AI
Saturday, April 02, 2011 11:09:46 AM
[0023]Exemplary cell-targeting moieties include but are not limited to receptor-specific ligands, antibodies, and other targeting moieties, such as peptides possessing an Arginine-Glycine-Aspartic acid (RGD) amino acid sequence or a Tyrosine-Isoleucine-Serine-Arginine-Glycine (YISRG) motif; growth factors including epidermal growth factor, vascular endothelial growth factor and fibroblast growth factor; viral surface ligands such as sialic acid and N-acetylneuraminic acid derivatives; cell receptor ligands such as folate, methotrexate, pteroic acid, estradiol, estratriol, testosternone, and other hormones; mannose-6-phosphate, sugars, vitamins, tryptophan, and the like. Antibodies are preferably monoclonal antibodies directed at cell-specific surface antigens; suitable targeting moieties include not only complete antibodies but also antibody fragments containing the active antigen-binding sequences, such as Fab'2 fragments, Fab' fragments, or short chain peptide analogues of the active antigen binding sequences of such antibodies.
[0024]Examples of virus-targeting moieties include small molecule ligands that bind to a virus, such as aminoalkyladamantanes, Fuzeon.TM., PRO-542, BMS-488043, sialic acid, 2:deoxy-2,3-didehydro-N-acetylneuraminic acid, 4-guanidino-Neu5Ac2en (zanamivir), oseltamivir, RWJ-270201, and the like; oligopeptides, oligosaccharides, and glycopeptides that bind to viral surfaces, and antibodies and antibody fragments directed at virus-specific surface antigens. In preferred embodiments, the present invention provides .pi.-polymers bearing ligands for viral neuraminidase or hemagglutinin. It is well-established that such polymers have antiviral properties in their own right; see for example T. Masuda et al., Chemical & Pharmaceutical Bulletin 51:1386-98 (2003); M. Itoh et al., Virology 212:340-7 (1995), and Reece et al., U.S. Pat. No. 6,680,054 (2004). The hydrophobic cores of the antiviral polymers and polymer aggregates of the present invention may optionally be loaded with one or more conventional antiviral drugs, which are advantageously released in the vicinity of the viral particle.
[0025]Other attachment groups of medical relevance may be small chemicals, peptides, antibodies or antibody fragments, enzymes, or active pharmaceutical ingredients, that may affect biological processes such as hormones or hormone agonists or antagonists, substances that interfere with virus binding, substances that interfere with cell cycle or cellular processes after intracellular entry, and the like. Cells of unicellular and multicellular organisms, including bacteria, fungi, higher animals, and plants, may be targeted. Biotin may be attached to the .pi.-polymer and used as an attachment point for avidin- and streptavidin-coupled proteins, peptides, and other targeting or pharmacologically active agents, such as antibodies, growth hormones, imaging reagents, and the like.
[0053]Alternatively, two or more specific ligands can be attached to improve specificity of binding to say, a virus, or cell surface. Two or more specific ligands can also be used so as to cause an interaction between different cellular targets, for example, one ligand may target a virus particle, and another ligand may facilitate binding to a phagocyte, thereby bringing virus particle into proximity or contact with the phagocyte and promoting phagocytosis.
[0054]Such derivatization allows the attachment of three or more distinct targeting and/or therapeutic moieties to the polymer, through different functional group attachments (such as amine, carboxylate, and thiol). Thus, one may attach a tissue-specific targeting agent, an imaging agent, and a therapeutic agent to a single polymer chain, and subsequent self-assembly of the polymer will yield a targeted therapeutic whose distribution and efficiency of targeting can be monitored.
[0055]Attachment of ligands to the repeating units of the polymers of the invention affords multivalent display of the ligand on the polymer chain and on the nanoparticles surface. Multivalent display often leads to great increases in affinity for the target. For example, multivalent antibodies can be far more effective in clearance of their targets than the normal divalent antibodies. Carbohydrate-binding proteins and carbohydrates are known to be multivalent in nature, and ineffective if monovalent. Similarly, multivalent peptide and carbohydrate targeting moieties will be far more effective than the monomer alone. The increase in MW due to attachment to the polymer results in reduced renal clearance rates of peptides and other ligands. In addition, the PEG backbone affords to the peptide benefits similar to those of PEGylation, including evasion of immune surveillance.
[0056]Further, a multivalent targeting moiety will decorate a multivalent target (say, a virus particle) and neutralize it far more effectively than the Monomeric targeting moiety. The ability to display multiple (different) peptides in multivalent format will lead to enhanced specificity. For example, a truly HIV-specific (HIV virus-binding) polymer can be built by attaching a peptide corresponding to the CD4 binding region, and another peptide corresponding to the CCR-5 or CXCR-4 binding region of the virus, and possibly a third peptide corresponding to the other receptor (CXCR-4 or CCR-5 respectively). Such a polymer could completely mask the virus's binding regions and render the virus unable to attach to cells and thereby non-infective. In addition, the surfactant properties of the polymer would lead to destabilization of the virus structure itself upon binding. Instead of peptides, small molecules that interfere with the same binding patterns (CD4, CCR-5, CXCR-4) or a mixture of peptides and small molecules, preferably with complementary activities, can be employed. The resulting polymers will render any free virus ineffective, and thus may be ideal for stopping spread of infection, by using them as components of condom lubricants and the like. In addition, such polymers may be injected into patients to reduce the HIV burden.
http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220100260743%22.PGNR.&OS=DN/20100260743&RS=DN/20100260743
Here's a question FWIW - Is a sialic acid LIGAND the SAME as sialic acid PER SE? Is one an ACID and the other a LIGAND (PROTEIN)? Stupid question? Probably - but hey, if you don't ask - you'll NEVER know!
BTW it is somewhat amusing the assumptions we all make, some of which are surely wrong but that is certainly understandable in this particular art which is foreign to most of us.
