulfate  are at the point of stoichiometric equivalency.  10.  The liposomal composition of claim  1,  wherein the  relative amounts of the irinotecan and the sucrose octasulfate  are near the point of stoichiometric equivalency.  9.  The liposomal composition of claim  1,  wherein molar  ratio of the irinotecan to the totality of the lipids is at least 1.0.  8.  The liposomal composition of claim  1,  wherein the  composition is a fluid pharmaceutical formulation for  parenteral administration.  7.  The liposomal composition of claim  6,  wherein the  poly(ethylene glycol) in the N-(omega-methoxy-poly(ethyl› ene glycol)-oxycarbonyl)-1,2-distearoylphosphatidyl etha› nolamine has a molecular weight of about 2,000.  6.  The liposomal composition of claim  1,  wherein the  membrane comprises about 59 .8 mo!.% of the 1,2-distearoyl› SN-phosphatidylcholine; about 39.9 mo!. % of the choles› terol and about 0.3 mo!.% of the N-(omega-methoxy-poly  ( ethylene glycol)-oxycarbonyl)-1,2-distearoylphosphatidyl  ethanolamine.  5.  The liposomal composition of claim  2,  wherein the  substituted ammonium compound is diethylanmionium.  4.  The liposomal composition of claim  2,  wherein the  substituted ammonium compound is triethylammonium.  TABLE 40  Loading of CPT-11 in DSPC/Chol/PEG-DSPE  liposomes containing 1.05N DEA-SOS.  Drug/lipid input  Drug/lipid output  Encapsulation  ratio, mol/g  ratio, mol/g  efficiency,%  1.25  1.247 –0.038  99.8 – 3.0  1.50  1.534 – 0.052  102.3 – 3.5  1.80  1.669 – 0.043  92.7 – 2.4  2.06  1.690 – 0.054  82.0 – 2.6  2.20  1.704 – 0.062  77.5 – 2.8  2.42  1.685 –0.103  69.6 –4.3  Although the invention has been described with reference  to the presently preferred embodiment, it should be under› stood that various modifications can be made without depart› ing from the spirit of the invention. Accordingly, the scope of $_{50 }$ the invention should be determined with reference to the  appended claims, along with the full scope of equivalents to  which such claims are entitled. The disclosures of all cited  articles and references, including patent applications and  publications, are incorporated herein by reference for all pur- 55  poses. 