LIPID FORMULATIONS FOR TARGET DELIVERY

Abstract: The present invention provides lipid-based systemic delivery vehicles and method for selectively targeting an active agent to a specific tissue site. The methods include designing a lipid-based systemic delivery vehicle having a plurality of constitutent parts, and thereafter varying the amounts of each of the plurality of constituent parts to impart tissue selectivity. After tissue selectivity is imparted it is possible to selectively target an active agent to a specific tissue site.

Description: LIPID FORMULATIONS FOR TARGET DELIVERY CROSS-REFERENCES TO RELATED APPLICATIONS This application claims priority to U. S . Provisional Patent Application No . 60/243,185, filed October 25, 2000, the teachings of which are hereby incorporated by reference in their entirety for all purposes. FIELD OF THE INVENTION This invention relates to lipid formulations, and more particularly, to nucleic acid-lipid particles useful as targeted gene delivery vehicles. BACKGROUND OF THE INVENTION Current gene delivery systems for systemic gene therapy include viral and non-viral systems. Viral gene transfer systems are rapidly cleared from circulation upon systemic administration, limiting their use to first pass organs such as the liver or lungs. In addition, the immimogenicity of viral systems directs an acute inflammatory response, which at best limits the effect of subsequent doses and at worst can be hazardous to the patient (see, Wprgall et al, Human Gene Therapy, 8: 37-44, 1997). Non-viral systems, such as plasmid- DNA-cationic lipid complexes (lipoplexs) perform adequately in vitro, but due to their large size and positive surface charge, lipoplex are also rapidly cleared from circulation and are similarly limited to applications involving transfection of first pass organs (see, Hofland et al., Pharmaceutical Res, 14: 742-749 1997). DNA-cationic lipid complexes have also been shown to exhibit significant toxicity (see, Li and Huang, Gene Therapy, 4: 891-900, 1997). A fundamental hurdle for gene drugs is delivery of the gene to an area of interest because large nucleic acids are rapidly degraded upon exposure to serum. However, this hurdle has been overcome for local and regional (i.e., inhalation or direct injection) delivery by the use of viral vectors, lipid complexes and the like. For systemic (i.e., intravenous) delivery, the hurdle has been overcome by the use of stable plasmid-lipid particles ("SPLPs") disclosed in PCT Publication No. WO 96/40964, which is incorporated herein by reference. SPLPs are fully encapsulated lipid-plasmid particles that are resistant to nuclease degradation, have low immunogenicity, and are of small size (<150 nm), thereby making them particularly well suited for long circulation lifetimes. The SPLPs can be produced using detergent dialysis methods that allows for complete encapsulation of plasmid DNA inside small (~70 nm), well defined lipid vesicles (see, Wheeler et al, Gene Therapy, 6: 271-281, 1999). These vesicles contain fusogenic helper lipids, which are known to induce fusion with cellular membranes. Since fusogenic lipids do not readily form the bilayer structured needed for liposome formation; they require stabilization or aggregating preventing agent such as polyethylene glycol (PEG)-lipid conjugates or anchors. The resulting particles have been shown to have circulation half-lives that are dependent on the length of the lipid anchor. Circulation half lives varied from 1.2 min (PEG-CerCs) to 13 h (PEG-CerC 2 o). This property permits the construction of a 'programmable' fusogenic gene delivery system. As the PEG-Cer diffuses out of the SPLP membrane at a rate that is dependent on its anchor length, the SPLP becomes more unstable and fusogenic, resulting in membrane fusion and release of the plasmid DNA payload. These particles exhibit extended circulation lifetimes, and enhanced pharmacokinetics over viral and other non-viral systems. In vitro studies have shown SPLP's with high levels of cationic lipid (24 mol %) have transfection properties, which are better than plasmid DNA-cationic lipid complexes. Despite the advances made in the SPLP technology, what is needed in the art are formulations that allow delivery of a payload to a target, i.e., a particular tissue site of interest. The present invention fulfills this and other needs. SUMMARY OF THE INVENTION In one embodiment, the present invention provides a method for identifying a lipid-based systemic delivery vehicle capable of selectively targeting an active agent to a specific tissue site, the method comprising: designing a lipid-based systemic delivery vehicle having a plurality of constituent parts; and varying the amount of each of the plurality of constituent parts to impart tissue selectivity, thereby identifying a lipid-based systemic delivery vehicle capable of selectively targeting an active agent to a specific tissue site. In preferred aspects, the constituent parts exclude targeting moieties (e.g., antibodies). Suitable tissue types include, but are not limited to, organs, bones, various types of tumors, and combinations thereof. Tissue selectivity can be determined using a variety of in vivo and in vitro assays. These assays represent yet other embodiment of the present invention. As such, the present invention provides an assay method for determining tissue selectivity, the method comprising: injecting a lipid-based systemic delivery vehicle having a plurality of constituent parts into the tail vein of a mouse to generate a biodistribution pattern; and analyzing the biodistribution patten thereby determining tissue selectivity. Another assay method for determining tissue selectivity comprises: providing a multiwell plate, (e.g., a multiwell microtiter plate) having a first well and a second well, . each well having a tissue type disposed therein; dispensing an array of nucleic acid-lipid particles, where the array of nucleic acid-lipid particles comprises a first nucleic acid-lipid particle having a first plurality of constituent parts dispensed in the first well, and a second nucleic acid-lipid particle having a second plurality of constituent parts dispensed in the second well; and thereafter determining the.transfection efficiency of each of the nucleic acid in the array of nucleic acid-lipid particles in the tissue. In_another embodiment, the present invention provides an array of nucleic acid-lipid particles having tissue selectivity. The array of nucleic acid-lipid particles . comprises a first nucleic acid-lipid particle having a first plurality of constituent parts and a first tissue selectivity and a second nucleic acid-lipid particle having a second plurality of constituent parts and a second tissue selectivity, wherein the first and second nucleic acid- lipid particles are constitutively different. In yet another embodiment, the present invention provides lipid-based systemic delivery vehicles ("LBSDVs"). In certain preferred aspects, the systemic delivery vehicle is a nucleic acid-lipid particle, the nucleic acid-lipid particle comprising: (a) a nucleic acid; (b) a cationic lipid; (c) a bilayer stabilizing component; and (d) cholesterol. The nucleic acid-lipid particle optionally further comprises (e) another lipid, such as a cationic "lipid and/or (f) a cationic polymer lipid having Formula I: A W Y I In Formula I, A is a lipid moiety; W is a hydrophilic polymer; and Y is a polycationic moiety. In certain aspects, a dansylated lysine spacer is inserted between A and W. In still yet another aspect, the present invention provides a method for delivering a payload to a specific tissue site, the method comprising: administering a lipid- based systemic delivery vehicle having tissue selectivity, wherein the lipid-based systemic delivery vehicle has a plurality of constituent parts, thereby delivering a payload to a specific tissue site. Preferably, the LBSDVs exclude targeting moieties. Using the LBSDVs of the present invention it is possible to deliver nucleic acids encoding tumor suppressor genes such as p53, pi lORb, and p72, to a specific tumor site. In another embodiment, the present invention provides a method for determining nucleic acid functionality at a specific tissue site, the method comprising: administering a lipid-based systemic delivery vehicle having tissue selectivity to a mammal, the lipid-based systemic delivery vehicle comprising a nucleic acid; and analyzing the effect if any, of the nucleic acid on the specific tissue site, thereby determining nucleic acid functionality. These and other embodiments will become more apparent when read with the acc mpan ing drawings and the BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates SPLP can be engineered to elicit tumor specific gene expression. Figure 2 illustrates SPLP for liver gene expression. These SPLPs have been designed for effective delivery to the liver. Figure 3 illustrates SPLP for liver gene expression. As shown therein, the > SPLPs are rapidly cleared from the blood compartment. Figure 4 illustrates gene expression in subcutaneous Neuro2A tumors following V. injection of SPLP. Figure 5 illustrates luciferase gene expression in the liver from Neuro-2a tumor bearing male A/J mice. Figure 6 illustrates luciferase gene expression in the heart from Neuro-2a tumor bearing male A/J mice. Figure 7 illustrates luciferase gene expression in Neuro-2a tumor bearing mice following a single IV administration of INEX 303. Figure 8 illustrates potency of SPLP : tumor gene expression following intravenous administration of SPLP. Figure 9 illustrates percent injected dose in lungs of male A/J mice following a single intravenous administration of 303, 314, and 314C with or without 4 mol% CPL4-lk. Figure 10 illustrates percent injected dose per Neuro-2a tumor of male A/J mice following a single intravenous administration of 303, 314, and 314C with or without 4 mol% CPL4-lk. Figure 11 illustrates percent injected dose remaining in plasma of male A J mice following a single intravenous administration of 303, 314, and 314C with or without 4 mol % CPL4-lk. Figure 12 illustrates percent dose per liver of male A/J mice following a single intravenous admimstration of 303,314, and 314C with or without 4 mol% CPL4-lk. Figure 13 illustrates percent injected dose per spleen of male A/J mice following a single intravenous administration of 303, 314, and 314C with or without 4 mol% CPL4-lk. Figure 14 illustrates percent injected dose in kidneys of male A/J mice following a single intravenous administration of 303, 314, and 314C with or without 4 mol% CPL4-lk. Figure 15 illustrates percent injected dose in hearts of male A J mice following a single intravenous administration of 303, 314, and 314C with or without 4 mol% CPL4-lk. Figure 16 illustrates CPL chemistry. Figure 17 illustrates CPL enhance in vitro transfection. DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS I. DEFINITIONS The term "lipid" refers to a group of organic compounds that include, but are not limited to, esters of fatty acids and are characterized by being insoluble in water, but soluble in many organic solvents. They are usually divided into at least three classes: (1) "simple lipids" which include fats and oils as well as waxes; (2) "compound lipids" which include phospholipids and glycolipids; (3) "derived lipids" such as steroids. The term "vesicle-forming lipid" is intended to include any amphipathic lipid having a hydrophobic moiety and a polar head group, and which by itself can form spontaneously into bilayer vesicles in water, as exemplified by most phospholipids. The term "vesicle-adopting lipid" is intended to include any amphipathicϊipid which is stably incorporated into lipid bilayers in combination with other amphipathic lipids, with its hydrophobic moiety in contact with the interior, hydrophobic region of the bilayer membrane, and its polar head group moiety oriented toward the exterior, polar surface of the membrane. Vesicle-adopting lipids include lipids that on their own tend to adopt a non- lamellar phase, yet which are capable of assuming a bilayer structure in the presence of a bilayer-stabilizing component. A typical example is DOPE (dioleoylphosphatidylethanolamine). Bilayer stabilizing components include, but are not limited to, polyamide oligomers, peptides, proteins, detergents, lipid-derivatives, PEG-lipid derivatives such as PEG coupled to phosphatidylethanolamines, and PEG conjugated to ceramides (see, U.S. Patent No. 5,885,613, which is incorporated herein by reference). The term "amphipathic lipid" refers, in part, to any suitable material wherein the hydrophobic portion of the lipid material orients into a hydrophobic phase, while the hydrophilic portion orients toward the aqueous phase. Amphipathic lipids are usually the major component of a lipid vesicle. Hydrophilic characteristics derive from the presence of polar or charged groups such as carbohydrates, phosphato, carboxylic, sulfato, amino, sulfhydryl, nitro, hy rσxy and other like groups. Hydrophobicity can be conferred by the inclusion of apolar groups that include, but are not limited to, long chain saturated and unsaturated aliphatic hydrocarbon groups and such groups substituted by one or more aromatic, cycloaliphatic or heterocyclic group(s). Examples of amphipathic compounds include, but are not limited to, phospholipids, aminolipids and sphingolipids. Representative examples of phospholipids include, but are not limited to, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidic acid, palmitoyloleoyl phosphatidylcholine, lysophosphatidylcholine, lysophosphatidylethanolamine, dipalmitoylphosphatidylcholine, dioleoylphosphatidylcholine, distearoylphosphatid lcholine or dilinoleoylphosphatidylcholine. Other compounds lacking in phosphorus, such as sphingolipid, glycosphingolipid families, diacylglycerøls and β- acyloxyacids, are also within the group designated as amphipathic lipids. Additionally, the amphipathic lipid described above can be mixed with other lipids including triglycerides and sterols. The term "neutral lipid" refers to any of a number of lipid species that exist either in an uncharged or neutral zwitterionic form at a selected pH. At physiological pH, such lipids include, for example, diacylphosphatidylcholine, diacylphosphatidylethanolamine, ceramide, sphingomyelin, cephalin, cholesterol, cerebrosides and diacylglycerols. The term "hydrophopic lipid" refers to compounds having apolar groups thaf include, but are not limited to, long chain saturated and unsaturated aliphatic hydrocarbon groups and such groups optionally substituted by one or more aromatic, cycloaliphatic or heterocyclic group(s). Suitable examples include, but are not limited to, diacylglycerol, dialkylglycerol, N-N-dialkylamino, l,2-diacyloxy-3-aminoρropane and l,2-dialkyl-3- aminoprσpane. The term "diacylglycerolyl" denotes 2-fatty acyl chains, R 1 and R 2 having independently between 2 and 30 carbons bonded to the 1- and 2-position of glycerol by ester linkages. The acyl groups can be saturated or have varying degrees of unsaturation. Diacylglycerol groups have the following general formula: The term "dialϋeylglycerolyl" denotes two C 1 -C3 0 alkyl chains bonded to the 1- and 2-position of glycerol by ether linkages. Dialkylglycerol groups have the following general formula: The term "N-N-dialkylamino" denotes The term "l,2-diacyIoxy-3-aminopropane" denotes 2-fatty acyl chains C1-C30 bonded to the 1- and 2-position of propane by an ester linkage. The acyl groups can be saturated or have varying degrees of unsaturation. The 3-position of the propane molecule has a -NH- group attached. l,2-diacyloxy-3-aminopropanes have the following general formula: The term "l,2-dialkyl-3-aminopropane" denotes 2-alkyl chains (C 1 -C 30 ) bonded to the 1- and 2-position of propane by an ether linkage. The 3-position of the propane molecule has a -NH- group attached. 1 ,2-dialkyl-3-aminopropanes have the following general formula: CH 2 0 C,-C 30 -Alkyl CH— O C r C 30 -Alkyl CH 2 N The term "non-cationic lipid" refers to any neutral lipid as described above as well as anionic lipids. Examples of anionic lipids include, but are not limited to, phosphatidylglycerol, cardiolipin, diacylphosphatidylserine, diacylphosphatidic acid, N- dodecanoyl phosphatidylethanolamines, N-succinyl phosphatidylethanolamines, N- glutarylphosphatidylethanoiamines, lysophosphatidylglycerols, and other anionic modifying groups joined to neutral lipids. The term "cationic lipid" refers to any of a number of lipid species that carry a net positive charge at a selected pH, such as physiological pH. Such lipids include, but are not limited to, N,N-dioleyl-N,N-dimethylammonium chloride ("DODAC"); N-(2,3- dioleyloxy)propyl)-N,N,N-trimethylammonium chloride ("DOTMA"); N,N-distearyl-N,N- dimethylammσnium bromide ("DDAB"); N-(2,3-dioleoyloxy)propyl)-N,N,N- trimethylammonium chloride ("DOTAP"); 3 -(N-( ,N'-dime laminoethane)- carbamoyl)cholesterol ("DC-Choi") and N-(l,2-dimyristyloxyprop-3-yl)-N,N-dimethyl-N- hydroxyethyl ammonium bromide ("DMRIE"). Additionally, a number of commercial preparations of cationic lipids are available which can be used in the present invention. These include, for example, LIPOFECTIN ® (commercially available cationic liposomes comprising DOTMA and 1 ,2-dioleoyl-s«-3-phosphoethanoiamine ("DOPE"), from GΪBCO/BRL, Gran Island, New York, USA); LIPOFECTAMINE ® (commercially available cationic hposomes comprising N-(l-(2,3-dioleyloxy)propyl)-N-(2- (sρerminecarboxamido)ethyl)-N,N-dimethylammoπium trifluoroacetate ("DOSPA") and("DOPE"), from GIBCO BRL); and TRANSFECTAM ® (commercially available cationic lipids comprising dioctadecylamidoglycyl carboxyspermine ("DOGS") in ethanol from Promega Corp., Madison, Wisconsin, USA). The following lipids are cationic and have a positive charge at below physiological pH: DODAP, DODMA, DMDMA and the like. The term "fusogenic" refers to the ability of a liposome or other drug delivery system to fuse with membranes of a cell. The membranes can be either the plasma membrane or membranes surrounding organelles, e.g., endosome, nucleus, etc. Fusogenesis is the fusion of a liposome to such a membrane. The term "dendrimer" includes reference to branched polymers that possess < multiple generations. In dendrimers, each generation creates multiple branch points. The term "ligand" includes any molecule, compound or device with a reactive functional group and includes lipids, amphipathic lipids, carrier compounds, bioaffinit compounds, biomaterials, biopolymers, biomedical devices, analytically detectable compounds, therapeutically active compounds, enzymes, peptides, proteins, antibodies, immune stimulators, radiolabels, fluorogens, biotin, drugs, haptens, DNA, RNA, polysaccharides, liposomes, virosomes, micelles, immunoglobulins, functional groups, targeting agents, or toxins. The foregoing list is illustrative and not intended to be exhaustive. The term "ATTA" or "polyamide" refers to, but is not limited to, compounds disclosed in WO 99/33494 incorporated herein by reference. These compounds include a compound having the formula wherein: R is a member selected from the group consisting of hydrogen, alkyl and acyl; R 1 is a member selected from the group consisting of hydrogen and alkyl; or optionally, R and R 1 and the nitrogen to which they are bound form an azido moiety; R 2 is a member of the group selected from hydrogen, optionally substituted alkyl, optionally substituted aryl and a side chain of an amino acid; R 3 is a member selected from the group consisting of hydrogen, halogen, hydroxy, alkoxy, mercapto, hydrazino, amino and R R , wherein R 4 and R s are independently hydrogen or alkyl; n is 4 to 80; m is 2 to 6; p is 1 to 4; and q is 0 or 1. It will be apparent to those of skill in the art that other polyamides can be used in the compounds of the present invention. As used herein, the term "alkyl" denotes branched or unbranched hydrocarbon chains, such as, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tertbutyl, octa-decyl and 2-methylpentyl. These groups can be optionally substituted with one or more functional groups which are attached commonly to such chains, such as, hydroxyl, bromo, fluoro, chloro, iodo, mercapto or thio, cyano, alkylthio, heterocyclyl, aryl, heteroaryl, carboxyl, carbalkoyl, alkyl, alkenyl, nitro, amino, alkoxyl, amido, and the like to form alkyl groups such as trifluoromethyl, 3- hydroxyhexyl, 2-carboxypropyl, 2-fluoroethyl, carboxymethyL, cyanobutyl and the like. The term "alkylene" refers to a divalent alkyl as defined above, such as methylene (-CH 2 -), propylene (-CH 2 CH 2 CH 2 -), chloroethylene (-CHCICH 2 -), 2-thiobutene (-CH 2 CH(SH)CH 2 CH2-), l-bromo-3-hydroxyl-4-methylρentene (-CHBrCH 2 CH(OH)CH(CH 3 )CH 2 -), and the like. The term "alkenyl" denotes branched or unbranched hydrocarbon chains containing one or more carbon-carbon double bonds. The term "alkynyl" refers to branched or unbranched hydrocarbon chains containing one or more carbon-carbon triple bonds. The term "aryl" denotes a chain of carbon atoms which form at least one aromatic ring having preferably between about 6-14 carbon atoms, such as phenyl, naphthyl, indenyl, and the like, and which may be substituted with one or more functional groups which are attached commonly to such chains, such as hydroxyl, bromo, fluoro, chloro, iodo, mercapto or thio, cyano, cyanoamido, alkylthio, heterocycle, aryl, heteroaryl, carboxyl, carbalkoyl, alkyl, alkenyl, nitro, amino, alkoxyl, amido, and the like to form aryl groups such as biphenyl, iodobipheπyl, methoxybiphenyl, anthryl, bromophenyl, iodophenyl, • chlorophenyl, hydroxyphenyl, methoxyphenyl, for ylphenyl, acetylphenyl, trifluoromethylthiophenyl, trifluoromethoxyphenyl, alkylthiophenyl, trialkylammoniumphenyl, amidophenyl, thiazolylphenyl, oxazolylphenyl, imidazolylphenyl, imidazolylmethylphenyl, and the like. The term "acyl" denotes the -C(O)R group, wherein R.is alkyl or aryl as defined above, such as formyl, acetyl, propionyl, or butyryl. The term "alkoxy" denotes -OR-, wherein R is alkyl. The term "amido" denotes an amide linkage: -C(O)NR- (wherein R is hydrogen or alkyl). The term "amino" denotes an a ine linkage: -NR-, wherein R is hydrogen or alkyl or a terminal NH2. The term "carboxyl" denotes the group -C(O)O-, and the term "carbonyl" denotes the group -C(O)-. The term "carbonate" indicates the group -OC(O)O-. The term "carbamate" denotes the roup -NHC(O)O-, and the term "urea" denotes the group -NHC(O)NH-. The term "phosphoro" denotes the group -OP(O)(OH)O-. The term "basic amino acid" refers to naturally-occurring amino acids as well as synthetic amino acids and/or or amino acid mimetics having a net positive charge at a selected pH, such as physiological pH. This group includes, but is not limited to, lysine, arginine, asparagine, glutamine, histidine and the like. The term "phosphorylethanolamino" denotes the group -OP(O)(OH)OCH 2 CH 2 NH-. The term "phosphorylethanolamido" denotes the group -OP(O)(OH)OCH2CH 2 NHC(O)-. The term "phospho" denotes apentavalent phosphorous moiety -P(O)(OH)O-. The term "phosphoethanolamino" denotes the group -P(O)(OH)OCH 2 CH 2 NH- The term "phosphoethanolamido" denotes the group- P(O)(OH)OCH 2 CH 2 NHC(O)-. The term "ethylene oxide unit" denotes the group -OCH 2 CH 2 -. The term "CPL" refers to a cationic-polymer-lipid e.g. , cationic-PEG-lipid. Preferred CPLs are compounds of Formula I. The abbreviations "HBS" refers to Hepes-buffered saline, "Rho-PE" refers to rhodamine-phosphatidylethanolamine, and "LUVs" refers to "large unilamellar vesicles." The term "array" means at least two of the nouns it modifies e.g. an array of LBSDVs is at least two LBSDVs. The nucleic acids used in the method of the present invention can be isolated from natural sources, obtained from such sources as ATCC or GenBank libraries or prepared by synthetic methods. Synthetic nucleic acids can be prepared by a variety of solution or solid phase " methods. Generally, solid phase synthesis is preferred. Detailed descriptions of the procedures for solid phase synthesis of nucleic acids by phosphite-triester, phosphotriester, and H-phosphonate chemistries are widely available. See, for example, Itakura, U.S. Patent No. 4,401,796; Caruthers, etαl, U.S. Patent Nos.4,458,066 and 4,500,707; Beaucage, etαl, Tetrahedron Lett, 22:1859-1862 (1981); Matteucci, etal,J. Am. Chem. Soc, 103:3185-3191 (1981); Caruthers, et al, Genetic Engineering, 4:1-17 (1982); Jones, chapter 2, Atkinson, et al, chapter 3 and Sproat, etal, chapter 4 in Oligonucleotide Synthesis: A Practical Approach, Gait (ed.), ML Press, Washington D.C. ' (1984); Froehler, et al, Tetrahedron Lett. , 27:469-472 (1986); Froehler, et al, Nucleic Acids Res., 14:5399-5407 (1986); Sinha, et al Tetrahedron Lett., 24:5843-5846 (1983); and Sinha, et al, Nucl Acids Res., 12:4539-4557 (1984), all of which are incorporated herein by reference. A "therapeutic gene" is one whose gene product performs a clinically useful function. For example, where the therapeutic gene is used to transform cancer cells, the therapeutic gene will inhibit the growth of the cancer cells. The therapeutic gene is preferably one whose gene product has low toxicity to non-target tissues, and high toxicity to the disease (e.g. cancer) site. For example, when delivered in the preferred lipid-nucleic acid (e.g., lipid- plasmid particles) particles of the invention, the gene product preferably has greater toxicity to rumor cells than liver or spleen cells, where a large portion of particles can normally be cleared. Alternatively, a therapeutic gene may be delivered to a treatment site, which is not a disease site, but which activates an immunologic or other response which is then favorable for the amelioration of the disease or disorder being treated. Examples of therapeutic genes useful in the methods of the present invention include, but are not limited to, genes for: pro-apoptotic proteins; tumor suppressors (e.g., p53, Rbl (Retinoblastoma), etc.); cytokines (such as Interleukin-2, Interleukin-12, etc.),' heat shock proteins; immunogenic antigens (such as tumor- specific proteins, etc.); genes activated in embryos only; Endostatin, Angiostatin, Thrombospondin, and other inhibitors of angiogenesis; Enzymes used in GDEPT combinations (i.e., suicide genes used in conjunction with a non-toxic pro-drug), such as Thymidine Kinase Irom Herpes simplex virus (HSV-TK); cytosine deaminase; porfirin; TIMP-2 (tissue inhibitor of metallo proteinase-2); plant, bacterial or fungal toxin genes, such as saporin, ricin, diphtheria • toxin, cholera toxin; viral protein genes, such as El A; mutated E6; SV40 Tag or viral protein genes which effect plasmid maintenance and/or copy number, such as EBNA-1; transcription plasmids encoding ribozymes or antisense oligonucleotides, Adenosine Deaminase; CFTR - Cystic Fibrosis; GM-CSF, IL-4, IL-2, IL-7, IL-10; Carcineombryonic Antigen; HLA-B7; TNF; T-Cell Receptor Antibody; CEA; Ig; IFN-g; MART-1; Chimeric Antibody/TCR; Prostate Specific Antigen; anti-erbB-2; Single Chain Antibody; BRCA-1; Alpha- 1 Antitrypsin; p47 phax; Fanconi Anemia Complementation Group C; Glucocerbrosidase; Iduronato-2-Sulfatase; Purine Nulceaside Phosphorylase. Other therapeutic genes are continually being discovered and can be used in the methods of the present invention. Therapeutic genes are generally delivered as part of an expression construct, although other formats are possible. II. XIEID.-BASED SYSTEMIC ELIVE Y- Y IJΞ S e BSDVsi') A. Architecture of the LBSD V The present invention provides lipid-based systemic delivery vehicles useful for delivering payloads to a target, such as a particular tissue site of interest. As such, in one embodiment, the present invention provides lipid-based systemic delivery vehicles ("LBSDV") useful for delivering a payload, such as a therapeutic gene, to a specific tissue site. Suitable LBSDVs of the present invention include, but are not limited to, liposomes, micelles, lipid-nucleic acid particles, SPLPs, virosomes, etc. In certain preferred aspects, the lipid-based systemic delivery vehicles, such as a lipid-nucleic acid particle, have a plurality of constituent parts. In preferred aspects, the constituent parts exclude external targeting moieties such as antibodies or targeting ligands (e.g., cell recognition moieties). In certain aspects, the architecture of the LBSDV can be designed and engineered in such a way as to selectively deliver the LBSDV and thus the payload to a specific tissue site. Tissue sites include, but are not limited to, an organ, bone, a tumor and combinations thereof. Organs include, but are not limited to, heart, spleen, lung, kidney and liver. In one embodiment, the LBSDV is a nucleic acid-lipid particle. The nucleic acid-lipid particle comprises a nucleic acid, such as a therapeutic gene. Suitable nucleic acids include, but are not limited to, plasmids, antisense oligonucleotides, and ribozymes. Nucleic acid is negatively charged and can be combined with a positively charged entity to form a lipid complex suitable for formulation and cellular delivery, vvnen the lipid-based systemic delivery vehicles are used to deliver therapeutic genes or oligonucleotides intended to induce or to block production of some protein within the cell, cationic lipids are included in the formulation, e.g., liposome, micelle, lipid-nucleic acid particle, etc. By designing a lipid- based systemic delivery vehicle having a plurality of constituent parts, and thereafter varying the amounts of each of the plurality of constituent parts, it is possible to impart tissue selectivity to the LBSDV. As used herein "tissue selectivity" means that the LBSDV has a propensity to accumulate or target a specific tissue site, and/or there is expression of a therapeutic gene at a specific tissue site. As explained in detail below, tissue selectivity can be determined and confirmed using both in vivo and in vitro methods. Once tissue selectivity has been imparted to the LBSDV, it is possible to selectively target an active agent to a specific tissue site. In one preferred aspect, the LBSDV is a stable plasmid-lipid particle ("SPLPs"). The SPLPs or nucleic acid-lipid particles of the present invention have a plurality - of constituent-parts, In-a-preferred aspect,. the-SPLP.-CDmprises_meJcJlow parts: (a) a nucleic acid; (b) about 1.0 mole % to about 60 mole % of a cationic lipid; (c) about 0.0 mole % to about 90 mole % of another lipid, such as a non-cationic lipid; (d) about 1.0 mole % to about 30 mole % of a bilayer stabilizing component; (e) about 0.0 mole % to about 90 mole % cholesterol; and (f) about 0.0 mole % to about 15 mole % of cationic polymer lipid. Advantageously, as explained above, it has been discovered that by varying each of the plurality of constituent parts, it is possible to impart tissue selectivity to the LBSDV (e.g., SPLP). In another preferred aspect, the SPLP comprises the following constitutive parts: (a) a nucleic acid; (b) about 1.0 mole % to about 45 mole % of a cationic lipid; (c) about 0.0 mole % to about 90 mole % of a non-cationic lipid; (d) about 1.0 mole % to about 10 mole % of a bilayer stabilizing component; (e) about 0.0 mole % to about 60 mole % cholesterol; and (f) about 0.0 mole % to about 10 mole % of cationic polymer lipid. For example, in certain indications, such as cirrhoses of the liver, a liver tumor, etc., it is desirable to target conventional drugs or nucleic acids to various tissue such as the liver. By architecturally designing the constituent parts of the LBSDV, tissue specific accumulation e.g., Uver accumulation i.e., a propensity to be directed to the liver, is imparted to the LBSDV (e.g. SPLP). An exemplar LBSDV (e.g., SPLP) designed for tumor delivery is illustrated in Figure 1. In this embodiment, the SPLP comprises DOPE, DODAC and PEGC20. Preferably, the ratio of DOPE:DODAC:PEGC20 is about 82.5 mole % to about 7.5 mole % to about 10 mole %. Following systemic administration to Neuro-2A tumor bearing mice, the biodistribution of such SPLPs was determined. Figure 1 shows that it is possible to architecturally design the constituent parts of the LBSDV for tumor, accumulation i.e., a propensity to be directed to the tumor or to have greater expression of a therapeutic gene in the tumor relative to other tissue. Figure 2 shows that is possible using the methods and compositions of the present, invention, to engineer the SPLP to impart liver tissue selectivity. In this embodiment, the LBSDV is designed for tissue targeting, wherein the tissue site is the liver. An exemplar LBSDV (e.g., SPLP) designed for liver delivery is illustrated in Figures 3-4. Figures 3 and 4 show the results of engineering the LB S VD such as SPLPs, to obtain liver selectivity, wherein the SPLP comprises DOPE, CHOL, DODAC, PEGC20, and a CPL. More particularly, the SPLP comprises DOPE:CHOL:DODAC:PEGC20;CPL in a ratio of about 31 mole % to about 45 mole % to about 14 mole % to about 10 mole % to about 4 mole %. In addition to the aforementioned tumor and liver tissues, in still yet another — embodiment, -it- is-possible-to- selectively deliv-er-a-LBSDN_to hearttissne..--- EorJ-αsta-sce, using an LBSDV such as a SPLP wherein the constitutive parts comprise DOPE, DODAC and PEGC 2 0 in a ratio of about 76 mole % to about 14 mole % to about 10 mole % selective heart delivery is achieved. One of the preferred constitutive parts of the LBSDVs of the present invention is a cationic lipid. As explained above, a cationic lipid generally refers to a lipid with a cationic head group situated at or near the liposome membrane (when incorporated in a liposome). CPLs, another preferred constitutive part of the LBSVDs, are distinguished from cationic lipids by the polymer "W" which in certain instances, has the effect of placing the cationic charge at a significant distance from the membrane of the LBSDV. Examples of suitable cationic lipids include, but are not limited to, the following: Ν,Ν-dioleyl-Ν,Ν-dimethylammonium chloride (DODAC), N,N-distearyl-N,N- dimethylammonium bromide (DDAB), N-(l-(2,3-dioleoyloxy)proρyl)-N,N,N- trimethylammonium chloride (DOTAP), N-(l-(2,3-dioleoyloxy)propyl)-N,N- dimethylammoniu chloride (DODAP), N-(l-(2,3-dioleyloxy)propyl)-N,N,N- trimemylammomum chloride (DOTMA), and N,N-dimethyl-2,3-dioleyloxy)propylamine (DODMA), and a mixture of two or more of the above. Other cationic lipids include DC- Chol, (see, Gao, et al, Biochem. Biophys. Res. Comm., 179:280-285 (1991); DDAB; DMRIE; DODAC (see, WO96/10390, which is incorporated herein by reference); DOGS; DOSPA; DOTAP; and DOTMA. In a presently preferred embodiment, NN ' -dioleoyl-N^V- dimethylammonium chloride is used in combination with aphosphatidylethanolamine. In addition, other compositions containing cationic lipids useful in producing lipid-based carriers for gene and oligonucleotide delivery are LIPOFECTIN (U.S. Patents Nos. 4,897,355; 4,946,787; and 5,208,036 issued to Eppstein, et al.) and LIPOFECTACE (U.S. Patent No. 5,279,883 issued to Rose). Both agents, as well as other transfecting cationic lipids, are available from Life Technologies, Inc. in Gaithersburg, Maryland. Another preferred constitutive part of the LBSDVs of the present invention is a cationic polymer lipid ("CPL", see, Figure 16.) In certain applications, the polymer length i.e., molecular weight ("MW) of "W in the CPL is shorter than the normal neutral PEG chains (M.W.2000-5000 Daltons) used for stealth liposomes. In such instances, the shorter polymer of the CPL is about 250 to about 3000 Daltons and more preferably, about 1000 to about 2000 Daltons. A complete description of CPLs is disclosed in U.S Patent Application No. 09/553,639, filed on April 20, 2000, and PCT Publication No. WO 00/62813, published October 26, 2000 which are incorporated herein by reference for all purposes. In another embodiment, the polymer length of "W in the CPL has a larger MW than the normal neutral PEG chains used for stealth liposomes. In such instances, the BSC is for example, a PEGiooo-Kpϊd, and the compound of Formula I has a formula of, for example, A- PEG3400-Y In certain formulations and applications, the type of CPL, i.e. the length of the polymer chain, the amount of cationic charge per molecule, and the amount of such CPL in a given formulation, e.g., SPLP, can be optimized to obtain the desired clearance properties. In certain instances, longer chain CPLs and higher levels of such CPLs in a given formulation result in increased transfection. In other instances, shorter chain CPLs incorporated in the formulations result in longer circulation lifetimes in animals Typically, the CPL is present in the LBSDVs of the present invention at a concentration ranging from about 0.05 mole percent to about 50 mole percent. In a presently preferred embodiment, the CPL is present at a concentration ranging from 0.05 mole percent to about 25 mole percent. In an even more preferred embodiment, the CPL is present at a concentration ranging from 0.05 mole percent to about 15 mole percent. One of ordinary skill in the art will appreciate that the concentration of the CPL can be varied depending on the CPL employed and the rate at which the liposome is to become fusogenic. Another preferred constitutive part of the LBSDVs of the present invention are bilayer stabilizing components (BSC). Suitable BSCs include, but are not limited to, polyamide oligomers, peptides, proteins, detergents, lipid-derivatives, PEG-lipids such as PEG coupled to phosphatidylethanolainine, and PEG conjugated to ceramides (see, U.S. Patent No. 5,885,613, which is incorporated herein by reference). Preferably, the bilayer stabilizing component is a PEG-lipid, or an ATTA-lipid. As discussed herein, in certain preferred instances, the PEG or the ATTA of the BSC has a greater molecular weight compared to the polymer "W" of the CPL. In other instances, the BSC has a smaller molecular weight compared to the "W" of the polymer. The present invention encompasses all such variations. In one embodiment, the LBSDVs of the present invention. comprise: a lipid capable of adopting a non-lamellar phase, yet capable of assuming a bilayer structure in the presence of a bilayer-stabilizing component (such as a PEG-lipid derivative); and a bilayer- stabilizing component reversibly associated with the lipid to stabilize the lipid in a bilayer structure. Such fusogenic liposomes (see, PCT Publication WO 96/40964, published to December 19, 1996) are advantageous because the rate at which they become fusogenic can -be-not only-predeteπnined, hut-also-yaried asreq-iύredPYer a. time- scale of ^fe mmutes to several tens of hours. It has been found, for example, that by controlling the composition and concentration of the bilayer-stabilizing component, one can control the rate at which the BSC exchanges out of the liposome in vivo and, in turn, the rate at which the liposome becomes fusogenic (see, U.S. Patent No.5,885,613). For instance, it has been found that by controlling the length of the lipid acyl chain(s), one can control the rate at which the BSC exchanges out of the liposome in vivo and, in turn, the rate at which the liposome becomes fusogenic. In particular, it has been discovered that shorter acyl chains (e.g., C-8) exchange out of the liposome more rapidly than longer acyl chains (e.g., C-20). Alternatively, by controlling the composition and concentration of the BSC, one can control the rate at which the BSC is degraded, i.e., broken down, by endogenous systems, e.g., endogenous enzymes in the serum, and, in turn, the rate at which the liposome becomes fusogenic. As such, in one embodiment, the lipids which can be used to form the LBSVDs of the present invention are those which adopt a non-lamellar phase under physiological conditions or under specific physiological conditions, e.g., in the presence of calcium ions, but which are capable of assuming a bilayer structure in the presence of a BSC. Such lipids include, but are not limited to, phosphatidylenthanolamines, ceramides, glycolipids, or mixtures thereof. Other lipids known to those of skill in the art to adopt a non- lamellar phase under physiological conditions can also be used. Moreover, it will be readily apparent to those of skill in the art that other lipids can be induced to adopt a non-lamellar phase by various non-physiological changes including, for example, changes in pH or ion concentration (e.g., in the presence of calcium ions) and, thus, they can also be used to form the fusogenic liposomes of the present invention. In a presently preferred embodiment, the LBSVD is prepared from a phosphatidylethanolamine. The phosphatidylethanolamine can be saturated or unsaturated. In a presently preferred embodiment, the phosphatidylyethanolamine is unsaturated. In an equally preferred embodiment, the fusogenic liposome is prepared from a mixture of a phosphatidylethanolamine (saturated or unsaturated) and a phosphatidylserine. In another equally preferred embodiment, the LBSDV is prepared from a mixture of a phosphatidylethanolamine (saturated or unsaturated) and a cationic lipid. In accordance with the present invention, lipids adopting a non-lamellar phase under physiological conditions can be stabilized in a bilayer structure by BSCs which are either bilayer forming themselves, or which are of a complementary dynamic shape. The non-bilayer forming lipid is stabilized in the bilayer structure only when it is associated with, i.e., in the presence of, the BSC. In selecting an appropriate BSC, it is preferable that the BSC be capable of transferring out of the liposome, or of being chemically modified by endogenous systems such that, with time, it loses its ability to stabilize the lipid in a bilayer structure. Only when liposomal stability is lost or decreased can fusion of the liposome with the plasma membrane of the target cell occur. The BSC-lipid, therefore, is "reversibly associated" with the lipid and only when it is associated with the lipid is the lipid constrained to adopt the bilayer structure under conditions where it would otherwise adopt a non-lamellar phase. As such, the BSC-lipids of the present invention are capable of stabilizing the lipid in , a bilayer structure, yet they are capable of exchanging out of the liposome, or of being chemically modified by endogenous systems so that, with time, they lose their ability to * stabilize the lipid in a bilayer structure, thereby allowing the liposome to become fusogenic. Another preferred constituent part of the LBSDVs of the present invention is another lipid such as a non-cationic lipid. Non-cationic lipids include, neutral lipids and anionic lipids. Preferred non-cationic lipids include, but are not limited to, dioleoyl phosphatidylcholine (DOPE), POPC, and egg phosphatidylcholine (EPC). In another embodiment of the present invention, the LBSDV (e.g. liposomes) optionally comprise cholesterol. It has been determined that when cholesterol-free liposomes are used in vivo, they have a tendency to absorb cholesterol from the plasma lipoproteins and ceil membranes. Cholesterol, if included, is generally present at a concentration ranging from 0.2 mole percent to about 90 mole percent and, more preferably, at a concentration ranging from 15 mole percent to about 60 mole percent and most preferably from about 35 mole percent to about 45 mole percent. B. Preparations LBSDVs such as CPL-Liposomes The following discussion refers generally to liposomes; however, it will be readily apparent to those of skill in the art that this same discussion is fully applicable to the other LBSDVs of the present invention (e.g., micelles, virosomes, lipid-nucleic acid particles, etc.). In a preferred method, SPLPs are made in accordance with the teachings of PCT Publication WO 96/40964, published on December 19, 1996. A preferred LBSDV of the present invention is a CPL-liposome. A variety of general methods for making CPL-containing SPLPs (or "CPL-liposomes") are discussed herein. Two general techniques include "post-insertion," that is, insertion of a CPL into for ' example, a pre-for ed liposome vesicle, and "standard" techniques, wherein the CPL is included in the lipid mixture during for example, the liposome formation steps. The post- insertion technique results in liposomes having CPLs mainly in the external face of the liposome bilayer membrane, whereas standard techniques provide liposomes having CPLs on both internal and external faces. In particular, "post-insertion" involves forming LBSDVs (by any method), and incubating the pre-formed vesicles in the presence of CPL under appropriate conditions (usually 2-3 hours at 60°C). Between 60-80% of the CPL can be inserted into the external leaflet of the recipient vesicle, giving final concentrations up to 7 mol % (relative to total lipid). The method is especially useful for vesicles made from phospholipids (which can contain cholesterol) and also for vesicles containing PEG-lipids (such as PEG-Ceramide). ' In an example of a "standard" technique, the LBSDVs of the present invention can be formed by extrusion. In this embodiment, all of the lipids including CPL, are co- dissolved in chloroform, which is then removed under nitrogen followed by high vacuum. The lipid mixture is hydrated in an appropriate buffer, and extruded through two polycarbonate filters with a pore size of 100 nm. The resulting vesicles contain CPL on both internal and external faces. In yet another standard technique, the formation of CPL-LUVs can be accomplished using a detergent dialysis or ethanol dialysis method, for example, as discussed in U.S. Patent Nos. 5,976,567 and 5,981,501, both of which are incorporated herein by reference. C. Use Of LBSDVs As Drug Delivery Vehicles The lipid-based drug formulations and compositions of the present invention (e.g., liposomes, micelles, lipid-nucleic acid particles, virosomes, etc.) are useful for the systemic or local delivery of bioactive agents such as therapeutic agents, prophylactic agents and diagnostic agents. Such delivery systems are described in greater detail in, for example, the following: WO95/32706, U.S. Patent Nos. 5,705,385, 5,976,567, 5,981,501, 60/055,094, 08/856,374, WO99/04819 and WO99/18933 the teachings of all of which are incorporated herein by reference. The following discussion refers generally to liposomes; however, it will be readily apparent to those of skill in the art that this same discussion is fully applicable to the other drug delivery systems of the present invention (e.g., micelles, virosomes, lipid-nucleic acid particles, etc.). For the delivery of therapeutic agents, the LBSDVs can be loaded with a therapeutic agent (conventional or nucleic acids) and administered to the subject requiring treatment. The therapeutic agents, which are administered using the present invention, can be any of a variety of drugs, which are selected to be an appropriate treatment for the disease to be treated or prevented. Often the drug will be an antineoplastic agent, such as vincristine, doxorubicin, mitoxantrone, camptothecin, cisplatin, bleomycin, cyclophosphamide, methotrexate, streptozotocin, and the like. Especially preferred antitumor agents include, for example, actinomycin D, vincristine, viriblastine, cystine arabinoside, anthracyclines, alkylative agents, platinum compounds, antimetabolites, and nucleoside analogs, such as methotrexate and purine and pyrimidine analogs. It may also be desirable to deliver anti- infective agents to specific tissues by the present methods. The compositions of the present invention can also be used for the selective delivery of other drugs including, but not limited to, local anesthetics, e.g., dibucaine and chlorpromazine; beta-adrenergic blockers, e.g., propranolol, timolol and labetolol; antihypertensive agents, e.g., clonidine and hydralazine; anti-depressants, e.g., imipramine, amitriptyline and doxepim; anti-conversants, e.g., phenytoin; antihistamines, e.g., diphenhydramine, chlorphenirimine andpromethazine; antibiotic/antibacterial agents, e.g., gentamycin, ciprofloxacin, and cefoxitin; antifungal agents, e.g., miconazole, terconazole, econazole, isoconazole, butaconazole, clotrimazole, itraconazole, nystatin, nafrifine and amphotericin B; antiparasitic agents, hormones, hormone antagonists, immunomodulators, neurotransmitter antagonists, antiglaucoma agents, vitamins, narcotics, and imaging agents. As mentioned above, the LBSDVs can be used in the delivery of therapeutic genes or oligonucleotides intended for example, to induce or to block production of some protein within the cell. Nucleic acid is negatively charged and may be combined with a positively charged entity to form a lipid complex or a fully encapsulated stable plasmid-lipid particle. Particularly useful antisense oligonucleotides are directed to targets such as c- yc, bcr-abl, c-myb, ICAM-1, C-erb B-2 and BCL-2. The LBSDVs of the present invention are also useful in the delivery of peptides, nucleic acids, plasmid DNA, minichromosomes and ribozymes. Another clinical application of LBSDVs of this invention is as an adjuvant for immunization of both animals and humans. Protein antigens, such as diphtheria toxoid, cholera toxin, parasitic antigens, viral antigens, im unoglobulins, enzymes and histocompatibility antigens, can be incorporated into or attached onto the LBSDVs of the present invention for immunization purposes. LBSDVs of the present invention are also particularly useful as carriers for vaccines that will be targeted to the appropriate lymphoid organs to stimulate an immune response. LBSDVs of the present invention can also be used as a vector to deliver immunosuppressive or immunostimulatory agents selectively to macrophages. In particular, glucocorticoids useful to suppress macrophage activity and lymphokines that activate macrophages can be delivered using the liposomes of the present invention. LBSDVs of the present invention and containing targeting molecules can be used to stimulate or suppress a cell. For example, liposomes incorporating a particular antigen can be employed to stimulate the B cell population displaying surface antibody that specifically binds that antigen. Liposomes incorporating growth factors or lymphokines on the liposome surface can be directed to stimulate cells expressing the appropriate receptors for these factors. Using this approach, bone marrow cells can be stimulated to proliferate as part of the treatment of cancer patients. LBSDVs encapsulated antibodies can be used to treat drug overdoses. The tendency of liposomes having encapsulated antibodies to be delivered to the liver has a therapeutic advantage in clearing substances, such as toxic agents, from the blood circulation. It has been demonstrated that whereas unencapsulated antibodies to digoxin caused intravascular retention of the drug, encapsulated antibodies caused increased splenic and hepatic uptake and an increased excretion rate of digoxin. LBSDVs of this invention also find utility as carriers for introducing lipid or protein antigens into the plasma membrane of cells that lack the antigens. For example, histocompatibiϋty antigens or viral antigens can be introduced into the surface of viral infected or tumor cells to promote recognition and killing of these cells by the immune system. In addition, LBSDVs of the present invention can be used to deliver any product (e.g., therapeutic agents, diagnostic agents, labels or other compounds) including those currently formulated in PEG-derivatized liposomes. In certain embodiments, it is desirable to target the LBSDVs of this invention using targeting moieties that are specific to a cell type or tissue. Targeting of the LBSDVs using a variety of targeting moieties, such as ligands, cell surface receptors, glycoproteins, vitamins (e.g., riboflavin) and monoclonal antibodies, has been previously described (see, e.g., U.S. Patent Nos. 4,957,773 and 4,603,044, the teachings of which are incorporated herein by reference). The targeting moieties can comprise the entire protein or fragments thereof. In some cases, the diagnostic targeting of the LBSDVs can subsequently be used to treat the targeted cell or tissue. For example, when a toxin is coupled to a targeted liposome, the toxin can then be effective in destroying the targeted cell, such as a neoplasmic cell. In another aspect, the present invention provides a method for increasing intracellular delivery of a LBSDV comprising: incorporating into the LBSDV a compound of Formula I, thereby increasing the intracellular delivery of the LBSDV compared to a LBSDV without a compound of Formula I. The compounds of Formula I increase intracellular delivery about 10 fold to about 1000 fold and preferably, about 10 fold to about 100,000 fold. In another aspect, the present invention provides a method of increasing the blood-circulation time of a parenterally administered lipid-based drug formulation, the method comprising: incorporating into the lipid-based drug formulation about 0.1 to 20 mole percent of a compound of Formula I. In other aspects, the present invention provides a method for transfection of a cell with a LBSDV comprising: contacting the cell with a LBSDV having about 0.1 to 20 mole percent of a compound of Formula I. Moreover, a method for increasing the transfection of a cell with a LBSDV comprising: contacting the cell with a LBSDV having about 0.1 to 20 mole percent of a compound of Formula I, whereby the transfection efficiency of the LBSDV is increased compared to the transfection efficiency of a LBSDV without the compound of Formula I. D. Loading and Administering the Liposomes The following discussion refers generally to liposomes; however, it will be readily apparent to those of skill in the art that this same discussion is fully applicable to the Otherdrugdeliveiy-systems-of-the-present-invention^a^.-i micelleSj, virosomes, lipid-nucleic acid particles, etc.). Methods of loading conventional drugs into liposomes include, for example, an encapsulation technique, loading into the bilayer and a transmembrane potential loading method. Again, methods of incorporating nucleic acids into the LBSDVs are disclosed in PCT Publications WO 96/40964, published to December 19, 1996; WO99/05303, published February 4, 1999; and WO99/18933, published April 22, 1999. In one encapsulation technique, the drug and liposome components are dissolved in an organic solvent in which all species are miscible and concentrated to a dry ' film. A buffer is then added to the dried film and liposomes are formed having the drug incorporated into the vesicle walls. Alternatively, the drug can be placed into a buffer and added to a dried film of only lipid components. In this manner, the drug will become encapsulated in the aqueous interior of the liposome. The buffer, which is used in the formation of the liposomes, can be any biologically compatible buffer solution of, for example, isotonic saline, phosphate buffered saline, or other low ionic strength buffers. Generally, the drug will be present in an amount of from about 0.01 ng/mL to about 50 mg/mL. The resulting liposomes with the drug incorporated in the aqueous interior or in the membrane are then optionally sized as described above. Transmembrane potential loading has been described in detail in U.S. Patent No.4,885,172, U.S. Patent No. 5,059,421, and U.S. Patent No. 5,171,578, the contents of which are incorporated herein by reference. Briefly, the transmembrane potential loading method can be used with essentially any conventional drug, which can exist in a charged state when dissolved in an appropriate aqueous medium. Preferably, the drug will be relatively lipophilic so that it will partition into the liposome membranes. A transmembrane potential is created across the bilayers of the liposomes or protein-Iiposome complexes and the drug is loaded into the liposome by means of the transmembrane potential. The transmembrane potential is generated by creating a concentration gradient for one or more charged species (e.g., Na + , K + and/or H + ) across the membranes. This concentration gradient is generated by producing liposomes having different internal and external media and has an associatetø- protσn gradient. Drug accumulation can than occur in a manner predicted by the Henderson- Hasselbach equation. The liposome compositions of the present invention can by administered to a subject according to standard techniques. Preferably, pharmaceutical compositions of the liposome compositions are administered parenterally, i.e., intraperitoneally, intravenously, subcutaneously or intramuscularly. More preferably, the pharmaceutical compositions are administered intravenously by steady infusion. Suitable formulations for use in the present invention are found in Remington 's Pharmaceutical Sciences, Mack Publishing Company, Philadelphia, PA, and 17th ed. (1985). The pharmaceutical compositions can be used, for example, to diagnose a variety of conditions, or treat a diseased state. The diseases include, but are not limited to, inflammation associated with rheumatoid arthritis, post-ischemic leukocyte-mediated tissue damage (reperfusiόn injury), acute leukocyte-mediated lung injury (e.g., adult respiratory distress syndrome), septic shock, and acute and chronic inflammation, including atopic dermatitis and psoriasis. In addition, various neoplasms and tumor metastases can be treated. Preferably, the pharmaceutical compositions are administered intravenously. Thus, this invention provides compositions for intravenous administration which comprise a solution of the liposomes suspended in an acceptable carrier, preferably an aqueous carrier. A variety of aqueous carriers can be used, e.g., water, buffered water, 0.9% isotonic saline, and the like. These compositions can be sterilized by conventional, well known sterilization techniques, or may be sterile filtered. The.resulting aqueous solutions may be packaged for use as is or lyophilized, the lyophilized preparation being combined With a sterile aqueous solution prior to administration. The compositions ma contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions, such as pH adjusting and buffering agents, tonicity adjusting agents, wetting agents and the like, for example, sodium acetate, sodium lactate, sodium chloride, potassium chloride, calcium chloride, sorbitan monolaurate, triethanolamine oleate, etc. The concentration of active ingredient in the pharmaceutical formulations can vary widely, i.e., from less than about 0.05%, usually at or at least about 2-5% to as much as 10 to 30% by weight and will be selected primarily by fluid volumes, viscosities, etc., in accordance with the particular mode of administration selected. For diagnosis, the amount of composition administered will depend upon the particular label used (i.e., radiolabel, fluorescence label, and the like), the disease state being diagnosed and the judgment of the clinician. in. LIBRARIES OF LBSVDs SUCH AS SPLPSs In certain aspects, the present invention provides libraries of LBSVDs and methods for the construction of libraries of LBSDVs using combinatorial techniques. Combinatorial chemistry is a generic term that describes a series of innovative technologies that are designed to automate and simplify the selection, synthesis, and formulation of candidate LBSDVs and combinations thereof into a library. The initial step of a combinatorial process is selection of the constituent parts of compounds such as cationic lipids, non-cationic lipids and CPLs, for inclusion in a library of LBSDVs. A major focus in the formulation of the library is the automation of each step of various operations. In many cases, 96-well or 384-well microtiter plates are used for the dispensing of reagents. Automated systems are available that control temperature of the reactions, volume of reaction reagents, ineπness of the reaction atmosphere, etc. hradditioπ:, highly automated samplmg handling and analysis has been developed to analyze the volume of LBSDVs in the library. Preparation of combinatorial chemical libraries is well known to those of skill in the art. Using similar methods, it is possible to prepare large libraries of LBSDVs. The array or library of the SPLPs comprise a first nucleic acid-lipid particle having a first plurality of constituent parts and a first tissueselectivity; and a second nucleic acid-lipid particle having a second plurality of constituent parts and a second tissue selectivity, wherein the first and second nucleic acid-lipid particles are constitutively different. It is noted that the constituent parts can be the same or different. For example, in one embodiment, the first SPLP comprises a nucleic acid, a cationic lipid, a BSC and cholesterol; and the second SPLP comprises a nucleic acid, a cationic lipid, a BSC, cholesterol and a CPL. Devices for the preparation of combinatorial libraries are commercially available (see, e.g., 357 MPS, 390 MPS, Advanced Chem Tech, Louisville KY, Symphony, Rainin, Woburn, MA, 433A Applied Biosystems, Foster City, CA, 9050 Plus, Millipore, Bedford, MA). A number of well known robotic systems have also been developed for solution phase chemistries. These systems include automated workstations like the automated synthesis apparatus developed by Takeda Chemical Industries, LTD. (Osaka, Japan) and many robotic systems utilizing robotic arms (Zymate II, Zymark Corporation, Hopkinton, Mass.; Orca, Hewlett-Packard, Palo Alto, Calif.) which mimic the manual synthetic operations performed by a person of skill in the art. The nature and implementation of modifications to these devices (if any) so that they can operate as discussed herein will be apparent to skilled artisans. In addition, numerous combinatorial libraries are themselves commercially available (see, e.g., ComGenex, Princeton, N.J., Asinex, Moscow, Ru, Tripos, Inc., St. Louis, MO, ChemStar, Ltd, Moscow, RU, 3D Pharmaceuticals, Exton, PA, Martek Biosciences, Columbia, MD, etc.). IV. DETERMINING TISSUE SELECTIVITY A. In vitro Method In certain embodiments, the present invention provides an in vitro assay method for determining tissue selectivity. The method comprises providing a multiwell plate having a first well and a second well, each well having a tissue type disposed therein. In each well is dispensed a nucleic acid-lipid particle having a first plurality of constituent parts, thereafter, the transfection efficiency of the nucleic acid of the nucleic acid-lipid particles in the desired tissue is determined. In certain aspects, each well in the multiwell plate has the same type of tissue such as liver cells. In this aspect, each well of the multiwell titer plate will have a different LBSVD such as a SPLP dispensed therein, i.e., the plurality of constituent parts of the LBSVD such as a SPLP are varied. Alternatively, each well of the multiwell plate can have a different type of tissue disposed therein. In this aspect, the plurality of constituent parts of the LBSDV are held constant. The tissue or cells are contacted with a nucleic acid-lipid particle for a period of sufficient time, to effectuate transfection. Thereafter, the efficiency of the transfection is determined to evaluate tissue selectivity. B. In vivo Method In certain other embodiments, the present invention provides in vitro assay methods for determining tissue selectivity. As such, the present invention provides an assay method for determining tissue selectivity, the assay method comprising: injecting a lipid- based systemic delivery vehicle having a plurality of constituent parts into the tail vein of a mouse to generate a biodistribution pattern; and analyzing the biodistribution patten thereby determining tissue selectivity. In certain aspects, the mouse is an array of mice, which are administered LBSDVs such as SPLPs with radioactive agents contained therein. After admimstration, biodistribution studies are carried out. Example 1 set forth below illustrates such a study. The accumulation of the radioactive agent, such as the accumulation of [ 3 H]CHE in organs and tumors is determined. Alternatively, the active agent is a gene encoding an enzyme such as luciferase. Thereafter, the propensity of the LBSDV to deliver a 5 certain agent to the target site can be determined. V. DETERMINING NUCLEIC ACID FUNCTIONALITY After tissue selectivity has been imparted into a LBSDV, it is possible to ascertain nucleic acid functionality. As such, the present invention provides a method for 10 determining nucleic acid functionality at a specific tissue site, the method comprising: administering a lipid-based systemic delivery vehicle having tissue selectivity to a mammal, the lipid-based systemic delivery vehicle comprising a nucleic acid; and analyzing the effect . if any, of the nucleic acid on a specific tissue site, thereby determining nucleic acid functionality. T5 Nucleic acids ofa-tftypgsτaay be associated with the LBSDVs-o-fthc-prcscnt- invention and thus can be subsequently delivered to a specific tissue site. These include DNA, RNA, DNA/RNA hybrids (each of which may be single or double stranded), including oligonucleotides such as antisense oligonucleotides, chimeric DNA-RNA polymers, and ribozymes, those having known and unknown functionality, as well as modified versions of 20 these nucleic acids wherein the modification may be in the base, the sugar moiety, the phosphate linkage, or in any combination thereof. Moreover, using the compositions and methods of the present invention it is possible to direct nucleic acid of unknown function to a specific tissue site. From the foregoing it will be clear to those skilled in the art that the LBSVDs 25 of the present invention are useful for both in vitro and in vivo application. Using the methods of the present invention, it is possible to analyze the effect of the nucleic acid on a specific tissue site, i.e., to determining nucleic acid functionality, e.g.; the process of recombinant production of a protein in the liver. After the delivery of the nucleic acid to the specific site, it is possible to test compounds, which modulate the nucleic acid functionality. 30 In certain aspects, the nucleic acids comprises an essential gene or fragment thereof, in which the target tissue cell or cells is deficient in some manner. This can occur where the gene is lacking or where the gene is mutated resulting in under- or over-expression. The nucleic acids can also comprise antisense oligonucleotides. Such antisense oligonucleotides can be constructed to inhibit expression of a target gene. The foregoing^αre examples of nucleic acids that may be used with the present invention, and should not be construed to limit the invention in any way. Those skilled in the art will appreciate that other nucleic acids will be suitable for use in the present invention as well. The following examples serve to illustrate, but not to limit the invention. EXAMPLES Materials Six large-scale luciferase plasmid TCS formulations were prepared. All were labeled with [3-HJ-CHE to facilitate PK and biodistribution. studies. They are as follows: A: 303 DOPE:DODAC:PEGC20::82.5:7.5:10 4(lead systemic SPLP) B: 303 + CPL 303 w/ 4 mol % CPL-4-lk C: 314 DOPE:DODAC:PEGC20::76:14:10 (high cationic lipid) D: 314 + CPL 314 w/ 4 mol % CPL-4-lk E.- 314C DOPE:CHOL:DODAC:PEGC20::31:45:14:10 (cholesterol) F: 314C + CPL 314C w/ 4 mol % CPL-4-lk These formulations were prepared to support in vivo studies. EXAMPLE 1 This Example illustrates the pharmacokinetics and biodistribution of SPLPs following systemic administration to Neuro-2 A tumor bearing mice. Biodistribution and gene expression were examined in parallel to differentiate between effects on gene delivery and transfection. The tumor gene expression study was extended to examine the gene expression resulting from systemic administration of PFV and the effect of calcium pre-incubation on gene expression in vivo. Test Samples/Drugs: All samples are filtered sterilized prior to dilution to working concentration. All samples are provided in sterile crimp top vials.. All vials are labeled with the formulation date, lipid composition, specific activity and DNA concentration. All samples are provided at 0.5 mg/ml DNA. 3[H]CHE is incorporated at 1 μCi/mg Lipid. Sample Treatment Contents A: [3-HjCHE-SPLP SPLP B: [3-HJCHE-SPLP-CPL SPLP w/ CPL-4-lk C: [3-H]CHE-HCL-SPLP SPLP w/ high cationic lipid D: [3-H]CHE-HCL-SPLP-CPL SPLP w/ high cationic lipid and CPL-4-lk E: [3-H]CHE-HCL-CHOL-SPLP SPLP w/ high cationic lipid and cholesterol F: [3-H3CHE-HCL-CHOL-SPLP-CPL SPLP w/ high cationic lipid, cholesterol and CPL-4-lk I. Experimental Design Animals: 140 A/J mice, female, 18-23 g; Experimental Groups: animals housed in cages of 4; 4 animals per group; 30 groups; 120 experimental mice total, 140 to be seeded. II. Procedures Tumor Inoculum: Cells are passaged in vitro as per ATCC. On day 0 of the study, cells are harvested, washed, counted and 1.5 x 10 6 cells are injected subcutaneously in the hind flank of each mouse (injection volume: 50 μl). Treatment: Mice are treated with [3-H]CHE-SPLP (100 μg DNA) formulations administered LV. in a total volume of 200 μl. All treatments are administered once tumor volumes are an appropriate size (approximately day 14). Animals with irregular tumors are removed from the study. Mice receive one treatment only. Endpoints: At the appropriate time-points mice are weighed, sacrificed, blood is collected by cardiac puncture and weighed, organs (liver, lung, spleen, kidney) and tumor are collected into tared fast-prep tubes and evaluated for [3-H]CHE. Formulation and tumor burden are well tolerated however mice exhibiting signs of distress associated with either the treatment or tumor burden are terminated. Data Analysis: 1) Clearance of [3-H]CHE from blood is determined. 2) Accumulation of [3-HjCHE in organs and tumor is determined. m. Results EXAMPLE 2 This Example illustrates luciferase gene expression following systemic administration of SPLP in Neuro2A tumor bearing mice. Jest Samples/Drugs All samples are filtered sterilized prior to dilution to working concentration. All samples are provided in sterile crimp top vials. All vials are labeled with the formulation date, lipid composition, specific activity and DNA concentration. All samples are provided at 0.5 mg/ml DNA. 3[H]CHE is incorporated at 1 μCi/mg Lipid. Sample Treatment Contents A: [3-H]CHE-SPLP SPLP [3-HjCHE-SPLP-CPL SPLP w/CPL-4-lk [3-H]CHE-HCL-SPLP SPLP w/ high cationic lipid [3-H]CHE-HCL-SPLP-CPL SPLP w/ high cationic lipid and CPL-4-lk [3-H]CHE-HCL-CHOL-SPLP SPLP w/ high cationic lipid and cholesterol [3-H]CHE-HCL-CHOL-SPLP-CPL SPLP w/high cationic lipid, cholesterol and CPL-4-lk I. Experimental Design Animals: . 140 A J mice, female, 18-23 g; Experimental Groups: animals housed in cages of 4; 4 animals per group; 21 groups; 84 experimental mice total, 100 seeded. II. Procedures Tumor Inoculum: Cells are passaged in vitro as per ATCC. On day 0 of the study, cells are harvested, washed, counted and 1.5 x 10 Λ 6 cells will be injected subcutaneously in the hind flank of each mouse (injection volume: 50 μl). Treatment: Mice are treated with [3-HjCHE-SPLP (100 μg DNA) formulations admi-nistered.IN.-in a total .volume, of 200 μl....All treatments, are . administered once tumor volumes are an appropriate size (starting approximately day 12). Animals with irregular tumors are removed from the study. Mice receive one treatment only. Endpoints: At the appropriate time-points mice are sacrificed, organs (liver, lung, spleen, kidney) and tumor are collected into tared fast-prep tubes and evaluated for Luciferase gene expression. Formulation and tumor burden are expected to be well tolerated however mice exhibiting signs of distress associated with either the treatment or tumor burden will be temiinated at the discretion of vivarium staff. Data Analysis: 1) Luciferase gene expression. HI Results All publications, patents and patent applications mentioned in this specification are herein incorporated by reference into the specification in their entirety for all purposes. Although the invention has been described with reference to preferred embodiments and examples thereof, the scope of the present invention is not limited only to those described embodiments. As will be apparent to persons skilled in the art, modifications and adaptations to the above-described invention can be made without departing from the spirit and scope of the invention, which is defined and circumscribed by the appended claims.

Claims: WHAT IS CLAIMED IS: 1. A method for identifying a lipid-based systemic delivery vehicle capable of selectively targeting an active agent to a specific tissue site, said method comprising: designing a lipid-based systemic delivery vehicle having a plurality of constituent parts; and varying the- amount-of each- of said plurality of constituent -parts to impart tissue selectivity for said specific tissue site, thereby identifying a lipid-based systemic delivery vehicle capable of selectively targeting an active agent to said specific tissue site. 2. The method for identifying a lipid-based systemic delivery vehicle of claim 1, wherein said lipid-based systemic delivery vehicle is a nucleic acid-lipid particle, 3. The method for identifying a lipid-based systemic delivery vehicle of claim 2, wherein said nucleic acid-lipid particle has a plurality of constituent parts comprising: (a) a nucleic acid; (b) about 1.0 mole % to about 45 mole % of a cationic lipid; (c) about 0.0 mole % to about 90 mole % of another lipid; (d) about 1.0 mole % to about 10 mole % of a bilayer stabilizing component; (e) about 0.0 mole % to about 60 mole % cholesterol; and (f) . about 0.0 mole % to about 10 mole % of cationic polymer lipid. 4. The method for identifying a lipid-based systemic delivery vehicle of claim 1, wherein said active agent is a nucleic acid. 5. The method for identifying a lipid-based systemic delivery vehicle of claim 4, wherein said nucleic acid is selected from the group consisting of a plasmid, an antisense oligonucleotide, and a ribσzyme. 6. The method for identifying a lipid-based systemic delivery vehicle of claim 1, wherein said plurality of constituent parts excludes targeting moieties, 7. The method for identifying a lipid-based systemic delivery vehible of claim 3, wherein said tissue is selected from the group consisting of an organ, bone, a tumor, and combinations thereof. 8. The method for identifying a lipid-based systemic delivery vehicle of claim 7, wherein said organ is selected from the group consisting of heart, spleen, lung, - dney-and-liver. 9. The method for identifying a lipid-based systemic delivery vehicle of claim 8, wherein said organ is the heart. 10. The method for identifying a lipid-based systemic delivery vehicle of claim 9, wherein said nucleic acid-lipid particle comprises DOPE, DODAC and PEGC 2 o. 11. The method for identifying a lipid-based systemic delivery vehicle of . claim 10, wherein the ratio of DOPE:DODAC:PEGC 2 o is about 76 mole % to about 14 mole % to about 10 mole %. 12. The method for identifying a upiα-oaseα systemic delivery verncle of claim 8, wherein said organ is the liver. 13. The method for identifying a lipid-based systemic delivery vehicle of claim 12, wherein said nucleic acid-lipid particle comprises DOPE, CHOL, DODAC, PEGC 20 , and a CPL. 14. The method for identifying a lipid-based systemic delivery vehicle of claim 13, wherein the ratio of DOPE:CHOL:DODAC:PEGC 20 :CPL is about 31 mole % to about 45 mole % to about 14 mole % to about 10 mole % to about 4 mole %. 15. The method for identifying a lipid-based systemic delivery vehicle of claim 7, wherein said tissue is a tumor. 16. The method for identifying a lipid-based systemic delivery vehicle of claim 15, wherein said nucleic acid-lipid particle comprises DOPE, DODAC and PEGC20. 17. The method for identifying a lipid-based systemic delivery vehicle of " claim 15, wherein the ratio of DOPE:DODAC:PEGC 2 o is about 82.5 mole % to about 7.5 mole % to about 10 mole %. 18. A method for delivering a payload to a specific tissue site, said method comprising: administering a-lipid'based--systemie delivery- vehiele-havHig-tissue selecti-vity- for said specific tissue site, wherein said lipid-based systemic delivery vehicle has a plurality of constituent parts, thereby delivering a payload to said specific tissue site. 19. The method for delivering a payload of claim 18, wherein said lipid- based systemic delivery vehicle is a nucleic acid-lipid particle. 20. The method for delivering a payload of claim 18, wherein said nucleic acid-lipid particle has a plurality of constituent parts comprising: (a) a nucleic acid; (b) about 1.0 mole % to about 45 mole % of a cationic lipid; (c) about 0.0 mole % to about 90 mole % of another cationic lipid; (d) about 1.0 mole % to about 10 mole % of a bilayer stabilizing component; (e) about 0.0 mole % to about 60 mole % cholesterol; and (f) about 0.0 mole % to about 10 mole % of cationic polymer lipid. 21. The method for delivering a payload of claim 18, wherein said payload is a nucleic acid. 22. The method for delivering a payload of claim 21, wherein said nucleic acid is selected from the group consistirig of a plasmid, an antisense oligonucleotide, and a ribozyme. 23. The method for delivering a payload of claim 1,8, wherein said plurality of constituent parts excludes targeting moieties. 24. The method for delivering a payload of claim 20, wherein said tissue is selected from the group consisting of an organ, bone and a tumor. 25. The method for delivering a payload of claim 24, wherein said organ is selected from the group consisting of heart, spleen, lung, kidney and liver. 26. The method for delivering a payload of claim 25, wherein said organ is the liver. 27. The method for delivering a payload of claim 26, wherein said nucleic acid-lipid particle comprises DOPE, CHOL, DODAC, PEGC 2 o, and a CPL. 28. The method for delivering a payload of claim 27, wherein the ratio of DOPE:CHOL:DODAC:PEGC 20 :CPL is about 31 mole % to about 45 mole % to about 14 mole % to about 10 mole % to about 4 mole %. 29. A lipid-based systemic delivery vehicle, wherein said lipid-based systemic delivery, vehicle is a nucleic acid-lipid particle, said nucleic acid-lipid particle comprising: (a) a nucleic acid; (b) a cationic lipid; (c) a bilayer stabilizing component; and (d) cholesterol. 30. The lipid-based systemic delivery vehicle of claim 29, further comprising: (e) another lipid. 31. The lipid-based systemic delivery vehicle of claim 32, wherein said another lipid is a non-cationic lipid. 32. The lipid-based systemic delivery vehicle of claim 29, wherein said nucleic acid is selected from the group consisting of a plasmid, an antisense oligonucleotide, and a ribozyme. 33. The lipid-based systemic delivery vehicle of claim 29, wherein said nucleic acid of said nucleic acid-lipid particle is resistant in aqueous solution to degradation with a nuclease. 34. The lipid-based systemic delivery vehicle of claim 29, wherein said cationic lipid is selected from group consisting of N,N-dioleyl-N,N-dimethyIammonium J chloride (DODAC), N,N-distearyl-N,N-dimethylammonium bromide (DDAB), N-(l-&3- dioleoyloxy)propyl)-N,N,N-trimethylammomum chloride (DOTAP), N-(l -(2,3- dioleoyloxy)propyl)-N,N-dimethylammonium chloride (DODAP), N-(l -(2,3- dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTMA), and N,N-dimethyl-2,3- dioleyloxy)ρroρylamine (DODMA), and a mixture of two or more of the above. 35. The lipid-based systemic delivery vehicle of claim 34, wherein said cationic lipid is N,N-dioleyl-N,N-dimethylammomum chloride (DODAC). 36. The lipid-based systemic delivery vehicle of claim 31 , wherein said non-cationic lipid is selected from the group consisting of dioleoyl phosphatidylcholine (DOPE), POPC, and egg phosphatidylcholine (EPC). 37. The lipid-based systemic delivery vehicle of claim 29, wherein said bilayer stabilizing component is a conjugated lipid that inhibits aggregation of said lipid coated nucleic acid particle. 38. The lipid-based systemic delivery vehicle of claim 29, wherein said bilayer stabilizing component is a hydrophilic polymer-lipid. 39. The lipid-based systemic delivery vehicle of claim 29, wherein said hydrophilic polymer-lipid is selected from the group consisting of a PEG-lipid and an ATTA- lipid. 40. The lipid-based systemic delivery vehicle of claim 39, wherein said PEG-lipid is a PEG-ceramide having two acyl chains. 41. The lipid-based systemic delivery vehicle o f claim 40, wherein said PEG-ceramide comprises at least one fatty acid having a chain length of about C_ to about 42. The lipid-based systemic delivery vehicle of claim 29, wherein cholesterol is present in said particle in about 15 % to about 60 % w/w. 43. The lipid-based systemic delivery vehicle of claim 42, wherein cholesterol is present in said particle in about 35 % to about 50 % w/w. 44. The lipid-based systemic delivery vehicle of claim 29, further comprising: (f) a cationic polymer lipid conjugate. 45. The lipid-based systemic delivery vehicle of claim 44, wherein said cationic polymer lipid has the formula: A W Y I wherem: A is a lipid moiety; W is a hydrophilic polymer; Y is a polycationic moiety; and optionally a dansylated lysine spacer between Aand W. 46. The lipid-based systemic delivery vehicle of claim 45, wherein A is a member selected from the group consisting of a diacylglycerolyl moiety, a dialkylglycerolyl moiety, a N-N-dialkylamino moiety, a l,2-diacyloxy-3-aminopropane moiety and a 1,2- dialkyl-3-aminoρropane moiety. 47. The lipid-based systemic delivery vehicle of claim 45, wherein W is a polymer selected from the group consisting of PEG, polyamide, olylactic acid, a hydrophilic polymer, polyglycolic acid, polylactic acid/polyglycolic acid copolymers and combinations thereof, said polymer having a molecular weight of about 250 to about 7000 daltons. 48. The lipid-based systemic delivery vehicle of claim 45, wherein Y comprises at least one basic amino acid or derivative thereof. 49. The lipid-based systemic delivery vehicle of claim 48, wherein Y is a member selected from the group consisting of lysine, arginine, asparagine, glutamine, derivatives thereof and combinations thereof. 50. The lipid-based systemic delivery vehicle of claim 47, wherein W has a molecular weight of about 1000 to about 3400 daltons. 51. The lipid-based systemic delivery vehicle of claim 45, wherein said compound is selected from the group consisting of A- PEGiooo-Y. A- PEG2000-Y and A- PEG 3400 -Y. 52. A method for transfecting a cell with a nucleic acid, said method comprising: contacting said cell with a nucleic acid-lipid particle, said nucleic acid-lipid particle comprising: (a) a nucleic acid; (b) a cationic lipid; (c) a bilayer stabilizing component; and (d) cholesterol, for a sufficient period of time, thereby transfecting said cell with said nucleic acid. 53. The method for transfecting a cell with a nucleic acid of claim 52, further comprising: (e) another lipid. 54. The method for transfecting a ceil with a nucleic acid of claim 53, wherein said another lipid is a non-cationic lipid. 1 55. The method for transfecting a cell with a nucleic acid of claim 52, wherein said nucleic acid is selected from the group consisting of a plasmid, an antisense oligonucleotide, and a ribozyme. 1 56. The method for transfecting a cell with a nucleic acid of claim 52, wherein said nucleic acid of said nucleic acid-lipid particle is resistant in aqueous solution to 3 degradation with a nuclease. 1 57. The method for transfecting a cell with a nucleic acid of claim 52, 2 wherein said cationic lipid is selected from group consisting of N,N-dioleyl-N,N- 3 dimethylammonium chloride (DODAC), N,N-distearyl-N,N-dimethylammonium bromide 4 (DDAB), N-.(l -(2,3-dioleoyloxy)ρropyl)-N,N,N-trimethylammomum chloride (DOTAP), N- 5 (l-(2,3-dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTMA), and N,N- 6 dimethyl-2,3-dioleyloxy)propylamine (DODMA), and a mixture of two or more of the above. 1 . 58. The method for transfecting a cell with a nucleic acid of claim 57, 2. wherein said lipid is N,N-dioleyl-N,N-dimethylammom'um chloride (DODAC). 59. The method for transfecting a cell with a nucleic acid of claim 54, wherein said non-cationic lipid is selected from the group consisting of DOPE, POPC, and EPC. 60. The method for transfecting a cell with a nucleic acid of claim 52, wherein said bilayer stabilizing component is a hydrophilic polymer-lipid. 61. The method for transfecting a cell with a nucleic acid of claim 60, wherein said hydrophilic polymer-lipid is selected from the group consisting of a PEG-lipid and anATTA-lipid. 62. The method for transfecting a cell with a nucleic acid of claim 61, wherein said PEG-lipid is a PEG-ceramide. 63. The method for transfecting a cell with a nucleic acid of claim 61, whpTftin said PKG-ceramide comprises a fatty acid having a chain length of about Cβ to about C 2 o. 64. The method for transfecting a cell with a nucleic acid of claim 52, further comprising: (f) a cationic polymer lipid conjugate. 65. The method for transfecting a cell with a nucleic acid of claim 64, wherein said cationic polymer lipid has the formula: A W Y I wherein: A is a lipid moiety; W is a hydrophilic polymer; and Y is a polycationic moiety; and optionally a dansylated lysine spacer between A and W. 66. The method for transfecting a cell with a nucleic acid of claim 66, wherein A is a member selected from the group consisting of a diacylglycerolyl moiety, a dialkylglycerolyl moiety, a N-N-dialkylamino moiety, a l,2-diacyloxy-3-aminopropane moiety and a l,2-dialkyl-3-aminopropane moiety. 67. The method for transfecting a cell with a nucleic acid of claim 66, wherein W is a polymer selected from the group consisting of PEG, polyamide, olylactic acid, a hydrophilic polymer, polyglycolic acid, polylactic acid/polyglycolic acid copolymers and combinations thereof, said polymer having a molecular weight of about 250 to about 7000 daltons. 68. The method for transfecting a cell with, a nucleic acid of claim 66, wherein Y comprises at least one basic amino acid or derivative thereof. 69. The method for transfecting a cell with a nucleic acid of claim 68, wherein Y is a member selected from the group consisting of lysine, arginine, asparagine, glutamine, derivatives thereof and combinations thereof. 70. The method for transfecting a cell with a nucleic acid of claim 66, wherein W has a molecular weight of about 250 to about 3400 daltons. 71. The method for transfecting a cell with a nucleic acid of claim 66, wherein said compound is selected from the group consisting of A- PEGιooo-Y > A- PEG 2 000-Y andA- PEG 3 4oo-Y. 72. An array of nucleic acid-lipid particles having tissue selectivity, said array of nucleic acid-lipid particles comprising: a first nucleic acid-lipid particle having a first plurality of constituent parts and a first tissue selectivity; a second nucleic acid-lipid particle having a second plurality of constituent parts and a second tissue selectivity, wherein the first and second nucleic acid-lipid particles are constitutively different. 73. The array of nucleic acid-lipid particles of claim 72, wherein said first plurality of constituent parts comprises : (a) a nucleic acid; (b) . about 1.0 mole % to about 45 mole % of a cationic lipid; (c) about 0.0 mole % to about 90 mole % of a non-cationic lipid; (d) about 1.0 mole % to about 10 mole % of a bilayer stabilizing component; (e) about 0.0 mole % to about 60 mole % cholesterol; and (f) about 0.0 mole % to about 10 mole % of cationic polymer lipid. 74. The array of nucleic acid-lipid particles of claim 72, wherein said second plurality of constituent parts comprises: (a) a nucleic acid; (b) about 1.0 mole % to about 45 mole % of a cationic lipid; (c) about 0.0 mole % to about 90 mole % of a non-cationic lipid; (d) about 1.0 mole % to about 10 mole % of a bilayer stabilizing component; (e) about 0.0 mole % to about 60 mole % cholesterol; and (f) about 0.0 mole % to about 10 mole % of cationic polymer lipid. 75. An assay method for determining tissue selectivity, said assay method comprising: injecting a lipid-based systemic delivery vehicle having a plurality of constituent parts into the tail vein of a mouse to generate a biodistribution pattern; and analyzing said biodistribution patten, thereby determining tissue selectivity. 76. The assay method for determining tissue selectivity of claim 75, wherein said mouse is an array of mice. 77, The assay method for determining tissue selectivity of claim 75, wherein said lipid-based systemic delivery vehicle comprises a labeled agent. 78. The assay method for determining tissue selectivity of claim 77, further comprising: dissecting said mouse to determine the presence of said labeled agent. 79. The assay method for determining tissue selectivity of claim 75, . wherein said biodistribution pattern is analyzed by gene expression of a nucleic acid in said lipid-based systemic delivery vehicle. 80. An assay method for determining tissue selectivity, said assay method comprising: providing a multiwell plate having a first well and a second well, each well having a tissue type disposed therein; dispensing an array of nucleic acid-lipid particles, said array of nucleic acid- lipid particles comprising a first nucleic acid-lipid particle having a first plurality of constituent parts dispensed in said first well and a second ' nucleic acid-lipid particle having a second plurality of constituent parts dispensed in said second well; and determining transfection efficiency of the nucleic acid of said array of nucleic acid-lipid particles in said tissue. 81. The assay method for determining tissue selectivity of claim 80, wherein said tissue type in said first well is the same type as the tissue type in said second well. 82. The assay method for determining tissue selectivity of claim 81, wherein said first and second nucleic acid-lipid particles are constitutively different. 83. The assay method for determining tissue selectivity of claim 80, wherein said tissue type in said first well is different than the tissue type in said second well. 84. The assay method for determining tissue selectivity of claim 83, wherein said first and second nucleic acid-lipid particles are constitutively similar. 85. The assay method for deteπnining tissue selectivity of claim 80, wherein said tissue type is selected from the group consisting of an organ, bone and a tumor. 86. A method for determining nucleic acid functionality at a specific tissue site, said method comprising: administering to a mammal a lipid-based systemic delivery vehicle having tissue selectivity for said specific tissue site, said lipid-based systemic delivery vehicle comprising a nucleic acid; and analyzing the effect if any of said nucleic acid on said specific tissue site, thereby determining nucleic acid functionality. 87. The method for deteπnining nucleic acid functionality of claim 86, wherein said nucleic acid is selected from the group consisting of a plasmid, an antisense oligonucleotide, and a ribozyme. 88. The method for determining nucleic acid functionality of claim 86, wherein the effect of said nucleic acid is analyzed at a site distal to said specific tissue site. 89. The method for determining nucleic acid functionality of claim 86, wherein said lipid-based systemic delivery vehicle is a nucleic acid-lipid particle, said nucleic acid-lipid particle comprising: (a) a nucleic acid; (b) a cationic lipid; (c) a bilayer.stabilizing component; and (d) cholesterol. ' 90. The method for determining nucleic acid functionality of claim 89, further comprising: (e) another lipid. . 91. The method for transfecting a cell with a nucleic acid of claim further W, comprising: (i) a cationic polymer lipid * conjugate: 92. The method for deteπnining nucleic acid functionality of claim 86, wherein said tissue site is selected from the group consisting of an organ, bone and a tumor. 93. The method for determining nucleic acid functionality of claim 92, wherein said organ is selected from the group consisting of heart, spleen, lung, kidney and liver. 94. The method for determining nucleic acid functionality of claim 93, wherein said organ is the liver. 95. The method for determining nucleic acid functionality of claim 94, wherein said nucleic acid-lipid particle comprises DOPE, CHOL, DODAC, PEGC 2 0, and a CPL. 96. ' The method for determining nucleic acid functionality of claim 95, wherein the ratio of DOPE:CHOL:DODAC:PEGC 20 :CPL is about 31 mole % to about 45 mole % to about 14 mole % to about 10 mole % to about 4 mole %.

Inventors: CULLIS PIETER R, FENSKE DAVID B, MACLACHLAN IAN, CULLIS, PIETER, R., FENSKE, DAVID, B., MACLACHLAN, IAN
Applicants: CULLIS PIETER R, FENSKE DAVID B, INEX PHARMACEUTICALS CORP, MACLACHLAN IAN, UNIV BRITISH COLUMBIA, CULLIS, PIETER, R., FENSKE, DAVID, B., INEX PHARMACEUTICALS CORPORATION, MACLACHLAN, IAN, THE UNIVERSITY OF BRITISH COLUMBIA
Application year: 2001
Main classification: A61K9
IPC codes: A61K9, A61K31, A61K47, A61K48, A61P9, A61P11, A61P17, A61P19, A61P29, A61P35, A61P37