WO2008033253A2 - Liposome complexes containing pharmaceutical agents and methods - Google Patents

Abstract

Liposome complexes are provided for site-specific delivery of pharmaceutical agents with improved targeting efficiency. The liposome complexes include a pharmaceutical agent associated with the liposome; a sialic acid-containing molecule associated with the liposome; and optionally a targeting agent attached to the sialic acid-containing molecule. The invention also provides methods of making liposome complexes and their in vivo administration.

Description

LIPOSOME COMPLEXES CONTAINING PHARMACEUTICAL AGENTS AND METHODS

This application claims the benefit of U.S. Provisional Application No. 60/843,808, filed 11 September 2006, which is hereby incorporated by reference in its entirety.

BACKGROUND

Liposomes, also known as vesicles, have been designed to encapsulate pharmacological agents useful for in vivo purposes such as the diagnosis and treatment of various diseases and conditions. These cargo-carrying liposomes have experimentally shown potential for being site-specific carrier systems for a variety of such agents. Agents so delivered to designated sites in vivo demonstrate significantly enhanced therapeutic indices. Concurrently, a decrease in unwanted side effects and wasted portions of a pharmaceutical dosage are achieved. The advantages of encapsulation have been offset, however, by the deleterious effects of the body's reticuloendothelial system (RES), mainly the liver and spleen. The reticuloendothelial system acts to screen the body's circulation. The reticuloendothelial system will gradually scavenge from the circulation all material it considers foreign and unwanted. Liposomes have certain physical characteristics which render them susceptible to removal by the reticuloendothelial system. Once recognized, liposomes, whether given a site-specific molecule for so- called "targeted" delivery or not, are quickly phagocytosed by the reticuloendothelial system along with their cargo.

From the foregoing, it will be appreciated that what is needed in the art is a liposome composition that delivers an encapsulated pharmaceutical agent into specific tissues (e.g., organs), particularly the brain, with reduced or no scavenging by the body's reticuloendothelial system. o uivuvi/vix. i KJΓ i ΠE AΠ v JJ,Π i XKJIV Liposome complexes are provided for site-specific delivery of pharmaceutical agents (e.g., therapeutic or diagnostic agents) to a targeted site with improved efficiency. Such liposome complexes include liposomes having associated therewith one or more types of sialic acid-containing molecules, preferably the sialic acid-containing molecules are attached to the external surface of the liposomes for surface modification. In certain preferred embodiments, the sialic acid-containing molecules form linkers for attachment of one or more targeting agents to the liposomes. In certain preferred embodiments, one or more pharmaceutical agents are located within the internal compartment of the liposome.

The liposome complexes of the present invention are particularly designed for delivering pharmaceutical agents across the bloόd-brain barrier, although they can also be used to target other organs such as the heart, liver, kidney, pancreas, etc., or other tissues (e.g., skin, spine). The therapeutic management of almost all debilitating neurological and psychiatric disorders is largely hindered by the restricted access of pharmaceutical agents to the brain, imposed by the microvascular endothelial blood-brain barrier (BBB). A limited permeability of the BBB, only to pharmaceutical agents exhibiting high lipophilicity and molecular masses of less than 500 Daltons, mandates the use of craniotomy-based techniques for delivering other promising therapeutic candidates (e.g., injecting the pharmaceutical agent either directly into a specific site within the brain or into the ventricles carrying the cerebrospinal fluid). Besides the invasive nature of craniotomy, these techniques fail to accomplish widespread distribution of the pharmaceutical agent in the brain that can be attained using a trans-vascular approach. Current strategies, used for administering BBB-impermeable therapeutics via the trans- vascular route, involve co-infusion of a therapeutic with an osmotic agent or conjugation to vectors that enable an absorptive- or receptor-mediated transcytosis across the BBB. Such methods are generally undesirable because they allow for an adverse, non-specific influx of plasma constituents into the brain, generalized breakdown of the BBB, peripheral vascular permeability, generation of antibodies (antigenicity), generation of an immune response (immunogenicity), and/or inactivation of the pharmaceutical agent.

Preferred liposome complexes of the present invention enable a trans- vascular access and widespread distribution of a broad range of pharmaceutical chemical-based compounds, into the brain. In preferred embodiments, liposomal encapsulation protects the pharmaceutical agent from enzymatic degradation in vivo. In addition, in certain preferred embodiments, conjugation of anionic, non- immunogenic polysialic acids (PSAs) to the liposomal surface reduces and/or restricts the reticuloendothelial uptake of the liposomes and extends their viable time in the bloodstream. In certain preferred embodiments, binding the liposomal PSAs to one or more targeting agents (e.g., monoclonal antibodies, antibody fragments, or peptide analogues that specifically recognize receptors expressed in the brain micro vasculature) facilitates entry into the brain.

In one embodiment, the liposome complex includes: a liposome having an exterior surface and an internal compartment; a pharmaceutical agent (e.g., a therapeutic agent or a diagnostic agent) associated with the liposome (in certain embodiments, located within the internal compartment of the liposome); a sialic acid-containing (e.g., terminated) molecule associated with the liposome (in certain embodiments, the sialic acid-containing molecule is attached at the external surface of the liposome); and a targeting agent; wherein the sialic acid-containing molecule forms a linker between the targeting agent and the external surface of the liposome.

In another embodiment, the liposome complex includes: a liposome having an exterior surface and an internal compartment; a pharmaceutical agent (e.g., a therapeutic agent or a diagnostic agent) associated with the liposome (in certain embodiments, located within the internal compartment of the liposome); a sialic acid-containing (e.g., terminated) molecule associated with the liposome (in certain embodiments, the sialic acid-containing molecule is attached at the external surface of the liposome); and optionally a targeting agent; wherein the sialic acid-containing molecule comprises polysialic acid having a degree of polymerization of at least 8 (particularly when the complex does not include a targeting agent).

In certain embodiments, the liposome is prepared from phospholipids selected from the group consisting of phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholines, phosphatidylglycerol, phosphatidic acid, phosphatidylmethanol, cardiolipin, ceramide, cholesterol, cerebroside, lysophosphatidylcholine, D-erythrosphingosine, sphingomyelin, dodecyl phosphocholine, N-biotinyl phosphatidylethanolamine, and combinations thereof. a lipid head-group (e.g., a phospholipid) and a sialic acid group. In certain embodiments, the sialic acid-containing molecule is selected from the group consisting of capsular polysialic acid, sialic acid-containing gangliosides, colominic acid, and combinations thereof. Preferably, the sialic acid-containing molecule is a capsular polysialic acid.

In certain embodiments, the targeting agent is selected from the group consisting of peptides, peptide analogs, antibodies, antibody fragments, small organic or inorganic molecules, and combinations thereof. Preferably, the targeting agent is a compound that specifically recognizes receptors expressed in the brain microvasculature.

In certain embodiments, the liposome complex includes two or more different pharmaceutical agents.

The present invention also provides a pharmaceutical composition that includes a liposome complex of the present invention and an optional pharmaceutically acceptable carrier. In certain embodiments, a pharmaceutical composition can also include a pharmaceutical agent that is not a part the liposome complex, which may be the same or different than the pharmaceutical agent associated with the liposome. In certain embodiments, a pharmaceutical composition can crosslink, gel, or change in viscosity on or after administration to a subject. In certain embodiments, a pharmaceutical composition can provide for delayed or extended release of the liposome complex after administration to a subject.

In certain embodiments, a pharmaceutical composition can include two or more different liposome complexes, each containing different pharmaceutical agents and/or targeting moieties.

The present invention also provides methods of treating and/or preventing an affliction by administering a liposome complex of the present invention or pharmaceutical composition containing such complex to a subject. The affliction can be a psychiatric disorder, a neurological disorder, a disease affecting and/or originating in the brain, a disorder of the cardiac system, a disorder of the hepatic system, a disorder of the vascular system, a disorder of the orthopedic system, or combinations thereof. agent to a subject by administering a liposome complex of the present invention or pharmaceutical composition containing such complex to the subject.

The present invention also provides methods of making a liposome complex. One method includes: preparing a liposome having an exterior surface and an internal compartment, a pharmaceutical agent associated therewith, and a sialic acid- containing molecule associated therewith; and attaching a targeting agent to the sialic acid-containing molecule; wherein sialic acid-containing molecule forms a linker between the targeting agent and the external surface of the liposome. Another method includes: preparing a liposome having an exterior surface and an internal compartment, a pharmaceutical agent associated therewith, and a sialic acid-containing molecule associated therewith; and optionally attaching a targeting agent to the sialic acid-containing molecule; wherein the sialic acid- containing molecule comprises polysialic acid having a degree of polymerization of at least 8.

In one method, preparing a liposome having an exterior surface and an internal compartment and a pharmaceutical agent associated therewith involves encapsulating the pharmaceutical agent within the internal compartment of the liposome. Preferably, the step of preparing a liposome having an exterior surface and an internal compartment and a sialic acid-containing molecule associated therewith involves attaching a sialic acid-containing molecule to the external surface of the liposome during or after encapsulation of the pharmaceutical agent. Preferably, the method further includes a step of attaching a targeting agent to the sialic acid-containing molecule before, during, or after attaching the sialic acid- containing molecule to the external surface of the liposome.

Definitions

As used herein, "sialic acid-containing molecule associated with the liposome" means that such molecules are included within the structure of the liposome, through covalent bonds or through non-covalent interactions. For example, a polysialic acid unit could be incorporated into a liposome through non- bonded interactions by the presence of a lipid or lipid-like head group, as is found in the naturally occurring capsular polysialic acids. that such agent can be included within the structure of the liposome in a variety of manners. For example, association can be accomplished through encapsulation within the internal compartment of the liposome, or through attachment to the outer surface of the liposome through bonding or nonbonding interactions, or through intercalation between the double layer of lipid head groups, or through other methods known in the art of drug delivery using liposomes.

As used herein, "liposome" refers to a vesicle (generally spherical in shape) in an aqueous medium, formed by a lipid bilayer enclosing an aqueous compartment.

As used herein, "sialic acid" refers to the N-acyl derivative of neuraminic acid.

As used herein, "targeting agent" refers to a compound that binds to a specific site in the body. As used herein, "pharmaceutical agent" refers to a therapeutic agent and/or a diagnostic agent.

As used herein, the term "comprises" and variations thereof do not have a limiting meaning where these terms appear in the description and claims. As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. Thus, for example, a liposome complex that comprises "a" pharmaceutical agent can be interpreted to mean that the liposome complex includes "one or more" pharmaceutical agents.

The words "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1 , 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

The teπn "and/or" means one or all of the listed elements (e.g., preventing and/or treating an affliction means preventing, treating, or both treating and preventing further afflictions). disclosed embodiment or every implementation of the present invention. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a representation of a polysialylated immuno-liposome encapsulating a therapeutic, expression plasmid DNA, and having the distal ends of liposome-conjugating polysialic acid (PSA) strands conjugated to a monoclonal antibody, which specifically recognizes a BBB endothelial receptor.

FIG. 2 depicts the size distribution of liposome complexes with a mean size of 150 nm (standard deviation of 30 nm). These complexes encapsulate a plasmid DNA that enables the expression of green fluorescent protein (GFP), and incorporate sialic acid-containing molecules (gangliosides), which are further conjugated to a monoclonal antibody that specifically recognizes the transferrin receptor known to express at high levels in the BBB endothelium. FIG. 3 is a representative of an agarose gel electrophoresis performed in order to confirm the encapsulation of plasmid DNA by liposome complexes. FIG. 4 is a representative transmission electron microscopy image of exemplary liposome complexes of the present invention. The transferrin receptor- targeting monoclonal antibodies tethered to sialic acid-containing molecules are bound by an anti-mouse secondary antibody, which is in turn conjugated 10 nm gold. The position of gold particles indicates the association of transferrin receptor- targeting monoclonal antibody with the liposome complexes.

FIG. 5 demonstrates the expression of GFP in mouse Neuro2a neuroblastoma cells upon treatment with liposome complexes that encapsulate the GFP-expressing plasmid DNA. Image A depicts the GFP-expressing cells brightly lit upon excitation required for visualizing GFP. Image B is a corresponding bright- field image. Scale bar: 10 microns or micrometers (μm). The invention provides a liposome complex for delivering a pharmaceutical agent (e.g., a diagnostic and/or therapeutic agent), and preferably a therapeutic agent, to a targeted area in a subject. The liposome complex includes a liposome having an exterior surface and an internal compartment, at least one pharmaceutical agent associated with the liposome (in certain embodiments, one or more pharmaceutical agents are located within the internal compartment of the liposome), and at least one sialic acid-containing molecule that is associated with the liposome. In certain embodiments, the liposome complex also includes at least one targeting agent, wherein the at least one targeting agent binds to a specific site in the body of the subject and is attached to (e.g., covalently bonded to) the at least one sialic acid-containing molecule (i.e., the sialic acid-containing molecule forms a linker between the targeting agent and the external surface of the liposome).

Liposome complexes of the present invention can be used to target various organs (e.g., brain, heart, liver, kidney, pancreas) or other tissues of the body (e.g., skin, spine). For example, a liposome complex can be administered to a subject for preferential uptake by an organ of interest.

The liposome complexes of the present invention are particularly designed for delivering pharmaceutical agents across the blood-brain barrier. As discussed above, the blood-brain barrier (BBB) poses a central problem in the unresponsiveness of almost all debilitating neurological disorders to conventional drug therapy.

The liposomes can form nanocontainers, such as nanoparticles, and are commonly used for encapsulation of pharmaceutical agents. They are typically spherical in shape, and preferably have an average particle size (i.e., the average of the longest dimension, which is the diameter for spherical particles) of no greater than 1000 nanometers (nm). Liposomes having an average particle size of 50 nm are desired, although other sizes may also be useful for crossing the blood brain barrier. Suitable types of liposomes may be prepared from, for example, phospholipids selected from the group consisting of phosphatidyl serine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholines, phosphatidylglycerol, phosphatidic acid, phosphatidylmethanol, cardiolipin, ceramide, cholesterol, cerebroside, lysophosphatidylcholine, D-erythrosphingosine, synthetic analogs of these molecules, derivatives of these molecules, and combinations thereof.

Liposomes may be prepared according to any of the well known conventional processes. For example, liposomes may be made by depositing a thin film of lipid on the inner wall of a flask, adding an aqueous phase, and shaking vigorously (e.g., by hand). Another method may include, for example, sonication of a lipid film in an aqueous solution, followed by extrusion through a series of filters (e.g., of decreasing pore size). Yet another method of making liposomes is to dialyze an aqueous solution of lipids in the presence of a detergent such as sodium cholate. As the detergent is depleted, the lipids form liposomes. Still another method is based on high pressure homogenization of a lipid solution using commercially available equipment. Additional methods may include, for example, re-hydration of freeze-dried vesicles and reverse-phase evaporation. Descriptions and protocols for these methods are well known to those of skill in the art. See, for example,

Liposomes: A Practical Approach (2^nd edition, 2003), edited by Vladimir Torchilin and Volkmar Weissig, Oxford University Press, Oxford, UK. Materials for making liposomes are commercially available, for example, from Avestin Inc., Ottawa, Canada, Microfluidics, a division of MFIC Corp., Newton, MA, and Harvard Apparatus, a Harvard Bioscience, Inc. company, Holliston, MA.

One or more pharmaceutical agents may be associated with a liposome, such as encapsulated within a liposome, using a wide variety of mechanisms, including encapsulation within the internal compartment of the liposome, or attachment to the outer surface of the liposome through bonding or nonbonding interactions, intercalation between the double layer of lipid head groups, and the like. For example, methods of associating one or more pharmaceutical agents with liposomes include, but are not limited to: encapsulating an agent within the aqueous core of the liposome, which can occur by preparing the liposome in the presence of the agent; causing a non-bonded interaction (e.g., van der Waals) between an agent and the hydrophilic tail of a lipid used to form the liposome, either within the core or at the outer surface of the liposome; causing an interaction between an agent and the lipid head group of a lipid used to form the liposome; intercalating an agent between the double layer of lipid head groups in a liposome; bonding (e.g., covalent, ionic, or hydrogen bonding) an agent to a molecule that makes up the structure of the and/or causing complex formation between an agent and a cationic salt that may be a part of the structure of the liposome.

The pharmaceutical agents employed do not impose any significant limitation upon the scope of the invention. A wide variety of agents can be used. Such agents that are particularly susceptible to liposomal entrapment or association are useful. Such agents can be for therapeutic and/or diagnostic purposes. Such agents include oligonucleotide-based compounds (e.g., DNA and RNA), amino acid- based compounds (e.g., proteins and peptides), polysaccharides, small molecule organic and inorganic compounds, organometallic species, and the like. Various combinations of pharmaceutical agents may be incorporated into liposomes according to the present invention.

Therapeutic agents include, for example, antibiotics, antidepressants, antitumorigenics, antivirals, cytokines, hormones, imaging agents, neurotransmitters, nucleic acids, stimulants, regulating agents that turn genes and/or protein production on or off, and the like. Suitable therapeutic agents may include, for example, poly-functional alkylating agents, such as mechlorethamine, chlorambucil, melphalan, thiotepa, busulfan, cyclophosphamide, ifosfamide; antimetabolites, such as methotrexate, 6-mercaptopurme, 6-thioguanme, 5-fluorouracil, 5-fluorodeoxyuridine, cytarabine, fludarabine, 2-chlorodeoxyadenosine, 2-deoxycoformycin, genicitabine: antibiotics, such as doxorubicin, bleomycin, dactinomycin, daunorubicin, plicamycin, mitomycin C, mitoxantrone; steroid and hormonally active compounds such as the androgen, fluoxymesterone; the antiandrogen, flutamide; the estrogens, ethinyl estradiol and diethylstilbestrol; the antiestrogen, tamoxifen; the progestational agent, megestrol acetate; the luteinizing hormone-releasing hormone agonist, leuprolide; the aromatase inhibitor, aminoglutethimide; the adrenal cortical compound, dexamethasone; miscellaneous drugs, such as asparaginase, altretaimine, carmustine, lomustine, steptozotocin, mitotane, dacarbazine, hydroxyurea, etoposide, cisplatin, carboplatin, procarbazine, vinblastine, vincristine, levamisole, cis-retinoic acid, paclitaxel, docetaxel; and biologic agents, such as α-interferon, β-interferon, interferon-γ tumor necrosis factor, erythropoietin, granulocyte colony-stimulating factor, granulocyte macrophage colony-stimulating combinations thereof.

Diagnostic agents include, for example, metals (e.g., gadolinium) that can be detected by MRI, agents for enhancing radiopacity (e.g., barium), radioisotopes, and the like. Techniques of using liposomes with diagnostic agents are known in the art and described, for example, in Arti, J.Clin. Oncol., 24, 3299-3308 (2006).

In certain embodiments, the number of pharmaceutical agents associated with (e.g., encapsulated within) the liposomes may vary from one to many, depending on the desired result (e.g., the affliction being treated). In certain embodiments, liposome complexes may include at least one pharmaceutical agent at a suitable level to produce the desired result.

One or more sialic acid-containing molecules are associated with liposomes according to the present invention. In certain embodiments, the sialic acid- containing molecule(s) are attached to the liposome external surface after the liposomes are prepared. Alternatively, sialic acid-containing molecules, such as polysialic acids, can be used to make the liposomes and thereby be incorporated into the structure of the liposome during preparation of the liposome. Various combinations of such mechanisms of associating sialic acid-containing molecules can be used in any one liposome complex. As a result of incorporation of sialic acid-containing molecule(s), particularly through surface modification of the liposomes, the liposome complexes of the present invention experience less scavenging by the body's reticulo-endothelial system than occurs with liposomes that do not have sialic acid-containing molecules associated therewith. While not being limited to theory, it is believed that while the liposomal encapsulation reduces and even prevents enzymatic degradation of the pharmaceutical agent in vivo, the hydrophilic nature of the sialic acid-containing molecule forms a protective "watery" coating around the liposome, thereby providing protection from reticulo-endothelial uptake. Advantageously, this combination of liposome and sialic acid surface modification increases the blood residence time of the pharmaceutical agent. Also, by virtue of their endogenous expression in mammals, sialic acid-containing molecules present a negligible risk of generating antigenic or immunogenic responses and are generally biodegradable, in contrast to currently employed polymers such as poly(ethylene glycol). link one or more targeting agents to the external surface of the liposome.

Alternatively, one or more targeting agents can be directly attached to the liposomes or attached to linkers other than sialic acid-containing molecules. Various combinations of attaching targeting agents to the liposomes can be used in any one liposome complex.

The sialic acid-containing molecule, may include, for example, a wide variety of materials that include sialic acid, polysialic acid, sialic acid analogues and polysialic acid analogues (such analogues are materials containing synthetically modified sialic acid), phospholipids and polysaccharides containing sialic acid units

(including those containing polysialic acid at a chain terminus), and the like.

Various combinations of different sialic acid-containing molecules can be used if desired.

In certain embodiments, the sialic acid-containing molecule may be oligomeric or polymeric and include at least 2 sialic acid units, more preferably at least 4 sialic acid units, and even more preferably at least 8 sialic acid units. Such materials are also referred to as "polysialic acids," or polymers of sialic acid whose degree of polymerization (DP) is preferably at least 2, more preferably at least 4, and even more preferably at least 8. There is no necessary limitation to the upper limit of the number of sialic acid units. Generally, such polymers could be as large as naturally occurring polysialic acids. In some embodiments, the number of sialic acid units is no greater than 1000, and in some embodiments no greater than 200. In certain embodiments, the sialic acid-containing molecule includes, for example, a lipid head-group and a sialic acid group. The lipid head-group may be a terminal phospholipid group for insertion into the lipid layer. Suitable terminal phospholipids groups may include, for example, those listed above, and combinations thereof.

Suitable examples of sialic acid-containing molecules may include, for example, capsular polysialic acid, sialic acid-containing gangliosides, colominic acid (i.e., a polysialic acid in which all sialic acid residues are linked in 2->8 fashion), and combinations thereof. Preferably, the sialic acid-containing molecules are anionic polymers of N-acetylneuraminic acid.

Capsular polysialic acids are generally referred to by reference to the microorganisms that produce them. Suitable examples include Serogroup B polysialic acid from N. meningitidis C, and polysialic acid from E. coli K92, which are abbreviated as PSB, PSC, and PSK92, respectively. See, for example, Gregoriadis et al., FEBS Letter, 315(3), January 1993, pp 271-76. Synthetic analogs of capsular polysialic acid are also suitable. One such analog is described as a twin- tailed, lipid-linked polysialic acid in Matthews et al., Biopolymers, 33, pp 453-7 (1993).

Sialic acid-containing gangliosides are commercially available from sources such as Avanti Polar Lipids, Alabaster, AL. One such product has the structure

lipids

and is referred to by Product Number 860065; G_{M I} (Ovine); G_{M I} Ganglioside (Brain, Ovine-Ammonium Salt); or GalBetal-3GalNAcBetal-4(NeuAcAlpha2- 3)GalBetal-4GlcBetal -l'-Cer (Brain, Ovine-Ammonium Salt). Mixtures of sialic acid-containing gangliosides are also commercially available.

Attachment of the sialic acid-containing molecule(s) to the liposome external surface can occur during or after encapsulation of the pharmaceutical agent(s). Suitable methods for attaching the sialic acid-containing molecule to the liposome may include, for example, the method described in the articles described above.

In certain embodiments, the liposome complexes of the present invention may include at least one sialic acid-containing molecule at a suitable level to produce the desired result. More than one type of sialic acid-containing molecule can be used if desired.

In certain preferred embodiments, it is desirable to also include targeting agents in the liposome complexes. For example, to provide transport of the liposomes that contain pharmaceutical agent(s) across the blood-brain barrier containing molecule(s).

Preferably, the targeting agent is selected from the group consisting of peptides, peptide analogs, antibodies (whether monoclonal or polyclonal) or fragments thereof, small organic or inorganic or organometallic molecules (i.e., compounds or portions thereof), and combinations thereof. More preferably, the targeting agent is a compound or a portion thereof that specifically recognizes receptors expressed in the brain microvasculature (e.g., receptors for bradykinin, insulin, insulin-like growth factors, leptin, low-density lipoproteins, and transferrin). Targeting agents may be endogenous peptide ligands of the receptors, analogs of the endogenous ligands, or peptidomimetic monoclonal antibodies (MAbs such as 8D3, Rl 7, and OX26 antibodies) that bind the same receptor of the endogenous ligand. See, for example, Shusta, NeuroRx, 2, 151-161 (2005); Pardridge et al., Pharmaceutical Research, 12, 807-816 (1995); and Lee et al., Journal of Pharmacology and Experimental Therapeutics, 292, 1048- 1052 (2000).

One such example is depicted by Figures 4 and 5, wherein the targeting agent for liposomal complexes is a monoclonal antibody that recognizes the transferrin receptor. Neuro2a neuronal cells express transferrin receptors on their surface that enable the delivery of liposome-encapsulated plasmid DNA in these cells. Such a delivery is abolished upon downregulation of the cell surface transferrin receptors.

Suitable targeting agents may include, for example, insulin, transferrin, insulin-like growth factors, and leptin. Such compounds or portions thereof facilitate the receptor-mediated transcytosis of the liposome complexes of the present invention across the BBB, and subsequent entry into the brain.

If desired, a molecule that includes sialic acid could be conjugated with two different targeting agents, one peptide targeting an endogenous blood-brain barrier receptor (such as those discussed above) and the other targeting an endogenous brain cell membrane peptide. The latter could be specific for particular cells within the brain, such as neurons, glial cells, pericytes, smooth muscle cells, or microglia. The latter could also be added to enhance the cellular uptake, e.g., cell-penetrating peptides that include those described in Dietz et al., MoI. & Cell. Neurosci., 27, 85- 131 (2004). Accordingly, therapeutic delivery can further be exacted to specific cell organ, for example).

Attachment of the targeting agent(s) to the liposome external surface can occur before, during, or after the sialic acid-containing molecule(s) are associated with to the liposomes. Suitable methods for attaching the targeting agent(s) to the sialic acid-containing molecule(s) may include, for example, generation of an aldehyde on the terminal sialic acid unit (e.g., by reaction with sodium periodate), which may react with an amine of the targeting agent to yield an imine. This imine may be subsequently reduced by a reducing agent such as sodium borohydride to yield a hydrolytically stable secondary or tertiary amine.

In certain embodiments, the liposome complexes of the present invention may include at least one targeting agent at a suitable level to produce the desired result. More than one type of targeting agent can be used if desired.

Figure 1 shows a particular example of one embodiment of the present invention in which a liposome complex encapsulates a therapeutic, expression plasmid DNA. Distal ends of the liposome-conjugating polysialic acid (PSA) strands are further conjugated to a monoclonal antibody, which specifically recognizes a BBB endothelial receptor.

The invention also provides methods of making liposome complexes for delivering a pharmaceutical agent. As discussed herein, such methods typically involve preparing a liposome having an exterior surface and an internal compartment and associating a pharmaceutical agent with the liposome (preferably, incorporating a pharmaceutical agent within the internal compartment of the liposome). A sialic acid-containing molecule can be associated with (e.g., attached at the external surface of) the liposome during or after association of the pharmaceutical agent. If used, a targeting agent can be attached to the sialic acid- containing molecule before, during, or after association of the sialic acid-containing molecule with the liposome.

The invention also provides methods of in vivo administration of a liposome complex of the present invention for delivering a pharmaceutical agent to a subject. In one embodiment, such administration could be used for treating and/or preventing one or more afflictions such as a psychiatric or neurological disorder or any disease affecting and/or originating in the brain such as Parkinson's Disease and orthopedic systems.

Various combinations of liposome complexes could be used, each containing a different pharmaceutical agent, for desired effect. Alternatively, various combinations of pharmaceutical agents (not associated with a liposome) and liposome complexes of the present invention could be administered to a subject. For example, a pharmaceutical agent could be added to the delivery solution that contains a liposome complex of the present invention. Preferably, the liposome complex is administered intra-vascularly and crosses the blood brain barrier, which is particularly desirable for preventing and/or treating neurological disorders.

The liposome complexes of this invention provide useful mechanisms for pharmaceutical applications for administering a therapeutic or diagnostic agent to a subject. Accordingly, the liposome complexes of this invention are useful as pharmaceutical compositions, optionally in combination with pharmaceutically acceptable carriers. Such pharmaceutical compositions can include two or more types of liposome complexes, each containing different pharmaceutical agents and/or targeting moieties. Such pharmaceutical compositions can also include one or more pharmaceutical agents that are not a part of the liposome complex. Liposome complexes of the present invention can be included in pharmaceutical compositions that crosslink, gel, or change in viscosity on or after administration to a subject. This can occur, for example, through covalent bond formation, hydrogen bond formation, pH change, temperature change, complex formation, and the like. Liposome complexes of the present invention can be included in pharmaceutical compositions that provides for delayed or extended release of the liposome complex, and, hence, the pharmaceutical agent(s) associated therewith after administration to a subject. This can occur, for example, using pH sensitivity as a trigger for release. Administration of the liposome complexes described herein can be via any of the accepted modes of administration for the biologically active substances that are desired to be administered. These methods include oral, topical, parenteral, ocular, transdermal, nasal and other systemic or aerosol forms, although IV administration is preferred. may be in the form of solid, semi-solid or liquid dosage forms, such as, for example, tablets, suppositories, pills, capsules, powders, liquids, suspensions, or the like, preferably in unit dosage forms suitable for single administration of precise dosages. The pharmaceutical compositions will include the liposome complexes as described herein and optionally a pharmaceutical acceptable excipient, other medicinal agents, pharmaceutical agents, carriers, adjuvants, etc.

Topical formulations composed of the liposome complexes described herein, penetration enhancers, and other biologically active drugs or medicaments can be applied in many ways. The solution can be applied dropwise, from a suitable delivery device, to the appropriate area of skin or diseased skin or mucous and be integrated over a total time period of the sustained-release device in order to compute the appropriate dose required. Although effective dosage ranges for specific biologically active substances of interest are dependent upon a variety of factors, and are generally known to one of ordinary skill in the art, some dosage guidelines can be generally defined.

In general, topical formulations are prepared in gels, creams, or solutions having an active ingredient in the range of from 0.001% to 10% (w/v), preferably 0.01 to 5%, and most preferably about 1% to about 5%. Of course, these ranges are subject to variation depending upon the potency of the therapeutic agent, and could in appropriate circumstance fall within a range as broad as from 0.001 % to 20%. In all of these exemplary formulations, as well as other topical formulations, the total dose given will depend upon the size of the affected area of the skin and the number of doses per day. The formulations may be applied as often as necessary, but preferably not more than about three times per day.

For oral administration, a pharmaceutically acceptable, non-toxic composition is formed by the incorporation of any of the normally employed excipients, such as, for example, mannitol, lactose, starch, magnesium stearate, sodium saccharine, talcum, cellulose, sodium crosscarmellose, glucose, gelatin, sucrose, magnesium carbonate, and the like. Such compositions include solutions, suspensions, tablets, dispersible tablets, pills, capsules, powders, sustained-release formulations, and the like.

Preferably the compositions will take the form of a pill or tablet. Thus the composition will contain along with the active ingredient: a diluent such as stearate, and the like; and a binder such as starch, gum acacia, gelatin, polyvinylpyrrolidone, cellulose and derivatives thereof, and the like.

Liquid pharmaceutically administrable compositions can, for example, be prepared by dissolving, dispersing, etc., the liposomes as described above and optional pharmaceutical adjuvants in a carrier, such as, for example, water, saline, aqueous dextrose, glycerol, glycols, ethanol, and the like, to thereby form a suspension. If desired, the pharmaceutical composition to be administered may also contain minor amounts of nontoxic auxiliary substances such as wetting agents, emulsifying agents, or solubilizing agents, pH buffering agents, and the like, for example, acetate, sodium citrate, cyclodextrin derivatives, sorbitan monolaurate, triethanolamine sodium acetate, triethanolamine oleate, etc.

Actual methods of preparing such dosage forms are known, or will be apparent, to those skilled in this art. The composition or formulation to be administered will, in any event, contain a quantity of the active pharmaceutical agent in an amount sufficient to effectively treat the disorder or disease of the subject being treated.

For a solid dosage form, the suspension, in, for example, propylene carbonate, vegetable oils or triglycerides, is preferably encapsulated in a gelatin capsule. Such suspensions and the preparation and encapsulation thereof, can be prepared by methods that are well known to those of skill in the art. For a liquid dosage form, the suspension may be diluted with a sufficient quantity of a pharmaceutically acceptable liquid carrier, e.g., water, to be easily measured for administration. Alternatively, liquid or semi-solid oral formulations may be prepared by dissolving or dispersing the liposome complexes in vegetable oils, glycols, triglycerides, propylene glycol esters (e.g., propylene carbonate), and the like, and encapsulating these solutions or suspensions in hard or soft gelatin capsule shells.

Nasal solutions of the liposome complexes alone or in combination with pharmaceutically acceptable excipients can also be administered.

Formulations of the liposome complexes may also be administered to the respiratory tract as an aerosol for a nebulizer. In such a case, the particles of the formulation have diameters of less than 50 microns, preferably less than 10 microns.

Intravenous administration of the liposome complexes may also be used. following example, but the particular materials and amounts thereof recited, as well as other conditions and details, should not be construed to unduly limit this invention. EXAMPLE

Preparation of Antibody-conjugated Liposomes DNA-containing liposomes composed of POPC (l-palmitoyl-2-oleoyl-sn- glycerol-3-phosphocholine), DDAB (didodecyldimethylammonium bromide), and ganglioside were prepared at a ratio of 82: 15:3. Lipid films were first created and then rehydrated. Each lipid was separately dissolved in chloroform/methanol in a 10 milliliters (mL) round-bottomed flask with a 20/24 outer joint as follows: To 16.4 micromoles (μmol) (or 12.42 milligrams (mg)) of POPC in chloroform (purchased from Avanti Polar Lipids, Alabaster, AL), additional chloroform (583.8 μL) and methanol (583.8 microliters (μL)) were added to adjust the total chloroform :mcthanol ratio to 2:1. To 3 μmol (or 2 mg) of DDAB in chloroform (purchased from Avanti Polar Lipids), additional chloroform (12.6 μL) and methanol (12.6 μL) were added to adjust the ratio to 2:1. Approximately 0.6 μmol (or about 1.1 mg) ganglioside (purchased from EMD Biosciences, Gibbstown, NJ) was added to the POPC-containing flask. To each flask, approximately 20 mg of octyl-β-D-glucopyranoside was then added. Each lipid mixture was vortexed carefully with moderate speed. The majority of the solvent in each flask was removed from each mixture by blowing nitrogen gas over the flask surface. The remainder of the solvent was removed to make white lyophilized lipid film by using a rotary evaporator. Each lipid film was then separately re-suspended and dispersed in 500 μL of buffer containing 20 millimolar (mM) HEPES and 140 mM NaCl buffer (pH = 7.5). Each mixture was vortexed briefly to cause each lipid to go completely into suspension. Following this, each re-suspended lipid/buffer mixture was sonicated for 10 minutes, and vortexed with moderate speed.

Green fluorescent protein (GFP)-encoding supercoiled plasmid DNA (100 micrograms (μg)) (pEGFP-Cl , Clontcch, Mountain View, CA) was added dropwise to the flask containing the cationic lipid solution (i.e., containing DDAB) while the mixture was carefully vortexed. Subsequently, this DNA/DDAB mixture was incubated at room temperature for one hour. The neutral lipid solution (i.e., containing POPC) was added dropwise and the mixture was vortexed carefully. 746300) with dialysis membranes of 5000 Dalton MWCO (all purchased from Harvard Apparatus, Hollister, MA) per manufacturer's instructions, for at least 48 hours, changing the dialysis buffer (containing 20 mM HEPES and 140 mM NaCl, pH 7.5) at least twice a day.

The liposome/DNA complexes were then sequentially extruded using a mini- extruder (Product No. 610000, purchased from Avanti Polar Lipids) and 400 nm, 200 nm, and 100 nm polycarbonate membranes (all purchased from Avanti Polar Lipids) per the manufacturer's instructions. The resultant liposomes produced were in the size range of 100-200 nm, as measured by the Partica LA-950 laser diffraction particle size analyzer (purchased from Horiba Jobin Yvon, Edison, NJ). Figure 2 depicts the size distribution of liposome complexes with a mean size of 150 nm (standard deviation of 30 nm).

Unencapsulated DNA was removed by treating the liposome/DNA complexes with nuclease digestion, based on the protocol described in the example of U.S. Patent No. 6,372,250.

The removal of exteriorized plasmid DNA was determined by subjecting aliquots from before and after nuclease treatment to agarose gel electrophoresis and ethidium bromide staining (Figure 3). Lane 1 : Liposome complexes in the absence of a detergent. Lane 2: Liposome complexes lyzed with a detergent (0.1% Triton X- 100 + 0.1% polyaspartic acid) to release the encapsulated GFP-expressing plasmid DNA (size 4.7 kb, depicted by an *). Lane 3: Standard DNA ladder to demonstrate the gel mobility of DNA with different kb. Lane 4: GFP-expressing plasmid DNA. Lane 5: (Positive control for lane 1) Complexes made using a commercially available reagent L1POFECTAMINE 2000 (Invitrogcn, Carlsbad, CA) to encapsulate the GFP-expressing plasmid DNA per the manufacturer's instructions. Lane 6: (Positive control for lane 2) L1POFECTAMINE 2000 complexes lyzed, using the same detergent as described earlier, to release the encapsulated GFP- expressing plasmid DNA. Sialic acid residues on the surface of liposomes were conjugated to a monoclonal antibody (ACL8971, purchased from Accurate Chemical & Scientific, Westbury, NY) targeting the transferrin receptor that is highly expressed in the blood brain barrier. This was done using a procedure using periodate oxidation adapted from Liposomes: A Practical Approach (2^nd edition, 2003), edited by Protocol 7, pages 202-203, and Heath et al., Biochem. Biophys. Acta, 640, 66 (1981).

The liposome suspension (approximately 1.0 mL) was incubated with sodium periodate solution (0.2 mL, 0.2 M in water) in a brown vial at the ambient temperature for 30 minutes. The material was then transferred to a 10,000 molecular weight cut off Slide-A-Lyzer (purchased from Pierce, Rockford, IL) and dialyzed overnight (approximately 24 hours) against borate buffer (1 L, 20 mM sodium borate Na₂B₄O₇.10H₂O with 120 mM NaCl, pH 8.4).

After dialysis, the material (approximately 1.4 mL) was transferred to a vial and mixed with 1.0 mL transferrin receptor antibody (ACL8971 ). Into this mixture, sodium cyanoborohydride solution (0.4 mL, 2 M in water) was added. The materials were shook well and stored at 4⁰C overnight.

Purification of the liposomes conjugated to the transferrin receptor-targeting antibody was performed using a disposable ultrafiltration unit with a 200,000 MWCO filter (Ultrafiltration/Filter Product No. USY-20 purchased from Advantec MFS, Dublin, CA) per the manufacturer's instructions. This was followed by re- suspension of the liposomes in 1.4 mL borate buffer (20 mM with 120 mM NaCl, pH 8.4).

Transmission electron microscopy was performed to visualize the antibody conjugated to the liposomes. The liposome-conjugated antibody was further bound by a conjugate of an anti-mouse secondary antibody and 10 nm gold particles (0.4 mL, Conjugate Product No. G7652 purchased from Sigma). This complex was purified from the unbound gold-secondary antibody conjugate by ultrafiltration as described above, and the purified complex was visualized employing the cryo-TEM procedure using JEOL 1210 TEM (Figure 4) as described by Bang et al.,

Macromolecules, 39, 1 199-1208 (2006). The position of gold particles indicates the association of transferrin receptor-targeting monoclonal antibody with the liposome complexes.

The DNA-encapsulating liposomes (50 μL) were added to approximately 70% confluent mouse Neuro2a neuroblastoma cells (American Type Culture Collection, Manassas, VA) plated in a 6- well plate with 1 mL of culture media. After approximately 48 hours of culturing at 37°C, cells were imaged under a fluorescent microscope to visualize the green fluorescence emitted by cells expressing GFP encoded by the DNA from liposomes (Figure 5). Image A depicts Image B is a corresponding bright-field image. Scale bar: 10 μm.

Alternatively, the same transfection procedure was followed except that the cells were initially cultured for 24 hours with 1 μg/mL of transferrin receptor antibody that was not conjugated to the liposomes. This pre-treatment leads to a substantial downregulation of transferrin receptors on the surface of Neuro2a cells. Subsequently, incubation of such Neuro2a cells with the DNA-containing liposomes conjugated to the transferrin receptor antibody did not result in any GFP-expressing cells, suggesting the requirement of transferrin receptors on the cell surface for an uptake of DNA-encapsulating liposomes conjugated to the transferrin receptor antibody.

The complete disclosure of all patents, patent applications, and publications, and electronically available material (e.g., GenBank amino acid and nucleotide sequence submissions; and protein data bank (pdb) submissions) cited herein are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims.

Claims

What is claimed is:

1. A liposome complex comprising: a liposome having an exterior surface and an internal compartment: a pharmaceutical agent associated with the liposome; a sialic acid-containing molecule associated with the liposome; and a targeting agent; wherein the sialic acid-containing molecule forms a linker between the targeting agent and the external surface of the liposome.

2. The liposome complex of claim 1 , wherein the liposome is prepared from phospholipids selected from the group consisting of phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholines, phosphatidylglycerol, phosphatidic acid, phosphatidylmethanol, cardiolipin, ceramide, cholesterol, cerebroside, lysophosphatidylcholine, D-erythrosphingosine, sphingomyelin, dodecyl phosphocholine, N- biotinyl phosphatidylethanolamine, and combinations thereof.

3. The liposome complex of claim 1 or claim 2, wherein the pharmaceutical agent is located within the internal compartment of the liposome.

4. The liposome complex of any one of claims 1 through 3, wherein the pharmaceutical agent is a therapeutic agent.

5. The liposome complex of any one of claims 1 through 3, wherein the pharmaceutical agent is a diagnostic agent.

6. The liposome complex of any one of claims 1 through 5, wherein the sialic acid-containing molecule is attached at the external surface of the liposome.

7. The liposome complex of any one of claims 1 through 6, wherein at least one sialic acid-containing molecule comprises a lipid head-group and a sialic acid group.

8. The liposome complex of claim 7, therein the lipid head-group is a phospholipid.

9. The liposome complex of any one of claims 1 through 8, wherein the sialic acid-containing molecule is selected from the group consisting of capsular polysialic acid, sialic acid-containing gangliosides, colominic acid, and combinations thereof.

10. The liposome complex of claim 9, wherein the sialic acid-containing molecule is a capsular polysialic acid.

11. The liposome complex of any one of claims 1 through 10, wherein the targeting agent is selected from the group consisting of peptides, peptide analogs, antibodies, antibody fragments, small organic or inorganic or organometallic molecules, and combinations thereof.

12. The liposome complex of claim 1 1 , wherein the targeting agent is a compound or portion thereof that specifically recognizes receptors expressed in the brain microvasculature.

13. The liposome complex of any one of claims 1 through 12 comprising two or more different pharmaceutical agents.

14. A pharmaceutical composition comprising the liposome complex of any one of claims 1 through 13 and an optional pharmaceutically acceptable carrier.

15. The pharmaceutical composition of claim 14 further comprising a pharmaceutical agent that is not a part the liposome complex.

16. The pharmaceutical composition of claim 14 or claim 15 which crosslinks, gels, or changes in viscosity on or after administration to a subject.

17. The pharmaceutical composition of any one of claims 14 through 16 which provides for delayed or extended release of the liposome complex after administration to a subject.

18. The pharmaceutical composition of any one of claims 14 through 17 comprising two or more different liposome complexes, each containing different pharmaceutical agents and/or targeting agents.

19. A method of treating and/or preventing an affliction, the method comprising administering a liposome complex or pharmaceutical composition of any one of claims 1 through 18 to a subject.

20. The method of claim 19, wherein the affliction is a psychiatric disorder, a neurological disorder, a disease affecting and/or originating in the brain, a disorders of the cardiac system, a disorder of the hepatic system, a disorder of the vascular system, a disorder of the orthopedic system, or combinations thereof.

21. A method of delivering a pharmaceutical agent to a subject, the method comprising administering a liposome complex or pharmaceutical composition of any one of claims 1 through 18 to the subject.

22. The method of claim 21 , wherein the liposome complex is administered to the subject for preferential uptake by an organ of interest.

23. A method of making a liposome complex, the method comprising: preparing a liposome having an exterior surface and an internal compartment, a pharmaceutical agent associated therewith, and a sialic acid-containing molecule associated therewith; and attaching a targeting agent to the sialic acid-containing molecule; wherein the sialic acid-containing molecule forms a linker between the targeting agent and the external surface of the liposome.

24. The method of claim 23, wherein preparing a liposome having an exterior surface and an internal compartment and a pharmaceutical agent associated therewith comprises encapsulating the pharmaceutical agent within the internal compartment of the liposome.

25. The method of claim 24, wherein preparing a liposome having an exterior surface and an internal compartment and a sialic acid-containing molecule associated therewith comprises attaching a sialic acid- containing molecule to the external surface of the liposome during or after encapsulation of the pharmaceutical agent.

26. The method of claim 25, further comprising attaching a targeting agent to the sialic acid-containing molecule before, during, or after attaching the sialic acid-containing molecule to the external surface of the liposome.

27. A liposome complex comprising: a liposome having an exterior surface and an internal compartment: a pharmaceutical agent associated with the liposome; a sialic acid-containing molecule associated with the liposome; and optionally a targeting agent; wherein the sialic acid-containing molecule comprises polysialic acid having a degree of polymerization of at least 8.

28. The liposome complex of claim 27, wherein the liposome is prepared from phospholipids selected from the group consisting of phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholines, phosphatidylglycerol, phosphatidic acid, phosphatidylmethanol, cardiolipin, ceramide, cholesterol, cerebroside, lysophosphatidylcholine, D-erythrosphingosine, sphingomyelin, dodecyl phosphocholine, N-biotinyl phosphatidylethanolamine, and combinations thereof.

29. The liposome complex of claim 27 or claim 28, wherein the pharmaceutical agent is located within the internal compartment of the liposome.

30. The liposome complex of any one of claims 27 through 29, wherein the pharmaceutical agent is a therapeutic agent.

31. The liposome complex of any one of claims 27 through 29, wherein the pharmaceutical agent is a diagnostic agent.

32. The liposome complex of any one of claims 27 through 31, wherein the sialic acid-containing molecule is attached at the external surface of the liposome.

33. The liposome complex of any one of claims 27 through 32, wherein at least one sialic acid-containing molecule comprises a lipid head-group and a sialic acid group.

34. The liposome complex of claim 33, therein the lipid head-group is a phospholipid.

35. The liposome complex of any one of claims 27 through 34, wherein the sialic acid-containing molecule is selected from the group consisting of capsular polysialic acid, sialic acid-containing gangliosides, colominic acid, and combinations thereof.

36. The liposome complex of claim 35, wherein the sialic acid-containing molecule is a capsular polysialic acid.

37. The liposome complex of any one of claims 27 through 36 comprising two or more different pharmaceutical agents.

38. The liposome complex of any one of claims 27 through 37 further comprising a targeting agent, wherein the sialic acid-containing molecule forms a linker between the targeting agent and the external surface of the liposome.

39. The liposome complex of claim 38, wherein the targeting agent is selected from the group consisting of peptides, peptide analogs, antibodies, antibody fragments, small organic or inorganic or organometallic molecules, and combinations thereof.

40. A pharmaceutical composition comprising the liposome complex of any one of claims 27 through 39 and an optional pharmaceutically acceptable carrier.

41 . The pharmaceutical composition of claim 40 further comprising a pharmaceutical agent that is not a part the liposome complex.

42. The pharmaceutical composition of claim 40 or claim 41 which crosslinks, gels, or changes in viscosity on or after administration to a subject.

43. The pharmaceutical composition of any one of claims 40 through 42 which provides for delayed or extended release of the liposome complex after administration to a subject.

44. The pharmaceutical composition of any one of claims 40 through 43 comprising two or more different liposome complexes, each containing different pharmaceutical agents.

45. A method of treating and/or preventing an affliction, the method comprising administering a liposome complex or pharmaceutical composition of any one of claims 27 through 44 to a subject.

46. The method of claim 45, wherein the affliction is a psychiatric disorder, a neurological disorder, a disease affecting and/or originating in the brain, a disorders of the cardiac system, a disorder of the hepatic system, a disorder of the vascular system, a disorder of the orthopedic system, or combinations thereof.

47. A method of delivering a pharmaceutical agent to a subject, the method comprising administering a liposome complex or pharmaceutical composition of any one of claims 27 through 44 to the subject.

48. The method of claim 47, wherein the liposome complex is administered to the subject for preferential uptake by an organ of interest.

49. A method of making a liposome complex, the method comprising: preparing a liposome having an exterior surface and an internal compartment, a pharmaceutical agent associated therewith, and a sialic acid-containing molecule associated therewith; and optionally attaching a targeting agent to the sialic acid-containing molecule; wherein the sialic acid-containing molecule comprises polysialic acid having a degree of polymerization of at least 8.

50. The method of claim 49, wherein preparing a liposome having an exterior surface and an internal compartment and a pharmaceutical agent associated therewith comprises encapsulating the pharmaceutical agent within the internal compartment of the liposome.

51. The method of claim 50, wherein preparing a liposome having an exterior surface and an internal compartment and a sialic acid-containing molecule associated therewith comprises attaching a sialic acid- containing molecule to the external surface of the liposome during or after encapsulation of the pharmaceutical agent.

52. The method of claim 51 , further comprising attaching a targeting agent to the sialic acid-containing molecule before, during, or after attaching the sialic acid-containing molecule to the external surface of the liposome.