This application is a divisional of U.S. patent application Ser. No. 12/949,536, filed Nov. 18, 2010, which is a divisional of U.S. patent application Ser. No. 12/396,605 (now issued U.S. Pat. No. 7,858,070), filed Mar. 3, 2009, which is a divisional of U.S. patent application Ser. No. 11/633,729 (now issued U.S. Pat. No. 7,527,787), filed Dec. 5, 2006, which is a continuation-in-part of PCT/US2006/010762, filed Mar. 24, 2006; PCT/US2006/012084, filed Mar. 29, 2006; PCT/US2006/025499, filed Jun. 29, 2006; U.S. patent application Ser. Nos. 11/389,358 (now issued U.S. Pat. No. 7,550,143), filed Mar. 24, 2006; 11/391,584 (now issued U.S. Pat. No. 7,521,056), filed Mar. 28, 2006 and 11/478,021 (now issued U.S. Pat. No. 7,534,866), filed Jun. 29, 2006; which claimed priority to provisional U.S. Patent Applications Nos. 60/782,332, filed Mar. 14, 2005; 60/728,292, filed Oct. 19, 2005, and 60/751,196, filed Dec. 16, 2005. This application claims the benefit under 35 U.S.C. §119(e) to provisional U.S. Patent Applications No. 60/751,196, filed Dec. 16, 2005, and No. 60/864,530, filed Nov. 6, 2006. The text of each of the applications cited above is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
Existing technologies for the production of antibody-based agents having multiple functions or binding specificities suffer a number of limitations. For agents generated by recombinant engineering, such limitations may include high manufacturing cost, low expression yields, instability in serum, instability in solution resulting in formation of aggregates or dissociated subunits, undefined batch composition due to the presence of multiple product forms, contaminating side-products, reduced functional activities or binding affinity/avidity attributed to steric factors or altered conformations, etc. For agents generated by various methods of chemical cross-linking, high manufacturing cost and heterogeneity of the purified product are two major limitations.
In recent years there has been an increased interest in antibodies or other binding moieties that can bind to more than one antigenic determinant (also referred to as epitopes). Generally, naturally occurring antibodies and monoclonal antibodies have two antigen binding sites that recognize the same epitope. In contrast, bifunctional or bispecific antibodies (hereafter, only the term bispecific antibodies will be used throughout) are synthetically or genetically engineered structures that can bind to two distinct epitopes. Thus, the ability to bind to two different antigenic determinants resides in the same molecular construct.
Bispecific antibodies are useful in a number of biomedical applications. For instance, a bispecific antibody with binding sites for a tumor cell surface antigen and for a T-cell surface receptor can direct the lysis of specific tumor cells by T cells. Bispecific antibodies recognizing gliomas and the CD3 epitope on T cells have been successfully used in treating brain tumors in human patients (Nitta, et al. Lancet. 1990; 355:368-371). More recently, a new class of bispecific antibodies termed “bispecific T-cell engagers” (BiTEs) was reported to overcome the limitations of most tumor-targeting bispecific antibodies that involve the recruitment of effector cells for biological activities (Kufer, et al. Trends in Biotechnol. 2004; 22: 238-244). BiTEs are recombinant bispecific single-chain antibodies composed of two distinct single-chain Fc fragments (scFvs) directed against a surface antigen on target cells and CD3 on T cells joined in tandem via a flexible polypeptide linker (Mack, et al., Proc Natl Acad Sci U.S.A. 1995; 92: 7021-7025). BiTEs are produced in mammalian cells and in contrast to other CD3-directed bispecific antibodies are capable of efficiently redirecting human peripheral. T lymphocytes to kill target cells without any requirement for pre- or costimulation of the effector T cells (Mack, et al. J. Immonol. 1997; 158: 3965-3970; Loffler, et al. Blood. 2000; 95: 2098-2103). BiTE concentrations as low as 10-100 pg/mL (˜0.1-2 pM) were shown to be sufficient for achieving half-maximal target cell lysis in vitro (Dreier, et al. Int J. Cancer. 2002; 100: 690-697) and tumor growth could be prevented with sub-microgram amounts in mouse models (Dreier, et al. J. Immunol. 2003; 170: 4397-4404; Schlereth et al. Cancer Res. 2005; 65: 2882-2889).
Numerous methods to produce bispecific antibodies are known. Methods for construction and use of bispecific and multi-specific antibodies are disclosed, for example, in U.S. Patent Application Publication No. 20050002945, filed Feb. 11, 2004, the entire text of which is incorporated herein by reference. Bispecific antibodies can be produced by the quadroma method, which involves the fusion of two different hybridomas, each producing a monoclonal antibody recognizing a different antigenic site (Milstein and Cuello, Nature, 1983; 305:537-540). The fused hybridomas are capable of synthesizing two different heavy chains and two different light chains, which can associate randomly to give a heterogeneous population of 10 different antibody structures of which only one of them, amounting to ⅛ of the total antibody molecules, will be bispecific, and therefore must be further purified from the other forms, which even if feasible will not be cost effective. Furthermore, fused hybridomas are often less stable cytogenically than the parent hybridomas, making the generation of a production cell line more problematic.
Another method for producing bispecific antibodies uses heterobifunctional cross-linkers to chemically tether two different monoclonal antibodies, so that the resulting hybrid conjugate will bind to two different targets (Staerz, et al. Nature. 1985; 314:628-631; Perez, et al. Nature. 1985; 316:354-356). Bispecific antibodies generated by this approach are essentially heteroconjugates of two IgG molecules, which diffuse slowly into tissues and are rapidly removed from the circulation. Bispecific antibodies can also be produced by reduction of each of two parental monoclonal antibodies to the respective half molecules, which are then mixed and allowed to reoxidize to obtain the hybrid structure (Staerz and Bevan. Proc Natl Acad Sci U S A. 1986; 83:1453-1457). An alternative approach involves chemically cross-linking two or three separately purified Fab′ fragments using appropriate linkers. For example, European Patent Application 0453082 disclosed the application of a tri-maleimide compound to the production of bi- or tri-specific antibody-like structures. A method for preparing tri- and tetra-valent monospecific antigen-binding proteins by covalently linking three or four Fab fragments to each other via a connecting structure is provided in U.S. Pat. No. 6,511,663. All these chemical methods are undesirable for commercial development due to high manufacturing cost, laborious production process, extensive purification steps, low yields (<20%), and heterogeneous products.
Other methods include improving the efficiency of generating hybrid hybridomas by gene transfer of distinct selectable markers via retrovirus-derived shuttle vectors into respective parental hybridomas, which are fused subsequently (DeMonte, et al. Proc Natl. Acad Sci USA. 1990, 87:2941-2945); or transfection of a hybridoma cell line with expression plasmids containing the heavy and light chain genes of a different antibody. These methods also face the inevitable purification problems discussed above.
A method to produce a recombinant bispecific antibody composed of Fab fragments from the same or different antibodies that are brought into association by complementary interactive domains inserted into a region of the antibody heavy chain constant region, was disclosed in U.S. Pat. No. 5,582,996. The complementary interactive domains are selected from reciprocal leucine zippers or a pair of peptide segments, one containing a series of positively charged amino acid residues and the other containing a series of negatively charged amino acid residues. One limitation of such a method is that the individual Fab subunits containing the fused complementary interactive domains appear to have much reduced affinity for their target antigens unless both subunits are combined.
Discrete VH and VL domains of antibodies produced by recombinant DNA technology may pair with each other to form a dimer (recombinant Fv fragment) with binding capability (U.S. Pat. No. 4,642,334). However, such non-covalently associated molecules are not sufficiently stable under physiological conditions to have any practical use. Cognate VH and VL domains can be joined with a peptide linker of appropriate composition and length (usually consisting of more than 12 amino acid residues) to form a single-chain Fv (scFv) with binding activity. Methods of manufacturing scFvs are disclosed in U.S. Pat. No. 4,946,778 and U.S. Pat. No. 5,132,405. Reduction of the peptide linker length to less than 12 amino acid residues prevents pairing of VH and VL domains on the same chain and forces pairing of VH and VL domains with complementary domains on other chains, resulting in the formation of functional multimers. Polypeptide chains of VH and VL domains that are joined with linkers between 3 and 12 amino acid residues form predominantly dimers (termed diabodies). With linkers between 0 and 2 amino acid residues, trimers (termed triabody) and tetramers (termed tetrabody) are favored, but the exact patterns of oligomerization appear to depend on the composition as well as the orientation of V-domains (VH-linker-VL or VL-linker-VH), in addition to the linker length.
Monospecific diabodies, triabodies, and tetrabodies with multiple valencies have been obtained using peptide linkers consisting of 5 amino acid residues or less. Bispecific diabodies, which are heterodimers of two different scFvs, each scFv consisting of the VH domain from one antibody connected by a short peptide linker to the VL domain of another antibody, have also been made using a dicistronic expression vector that contains in one cistron a recombinant gene construct comprising VH1-linker-VL2 and in the other cistron a second recombinant gene construct comprising VH2-linker-VL1 (Holliger, et al. Proc Natl Acad Sci USA. 1993; 90: 6444-6448; Atwell, et al. Mol. Immunol. 1996; 33:1301-1302; Holliger, et al. Nature Biotechnol. 1997; 15: 632-631; Helfrich, et al. Int. J. Cancer. 1998; 76: 232-239; Kipriyanov, et al. Int J. Cancer. 1998; 77: 763-772; Holliger, et al. Cancer Res. 1999; 59: 2909-2916).
More recently, a tetravalent tandem diabody (termed tandab) with dual specificity has also been reported (Cochlovius, et al. Cancer Res. 2000; 60: 4336-4341). The bispecific tandab is a dimer of two identical polypeptides, each containing four variable domains of two different antibodies (VH1, VL1, VH2, VL2) linked in an orientation to facilitate the formation of two potential binding sites for each of the two different specificities upon self-association.
To date, the construction of a vector that expresses bispecific or trispecific triabodies has not been achieved. However, polypeptides comprising a collectin neck region are reported to trimerize (Hoppe, et al. FEBS Letters. 1994; 344: 191-195). The production of homotrimers or heterotrimers from fusion proteins containing a neck region of a collectin is disclosed in U.S. Pat. No. 6,190,886.
Methods of manufacturing scFv-based agents of multivalency and multispecificity by varying the linker length were disclosed in U.S. Pat. No. 5,844,094, U.S. Pat. No. 5,837,242, and WO 98/44001. Methods of manufacturing scFv-based agents of multivalency and multispecificity by constructing two polypeptide chains, one comprising of the VH domains from at least two antibodies and the other the corresponding VL domains were disclosed in U.S. Pat. No. 5,989,830 and U.S. Pat. No. 6,239,259. Common problems that have been frequently associated with generating scFv-based agents of multivalency and multispecificity by prior art methods are low expression levels, heterogenous product forms, instability in solution leading to aggregates, instability in serum, and impaired affinity.
A recombinantly produced bispecific or trispecific antibody in which the c-termini of CH1 and CL of a Fab are each fused to a scFv derived from the same or different monoclonal antibodies was disclosed in U.S. Pat. No. 6,809,185. Major deficiencies of this “Tribody” technology include impaired binding affinity of the appended scFvs, heterogeneity of product forms, and instability in solution leading to aggregates.
Thus, there remains a need in the art for a method of making multivalent structures of either monospecificity or multiple specificities or functionalities, which are of defined composition, homogeneous purity, and unaltered affinity, and can be produced in high yields without the requirement of extensive purification steps. Furthermore, such structures must also be sufficiently stable in serum to allow in vivo applications. A need exists for stable, multivalent structures of monospecificity or multiple specificities or functionalities that are easy to construct and/or obtain in relatively purified form.
SUMMARY OF THE INVENTION
The present invention discloses a platform technology for generating stably tethered structures that may be monospecific and/or monofunctional, or may have multiple functions or binding specificities, and are suitable for in vitro as well as in vivo applications. In preferred embodiments, such stably tethered structures are produced as complexes of two components, referred herein as A and B, via specific interactions between two distinct peptide sequences, one termed dimerization and docking domain (DDD) and the other anchoring domain (AD). In more preferred embodiments, the DDD sequences (shown for DDD1 and DDD2 in FIG. 1) are derived from the regulatory (R) subunits of a cAMP-dependent protein kinase (PKA), and the AD sequences (shown for AD1 and AD2 in FIG. 2) are derived from a specific region found in various A-kinase anchoring proteins (AKAPs) that mediates association with the R subunits of PKA. However, the skilled artisan will realize that other dimerization and docking domains and anchoring domains are known and any such known domains may be used within the scope of the claimed subject matter. The disclosed methods and compositions enable site-directed covalent or non-covalent association of any two complexes with the DDD/AD coupling system. The X-type four-helix bundle dimerization motif that is a structural characteristic of the DDD (Newlon, et al. EMBO J. 2001; 20: 1651-1662; Newlon, et al. Nature Struct Biol. 1999; 3: 222-227) is found in other classes of proteins, such as the S100 proteins (for example, S100B and calcyclin), and the hepatocyte nuclear factor (HNF) family of transcriptional factors (for example, HNF-1α and HNF-1β). As S100 proteins have biological activities such as tumorigenesis, they may be less desirable for such use.
Over 300 proteins that are involved in either signal transduction or transcriptional activation contain a module of 65-70 amino acids termed the sterile a motif (SAM) domain, which has a variation of the X-type four-helix bundle present on its dimerization interface. For S100B, this X-type four-helix bundle enables the binding of each dimer to two p53 peptides derived from the c-terminal regulatory domain (residues 367-388) with micromolar affinity (Rustandi, et al. Biochemistry. 1998; 37: 1951-1960). Similarly, the N-terminal dimerization domain of HNF-1α(HNF-p1) was shown to associate with a dimer of DCoH (dimerization cofactor for HNF-1) via a dimer of HNF-p1 (Rose, et al. Nature Struct Biol. 2000; 7: 744-748). In alternative embodiments, these naturally occurring systems also may be utilized within the claimed methods and compositions to provide stable multimeric structures with multiple functions or binding specificities. Other binding events such as those between an enzyme and its substrate/inhibitor, for example, cutinase and phosphonates (Hodneland, et al. Proc Natl Acd Sci USA. 2002; 99: 5048-5052), may also be utilized to generate the two associating components (the “docking” step), which are subsequently stabilized covalently (the “lock” step).
Other AD sequences of potential use may be found in Patent Application Serial No. US20003/0232420A1, the entire text of which is incorporated herein by reference.
In exemplary embodiments, one component of a binary complex, A, is produced by linking a DDD sequence to the precursor of A, referred to as A, by recombinant engineering or chemical conjugation via a spacer group, resulting in a structure of A/DDD, hereafter referred to as a. As the DDD sequence in a effects the spontaneous formation of a dimer, A is thus composed of a2. The other component of a binary complex, B, is produced by linking an AD sequence to the precursor of B, referred to as B, by recombinant engineering or chemical conjugation via a spacer group, resulting in a structure of B/AD, hereafter referred to as b. The fact that the dimeric structure contained in a2 creates a docking site for binding to the AD sequence contained in b results in a ready association of a2 and b to form a binary complex composed of a2b. In various embodiments, this binding event is further stabilized with a subsequent reaction to covalently secure the two components of the assembly, for example via disulfide bridges, which occurs very efficiently as the initial binding interactions orient the reactive thiol groups to ligate site-specifically.
By placing cysteine residues at strategic locations in both the DDD and AD sequences (as shown for DDD2 and AD2), the binding interaction between a2 and b can be made covalent via disulfide bridges, thereby forming a stably tethered structure that renders in vivo applications more feasible. The stably tethered structure also retains the full functional properties of the two precursors A and B. The inventors are unaware of any prior art bispecific composition with this unique combination of features. The design disclosed above is modular in nature, as each of the two precursors selected can be linked to either DDD or AD and combined afterwards. The two precursors can also be the same (A=B) or different (A≠B). When A=B, the resulting a2b complex is composed of a stably tethered assembly of three subunits, referred to hereafter as a3. Materials that are amenable as precursors include proteins, peptides, peptide mimetics, polynucleotides, RNAi, oligosaccharides, natural or synthetic polymeric substances, nanoparticles, quantum dots, and organic or inorganic compounds. Other non-limiting examples of precursors of potential use are listed in Tables 6-10 below.
In addition to the use of disulfide linkages for preventing the dissociation of the constituent subunits, other methods for enhancing the overall stability of the stably tethered structure may be practiced. For example, various crosslinking agents or methods that are commercially available or used in research may be selected for such purposes. A potentially useful agent is glutaraldehyde, which has been widely used for probing the structures of non-covalently associated multimeric proteins by cross-linking the constituent subunits to form stable conjugates (Silva, et al. Food Technol Biotechnol. 2004; 42:51-56). Also of interest are two chemical methods involving oxidative crosslinking of protein subunits. One is a proximity labeling technique that employs either hexahistidine-tagged proteins (Fancy, et al. Chem. Biol. 1996; 3:551-559) or N-terminal glycine-glycine-histidine-tagged proteins (Brown, et al. Biochemistry. 1998; 37:4397-4406). These tags bind Ni(II) tightly and, when oxidized with a peracid, a Ni(III) species is produced that is capable of mediating a variety of oxidative reactions, including protein-protein crosslinking. Another technique, termed PICUP (photo-induced crosslinking of unmodified proteins) uses [Ru(II)(bipy)3]2+, ammonium persulfate, and visible light to induce protein-protein crosslinking (Fancy and Kodadek. Proc Natl Acad Sci USA. 1999; 96:6020-6024). However, as discussed below, numerous methods for chemically cross-linking peptide, polypeptide, protein or other macromolecular species are known in the art and any such known method may be used to covalently stabilize the binary a2b complex.
In more preferred embodiments, disclosed in more detail in Examples 23-35 below, hexameric complexes may be formed that are either monospecific or bispecific. Such complexes may be formed, for example, as disclosed in FIG. 10, FIG. 11, and FIG. 13 by attaching one AD2 to each of the C- or N-terminal ends of IgG moieties, which may then bind to DDD2-conjugated Fab fragments or other DDD2-conjugated antibodies or antibody fragments, to form a hexameric complex. As discussed in Examples 23-35, such monospecific or bispecific hexameric complexes show higher binding affinity and increased efficacy compared to the parent antibodies or fragments. Numerous monospecific or bispecific hexameric stably tethered structures are disclosed in Examples 23-35. However, the skilled artisan will realize that the examples are not limiting and a variety of antigen-binding or other functional moieties may be incorporated into the disclosed hexameric structures, discussed in part in Tables 6-10.
The skilled artisan will realize that where the above discussion refers to IgG or Fab fragments, other types of antibodies, antibody fragments, or non-antibody proteins as discussed in more detail below may be substituted. The stably tethered structures may comprise various combinations of antigen-binding components and/or effector components. For example, a bispecific antibody reacting with both activated platelet and tissue plasminogen activator (tPA) would not only prevent further clot formation by inhibiting platelet aggregation but also could dissolve existing clot by recruiting endogenous tPA to the platelet surface (Neblock et al., Bioconjugate Chem. 1991, 3:126-31). A stably tethered structure comprising a multivalent antibody binding component against an internalizing tumor associated antigen (such as CD74) linked to a toxin (such as a ribonuclease) would be valuable for selective delivery of the toxin to destroy the target tumor cell. A stably tethered structure comprising a soluble component of the receptor for IL-4R (sIL-4R) and a soluble component of the receptor for IL-13 (sIL-13R) would be a potential therapeutic agent for treating asthma or allergy. A hexameric, monospecific stably tethered structure composed of anti-GPIIb/IIIa Fab fragments should be more effective in preventing clot reformation than either the monovalent (ReoPro, Centocor) or bivalent analogs due to higher binding avidity. A stably tethered structure comprising multiple copies of a soluble component of TNFα-R should be more efficacious for arresting TNF than Enbrel (Amgen) in the treatment of rheumatoid arthritis and certain other autoimmune diseases (AID).
The claimed methods and compositions also include conjugates composed of one or more effectors or carriers linked to a stably tethered structure. The effectors or carriers may be linked to the stably tethered structure either non-covalently or covalently, for example by chemical cross-linking or by binding to a bispecific or multispecific stably tethered structure, with a first specificity for a disease-associated target and a second specificity for an effector and/or hapten linked to the effector(s), as discussed further below. Depending on the intended applications, the effector may be selected from a diagnostic agent, a therapeutic agent, a chemotherapeutic agent, a radioisotope, an imaging agent, an anti-angiogenic agent, a cytokine, a chemokine, a growth factor, a drug, a prodrug, an enzyme, a binding molecule, a ligand for a cell surface receptor, a chelator, an immunomodulator, an oligonucleotide, a hormone, a photodetectable label, a dye, a peptide, a toxin, a contrast agent, a paramagnetic label, an ultrasound label, a pro-apoptotic agent, a liposome, a nanoparticle or a combination thereof. Moreover, a conjugate may contain more than one effector, which can be the same or different, or more than one carrier, which can be the same or different. Effectors and carriers can also be present in the same conjugate. When the effector is a chelator, the resulting conjugate is usually further complexed with a metal, which can be either radioactive or non-radioactive. Conjugates containing carriers are also further incorporated with agents of diagnostic or therapeutic functions for the intended applications.
In certain embodiments, the effectors or carriers may be administered to a subject after a stably tethered structure, for example in pre-targeting strategies discussed below. The stably tethered structure may be first administered to the subject and allowed to localize in, for example, a diseased tissue such as a tumor. The effectors or carriers may be added subsequently and allowed to bind to the localized stably tethered structure. Where the effector or carrier is conjugated to a toxic moiety, such as a radionuclide, this pretargeting method reduces the systemic exposure of the subject to toxicity, allowing a proportionately greater delivery of toxic agent to the targeted tissue. Optionally, a clearing agent may be administered to clear non-localized stably tethered structures from circulation before administration of the targetable construct. These methods are known in the art and described in detail in U.S. Pat. No. 4,624,846, WO 92/19273, and Sharkey et al., Int. J. Cancer 51: 266 (1992). An exemplary targetable construct may have a structure of X-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-Lys(Y)-NH2, where the compound includes a hard acid cation chelator at X or Y, and a soft acid cation chelator at remaining X or Y; and wherein the compound further comprises at least one diagnostic or therapeutic cation, and/or one or more chelated or chemically bound therapeutic agents, diagnostic agents, or enzymes. The diagnostic agent could be, for example, Gd(III), Eu(III), Dy(III), Pr(III), Pa(IV), Mn(II), Cr(III), Co(III), Fe(III), Cu(II), Ni(II), Ti(III), V(IV) ions or a radical. A second exemplary construct may be of the formula X-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-Lys(Y)-NH2, where the compound includes a hard acid cation chelator or a soft acid chelator at X or Y, and nothing at the remaining X or Y; and wherein the compound further comprises at least one diagnostic or therapeutic cation, and/or one or more chelated or chemically bound therapeutic agents, diagnostic agents, or enzymes. In such embodiments, the A subunit may, for example, contain binding sites for tumor associated antigens while the B subunit may contain a binding site for an effector or carrier or a hapten conjugated to an effector or carrier.
The stably tethered structures of the present invention, including their conjugates, are suitable for use in a wide variety of therapeutic and diagnostic applications. For example, the hexavalent constructs based on antibody binding domains can be used for therapy where such a construct is not conjugated to an additional functional agent, in the same manner as therapy using a naked antibody. Alternatively, these stably tethered structures can be derivatized with one or more functional agents to enable diagnostic or therapeutic applications. The additional agent may be covalently linked to the stably tethered structures using conventional conjugation chemistries.
Methods of use of stably tethered structures may include detection, diagnosis and/or treatment of a disease or other medical condition. Such conditions may include, but are not limited to, cancer, cardiovascular disease, atherosclerosis, stroke, neurodegenerative disease, Alzheimer's disease, metabolic diseases, hyperplasia, diabetic retinopathy, macular degeneration, inflammatory bowel disease, Crohn's disease, ulcerative colitis, rheumatoid arthritis, sarcoidosis, asthma, edema, pulmonary hypertension, psoriasis, corneal graft rejection, neovascular glaucoma, Osler-Webber Syndrome, myocardial angiogenesis, plaque neovascularization, restenosis, neointima formation after vascular trauma, telangiectasia, hemophiliac joints, angiofibroma, fibrosis associated with chronic inflammation, lung fibrosis, amyloidosis, organ transplant rejection, deep venous thrombosis or wound granulation.
In particular embodiments, the disclosed methods and compositions may be of use to treat autoimmune disease, such as acute idiopathic thrombocytopenic purpura, chronic idiopathic thrombocytopenic purpura, dermatomyositis, Sydenham's chorea, myasthenia gravis, systemic lupus erythematosus, lupus nephritis, rheumatic fever, polyglandular syndromes, bullous pemphigoid, juvenile diabetes mellitus, Henoch-Schonlein purpura, post-streptococcalnephritis, erythema nodosum, Takayasu's arteritis, Addison's disease, rheumatoid arthritis, multiple sclerosis, sarcoidosis, ulcerative colitis, erythema multiforme, IgA nephropathy, polyarteritis nodosa, ankylosing spondylitis, Goodpasture's syndrome, thromboangitisubiterans, Sjogren's syndrome, primary biliary cirrhosis, Hashimoto's thyroiditis, thyrotoxicosis, scleroderma, chronic active hepatitis, polymyositis/dermatomyositis, polychondritis, pemphigus vulgaris, Wegener's granulomatosis, membranous nephropathy, amyotrophic lateral sclerosis, tabes dorsalis, giant cell arteritis/polymyalgia, pernicious anemia, rapidly progressive glomerulonephritis, psoriasis or fibrosing alveolitis.
Various embodiments may concern methods of treating inflammatory and immune-dysregulatory diseases, infectious diseases, pathologic angiogenesis or cancer. In this application the stably tethered structures bind to two different targets selected from the group consisting of (A) proinflammatory effectors of the innate immune system, (B) coagulation factors, (C) complement factors and complement regulatory proteins, and (D) targets specifically associated with an inflammatory or immune-dysregulatory disorder or with a pathologic angiogenesis or cancer, wherein the latter target is not (A), (B), or (C). At least one of the targets is (A), (B) or (C). Suitable combinations of targets are described in U.S. patent application Ser. No. 11/296,432, filed Dec. 8, 2005, entitled “Methods and Compositions for Immunotherapy and Detection of Inflammatory and Immune-Dysregulatory Disease, Infectious Disease, Pathologic Angiogenesis and Cancer,” the contents of which are incorporated herein by reference in their entirety. The proinflammatory effector of the innate immune system to which the binding molecules may bind may be a proinflammatory effector cytokine, a proinflammatory effector chemokine or a proinflammatory effector receptor. Suitable proinflammatory effector cytokines include MIF, HMGB-1 (high mobility group box protein 1), TNF-α, IL-1, IL-4, IL-5, IL-6, IL-8, IL-12, IL-15, and IL-18. Examples of proinflammatory effector chemokines include CCL19, CCL21, IL-8, MCP-1, RANTES, MIP-1A, MIP-1B, ENA-78, MCP-1, IP-10, GROB, and Eotaxin. Proinflammatory effector receptors include IL-4R (interleukin-4 receptor), IL-6R (interleukin-6 receptor), IL-13R (interleukin-13 receptor), IL-15R (interleukin-15 receptor) and IL-18R (interleukin-18 receptor).
The binding molecule also may react specifically with at least one coagulation factor, particularly tissue factor (TF) or thrombin. In other embodiments, the binding molecule reacts specifically with at least one complement factor or complement regulatory protein. In preferred embodiments, the complement factor is selected from the group consisting of C3, C5, C3a, C3b, and C5a. When the binding molecule reacts specifically with a complement regulatory protein, the complement regulatory protein preferably is selected from the group consisting of CD46, CD55, CD59 and mCRP.
In certain embodiments, the stably tethered structures may be of use for therapeutic treatment of cancer. It is anticipated that any type of tumor and any type of tumor antigen may be targeted. Exemplary types of tumors that may be targeted include acute lymphoblastic leukemia, acute myelogenous leukemia, biliary cancer, breast cancer, cervical cancer, chronic lymphocytic leukemia, chronic myelogenous leukemia, colorectal cancer, endometrial cancer, esophageal, gastric, head and neck cancer, Hodgkin's lymphoma, lung cancer, medullary thyroid cancer, non-Hodgkin's lymphoma, multiple myeloma, renal cancer, ovarian cancer, pancreatic cancer, glioma, melanoma, liver cancer, prostate cancer, and urinary bladder cancer.
Tumor-associated antigens that may be targeted include, but are not limited to, carbonic anhydrase IX, A3, antigen specific for A33 antibody, BrE3-antigen, CD1, CD1a, CD3, CD5, CD15, CD16, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD45, CD74, CD79a, CD80, HLA-DR, NCA95, NCA90, HCG and its subunits, CEA (CEACAM-5), CEACAM-6, CSAp, EGFR, EGP-1, EGP-2, Ep-CAM, Ba 733, HER2/neu, hypoxia inducible factor (HIF), KC4-antigen, KS-1-antigen, KS1-4, Le-Y, macrophage inhibition factor (MIF), MAGE, MUC1, MUC2, MUC3, MUC4, PAM-4-antigen, PSA, PSMA, RS5, S100, TAG-72, p53, tenascin, IL-6, IL-8, insulin growth factor-1 (IGF-1), Tn antigen, Thomson-Friedenreich antigens, tumor necrosis antigens, VEGF, placenta growth factor (P1GF), 17-1A-antigen, an angiogenesis marker (e.g., ED-B fibronectin), an oncogene marker, an oncogene product, and other tumor-associated antigens. Recent reports on tumor associated antigens include Mizukami et al., (2005, Nature Med. 11:992-97); Hatfield et al., (2005, Curr. Cancer Drug Targets 5:229-48); Vallbohmer et al. (2005, J. Clin. Oncol. 23:3536-44); and Ren et al. (2005, Ann. Surg. 242:55-63), each incorporated herein by reference. Particularly preferred embodiments may concern hexavalent, monospecific constructs with binding sites for CD20 or CD22. Other preferred embodiments may concern a hexavalent bispecific construct with binding sites for both CD20 and CD22.
Other embodiments may concern methods for treating a lymphoma, leukemia, or autoimmune disorder in a subject, by administering to the subject one or more dosages of a stably tethered structure, where the binding site of the second precursor bind to a lymphocyte antigen, and where the binding site of the first precursor binds to the same or a different lymphocyte antigen. The binding site or sites may bind a distinct epitope, or epitopes of an antigen selected from the group consisting of CD4, CD5, CD8, CD14, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD33, CD37, CD38, CD40, CD40L, CD46, CD52, CD54, CD74, CD80, CD126, CD138, CD154, B7, MUC1, Ia, Ii, HM1.24, HLA-DR, tenascin, VEGF, P1GF, ED-B fibronectin, an oncogene, an oncogene product, NCA 66a-d, necrosis antigens, IL-2, T101, TAG, IL-6, MIF, TRAIL-R1 (DR4) and TRAIL-R2 (DR5). The composition may be parenterally administered in a dosage of 20 to 1500 milligrams protein per dose, 20 to 500 milligrams protein per dose, 20 to 100 milligrams protein per dose, or 20 to 1500 milligrams protein per dose, for example.
In other embodiments, the stably tethered structures may be of use to treat infection with pathogenic organisms, such as bacteria, viruses or fungi. Exemplary fungi that may be treated include Microsporum, Trichophyton, Epidermophyton, Sporothrix schenckii, Cryptococcus neoformans, Coccidioides immitis, Histoplasma capsulatum, Blastomyces dermatitidis or Candida albicans. Exemplary viruses include human immunodeficiency virus (HIV), herpes virus, cytomegalovirus, rabies virus, influenza virus, human papilloma virus, hepatitis B virus, hepatitis C virus, Sendai virus, feline leukemia virus, Reo virus, polio virus, human serum parvo-like virus, simian virus 40, respiratory syncytial virus, mouse mammary tumor virus, Varicella-Zoster virus, Dengue virus, rubella virus, measles virus, adenovirus, human T-cell leukemia viruses, Epstein-Barr virus, murine leukemia virus, mumps virus, vesicular stomatitis virus, Sindbis virus, lymphocytic choriomeningitis virus or blue tongue virus. Exemplary bacteria include Bacillus anthracis, Streptococcus agalactiae, Legionella pneumophilia, Streptococcus pyogenes, Escherichia coli, Neisseria gonorrhoeae, Neisseria meningitidis, Pneumococcus spp., Hemophilis influenzae B, Treponema pallidum, Lyme disease spirochetes, Pseudomonas aeruginosa, Mycobacterium leprae, Brucella abortus, Mycobacterium tuberculosis or a Mycoplasma.
Although not limiting, in various embodiments, the precursors incorporated into the stably tethered structures may comprise one or more proteins, such as a bacterial toxin, a plant toxin, ricin, abrin, a ribonuclease (RNase), DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtherin toxin, Pseudomonas exotoxin, Pseudomonas endotoxin, Ranpirnase (Rap), Rap (N69Q), PE38, dgA, DT390, PLC, tPA, a cytokine, a growth factor, a soluble receptor component, surfactant protein D, IL-4, sIL-4R, sIL-13R, VEGF121, TPO, EPO (erythropoietin), a clot-dissolving agent, an enzyme, a fluorescent protein, sTNFα-R, an avimer, a scFv, a dsFv or a nanobody.
In other embodiments, an anti-angiogenic agent may form part or all of a precursor or may be attached to a stably tethered structure. Exemplary anti-angiogenic agents of use include angiostatin, baculostatin, canstatin, maspin, anti-VEGF antibodies or peptides, anti-placental growth factor antibodies or peptides, anti-Flk-1 antibodies, anti-Flt-1 antibodies or peptides, laminin peptides, fibronectin peptides, plasminogen activator inhibitors, tissue metalloproteinase inhibitors, interferons, interleukin 12, IP-10, Gro-β, thrombospondin, 2-methoxyoestradiol, proliferin-related protein, carboxiamidotriazole, CM101, Marimastat, pentosan polysulphate, angiopoietin 2, interferon-alpha, herbimycin A, PNU145156E, 16K prolactin fragment, Linomide, thalidomide, pentoxifylline, genistein, TNP-470, endostatin, paclitaxel, accutin, angiostatin, cidofovir, vincristine, bleomycin, AGM-1470, platelet factor 4 or minocycline.
In still other embodiments, one or more therapeutic agents, such as aplidin, azaribine, anastrozole, azacytidine, bleomycin, bortezomib, bryostatin-1, busulfan, calicheamycin, camptothecin, 10-hydroxycamptothecin, carmustine, celebrex, chlorambucil, cisplatin, irinotecan (CPT-11), SN-38, carboplatin, cladribine, cyclophosphamide, cytarabine, dacarbazine, docetaxel, dactinomycin, daunomycin glucuronide, daunorubicin, dexamethasone, diethylstilbestrol, doxorubicin, 2-pyrrolinodoxorubicine (2P-DOX), cyano-morpholino doxorubicin, doxorubicin glucuronide, epirubicin glucuronide, ethinyl estradiol, estramustine, etoposide, etoposide glucuronide, etoposide phosphate, floxuridine (FUdR), 3′,5′-O-dioleoyl-FudR (FUdR-dO), fludarabine, flutamide, fluorouracil, fluoxymesterone, gemcitabine, hydroxyprogesterone caproate, hydroxyurea, idarubicin, ifosfamide, L-asparaginase, leucovorin, lomustine, mechlorethamine, medroprogesterone acetate, megestrol acetate, melphalan, mercaptopurine, 6-mercaptopurine, methotrexate, mitoxantrone, mithramycin, mitomycin, mitotane, phenyl butyrate, prednisone, procarbazine, paclitaxel, pentostatin, PSI-341, semustine streptozocin, tamoxifen, taxanes, taxol, testosterone propionate, thalidomide, thioguanine, thiotepa, teniposide, topotecan, uracil mustard, velcade, vinblastine, vinorelbine, vincristine, ricin, abrin, ribonuclease, onconase, rapLR1, DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin, Pseudomonas exotoxin, Pseudomonas endotoxin, an antisense oligonucleotide, an interference RNA, or a combination thereof, may be conjugated to or incorporated into a stably tethered structure.
Various embodiments may concern stably tethered structures and methods of use of same that are of use to induce apoptosis of diseased cells. Further details may be found in U.S. Patent Application Publication No. 20050079184, the entire text of which is incorporated herein by reference. Such structures may comprise precursors with binding affinity for an antigen selected from the group consisting of CD2, CD3, CD8, CD10, CD21, CD23, CD24, CD25, CD30, CD33, CD37, CD38, CD40, CD48, CD52, CD55, CD59, CD70, CD74, CD80, CD86, CD138, CD147, HLA-DR, CEA, CSAp, CA-125, TAG-72, EFGR, HER2, HER3, HER4, IGF-1R, c-Met, PDGFR, MUC1, MUC2, MUC3, MUC4, TNFR1, TNFR2, NGFR, Fas (CD95), DR3, DR4, DR5, DR6, VEGF, P1GF, ED-B fibronectin, tenascin, PSMA, PSA, carbonic anhydrase IX, and IL-6. In more particular embodiments, a stably tethered structure of use to induce apoptosis may comprise monoclonal antibodies, Fab fragments, chimeric, humanized or human antibodies or fragments. In preferred embodiments, the stably tethered structure may comprise combinations of anti-CD74 X anti-CD20, anti-CD74 X anti-CD22, anti-CD22 X anti-CD20, anti-CD20 X anti-HLA-DR, anti-CD19 X anti-CD20, anti-CD20 X anti-CD80, anti-CD2 X anti-CD25, anti-CD8 X anti-CD25, anti-CD2 X anti-CD147, anti-CEACAM5 X anti-CD3, anti-CEACAM6 X anti-CD3, anti-EGFR X anti-CD3, anti-HER2/neu X anti-CD3, anti-CD20 X anti-CD3, anti-CD74 X anti-CD3 and anti-CCD22 X anti-CD3. In other preferred embodiments, the stably tethered structure may be a monospecific or multispecific anti-CD20, anti-CD22, anti-HLA-DR and/or anti-CD74. The skilled artisan will realize that a multivalent stably tethered structure may comprise multiple antigen-binding moieties that bind, for example, to different epitopes of the CD20 or CD22 antigens, or alternatively may comprise multiple copies of a single antigen-binding moiety that all bind to the same epitope. In more preferred embodiments, the chimeric, humanized or human antibodies or antibody fragments may be derived from the variable domains of LL2 (anti-CD22), LL1 (anti-CD74), L243 (anti-HLA-DR) and A20 (anti-CD20).
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows two exemplary DDD sequences. The underlined sequence in DDD1 (SEQ ID NO:1) corresponds to the first 44 amino-terminal residues found in the RIIα of human PKA. DDD2 (SEQ ID NO:2) differs from DDD1 in the two amino acid residues at the N-terminus.
FIG. 2 shows two exemplary AD sequences. The underlined sequence of AD1 (SEQ ID NO:3) corresponds to AKAP-is, which is an optimized RII-selective peptide reported with a Kd of 0.4 nM. Also shown is AD2 (SEQ ID NO:4).
FIG. 3 shows a schematic diagram of N-DDD2-Fab-hMN-14 (A), and the putative a2 structure formed by DDD2-mediated dimerization (B).
FIG. 4 shows the design of the N-DDD2-VH-hMN-14-pdHL2 plasmid expression vector.
FIG. 5 shows a schematic diagram of C-DDD2-Fab-hMN-14 (A), and the putative a2 structure formed by DDD2-mediated dimerization (B).
FIG. 6 shows the design of the C-DDD2-VH-hMN-14-pdHL2 plasmid expression vector.
FIG. 7 shows a schematic representation of (A) the noncovalent a2b complex that is formed upon mixing N-DDD2-Fab-hMN-14 and h679-Fab-AD2 under reducing conditions, and (B) the covalent TF1 structure formed by disulfide bridges.
FIG. 8 shows a schematic diagram of TF2.
FIG. 9 is a sketch of C-H-AD2-IgG. (A) Arrangement of cDNA/polypeptide sequences for heavy chain-AD2 and light chain. (B) Schematic representation of a C-H-AD2-IgG.
FIG. 10 is a schematic representation of a monospecific HIDS (hexavalent IgG-based DNL structure) resulting from the combination of C-H-AD2-IgG and Fab-DDD2 modules.
FIG. 11 is a schematic representation of a bispecific HIDS resulting from the combination of C-H-AD2-IgG and Fab-DDD2 modules.
FIG. 12 is a sketch of N-K-AD2-IgG. (A) Arrangement of cDNA/polypeptide sequences for heavy chain and AD2-light chain. (B) Schematic representation of a N-K-AD2-IgG.
FIG. 13 is a schematic representation of a bispecific HIDS resulting from the combination of N-K-AD2-IgG and Fab-DDD2 modules.
FIG. 14 shows sketches of (A) Fc-AD2-pdHL2 shuttle vector, (B) IgG-pdHL2 mammalian expression vector and (C) C-H-AD2-IgG-pdHL2 mammalian expression vector.
FIG. 15 shows SE-HPLC analysis of Protein A-purified C-H-AD2-hLL2-IgG. Peaks representing monomeric and dimeric forms are indicated.
FIG. 16 shows SDS-PAGE analysis of Protein A-purified C-H-AD2-hLL2-IgG under reducing and non-reducing conditions. Bands representing heavy chain-AD2, heavy chain and kappa light chain are indicated for reduced lanes. Bands representing C-H-AD2-hLL2-IgG and the covalent dimer are indicated for non-reduced lanes. The positions of molecular weight markers are indicated.
FIG. 17 shows SE-HPLC analysis of Protein A-purified N-K-AD2-hLL2-IgG. (A) Peaks representing monomeric, dimeric and trimeric forms are indicated with arrows. (B) Analysis following reduction with glutathione showing that the dimeric and trimeric forms are converted to the monomeric form.
FIG. 18 shows sketches of postulated structures for (A) dimeric and (B) trimeric forms of N-K-AD2-hLL2-IgG, which are converted to (C) the monomeric form by mild reduction.
FIG. 19 shows SE-HPLC analysis of Protein A-purified Hex-hA20.
FIG. 20 shows SDS-PAGE analysis of six C-H-AD2-hLL2-IgG-based HIDS. (A) SDS-PAGE under non-reducing conditions. (B) SDS-PAGE under reducing conditions. Bands representing heavy chain-AD2, Fd-DDD2 and kappa light chain are indicated by arrows. The positions of molecular weight markers are indicated.
FIG. 21 shows SE-HPLC analysis of Protein A-purified Hex-hLL2.
FIG. 22 shows SE-HPLC analysis of (A) DNL1 and (B) DNL1C.
FIG. 23 shows SE-HPLC analysis of DNL2.
FIG. 24 shows SDS-PAGE analysis of DNL3 and K-Hex-hA20 under reducing and non-reducing conditions. Bands representing heavy chain, AD2-kappa chain, Fd-DDD2 and kappa light chain are shown in the reduced lanes. Bands representing DNL3 and K-Hex-hA20 are shown in the non-reduced lanes. The positions of molecular weight markers are indicated.
FIG. 25 shows SE-HPLC analysis of DNL3.
FIG. 26 shows the results of two competitive ELISA experiments to compare the relative hA20/hLL2 binding avidities of DNL1, DNL2 Hex-hA20 and Hex-hLL2 with the parental IgGs. Microtitre plates were coated with hA20 or hLL2 IgG at 5 μg/ml. Dilution series of the HIDS were mixed with anti-Ids specific to hA20 or hLL2 IgG, which was maintained at a constant concentration (2 nM). The level of binding of the anti-Ids to the coated wells was detected using peroxidase-conjugated-Goat anti-Rat IgG and OPD substrate solution. The results are plotted as % inhibition (of anti-Id binding to coated wells) vs. concentration of HIDS. EC50 (the effective concentration resulting in 50% inhibition) values were derived using Prism software. The HIDS were used to compete for binding to (A) WI2 (hA20 Rat anti-Id) in hA20-coated wells or (B) WN (hLL2 Rat anti-Id) in hLL2-coated wells.
FIG. 27 shows the results of two competitive ELISA experiments to compare the relative hA20/hLL2 binding avidities of DNL2 and DNL3. Experiments were carried out as described for FIG. 26. DNL2, DNL3 and the parental IgGs were used to compete for binding to (A) WI2 (hA20 Rat anti-Id) in hA20-coated wells or (B) WN (hLL2 Rat anti-Id) in hLL2-coated wells.
FIG. 28 shows the result of cell counting assays following treatment of Daudi lymphoma cells with DNL1, DNL2, Hex-hA20 or rituximab. Tissue culture flasks were inoculated with 1×105 Daudi cells/ml in RPMI 1640 media supplemented with one of the HIDS or rituximab at varying concentrations. Viable cells were counted daily using a Guava PCA. (A) Comparison growth curves following treatments at 10 nM concentrations. (B) Comparison of growth curves at selected concentrations.
FIG. 29 shows the results of a dose-response experiment for treatment of Daudi cells with various HIDS. Cells were plated in 96-well plates at 5,000 cells/well in RPMI 1640 media. Five-fold serial dilutions were performed in triplicate from concentrations of 2×10−8 down to 6.4×10−12 M. The plates were incubated for four days, after which MTS reagent was added and the incubation was continued for an additional four hours before reading the plates at 490 nm. The results are given as percent of the OD490 for untreated wells vs. the log of the molar concentration of HIDS. EC40 (the effective concentration resulting in 40% growth inhibition) values were measured for each dose-response curve.
FIG. 30 shows the results of an in vivo therapy experiment where mice bearing human Burkitt Lymphoma (Daudi) were treated with DNL2 or Hex-hA20. Mice (4/group) were inoculated i.v. with 1.5×107 Daudi cells (day 0). On days 1, 4 and 7, mice were administered either 4 pg or 20 μg of DNL2 or Hex-hA20 intraperitoneally (i.p.). Mice were sacrificed if they developed either hind-limb paralysis or lost >20% body weight. The results are plotted as % survival vs. time (days). Median survival and long term survivors are shown.
FIG. 31 shows the relative dose-response curves generated using an MTS proliferation assay for Daudi cells, Raji cells and Ramos cells treated with a bispecific HID (DNL2—four hLL2 Fab fragments tethered to an hA20 IgG) and a monospecific HID (Hex-hA20), compared with an hA20 IgG control. In Daudi cells (top panel), DNL2 showed >100-fold and Hex-hA20 showed >10,000 fold more potent antiproliferative activity than hA20 IgG. In Raji cells (middle panel), Hex-hA20 displayed potent anti-proliferative activity, while DNL2 showed only minimal activity, compared to hA20 IgG. In Ramos cells (bottom panel), both DNLs and Hex-hA20 displayed potent anti-proliferative activity compared to hA20 IgG.
FIG. 32 shows the effects of cross-linking on the anti-proliferative activity of hA20 IgG, DNL2 and Hex-hA20. As shown in the Figure, cross-linking potentiated the anti-proliferative activity of hA20 IgG, but resulted in no enhancement of the activities of DNL2 or Hex-hA20.
FIG. 33 shows the stability of DNL1 and DNL2 in human serum, as determined using a bispecific ELISA assay. The protein structures were incubated at 10 μg/ml in fresh pooled human sera at 37° C. and 5% CO2 for five days. For day 0 samples, aliquots were frozen in liquid nitrogen immediately after dilution in serum. ELISA plates were coated with an anti-Id to hA20 IgG and bispecific binding was detected with an anti-Id to hLL2 IgG. Both DNL1 and DNL2 were highly stable in serum and maintained complete bispecific binding activity.
FIG. 34 illustrates the complement-dependent cytotoxicity (CDC) or lack thereof by DNL1, DNL2, Hex-hA20, hLL2, hA20-IgG and hA20-IgG-AD2. Surprisingly, although hA20 IgG and hA20-IgG-AD2 exhibited potent CDC activity on Daudi cells in an in vitro assay, none of the hexavalent DNL structures exhibited CDC activity in this assay. Both DNL2 and Hex-ha20 comprise hA20-IgG-AD2, which showed CDC activity similar to hA20 IgG.
FIG. 35 shows the antibody-dependent cellular cytotoxicity (ADCC) of DNL1, compared with hA20 IgG, Rituximab and hLL2 IgG, assayed with freshly isolated peripheral blood mononuclear cells. Both rituximab and hA20 IgG had potent ADCC activity, while DNL1 did not exhibit any detectable ADCC.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
All documents, or portions of documents, cited in this application, including but not limited to patents, patent applications, articles, books, and treatises, are hereby expressly incorporated by reference in their entirety.
In certain embodiments, novel stably tethered structures in the format of a2b and methods for making these complexes are provided. In general, the binary complexes are made up of a noncovalently linked homodimer structure, referred to as A or a2, with which a second structure, referred to as B or b, associates site-specifically. The resulting a2b structure may be stabilized by non-covalent, or preferably by covalent interaction (e.g., disulfide bonds) between A and B. A is formed from two identical subunits, where each subunit is composed of a precursor linked to a peptide sequence, referred to as the dimerization and docking domain (DDD), which in preferred embodiments is derived from a cAMP-dependent protein kinase (PKA). The DDD domain contained in the subunit associates spontaneously to form a stable homodimer, and this association in turn produces a high affinity binding site for a peptide sequence, referred to as the anchoring domain (AD), which is found, for example, in various A-kinase anchor proteins (AKAPs), and is contained in B. Thus, B is composed of a precursor linked to an AD.
Assembly of the binary complex occurs readily via interaction of the AD peptide with the (DDD)2 binding site. The DDD peptide may be inserted into essentially any polypeptide sequence or tethered to any precursor, provided that such derivatization does not interfere with its ability to dimerize, as well as to bind to the AD peptide. Likewise, the AD peptide may be inserted into essentially any polypeptide sequence or tethered to any precursor provided that such derivatization does not interfere with its binding to the homodimer DDD binding site. This modular approach is highly versatile and can be used to combine essentially any A with any B to form a binary assembly that contains two subunits (a2) derived from the precursor of A and one subunit (b) derived from the precursor of B. Where both precursors of A and B contain an antibody domain that can associate with a second antibody domain to produce an antigen binding site (for example, a Fab or scFv), the resulting a2b complex is bispecific and trivalent. In some embodiments, the binary complex may be linked, for example via chemical conjugation, to effectors, such as ligands or drugs, to carriers, such as dextran or nanoparticles, or to both effectors and carriers, to allow additional applications enabled by such modifications. In preferred embodiments, variations on this theme may be used to prepare hexameric complexes that are either homohexamers or heterohexamers.
As the stability of the binary complex depends primarily on the binding affinity of the DDD contained in A for the AD contained in B, which is estimated by equilibrium size-exclusion HPLC analysis to be no stronger than 8 nM for two prototype a2b structures (described in Example 5) formed between a C-terminally fused AD1 construct (h679-Fab-AD1, described in Example 3) to a C- or N-terminally fused DDD1 construct (C-DDD1-Fab-hMN-14 or N-DDD1-Fab-hMN-14, both described in Example 4), covalently linking A and B contained in the a2b complex would prevent undesirable dissociation of the individual subunits, thereby facilitating in vivo applications. To stabilize the binary complex, cysteine residues may be introduced onto both the DDD and AD sequences at strategic positions to enable the formation of disulfide linkages between the DDD and AD. Other methods or strategies may be applied to effect the formation of a stabilized complex via crosslinking a2 and b. For example, the constituent subunits can be covalently linked to each other in a less specific way with lower efficiency using glutaraldehyde or the PICUP method. Other known methods of covalent cross-linking may also be used.
As used herein, “a” or “an” may mean one or more than one of an item.
As used herein, the terms “and” and “or” may be used to mean either the conjunctive or disjunctive. That is, both terms should be understood as equivalent to “and/or” unless otherwise stated.
A “dimerization and docking domain (DDD)” refers to a peptide sequence that allows the spontaneous dimer formation of two homomonomers containing the DDD sequence. The resulting homodimer contains a docking site within the DDD sequence for an anchoring domain. Although exemplary DDD sequences may be obtained from cAMP-dependent protein kinase, other known DDD sequences may be utilized.
An “anchoring domain (AD)” is a peptide sequence that has binding affinity for a dimerized DDD sequence. Although exemplary AD sequences may be derived from any of the A-kinase anchor proteins (AKAPs), other known AD sequences may be utilized.
The term “precursor” is used according to its plain and ordinary meaning of a substance from which a more stable, definitive or end product is formed.
A “binding molecule,” “binding moiety” or “targeting molecule,” as used herein, is any molecule that can specifically bind to a target molecule, cell, complex and/or tissue. A binding molecule may include, but is not limited to, an antibody or a fragment, analog or mimic thereof, an avimer, an aptamer or a targeting peptide.
An “antibody,” as described herein, refers to a full-length (i.e., naturally occurring or formed by normal immunoglobulin gene fragment recombinatorial processes) immunoglobulin molecule (e.g., an IgG antibody) or an immunologically active (i.e., specifically binding) portion or analog of an immunoglobulin molecule, like an antibody fragment.